Patent Publication Number: US-2006005344-A1

Title: Self-propelled cleaner and suspension mechanism

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a self-propelled cleaner which performs cleaning by traveling autonomously and a suspension mechanism for a drive wheel that is provided on the self-propelled cleaner.  
      2. Description of the Related Art  
      Conventionally, there have been known self-propelled cleaners that perform cleaning by traveling autonomously based on predetermined traveling patterns in rooms.  
      The self-propelled cleaner of this type has, for example, two drive wheels which are provided along a direction which intersects with a traveling direction thereof at right angles and is adapted to perform cleaning a traveling surface such as a floor while traveling in predetermined directions by driving the drive wheels so provided.  
      As the self-propelled cleaners, there have been known self-propelled cleaners having a suspension mechanism for damping vertical motions of the drive wheels relative to the self-propelled cleaner which are generated based on impacts and vibrations given to the drive wheel during traveling (for example, refer to JP-A-2001-525567 and JP-A-2002-360480). As the suspension mechanism, to be more specific, there have been known suspension mechanisms comprising a spring member (an elastic body) for pressing (biasing) drive wheels which constitute a drive unit together with a drive motor and a speed reduction mechanism such as gears against the side of a traveling surface of a self-propelled cleaner (for example, refer to JP-A-2003-033310 and JP-A-2004-016385).  
     SUMMARY OF THE INVENTION  
      In the case of the suspension mechanisms disclosed in JP-A-2003-033310 and JP-A-2004-016385, however, there has been caused a problem that the damping of the vertical motions of the drive wheels relative to the self-propelled cleaner which occur during the traveling thereof cannot be implemented in a preferred fashion, and hence the traveling of the self-propelled cleaner cannot be implemented properly.  
      Namely, in the case of the suspension mechanism disclosed in JP-A-2003-033310, since a drive unit is configured rotatably about a rotational shaft provided forward of drive wheels in an advancing direction of the self-propelled cleaner, mechanical malfunctions attributed to manufacturing and assembling errors tend to be generated easily, and the ground contact properties of the drive wheels are reduced, whereby the self-propelled cleaner cannot travel properly. In addition, in the case of the suspension mechanism disclosed in JP-A-2004-016385, a drive unit (a traveling portion) is mounted via a compression spring that is provided in a direction in which a compression direction (extension and contraction direction) thereof becomes substantially normal to a traveling surface of the self-propelled cleaner. Due to this, for example, in the event that an impact is applied obliquely to the drive wheels from the front during traveling, since the direction in which the impact is applied to the drive wheel is different from the extension and contraction direction of the compression spring, the compression spring is not allowed to extend and contract (to be compressed) properly, whereby the damping power of impact is reduced, and hence the following properties of the drive wheels to the traveling surface are reduced. In particular, in the event that the suspension mechanism includes a guide member for guiding the traveling direction of the drive wheel, since the extension and contraction direction of the compression spring is restricted by the guide member, the frictional resistance is increased, whereby the drive wheels cannot move vertically in a smooth fashion.  
      The present invention provides a self-propelled cleaner and a suspension mechanism which damp properly impact applied to the drive wheels and increase the ground contact properties of the drive wheels relative to the traveling surface.  
      According to a first aspect of the invention, there is provided a self-propelled cleaner that performs cleaning by traveling autonomously, the self-propelled cleaner including: a cleaner main body; a drive unit that includes a drive wheel, a drive source for rotating the drive wheel, and a transmission mechanism that transmits a driving force of the drive source to the drive wheel, being integrally provided with each other; a supporting member that supports the drive unit and is fixedly mounted on the cleaner main body; a biasing member that biases the drive unit towards a traveling surface of the self-propelled cleaner; a first and a second linking members that connects the drive unit to the supporting member at two different points, respectively, wherein the drive unit includes: a unit-side primary connecting portion to which the first linking member is connected, the unit-side primary connecting portion being provided at a position coaxial with a rotational shaft of the drive wheel; and a unit-side secondary connecting portion to which the second linking member is connected, the unit-side secondary connecting portion being provided at a position upward of the unit-side primary connecting portion, and at a position that is substantially superposed on the unit-side primary connecting portion in substantially a normal direction relative to the traveling surface, wherein the supporting member includes: a supporting member-side primary connecting portion to which the first linking member is connected; and a supporting member-side secondary connecting portion to which the second linking member is connected, the supporting member-side secondary connecting portion being provided at a position upward of the supporting member-side primary connecting portion and at a position that is substantially superposed on the supporting member-side primary connecting portion in substantially a normal direction relative to the traveling surface, wherein the supporting member is provided at a position that is displaced in an advancing direction of the self-propelled cleaner with respect to a rotational shaft of the drive wheel, and wherein the biasing member is provided on the supporting member and biases the drive unit via at least either one of the first linking member and the second linking member.  
      According to a second aspect of the invention, there is provided a suspension mechanism of a drive wheel to be mounted on a cleaner main body of a self-propelled cleaner that performs cleaning by traveling autonomously, the suspension mechanism including: a drive unit that includes the drive wheel, a drive source for rotating the drive wheel, and a transmission mechanism that transmits a driving force of the drive source to the drive wheel, being integrally provided with each other; a supporting member that supports the drive unit and is fixedly mounted on the cleaner main body; a biasing member that biases the drive unit towards a traveling surface of the self-propelled cleaner; a first and a second linking members that connects the drive unit to the supporting member at two different points, respectively. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      In the accompanying drawings:  
       FIG. 1  is a side view of a self-propelled cleaner which will be illustrated as a preferred embodiment to which the invention is applied, resulting when the self-propelled cleaner is viewed from a side thereof;  
       FIG. 2  is a plan view showing the self-propelled cleaner in  FIG. 1 ;  
       FIG. 3  is a front view of the self-propelled cleaner shown in  FIG. 1 ;  
       FIG. 4  is a block diagram illustrating the configuration of a main part of the self-propelled cleaner shown in  FIG. 1 ;  
       FIG. 5  is a drawing which describes an example of a suspension mechanism provided on the self-propelled cleaner shown in  FIG. 1 ; and  
       FIG. 6  is a drawing which describes the example of the suspension mechanism provided on the self-propelled cleaner shown in  FIG. 1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Embodiments of the present invention will be explained with reference to the drawings hereinafter.  
       FIG. 1  is a side view of a self-propelled cleaner which will be illustrated as a preferred embodiment to which the invention is applied, resulting when the self-propelled cleaner is viewed from a side thereof,  FIG. 2  is a plan view showing the self-propelled cleaner, and  FIG. 3  is a front view of the self-propelled cleaner. In addition,  FIG. 4  is a block diagram illustrating the configuration of a main part of the self-propelled cleaner.  
      Note that in FIGS.  1  to  3 , states within a housing  1  of a self-propelled cleaner  100  are shown which would result when the interior of the housing were seen through the housing, and respective constituent elements provided within the housing  1  are to be shown by broken lines.  
      In addition, in the following description, a direction along a traveling direction of the self-propelled cleaner  100  is regarded as a longitudinal direction X, and an advancing direction side is regarded as front, whereas a reversing direction side as rear. Furthermore, one direction which intersects with the longitudinal direction X at right angles is regarded as a transverse direction Y, and a direction which intersects with both the longitudinal direction X and the transverse direction Y is regarded as a vertical direction Z.  
      The self-propelled cleaner  100  is such as to perform cleaning by traveling autonomously based on predetermined traveling patterns within, for example, a room, and is externally formed into a disk-like shape as shown in FIGS.  1  to  3 . In the interior of the housing  1 , there are provided a traveling portion  2  for moving the self-propelled cleaner  100  in predetermined directions by driving to rotate two left and right drive wheels  21 L,  21 R and a cleaning portion  3  for cleaning a surface to be cleaned which is a traveling surface so as to get the surface free of dirt and dust. Additionally, the self-propelled cleaner  100  has, as shown in  FIG. 4 , a control unit  4 , a memory  5 , a RAM  6  and a CPU  7 , which are connected by a bus  8 .  
      The memory  5  may be configured as, for example, a ROM (Read Only Memory) or an EEPROM (Electronic Erasable Programmable ROM) and is designed to store various types of programs which are executed under control by the CPU  7  and data related to the process of the respective programs. To be specific, the memory  5  stores traveling pattern information on predetermined traveling patterns of the self-propelled cleaner  100  which are set in advance.  
      The RAM (Random Access Memory)  6  is, for example, a volatile semiconductor memory and makes up a storage area and a work area of the programs and data read out from the memory  5  under control of the CPU  7 .  
      The CPU (Central Processing Unit)  7  is such as to uniformly control the respective components making up the self-propelled cleaner  100  and reads out the predetermined programs stored in the memory  5  so as to deploy them in the work area of the RAM  6  to thereby execute various types of processing according to the programs so read out and deployed.  
      The control unit  4  has, for example, a plurality of keys (not shown) for indicating the execution of various types of functions of the self-propelled cleaner  100  and outputs to the CPU  7  a predetermined signal which corresponds to a control key operated by the user.  
      The traveling portion  2  is configured to include the two drive wheels  21 L,  21 R which are provided at both end portions of a bottom portion of the self-propelled cleaner  100  as viewed in the transverse direction Y but at a central portion of the bottom portion as viewed in the longitudinal direction X, a left wheel drive portion  22  and a right wheel drive portion  23  which drive to rotate independently the drive wheels  21 L,  21 R, respectively, a predetermined number of follower wheels (in  FIG. 2 , five wheels are shown) which rotate passively in association with the traveling of the self-propelled cleaner  100 , proximity sensors  25  for detecting an obstacle (not shown) such as a wall or a piece of furniture which exists on a side to which the self-propelled cleaner  100  is traveling, lateral wall proximity sensors  26  for detecting an obstacle (not shown) such as a lateral wall which exists in the transverse direction of the self-propelled cleaner  100 , a primary flow sensor  27  and a secondary flow sensor  28  which sense an air flow and detect the velocity thereof and level difference detecting sensors  29  for detecting a difference in level such as irregularities existing on a traveling surface.  
      The left drive wheel  21 L is provided rotatably around, for example, an axial center extending in the transverse direction Y. In addition, a rotary encoder  211 L is provided on the left drive wheel  21 L for outputting a rotational signal as the left drive wheel  21 L is driven to rotate.  
      The left wheel drive portion  22  includes, for example, a left wheel drive motor  221  as a drive source for driving to rotate the left drive wheel  21 L under control of the CPU  7  and a driving force transmission portion (which will be described later on) for transmitting the driving force of the left wheel drive motor  221  to the left drive wheel  21 L, and the left wheel drive portion  22  makes up a left wheel side drive unit  2 L together with the left drive wheel  21 L.  
      Hereinafter, the left wheel side drive unit  2 L will be described in detail by reference to  FIGS. 5 and 6 .  
       FIGS. 5 and 6  are drawings which describe an example of a suspension mechanism which is made to include the left wheel side drive unit  2 L, in which  FIG. 6  illustrates a state in which the left wheel side drive unit  2 L, which is in a state shown in  FIG. 5 , is rotated upward.  
      As shown in  FIGS. 5 and 6 , the left wheel side drive unit  2 L is supported on a supporting member  210  which is fixedly mounted on the cleaner main body via a first linking member  220  and a second linking member  230  in such a state that the left wheel side drive unit  2 L is biased to the side of the traveling surface of the self-propelled cleaner  100  by a torsion coil spring (a biasing member)  222 , whereby a suspension mechanism for the left drive wheel  21 L is configured.  
      In addition, the left wheel side drive unit  2 L includes as a driving force transmission portion (transmission mechanism), a gear box  240  which accommodates primary and tertiary gears  251  to  253  so as transmit the driving force of the left wheel drive motor  221  to the left drive wheel  21 L via the primary to tertiary gears  251  to  253 . Namely, the left wheel drive motor  221  is fixedly mounted in the gear box  240 , and the primary gear  251  is brought into mesh engagement with an output shaft of the left wheel drive motor  221 . Furthermore, the secondary gear  252  is made to mesh with the primary gear  251 , and the tertiary gear  253 , whose center shaft is provided coaxially with a rotational shaft of the left drive wheel  21 L, is made to mesh with the secondary gear  252 .  
      A unit-side primary connecting portion  241 , to which one end portion of the first linking member  220  is rotatably connected, is provided coaxially with the center shaft of the tertiary gear  253  and the rotational shaft of the left drive wheel  21 L.  
      In addition, the gear box  240  includes an extension  243  formed by being extended from an upper end portion of the gear box  240  towards a front of the self-propelled cleaner  100 , and a unit-side secondary connecting portion  242 , to which one end portion of the second linking member  230  is rotatably connected, is provided on the extension  243  at a position which is substantially superposed on the unit-side primary connecting portion  241  in a vertical direction (a direction substantially normal to the traveling surface) Z. Namely, the unit-side secondary connecting portion  242  is provided upward of the unit-side primary connecting portion  241 .  
      In addition, the supporting member  210  is provided a position which deviates forward of the rotational shaft of the left drive wheel  21 L in an advancing direction of the self-propelled cleaner  100 .  
      Furthermore, the supporting member  210  is a member which is formed substantially long along a direction which is substantially normal to the traveling surface, and a supporting member-side primary connecting portion  211 , to which the other end of the first linking member  220  is connected, is provided on a lower portion thereof. In addition, a supporting member-side secondary connecting portion  212 , to which the other end portion of the second linking member  230  is connected, is provided on an upper portion of the supporting member  210  at a position which is substantially superposed on the supporting member-side primary connecting portion  211  in the vertical direction (the direction substantially normal to the traveling surface) Z.  
      A coil spring  222  is supported coaxially with a rotational shaft of the supporting member-side secondary connecting portion  212  in such a manner that a portion that is wound into a coil constitutes a fulcrum, and an end portion thereof is fixed to a spring fixing portion  213  provided below the supporting member-side secondary connecting portion  212 , whereby the second linking member  230  is put into such a state that the second linking member  230  is biased to the side of the traveling surface by a portion of the torsion coil spring  222  which is provided in such a manner as to extend along an upper side of the second linking member  230 .  
      Substantially similar to the left drive wheel  21 L, the right drive wheel  21 R is provided rotatably around, for example, an axial center extending in the transverse direction. In addition, a rotary encoder  211 R is provided on the right drive wheel  21 R for outputting a rotational signal as the right drive wheel  21 R is driven to rotate.  
      The right wheel drive portion  23  is configured substantially the same as the left wheel drive portion  22  and includes, for example, a right wheel drive motor  231  as a drive source for driving to rotate the right drive wheel  21 R under control of the CPU  7  and a driving force transmission portion for transmitting the driving force of the right wheel drive motor  231  to the right drive wheel  21 R, and the right wheel drive portion  23  makes up a right wheel side drive unit  2 R together with the right drive wheel  21 R.  
      Note that since the right side drive unit  2 R is configured substantially the same as the left wheel side drive unit  2 L, the detailed description thereof will be omitted.  
      The predetermined number of follower wheels  24  are provided at predetermined positions in consideration of a longitudinal weight balance with the drive wheels  21 L,  21 R of the self-propelled cleaner  100  constituting the center of the same cleaner in order to increase the traveling stability in accordance with the rotational driving of the drive wheels  21 L,  21 R.  
      The plurality of proximity sensors  25  are, for example, infrared sensors or ultrasonic sensors and are provided in such a manner that distal end portions of the respective proximity sensors  25  are exposed via a plurality of openings provided in a front side of the housing  1 .  
      In addition, the proximity sensors  25  are designed to output to the CPU  7  obstacle detection signals for detecting an obstacle such as a wall and a piece of furniture that exists within a predetermined range of the self-propelled cleaner  100  that resides on the advancing side thereof. Then, the CPU  7  is designed to detect an obstacle existing in the traveling direction of the self-propelled cleaner  100  by following the execution of a predetermined arithmetic program based on the input of obstacle detection signals outputted from the proximity sensors  25  during the traveling of the self-propelled cleaner  100 .  
      Substantially similar to the proximity sensors  25 , the lateral wall proximity sensors  26  are, for example, infrared sensors or ultrasonic sensors and are provided in such a manner that distal end portions of the respective lateral wall proximity sensors  26  are exposed, respectively, via two openings provided laterally outward of the left and right drive wheels  21 L,  21 R in lateral end portions of the housing  1 .  
      In addition, the lateral wall proximity sensors  26  are designed to output to the CPU  7  obstacle detection signals for detecting an obstacle such as a wall and a piece of furniture which exists in the lateral direction Y which intersects with the advancing direction substantially at right angles and resides within a predetermined. Then, the CPU  7  is designed to detect an obstacle existing in the reversing direction of the self-propelled cleaner  100  by following the execution of a predetermined arithmetic program based on the input of obstacle detection signals outputted from the proximity sensors  26 .  
      The primary flow sensor  27  and the secondary flow sensor  28  are provided at substantially a central portion on an upper surface of the self-propelled cleaner  100 . To be specific, the primary flow sensor  27  and the secondary flow sensor  28  are provided in such a manner as to be oriented in predetermined directions with detecting portions of the respective sensors being exposed from the housing  1  so that the primary flow sensor  27  can detect an air flow which flows in advancing directions according to the predetermined traveling patterns, whereas the secondary flow sensor  28  can detect an air flow which flows in a direction which intersects with the advancing direction at right angles.  
      While the self-propelled cleaner  100  is traveling (moving), the primary flow sensor  27  is designed to output to the CPU  7  a primary flow velocity signal which relates to the flow velocity of the air flow which flows in the advancing direction, and the secondary flow sensor  28  is designed to output to the CPU  7  a secondary flow velocity signal which relates to the flow velocity of the air flow which flows in the direction that intersects with the advancing direction at right angles. To be more specific, the primary flow sensor  27  and the secondary flow sensor  28  include, for example, temperature detecting portions such as micro sensors and detect temperatures reduced by air flows generated during the traveling of the self-propelled cleaner  100  at the temperature detecting portions so as to thereafter compute flow velocities of the respective air flows which flow in the advancing direction and the direction which intersects with the advancing direction at right angles or a then traveling speed of the self-propelled cleaner  100 , the flow velocities or the traveling speed having a predetermined relationship with the degree of reduction in detected temperatures, for output to the CPU  7  as a primary flow velocity signal and a secondary flow velocity signal.  
      Here, when at least either of the primary flow velocity signal outputted from the primary flow sensor  27  and the secondary flow velocity signal outputted from the secondary flow sensor  28  is inputted into the CPU  7 , the CPU  7  is designed to execute a predetermined arithmetic program based on at least either of the primary flow velocity signal and the secondary flow velocity signal to detect a traveling direction of the self-propelled cleaner  100 . Note that the CPU  7  is designed to execute a predetermined program based on the traveling direction so detected to thereby control the driving of the left wheel drive motor  221  and the right wheel drive motor  231  so as to move the self-propelled cleaner  100  in accordance with the predetermined traveling patterns.  
      Substantially similar to the proximity sensors  25  and the lateral wall proximity sensors  26 , the level difference detecting sensors  29  are made up of infrared sensors or ultrasonic sensors and are provided at a front end portion of the bottom portion and in front of the left and right drive wheels  21 L,  21 R in such a state that distal end portions thereof are oriented towards the traveling surface. In addition, the level difference detecting sensors  29  are designed to output to the CPU  7  level difference signals for detecting level differences that exist on the traveling surface.  
      The cleaning portion  3  includes a cleaning brush  31  stirs up dirt and dust on the cleaning surface (traveling surface), a suction fan  33  that is driven to collect dirt and dust on the cleaning surface via a suction port  32 , a dust collecting portion  35  which communicates with the suction port  32  via a communication portion  34  and into which dirt and dust so sucked via the suction port  32  are collected and side cleaning brushes  36  for cleaning portions of the cleaning surface which exist laterally outward of the cleaning brush  31 .  
      The cleaning brush  31  is designed to rotate around an axial center extending in the lateral direction Y based on the rotational driving of a brush drive motor  311  under control of the CPU  7 . In addition, the suction port  32  is provided back of the cleaning brush  31 .  
      The suction port  32  is provided at substantially a central portion as viewed in a longitudinal direction of the cleaning brush  31  and is connected to a rear end portion of the dust collecting portion  35  via the communication portion  34 .  
      The suction fan  33  is made to communicate with a front end portion of the dust collecting portion  35  via a filter  37  and is rotatably based on the rotational driving of a fan drive motor  331  under control of the CPU  7 .  
      The side cleaning brushes  36  are provided, respectively, in front of the left and right drive wheels  21 L,  21 R in such a manner as to partially protrude laterally outward of the housing  1 . Namely, the side cleaning brushes  36  are designed to rotate around axial centers provided in the vertical direction Z at edge portions of the housing  1  based on the rotational driving of a side brush driving motors  361  under control of the CPU  7 . Consequently, part or, for example, substantially half of the side cleaning brush  36  is made to be positioned outward of the housing  1  so that the portions of the cleaning surface that exist laterally outward of the cleaning brush  31  are cleaned of dirt and dust existing thereon.  
      As described above, according to the self-propelled cleaner  100  of the embodiment of the invention, since the drive units  2 L,  2 R, which are configured to be integrated with the drive wheels  21 L,  21 R, the drive motors  221 ,  231  and the primary to tertiary gears  251  to  253  with each other, are biased to the side of the traveling surface of the self-propelled cleaner  100  by the torsion coil springs  222 ,  232  and are connected to the supporting member  210  via the first linking member  220  and the second linking member  230 , the damping of impact applied to the drive wheels  21 L,  21 R can be performed properly to thereby increase the ground contact properties of the drive wheels  21 L,  21 R. Namely, since the drive units  2 L,  2 R can be rotated about the rotational shafts of the first linking member  220  and the second linking member  230 , respectively, an impact applied to the drive wheels  21 L,  21 R during the traveling of the self-propelled cleaner  100  can be dispersed in a preferred fashion via the rotating shafts of the first linking member  220  and the second linking member  230 , and the damping of the impact so applied can be performed properly by the torsion coil springs  222 ,  232 , whereby the drive wheels  21 L,  21 R are allowed to follow the traveling surface more properly, thereby making it possible to increase the ground contact properties of the drive wheels  21 L,  21 R. Consequently, the self-propelled cleaner  100  is allowed to travel properly.  
      In addition, since the unit-side primary connecting portion  241  to which the first linking member  220  is connected and the unit-side secondary connecting portion to which the second linking member  230  is connected are provided on each of the drive units  2 L,  2 R at the positions where both the connecting portions are substantially superposed on each other in the vertical direction Z, the rotation of the drive units  2 L,  2 R via the first linking member  220  and the second linking member  230  is implemented more properly, whereby the damping of impact can be implemented more properly.  
      Furthermore, since the supporting member-side primary connecting portion  211  to which the first linking member is connected and the supporting member-side secondary connecting portion  212  to which the second linking member  230  is connected are provided on the supporting member  210  at the positions where both the connecting portions are substantially superposed on each other in the vertical direction Z, the rotation of the drive units  2 L,  2 R is performed more properly, whereby the damping of impact can be performed more properly. In addition, since the supporting member  210  is provided at the position which deviates forward of the rotational shafts of the drive wheels  21 L,  21 R in the advancing direction of the self-propelled cleaner  100 , the damping of an impact that is applied obliquely to the drive wheels  21 L,  21 R from the front while the self-propelled cleaner  100  is advancing can be implemented properly.  
      Furthermore, since the torsion coil springs  222 ,  232  are provided on the supporting member  210  so as to bias the drive units  2 L,  2 R via the second linking member  230 , an impact applied to the drive wheels  21 L,  21 R can be dampened more properly via the second linking member  230  than a case where the drive units  2 L,  2 R are biased directly to the side of the traveling surface by the torsion coil springs  222 ,  232 .  
      Note that the invention is not limited to the embodiment that has been described heretofore but may be improved and modified with respect to design thereof in various ways without departing from the spirit and scope of the invention.  
      For example, while in the embodiment, the construction is illustrated in which the drive wheels are biased to the side of the traveling surface by the torsion coil springs  222 ,  232  as the biasing members via the second linking member  230 , the invention is not limited thereto, and the drive wheels may be so biased via the first linking member  220  or via both the first linking member  220  and the second linking member  230 .  
      In addition, the positions of the unit-side primary connecting portion  241  and the unit-side secondary connecting portion  242 , the positions of the supporting member-side primary connecting portion  211  and the supporting member-side secondary connecting portion  212  and the lengths of the first linking member  220  and the second linking member  230  may be modified arbitrarily as  
      As described above with reference to the accompanying drawings, there is provided a self-propelled cleaner ( 100 ) for performing cleaning by traveling autonomously. The self-propelled cleaner includes a suspension mechanism for a drive wheel (for example, a left drive wheel  21 L, a right drive wheel  21 R) which is adapted to be mounted on a cleaner main body of the self-propelled cleaner. The suspension mechanism includes a drive unit (for example, a left wheel side drive unit  2 L a right wheel side drive unit  2 R) made up by integrating the drive wheel, a drive source (for example, a left wheel drive motor  221 , a right wheel drive motor  231 ) for driving to rotate the drive wheel and a driving force transmission portion (for example, primary to tertiary gears  251  to  253 ) for transmitting a driving force of the drive source to the drive wheel with each other; and a supporting member ( 210 ) fixedly mounted on the cleaner main body at a position which deviates forward of a rotational shaft of the drive wheel in an advancing direction of the self-propelled cleaner and which is adapted to support the drive unit. The drive unit is connected to the supporting member via a first linking member ( 220 ) rotatably mounted on a unit-side primary connecting portion ( 241 ) provided coaxially with the rotational shaft of the drive wheel of the drive unit and a supporting member-side primary connecting portion ( 242 ) of the supporting member and a second linking member ( 230 ) rotatably mounted on a unit-side secondary connecting portion ( 212 ) provided upward of the unit-side primary connecting portion of the drive unit and at a position which is substantially superposed on the unit-side primary connecting portion in substantially a normal direction relative to a traveling surface of the self-propelled cleaner and a supporting member-side secondary connecting portion provided upward of the support side primary connecting portion of the supporting member and at a position which is substantially superposed on the supporting member-side primary connecting portion in substantially the normal direction relative to the traveling surface and being biased to the side of the traveling surface of the self-propelled cleaner by a biasing member (for example, torsion coil springs  222 ,  232 ) provided on the supporting member via at least either of the first linking member and the second linking member.  
      According to the self-propelled cleaner, since the drive unit which is made up by integrating the drive wheel, the drive source and the driving force transmission portion with each other is biased to the side of the traveling surface of the self-propelled cleaner by the biasing member and is connected to the supporting member via the first linking member and the second linking member, impact applied to the drive wheel can be damped properly, whereby the ground contact properties of the drive wheel to the traveling surface can be increased. Namely, since the drive unit can be rotated about the rotational shafts of the first linking member and the second linking member, for example, an impact applied to the drive wheel while the self-propelled cleaner is traveling can be dispersed in a preferred fashion via the rotational shafts of the first linking member and the second linking member, and the impact can be dampened properly by the biasing member, whereby the drive wheel is allowed to follow the traveling surface in a more proper fashion, thereby making it possible to increase the ground contact properties of the drive wheel.  
      Since a unit-side primary connecting portion to which the first linking member is connected and a unit-side secondary connecting portion to which the second linking member is connected are provided on the drive unit at a position where they are superposed on each other in substantially a normal direction relative to the traveling surface, the rotation of the drive unit via the first linking member and the second linking member is performed more properly so as to damp the impact more properly.  
      Furthermore, since a supporting member-side primary connecting portion to which the first linking member is connected and a supporting member-side secondary connecting portion to which the second linking member is connected are provided on the supporting member at a position where they are superposed on each other in substantially the normal direction relative to the traveling surface, the rotation of the drive unit via the first linking member and the second linking member is performed more properly so as to damp the impact more properly.  
      In addition, since the supporting member is provided at a position which deviates forward of the rotational shaft of the drive wheel in an advancing direction of the self-propelled cleaner, an impact that is applied obliquely to the drive wheel from the front while the self-propelled cleaner is advancing can be damped more properly.  
      Furthermore, since the biasing member is provided on the supporting member for biasing the drive unit via at least either of the first linking member and the second linking member, impact applied to the drive wheel can be damped more properly via the first linking member and the second linking member when compared with a case where the drive unit is directly biased to the side of the traveling surface by the biasing member.  
      According to the suspension mechanism, the same advantages can be obtained as those provided by the self-propelled cleaner.  
      According to the self-propelled cleaner, impact applied to the drive wheel can be dispersed in a preferred fashion via the first linking member and the second linking member, and the impact so applied can be damped properly by the biasing means, whereby the drive wheel is allowed to follow the traveling surface more properly, thereby making it possible to increase the ground contact properties of the drive wheel.  
      According to the suspension mechanism, impact applied to the drive wheel can be dispersed in a preferred fashion via the first linking member and the second linking member, and the impact so applied can be damped properly by the biasing means, whereby the drive wheel is allowed to follow the traveling surface more properly, thereby making it possible to increase the ground contact properties of the drive wheel.  
      Although the present invention has been shown and described with reference to the embodiment, various changes and modifications will be apparent to those skilled in the art from the teachings herein. Such changes and modifications as are obvious are deemed to come within the spirit, scope and contemplation of the invention as defined in the appended claims.