Patent Publication Number: US-11039724-B2

Title: Vacuum cleaner

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a continuation of U.S. application Ser. No. 15/445,214, filed on Feb. 28, 2017 which claims priority under 35 U.S.C. § 119 to Korean Patent Application No. 10-2016-0024022, filed in Korea on Feb. 29, 2016, Korean Patent Application No. 10-2016-0062452, filed in Korea on May 20, 2016, Korean Patent Application No. 10-2016-0108676, filed in Korea on Aug. 25, 2016, Korean Patent Application No. 10-2016-0184117, filed in Korea on Dec. 30, 2016, and Korean Patent Application No. 10-2017-0001590, filed in Korea on Jan. 4, 2017, whose entire disclosure is hereby incorporated by reference. 
    
    
     BACKGROUND 
     1. Field 
     A vacuum cleaner is disclosed herein. 
     2. Background 
     Generally, a vacuum cleaner is an apparatus which suctions dust and foreign substances on a surface to be cleaned using a suction motor provided inside a main body and then filters the dust and the foreign substances at an inside of the main body. 
     The above-described vacuum cleaner may be classified into an up-right type vacuum cleaner in which a suction nozzle is connected to a main body to be moved along with the main body, and a canister type vacuum cleaner in which the suction nozzle is connected to the main body by a connection pipe, a handle, a hose and the like. 
     In Korean Patent Publication No. 10-2012-0004100 (published on Jan. 12, 2012) as a prior art document, there is disclosed a canister type vacuum cleaner. 
     SUMMARY 
     The present disclosure provides a vacuum cleaner capable of traveling while avoiding an obstacle detected when the cleaner travels to improve user convenience, and a method of controlling the same. 
     The present disclosure provides a vacuum cleaner capable of detecting an obstacle when the cleaner travels and preventing malfunction caused due to a suction hose to improving operation reliability, and a method of controlling the same. 
     The present disclosure provides a vacuum cleaner capable of preventing an obstacle from being erroneously detected when a cleaner body rotates, and a method of controlling the same. 
     The present disclosure provides a vacuum cleaner capable of avoiding an obstacle located at a front side, traveling along a wall and escaping from the wall, and a method of controlling the same. 
     A vacuum cleaner according to one aspect includes a cleaner body, a suction hose mounted at a front surface of the cleaner body to suck in dust, moving wheels provided at both sides of the cleaner body, rotating to move the cleaner body and rotatably supporting the cleaner body, wheel motors connected to the moving wheels and rotating the moving wheels, a detecting unit provided in the cleaner body and sensing inclination of the cleaner body to determine whether the cleaner moves and stops, a plurality of detecting members provided at a front surface of the cleaner body and located at both sides of the suction hose to detect an obstacle, and a controller configured to control the wheel motors according to detected signals of the detecting unit and the plurality of obstacle detecting members. 
     A method of controlling a vacuum cleaner includes moving wheels rotating at both sides of a cleaner body, wheel motors for driving the moving wheels, a suction hose located at the center of a front surface of the cleaner body, a plurality of obstacle detecting members provided at both sides of the suction hose and a controller configured to control driving of the wheel motors, wherein the controller controls operation of the wheel motors such that the cleaner body travels while avoiding an obstacle, upon receiving an obstacle detecting signal from the plurality of obstacle detecting members. 
     The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments will be described in detail with reference to the following drawings in which like reference numerals refer to like elements, and wherein: 
         FIG. 1  is a perspective view of a vacuum cleaner according to an embodiment of the present invention; 
         FIG. 2  is a view illustrating a state in which a cleaner body and a suction unit are separated; 
         FIG. 3  is a view illustrating a state in which a dust container is separated from the cleaner body; 
         FIG. 4  is a view illustrating a state in which a cover member of the cleaner body is opened; 
         FIG. 5  is an exploded perspective view of the cleaner body; 
         FIG. 6  is an exploded perspective view illustrating a state in which a prefilter assembly is opened; 
         FIG. 7  is a cross-sectional view of the cleaner body; 
         FIG. 8  is a plan view of the cleaner body from which the cover member is removed; 
         FIG. 9  is an exploded perspective view illustrating a coupling structure of the cleaner body, a moving wheel and a detecting part when being seen in one direction; 
         FIG. 10  is an exploded perspective view illustrating the coupling structure of the cleaner body, the moving wheel and the detecting part when being seen in another direction; 
         FIG. 11  is a side view illustrating an installing state between the cleaner body and a wheel gear assembly; 
         FIG. 12  is a side view of the cleaner body; 
         FIG. 13  is a bottom view of the cleaner body; 
         FIG. 14  is an exploded perspective view illustrating a coupling structure of a rear wheel unit according to the embodiment of the present invention; 
         FIG. 15  is a cross-sectional view illustrating an operating state of the rear wheel unit; 
         FIG. 16  is a rear view illustrating a state in which a rear cover of the cleaner body is opened; 
         FIG. 17  is an exploded perspective view illustrating a coupling structure of a battery and a filter according to the embodiment of the present invention; 
         FIG. 18  is a cross-sectional view of the cleaner body before the battery is installed; 
         FIG. 19  is a cross-sectional view of the cleaner body in a state in which the battery is installed; 
         FIG. 20  is a perspective view of the cover member; 
         FIG. 21  is an exploded perspective view of the cover member; 
         FIG. 22  is a partial cross-sectional view illustrating a coupling structure of the cover member and an obstacle detecting member; 
         FIG. 23  is an exploded perspective view illustrating a coupling structure of a locking assembly according to the embodiment of the present invention; 
         FIG. 24  is a perspective view illustrating a state before the locking assembly is operated; 
         FIG. 25  is a cross-sectional view illustrating the state before the locking assembly is operated; 
         FIG. 26  is a perspective view illustrating an operating state of the locking assembly; 
         FIG. 27  is a cross-sectional view illustrating the operating state of the locking assembly; 
         FIG. 28  is a plan view of the cover member in which a display according to the embodiment is in an OFF state; 
         FIG. 29  is a plan view of the cover member in which the display according to the embodiment is in an ON state; 
         FIG. 30  is a perspective view illustrating a state in which the cover member is opened; 
         FIG. 31  is an exploded perspective view illustrating a coupling structure of a link assembly according to the embodiment of the present invention; 
         FIG. 32  is a cross-sectional view illustrating a state of the link assembly while the cover member is closed; 
         FIG. 33  is a cross-sectional view illustrating the state of the link assembly while the cover member is opened; 
         FIG. 34  is an enlarged view of an A portion in  FIG. 30 ; 
         FIG. 35  is a partial perspective view illustrating a structure of a cover member coupling portion and an arrangement of a display cable according to the embodiment of the present invention; 
         FIG. 36  is a view illustrating a cable arrangement state in a cover base of the cover member; 
         FIG. 37  is a view illustrating a coupling structure of the wire to the cleaner body; 
         FIG. 38  is a perspective view of the dust container; 
         FIG. 39  is an exploded perspective view of the dust container; 
         FIG. 40  is an exploded perspective view illustrating a coupling structure of an upper cover and a lower cover of the dust container when being seen from one side; 
         FIG. 41  is a cross-sectional view illustrating a state in which the upper cover is opened; 
         FIG. 42  is an exploded perspective view illustrating the coupling structure of the upper cover and the lower cover of the dust container when being seen from another side; 
         FIG. 43  is a cross-sectional view illustrating a state in which the lower cover is opened; 
         FIG. 44  is an exploded perspective view illustrating a coupling structure of the lower cover and a dust compressing unit; 
         FIG. 45  is an enlarged view of a B portion in  FIG. 41 ; 
         FIG. 46  is a cross-sectional view illustrating a flow of air and dust in the cleaner body; 
         FIG. 47  is a plan view illustrating the flow of the air and dust in the cleaner body; 
         FIG. 48  is a view illustrating a stopping state of the cleaner body; 
         FIG. 49  is a view illustrating a travelling state of the cleaner body; 
         FIG. 50  is a view illustrating an obstacle avoidance travelling state of the cleaner body; 
         FIG. 51  is a view illustrating a detection range of the obstacle detecting member; 
       and 
         FIG. 52  is a view illustrating a wall surface travelling state of the cleaner body. 
         FIG. 53  is a view illustrating a state in which a body part of the cleaner body according to another embodiment of the present invention is inclined forward; 
         FIG. 54  is a view illustrating a state in which the body part is inclined backward; 
         FIG. 55  is a view illustrating a configuration of a support part according to another embodiment of the present invention; 
         FIG. 56  is a view sequentially illustrating a process in which a battery is coupled to the cleaner body; 
         FIG. 57  is a view sequentially illustrating a process in which a battery is separated from the cleaner body; 
         FIG. 58  is a diagram showing the concept illustrating a reference distance for controlling following movement of a vacuum cleaner according to another embodiment of the present invention. 
         FIG. 59  is a diagram showing the concept illustrating a sensor attached to each of a handle and a main body of a vacuum cleaner to sense a distance between the handle and the main body according to the present invention. 
         FIG. 60  is a flowchart illustrating a method of controlling a vacuum cleaner according to the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. However, the invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein; rather, alternative embodiments included in other retrogressive inventions or falling within the spirit and scope of the present disclosure can easily be derived through adding, altering, and removing, and will fully convey the concept of the invention to those skilled in the art. 
       FIG. 1  is a perspective view of a vacuum cleaner according to an embodiment of the present invention. And  FIG. 2  is a view illustrating a state in which a cleaner body  10  and a suction unit are separated. 
     As illustrated in the drawings, a vacuum cleaner  1  according to an embodiment of the present invention includes a cleaner body  10  and a suction unit  20 . 
     A motor for generating a suction force is provided inside the cleaner body  10 . And when the motor is driven and the suction force is generated, the suction unit  20  may guide air containing dust into the cleaner body  10 . 
     The suction unit  20  may include a suction part  21  for suctioning the dust on a surface to be cleaned, e.g., a floor surface and a connection part for connecting the suction part  21  with the cleaner body  10 . The connection part may include an extension pipe  22  which is connected to the suction part  21 , a handle  23  which is connected to the extension pipe  22  and a suction hose  24  which connects the handle  23  with the cleaner body  10 . 
     A fitting portion  241  which enhances airtightness when being coupled with a connector  401  of the cleaner body  10  may be provided at the suction hose  24 . 
     The fitting portion  241  may serve to install or separate the suction hose  24  at/from the connector  401 . The fitting portion  241  may be formed in multi-stages as illustrated in the drawings. 
     The cleaner body  10  includes a body part  30  and a cover member  40  which form an entire exterior. 
     The cleaner body  10  may further include a moving wheel  60  which is rotatably coupled to the body part  30 . A pair of moving wheels  60  may be provided and may be coupled to both sides of the body part  30 , respectively. And the moving wheel  60  supports the body part  30  to be rotatable about a rotating center of the moving wheel  60 . 
     A grip portion  41  which is gripped by a user may be provided at the cover member  40 . The user may grip the grip portion  41  when lifting or tilting the body part  30 , or opening and closing the cover member  40 . 
     A rear cover  314  which is openable and closable may be provided at a rear surface of the body part  30 . The rear cover  314  may be formed to open and close a space inside the body part  30  in which a battery unit  38  and a filter unit  39  are accommodated. 
     The cleaner body  10  further includes a dust container  50  in which the dust suctioned through the suction unit  20  is stored. The dust container  50  may be formed in a cylindrical shape as illustrated in the drawings, but is not limited thereto. And the dust container  50  may be separably provided at a front surface of the body part  30 . 
     And  FIG. 3  is a view illustrating a state in which the dust container is separated from the cleaner body  10 . And  FIG. 4  is a view illustrating a state in which the cover member of the cleaner body  10  is opened. 
     As illustrated in the drawings, the dust container  50  may be separably installed at a seating part  32  formed at a first half portion of the body part  30 . The dust container  50  may form a part of the front surface of the body part  30  while being installed at the seating part  32 . And the dust container  50  may be installed or separated by opening and closing of the cover member  40 . 
     A suction port  511  through which the dust is suctioned may be provided at the dust container  50 . The suction port  511  may be disposed at an upper surface portion of the dust container  50 . Accordingly, the air introduced through the suction port  511  is guided downward and then moved to a dust collecting space inside the dust container  50 . 
     The dust container  50  may be separably installed at the body part  30 . The dust collecting space in which the dust introduced through the suction port  511  is collected may be formed inside the dust container  50 . 
     The dust container  50  may be provided at a front of the body part  30 , and at least a part of a side surface portion of the dust container  50  may be formed of a transparent material to allow the user to check the dust collected in the dust collecting space. 
     While the dust container  50  is seated on the seating part  32 , the side surface portion may be exposed through the front surface of the body part  30 . At this point, an exposed portion of the dust container  50  is formed from a transparent upper end of the side surface portion of the dust container  50  to a lower end thereof, and thus the entire dust collecting space may be checked without separating the dust container  50 . 
     A dust separation structure which separates the dust from the air suctioned through the suction unit  20  may be provided inside the dust container  50 , and the dust separated by the dust separation structure may be collected in a lower portion of the dust container  50 . 
     The connector  401  is directly connected to the suction hose  24 , and the air containing the dust may be introduced therethrough. That is, one side of the connector  401  is coupled to the suction hose  24 , and the other side thereof is coupled to the suction port  511 . Therefore, the connector  401  connects the suction hose  24  with the suction port  511 . 
     The connector  401  may be in communication with the dust container  50 . Accordingly, the air introduced into the suction hose  24  may be introduced into the dust container  50  via the connector  401 . 
     The suction port  511  through which the dust is introduced may be provided at one side of the dust container  50 . As illustrated in the drawings, the suction port  511  may be provided at an upper portion of the dust container  50 . And the suction port  511  may be formed to be directed forward. Here, the term “forward” may be a portion, at which the suction hose  24  is located, based on the cleaner body  10 . 
     As illustrated in the drawings, the connector  401  may be disposed at the upper portion of the dust container  50 . Since both of the suction port  511  and the connector  401  are disposed at the upper portion of the dust container  50 , a passage length of the air introduced from the suction hose  24  may be minimized. 
     The cleaner body  10  further includes the cover member  40  which is movably provided at the body part  30 . The cover member  40  may form at least a part of an upper surface of the cleaner body  10  and may be formed to open and close an upper surface of the body part  30 . At this point, a rear end of the cover member  40  may be shaft-coupled to the body part  30  to be rotatable, and thus the user may open the cover member  40  by gripping and rotating the grip portion  41 . 
     The connector  401  may be provided at the cover member  40 . Therefore, the connector  401  may be moved along with the cover member  40 . The cover member  40  may shield at least one side of the dust container  50 . The cover member  40  may shield at least one side of the dust container  50  and may also be coupled to the dust container  50 . The cover member  40  may be coupled to the dust container  50  when being closed and may be separated from the dust container  50  when being opened. For example, the cover member  40  may be coupled to the upper portion of the dust container  50 . 
     While the cover member  40  is in a closed state, the fitting portion  241  of the suction hose  24  connected to the connector  401  of the cover member  40  may be in communication with the suction port  511  of the dust container  50 . Therefore, the dust and the air suctioned through the suction unit  20  may pass through the connector  401  of the cover member  40  and then may be introduced into the dust container  50  through the suction port  511 . 
     And while the cover member  40  is in an opened state, the fitting portion  241  of the suction hose  24  may be maintained in a connected state to the connector  401  of the cover member  40 , and the cover member  40  and the dust container  50  may be separated. Therefore, while the cover member  40  is in the opened state, the dust container  50  may be separable from the seating part  32 . 
     Hereinafter, the cleaner body  10  will be more specifically described. 
       FIG. 5  is an exploded perspective view of the cleaner body  10 .  FIG. 6  is an exploded perspective view illustrating a state in which a prefilter assembly is opened. And  FIG. 7  is a cross-sectional view of the cleaner body  10 . And  FIG. 8  is a plan view of the cleaner body  10  from which the cover member is removed. 
     As illustrated in the drawings, the cleaner body  10  includes the body part  30  and the cover member  40  and may be formed so that the dust container  50  is installed at the body part  30 . 
     And the body part  30  may include a base  31  which forms a bottom of the cleaner body  10  and provides a space in which the dust container  50 , the battery unit  38 , the filter unit  39  and a main motor  35  are installed. 
     The base  31  may include a first half portion  312 , a center portion  311  and a second half portion  313 , may be formed to have a predetermined width and thus may provide the space in which the dust container  50 , the battery unit  38 , the filter unit  39  and so on are installed. 
     The center portion  311  may be formed in a flat surface shape and may be disposed between the first half portion  312  and the second half portion  313 . At this point, the first half portion  312  and the second half portion  313  may be formed to extend slantly based on the center portion  311  and may be formed to be gradually higher in a direction which becomes distant from an end of the center portion  311 . 
     A terminal installing portion  311   a  at which a power supply terminal  307  is disposed may be formed at one end of the center portion  311 , i.e., a position adjacent to the moving wheel  60 . The terminal installing portion  311   a  may be formed to be recessed, such that a lower surface thereof is opened, and may also be formed to be connected to a terminal of a charging device when the battery unit  38  of the vacuum cleaner  1  is charged. 
     And a rear wheel unit  70  may be provided at a position of the center portion  311  adjacent to the second half portion  313 . The rear wheel unit  70  may prevent the cleaner body  10  from being overturned backward while the vacuum cleaner  1  is being used. The rear wheel unit  70  may allow the base  31  to be maintained at a set angle while being in a stopped state. To this end, the rear wheel unit  70  may be formed to be in contact with the ground and the center portion  311  while the cleaner body  10  is in the stopped state which is not travelled, thereby elastically supporting the cleaner body  10 . 
     The first half portion  312  is formed at a front end of the center portion  311 . The first half portion  312  extends from an end of the center portion  311  so as to be inclined upward, and the seating part  32  which forms the space for accommodating the dust container  50  may be provided at the first half portion  312 . 
     The seating part  32  may include a lower surface portion  321  which forms a bottom thereof and a circumferential portion  322  which extends upward along a circumference of the lower surface portion  321 . The circumferential portion  322  is formed to be opened forward, such that the dust container  50  is installed therein. 
     A compression motor assembly  323  for driving a dust compressing unit  56  inside the dust container  50  may be provided between the lower surface portion  321  and the first half portion  312 . When the dust container  50  is installed at the seating part  32 , the compression motor assembly  323  and the dust compressing unit  56  which will be described below in detail are connected to each other, and thus the dust compressing unit  56  is in a drivable state. 
     The compression motor assembly  323  may include a compression motor  323   a  which provides a rotating force and a compression gear  323   b  which is connected to a rotating shaft of the compression motor  323   a . The compression gear  323   b  may be located at a position which is eccentric to one side from a center of the lower surface portion  321 . And an opened lower surface hole  321   a  may be formed at the lower surface portion  321 , and a first transmission gear  591  which will be described below may be located at the lower surface hole  321   a  when the dust container  50  is seated. Therefore, when the dust container  50  is installed, the compression gear  323   b  is coupled to the first transmission gear  591  so as to transmit power of the compression motor  323   a.    
     A front wheel  312   a  may be installed at a lower surface of the first half portion  312 . The front wheel  312   a  is located at a front side slightly further than a center of the first half portion  312  and allows the cleaner body  10  to be easily moved over an obstacle when the obstacle such as a carpet and a door sill is located in front of the cleaner body  10  which is being moved. And when the cleaner body  10  is tilted forward, the front wheel  312   a  may be rotated in a contacting state with the ground so that the cleaner body  10  is prevented from being overturned forward. 
     The second half portion  313  may also be formed to be inclined upward from a rear end of the center portion  311 . Therefore, when the cleaner body  10  starts to move forward to travel, the vacuum cleaner  1  is inclined using the moving wheel  60  as an axis, and thus the cleaner body  10  is easily rotated. 
     And at least a part of a rear opening  317  opened and closed by the rear cover  314  may be formed at the second half portion  313 . The rear cover  314  forms the same curved surface as that of each of a lower decoration  315  and an upper decoration  37  which form an exterior of each of the second half portion  313  and the cleaner body  10  while shielding the rear opening  317 . The rear cover  314  may be formed as a part of the second half portion  313  to have the same slope or curved surface as that of the second half portion  313 . 
     The rear cover  314  may form a part of the rear surface of the body part  30 . And a lower end of the rear cover  314  may be rotatably coupled to the second half portion  313  and may open and close the rear opening  317  by rotation. And a grille through which the air separated from the dust while passing through the inside the cleaner body  10  is discharged may be formed at the rear cover  314 , and thus the air from which the dust is filtered may be discharged. 
     Meanwhile, a base frame is installed at a center of the base  31 . The base frame is formed to divide a space in which the dust container  50  is disposed, a space in which the main motor  35  is provided and a space in which the battery unit  38  and the filter unit  39  are provided. 
     Specifically, the base frame may include a lower frame  33  and an upper frame  34 . 
     The lower frame  33  is installed at the center portion  311  and may include a first barrier  331  which divides forward and backward a part of an internal space of the body part  30  and one pair of side walls  332  which extend from both ends of the first barrier  331 , respectively. And the main motor  35 , a wheel motor assembly  63 , the compression motor assembly  323 , an obstacle detecting member  44  and a main PCB  301  for controlling a general driving of the vacuum cleaner  1  may be provided at a front surface of the first barrier  331 . 
     A lower seating member  300  may be provided at the front surface of the first barrier  331 . The lower seating member  300  may be formed so that a center thereof is recessed to support a side surface of the dust container  50  when the dust container  50  is installed. And the main PCB  301  installed at the front surface of the first barrier  331  may be accommodated inside the lower seating member  300 . 
     A noise filter  302  for removing noise of input power supplied to the main PCB  301  is provided at a rear surface of the first barrier  331 . The noise filter  302  may be an EMI filter. 
     At this point, a first barrier hole  331   a  serving as a passage of the air is formed at the first barrier  331  between the main PCB  301  and the noise filter  302 . Therefore, the main PCB  301  and the noise filter  302  may be naturally cooled by the air passing through the first barrier hole  331   a.    
     The lower frame  33  is opened upward and downward while being installed at the base  31 , and the upper frame  34  is installed at an upper end of the lower frame  33 . And the upper frame  34  shields an opened upper surface of the lower frame  33  and forms the space in which the battery unit  38  and the filter unit  39  are accommodated. And the space in which the main motor  35  for suctioning the air is provided is also formed. 
     Specifically, the upper frame  34  may include a cover plate  341 , a second barrier  342  and a second side wall  343 . 
     The second barrier  342  divides an upper space of the body part  30  into a front portion and a rear portion, forms at a front thereof a space in which a prefilter assembly  36  connected to the dust container  50  is provided and also forms at a rear thereof a space in which the main motor  35  is provided. 
     And a second barrier hole  342   a  may be formed at the second barrier  342 , and thus fine dust may be filtered while the air passed through the dust container  50  passes through the prefilter assembly  36  when the main motor  35  is driven, and the air filtered while passing through the prefilter assembly  36  passes through the main motor  35 . 
     A front barrier wall  344  which extends forward is formed at both ends of the second barrier  342  and forms a space in which the prefilter assembly  36  is accommodated. 
     The prefilter assembly  36  may include a prefilter case  361  which is in close contact with the dust container  50  and a prefilter body  362  which is coupled with the prefilter case  361  and in which a filter member  363  is accommodated. 
     The prefilter case  361  and the prefilter body  362  may form a space therein to accommodate the filter member  363  while being coupled to each other and may also be rotatably coupled to each other to be opened and closed. Therefore, the filter member  363  may be installed at or separated from the prefilter body  362  after the prefilter case  361  is opened. 
     The filter member  363  serves to secondarily filter the fine dust which is not filtered by the dust container  50  in which the dust and foreign substances are primarily filtered and is formed to remove the fine dust in the air introduced into the main motor  35 . Meanwhile, the air passed through the filter member  363  and the main motor  35  may cool the battery unit  38  and then may be discharged to an outside after the fine dust therein is tertiarily filtered in the filter unit  39  which will be described in detail. 
     The prefilter assembly  36  will be described in more detail with reference to  FIG. 6 . The prefilter assembly  36  has a structure in which the filter member  363  is accommodated in the prefilter body  362  and which is shielded by the prefilter case  361 . 
     The prefilter case  361  may be exposed forward while the prefilter assembly  36  is installed at the upper frame  34 . And a front surface of the prefilter case  361  is formed to have a curved surface corresponding to an outer surface of the dust container  50 . Therefore, when the dust container  50  is installed at the body part  30 , the exposed front surface of the prefilter case  361  surrounds and supports the outer surface of the dust container  50 . At this point, the front surface of the prefilter case  361  may be formed to be inclined and thereby to be in contact with the outer surface of the dust container  50  according to an inclined installation state of the dust container  50 . Therefore, when the dust container  50  is installed, the dust container  50  may be maintained in a stably supported state due to the front surface of the prefilter case  361 . 
     A filter hole  361   a  is formed at a position of the prefilter case  361  corresponding to a discharge port  512  of the dust container  50 . The filter hole  361   a  may be formed to have a size and shape corresponding to those of the discharge port  512 . And a case gasket  361   b  which is in close contact with a circumference of the discharge port  512  is formed around the filter hole  361   a  so that the dust container  50  and the prefilter case  361  are in close contact with each other and thus a leakage of the air is prevented. 
     A locker groove  361   c  is further formed at the prefilter case  361 . The locker groove  361   c  accommodates an upper locker  57  which is disposed to protrude from the outer surface of the dust container  50  when the dust container  50  is installed at the body part  30 . Therefore, the locker groove  361   c  may be formed to correspond to a protruding shape of the upper locker  57 . 
     A first restricting portion  361   d  which allows the prefilter body  362  to be maintained in a closed state may be formed at both side surfaces of the prefilter case  361 . The first restricting portion  361   d  may be formed in a recessed shape to accommodate a second restricting portion  362   c  which will be described below, and a restricting protrusion  361   e  may be formed at the first restricting portion  361   d  to protrude. 
     Meanwhile, a case gasket  361   g  may be further provided at a circumference of an opened rear end of the prefilter case  361 . The case gasket  361   g  may be in close contact with a front surface of the second barrier  342  and may allow the air passing through the prefilter assembly  36  to pass through the second barrier hole  342   a  without a leakage. 
     A first rotation coupling portion  361   f  may be formed at a lower end of the prefilter case  361 . The first rotation coupling portion  361   f  serves to allow the prefilter case  361  and the prefilter body  362  to be rotatably connected, and one pair of first rotation coupling portions  361   f  may protrude from the lower end of the prefilter case  361 . And a second rotation coupling portion  362   e  may be located between the pair of first rotation coupling portions  361   f , and the first rotation coupling portions  361   f  may be rotatably shaft-coupled to both ends of the second rotation coupling portion  362   e.    
     The prefilter body  362  may include a body grille  362   a  of which a front surface is opened and a rear surface is formed in a grille shape and which is in close contact with the second barrier  342  and a body flange  362   b  which extends along a perimeter of the body grille  362   a  and accommodates the prefilter case  361 . 
     If necessary, a gasket may be provided at the perimeter of the body grille  362   a  so that the second barrier  342  and the prefilter body  362  are airtightly in close contact with each other. And the body grille  362   a  may be formed in the grille shape so that the air introduced through the filter hole  361   a  passes through the filter member  363  and then passes through the second barrier hole  342   a.    
     The body flange  362   b  may be in close contact with an outer surface of the prefilter case  361  and may be formed such that a width of a lower end thereof is greater than that of an upper end thereof and a side surface thereof is inclined in order to allow the prefilter case  361  to be coupled in an inclined state. And the second restricting portion  362   c  which is seated on the first restricting portion  361   d  may be formed at both side surfaces of the body flange  362   b.    
     The second restricting portion  362   c  may be formed to protrude forward from both sides of the body flange  362   b  and may be formed in a shape which is accommodated in the first restricting portion  361   d . And a restricting hole  362   d  is formed at the second restricting portion  362   c . The restricting hole  362   d  serves to allow the restricting protrusion  361   e  to be inserted therein when the second restricting portion  362   c  is accommodated in the second restricting portion  362   c , thereby allowing the prefilter case  361  and the prefilter body  362  to be maintained in a closed state. 
     And the second rotation coupling portion  362   e  may be formed at the lower end of the body flange  362   b . The second rotation coupling portion  362   e  is rotatably coupled to the first rotation coupling portion  361   f  and also formed so that the prefilter case  361  and the prefilter body  362  are rotated about the first rotation coupling portion  361   f  and the second rotation coupling portion  362   e , respectively. Therefore, the prefilter case  361  may be opened and closed by being rotated about a lower end of the prefilter body  362  and may replace the filter member  363  after the prefilter body  362  is opened. 
     Various types of filters which may collect a variety of fine dust may be used as the filter member  363 , and the filter member  363  may be formed in a shape which is accommodated in an inner space of the prefilter body  362 . 
     The prefilter assembly  36  may be installed on the upper frame  34  while accommodating the filter member  363 , may support the dust container  50  while being installed on the upper frame  34  and may allow the air passed through the dust container  50  to be secondarily filtered and then to be supplied to the main motor  35 . 
     One pair of second side walls  343  may extend backward from a rear surface of the second barrier  342 . The second side walls  343  may form the space in which the main motor  35  is disposed and may also form a space in which a sub-PCB  305  is disposed. 
     Specifically, the main motor  35  may be provided between the pair of second side walls  343 , and the sub-PCB  305  may be installed at an outer surface of one of the second side walls  343 . That is, as illustrated in  FIG. 8 , the main motor  35  and the sub-PCB  305  may be respectively disposed at the spaces divided based on the second side walls  343 . 
     Meanwhile, the second barrier hole  342   a  may be formed at an area between the pair of second side walls  343 . Therefore, all of the air passing through the second barrier hole  342   a  may pass through the main motor  35 . 
     And a plate hole  341   a  may be formed at the cover plate  341  which forms a bottom of the upper frame  34 . The plate hole  341   a  may be formed at an area between the pair of the second side walls  343 . Therefore, the air introduced into the space for accommodating the main motor  35  through the second barrier hole  342   a  may be introduced into the space, which is formed at the lower frame  33  to accommodate the battery unit  38 , through the plate hole  341   a  and may cool the battery unit  38 . 
     The main motor  35  is provided at a space formed by the upper frame  34  and located at a rear side further than a center of gravity of the body part  30  and a center of the moving wheel  60 . Accordingly, due to an installation structure of the main motor  35 , a load is applied so that a rear end of the body part  30  is lowered by a weight of the main motor  35  while an external force is not provided. 
     And since the main motor  35  is disposed long in forward and backward directions, the center of gravity of the body part  30  may be located at a rear side further than the rotating center of the moving wheel  60  and may provide a rotational moment for clockwise rotating the body part  30 . 
     Meanwhile, the main motor  35  has a structure in which a fan and a motor are coupled inside a case for guiding the flow of the air. Various structures which force the flow of the air may be applied as such a structure of the main motor  35 . 
     And the main motor  35  may be installed at and fixed to the upper frame  34  by a motor supporting member  351 . The motor supporting member  351  may be formed of a rubber material or a material having elasticity, may reduce vibration generated when the main motor  35  is driven and thus may reduce a noise. 
     A motor cover  352  which surrounds at least a part of the main motor  35  may be further provided at a rear of the main motor  35 . A plurality of holes may be formed at the motor cover  352 , and thus the air forcibly blown by the main motor  35  may pass therethrough. And a sound absorbing material may be further provided between the motor cover  352  and the main motor  35  and may reduce the noise generated when the main motor  35  is driven. 
     And the main motor  35  is disposed at the space formed by the upper frame  34  to be leaned to one side at which the sub-PCB  305  is provided. That is, the main motor  35  is disposed adjacent to one of the pair of second side walls  343  at which the sub-PCB  305  is installed. Accordingly, a relatively wide space may be formed between the main motor  35  and one of the second side walls  343  which is distant from the sub-PCB  305 . 
     At least a part of the plate hole  341   a  may be exposed through an area between the main motor  35  and the second side wall  343  which is distant from the sub-PCB  305 . Also, the first barrier hole  331   a  may also be formed at an area of the same extension line as that of the plate hole  341   a.    
     Therefore, the air discharged through the main motor  35  may be discharged through the motor cover  352 . Since one of both lateral directions is blocked by the adjacent second side wall  343 , the air naturally flows through a space between the other second side wall  343  each of which has the plate hole  341   a . Since the air is allowed to smoothly flow to the first barrier hole  331   a , the flow noise may be reduced. 
     Meanwhile, a frame cover  36  may be provided at the upper frame  34 . The frame cover  36  may be formed to shield an opened upper surface of the upper frame  34 . Therefore, while the frame cover  36  is installed, the space in which the main motor  35  is accommodated may be sealed, and all of the air introduced through the second barrier hole  342   a  by the driving of the main motor  35  may pass through the main motor  35  and then may be discharged to the plate hole  341   a.    
     Meanwhile, the sub-PCB  305  may be provided at one of the pair of the second side walls  343 . The sub-PCB  305  controls driving of a sub-motor  201  which drives an agitator inside the suction unit  20 . A BLDC motor which is inexpensive and is easily controlled may be used as the sub-motor  201 , and the sub-PCB  305  may decrease a voltage of the input power to be suitable for the sub-motor  201  and then may supply the input power to the sub-motor  201 . 
     The sub-PCB  305  may be provided at a separate space of the upper frame  34  separately from the main PCB  301  and thus may be installed if necessary. That is, when the sub-motor  201  is not provided at the suction unit  20 , the sub-PCB  305  may not be installed, and thus the main PCB  301  may be commonly used. 
     Meanwhile, an upper portion of the cleaner body  10  may be formed by the upper decoration  37 . The upper decoration  37  may shield an opened upper portion of the base  31  and thus may shield internal elements installed at the base  31 . And the upper decoration  37  forms a part of an exterior of the upper surface of the cleaner body  10  and forms an upper exterior of the cleaner body  10  except a portion thereof shielded by the cover member  40 , the moving wheel  60  and the dust container  50 . 
     And the upper decoration  37  may be coupled to the lower decoration  315  which will be described below and may form a part of an exterior of a side surface of the cleaner body  10  by being coupled to the lower decoration  315 . 
       FIG. 9  is an exploded perspective view illustrating a coupling structure of the cleaner body  10 , the moving wheel and a detecting part when being seen in one direction. And  FIG. 10  is an exploded perspective view illustrating the coupling structure of the cleaner body  10 , the moving wheel and the detecting part when being seen in another direction.  FIG. 11  is a side view illustrating an installing state between the cleaner body  10  and a wheel gear assembly. And  FIG. 12  is a side view of the cleaner body  10 . 
     As illustrated in the drawings, one pair of side portions  316  formed to extend upward are formed at both side ends of the base  31 , respectively. The side portions  316  may provide a space in which the moving wheel  60  and the wheel motor assembly  63  for driving the moving wheel  60  are installed. The pair of side portions  316  may be provided at both of left and right sides, and a structure in which the wheel motor assembly  63  is installed may be the same as that in which the moving wheel  60  is installed. 
     Each of the side portions  316  may extend to a position higher than the center of the moving wheel  60  and may be formed smaller than the moving wheel  60 . A wheel boss  316   a  in which the moving wheel  60  is rotatably installed may be provided at a center of each of the side portions  316 . The wheel boss  316   a  may extend from the side portion  316  toward the center of the moving wheel  60 . While the moving wheel  60  is installed at the wheel boss  316   a , the moving wheel  60  may be rotated by the wheel motor assembly  63  and a wheel gear  64 . And the cleaner body  10  may also be in a rotatable state using the wheel boss  316   a  as an axis. 
     And the wheel motor assembly  63  may be provided at a lateral side of the wheel boss  316   a . When the moving wheel  60  is installed at the wheel boss  316   a , the wheel motor assembly  63  may be shielded by the moving wheel  60 . That is, the wheel motor assembly  63  may be provided at a space formed between the side portion  316  and the moving wheel  60 . 
     The wheel motor assembly  63  may include a wheel motor  632 , a wheel motor case  631  and a plurality of moving gears (not shown) which are provided inside the wheel motor case  631  to transmit power to the wheel gear  64 . 
     The wheel motor  632  may be configured with a BLCD motor of which rotation is easily controlled and which is light. And the plurality of moving gears which connect a rotating shaft of the wheel motor  632  with the wheel gear  64  of the moving wheel  60  decelerates rotation of the wheel motor  632  and then transmits the rotation to the moving wheel  60 . 
     Meanwhile, the wheel motor assembly  63  may be installed at a rear side further than the rotating center of the moving wheel  60 . Specifically, a case installing groove  633  which is recessed inward may be formed at the wheel motor case  631 . The case installing groove  633  is recessed in a shape corresponding to the wheel boss  316   a  and formed to accommodate at least a part of the wheel boss  316   a . That is, while the wheel motor assembly  63  is installed, the case installing groove  633  is installed to surround a second half portion of an outer surface of the wheel boss  316   a  and disposed at a rear side of the wheel boss  316   a . Therefore, the wheel motor assembly  63  may allow the center of gravity of the cleaner body  10  to be located at a further rear side while being installed at the cleaner body  10 . 
     And the wheel motor  632  is located at a lower portion of the wheel motor case  631 , and the plurality of moving gears are located above the wheel motor  632 . That is, since the wheel motor  632  which is relatively heavy is disposed at the lower side, the center of gravity of the cleaner body  10  may be located at a further lower side. 
     The lower decoration  315  which forms the exterior of the body part  30  exposed to an outside of the moving wheel  60  may be installed at the side portion  316 . The lower decoration  315  may be formed along at least a part of a circumference of the moving wheel  60 , may be formed to have a curved surface which is continued to a curved surface of the moving wheel  60  and thus may form a smooth exterior. 
     A plurality of reinforcing ribs  316   b  which vertically extend may be further formed at an inner surface of the side portion  316 , i.e., a surface thereof opposite to a surface at which the wheel boss  316   a  is formed. Since the plurality of reinforcing ribs  316   b  are formed, the side portion  316  may be prevented from being damaged by a load which is laterally applied. And the moving wheel  60  may be maintained in a stably coupled state. 
     Meanwhile, a detecting part  306  may be further provided at one side of the inner surface of the side portion  316 . The detecting part  306  may detect a moving state or a posture of the cleaner body  10  and may control the driving of the moving wheel  60 . The detecting part  306  serves to detect movement of the cleaner body  10  and may include a gyro sensor or an acceleration sensor which is typically widely used. Of course, instead of the gyro sensor or the acceleration sensor, various sensors or devices which detect the movement of the cleaner body  10  may be used as the detecting part  306 . 
     The detecting part  306  may be installed at an upper portion of the inner surface of the side portion  316 . The detecting part  306  may include a detection PCB  360   a  on which the gyro sensor is mounted and a detecting part fixing member  306   b  which fixes the detection PCB  360   a  and is installed at the side portion  316 . And one pair of fixing hooks  306   c  may be provided at the detecting part fixing member  306   b  and may be inserted and fixed into detecting part fixing holes  316   c  formed at the side portion  316 . 
     Meanwhile, the detection PCB  360   a  may be formed to control driving of the wheel motor  632  provided at both sides thereof. That is, a configuration for controlling the gyro sensor and the wheel motor  632  may be configured with one PCB. 
     As described above, the detecting part  306  may be installed at and fixed to the side portion  316 , and an installation position of the detecting part  306  may be disposed at one side which is distant from the rotating center of the moving wheel  60  used as the rotating shaft of the cleaner body  10 . Therefore, when the cleaner body  10  is travelled or stopped, a rotation angle, i.e., a slope of the cleaner body  10  may be effectively detected. 
     While the cleaner body  10  is in the stopped state, the center of gravity thereof is located at a rear of the center of the moving wheel  60 . Therefore, the cleaner body  10  is maintained in a state which is intended to be clockwise rotated based on the center of the moving wheel  60 . And the cleaner body  10  is maintained in a supported state by the rear wheel unit  70  which is in contact with the ground. Accordingly, a bottom surface of the cleaner body  10 , in particular, the first half portion  312  may be maintained at a predetermined angle. 
     In this state, the detecting part  306  determines whether the cleaner body  10  is being travelled or stopped through the slope of the cleaner body  10 , i.e., the angle of the first half portion  312 . 
     Specifically, the wheel motor assembly  63 , the battery unit  38  and the main motor  35  may be disposed at a rear of the center of the moving wheel  60 . Therefore, the center G of gravity of the cleaner body  10  is located at a rear side further than the rotating center C of the moving wheel  60 , and thus the cleaner body  10  is naturally in the state which is intended to be clockwise rotated based on the center of the moving wheel  60 . 
     And the second half portion  313  of the cleaner body  10  may be supported by the rear wheel unit  70  installed at the second half portion  313  of the base  31 . Therefore, the cleaner body  10  may be prevented from being excessively rotated clockwise and may be stably maintained at a set angle α. 
     In particular, due to a characteristic of the vacuum cleaner  1 , the dust is accumulated in the dust container  50  after the vacuum cleaner  1  is used. In consideration of this fact, the center of gravity of the cleaner body  10  is always located at the second half portion thereof and supported by the rear wheel unit  70 , and thus the cleaner body  10  may maintain a constant slope with respect to the ground while being in the stopped state, regardless of an amount of the dust. 
     In this state, when the detecting part  306  detects an angle of the first half portion  312  and confirms that the first half portion  312  maintains the set angle α, it is determined that the cleaner body  10  maintains a set posture in the stopped state. Therefore, the main PCB  301  controls the wheel motor assembly  63  not to be operated, thereby maintaining the stopped state of the cleaner body  10 . 
     Meanwhile, when the user grips and moves forward the handle  23  to use the vacuum cleaner  1 , the cleaner body  10  is inclined due to a position of the handle  23 . That is, the cleaner body  10  is counterclockwise rotated so that the first half portion  312  is moved further downward. 
     At this point, the detecting part  306  detects a change in the angle of the first half portion  312  and determines a fact that the movement of the vacuum cleaner  1  starts according to the change in the angle. Therefore, the main PCB  301  may determine that the cleaner body  10  is moved and thus may rotate the moving wheel  60  by driving the wheel motor assembly  63 . 
     And when the movement of the cleaner body  10  is stopped again, the cleaner body  10  is rotated to an initial state by the center of gravity, and the detecting part  306  checks a fact that the angle of the first half portion  312  coincides with the set angle α in the stopped state. Therefore, the main PCB  301  may determine that the movement of the cleaner body  10  is completed and may control the wheel motor assembly  63  to be stopped. 
     Meanwhile, as illustrated in  FIG. 11 , the bottom surface of the cleaner body  10 , i.e., the center portion  311 , the first half portion  312  and the second half portion  313  of the base  31  may have a predetermined angle. The angle of each of the center portion  311 , the first half portion  312  and the second half portion  313  may be set variously. Hereinafter, the angle of the base  31  in the stopped state of the cleaner body  10  will be described. 
     For example, the first half portion  312  may be formed to be inclined at an angle of 27° with respect to the ground. The first half portion  312  may hardly collide with the ground by allowing the first half portion  312  to have the angle of 27° even when the suction hose  24  is pulled and the cleaner body  10  is rotated. Of course, the first half portion  312  may be in contact with the ground due to an unexpected operation. In this case, the movement of the cleaner body  10  may be smoothly performed by a rolling motion of the front wheel  312   a . Also, the first half portion  312  may be easily moved over the carpet, the door sill or the like due to the slope of the first half portion  312  while the cleaner body  10  is being travelled. 
     And the center portion  311  may be formed to be inclined at an angle of 7° with respect to the ground while the cleaner body  10  is in the stopped state. When the moving wheel  60  is rotated by the driving of the wheel motor  632  and thus the cleaner body  10  is travelled, the cleaner body  10  is counterclockwise rotated by an angle of about 7°. Therefore, while the cleaner body  10  is being travelled, the center portion  311  is maintained in a horizontal state with the ground, and thus the bottom of the vacuum cleaner  1  may be prevented from being caught by foreign substances or the like in a room. 
     And the second half portion  313  may be formed to be inclined at an angle of 10° with respect to the ground while the cleaner body  10  is in the stopped state. Therefore, the cleaner body  10  may be clockwise rotated by the center of gravity of the cleaner body  10  which is eccentric to a rear side while the cleaner body  10  is in the stopped state and then may be seated on the ground. 
     That is, in the stopped state, the cleaner body  10  is already in a state in which the second half portion  313  thereof is moved down due to the center of gravity and thus may be maintained in the stably supported state by the rear wheel unit  70 , regardless of the amount of the dust stored in the dust container  50 . 
     Also, due to the inclined second half portion  313 , the second half portion  313  may be prevented from colliding with the ground when the suction hose  24  is pulled and the cleaner body  10  is rotated, and thus rotation of the cleaner body  10  may be prevented from being restricted. 
     Meanwhile, the moving wheel  60  may include a wheel frame  61  which is rotatably installed at the wheel boss  316   a  of the side portion  316  and at which the wheel gear  64  is installed, and a wheel decoration  62  which forms an exterior of the moving wheel  60  by being coupled to an outer surface of the wheel frame  61 . 
     The wheel frame  61  forms a substantive framework of the moving wheel  60  and performs the rolling motion while being in contact with the ground, and a plurality of ribs  611  for reinforcing an entire strength may be radially provided at an inside surface and an outer surface thereof. Also, a wheel gear installing portion  612  to which the wheel gear  64  is fixed is formed at a center of the wheel frame  61 . The wheel gear  64  may be rotatably installed at the wheel boss  316   a  while being fixed to the wheel frame  61 . 
     Meanwhile, a wheel opening  621  is formed at a center of the wheel decoration  62 , and a coupling member by which the wheel gear  64  and the wheel frame  61  are coupled may be fastened through the wheel opening  621 . And a wheel cap  623  may be installed at the wheel opening  621  and may shield the wheel opening  621 . 
     Meanwhile, in  FIG. 12 , the cleaner body  10  may be divided into a front side and a rear side by a vertical extension line L v , which extends vertically to the ground (or the floor surface), based on the rotating center C of the moving wheel  60 . 
     And the cleaner body  10  may be divided into an upper side and a lower side by a horizontal extension line L H , which extends horizontally with the ground (or the floor surface), based on between the main motor  35  and the battery unit  38 . 
     The cleaner body  10  may be divided into four areas, i.e., four quadrants by the vertical extension line L v  and the horizontal extension line L H . Hereinafter, main configurations of the cleaner body  10  will be described based on the vertical extension line L v  and the horizontal extension line L H . 
     The main motor  35  may be located at a first quadrant of the cleaner body  10 , i.e., a rear of the vertical extension line L v  and an upper side of the horizontal extension line L H . And the battery unit  38  may be located at a fourth quadrant of the cleaner body  10 , i.e., the rear of the vertical extension line L v  and a lower side of the horizontal extension line L H . And a hole formed at a position at which the connector  401  or the suction hose  24  is connected may be located at a second quadrant of the cleaner body  10 , i.e., a front of the vertical extension line L v  and the upper side of the horizontal extension line L H . And at least a part of a bottom surface of the dust container  50  may be located at a third quadrant of the cleaner body  10 , i.e., the front of the vertical extension line L v  and the lower side of the horizontal extension line L H . 
     Due to such an arrangement, the center G of gravity of the entire cleaner body  10  may be located at the rear of the vertical extension line L v . At this time, the center G of gravity may be located at any one of the upper side and the lower side of the horizontal extension line L H . However, the center G of gravity should be located at a position at which a rear end of the cleaner body  10  or the rear wheel unit  70  is rotatable to be in contact with the ground. 
     Also, the center G of gravity may be disposed so that the rear end of the cleaner body  10  or the rear wheel unit  70  is in contact with the ground while the vacuum cleaner  1  is in the stopped state, regardless of the amount of the dust collected in the dust container  50  by using the vacuum cleaner  1 . 
     Also, the wheel motor assembly  63  may also be located at the rear of the vertical extension line L v  so that the center G of gravity is more easily disposed at the rear side. 
       FIG. 13  is a bottom view of the cleaner body  10 . And  FIG. 14  is an exploded perspective view illustrating a coupling structure of the rear wheel unit  70  according to the embodiment of the present invention. And  FIG. 15  is a cross-sectional view illustrating an operating state of the rear wheel unit  70 . 
     As illustrated in the drawings, the rear wheel unit  70  may be provided at the base  31 . A base recessing portion  311   b  which is recessed inward is formed at the rear end of the center portion  311  of the base  31 . And a wheel installing portion  311   c  for installing the rear wheel unit  70  is formed at a front end of each of both side surfaces of the base recessing portion  311   b.    
     The rear wheel unit  70  is in contact with the ground while the cleaner body  10  is not moved and allows the cleaner body  10  to be maintained in a set posture. And the rear wheel unit  70  is in contact with the ground while the cleaner body  10  is rotated so that the first half portion  312  is lifted, also provides elasticity for reverse rotation of the cleaner body  10  and thus may prevent the cleaner body  10  from being excessively rotated or overturned. 
     The rear wheel unit  70  may include a wheel supporter  71  and a rear wheel  72 . The wheel supporter  71  allows the rear wheel  72  to be rotatably installed and also is in contact with a lower surface of the base  31 , thereby providing predetermined elasticity. 
     Specifically, the wheel supporter  71  may include one pair of legs  73  which are provided at both of left and right sides thereof, a wheel accommodating portion  74  which connects front ends of the legs  73  and at which the rear wheel  72  is installed and an elastic portion  75  which is provided between the legs  73  and is in contact with the base  31  to provide the elasticity. 
     The legs  73  serve to install the wheel supporter  71  and may be provided at both sides which are spaced apart from each other, and a leg protrusion  731  which protrudes outward may be formed at an upper end of each of the legs  73 . The leg protrusion  731  may be inserted inside the wheel installing portion  311   c , and the wheel supporter  71  may be installed to be rotatable using the leg protrusion  731  as an axis. 
     The wheel accommodating portion  74  is provided at the front end of each of the pair of the legs  73  and formed to connect between the pair of legs  73 . And the wheel accommodating portion  74  is formed in a shape which is opened downward and provides a space in which the rear wheel  72  is accommodated. And a shaft installing portion  741  at which a rotating shaft  721  of the rear wheel  72  is rotatably connected may be further formed at each of both ends of the wheel accommodating portion  74 . Therefore, the rear wheel  72  may be rotated while being accommodated inside the wheel accommodating portion  74 . 
     The elastic portion  75  may be provided between the legs  73  and may extend from a first half portion of each of the legs  73  toward a second half portion thereof. And the elastic portion  75  may extend with a predetermined curvature so that an extending end thereof is directed to the base  31 . Also, the elastic portion  75  may be formed in a plate shape and may extend to be elastically deformed when being in contact with the base  31 . 
     The extending end of the elastic portion  75  may be in contact with the base  31  while the vacuum cleaner  1  is stopped. At this time, the rear wheel  72  may be in contact with the rear wheel  72 . Therefore, the cleaner body  10  may be supported by the pair of moving wheels  60  and the rear wheel  72  located at a rear of the moving wheel  60  and may be maintained in a stable state. 
     And when the cleaner body  10  is rotated using the moving wheel  60  as an axis by moving the cleaner body  10 , the elastic portion  75  may be elastically deformed and thus may prevent the cleaner body  10  from being excessively rotated or overturned. And when the vacuum cleaner  1  is moved and then stopped and thus an external force which rotates the vacuum cleaner  1  is removed, the cleaner body  10  is returned to its original position due to a restoring force of the elastic portion  75 . 
     Meanwhile, the terminal installing portion  311   a  which allows the power supply terminal  307  to be installed and exposed downward is formed at one side of the base  31  corresponding to the power supply terminal  307 . The terminal installing portion  311   a  is formed so that a lower surface thereof is opened, and the power supply terminal  307  may be provided therein. And the terminal installing portion  311   a  may be located adjacent to one of the moving wheels  60 . Accordingly, by seating and fixing the moving wheel  60  at the charging device, the power supply terminal  307  and the charging device may be aligned with each other. 
       FIG. 16  is a rear view illustrating a state in which the rear cover of the cleaner body  10  is opened. And  FIG. 17  is an exploded perspective view illustrating a coupling structure of a battery and a filter according to the embodiment of the present invention. 
     As illustrated in the drawings, the rear cover  314  may be provided at a rear surface of the cleaner body  10 . The rear cover  314  may be rotatably installed at the base  31  and may be formed to open and close the rear opening  317  formed by the base  31  and the upper decoration  37  by rotation thereof. 
     A rear cover restricting portion  314   a  which is selectively fixed to a rear end of the upper decoration  37  may be formed at an upper end of the rear cover  314 . Therefore, the rear cover  314  may be opened and closed by an operation of the rear cover restricting portion  314   a.    
     And a cover rotating shaft  314   b  is formed to protrude from each of both sides of the lower end of the rear cover  314 . The cover rotating shaft  314   b  may be coupled to the base  31 , and the rear cover  314  may open and close the rear opening  317  by being rotated about the cover rotating shaft  314   b  when the rear cover  314  is opened and closed. 
     Meanwhile, a space in which a filter and the battery unit  38  are provided may be formed at the second half portion of the cleaner body  10 , i.e., a rear of the center of the moving wheel  60 . And the space in which the filter unit  39  and the battery unit  38  are accommodated may be defined by the lower frame  33 . The lower frame  33  includes the first barrier  331  and the first side wall  332 , and the space in which the filter unit  39  and the battery unit  38  are provided may be formed by coupling between the base  31  and the upper frame  34 . 
     The filter unit  39  may include a filter case  391  which forms an exterior and a filter member  392  which is provided inside the filter case  391 . The filter member  392  serves to filter ultra-fine dust (defined as particles smaller than dust and fine dust) contained in the air passed through the dust container  50  and the main motor  35 , and a HEPA filter may be generally used as the filter member  392 . Of course, if necessary, various types of filters which filter the ultra-fine dust may be used as the filter member  392 . 
     The filter case  391  may be disposed at an upper portion of the space and may be formed to be in contact with a bottom surface of the upper frame  34  while being in an installed state. Therefore, all of the air introduced into the space through the plate hole  341   a  of the upper frame  34  may be purified while passing through the filter unit  39 , may cool the battery unit  38  and then may be discharged to an outside. 
     Some of the air introduced into the space through the plate hole  341   a  may be moved forward through the first barrier hole  331   a  of the first barrier  331  and may cool the noise filter  302  and the main PCB  301  during the above-described process. 
     A filter handle  393  may be formed at a rear end of the filter case  391 . The filter handle  393  may be exposed when the rear cover  314  is opened, and thus the user may separate the filter unit  39  from the space by gripping and pulling the filter handle  393 . 
     And a filter groove  394  may be formed at each of both side surfaces of the filter case  391 . The filter groove  394  may extend from the rear end of the filter case  391  in a lengthwise direction and may be inserted into a filter guide  333  formed at the second side wall  343 . 
     That is, when the filter case  391  is installed in the space, the filter case  391  is inserted while the filter grooves  394  are aligned between the filter guides  333  formed at both side surfaces thereof. Therefore, the filter case  391  may be completely inserted into the space along the filter guides  333 . In this state, the filter case  391  may be maintained in an installed state to be in contact with the bottom surface of the upper frame  34 . 
     The battery unit  38  may supply electric power necessary to drive the vacuum cleaner  1 . The battery unit  38  may be configured with a secondary cell which is chargeable and dischargeable. Of course, a power cord (not shown) for supplying commercial electric power may be separately connected to the battery unit  38 . 
     Meanwhile, although not illustrated, in the case of a model in which the battery unit  38  is not provided, a cord reel (not shown) on which an electric wire for supplying the electric power is wound may be provided instead of the battery unit  38 . The center of gravity may be moved backward by the cord reel. 
     The battery unit  38  may include a battery case  381  and a secondary cell  383  which is accommodated inside the battery case  381 . The secondary cell  383  may be arranged to be aligned in the battery case  381 . 
     The battery case  381  may be formed in a size which is accommodated in the space, and a battery grille  381   a  may be formed at an upper surface and a lower surface thereof and a position thereof corresponding to the rear cover  314 . Therefore, the air passed through the filter unit  39  and introduced into the space may cool the secondary cell  383  while passing through an inside of the battery case  381  via the battery grille  381   a.    
     And a battery handle  382  which is gripped by the user when the battery unit  38  is inserted into or withdrawn from the space may be formed at a rear surface of the battery case  381 . And battery grooves  384  may be formed at both side surfaces of the battery case  381 . The battery grooves  384  may be recessed from both of the side surfaces of the battery case  381  and may extend backward from front ends thereof. 
     A battery guide  334  formed at a lower portion of the first side wall  332  is inserted into the battery groove  384 . When the battery unit  38  is installed, the battery guide  334  may be inserted along the battery groove  384 , and thus the battery unit  38  may be correctly installed. 
     Meanwhile, a battery restricting portion  335  and a battery restricting member  336  may be provided at the battery guides  334  of both sides of the first side wall  332 , respectively. The battery restricting portion  335  and the battery restricting member  336  may serve to allow the battery unit  38  to be maintained in an installed state inside the space, may be located at positions facing each other and may be caught and restricted by battery restricting grooves  385  formed at both side surfaces of the battery case  381 . 
     Specifically, the battery restricting portion  335  may include a first elastic portion  335   a  which is formed by cutting a part of the first side wall  332  and a first restricting protrusion  335   b  which is formed at an end of the first elastic portion  335   a . Therefore, while the battery unit  38  is inserted, the first elastic portion  335   a  may be elastically deformed, and when the battery unit  38  is completely inserted, the first restricting protrusion  335   b  is caught and restricted by the battery restricting grooves  385  and thus may restrict one side of the battery unit  38 . 
     Meanwhile, the battery restricting member  336  is installed at and fixed to the first side wall  332  which faces the battery restricting portion  335 . A side hole  334   a  which is formed in a shape corresponding to the battery restricting member  336  is opened at the first side wall  332  at which the battery restricting member  336  is installed. And a restricting member fixing portion  334   b  to which a perimeter of the battery restricting member  336  is fitted and fixed may be formed at the side hole  334   a . Therefore, the battery restricting member  336  may be installed and fixed by the fitting, and a hook may be formed at an end of the restricting member fixing portion  334   b , and thus the battery restricting member  336  may be maintained in a fixed state. 
     The battery restricting member  336  may be formed of a different type of material from that of the battery restricting portion  335 . For example, the battery restricting portion  335  may be integrally formed with the lower frame  33  and may be injection-molded with an ABS material. And the battery restricting member  336  may be injection-molded with a POM material. The battery restricting member  336  and the battery restricting portion  335  may be separately formed of different materials from each other, thus may prevent a damage of a restricting portion when the battery unit  38  is installed and may be more effectively coupled. 
     The battery restricting member  336  may include a restricting member flange  336   a  formed in a quadrangular shape corresponding to the side hole  334   a . The restricting member flange  336   a  may be maintained in an installed and fixed state to the side hole  334   a  by a perimeter of the battery restricting portion  335 . And the battery restricting member  336  may include a second elastic portion  336   b  and a second restricting protrusion  336   c.    
     The second elastic portion  336   b  and the second restricting protrusion  336   c  may be formed in shapes corresponding to the first elastic portion  335   a  and the first restricting protrusion  335   b . That is, the second elastic portion  336   b  may be formed by cutting an inside of the battery restricting member  336 , may extend in a predetermined length and may have elasticity. And the second restricting protrusion  336   c  may be formed at an end of the extending second elastic portion  336   b.    
     Therefore, while the battery unit  38  is inserted, the second elastic portion  336   b  may be elastically deformed, and when the battery unit  38  is completely inserted, the second restricting protrusion  336   c  may be caught and restricted by the battery restricting grooves  385  and thus may restrict the battery unit  38 . 
     Meanwhile, a battery terminal  331   b  which is connected to the battery unit  38  while the battery unit  38  is completely inserted may be provided at a lower end of the first barrier  331 . The battery terminal  331   b  may protrude in an insertion direction of the battery unit  38  and may be formed to be coupled to a front surface of the battery unit  38 . And the battery terminal  331   b  may be electrically connected to the battery unit  38  and may supply the electric power for driving the internal elements of the vacuum cleaner  1 . 
     A holder  371  may be provided above the rear opening  317  which is shielded by the rear cover  314 . The holder  371  serves to fix, install and accommodate the extension pipe  22  when the vacuum cleaner  1  is not used and may be formed so that an opening  371   a  formed therein becomes narrower from an opening upper side thereof toward a lower side thereof. 
     And the holder  371  may be molded separately from the upper decoration  37  and may be inserted and installed into the upper decoration  37 . And the holder  371  may be additionally fixed to the body part  30  by a holder fixing member  371   b  and may be prevented from being damaged when a shock and a load are generated due to the installation of the extension pipe  22 . The holder  371  may be formed of a metallic material. The holder  371  may be molded by a die-casting and may have a higher strength. 
       FIG. 18  is a cross-sectional view of the cleaner body  10  before the battery is installed. And  FIG. 19  is a cross-sectional view of the cleaner body  10  in a state in which the battery is installed. 
     As illustrated in  FIG. 18 , before the battery unit  38  is installed, the battery restricting portion  335  and the battery restricting member  336  are disposed at positions which face each other. And the first elastic portion  335   a  and the second elastic portion  336   b  are in a state in which the external force is not applied thereto, and the first restricting protrusion  335   b  and the second restricting protrusion  336   c  are in a protruding state to an internal space of the lower frame  33 . 
     In this state, the user may open the rear cover  314  to expose the space and then may install the battery unit  38 . After the rear cover  314  is opened, the battery unit  38  is inserted inside the space. At this point, the battery unit  38  may be slidingly inserted while the battery guide  334  and the battery groove  384  are aligned. When the battery unit  38  is completely inserted, the front surface of the battery unit  38  may be coupled to the battery terminal  331   b  and may supply the electric power to the internal elements of the cleaner body  10 . 
     While the battery unit  38  is completely inserted and installed, the front surface of the battery unit  38  is in a contacting state with the first barrier  331 , as illustrated in  FIG. 19 . While the battery unit  38  is being inserted, the first elastic portion  335   a  and the second elastic portion  336   b  are elastically deformed outward. And in a state in which the battery unit  38  is inserted, the first restricting protrusion  335   b  and the second restricting protrusion  336   c  may be inserted into the battery restricting grooves  385  formed at both side surfaces of the battery case  381  and may be maintained in a fixed state. 
       FIG. 20  is a perspective view of the cover member. And  FIG. 21  is an exploded perspective view of the cover member. And  FIG. 22  is a partial cross-sectional view illustrating a coupling structure of the cover member and the obstacle detecting member. 
     As illustrated in the drawings, the cover member  40  may form the upper portion of the cleaner body  10  and may be formed to have a structure which shields an upper end of the upper decoration  37  and an upper end of the dust container  50 . 
     The cover member  40  may generally include a cover base  42  and an outer cover  43 . The cover base  42  forms a lower surface of the outer cover  43  and substantially shields the dust container  50  and the opened upper surface of the body part  30 . 
     A cover member coupling portion  421  is formed at a rear end of the cover base  42 , and the cover member coupling portion  421  may be shaft-coupled to an upper end of the body part  30 , more specifically, the rear end of the upper decoration  37 . And a connecting hole  422  which is connected to the connector  401  may be formed at a front end of the cover base  42 . 
     The obstacle detecting member  44  may be provided at the cover base  42 . The obstacle detecting member  44  serves to check an obstacle while the cleaner body  10  is being travelled and may be disposed along a front surface of the cover base  42 . 
     A plurality of obstacle detecting members  44  may be provided at a center of the front surface of the cover base  42 , i.e., both of left and right sides based on the connector  401 . That is, two obstacle detecting members  44  may be provided at each of the left and right sides based on the center of the cover base  42 , and each of the obstacle detecting members  44  may be formed to have a detection range of about 25° using a laser sensor  441 . And the plurality of obstacle detecting members  44  may be disposed so that adjacent obstacle detecting members  44  are directed in different directions from each other. 
     The obstacle detecting members  44  may include front sensors  44   b  and  44   c  and side sensors  44   a  and  44   d . The front sensors  44   b  and  44   c  serve to detect the obstacle located at a front of the cleaner body  10 . When the obstacle is appeared at the front of the cleaner body  10  while the cleaner body  10  is travelled, the front sensors  44   b  and  44   c  detect the obstacle. And the side sensors  44   a  and  44   d  serve to detect the obstacle located at a lateral side of the cleaner body  10 . When the obstacle is appeared at the lateral side adjacent to the cleaner body  10  while the cleaner body  10  is travelled, the side sensors  44   a  and  44   d  detect the obstacle. In particular, the side sensors  44   a  and  44   d  allow the cleaner body  10  to be travelled without a collision with a corner of a wall surface through a combination of the front sensors  44   b  and  44   c.    
     More specifically, the front sensors  44   b  and  44   c  may be respectively located at both of left and right sides of the connector  401  and may be disposed to emit light in a diagonal direction between the front and the lateral side. That is, as illustrated in  FIG. 22 , centers of the front sensors  44   b  and  44   c  may be located at positions which are clockwise and counterclockwise rotated at 45° with respect to a center of the connector  401 . Therefore, the centers of the front sensors  44   b  and  44   c  may form an angle of 90° with respect to each other. 
     And since the detection range of each of the obstacle detecting members  44  is about 25°, a non-detected area S is generated between the front sensors  44   b  and  44   c . The non-detected area S may have an angle of 65°. The non-detected area S is an area at which the suction hose  24  may be located while the cleaner body  10  is travelled and which prevents the suction hose  24  from being regarded as the obstacle by the front sensors  44   b  and  44   c . That is, even when the user moves the suction hose  24  while performing a cleaning operation, the front sensors  44   b  and  44   c  may be prevented from erroneously recognizing the suction hose  24  as the obstacle, and thus the cleaner body  10  may be prevented from being abnormally travelled. 
     The side sensors  44   a  and  44   d  are located at a rear side further than the front sensors  44   b  and  44   c  and disposed to emit the light toward the lateral side of the cleaner body  10 . That is, the side sensors  44   a  and  44   d  may be disposed at both sides based on the connector  401  to form an angle of about 90°. Therefore, the side sensors  44   a  and  44   d  may detect the obstacle appeared at the lateral side of the cleaner body  10 . 
     Meanwhile, each of the side sensors  44   a  and  44   d  may be formed to have a detecting distance shorter than that of each of the front sensors  44   b  and  44   c . For example, each of the front sensors  44   b  and  44   c  may be formed to have a detection distance L 1  of about 600 mm toward the front side, and each of the side sensors  44   a  and  44   d  may be formed to have a detection distance L 2  of about 350 mm toward the lateral side. 
     Since the obstacle located at the front of the cleaner body  10  has a high possibility of interfering with the cleaner body  10  while the cleaner body  10  is travelled, it is necessary to detect the obstacle which is located at a long distance. In the case of the obstacle which is located at the lateral side, there is a low possibility of interfering with the cleaner body  10  while the cleaner body  10  is travelled, and when a distant object located at the lateral side is recognized as the obstacle, it may be impossible that the cleaner body  10  is normally travelled. 
     In particular, when the detection distance L 2  of each of the side sensors  44   a  and  44   d  is set shorter than that L 1  of each of the front sensors  44   b  and  44   c , the cleaner body  10  may smoothly escape from a wall surface or a corner when passing the wall surface or the corner. 
     Meanwhile, the obstacle detecting members  44  may include the laser sensor  441  and a sensor substrate  442  on which the laser sensor  441  is installed. Elements for driving or controlling the laser sensor  441  may be further installed on the sensor substrate  442 . Of course, instead of the laser sensor  441 , various means, such as an ultrasonic sensor, a proximity sensor and a vision camera, which detect the obstacle located at the front side may be used as the obstacle detecting members  44 . 
     And a locking assembly  80  which enables the cover member  40  to be selectively restricted may be further provided between the cover base  42  and the outer cover  43 . The locking assembly  80  may include a push member  81 , and a main link  83  and a sub-link  84  which are interlocked with the push member  81 . 
     The outer cover  43  forms an exterior of the cover member  40  and forms an exterior of the upper portion of the cleaner body  10  while the cover member  40  is closed. The connector  401  connected to the fitting portion  241  of the suction hose  24  is formed at a front end of the outer cover  43 . The connector  401  is connected to the connecting hole  422  and allows the dust and the air suctioned through the suction unit  20  to be introduced toward the dust container  50 . 
     A detecting hole  431  may be formed at a front surface of the outer cover  43  based on the connector  401 . The detecting hole  431  may be opened at a position corresponding to the laser sensor  441  and may be formed so that the light for detecting the obstacle is transmitted and received therethrough. 
     Meanwhile, the detecting hole  431  may be opened at a position corresponding to each of the front sensors  44   b  and  44   c  and the side sensors  44   a  and  44   d  and may be formed so that both of internal side surfaces thereof are inclined. Accordingly, the light may be emitted by a set angle range. 
     And if necessary, a hole cover  432  which is formed of a material through which the light of the laser sensor  441  is transmitted and which shields the detecting hole  431  may be further provided at the detecting hole  431 . A plurality of detecting holes  431  may be formed at the same height and may be located at positions symmetric to each other based on the connector  401 . As described above, the detecting holes  431  and the obstacle detecting members  44  may be disposed at a front surface of the cover member  40 , which is not shielded by the body part  30  but is exposed forward, to detect the obstacle while the cleaner body  10  is travelled. 
     The grip portion  41  may be formed at an upper surface of the outer cover  43 . The grip portion  41  may extend from one side of the connector  401  to a rear end of the outer cover  43 . And the push member  81  which is pushed by the user to selectively restrict the cover member  40  may be provided at the grip portion  41 . By an operation of the push member  81 , a cover restricting protrusion  843  may selectively protrude toward both sides of the cover member  40  and may selectively restrict the cover member  40  to the body part  30 . 
       FIG. 23  is an exploded perspective view illustrating a coupling structure of the locking assembly according to the embodiment of the present invention. 
     As illustrated in the drawing, the locking assembly  80  may include the push member  81  which is pushed by the user, a transmission member  82  which transmits the operation of the push member  81 , the main link  83  which is rotated by the transmission member  82  and the sub-link  84  which is horizontally moved by rotation of the main link  83 . 
     The push member  81  may be accommodated inside the grip portion  41  and may be disposed to be movable vertically. The grip portion  41  may be formed by coupling a grip portion cover  411  with a grip portion body  412 , and the push member  81  may be installed at the grip portion body  412 . A cover opening  411   a  may be formed at the grip portion cover  411 , and the push member  81  may be exposed through the cover opening  411   a.    
     A transmission member installing portion  811  which extends downward is formed at a lower surface of the push member  81 . The transmission member  82  is installed at the transmission member installing portion  811 . The transmission member  82  and the push member  81  may be shaft-coupled to each other. When the push member  81  is vertically moved, the transmission member  82  may be vertically moved together while being rotated at a predetermined angle. 
     And a transmission member inclined portion  821  may be formed at a lower surface of the transmission member  82 . The transmission member inclined portion  821  serves to be in contact with the main link  83  which will be described below and to move the main link  83  and is formed so that a width thereof is increased upward from a lower end thereof to form an inclined surface. 
     The main link  83  and the sub-link  84  may be coupled and interlocked with each other, and one pair of main links  83  and one pair of sub-links  84  may be provided at both of left and right sides based on a center of the cover base  42 , respectively. That is, the main links  83  and the sub-links  84  may include a first main link  83   a  and a first sub-link  84   a  which are provided at the left side based on  FIG. 23  and a second main link  83   b  and a second sub-link  84   b  which are provided at the right side. 
     The main link  83  may be rotatably coupled to the cover base  42  by a fastening boss  85 . The main link  83  includes a through portion  831  through which the fastening boss  85  passes, a first extending portion  832  which extends from the through portion  831  toward a center thereof at which the transmission member  82  is located and a second extending portion  833  which extends from the through portion  831  in a direction vertical to the first extending portion  832 . 
     Meanwhile, a connecting portion  834  formed at the first extending portion  832  of each of the first main link  83   a  and the second main link  83   b  may be formed to be overlapped with each other. An extending portion hole  834   b  and an extending portion protrusion  834   a  which are rotatably coupled to each other are formed at the first extending portions  832 , and thus the first main link  83   a  and the second main link  83   b  may be interlocked with each other. 
     Also, an extending portion inclined surface  834   c  corresponding to the transmission member inclined portion  821  is formed at one end of the first extending portion  832 , i.e., one side thereof which is in contact with the transmission member  82 . The extending portion inclined surface  834   c  is maintained in a contacting state with the transmission member inclined portion  821 , and the transmission member inclined portion  821  is vertically moved along the extending portion inclined surface  834   c  according to the vertical movement of the transmission member  82 , and thus the first extending portion  832  may be moved forward and backward. The first main link  83   a  and the second main link  83   b  may be rotated according to the forward and backward movement of the first extending portion  832 . 
     The sub-link  84  may be rotatably coupled to an end of the second extending portion  833 . That is, the first sub-link  84   a  and the second sub-link  84   b  are coupled to ends of the pair of second extending portions  833 , respectively. And link holes  833   a  may be formed at the ends of the second extending portions  833 , and link protrusions  841   a  which are coupled into the link holes  833   a  may be formed at the first sub-link  84   a  and the second sub-link  84   b . Therefore, when the main link  83  is rotated, the sub-link  84  may be interlocked therewith. 
     A link guide  423  may be formed at the cover base  42 . The link guide  423  is formed at a position corresponding to that of each of the first sub-link  84   a  and the second sub-link  84   b , and a space in which the first sub-link  84   a  and the second sub-link  84   b  are accommodated is formed therein. The link guide  423  may be formed in the form of one pair of ribs and may guide the sub-link  84  to be movable while the sub-link  84  is located therebetween. 
     Each of the first sub-link  84   a  and the second sub-link  84   b  may include a third extending portion  841  which is accommodated in the link guide  423  and a fourth extending portion  842  which is vertically bent from the third extending portion  841 . And the cover restricting protrusion  843  which protrudes laterally may be formed at the third extending portion  841 . 
     An inclined surface  843   a  may be formed at a side surface of the cover restricting protrusion  843 . The inclined surface  843   a  may be formed so that a width thereof is increased from a lower end thereof toward an upper end thereof. Therefore, while the cover member  40  is closed, the inclined surface  843   a  of the cover restricting protrusion  843  may be inserted inward while being in contact with a side wall of the upper decoration  37  and then may protrude outward to be restricted when reaching a protrusion restricting hole  376  (in  FIG. 28 ) of the upper decoration  37 . To this end, an upper end of the cover restricting protrusion  843  may be formed in a flat shape. 
     And a protrusion entrance  424  through which the cover restricting protrusion  843  is inserted and withdrawn may be formed at a side surface of the cover base  42  corresponding to a position of the link guide  423 . When the second sub-link  84   b  is horizontally moved, the cover restricting protrusion  843  may be inserted and withdrawn through the protrusion entrance  424 . The cover restricting protrusion  843  is caught and restricted by the protrusion restricting hole  376  (in  FIG. 28 ) of the body part  30  while protruding from the protrusion entrance  424  and allows the cover member  40  to be maintained in a closed state. 
     Meanwhile, although not illustrated, an elastic member such as a spring may be provided at at least one of the push member  81 , the main link  83  and the sub-link  84 . Due to the elastic member, the cover restricting protrusion  843  may be maintained in a protruding state while the external force by a user&#39;s operation is not provided. 
       FIG. 24  is a perspective view illustrating a state before the locking assembly is operated. And  FIG. 54  is a cross-sectional view illustrating the state before the locking assembly is operated. 
     As illustrated in the drawings, while the push member  81  is not operated by the user, the transmission member  82  may be maintained in the contacting state with the main link  83 . At this point, the transmission member  82  is located at the uppermost side, and the transmission member inclined portion  821  is in a contacting state with the extending portion inclined surface  834   c.    
     Also, a guide inclined surface  822  may be further formed at a lower end of the transmission member  82 . The guide inclined surface  822  may be in contact with a transmission member guide  412   a  formed at the cover base  42 . That is, when the transmission member  82  is moved downward, the transmission member  82  allows the guide inclined surface  822  to be moved along the transmission member guide  412   a . At this point, the transmission member guide  412   a  extends to vertically cross the main link  83 , and thus the transmission member  82  may be moved in a direction which crosses the main link  83  when being moved downward and may operate the main link  83 . 
     At this point, the first main link  83   a  and the second main link  83   b  are maintained on the same extension line, and the main link  83  is maintained in a state in which the external force is not applied. The cover restricting protrusion  843  is maintained in a caught and restricted state by the protrusion restricting hole  376  (in  FIG. 28 ) of the body part  30  while protruding from the protrusion entrance  424  and thus allows the cover member  40  to be maintained in the closed state. 
     In this state, the user pushes the push member  81  to open the cover member  40 . Due to the operation of the push member  81 , the main link  83  and the sub-link  84  are interlocked with each other, and the cover member  40  is in an openable state. 
       FIG. 26  is a perspective view illustrating an operating state of the locking assembly. And  FIG. 27  is a cross-sectional view illustrating the operating state of the locking assembly. 
     As illustrated in the drawings, when the user pushes the push member  81 , the transmission member  82  is moved downward. At this point, the transmission member  82  may be rotated by a rotating shaft  811   a  formed on the transmission member installing portion  811  and may vertically push the main link  83 . At this point, to prevent the transmission member  82  from being excessively rotated or separated, one pair of separation preventing protrusions  824  may protrude from an upper end of the transmission member  82  to be spaced apart from each other at a predetermined distance, and a separation preventing rib  812  of the push member  81  may be disposed between the separation preventing protrusions  824 . 
     When the transmission member  82  is moved downward while the transmission member inclined portion  821  is in contact with the extending portion inclined surface  834   c , the extending portion inclined surface  834   c  performs a relative motion along the transmission member inclined portion  821 . That is, the first extending portion  832  is pushed up forward. At this point, since the first main link  83   a  and the second main link  83   b  are connected with each other, the first extending portion  832  is also moved forward together. 
     When the first extending portion  832  is moved forward, the main link  83  is rotated using the through portion  831  as an axis, and the second extending portions  833  are moved in a direction which become closer to each other. Therefore, the first sub-link  84   a  and the second sub-link  84   b  which are connected to the second extending portion  833  are horizontally moved inward. Due to the horizontal movement of the sub-link  84 , the cover restricting protrusion  843  formed at the sub-link  84  is also moved horizontally toward an inside of the protrusion entrance  424 . 
     In this state, since the cover restricting protrusion  843  is located inside the cover member  40 , the restriction by the protrusion restricting hole  376  (in  FIG. 28 ) of the body part  30  may be released. Therefore, the user may rotate the cover member  40  while gripping the grip portion  41  of the cover member  40  and may open an inside of the body part  30  or may separate the dust container  50  from the body part  30 . 
     Meanwhile, as illustrated in  FIG. 26 , a display  45  for displaying an operating state of the vacuum cleaner  1  may be provided at the cover member  40 . The display  45  may be formed to display information on an upper surface of the cover member  40  and may be disposed at a lateral side of the grip portion  41  so that the user may easily check a state of the vacuum cleaner  1  from an upper side while using the vacuum cleaner  1 . 
     The display  45  may be formed in various types such as a liquid crystal display, a combination of a plurality of LEDs and a seven-segment and may be formed to allow the information to be visible. The display  45  may be defined as a single configuration for outputting an image and may also be defined to include a display PCB  451  on which the display  45  is mounted. 
     The display  45  may be installed on the cover base  42  and may be formed to be shielded by the outer cover  43 . At this point, the whole or a part of the outer cover  43  may be formed to transmit light. Therefore, when the display  45  shielded by the outer cover  43  is operated, the information may be displayed to an outside through the outer cover  43 . 
     To this end, the entire outer cover  43  may be formed of a material which transmits the light. Otherwise, only a part thereof corresponding to the display  45  may be formed to transmit the light. Of course, an opening may be formed at the outer cover  43 , and the display  45  may be installed at the opening to be directly exposed to the outside or to be shielded by a separate transparent cover. 
     The display  45  may be installed and fixed to an upper surface of the cover base  42 . The display  45  may be connected to the main PCB  301  by a display cable  452 . Therefore, the display  45  may be driven by the electric power and the information transmitted from the main PCB  301 . 
     The display  45  may display the operating state of the vacuum cleaner  1  and may be formed to display, for example, a battery residual value of the battery unit  38  or an operable time with the current battery residual value. Also, the display  45  may display an abnormal operation state of the vacuum cleaner  1  or information about a replacement of the dust container  50  or the like. 
       FIG. 28  is a plan view of the cover member in which the display according to the embodiment is in an OFF state. And  FIG. 29  is a plan view of the cover member in which the display according to the embodiment is in an ON state. 
     Referring to the drawings, while the vacuum cleaner  1  is not operated, the display  45  is in an OFF state. In this state, as illustrated in  FIG. 28 , the display  45  is covered by the outer cover  43  and is thus invisible from the outside, and only an exterior of the outer cover  43  may be exposed. 
     When an operation of the vacuum cleaner  1  starts by an user&#39;s operation, the display  45  is turned on, and an image output on the display  45  may be visible to the outside through the outer cover  43 . That is, when the display  45  becomes bright due to an output of the image on the display  45 , light of the display  45  may pass through the outer cover  43  and thus the image on the display  45  may be visible to the outside. 
     The display  45  may display a state of the battery unit  38  of the vacuum cleaner  1  in the form of a picture. The user may check the state of the battery unit  38  through the image output on the display  45  and may decide charging of the battery unit  38  or performing of a cleaning operation. 
     Of course, the display  45  may display a variety of information other than the charging state of the battery unit  38 . 
       FIG. 30  is a perspective view illustrating a state in which the cover member is opened. And  FIG. 31  is an exploded perspective view illustrating a coupling structure of a link assembly according to the embodiment of the present invention. 
     As illustrated in the drawings, the cover member coupling portion  421  is formed at the rear end of the cover member  40 , and the cover member coupling portion  421  may be coupled into a cover member coupling hole  372  formed at the upper decoration  37  of the body part  30 . When the cover member coupling portion  421  is coupled into the cover member coupling hole  372 , the cover member  40  may be rotatably installed. The cover member  40  may be rotated using the cover member coupling portion  421  as an axis and may open and close the inside of the body part  30 . 
     The cover member  40  may also be opened and closed when the dust container  50  is separated. When the cover member  40  is maintained in an opened state during such an operation, the dust container  50  may be more easily separated. 
     In particular, since a structure at which the fitting portion  241  of the suction hose  24  is installed is provided at a front end of the cover member  40 , the cover member  40  is structurally naturally closed due to a weight of the suction hose  24 . 
     In this state, a link assembly  90  which connects the rear end of the cover member  40  with an inside of the upper decoration  37  may be provided to maintain the opened state of the cover member  40 . 
     The link assembly  90  may include a rotating link  91  which is installed at the cover member coupling portion  421 , a slider  92  which is coupled to the rotating link  91  to be slidably moved when the rotating link  91  is rotated and a spring  93  which elastically supports the slider  92 . 
     The rotating link  91  may include a rotating portion  911  which is rotatably installed at the cover member coupling portion  421  and supporting portions  912  which extend from both side ends of the rotating portion  911  to be spaced apart from each other. 
     The rotating portion  911  may be inserted between one pair of the cover member coupling portions  421 , and a rotating shaft  911   a  which laterally protrudes from each of both side ends of the rotating portion  911  may be inserted into a rotating shaft hole  421   a  formed at the cover member coupling portion  421 . Therefore, the rotating link  91  may be rotatable about the rotating shaft  911   a  and may be rotated when the cover member  40  is opened and closed. 
     The supporting portions  912  may extend while being spaced apart from each other, and a space portion  913  in which an end of the slider  92  is accommodated may be formed between the pair of supporting portions  912 . A slider fixing portion  912   a  and a supporting protrusion  912   b  may be formed at ends of the pair of the supporting portions  912 , respectively. 
     The slider fixing portion  912   a  protrudes toward the opposite end of the supporting portion  912  and is located inside the space portion  913 . The slider fixing portion  912   a  may be inserted into a slider fixing groove  921  of the slider  92 . And the slider fixing portion  912   a  may be a rotating shaft of the slider  92  or a rotating shaft of the rotating link  91 . 
     The supporting protrusion  912   b  is formed to protrude laterally from the end of the supporting portion  912  along an outer surface thereof. The supporting protrusion  912   b  may protrude outward and may be selectively caught and restricted by an interference protrusion  375   a  inside a link assembly accommodating portion  373  which will be described below when the cover member  40  is opened and closed. 
     Meanwhile, a supporting slit  912   c  may be formed at each of the ends of the supporting portions  912 . The supporting slit  912   c  enables the ends of the supporting portions  912  to be easily elastically deformed when the supporting protrusion  912   b  and the interference protrusion  375   a  interfere with each other. 
     A rear end of the slider  92  is disposed inside the space portion  913 , and a front end thereof may be accommodated in the link assembly accommodating portion  373  formed at the body part  30 . 
     The slider fixing groove  921  which is recessed inward may be formed at each of left and right side surfaces of the slider  92 . The slider fixing groove  921  is formed to be opened backward and formed to accommodate the slider fixing portion  912   a  which is formed in a shaft shape. And the slider  92  may be interlocked with the rotating link  91 . 
     And a slider guide  922  may be formed at a front of the slider fixing groove  921 . The slider guide  922  may extend from an end of the slider fixing groove  921  to an end of the slider  92 . The slider guide  922  has one pair of ribs respectively provided at both of left and right sides thereof, accommodates a guide rib  374   a  which will be described below and enables the slider  92  to be smoothly moved. 
     And a spring hole  923  which is recessed inward is formed at a rear surface of the slider  92 . The spring  93  may be inserted and installed into the spring hole  923 , may be compressed or elastically deformed according to movement of the slider  92  and may provide an elastic force to the slider  92 . 
     Meanwhile, the link assembly accommodating portion  373  may be formed at the upper decoration  37 . The link assembly accommodating portion  373  may be provided at the upper surface of the body part  30  and may be formed to have a size which enables the slider  92  and the rotating link  91  to be inserted and withdrawn. 
     Specifically, a slider accommodating portion  374  in which the slider  92  is accommodated may be formed at a center inside the link assembly accommodating portion  373 . And the guide rib  374   a  is formed to protrude from each of both wall surfaces of the slider accommodating portion  374 . The guide rib  374   a  may protrude to be inserted into the slider guide  922  and may be formed to extend in an inserting direction of the slider  92 . Therefore, the guide rib  374   a  and the slider guide  922  prevent the slider  92  from being separated and enable the slider  92  to be slidingly moved along a set route when the slider  92  is slidingly moved forward and backward. 
     A link accommodating portion  375  in which the rotating link  91  is selectively inserted may be further formed at the link assembly accommodating portion  373 . The link accommodating portion  375  may be located at a rear of the slider accommodating portion  374 , may provide a space in which the rotating link  91  is accommodated and may be opened backward. 
     The interference protrusion  375   a  which protrudes inward may be formed to protrude from an inner wall surface of the link accommodating portion  375 . The interference protrusion  375   a  may support the supporting protrusion  912   b  formed at the supporting portion  912  while the cover member  40  is opened and the rotating link  91  is withdrawn and may allow the rotating link  91  to be maintained in a withdrawable state. 
     At this point, the interference protrusion  375   a  may protrude to be inclined at a predetermined angle and thus may allow the rotating link  91  to be supported in an inclined state when the supporting protrusion  912   b  is supported. That is, when the interference protrusion  375   a  supports the supporting protrusion  912   b , the cover member  40  may be allowed to be maintained in the inclined state and thus may be maintained in the opened state. 
     And an opened and closed state of the cover member  40  may be determined by that the supporting protrusion  912   b  is supported by the interference protrusion  375   a  or moved over the interference protrusion  375   a  according to the user&#39;s rotating operation of the cover member  40 . 
       FIG. 32  is a cross-sectional view illustrating a state of the link assembly while the cover member is closed. 
     Referring to the drawing, a state of the link assembly  90  while the cover member  40  is in a closed state will be described. While the cover member  40  is in the closed state, the cover member  40  shields the opened upper surface of the body part  30 . A lower end of the cover member  40  is in contact with a lower end of the upper decoration  37 , and the link assembly  90  of the cover member  40  is in a restricted state by the upper decoration  37 . 
     And the slider  92  and the rotating link  91  are in an inserted state inside the link assembly accommodating portion  373  of the upper decoration  37 , and the rotating link  91  is maintained in a horizontal state with the slider  92  or on the same extension line as that of the slider  92 . 
     At this point, since the slider  92  is completely inserted into the slider accommodating portion  374 , the spring  93  is in a maximally compressed state. Therefore, when the user releases the restriction of the locking assembly  80  to open the cover member  40 , the slider  92  may be pushed by the elastic force of the spring  93 , and thus a force may be naturally applied in a rotating direction of the cover member  40 . 
     In this state, the user pushes the push member  81  and operates the locking assembly  80  to open the cover member  40 , and thus the restriction of the cover member  40  and the body part  30  is released and the cover member  40  is in an openable state. And the user may grip the grip portion  41 , may rotate the cover member  40  and then may open the cover member  40 . 
       FIG. 33  is a cross-sectional view illustrating the state of the link assembly while the cover member is opened. And  FIG. 34  is an enlarged view of an A portion in  FIG. 30 . 
     Referring to the drawings, the state of the link assembly  90  while the cover member  40  is in the opened state will be described. When the cover member  40  is opened by the user, the cover member  40  may be clockwise rotated using the cover member coupling portion  421  as an axis and thus may be opened. 
     At this point, the rotating link  91  which is rotatably connected to the cover member coupling portion  421  is also rotated together, and the slider  92  connected to the rotating link  91  is slidingly moved backward (to a right side in  FIG. 33 ) by guiding of the slider guide  922  and the guide rib  374   a . When the slider  92  is moved, the spring  93  which elastically supports the slider  92  provides the elastic force, and thus the slider  92  may be more easily moved. 
     And the rotating link  91  is horizontally moved along the slider  92  to pull and withdraw the slider  92  and simultaneously rotated counterclockwise. At this point, the supporting protrusion  912   b  of the rotating link  91  is in contact with the interference protrusion  375   a  on the link assembly accommodating portion  373 . 
     When the cover member  40  is completely opened by the user, the rotating link  91  may be in a state illustrated in  FIGS. 33 and 34 . At this point, the supporting protrusion  912   b  may pass the interference protrusion  375   a  by the user&#39;s rotating operation of the cover member  40 , and the supporting portion  912  is elastically deformed so that the supporting protrusion  912   b  is moved over the interference protrusion  375   a.    
     In this state, the opening of the cover member  40  may be stopped. Even when the user releases the grip portion  41 , the supporting protrusion  912   b  is in contact with the interference protrusion  375   a , and thus the rotating link  91  may be maintained at the set angle. Therefore, the cover member  40  may maintain the opened state at the set angle. While the cover member  40  is opened, the user may separate or install the dust container  50  or may perform any necessary operations in the body part  30 . 
     Meanwhile, in the state illustrated in  FIGS. 33 and 34 , when it is intended to close the cover member  40  again, the user may grip the grip portion  41  and may push the cover member  40 , and thus the cover member  40  may be closed while being rotated counterclockwise. 
     At this point, at a moment when the counterclockwise rotation of the cover member  40  starts, the supporting protrusion  912   b  may be moved over the interference protrusion  375   a  by a force applied by the user, and the supporting portion  912  may be elastically deformed so that the supporting protrusion  912   b  is easily moved. 
     The cover member  40  is in a state illustrated in  FIG. 32  when being completely rotated and closed. When the cover member  40  is closed, the cover restricting protrusion  843  of the locking assembly  80  is inserted and restricted inside the protrusion restricting hole  376 , and the cover member  40  may be maintained in the closed state. 
     Meanwhile, the display cable  452  may be guided into the body part  30  through a cover member coupling portion  46  which extends backward from a rear end of the cover member  40 . The display cable  452  is guided along an inside of the cover member coupling portion  46  not to be exposed to the outside. And since the display cable  452  is guided into the body part  30  through a rear end of the cover member coupling portion  46  which is a rotating center of the cover member  40 , it is possible to prevent the display cable  452  from being exposed and also to prevent the display cable  452  from being damaged although an opening and closing operation of the cover member  40  is continuously performed. 
       FIG. 35  is a partial perspective view illustrating a structure of the cover member coupling portion and an arrangement of the display cable according to the embodiment of the present invention. 
     A structure of the cover member coupling portion  46  will be described in detail with reference to the drawing. One pair of cover member coupling portions  46  may extend backward from both of left and right sides, may be inserted into the cleaner body  10  and may be rotatably coupled. 
     The cover member coupling portion  46  may include a bent portion  461  which extends downward from the rear end of the cover base  42  in a predetermined length and an extending portion  462  which extends backward from an end of the bent portion  461 . 
     A bent portion hole  463  in which the rotating shaft  911   a  of the rotating portion  911  of the rotating link  91  is inserted may be formed at an inner surface of each of the bent portions  461  provided at both of left and right sides. Therefore, one end of the rotating link  91  may be disposed at a space between one pair of bent portions  461  and may be rotatably coupled to the inner surface of the bent portion  461 . 
     And a cover rotating shaft  464  may be formed at both side ends of the extending portion  462 . The cover rotating shaft  464  may protrude outward from an outer surface of the extending portion  462  and may be shaft-coupled to the cover member coupling hole  372  of the upper decoration  37 . Therefore, the cover member  40  may be rotated about an end of the cover member coupling portion  46 , i.e., the cover rotating shaft  464  and may be opened and closed by rotation. 
     Meanwhile, the cover member coupling portion  46  has a guide space  465  recessed therein. The guide space  465  may be formed from a front end of the cover member coupling portion  46  to the rear end thereof. And a cable hole  466  may be formed at a rear end of the guide space  465 , i.e., the rear end of the cover member coupling portion  46 . 
     Therefore, while the cover member  40  is rotatably coupled to the upper decoration  37 , the cover member coupling portion  46  is inserted into a decoration opening  377  of the upper decoration  37 . And in this state, the cover member coupling portion  46  may allow an inside of the cover member  40  and an inside of the body part  30  to be in communication with each other. 
     The display cable  452  may be disposed at the guide space  465  of the cover member coupling portion  46 . The display cable  452  may be guided along the cover member coupling portion  46 , may pass through the cable hole  466  and then may be introduced into the body part  30 . And the display cable  452  introduced into the body part  30  may be connected to the main PCB  301 . Of course, the display cable  452  may be connected to another PCB or an element for power supply in the body part  30  rather than the main PCB  301 . 
     Meanwhile, a plurality of reinforcing portions  467  may be further formed in the guide space  465 . Each of the plurality of reinforcing portions  467  may be formed in a rib shape, and the plurality of reinforcing portions  467  may be formed in an extension direction of the cover member coupling portion  46  and a direction intersecting therewith. 
     And a stopper  47  may be formed between a space between the cover member coupling portions  46  provided at both of the left and right sides. The stopper  47  may be be in contact with an outer surface of the upper decoration  37  while the cover member  40  is completely opened when a rotating operation is performed to open the cover member  40 , may restrict the cover member  40  from being excessively rotated and thus may prevent the rotating link  91  from being broken or separated. 
       FIG. 36  is a view illustrating a cable arrangement state in the cover base of the cover member. 
     As illustrated in the drawing, the locking assembly  80  may be disposed at the cover base  42  of the cover member  40 . The locking assembly  80  may include the push member  81 , the transmission member  82 , the main link  83  and the sub-link  84 . At this point, the push member  81  may be installed and fixed to the grip portion  41 , and the remaining configurations of the locking assembly  80  except the grip portion  41  may be disposed to interact with each other on the cover base  42 . 
     And the plurality of obstacle detecting members  44  may be disposed at the front surface of the cover member  40 . The obstacle detecting members  44  serve to check an obstacle while the cleaner body  10  is travelled and may be disposed along the front surface of the cover base  42 . 
     The plurality of obstacle detecting members  44  may be provided at both of left and right sides based on a center of the front surface of the cover base  42 , i.e., the connector  401 . That is, two obstacle detecting members  44  may be provided at each of the left and right sides based on the center of the cover base  42 . The front surface of the cover member  40  may be formed to be rounded, and the plurality of obstacle detecting members  44  may be formed to emit light rays or ultrasonic waves for detecting the obstacle in a direction vertical to a tangent line of the front surface of the cover member  40 . The obstacle detecting member  44  may include a vision camera or a laser sensor, an optical sensor or an ultrasonic sensor which may detect the obstacle located in a travel direction of the vacuum cleaner  1  or at an adjacent position thereof. 
     The obstacle detecting members  44  may include a plurality of sensor substrates  442  for an operation of a sensor or a detecting device, and a detecting member cable  443  may be connected to each of the plurality of sensor substrates  442 . Supplying of electric power and transmitting of a detected signal for operating of the obstacle detecting member  44  may be performed through the detecting member cable  443 . 
     A plurality of detecting member cables  443  may be provided to connect the plurality of sensor substrates  442  and may be guided along an inner circumference of the cover base  42  to a rear side at which the cover member coupling portion  46  is disposed. At this point, the plurality of detecting member cables  443  may be fastened into a bundle by a cable guide member  443   a  such as a contraction tube, a tape or a cable tie and may pass through the cover member coupling portion  46  in this state. That is, the cable guide member  443   a  may be disposed at a section which passes through at least the cover member coupling portion  46 . 
     At this point, the detecting member cables  443  may be guided into the body part  30  through one (left one in  FIG. 36 ) of the pair of cover member coupling portions  46  which is disposed at the rear end of the cover base  42 . Therefore, the detecting member cables  443  may be prevented from being damaged although the cover member  40  is continuously operated to be opened and may be easily disposed in the body part  30  by passing through the cover member coupling portion  46 . 
     Meanwhile, the display  45  and the display PCB  451  may be disposed on the upper surface of the cover base  42 . Of course, the display  45  and the display PCB  451  may be installed and fixed to a rear surface of the outer cover  43  of the cover member  40 . 
     The display PCB  451  may be installed and fixed to the upper surface of the cover base  42 , and the display  45  may be installed on the display PCB  451 . The display  45  may include a light guide  45   a  which is in contact with the rear surface of the outer cover  43 , and a plurality of LED holes  45   b  may be installed at the light guide  45   a . And LEDs (not shown) may be accommodated in the plurality of LED holes  45   b  and may be independently turned on and off. Therefore, the battery residual value of the battery unit  38  may be displayed by light which is guided by the LED holes  45   b  and transmitted to the outer cover  43 . 
     Meanwhile, the display cable  452  may be installed at the display PCB  451 . The display cable  452  may be configured with a plurality of wires and may be fastened into a bundle by a cable guide member  452   a  which is the same as the cable guide member  443   a . The cable guide member  452   a  may be disposed at a section which passes through at least the cover member coupling portion  46 . And the display cable  452  may be guided into the body part  30  through the cover member coupling portion  46 . At this point, the display cable  452  may be guided through the other one (right one in  FIG. 36 ) of the pair of cover member coupling portions  46  rather than the one by which the detecting member cable  443  is guided. That is, the detecting member cable  443  and the display cable  452  may be separately guided by the pair of cover member coupling portions  46  which are provided at the rear end of the cover base  42 . 
       FIG. 37  is a view illustrating a coupling structure of the wire to the cleaner body. 
     As illustrated in the drawing, the detecting member cable  443  and the display cable  452  may be guided into the body part  30  through the pair of cover member coupling portions  46  and may be guided without exposing the cables to the outside even when the cover member  40  is operated to be opened and closed by the rotation. 
     The detecting member cable  443  introduced into the body part  30  may be guided to one side of the body part  30  at which the moving wheel  60  is installed. And the detecting member cable  443  may be connected to the detecting part  306  installed at the body part  30 . Therefore, an obstacle detecting signal detected by the obstacle detecting member  44  may be transmitted to and processed in the detecting part  306 , and the travelling of the cleaner body  10  may also be controlled by controlling the driving of the moving wheel  60 . 
     At this point, connectors  443   b  which are connectable to each other may be provided at an end of the detecting member cable  443  and one side of the detecting part  306 , and thus the detecting member cable  443  and the detecting part  306  may be connected through a simple operation which connects the connectors  443   b.    
     And the display cable  452  introduced into the body part  30  may be connected to the battery unit  38  installed on the lower frame  33  while being guided into the body part  30  or may be connected to another PCB or a device which may provide the information about the battery residual value of the battery unit  38 . 
     That is, the information about the battery residual value of the battery unit  38  and the electric power which are transmitted in a connected state of the display cable  452  are transmitted to the display  45 , and thus operating information of the battery unit  38  may be transmitted to the user. 
     Of course, a connector  452   b  may also be provided at an end of the display cable  452  to be easily coupled to a target object. 
       FIG. 38  is a perspective view of the dust container. And  FIG. 39  is an exploded perspective view of the dust container. 
     As illustrated in the drawings, the dust container  50  serves to separate and store the dust in the air introduced through the suction unit  20 , and the suctioned air may be filtered, in turn, through a first cyclone  54  and a second cyclone  55  which separate the dust from the air in a cyclone method, then may be discharged through the discharge port  512  and may be introduced inside the body part  30 . 
     The dust container  50  may include a transparent case  53  which is generally formed in a cylindrical shape, an upper cover  51  which opens and closes an opened upper end of the transparent case  53  and a lower cover  52  which opens and closes an opened lower end of the transparent case  53 . And the first cyclone  54 , the second cyclone  55 , an inner case  544 , the dust compressing unit  56 , a guide unit  543  and so on may be accommodated in the transparent case  53 . 
     More specifically, the upper cover  51  forms an exterior of an upper surface of the dust container  50  and is formed to be shielded by the cover member  40  while being installed at the body part  30 . And the suction port  511  is formed at a front of the dust container  50 . The suction port  511  is formed to be in communication with the connector  401  while the cover member  40  is closed, such that the air containing the dust which is suctioned through the suction unit  20  is introduced inside the dust container  50 . 
     And although not illustrated in detail, a passage guide  518  is provided inside the upper cover  51  so that the air introduced through the suction port  511  is guided along an outer circumference thereof and flows downward along an inner surface of the transparent case  53 . At this point, the flowing air may be discharged in one direction along the inner surface of the transparent case  53  by the upper cover  51  and may be rotated along a circumference of the transparent case  53  while being rotated spirally. 
     The discharge port  512  is formed at a rear of the upper cover  51  which faces the suction port  511 . The discharge port  512  is an outlet through which the air from which the dust is filtered while passing through the first cyclone  54  and the second cyclone  55  inside the dust container  50  is discharged to an outside of the dust container  50 . The air in the dust container  50  may be guided to the discharge port  512  by the passage guide  518  provided inside the upper cover  52 . And the discharge port  512  may be in contact with the filter hole  361   a  of the prefilter assembly  36  and may be introduced into the body part  30  through the filter hole  361   a.    
     Meanwhile, a dust container handle  513  which is withdrawable upward may be provided at an upper surface of the upper cover  52 . The dust container handle  513  may include a handle portion  513   a  which extends transversely to be gripped by the user and a side extending portion  513   b  which extends vertically from each of both ends of the handle portion  513   a . The side extending portion  513   b  may be inserted inside the upper cover  52 . At this point, the handle portion  513   a  may be in close contact with the upper surface of the upper cover  52 . While the dust container  50  is installed, the dust container handle  513  is maintained in an inserted state due to its own weight and does not interfere with the cover member  40  when the cover member  40  is opened and closed. 
     And a cover inserting portion  514  which extends downward along a circumference of the upper cover  51  is formed at a lower end of the upper cover  52 , and an upper gasket  515  is provided at the upper cover inserting portion  514  to seal the transparent case  53  while the upper cover  51  is installed at the transparent case  53 . And the upper cover  51  is maintained in a coupled state to the transparent case  53  by the upper locker  57  which will be described below. 
     The lower cover  52  may be formed in a corresponding shape to shield an opened lower surface of the transparent case  53 . A lower gasket  523  is provided at a circumference of the lower cover  52  to be in close contact with the transparent case  53  while the lower cover  52  is closed, thereby sealing between the transparent case  53  and the lower cover  52 . 
     And a transmission gear  59  may be provided at a center of the lower cover  52 . The transmission gear  59  connects the compression motor assembly  323  with the dust compressing unit  56  and transmits power so that the dust compressing unit  56  is driven by driving of the compression motor assembly  323 . 
     One side of the lower cover  52  may be shaft-coupled to the lower end of the transparent case  53 , and thus the lower cover  52  may be opened and closed by rotation to remove the dust. And the lower cover  52  is maintained in the coupled state to the transparent case  53  by a lower locker  58  which will be described below. Therefore, the lower cover  52  may be selectively opened and closed by an operation of the lower locker  58 . 
     And the first cyclone  54  is formed to filter the dust and foreign substances from the introduced air and also to allow the air, from which the dust and the foreign substances are filtered, to be introduced inward. The first cyclone  54  may include a cylindrical strainer  541  which has a plurality of holes and a dust filter  542  which is provided outside or inside the strainer  541 . 
     Therefore, the air introduced along the transparent case  53  may be filtered by the filter unit  39 , and the filtered air may be introduced inside the strainer  541 , then may fall downward, may pass through the guide unit  543  and may be stored in a first dust collecting space  501  formed at a lower portion of the dust container  50 . Meanwhile, the fine dust which is not filtered by the filter unit  39  may pass through the filter unit  39  and may be introduced into the second cyclone  55  to be separated therein. 
     The second cyclone  55  may include a plurality of casings  551  which are accommodated inside the strainer  541  and formed in a conical shape which becomes narrower downward. An upper end and a lower end of each of the casings  551  may be opened so that the fine dust is separated and discharged downward while the suctioned air is rotated inside the casing  551  and the air from which the fine dust is separated flows upward. The fine dust separated by the casing  551  may be stored in a second dust collecting space  502  which is separated from the first dust collecting space  501 . 
     An inlet port  551   a  through which the air is introduced may be formed at an upper portion of the casing  551 . And a guide vane  552  formed in a spiral shape along an inner circumference of the casing  551  is provided at the inlet port  551   a  to generate a rotating flow of the introduced air. 
     A vortex finder  553  at which an outlet port  553   a  for discharging the air separated from the fine dust in the casing  551  is formed is provided at the upper portion of the casing  551 . The vortex finder  553  shields an opened upper surface of the casing  551 , and the outlet port  553   a  may be disposed at a center of the casing  551 . And a cyclone cover  554  which forms an upper surface of the second cyclone  55  is provided. The cyclone cover  554  is formed to be in communication with the outlet ports  553   a  of a plurality of vortex finders  553 . The vortex finder  553  and the cyclone cover  554  may be formed integrally, and the guide vane  552  may also be integrally formed with the vortex finder  553 . And the cyclone cover  554  may be coupled and fixed to the upper cover  51  or may be fixed to the upper end of the transparent case  53 . 
     The air which is discharged upward through the outlet port  553   a  of the vortex finder  553  may flow through the upper cover  52 , may flow along an inside of the body part  30  through the discharge port  512  and then may be discharged outside the body part  30  through the rear cover  314 . 
     The inner case  544  may support the first cyclone  54  and the second cyclone  55  and may also divide the first dust collecting space  501  and the second dust collecting space  502 . The inner case  544  may be formed in a cylindrical shape of which an upper surface and a lower surface are opened, and a diameter of a lower portion thereof may be formed smaller than that of an upper portion thereof. Therefore, a space between the inner case  544  and the transparent case  53  may be defined as the first dust collecting space  501  in which the dust separated by the first cyclone  54  is stored, and a space inside the inner case  544  may be defined as the second dust collecting space  502  in which the dust separated by the second cyclone  55  is stored. 
     An upper portion of the inner case  544  is formed so that the diameter thereof becomes narrower downward and also formed to accommodate a lower portion of the casing  551 . And the guide unit  543  may be provided at the upper portion of the inner case  544 . 
     The guide unit  543  serves to enable the air separated from the dust by the first cyclone  54  to be moved downward while being spirally rotated and may include a guide base  543   a  which is installed outside the inner case  544  and a vane  543   b  which protrudes from the guide base  543   a.    
     The guide base  543   a  may be formed in a cylindrical shape and may be disposed outside the inner case  544 . The guide base  543   a  may be coupled to the inner case  544  or may be integrally formed with the inner case  544 . And the guide base  543   a  may be installed outside the inner case  544  to be rotatable. And the guide base  543   a  may be integrally formed with the dust compressing unit  56 . 
     The vane  543   b  may be formed along a circumference of an outer surface of the base  31  and may be formed to be inclined such that a flowing direction of the dust and the air is forced spirally. At this point, a plurality of vanes  543   b  may be disposed so that adjacent vanes  543   b  are at least partially overlapped with each other when being seen from an upper side, and the dust and the air may flow downward through a passage formed between the adjacent vanes  543   b.    
     The dust guided through the vane  543   b  may pass through the vane  543   b  and then may be stored in the first dust collecting space  501 . And the dust stored in the first dust collecting space  501  may not flow back in a reverse direction but may be stayed in the first dust collecting space  501  due to a structure of the vanes  543   b  which are formed to be inclined and disposed to be vertically overlapped with each other. 
     In particular, a backflow preventing portion  531  is formed at the inner surface of the transparent case  53  corresponding to an area of the vane  543   b . The backflow preventing portion  531  may be disposed along an inner circumference of the transparent case  53  at a predetermined interval. The backflow preventing portion  531  may be formed in a rib shape which extends in a direction which crosses the vane  543   b.    
     Therefore, some of the dust which flows back in the first dust collecting space  501  collides with the backflow preventing portion  531  during a process in which the vane  543   b  is rotated. Therefore, the dust does not pass through the vane  543   b , falls downward again and then is primarily compressed. That is, some of the dust which flows upward is continuously and repeatedly falls downward by the vane  543   b  and the backflow preventing portion  531  and then compressed while colliding with another dust. 
     The dust compressing unit  56  is provided at a lower portion of the inner case  544  and formed to compress the dust stored inside the first dust collecting space  501  by rotation, thereby reducing a volume of the dust. 
     Specifically, the dust compressing unit  56  may include a rotating portion  561  and a pressing portion  562 . The rotating portion  561  is formed in a cylindrical shape and installed outside the inner case  544 . The rotating portion  561  may be independently rotated according to a coupling state with the inner case  544  and may be formed to be rotated along with the inner case  544 . Of course, the rotating portion  561  may also be rotated along with the guide unit  543  when being coupled to the guide unit  543 . 
     The pressing portion  562  may be formed to cross the first dust collecting space  501  from one side of the rotating portion  561  to the inner surface of the transparent case  53 . The pressing portion  562  may be formed in a plate shape corresponding to a cross section of the first dust collecting space  501  and may divide an inside of the first dust collecting space  501 . An inner wall (not shown) which extends inward to be overlapped with the pressing portion  562  may be formed inside the first dust collecting space  501 . The dust stored in the first dust collecting space  501  may be compressed between the pressing portion  562  and the inner wall by normal and reverse rotation of the pressing portion  562 . That is, the dust stored in the first dust collecting space  501  is secondarily compressed by the rotation of the pressing portion  562 . 
     A plurality of vent holes  562   a  may be formed at the pressing portion  562  to solve resistance of the air which may be generated when the pressing portion  562  is rotated and also to solve a pressure unbalance between spaces divided by the pressing portion  562 . And a decoration member  563  which is in contact with the inner surface of the transparent case  53  may be installed at an extending end of the pressing portion  562 . The decoration member  563  may be formed in a quadrangular shape which is in surface contact with the transparent case  53  and may shield between the pressing portion  562  and the transparent case  53 . And the decoration member  563  may be formed of a wear resistant material and may be formed of a lubricant material to allow smooth rotation of the pressing portion  562 . 
     Meanwhile, one pair of supporting ribs  532  may be formed at an outer surface of the transparent case  53 . The supporting ribs  532  may be formed to extend from an upper end of the transparent case  53  to a lower end thereof. And the supporting ribs  532  are in contact with both of left and right side ends of the opened front surface of the body part  30  when the dust container  50  is installed and guide the exact installing of the dust container  50 . 
       FIG. 40  is an exploded perspective view illustrating a coupling structure of the upper cover and the lower cover of the dust container when being seen from one side. And  FIG. 41  is a cross-sectional view illustrating a state in which the upper cover is opened. And  FIG. 42  is an exploded perspective view illustrating the coupling structure of the upper cover and the lower cover of the dust container when being seen from another side. And  FIG. 43  is a cross-sectional view illustrating a state in which the lower cover is opened. 
     As illustrated in the drawings, the upper cover  51  and the lower cover  52  may be respectively installed at the upper end and the lower end of the transparent case  53  to shield the transparent case  53 . 
     The upper cover  51  may be maintained in a restricted state to the transparent case  53  by the upper locker  57 . And when it is necessary to disassemble and clean or maintain internal elements of the dust container  50 , the upper cover  51  may be separated from the transparent case  53  by an operation of the upper locker  57 . 
     The upper locker  57  may be installed at an upper locker installing portion  533  formed at the upper end of the transparent case  53 . At this point, a locker rotating shaft  571  which protrudes laterally from each of both side surfaces of the upper locker  57  may be inserted and installed into a locker hole  533   a  of the upper locker installing portion  533 , and thus the upper locker  57  may be operated to be rotated. 
     And a locker spring  572  may be provided between the upper locker installing portion  533  and the upper locker  57  under the locker rotating shaft  571  and a lower portion of the upper locker  57  may be elastically supported by a spring installing portion  573  and a spring guide  533   b.    
     The upper locker  57  may extend further than the upper end of the transparent case  53 , and a hook portion  574  which protrudes in a hook shape may be formed at an extending end thereof. The hook portion  574  may be inserted into a hook restricting portion  516  of the upper cover  51  to be caught and restricted to each other while the upper cover  51  is installed. 
     An upper protrusion  517  may be formed at one side of the upper cover  51  which faces the hook restricting portion  516 , and an upper groove  534  in which the upper protrusion  517  is inserted is correspondingly formed at an upper end of the inner surface of the transparent case  53 . 
     Therefore, while the upper cover  51  is installed, one end of the upper cover  51  is fixed by coupling between the upper protrusion  517  and the upper groove  534 , and the other end of the upper cover  51  is fixed by the upper locker  57 , and thus the upper cover  51  may be maintained in an installed state. And to separate the upper cover  52 , the restriction of one end of the upper cover  51  is released by operating the upper locker  57 , and then the upper protrusion  517  and the upper groove  534  are separated from each other. 
     The lower cover  52  may be maintained in a closed state by the lower locker  58 , and the first dust collecting space  501  and the second dust collecting space  502  may be opened by opening the lower cover  52 , and thus the dust in the first dust collecting space  501  and the second dust collecting space  502  may be removed. 
     A lower cover shaft  521  is formed at one end of the lower cover  52 . The lower cover shaft  521  is rotatably coupled to a lower cover coupling portion  535  formed at the lower end of the transparent case  53 . Accordingly, when the lower cover  52  is opened and closed, the lower cover  52  is rotated about an axis of the lower cover  52 . 
     And the lower locker  58  is provided at the other end of the transparent case  53  corresponding to the lower cover coupling portion  535 . The lower locker  58  may be installed to be slidable vertically, and thus the lower cover  52  may be selectively restricted. 
     Specifically, a lower locker installing portion  536  is formed at the lower end of the transparent case  53  which faces the upper locker installing portion  533 . The lower locker installing portion  536  may be configured with one pair of protruding ribs, and a locker slot  536   a  which extends vertically is formed therein. 
     A case catching portion  537  is formed between the protruding ribs of the lower locker installing portion  536 . The case catching portion  537  protrudes from the lower end of the transparent case  53 , and a lower hook  522  of the lower cover  52  may be caught and restricted while the lower cover  52  is closed. 
     And the lower locker  58  is formed to be recessed, such that the lower locker installing portion  536  is accommodated therein, and a locker protrusion  581  which protrudes inward is formed at each of both sides of an inner surface of the lower locker  58  and inserted into the locker slot  536   a . Therefore, the lower locker  58  may be installed to be vertically movable while being installed at the lower locker installing portion  536 . 
     And a pushing portion  582  which extends downward may be formed at a recessed inside of the lower locker  58 . The pushing portion  582  is in contact with the lower hook  522  formed at the lower cover  52  and is formed to have an inclined surface  582   a . When the lower locker  58  is moved downward, the pushing portion  582  pushes the lower hook  522  so that the lower hook  522  is separated from the case catching portion  537  and thus the lower cover  52  is opened. 
     An inclined surface  522   a  may be formed at an upper end of the lower hook  522 . While the lower cover  52  is closed, the inclined surface  522   a  of the lower hook  522  is in contact with the inclined surface  582   a  of the pushing portion  582 . In this state, when the lower locker  58  is moved downward, the pushing portion  582  pushes the inclined surface  522   a  of the lower hook  522 , and thus the lower hook  522  is elastically deformed. Therefore, due to the elastic deformation of the lower hook  522 , the lower hook  522  may be released from the case catching portion  537 . 
       FIG. 44  is an exploded perspective view illustrating a coupling structure of the lower cover and the dust compressing unit. And  FIG. 45  is an enlarged view of a B portion in  FIG. 41 . 
     As illustrated in the drawings, a bearing  593  may be installed at a center of the lower cover  52 . And the first transmission gear  591  may be provided at a lower surface of the lower cover  52 . The first transmission gear  591  may be connected with the compression motor assembly  323  to be rotatable. When the dust container  50  is seated on the seating part  32 , the first transmission gear  59  is naturally connected to the compression motor assembly  323  to be rotatable. 
     A rotating shaft  591   a  of the first transmission gear  591  may be installed to pass through the bearing  593  and may be smoothly rotated by the bearing  593 . And a second transmission gear  592  is disposed at an upper surface of the lower cover  52  and formed to be connected to the rotating shaft  591   a  of the first transmission gear  591  through the bearing  593 . Accordingly, the second transmission gear  592  may be rotated along with the first transmission gear  591 . 
     The second transmission gear  592  is formed in a circular plate shape, and a plurality of gear portions  592   a  are formed along a circumference thereof. The plurality of gear portions  592   a  may be coupled to a gear coupling protrusion  561   a  formed at an inner circumferential surface of the rotating portion  561  of the dust compressing unit  56 . 
     That is, in an assembling operation of the dust container  50 , when the lower cover  52  is closed while the dust compressing unit  56  is installed, the gear portion  592   a  of the second transmission gear  592  is matched with the gear coupling protrusion  561   a  of the dust compressing unit  56 , and thus the dust compressing unit  56  may be driven. 
     Meanwhile, a coupling boss  592   b  may be formed at a center of an upper surface of the second transmission gear  592 , and a seating groove  592   c  in which a gasket plate  594  is seated may be formed outside the coupling boss  592   b.    
     And a gasket installing protrusion  592   d  is formed at a lower surface of the second transmission gear  592 . A transmission gear gasket  597  is installed at the gasket installing protrusion  592   d . The transmission gear gasket  597  may be sealed by being in contact with the inner circumferential surface of the rotating portion  561 . At this point, the transmission gear gasket  597  is integrally coupled to the second transmission gear  592  and rotated together when the second transmission gear  592  is rotated. 
     The gasket plate  594  is formed in a circular plate shape, and an inner gasket  595  which shields an opened lower surface of the inner case  544  is installed thereat. The inner gasket  595  may be integrally coupled with gasket installing portions  594   a  and  594   b  formed at an upper end of the gasket plate  594 . The inner gasket  595  may be formed in a shape corresponding to an opening of the inner case  544 . 
     The inner gasket  595  may include a first sealing portion  595   a  which is formed in a circular plate shape to be in contact with an opened lower end of the inner case  544  and a second sealing portion  595   b  which is provided above the first sealing portion  595   a  and inserted inside the inner case  544  to be in contact with an inner surface of the inner case  544 , and may seal the opening of the inner case  544  in a fixed state. 
     The gasket installing portions  594   a  and  594   b  include a first protruding portion  594   a  which protrudes upward from an upper surface of the gasket plate  594  and a second protruding portion  594   b  which protrudes vertically outward from the first protruding portion  594   a . Both of the first protruding portion  594   a  and the second protruding portion  594   b  are inserted into a lower surface of the inner gasket  595  and may firmly fix the inner gasket  595  to the gasket plate  594 . 
     Meanwhile, a seating rib  594   c  which is inserted into the seating groove  592   c  may be formed at a lower surface of the gasket plate  594 . The seating rib  594   c  is formed to be movable while being inserted into the seating groove  592   c.    
     And a shaft coupling hole  594   d  in which a shaft coupling member  596  for coupling the gasket plate  594  with the second transmission gear  592  is fastened is formed at a center of the gasket plate  594 . The shaft coupling member  596  may be fastened through the shaft coupling hole  594   d  and the coupling boss  592   b  of the second transmission gear  592 . 
     At this point, the coupling boss  592   b  is formed higher than the gasket plate  594 , and thus the shaft coupling member  596  does not press the gasket plate  594 . Therefore, the gasket plate  594  may be installed to be freely rotatable even while being coupled to the second transmission gear  592 . 
     That is, when the compression motor assembly  323  is driven while the dust container  50  is installed, the first transmission gear  591  and the second transmission gear  592  are rotated, and the rotating portion  561  which is gear-coupled with the second transmission gear  592  is also rotated, and thus the dust compressing unit  56  may be driven. 
     At this point, since the gasket plate  594  seated at the second transmission gear  592  is coupled to be freely rotatable above the second transmission gear  592 , the stopped state may be maintained even when the second transmission gear  592  is rotated. Therefore, the inner gasket  595  installed at the gasket plate  594  may be maintained in a state of shielding the lower surface of the inner case  544 , i.e., the second dust collecting space  502 . 
     Hereinafter, when the main motor is driven, the flow of the dust and the air in the vacuum cleaner will be described. 
       FIG. 46  is a cross-sectional view illustrating the flow of the air and the dust in the cleaner body  10 . And  FIG. 47  is a plan view illustrating the flow of the air and dust in the cleaner body  10 . 
     As illustrated in the drawings, when the user operates the vacuum cleaner  1 , the driving of the main motor  35  starts, and the air containing the dust may be suctioned through the suction unit  20  by a suction force which is generated by the main motor  35 . 
     The air containing the dust may be suctioned through the connector  401  of the cleaner body  10  and then may be suctioned into the dust container  50  through the suction port  511  of the dust container  50 . And in the dust container  50 , the dust and the fine dust are separated by the first cyclone  54  and the second cyclone  55  and then collected in the first dust collecting space  501  and the second dust collecting space  502 , respectively. 
     Specifically, the air containing the dust introduced through the suction port  511  is introduced between the dust container  50  and the strainer  541  through the passage guide  518 . At this point, the air and the dust introduced by the passage guide  518  flows while being rotated along an inner wall of the dust container  50 . 
     While the flowing dust and air pass though the dust filter  542  and the strainer  541 , the dust may be primarily filtered, and the filtered air may be introduced into a space inside the strainer  541 . And the separated dust falls downward, passes through the guide unit  543  and is then stored in the first dust collecting space  501 . The dust collected in the first dust collecting space  501  may be doubly compressed by the dust compressing unit  56 , the guide unit  543  and the backflow preventing portion  531  and then may be stored in the first dust collecting space  501 . 
     Meanwhile, the air filtered while passing through the dust filter  542  and the strainer  541  is introduced inside the casing  551  through the inlet port  551   a  of the casing  551 . At this point, the air introduced into the casing  551  by the guide vane  552  disposed at a side of the inlet port  551   a  forms a vortex flow along an inner wall of the casing  551 . 
     In this process, the fine dust and the air are separated, and the fine dust is secondarily filtered. The fine dust separated in the casing  551  may fall downward through an opened lower surface of the casing  551  and may be stored in the second dust collecting space  402 . And the filtered air flows upward through the outlet port  553   a  of the vortex finder  553  and then flows to the outside of the dust container  50  through the discharge port  512 . 
     The fine dust in the air discharged through the discharge port  512  may be secondarily filtered while the air passes through the prefilter assembly  36 . And the air passed through the prefilter assembly  36  flows to an internal space of the upper frame  34  and passes through the main motor  35 . The air passed through the main motor  35  flows downward through the plate hole  341   a  and passes through the filter unit  39  installed at the lower frame  33 . 
     While the air passes through the filter unit  39 , the ultrafine dust contained in the air may be separated. Eventually, the ultrafine dust may also be tertiarily filtered. Most of the filtered air is used to cool the battery unit  38  under the filter unit  39  and then discharged backward through the rear cover  314 . 
     And some of the air passed through the filter unit  39  passes through the first barrier hole  331   a . In this process, the noise filter  302  and the main PCB  301  are cooled. The air which cools the noise filter  302  and the main PCB  301  may be naturally discharged from the inside of the body part  30  or may be discharged through the rear cover  314 . 
     Meanwhile, to empty the dust container  50  after using of the vacuum cleaner  1 , first, the push member  81  is pushed to operate the locking assembly  80 , and the cover member  40  is opened. When the cover member  40  is completely opened, the cover member  40  is maintained in the opened state by the link assembly  90 . 
     In this state, the dust container  50  is separated from the body part  30 , and then the lower cover  52  may be opened by operating the lower locker  58 . When the lower cover  52  is opened, all of the dust in the first dust collecting space  501  and the second dust collecting space  502  may be removed. And for cleaning and checking the dust container  50 , the upper cover  51  may also be opened by operating the upper locker  57 , and thus internal elements of the dust container  50  may be separated and then may be cleaned and checked. 
     After the dust container  50  is emptied, the dust container  50  is installed again at the body part  30 , and then the cover member  40  is closed by rotating the cover member  40 . 
     Meanwhile, when the vacuum cleaner  1  is used, the user moves while gripping the handle  23 . In this process, travelling of the cleaner body  10  may be controlled. 
       FIG. 48  is a view illustrating a stopped state of the cleaner body  10 . 
     As illustrated in the drawing, while the cleaner body  10  is not moved and is in the stopped state, the center G of the gravity of the cleaner body  10  is located at a rear side further than the rotating center C of the moving wheel  60 . 
     In this state, the cleaner body  10  is intended to be rotated clockwise (in a normal direction) based on the rotating center C of the moving wheel  60 , and the second half portion  313  of the base  31  is lowered and the first half portion  312  is lifted. 
     At this point, the rear wheel unit  70  which is in contact with the ground prevents the second half portion  313  of the base  31  from being excessively lowered, elastically supports the base  31  and enables the cleaner body  10  to be maintained in the stable state. 
     That is, both of the moving wheel  60  and the rear wheel unit  70  are in contact with the ground, and the cleaner body  10  is three-point supported. Also, the rear of the cleaner body  10  at which the center of gravity is located is in a lowered state and thus the cleaner body  10  may maintain the stable posture in the stopped state. 
     Therefore, the first half portion of the cleaner body  10  may be maintained at the set angle α, regardless of presence or absence of the dust in the dust container  50  or the amount of the dust. In this state, the detecting part  306  may determine a posture of the cleaner body  10  through the angle thereof. 
     That is, the detecting part  306  confirms that the first half portion  312  is maintained at the set angle α, determines that the cleaner body  10  is not moved and is maintained in the stopped state and thus allows the wheel motor  632  not to be driven and to be maintained in the stopped state. 
       FIG. 49  is a view illustrating a travelling state of the cleaner body  10 . 
     As illustrated in the drawing, when the user moves forward while gripping the handle  23  to perform the cleaning operation, the suction hose  24  connected to the handle  23  is pulled. And since the connector  401  connected to the suction hose  24  is located at the cover member  40 , the force is applied to a place above the rotating center C of the moving wheel  60 . Accordingly, the cleaner body  10  is rotated counterclockwise (in the reverse direction) by the rotating moment based on the rotating center C of the moving wheel  60 . 
     An angle β between the first half portion  312  and the ground may be changed according to a magnitude of the force applied to the connector  401  but is smaller than the set angle α in the stopped state of the cleaner body  10 . And even when the force applied to the connector  401  becomes greater, the first half portion  312  is not in direct contact with the ground due to the front wheel  312   a , and the front wheel  312   a  is in contact with the ground, and the vacuum cleaner  1  may be stably moved. 
     For example, while the cleaner body  10  is stabled travelled, the center portion  311  is in a horizontal state with the ground. And due to the counterclockwise movement of the cleaner body  10 , the first half portion  312  forms an angle of 20° with respect to the ground, and the second half portion  313  forms an angle of 10°. In this state, the cleaner body  10  may be ideally travelled. However, the angle of the cleaner body  10  may be changed according to a user&#39;s momentary pulling force or a state of the ground. 
     The detecting part  306  detects the posture of the cleaner body  10  and determines the rotation of the moving wheel  60 . When the angle β between the first half portion  312  and the ground is smaller than the set angle α, the detecting part  306  drives the wheel motor  632  and rotates the moving wheel  60  counterclockwise. Due to the rotation of the moving wheel  60 , the cleaner body  10  may be travelled forward. 
     At this point, the detecting part  306  may immediately drive the wheel motor  632  at the moment when the detected angle becomes smaller than the set angle α. If necessary, the wheel motor  632  may be driven when a change value detected by the detecting part  306  exceeds a set range (e.g., 1° to 2°). 
     Meanwhile, since the detecting part  306  may detect a change in the angle β between the first half portion  312  and the ground, a rotating speed of the wheel motor assembly  63  may be controlled in proportion to the change in the angle. For example, when the angle β between the first half portion  312  and the ground becomes sharply smaller, a rotating speed of the wheel motor  632  also becomes faster, and thus the cleaner body  10  may be moved forward at a high speed. And when the angle β between the first half portion  312  and the ground becomes smaller relatively slowly, the rotating speed of the wheel motor  632  may relatively becomes slower. 
     When a distance from the user becomes closer due to forward movement of the cleaner body  10 , the force applied to the connector  401  may become smaller or may be eliminated. When the force applied to the connector  401  is eliminated, the cleaner body  10  is rotated clockwise based on the rotating center of the moving wheel  60  and is in a state illustrated in  FIG. 46 . At this point, the detecting part  306  may confirm that the angle between the first half portion  312  and the ground is the set angle α and thus may stop the driving of the wheel motor assembly  63 . 
     Therefore, when the user moves while gripping the handle  23  to use the vacuum cleaner  1 , the force is applied to the connector  401 , and the cleaner body  10  is moved forward. And when the cleaner body  10  is travelled forward and the distance from the user becomes closer, the force applied to the connector  401  becomes weaker. When the force applied to the connector  401  becomes weaker, the cleaner body  10  is stopped while being rotated clockwise due to the center of gravity. 
     Meanwhile, in a state in which the vacuum cleaner  1  is being travelled, when the angle between the bottom surface of the dust container  50  or the first half portion  312  and the ground (the floor surface) is less than the set angle (α&lt;set angle&lt;β), the driving of the wheel motor assembly  63  may be decelerated. That is, a predetermined speed is maintained until the set angle, and a deceleration thereof starts when the detected angle reaches the set angle, and the wheel motor assembly  63  is stopped when the detected angle is the set angle. Of course, a determination of the angle may be achieved based on the center portion  311  and the second half portion  313  rather than the first half portion  312 . 
     When such a process is repeated, the cleaner body  10  follows the user according to the user&#39;s movement, and thus although the user does not perform a separate operation for moving the cleaner body  10 , autonomous movement may be achieved. 
     Since the first half portion  312  is formed to be inclined, the cleaner body  10  may be effectively moved over the door sill or the obstacle when the door sill or the obstacle is located at the front thereof while being travelled. That is, even in a situation in which the obstacle is generated, the cleaner body  10  may be stably travelled and may be continuously moved over the obstacle. 
     And when it is necessary to move over an high obstacle or the user lifts the handle  23 , the cleaner body  10  is rotated clockwise based on the center of the moving wheel  60 , and thus the second half portion  313  may be moved toward the ground. At this point, the rear wheel unit  70  is in the contacting state with the ground and may prevent the second half portion  313  from being excessively lowered or overturned. And the rear wheel unit  70  elastically supports the second half portion  313  so that the cleaner body  10  is in the state illustrated in  FIG. 46  when the external force is removed from the cleaner body  10 . 
     Meanwhile, the cleaner body  10  may detect the obstacle O while being travelled. When the obstacle O is detected, the cleaner body  10  may be travelled while avoiding the obstacle by controlling the driving of the moving wheel  60 . 
       FIG. 50  is a view illustrating an obstacle avoidance travelling state of the cleaner body. 
     As illustrated in the drawing, when the cleaner body is being travelled or starts the travelling from the stopped state, the obstacle O may be detected by the obstacle detecting member  44 . The plurality of obstacle detecting members  44  are provided at the front surface of the cover member  40  formed in the curved surface shape. After the obstacle detecting member  44  detects the obstacle O located within a set angular range, an obstacle avoidance travelling is performed. 
     For example, as illustrated in the drawing, when the obstacle O is detected by the front sensor  44   c  of the obstacle detecting member  44  while the cleaner body  10  is travelled, a location of the obstacle O is calculated by the main PCB  301  or the detection PCB  360   a.    
     And when the position of the obstacle O is calculated, the main PCB  301  may allow one of the moving wheels  60  located at both of the left and right sides, which is closer to the obstacle O, to be rotated faster, thereby changing a travelling direction of the cleaner body  10  to avoid the obstacle O. 
     At this point, the main PCB  301  may drive only one of the wheel motors  632  located at both sides and may also avoid the obstacle O by differing a rotating speed of each of the wheel motors  632  from each other or differing a rotating direction thereof. 
     And the rotating speed of each of the wheel motors  632  may be deferred according to a distance from the obstacle detected by the obstacle detecting member  44 . That is, when the obstacle O is detected from a long distance, the rotating speed of the wheel motors  632  may become relatively slower, and when the obstacle O is detected from a short distance, the rotating speed of the wheel motors  632  may become relatively faster. 
     As described above, even when the separate operation for avoiding the obstacle O is not performed, it is possible to travel while actively avoiding the obstacle O by the obstacle detecting member  44 . 
     In the embodiment of the present invention, the forward travelling of the cleaner body  10  has been described. However, since the second half portion  313  also has an inclined state, the cleaner body  10  may be automatically moved backward according to a change in an angle of the second half portion  313 . 
       FIG. 51  is a view illustrating a detection range of the obstacle detecting member. As illustrated in the drawing, the obstacle detecting member  44  detects the obstacle located within a set detection distance L. For example, the obstacle detecting member  44  may have a detection distance of about 650 mm. 
     At this point, the detection distance L of the obstacle detecting member  44  may be set to a distance at which the ground is not detected when the cleaner body  10  is rotated counterclockwise and the front wheel  312   a  is in contact with the ground. 
     When the detection distance L is too long, there is a problem that the ground may be recognized as the obstacle when the first half portion  312  of the cleaner body  10  is rotated counterclockwise. On the contrary to this, when the detection distance L is too short, avoidance movement should be performed very rapidly after the obstacle located at the front of the cleaner body  10  is detected, and thus user inconvenience may occur, and even when the avoidance movement is performed, the obstacle may not be avoided completely. 
     Therefore, the obstacle detecting member  44  may have the set distance L at which the ground is not detected when the cleaner body  10  is rotated and the travelling may be performed while effectively avoiding the obstacle. 
     Meanwhile, since the obstacle detecting member  44  is disposed at the front surface of the cover member  40  which is the uppermost end of the cleaner body  10 , an emission angle of the obstacle detecting member  44  may be set so that the ground may not be detected even when an angle of the cleaner body  10  is changed and the obstacle may be effectively detected. 
     For example, when the obstacle detecting member  44  is provided at a lower surface of the cleaner body  10  or a low position, the light emitted from the obstacle detecting member  44  cannot help being directed to the ground, and an detection error may be generated due to a detection of the ground. In particular, due to a characteristic of the cleaner body  10  which is rotated, it is important to select a position at which the obstacle is distinguished while the ground is not detected. 
       FIG. 52  is a view illustrating a wall surface travelling state of the cleaner body  10 . 
     As illustrated in the drawing, the cleaner body  10  may be moved along a wall surface of a room or furniture to perform the cleaning operation. When the cleaner body  10  is moved along the wall surface, the cleaner body  10  should recognize the wall surface, should be travelled along the wall surface without avoidance of the wall surface and then should be rotated after completely escaping from the corner. 
     To this end, the obstacle detecting member  44  may be set so that the front sensors  44   b  and  44   c  and the side sensors  44   a  and  44   d  have different detection distances L 1  and L 2  from each other. The detection distance L 1  of the front sensors  44   b  and  44   c  may be set longer than that L 2  of the side sensors  44   a  and  44   d . For example, when each of the front sensors  44   b  and  44   c  has a detection distance L 1  of about 650 mm, each of the side sensors  44   a  and  44   d  may be set to have a detection distance L 2  of about 300 mm. 
     When the detection distance L 2  of each of the side sensors  44   a  and  44   d  is the same as or longer than that L 1  of each of the front sensors  44   b  and  44   c , the wall surface is too distant due to the detection distance L 2  of each of the side sensors  44   a  and  44   d , and the front sensors  44   b  and  44   c  may not detect the wall surface. Eventually, a situation in which all of the front sensors  44   b  and  44   c  and the side sensors  44   a  and  44   d  may not detect occurs, and thus the wall surface may not be recognized. Therefore, when the detection distance L 2  of each of the side sensors  44   a  and  44   d  is shorter so that the cleaner body  10  is located closer to the wall surface, the front sensors  44   b  and  44   c  and the side sensors  44   a  and  44   d  may simultaneously recognize the wall surface. 
     Meanwhile, when the front sensors  44   b  and  44   c  and the side sensors  44   a  and  44   d  simultaneously recognize the obstacle while the cleaner body  10  is travelled, the obstacle may be regarded as the wall surface, and thus the cleaner body  10  may be travelled along the wall surface without the avoidance movement. That is, the travelling is performed while a state in which the front sensors  44   b  and  44   c  and the side sensors  44   a  and  44   d  detect the wall surface is maintained. 
     When the cleaner body  10  is continuously travelled along the wall surface and then absence of the obstacle is determined by the front sensors  44   b  and  44   c  and the absence of the obstacle is also determined by the side sensors  44   a  and  44   d , it is determined that the cleaner body  10  has passed a corner of the wall surface, and the cleaner body  10  may be travelled in a direction of the corner. 
     At this point, after the absence of the obstacle is also determined by the side sensors  44   a  and  44   d , the cleaner body  10  may be moved forward further by a set distance and then may be rotated. That is, the cleaner body  10  may be rotated after completely passing the corner, and thus a rear portion of the cleaner body  10  may be prevented from colliding with the wall surface. 
     The present invention may have various other embodiments in addition to the above-described embodiment. 
     The remaining configuration of another embodiment of the present invention except a part thereof will be the same as that of the above-described embodiment, and like terms refer to like or corresponding elements and repeated description thereof will be omitted. 
       FIG. 53  is a view illustrating a state in which a body part of the cleaner body according to another embodiment of the present invention is inclined forward. And  FIG. 54  is a view illustrating a state in which the body part is inclined backward. And  FIG. 55  is a view illustrating a configuration of a support part according to another embodiment of the present invention. 
     Referring to  FIGS. 53 to 55 , a cleaner body  1000  includes a body part  1110 , a moving wheel  1120  and a battery  1130 . 
     A dust container  1105  in which the dust suctioned through a suction unit  1160  is stored may be provided at the body part  1110 . A pair of moving wheels  1120  may be coupled to both sides of the body part  1110 , respectively. The battery  1130  may be separably coupled to the body part  1110 . 
     A portion of the cleaner body  1000  in which a connector  1103  is arranged based on a straightly extending line V passing through a rotating center of the moving wheel  1120  may be defined as a front, and a portion thereof in which the battery  1130  is arranged may be defined as a rear. Also, the case in which the body part  1110  is rotated forward is a case in which the body part  1110  is rotated counterclockwise on the drawing (referring to  FIG. 53 ), and the case in which the body part  1110  is rotated backward is a case in which the body part  1110  is rotated clockwise (referring to  FIG. 54 ). 
     The cleaner body  1000  may further include a driving part for driving the moving wheels  1120 . And the cleaner body  1000  may control driving of the moving wheels  1120  by a control part according to detecting information of a detecting part for detecting movement of the cleaner body  1000 . 
     When the detecting part is in an OFF state, the moving wheels  1120  may not be driven. In this case, the body part  1110  is inclined according to a position of a center of gravity. For example, when the center of gravity of the body part  1110  is located at a front of the straightly extending line V passing through the rotating center of the moving wheel  1120 , the body part  1110  is inclined forward, as illustrated in  FIG. 53 , and when the center of gravity of the body part  1110  is located at a rear of the straightly extending line V, the body part  1110  is inclined backward, as illustrated in  FIG. 54 . 
     When the detecting part is turned on, the control part may control the driving of the moving wheels  1120  so that the center of gravity of the body part  1110  is located on the straightly extending line V passing through the rotating center of the moving wheel  1120 . In this case, a lower surface B of the body part  1110  may also be spaced apart from a floor surface G, as illustrated in  FIG. 54 . 
     The cleaner body  1000  may further include a rear wheel unit  1140 . The rear wheel unit  1140  may be disposed at a rear of the lower surface of the body part  1110  and may serve to restrict an angle at which the body part  1110  is inclined backward. 
     The rear wheel unit  1140  may further include an extending portion  1144 . An auxiliary wheel  1142  may be rotatably connected to one side of the extending portion  1144 . The other side of the extending portion  1144  may be rotatably connected to the body part  1110  by a rotating shaft  1146 . And the extending portion  1144  may be rotated upward or downward within a range a-a′. 
     The rear wheel unit  1140  may further include an elastic member  1150 . For example, the elastic member  1150  may be a torsion spring. One end  1152  of the elastic member  1150  may be supported by the body part  1110 , and the other end  1153  thereof may be supported by the extending portion  1144 . The elastic member  1150  may apply an elastic force so that the extending portion  1144  is rotated clockwise on the drawing. 
     When the body part  1110  is maximally inclined forward, a front portion of the lower surface B of the body part  1110  may be in contact with the floor surface G. Thus, a maximum forward rotation angle of the body part  1110  may be restricted. 
     On the other hand, when the body part  1110  is inclined backward, the rear wheel unit  1140  may be in contact with the floor surface G. Accordingly, a maximum backward rotation angle of the body part  1110  may be restricted. Therefore, the body part  1110  may be prevented from being overturned forward or backward. 
     The lower surface B of the body part  1110  may form a predetermined angle θ with respect to the floor surface G when the body part  1110  is maximally inclined backward. At this point, the angle θ between the lower surface B of the body part  1110  and the floor surface G may be about 17° to 20°. 
     A cover  1131  may be provided at the battery  1130 . While the battery  1130  is installed at the body part  1110 , the cover  1131  may be exposed to an outside. Therefore, the cover  1131  may form at least a part of an exterior of the body part  1110 . Also, the user may separate or couple the battery  1130  from/to the body part  1110  without disassembling the body part  1110 . 
     Hereinafter, a process in which the battery  1130  is installed or separated at/from the body part  1110  will be described in detail. However, the following descriptions are limited to the cases in which the center of gravity of the body part  1110  is located at the front when the battery  1130  is separated from the body part  1110  and the center of gravity of the body part  1110  is located at the rear when the battery  1130  is coupled to the body part  1110 . 
       FIG. 56  is a view sequentially illustrating a process in which the battery is coupled to the cleaner body. 
       FIG. 56A  is a view illustrating a state in which the battery  1130  is separated from the body part  1110 , and  FIG. 56B  is a view illustrating a state in which the battery  1130  is coupled to the body part  1110 , and  FIG. 56C  is a view illustrating a state in which the body part  1110  is inclined backward. 
     A battery coupling portion  1107  to which the battery  1130  is coupled is formed at the body part  1110 . The battery coupling portion  1107  may be formed by recessing a part of body part  1110 . 
     The battery coupling portion  1107  is formed at a lower side of the body part  1110 , and thus the battery  1130  is coupled to the lower side of the body part  1110 . For example, while the battery  1130  is installed at the body part  1110 , the center of gravity of the battery  1130  may be located at a lower side further than the rotating center of the moving wheel  1120 . 
     Therefore, since the center of gravity of the battery  1130  may be moved downward when the battery  1130  is coupled to the body part  1110 , travel stability of the cleaner body  1000  may be enhanced. 
     When the battery  1130  is coupled to the lower side of the body part  1110 , there is an advantage that the travel stability of the cleaner body  1000  is enhanced. However, since the battery  1130  should be coupled to the lower side of the body part  1110 , it may be inconvenient for the user to couple the battery  1130 . 
     However, while the battery  1130  is separated from the body part  1110 , the center of gravity of the body part  1110  may be located at a front of the straightly extending line passing through the center of the moving wheel  1120 . Therefore, when the battery  1130  is separated from the body part  1110 , the body part  1110  may be inclined forward about the moving wheel  1120 . 
     As the body part  1110  is inclined forward, the front portion of the lower surface of the body part  1110  comes in contact with the floor surface. At this point, the battery coupling portion  1107  is obliquely directed upward. Therefore, the user may easily couple the battery  1130 . 
     The battery  1130  may be coupled in an oblique direction with respect to the body part  1110  by a coupling guide portion provided at the battery coupling portion  1107 . Specifically, an insertion direction S of the battery  1130  may form an acute angle with respect to each of the straightly extending line V and floor surface. Therefore, when the front portion of the lower surface of the body part  1110  is in contact with the floor surface, the insertion direction S of the battery  1130  forms the acute angle with respect to the floor surface. 
     When the battery  1130  is coupled to the body part  1110 , the center of gravity of the body part  1110  may be moved backward. That is, while the battery  1130  is coupled to the body part  1110 , the center of gravity of the body part  1110  may be located at the rear of the straightly extending line passing through the center of the moving wheel  1120 . 
     In other words, when the battery  1130  is coupled to the body part  1110 , the body part  1110  may be inclined backward about the moving wheels  1120 . At this point, the rear wheel unit  1140  is selectively in contact with the floor surface. At this point, the lower surface B of the body part  1110  forms a predetermined angle θ with respect to the floor surface G. 
       FIG. 57  is a view sequentially illustrating a process in which the battery is separated from the cleaner body. 
     Specifically,  FIG. 57A  illustrates a state before the battery  1130  is separated from the body part  1110 , and  FIG. 57B  illustrates a state in which the battery  1130  is separated from the body part  1110 . 
     To separate the battery  1130  from the body part  1110 , the user may directly apply a force to the body part  1110  and may tilt forward the body part  1110 . Then, the user may separate the battery  1130  in a direction opposite to the insertion direction S. 
     When the battery  1130  is separated from the body part  1110 , the center of gravity of the body part  1110  is moved forward again. Therefore, the body part  1110  may be maintained in a forwardly inclined state. 
     As described above, in the vacuum cleaner of the present invention, while the battery  1130  is installed at the body part  1110 , the body part  1110  may be rotated backward and thus the lower surface of the body part  1110  may be spaced apart from the floor surface. That is, the body part  1110  may be two-point supported by the moving wheels  1120  when travelling. In this case, the cleaner body  1000  may more easily climb over an obstacle, and since travel friction acting on the moving wheels  1120  may be reduced, a labor force required when the user moves the cleaner body  1000  may also be reduced. 
     When the battery  1130  is separated from the body part  1110 , the center of gravity of the body part  1110  is moved forward, and the body part  1110  is rotated forward, and thus the battery coupling portion  1107  provided at a rear lower side of the body part  1110  is moved up. Accordingly, the user may easily couple the battery  1130  to the battery coupling portion  1107 . 
       FIG. 58  is a diagram showing the concept illustrating a reference distance for controlling following movement of a vacuum cleaner according to another embodiment of the present invention. 
     The present embodiment is equal to the previous embodiment except that a component for sensing a distance between the cleaner body  10  and the handle  23  is further included. Accordingly, hereinafter, only the features of the present embodiment will be described. 
     Referring to  FIG. 58 , according to the distance between the cleaner body  10  and the handle  23 , the controller may control output of a wheel motor for driving the moving wheel. That is, the controller may control sensitivity of control processing of inclination of the cleaner body  10  according to the distance between the cleaner body  10  and the handle  23 . 
     The controller may calculate the distance between the cleaner body  10  and the handle  23  using a distance sensor provided in each of the cleaner body  10  and the handle  23 . The distance sensor will be described in detail below with reference to  FIG. 59 . 
     In an example, the controller may calculate the distance between the cleaner body  10  and the handle  23  at a predetermined interval of time. 
     In another example, the controller may calculate the distance between the cleaner body  10  and the handle  23  whenever it is determined that the cleaner body  10  is moved. More specifically, the controller may determine that the cleaner body  10  is moved whenever the wheel motor operates or whenever the moving wheel moves. 
     In the present invention, as shown in  FIG. 58 , reference distances d 1 , d 2  and d 3  for control processing are defined. At this time, the first reference distance d 1  may be less than the second reference distance d 2  and the second reference distance d 2  may be less than the third reference distance d 3 . 
     More specifically, the controller may finish control of the wheel motor for driving the moving wheel regardless of the inclination angle of the cleaner body  10 , when the distance between the cleaner body  10  and the handle  23  is equal to or less than the first reference distance d 1 . Accordingly, the first reference distance d 1  is referred to as a stop reference distance. 
     Meanwhile, the controller may control the wheel motor for driving the moving wheel to move the cleaner body  10  when the distance between the cleaner body  10  and the handle  23  is equal to or less than the first reference distance d 1  and the rotation angle of the cleaner body relative to the rotation center of the moving wheel is equal to or greater than a first reference angle in a state in which the wheel motor is stopped. At this time, the cleaner body  10  rotating with respect to the rotation center of the moving wheel means that the angle between the first half portion  312  of the cleaner body  10  and the ground decreases. 
     In addition, the rotation angle of the cleaner body  10  relative to the rotation center of the moving wheel is a difference between the angle α of  FIG. 47  and the angle β of  FIG. 48  and is equal to the below-described “reference angle”. 
     Accordingly, the rotation angle of the cleaner body  10  relative to the rotation center of the moving wheel may be sensed by the detecting part ( 306  of  FIG. 9 ). 
     More specifically, the first reference angle may be set to a relatively large value. That is, if the distance between the cleaner body  10  and the handle  23  is equal to or less than the first reference distance d 1 , the controller may control the wheel motor for driving the moving wheel to move the cleaner body  10 , only upon determining that inclination of the cleaner body  10  is relatively large. 
     In addition, the controller may control the wheel motor for driving the moving wheel to move the cleaner body  10 , when the distance between the cleaner body  10  and the handle  23  exceeds the first reference distance d 1  and is equal to or less than the second reference distance d 2  and the inclination angle of the cleaner body  10  is equal to or greater than a second reference angle. 
     More specifically, the second reference angle may be set to be less than the first reference angle. That is, the controller may decrease the reference angle for starting driving of the wheel motor from the first reference angle to the second reference angle, when the distance between the cleaner body  10  and the handle  23  exceeds the first reference distance d 1 . 
     When the distance between the cleaner body  10  and the handle  23  exceeds the first reference distance d 1 , the output of the wheel motor may increase. That is, the controller may control the voltage applied to the wheel motor when the distance between the cleaner body  10  and the handle  23  exceeds the first reference distance d 1  to be greater than the voltage applied to the wheel motor when the distance between the cleaner body  10  and the handle  23  is equal to or less than the first reference distance d 1 . 
     In addition, the controller may control the wheel motor for driving the moving wheel to move the cleaner body  10 , when the distance between the cleaner body  10  and the handle  23  exceeds the second reference distance d 2  and is equal to or less than the third reference distance d 3  and the inclination angle of the cleaner body  10  is equal to or greater than a third reference angle. 
     More specifically, the third reference angle may be set to be less than the second reference angle. That is, the controller may decrease the reference angle for starting driving the wheel motor from the second reference angle to the third reference angle when the distance between the cleaner body  10  and the handle  23  exceeds the second reference distance d 2 . 
     In addition, the controller may increase the output of the wheel motor when the distance between the cleaner body  10  and the handle  23  exceeds the second reference distance d 2 . That is, the controller may control the voltage applied to the wheel motor when the distance between the cleaner body  10  and the handle  23  exceeds the second reference distance d 2  to be greater than the voltage applied to the wheel motor when the distance between the cleaner body  10  and the handle  23  is equal to or less than the second reference distance d 2 . 
     The above-described first to third reference distances d 1 , d 2  and d 3  and the first to third reference angles (not shown) are not fixed and may be differently set according to the properties of the vacuum cleaner. 
     Meanwhile, unlike the embodiment shown in  FIG. 59 , the controller of the vacuum cleaner according to the present invention may gradually decrease the reference angle for starting driving of the wheel motor as the distance between the cleaner body  10  and the handle  23  increases, without setting a plurality of reference distances. 
     More specifically, the controller may set the reference angle using Equation 1 below. 
     
       
         
           
             
               
                 
                   α 
                   = 
                   
                     
                       K 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       1 
                     
                     
                       d 
                       + 
                       
                         
                           _ 
                           ⁢ 
                           K 
                         
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         2 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     1 
                   
                   ] 
                 
               
             
           
         
       
     
     In Equation 1 above, α denotes a reference angle, K 1  and K 2  denote constants, and d denotes the distance between the cleaner body  10  and the handle  23  calculated by the controller. 
     That is, the controller may calculate the distance between the cleaner body  10  and the handle  23  at a predetermined interval of time and decrease the reference angle as the calculated distance increases. 
     In addition, the controller may increase a voltage or current applied to the wheel motor as the calculated distance increases. 
     Meanwhile, the controller may finish control of the wheel motor for driving the moving wheel if the distance enters a limited distance (reference distance range), even when the reference angle is gradually changed. 
     In addition, the controller may perform a first control method of changing a reference angle based on a plurality of reference distances and a second control method of gradually changing a reference angle, based on user input. That is, the controller may determine whether the wheel motor for driving the moving wheel is driven through the first control method or the second control method according to user input. 
       FIG. 59  is a diagram showing the concept illustrating a sensor attached to each of a handle and a main body of a vacuum cleaner to sense a distance between the handle and the main body according to the present invention. 
     Referring to  FIG. 59 , a first sensor  910  attached to the handle  23  and a second sensor  920  attached to the cleaner body  10  may perform wireless communication with each other. 
     More specifically, the first and second sensors  910  and  920  may transmit or receive a signal having a pulse capable of penetrating through an object at a predetermined distance or less. 
     For example, the first and second sensors  910  and  920  may be ultra wide band (UWB) sensors, and a pulse transmitted or received by the UWB sensor may be a very short pulse of several nanoseconds or several picoseconds. 
     For reference, UWB wireless technology uses a very wide frequency band of several GHz or more in a baseband without using a RF carrier. That is, the UWB wireless technology uses a very short pulse of several nanoseconds or picoseconds. 
     The pulse emitted from the UWB sensor is of several nanoseconds or picoseconds and thus has good penetrability. Accordingly, one UWB sensor may receive a very short pulse emitted from another UWB sensor regardless of a peripheral obstacle. 
     The UWB sensor may include a transmitter and a receiver formed as one module. That is, the first and second sensors  910  and  920  may transmit or receive a signal. 
     That is, the first and second sensors  910  and  920  respectively provided in the handle  23  and the cleaner body  10  transmit and receive pulses capable of penetrating through an object and thus perform wireless communication regardless of the obstacle. 
     For example, when the user turns the corner, if a wall is present between the handle  23  and the cleaner body  10  or a user body is located between the handle  23  and the cleaner body  10 , the distance between the handle  23  and the cleaner body  10  may be calculated using wireless communication between the first and second sensors  910  and  920 . 
       FIG. 60  is a flowchart illustrating a method of controlling a vacuum cleaner according to the present invention. 
     Referring to  FIG. 60 , the controller may sense the distance d between the cleaner body  10  and the handle  23  using the distance sensors  910  and  920  respectively provided in the cleaner body  10  and the handle  23  (S 1001 ). 
     The controller may compare the sensed distance d with the first to third reference distances (S 1002 , S 1003 ). 
     The controller may finish driving of the wheel motor when the sensed distance d is less than the first reference distance d 1  (S 1004 ). 
     In addition, the controller may set the reference angle of the cleaner body for driving the wheel motor to A when the sensed distance d is equal to or greater than the first reference distance d 1  and is less than the second reference distance d 2  (S 1005 ). At this time, the angle A may correspond to the second reference angle. 
     In addition, the controller may set the reference angle of the cleaner body to B less than A when the sensed distance d is equal to or greater than the second reference distance d 2  (S 1006 ). At this time, the angle B may correspond to the third reference angle. 
     According to the vacuum cleaner according to the embodiment of the present invention, the following effects can be expected. 
     According to the vacuum cleaner and the method of controlling the same of the embodiment of the present invention, an obstacle located at a front side is detected by the obstacle detecting members including a laser sensor while the cleaner travels. Accordingly, the cleaner body traveling at the back side of a user may control rotation of the moving wheel to avoid the obstacle upon detecting the obstacle. Accordingly, the cleaner body can detect and avoid the obstacle without user manipulation, thereby improving user convenience. 
     The obstacle detecting members are located at both sides of the suction hose and may be located at positions rotated from the suction hose by a predetermined angle in order to prevent the suction hose from be detected. Accordingly, it is possible to prevent malfunction caused due to detection of the suction hose to improve operation reliability. 
     The obstacle detecting members are formed on the upper ends of the front surface of the cleaner body and are formed to have a predetermined detection distance. Accordingly, the obstacle detecting members can detect the ground even when the cleaner moves or stops or even when the state of the cleaner is changed, thereby preventing malfunction to improve operation reliability. 
     Since the obstacle detecting members include a plurality of front sensors and side sensors, it is possible to efficiently detect an obstacle in a front even region in which the cleaner travels. 
     In addition, the PCB may control driving of the wheel driving assembly upon detecting the obstacle by the obstacle detecting members, such that the cleaner efficiently avoid the obstacle. 
     In addition, the wall or the corner of the wall is sensed by the front sensor and the side sensor such that the cleaner travels along the wall or rotates after passing through the corner, thereby improving user convenience. 
     According to the present invention, since the vacuum cleaner according to the present invention can calculate the distance between the cleaner body and the handle even when an obstacle is present between the cleaner body and the handle, the vacuum cleaner can follow the user regardless of whether the obstacle is present between the cleaner body and the handle. 
     In addition, since the vacuum cleaner according to the present invention can follow the user before tension of the hose exceeds a predetermined value, the vacuum cleaner can follow the user even when the vacuum cleaner is pulled with force weaker than minimum force capable of inclining the cleaner body. 
     In the vacuum cleaner according to the embodiment of the present invention, since the center of gravity of the cleaner body is located at the second half portion, the cleaner body can be rotated about the moving wheel and can be maintained in the stably supported state by being in contact with the ground. 
     And since the center of gravity is located at the second half portion, when the travelling of the vacuum cleaner is stopped, the cleaner body can be rotated and then can be in the inclined state, and when the cleaner body is travelled, the change in the angle thereof occurs by the rotation, and thus the stopped or moving state of the vacuum cleaner can be accurately determined. 
     Also, the detecting part for detecting the posture of the cleaner body, i.e., the slope or the rotating angle thereof is provided inside the cleaner body. And since the vacuum cleaner has a structure in which the suction hose is connected to the upper portion of the cleaner body, the cleaner body is inclined when the user pulls the suction hose to move the vacuum cleaner, and the moving wheel is driven by the detecting part which detects the situation. 
     Therefore, although the user does not pull the cleaner body itself to move the cleaner body, the cleaner body can be automatically travelled by an simple operation such as moving of the suction hose, and the cleaner body can be travelled following the user when the user moves, and thus user convenience can be enhanced. 
     Particularly, since the cleaner body can be stopped while the slope of the cleaner body is maintained always constantly, regardless of presence and absence of the dust or the amount of the dust, reliability of the detecting part in detecting the slope can be enhanced. 
     Even though all the elements of the embodiments are coupled into one or operated in the combined state, the present disclosure is not limited to such an embodiment. That is, all the elements may be selectively combined with each other without departing the scope of the invention. Furthermore, when it is described that one comprises (or comprises or has) some elements, it should be understood that it may comprise (or include or have) only those elements, or it may comprise (or include or have) other elements as well as those elements if there is no specific limitation. Unless otherwise specifically defined herein, all terms comprising technical or scientific terms are to be given meanings understood by those skilled in the art. Like terms defined in dictionaries, generally used terms needs to be construed as meaning used in technical contexts and are not construed as ideal or excessively formal meanings unless otherwise clearly defined herein. 
     Although embodiments have been described with reference to a number of illustrative embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention as defined by the appended claims. Therefore, the preferred embodiments should be considered in descriptive sense only and not for purposes of limitation, and also the technical scope of the invention is not limited to the embodiments. Furthermore, is defined not by the detailed description of the invention but by the appended claims, and all differences within the scope will be construed as being comprised in the present disclosure.