Patent Publication Number: US-10765288-B2

Title: Vacuum cleaner

Description:
CROSS-REFERENCE TO RELATED APPLICATION AND CLAIM OF PRIORITY 
     This application is related to and claims the benefit of Korean Patent Application No. 10-2017-0028123, filed on Mar. 6, 2017, the disclosure of which is incorporated by reference herein in its entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to a vacuum cleaner that travels actively according to a user&#39;s intention. 
     BACKGROUND 
     A vacuum cleaner is a home appliance including a fan motor to generate a suction force for sucking air from the floor to be cleaned, and a dust collecting apparatus to remove dust from the sucked air to clean the floor. There are various kinds of vacuum cleaners including a canister type, an upright type, a hand type, and a robot type. 
     An upright type vacuum cleaner includes a main frame having a handle and a dust collecting apparatus, and a base coupled with the main frame and having a suction opening, a brush, and one or more wheels. A user grips the handle of the main frame to clean the floor. 
     However, many users experience difficulties in operating the upright type vacuum cleaner due to its strong suction force and heavy weight. For this reason, some upright type vacuum cleaners include a driver for driving wheels such that the wheels can travel actively. 
     However, typical drivers could not accurately identify a user&#39;s intention, that is, a direction in which a user intends to clean, which caused cases in which the user is pulled by the vacuum cleaner. In order for a vacuum cleaner to accurately identify a user&#39;s intention, the vacuum cleaner needs various sensors and control circuits additionally. 
     SUMMARY 
     Therefore, it is an aspect of the present disclosure to provide a vacuum cleaner with improved convenience in operation by reflecting a user&#39;s intention to adjust driving speed and a driving direction. 
     It is another aspect of the present disclosure to provide a cleaner with improved convenience in operation through a simple mechanical structure without including a separate sensor and a control circuit portion. 
     Additional aspects of the disclosure will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the disclosure. 
     In accordance with an aspect of the present disclosure, a vacuum cleaner includes a base including a suction opening; a main frame including a dust collecting apparatus configured to remove dust from air sucked through the suction opening; and a wheel assembly including a forward wheel and a reverse wheel, and rotatably coupled with the base, wherein when the main frame slides with respect to the base, any one of the forward wheel or the reverse wheel contacts a floor. 
     The vacuum cleaner may further include a bracket coupled with the base and the main frame, wherein the bracket may slide with respect to the base together with the main frame. 
     The bracket may include a rack gear portion configured to rotate the wheel assembly. 
     The wheel assembly may include a wheel housing in which the forward wheel and the reverse wheel are installed, and the wheel housing may include a pinion gear portion engaged with the rack gear portion. 
     The vacuum cleaner may further include a link configured to connect the bracket to the wheel assembly, and forming a slider crank mechanism configured to convert sliding of the bracket into rotation of the wheel assembly. 
     The vacuum cleaner may further include a driving motor configured to generate power for driving the forward wheel and the reverse wheel; and a power transmission mechanism configured to transmit the power from the driving motor to the forward wheel and the reverse wheel. 
     The power transmission mechanism may include a base gear assembly disposed in the base, a wheel gear assembly disposed in the wheel housing, and a connection shaft connecting the base gear assembly to the wheel gear assembly. 
     The wheel gear assembly may be configured to rotate on the connection shaft. 
     The wheel gear assembly may include a connection gear configured to rotate on the connection shaft, at least one forward gear disposed between the connection gear and the forward wheel, and at least one reverse gear disposed between the connection gear and the reverse wheel. 
     The vacuum cleaner may further include a one-way clutch disposed between the at least one forward gear and the forward wheel; and a second one-way clutch disposed between the at least one reverse gear and the reverse wheel. 
     The forward wheel and the reverse wheel may be configured to rotate simultaneously. 
     The forward wheel and the reverse wheel may be configured to rotate in opposite directions. 
     The forward wheel and the reverse wheel may be configured to rotate at the same speed. 
     The wheel assembly may include an idle wheel contacting the floor when none of the forward wheel and the reverse wheel contacts the floor. 
     In accordance with another aspect of the present disclosure, a vacuum cleaner includes a base including a suction opening; a main frame including a dust collecting apparatus configured to remove dust from air sucked through the suction opening; a bracket coupled with the base and the main frame, wherein the bracket slides with respect to the base together with the main frame; and a wheel assembly including a wheel housing and a wheel installed in the wheel housing, and rotatably coupled with the base, wherein when the main frame and the bracket slide with respect to the base, the wheel contacts or does not contact a floor. 
     The bracket may include a rack gear portion configured to rotate the wheel assembly, and wherein the wheel housing comprises a pinion gear portion engaged with the rack gear portion. 
     The wheel assembly may include a left wheel assembly disposed in a left portion of the base, and a right wheel assembly disposed in a right portion of the base. 
     The vacuum cleaner may further include a driving motor configured to generate power for driving a wheel of the left wheel assembly and a wheel of the right wheel assembly; and a power transmission mechanism configured to transfer power from the driving motor to the wheel of the left wheel assembly and the wheel of the right wheel assembly. 
     The power transmission mechanism may include a differential gear apparatus configured to transfer power to the wheel of the left wheel assembly and the wheel of the right wheel assembly, differentially, according to loads applied from the driving motor to the wheel of the left wheel assembly and the wheel of the right wheel assembly. 
     In accordance with another aspect of the present disclosure, a vacuum cleaner includes a base including a suction opening; a main frame including a dust collecting apparatus configured to remove dust from air sucked through the suction opening; and a left wheel assembly and a right wheel assembly each including a forward wheel and a reverse wheel, and rotatably coupled with left and right portions of the base, wherein when the main frame is pushed, the left wheel assembly and the right wheel assembly rotate in a first direction so that a forward wheel of the left wheel assembly and a forward wheel of the right wheel assembly contact a floor, and wherein when the main frame is pulled, the left wheel assembly and the right wheel assembly rotate in a second direction that is opposite to the first direction so that a reverse wheel of the left wheel assembly and a reverse wheel of the right wheel assembly contact the floor. 
     Before undertaking the DETAILED DESCRIPTION below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation; the term “or,” is inclusive, meaning and/or; the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like. 
     Definitions for certain words and phrases are provided throughout this patent document. Those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects of the disclosure will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG. 1  illustrates a vacuum cleaner according to an embodiment of the present disclosure; 
         FIG. 2  illustrates a base portion and a wheel assembly of the vacuum cleaner of  FIG. 1 ; 
         FIG. 3  is an exploded perspective view illustrating an internal structure of the base portion of the vacuum cleaner of  FIG. 1 ; 
         FIG. 4  is a top view illustrating the internal structure of the base portion of the vacuum cleaner of  FIG. 1 ; 
         FIG. 5  illustrates a power transmission mechanism of the vacuum cleaner of  FIG. 1 ; 
         FIG. 6  illustrates a differential gear apparatus of the vacuum cleaner of  FIG. 1 ; 
         FIG. 7  illustrates a wheel gear assembly of a wheel assembly of the vacuum cleaner of  FIG. 1 ; 
         FIGS. 8 and 9  are views for illustrating sliding of a bracket and rotation of a wheel assembly, when a user pushes the main frame of the vacuum cleaner of  FIG. 1 ; 
         FIGS. 10 and 11  are views for illustrating sliding of the bracket and rotation of the wheel assembly, when a user pulls the main frame of the vacuum cleaner of  FIG. 1 ; and 
         FIGS. 12 and 13  illustrate a slider crank mechanism of a vacuum cleaner according to another embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 through 13 , discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged system or device. 
     The embodiments described in the present disclosure are embodiments of the present disclosure, and thus it is to be understood that various equivalents or modified examples, that may replace the embodiments described in the present specification, are possible. 
     Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. 
       FIG. 1  illustrates a vacuum cleaner according to an embodiment of the present disclosure.  FIG. 2  illustrates a base portion and a wheel assembly of the vacuum cleaner of  FIG. 1 .  FIG. 3  is an exploded perspective view illustrating an internal structure of the base portion of the vacuum cleaner of  FIG. 1 .  FIG. 4  is a top view illustrating the internal structure of the base portion of the vacuum cleaner of  FIG. 1 .  FIG. 5  illustrates a power transmission mechanism of the vacuum cleaner of  FIG. 1 .  FIG. 6  illustrates a differential gear apparatus of the vacuum cleaner of  FIG. 1 .  FIG. 7  illustrates a wheel gear assembly of a wheel assembly of the vacuum cleaner of  FIG. 1 . 
     Referring to  FIGS. 1 to 7 , a vacuum cleaner  1  may include a base  20  including a suction opening  23  configured to suck air from a floor to be cleaned, a main frame  10  including a suction fan (not shown) configured to generate a suction force and a dust collecting apparatus  16  configured to remove dust from the air sucked through the suction opening  23 , and a pair of wheel assemblies  40  (that is, a left wheel assembly  40   a  and a right wheel assembly  40   b ) disposed in left and right portions of the base  20 . 
     The base  20  may be formed by assembling an upper base  21  with a lower base  22 . In the base  20 , a suction flow path  24  may be formed to guide air sucked through the suction opening  23  to the dust collecting apparatus  16 . 
     The suction flow path  24  may communicate with a guide flow path  13  of the main frame  10 . Accordingly, air sucked through the suction opening  23  may be guided to the dust collecting apparatus  16  via the suction flow path  24  and the guide flow path  13 . The dust collecting apparatus  16  may collect dust from the air, and then discharge the air from which the dust has been removed to the outside through a separate outlet (not shown). 
     A brush  25  may be rotatably installed in the suction opening  23 . The brush  25  may be configured to sweep dust from the floor to be cleaned. Dust remaining on the floor may be swept up from the floor by the brush  25 , and sucked into the suction opening  23  by a suction force of the suction fan. The brush  25  may rotate by receiving power from a brush driving motor  26 . 
     The dust collecting apparatus  16  may be a dust bag type to filter dust out by passing air through a dust bag, or a cyclone type to separate dust through centrifugation, although the dust collecting apparatus  16  is not limited to these embodiments. 
     The main frame  10  may be configured with a main frame body  11 , and a neck portion  12  disposed below the main frame body  11  to be coupled with the base  20 . The neck portion  12  may be rotatably coupled with the base  20 . The neck portion  12  may include an operating groove  14  into which an operating protrusion  31  of a bracket  30  is inserted, and a neck tooth portion  15  supported by a support gear  37 . 
     In the main frame body  11 , a handle  17  configured to be gripped by a user&#39;s hand to move the main frame  10  may be provided. The user may grip the handle  17  to push or pull the main frame  10  or to turn the main frame  10  in a left or right direction. 
     The wheel assemblies  40  may be disposed in the left and right portions of the base  20 . Each of the left and right wheel assemblies  40   a  and  40   b  may include a forward wheel  43  and a reverse wheel  44 . That is, the vacuum cleaner  1  according to an embodiment of the present disclosure may include a total of four wheels, that is, the forward wheel  43  and the reverse wheel  44  of the left wheel assembly  40   a  and the forward wheel  43  and the reverse wheel  44  of the right wheel assembly  40   b.    
     The forward wheel  43  and the reverse wheel  44  may rotate by receiving power from a driving motor  27  to enable the vacuum cleaner  1  to travel actively. Particularly, the vacuum cleaner  1  according to an embodiment of the present disclosure may understand the user&#39;s intention, and move forward/backward or turn according to the user&#39;s intention. 
     The vacuum cleaner  1  may include the bracket  30  coupled with the base  20  in such a way to slide back and forth. In order for the bracket  30  to be coupled with the base  20  in such a way to slide back and forth, a bracket installing portion  28  may be formed in the base  20 , wherein the bracket  30  is slidably coupled with the bracket installing portion  28 . In a front end and a rear end of the bracket installing portion  28 , stopper portions  29   a  and  29   b  (see  FIG. 8 ) may be formed to limit a movement range of the bracket  30 . 
     In some embodiments, the bracket  30  may be further coupled with the main frame  10 . More specifically, the bracket  30  may be coupled with the main frame  10  in such a way to translate together with the main frame  10 , while relatively rotating with respect to the main frame  10 . For this, the bracket  30  may include an operating protrusion  31  inserted into the operating groove  14  of the neck portion  12  of the main frame  10 . The operating protrusion  31  may be rotatable in the operating groove  14 . When the operating protrusion  31  of the bracket  30  is inserted into and coupled with the operating groove  14  of the neck portion  12 , the bracket  30  may translate together with the main frame  10 , and rotate with respect to the main frame  10 . 
     The bracket  30  may include support gears  37  and  38  to rotatably support the main frame  10 . The support gear  38  may be engaged with the neck tooth portion  15  of the neck portion  12  of the main frame  10  to support a weight of the main frame  10  regardless of an angle of rotation of the main frame  10 . 
     The bracket  30  may include a rack gear portion  32  configured to rotate the wheel assemblies  40 . When the main frame  10  slides with respect to the base  20 , the rack gear portion  32  of the bracket  30  may slide accordingly, and the sliding of the rack gear portion  32  may be transferred to the wheel assemblies  40  so that the wheel assemblies  40  can rotate. 
     More specifically, the rack gear portion  32  may be engaged with a middle gear  60 , and the middle gear  60  may be engaged with a pinion gear portion  42  of the wheel assemblies  40 . The bracket  30  may include a roller  36  to cause the bracket  30  to slide smoothly in the base  20 . A pair of brackets  30  may be respectively disposed in the left and right portions of the base  20 . 
     Each wheel assembly  40  may include a wheel housing  41 , and the forward wheel  43  and the reverse wheel  44  installed in the wheel housing  41 . The wheel housing  41  may include a shaft portion  41   a  protruding toward the base  20 . The shaft portion  41   a  may be in the shape of a cylinder, and the pinion gear portion  42  may be formed on an outer circumferential surface of the shaft portion  41   a . Accordingly, the wheel housing  41  may rotate on the shaft portion  41   a.    
     The forward wheel  43  and the reverse wheel  44  may be installed in the wheel housing  41  in such a way to be rotatable on rotation shafts  43   a  and  44   a  (see  FIG. 7 ), respectively. A rotation shaft  43   a  of the forward wheel  43  may be eccentric to a rotation shaft  44   a  of the reverse wheel  44 , and the rotation shaft  43   a  of the forward wheel  43  and the rotation shaft  44   a  of the reverse wheel  44  may be eccentric to the shaft portion  41   a  of the wheel housing  41 . Accordingly, when the wheel housing  41  rotates on the shaft portion  41   a , the forward wheel  43  and the reverse wheel  44  may also rotate (revolve) around the shaft portion  41   a.    
     When the driving motor  27  operates, the forward wheel  43  and the reverse wheel  44  may rotate (spin) on the corresponding rotation shafts  43   a  and  44   a . The forward wheel  43  and the reverse wheel  44  may be rotatable in opposite directions. For example, the forward wheel  43  may rotate in a direction of moving the base  20  forward, and the reverse wheel  44  may rotate in a direction of moving the base  20  backward. 
     As described above, the middle gear  60  may be engaged with the pinion gear portion  42 , and the rack gear portion  32  of the bracket  30  may be engaged with the middle gear  60 . Accordingly, when the rack gear portion  32  slides, the middle gear  60  may rotate in one direction, and the pinion gear portion  42  may rotate in the opposite direction. As a result, when the main frame  10  is pushed forward or pulled backward, the wheel housing  41  may rotate on the shaft portion  41   a . When the wheel housing  41  rotates on the shaft portion  41   a , the forward wheel  43  and the reverse wheel  44  installed in the wheel housing  41  may also rotate on the shaft portion  41   a.    
     According to an embodiment of the present disclosure, when the main frame  10  slides with respect to the base  20 , any one of the forward wheel  43  and the reverse wheel  44  of each wheel assembly  40  may contact a floor. More specifically, in an initial state, none of the forward wheel  43  and the reverse wheel  44  may contact the floor, and when the main frame  10  slides forward with respect to the base  20 , the forward wheel  43  may contact the floor. In contrast, when the main frame  10  slides backward with respect to the base  20 , the reverse wheel  44  may contact the floor. 
     The wheel assembly  40  may include an idle wheel  49  configured to contact the floor when none of the forward wheel  43  and the reverse wheel  44  contacts the floor. 
     In the current embodiment, the middle gear  60  may be disposed between the rack gear portion  32  of the bracket  30  and the pinion gear portion  42  of the wheel assembly  40 . However, in some embodiments the rack gear portion  32  may be directly engaged with the pinion gear portion  42  without the middle gear  60  in between. 
     The vacuum cleaner  1  may include the driving motor  27 , configured to generate power for driving the forward wheel  43  and the reverse wheel  44 , and a power transmission mechanism configured to transmit power generated by the driving motor  27  to the forward wheel  43  and the reverse wheel  44 . 
     According to an embodiment of the present disclosure, all of the four wheels: the forward wheel  43  and the reverse wheel  44  of the left wheel assembly  40   a  and the forward wheel  43  and the reverse wheel  44  of the right wheel assembly  40   b , may receive power from the driving motor  27 . According to an embodiment of the present disclosure, the driving motor  27  for providing power to the wheels may be separated from the brush driving motor  26  that is configured to provide power to the brush  25 . However, a single motor may supply power to both the wheels and the brush  25 . 
     As the power transmission mechanism, various mechanical elements for transmitting power, such as a gear, a belt, a pulley, and a chain, may be used. In one embodiment, the power transmission mechanism may include a base gear assembly disposed in the base  20 , a wheel gear assembly disposed in the wheel housing  41 , and a connection shaft CS (see  FIG. 5 ) configured to connect the base gear assembly to the wheel gear assembly. 
     The base gear assembly may include base gears BG 1  to BG 3  disposed between the driving motor  27  and a differential gear apparatus DG, and base gears BG 4  to BG 9  disposed between the differential gear apparatus DG and the connection shaft CS. 
     The differential gear apparatus DG may distribute power generated by the driving motor  27 , and transfer the distributed power to the wheel assemblies  40   a  and  40   b  disposed in the left and right portions of the base  20 . As shown in  FIG. 6 , the differential gear apparatus DG may include a ring gear DG 1  connected to a driving side, a plurality of sun gears DG 2  and DG 3  connected to a passivity side, and a plurality of planetary gears DG 4  and DG 5  configured to spin and revolve around the plurality of sun gears DG 2  and DG 3 . 
     The planetary gear DG 4  may be engaged with the planetary gear DG 5 , the planetary gear DG 4  may be engaged with the sun gear DG 2 , and the planetary gear DG 5  may be engaged with the sun gear DG 3 . Accordingly, the sun gear DG 2 , the sun gear DG 3 , the planetary gear DG 4 , and the planetary gear DG 5  may be engaged with one another. 
     The differential gear apparatus DG may include a plurality of additional planetary gears DG 6  and DG 7  to transfer power more stably. The planetary gears DG 6  and DG 7  may perform the same function as the planetary gears DG 4  and DG 5 . 
     The ring gear DG 1  may be integrated into a disk  70 , and a plurality of rotating shafts  71  and  72  of the plurality of planetary gears DG 4  and DG 5  may protrude from the disk  70  in such a way to be eccentric to a rotation shaft of the ring gear DG 1 . 
     Through the above-described structure, when the driving motor  27  operates and thus the ring gear DG 1  rotates, the disk  70  may rotate together with the ring gear DG 1 , and the plurality of planetary gears DG 4  and DG 5  connected to the rotating shafts  71  and  72  formed on the disk  70  may revolve around the rotating shaft of the ring gear DG 1 . Accordingly, the plurality of sun gears DG 2  and DG 3  may rotate to transfer a rotation force to the plurality of wheel assemblies  40   a  and  40   b.    
     When different loads are applied to the plurality of wheel assemblies  40   a  and  40   b , that is, when a user turns the vacuum cleaner  1  in the left or right direction, different loads may be applied to the plurality of sun gears DG 2  and DG 3 , and accordingly, the plurality of planetary gears DG 4  and DG 5  may rotate in different directions. 
     Accordingly, the plurality of sun gears DG 2  and DG 3  may rotate by different numbers of rotation resulting from adding or subtracting the numbers of rotation of the plurality of planetary gears DG 4  and DG 5 . As a result, the differential gear apparatus DG may transfer power to the forward wheel  43  and reverse wheel  44  of the left wheel assembly  40   a  and the forward wheel  43  and reverse wheel  44  of the right wheel assembly  40   b  differentially, according to loads applied to the left wheel assembly  40   a  and the right wheel assembly  40   b.    
     For example, when the user turns the vacuum cleaner  1  in the left direction, a load may be applied to the forward wheel  43  and reverse wheel  44  of the left wheel assembly  40   a , and accordingly, more power may be transferred to the forward wheel  43  and reverse wheel  44  of the right wheel assembly  40   b  than to the forward wheel  43  and reverse wheel  44  of the left wheel assembly  40   a . Accordingly, the forward wheel  43  and reverse wheel  44  of the right wheel assembly  40   b  may rotate more than the forward wheel  43  and reverse wheel  44  of the left wheel assembly  40   a , so that the vacuum cleaner  1  can turn to the left. 
     In some embodiments, the base gears BG 1  to BG 3  may be engaged with one another. In some embodiments, the base gears BG 4  to BG 6  may be engaged with one another. The base gears BG 6  and BG 7  may be connected to a shaft S 1  to rotate together. The base gear BG 7  may be engaged with the base gear BG 8 , and rotate together with the base gear BG 8 . The base gears BG 8  and BG 9  may be connected to a shaft S 2  to rotate together. The middle gear  60  may be rotatable on the shaft S 2 . 
     The connection shaft CS may be disposed in the inside of the shaft portion  41   a  of the wheel housing  41  described above. Accordingly, the wheel assembly  40  may rotate on the connection shaft CS. 
     The wheel gear assembly may include a connection gear CG coupled with the connection shaft CS to rotate on the connection shaft CS, one or more forward gears FG 1  and FG 2  disposed between the connection gear CG and the forward wheel  43  in such a way to be engaged with each other, and one or more reverse gears RG 1 , RG 2 , and RG 3  disposed between the connection gear CG and the reverse wheel  44  in such a way to be engaged with each other. 
     The number of the forward gears FG 1  and FG 2  may be different from the number of the reverse gears RG 1 , RG 2 , and RG 3  so that the forward wheel  43  and the reverse wheel  44  may rotate in different directions. In the current embodiment, two forward gears FG 1  and FG 2  may be provided so that the forward wheel  43  may rotate in the same direction FR (see  FIG. 7 ) as a rotation direction of the connection gear CG, and three reverse gears RG 1 , RG 2 , and RG 3  may be provided so that the reverse wheel  44  may rotate in a direction RR (see  FIG. 7 ) that is opposite to a rotation direction of the forward wheel  43 . In some embodiments, by adjusting gear ratios of the forward gears FG 1  and FG 2  and the reverse gears RG 1 , RG 2 , and RG 3 , the forward wheel  43  and the reverse wheel  44  may rotate at the same speed. 
     Through the above structure, power may be transferred from the driving motor  27  to the forward wheels  43  and the reverse wheels  44  of the wheel assemblies  40   a  and  40   b . In this embodiment, the operation of transferring power from the driving motor  27  to the forward wheels  43  and the reverse wheels  44  of the wheel assemblies  40   a  and  40   b  may be performed regardless of an angle of rotation of the wheel housing  41 , because the connection shaft CS connecting the base gear assembly to the wheel gear assembly is formed in the inside of the shaft portion  41   a  that is the rotation shaft of the wheel housing  41 , as described above. 
     A one-way clutch C (see  FIG. 7 ) may be disposed between the forward gear FG 2  and the forward wheel  43 . The one-way clutch C may be configured to cause a rotation force to be transferred to the forward wheel  43  when the forward gear FG 2  rotates in one direction, and when the forward gear FG 2  rotates in the opposite direction, the one-way clutch C may prevent a rotation force from being transferred to the forward wheel  43 . 
     More specifically, when the forward gear FG 2  rotates in the FR direction, as shown in  FIG. 7 , a rotation force may be transferred to the forward wheel  43  so that the forward wheel  43  rotates in the FR direction, and when the forward gear FG 2  rotates in the RR direction that is opposite to the FR direction, no rotation force may be transferred to the forward wheel  43 . 
     When the driving motor  27  is in an off state, the forward wheel  43  may rotate in the FR direction without receiving any load from the forward gear FG by the one-way clutch C. That is, the forward wheel  43  may rotate idly in the FR direction without receiving any load from the forward gear FG by the one-way clutch C. Accordingly, if a user pushes the main frame  10  forward when the driving motor  27  is in an off state, the wheel assembly  40  may rotate so that the forward wheel  43  contacts the floor, and the forward wheel  43  may rotate idly in the FR direction so that the vacuum cleaner  1  may move forward. 
     The one-way clutch C may include various structures well-known in the related art, and may be disposed between the reverse gear RG 3  and the reverse wheel  44 . 
       FIGS. 8 and 9  are views for illustrating sliding of a bracket and rotation of a wheel assembly, when a user pushes the main frame of the vacuum cleaner  1  of  FIG. 1 .  FIGS. 10 and 11  are views for illustrating sliding of the bracket and rotation of the wheel assembly, when a user pulls the main frame of the vacuum cleaner  1  of  FIG. 1 . 
     Hereinafter, operations of the vacuum cleaner  1  according to an embodiment of the present disclosure will be described with reference to  FIGS. 8 to 11 . 
     As shown in  FIGS. 8 and 9 , when a user grips the handle  17  and pushes the main frame  10 , the main frame  10  may slide forward (in an F direction) with respect to the base  20 . More specifically, the bracket  30  coupled with the main frame  10  may slide forward (in the F direction) with respect to the base  20 . 
     If the bracket  30  slides forward, the rack gear portion  32  of the bracket  30  may slide forward, and the middle gear  60  engaged with the rack gear portion  32  may rotate. 
     Since the pinion gear portion  42  of the wheel housing  41  is engaged with the middle gear  60 , the wheel housing  41  may rotate in a WR 1  direction according to the rotation of the middle gear  60 . When the wheel housing  41  rotates, the forward wheel  43  may contact the floor. 
     The forward wheel  43  may receive power generated by the driving motor  27  through the power transmission mechanism, and rotate in the FR direction. Accordingly, the vacuum cleaner  1  may travel forward. 
     As shown in  FIGS. 10 and 11 , when the user grips the handle  17  and pulls the main frame  10  backward, the main frame  10  may slide backward (in an R direction) with respect to the base  20 . More specifically, the bracket  30  coupled with the main frame  10  may slide backward (in the R direction) with respect to the base  20 . 
     If the bracket  30  slides backward, the rack gear portion  32  of the bracket  30  may slide backward, and the middle gear  60  engaged with the rack gear portion  32  may rotate. 
     Since the pinion gear portion  42  of the wheel housing  41  is engaged with the middle gear  60 , the wheel housing  41  may rotate in a WR 2  direction according to the rotation of the middle gear  60 . When the wheel housing  41  rotates, the reverse wheel  44  may contact the floor. 
     The reverse wheel  44  may receive power generated by the driving motor  27  through the power transmission mechanism, and rotate in the RR direction. Accordingly, the vacuum cleaner  1  may travel backward. 
       FIGS. 12 and 13  illustrate a slider crank mechanism of a vacuum cleaner according to another embodiment of the present disclosure. Hereinafter, the vacuum cleaner  1  according to the other embodiment of the present disclosure will be described with reference to  FIGS. 12 and 13 . The same components as in the above-described embodiment will be assigned like reference numerals, and detailed descriptions thereof will be omitted. 
     In the above-described embodiment, sliding of the main frame  10  may be converted into rotation of the wheel assembly  40  by engagement of the rack gear portion  32  of the bracket  30  with the pinion gear portion  42  of the wheel housing  41 . However, various mechanical structures capable of converting sliding into rotation, other than the rack-pinion structure, may be applied to the vacuum cleaner  1 . 
     For example, the vacuum cleaner  1  may include a slider crank mechanism configured to convert sliding of the main frame into rotation of the wheel assembly  40 . 
     The slider crank mechanism may include the bracket  30  configured to be slidable with respect to the base  20 , a first joint  241  disposed in the bracket  30 , a second joint  242  disposed in the wheel housing  41  of the wheel assembly  40 , and a link  245  connecting the first joint  241  to the second joint  242 . 
     One end of the link  245  may be coupled with the first joint  241 , wherein the one end of the link  245  may rotate idly on the first joint  241 , and the other end of the link  245  may be coupled with the second joint  242 , wherein the other end of the link  245  may rotate idly on the second joint  242 . 
     The wheel housing  41  may be coupled with the base  20  in such a way to be rotatable on a rotating shaft  243  with respect to the base  20 . 
     Through the above-described structure, when the main frame  10  moves forward in the F direction, as shown in  FIG. 12 , the bracket  30  may move forward, and the link  245  may pull the wheel housing  41 . Accordingly, the wheel assembly  40  may rotate in the WR 1  direction. When the main frame  10  moves backward in the R direction, the bracket  30  may move backward, and the link  245  may push the wheel housing  41 . Accordingly, the wheel assembly  40  may rotate in the WR 2  direction. 
     According to the embodiments of the present disclosure, because the wheels of the vacuum cleaner  1  may move forward/backward or turn according to a user&#39;s intention, it is possible to improve convenience in operation. 
     According to the embodiments of the present disclosure, because the wheel driver of the vacuum cleaner  1  may be implemented without adding a sensor or a control circuit, manufacturing costs may be reduced. 
     Although a few embodiments of the present disclosure have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the disclosure, the scope of which is defined in the claims and their equivalents. Although the present disclosure has been described with various embodiments, various changes and modifications may be suggested to one skilled in the art. It is intended that the present disclosure encompass such changes and modifications as fall within the scope of the appended claims.