Patent Publication Number: US-2023145580-A1

Title: Robot cleaner

Description:
TECHNICAL FIELD 
     The present disclosure relates to a robot cleaner that detects a collision of a bumper using a cliff sensor. 
     BACKGROUND ART 
     In general, robots have been developed for industrial use and have been part of factory automation. In recent years, the field of application of robots has been further expanded, and not only aerospace robots and medical robots, but also household robots that can be used in general households are being made. 
     A typical example of a household robot is a robot cleaner. A robot cleaner performs a vacuum cleaning function that sucks dust and foreign matter from a floor while performing autonomous driving in a predetermined region or a mop cleaning function through mopping. Such a robot cleaner is generally provided with a rechargeable battery, and an obstacle detection sensor that can avoid an obstacle while driving to clean while performing autonomous driving. 
     In some cases, the robot cleaner is unable to avoid an obstacle while driving to collide with the obstacle. In order to detect a collision with an obstacle, a cleaner body is provided with a collision detection portion including a bumper configured to be movable inwardly when in contact with the obstacle, and a detection element that detects the inward movement of the bumper. 
     US 2007/0017061 A1 (published on Jan. 25, 2007; hereinafter, Patent Document 1) discloses a steering control sensor for a robot cleaner that is driven to change steering when reaching an end of a floor surface or encountering an obstacle while driving. 
     The steering control sensor is mounted on a front bottom surface of the robot cleaner. The steering control sensor includes a contact member accommodated in a casing and elastically supported by a spring to be movable, and a photo sensor selectively exposed according to the movement of the contact member. 
     The contact member is movable between an open position and a closed position. When the contact member moves to the open position, the photo sensor may detect light reflected from the bottom surface through a through hole. 
     When the robot cleaner encounters an obstacle in front to move the contact member to the closed position by an external pressure, the contact member may block the light reflected from the floor surface and the photo sensor may not receive a signal of the reflected light, thereby allowing the robot cleaner to recognize a collision with the obstacle. 
     In Patent Document 1, a contact member is integrated with a bumper, and a sensor may recognize a bumping operation when the bumper is sufficiently retracted by an effective distance. 
     However, when the bumper is not retracted by the effective distance, there is a problem in that the sensor does not recognize the bumping operation. 
     In addition, WO 2018/169180 A1 (published on Sep. 20, 2018; hereinafter, Patent Document 2) discloses a robot cleaner. 
     The robot cleaner of Patent Document 2 includes a bumper configured to be movable inwardly by an external force, and a cliff sensor that detects a terrain below. The cliff sensor includes a light emitting portion and a light receiving portion, and the controller is configured to measure a time at which light irradiated downward from the light emitting portion is received by the light receiving portion to detect the terrain below. 
     In Patent Document 2, the bumper may be disposed to cover the cliff sensor in a state in which the bumper is moved inward by an external force, thereby allowing the cliff sensor to recognize a bumping operation of the bumper. 
     However, there is a problem in that the sensor is unable to recognize the bumping operation when the bumper is not sufficiently retracted by an effective distance. 
     Therefore, in both Patent Documents 1 and 2, there is a need to improve the sensitivity of the sensor in recognizing the bumping operation. 
     DISCLOSURE OF INVENTION 
     Technical Problem 
     The present disclosure is contrived to solve the problems of the related art, and a first aspect of the present disclosure is to provide a robot cleaner capable of providing a new collision detection structure, unlike a structure in which an inward movement of a bumper covers a cliff sensor as a collision detection element of the bumper. 
     Furthermore, a second aspect of the present disclosure is to provide a robot cleaner capable of improving the sensitivity of the bumper to collision detection. 
     In addition, a third aspect of the present disclosure is to provide a robot cleaner capable of improving the reliability of bumper to collision detection. 
     Solution to Problem 
     In order to achieve the foregoing objectives of the present disclosure, a robot cleaner according to the present disclosure may include a cleaner body provided with a controller, and a driving wheel the driving of which is controlled by the controller; a bumper mounted on a front surface portion of the cleaner body to be movable toward an inside of the cleaner body by an external force; a cliff sensor mounted on an inside of an opening portion that is open downward at a bottom portion of the cleaner body to detect a terrain below; and a shielding module disposed at the bottom portion of the cleaner body to detect a collision between the bumper and an obstacle, wherein the shielding module includes a cam coming in contact with a guide protrusion protruding inwardly from the bumper so as to be interlocked with the bumper, and rotatably mounted to the bottom portion of the cleaner body about a rotation shaft; and a cover plate rotatably mounted about the rotation shaft while maintaining a phase angle with the cam to selectively expose the cliff sensor. 
     According to an example associated with the present disclosure, the cover plate may reciprocally rotate between a first position disposed to expose the cliff sensor before a collision between the bumper and an obstacle and a second position disposed to cover the cliff sensor by an inward movement of the bumper after the collision, wherein the shielding module further includes an elastic element that restores the cover plate from the second position to the first position. 
     According to an example associated with the present disclosure, the elastic element may be disposed between the bumper and the opening portion to elastically push the cover plate such that the cover plate does not overlap the opening portion in a top-down direction. 
     According to an example associated with the present disclosure, the shielding module may further include an elastic element that restores the cover plate, which rotates according to the inward movement of the bumper, to an original position, wherein the elastic element is implemented as a spring. 
     According to an example associated with the present disclosure, the shielding module may further include an elastic element that restores the cover plate, which rotates according to the inward movement of the bumper, to an original position; and a mounting guide provided at a bottom portion of the cleaner body to guide the mounting of the shielding module, wherein one side of the elastic element is supported by a first fixing protrusion disposed on the mounting guide, and the other side of the elastic element is supported by a second fixing protrusion disposed on the cover plate. 
     According to an example associated with the present disclosure, the shielding module may further include a hinge portion hinge-coupled to the rotation shaft, and connected to the cam and the cover plate to support the cam and the cover plate. 
     According to an example associated with the present disclosure, the cam may include an inclined surface disposed to be inclined in a direction intersecting a front-rear direction and a left-right lateral direction with respect to a head-on or lateral collision between the bumper and the obstacle to make contact with the guide protrusion. 
     According to an example associated with the present disclosure, a distance between the center of the cover plate and the center of the rotation shaft may be configured to be greater than a distance between a contact point of the cam in contact with the guide protrusion and the center of the rotation shaft. 
     According to an example associated with the present disclosure, the shielding module may further include a mounting guide provided on a bottom surface of the cleaner body to guide the mounting of the shielding module. 
     According to an example associated with the present disclosure, the mounting guide may be provided with a guide hole that limits a movement range of the bumper, wherein the guide protrusion moves in a front-rear direction or a left-right direction while being accommodated in the guide hole according to an inward movement of the bumper. 
     According to an example associated with the present disclosure, the bumper may further include a protruding portion disposed to protrude from the bumper toward the mounting guide, wherein the mounting guide includes a first accommodating portion that accommodates the cover plate disposed not to overlap the opening portion in a top-down direction; and a second accommodating portion that accommodates the protruding portion to movably support the protruding portion. 
     According to an example associated with the present disclosure, the mounting guide may be disposed between the bumper and the opening portion, wherein the mounting guide may further include a partition wall extending in a direction intersecting an outside and an inside of the mounting guide to partition the first and second accommodation portions; a first shielding wall extending along an outer edge of the first accommodating portion from one end of the partition wall to open the first accommodating portion in a direction facing the cover plate; and a second shielding wall extending from the other end of the partition wall along an inner edge of the second accommodation portion to open the second accommodation portion in a direction facing the bumper. 
     According to an example associated with the present disclosure, the cliff sensor may include a light emitting portion that irradiates light to a lower side of the opening portion; and a light receiving unit that receives reflective light. 
     According to an example associated with the present disclosure, the shielding modules may be disposed symmetrically to each other on both left and right sides of the cleaner body with respect to a front-rear center line passing through the center of the cleaner body in a front-rear direction 
     According to an example associated with the present disclosure, the robot cleaner may further include a support portion that movably supports the bumper in a front-rear direction and a left-right lateral direction with respect to the cleaner body. 
     According to an example associated with the present disclosure, the bumper may further include an engaging hook disposed to protrude from an upper end of the bumper toward an inside thereof such that an upper end portion of the bumper is supported to be suspended on the support portion, wherein the support portion includes a support body extending along a front edge of the cleaner body to allow the engaging hook to be slidable; an engaging protrusion disposed to protrude from a front end of the support body to allow the engaging hook to be caught; and a plurality of fitting portions to allow the support body to be fit and coupled to the cleaner body. 
     According to an example associated with the present disclosure, the robot cleaner may include a brush module or a mop module mounted to be accommodated into the cleaner body, wherein the opening portion is disposed at a front side of the brush module or the mop module. 
     According to an example associated with the present disclosure, the robot cleaner may further include a mounting guide that guides the mounting of the shielding module, wherein the mounting guide is provided with a guide hole that limits a movement range of the guide protrusion, and the guide hole is disposed to be inclined from an outside of the mounting guide to an inside thereof rearward such that the guide protrusion pushes the cam rearward to rotate. 
     According to an example associated with the present disclosure, the cliff sensor may be disposed at a rear side of the guide hole. 
     According to an example associated with the present disclosure, the cam may include an inclined surface disposed to be inclined rearward from an inside of the mounting guide to an outside thereof to make contact with the guide protrusion. 
     Advantageous Effects of Invention 
     The effects of a robot cleaner according to the present disclosure will be described as follows. 
     First, a shielding module provided at a lower portion of a cleaner body provided separately from a bumper may selectively expose a cliff sensor in conjunction with an inward movement of the bumper, thereby detecting a collision between the bumper and an obstacle. 
     Second, the shielding module includes a cam and a cover plate that rotate with the same phase angle around the same rotation shaft. A distance between the center of the cover plate and the center of the rotation shaft is configured to be greater compared to a distance between a contact point of an inclined surface of the cam in contact with a guide protrusion of the bumper and the center of the rotation shaft. For this reason, a rotational movement speed of the cover plate that rotates to cover the cliff sensor is much faster than an inward movement speed of the bumper. Accordingly, a sensitivity between the bumper and the obstacle to collision detection using the cliff sensor is improved. 
     Third, a guide protrusion protruding from an inner surface of the bumper is provided on the bumper, and a shielding module has a guide hole for limiting a movement range of the guide protrusion. The guide hole is disposed to be inclined such that the guide protrusion is able to move on an inclined surface of the cam to a rear side thereof during a front collision of the bumper as well as a side collision of the bumper. As a result, the cover plate may be guided to cover the cliff sensor in all collision directions of the bumper, thereby enhancing the reliability of collision detection. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a perspective view showing an appearance of a robot cleaner according to the present disclosure. 
         FIG.  2    is a cross-sectional view taken along line II-II in  FIG.  1   . 
         FIG.  3    is a bottom view of  FIG.  1   . 
         FIG.  4    is a cross-sectional view taken along line IV-IV in  FIG.  3   . 
         FIG.  5    is an assembly view showing a shape in which a collision detection portion mounted on a front surface of a cleaner body in  FIG.  3    is viewed from a bottom surface. 
         FIG.  6    is an exploded view of a bumper, a support portion, a cliff sensor, and a shielding module (a mounting guide, a cover plate, a cam) in  FIG.  5   . 
         FIG.  7    is a bottom view showing the mounting guide in  FIG.  6   . 
         FIG.  8    is a bottom view showing the cover plate, the cam, and the rotation shaft in  FIG.  6   . 
         FIG.  9    is an enlarged conceptual view showing a shape in which the shielding module is mounted on a bottom surface of the cleaner body taken along line IX-IX in  FIG.  5   . 
         FIG.  10    is a conceptual view showing a shape in which a cover plate is at a first position to expose a cliff sensor before a collision between a bumper and an obstacle. 
         FIG.  11    is a cross-sectional view taken along line XI-XI in  FIG.  10   . 
         FIG.  12    is a conceptual view showing a shape in which the cover plate is at a second position to cover the cliff sensor after the bumper collides head-on with the obstacle in  FIG.  10   . 
         FIG.  13    is a cross-sectional view taken along line XIII-XIII in  FIG.  12   . 
         FIG.  14    is a conceptual view showing a shape in which the bumper is at a second position to cover the cliff sensor after the bumper in  FIG.  10    collides laterally with the obstacle. 
     
    
    
     MODE FOR THE INVENTION 
     Hereinafter, the embodiments disclosed herein will be described in detail with reference to the accompanying drawings, and the same or similar elements are designated with the same numeral references regardless of the numerals in the drawings and redundant description thereof will be omitted. A suffix “module” and “unit” used for constituent elements disclosed in the following description is merely intended for easy description of the specification, and the suffix itself does not give any special meaning or function. In describing the embodiments disclosed herein, moreover, the detailed description will be omitted when specific description for publicly known technologies to which the invention pertains is judged to obscure the gist of the present disclosure. Also, it should be understood that the accompanying drawings are merely illustrated to easily explain the concept of the invention, and therefore, they should not be construed to limit the technological concept disclosed herein by the accompanying drawings, and the concept of the present disclosure should be construed as being extended to all modifications, equivalents, and substitutes included in the concept and technological scope of the invention. 
     It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. The terms are used merely for the purpose to distinguish an element from the other element. 
     In case where an element is “connected” or “linked” to the other element, it may be directly connected or linked to the other element, but another element may be existed therebetween. On the contrary, in case where an element is “directly connected” or “directly linked” to the other element, it should be understood that any other element is not existed therebetween. 
     A singular representation may include a plural representation as far as it represents a definitely different meaning from the context. 
     Terms “include” or “has” used herein should be understood that they are intended to indicate the existence of a feature, a number, a step, a constituent element, a component or a combination thereof disclosed in the specification, and it may also be understood that the existence or additional possibility of one or more other features, numbers, steps, constituent elements, components or combinations thereof are not excluded in advance. 
       FIG.  1    is a perspective view showing an appearance of a robot cleaner according to the present disclosure. 
       FIG.  2    is a cross-sectional view taken along line II-II in  FIG.  1   . 
       FIG.  3    is a bottom view of  FIG.  1   . 
       FIG.  4    is a cross-sectional view taken along line IV-IV in  FIG.  3   . 
     The robot cleaner is configured to perform a function of cleaning a floor while performing autonomous driving in a predetermined region. Here, the cleaning of the floor may be understood as a concept including sucking dust and foreign matter on the floor or mopping the floor. 
     In this example, it is shown that the robot cleaner is configured to perform a vacuum cleaning function of sucking air from the floor and separating dust and foreign matter from the sucked air while performing autonomous driving in a predetermined region. 
     The robot cleaner is configured to include a cleaner body  100 . The cleaner body  100  defines the appearance of the cleaner. Various parts, including a controller for controlling the cleaner, are integrated or mounted in the cleaner body  100 . 
     A circuit board (not shown) constituting the controller may be disposed in the cleaner body  100 . Various modules, for example, a brush module  102  or a mop module (not shown) may be detachably coupled to the cleaner body  100 . 
     A driving wheel  104  is provided on a bottom surface of the cleaner body  100 . The driving wheel  104  is configured to rotate by receiving a driving force from a drive motor (not shown). The drive motor may receive a control signal from the controller to control its driving. 
     The driving wheels  104  may be provided on both left and right sides of the bottom surface of the cleaner body  100 , respectively. For independent driving of each driving wheel  104 , the drive motor may be connected to each driving wheel  104 . 
     The cleaner body  100  may be moved or rotated forward, backward, left, and right by the rotation of the driving wheel  104 . 
     An auxiliary wheel  105  may be additionally provided in the cleaner body  100 . The auxiliary wheel  105  may be distinguished from the driving wheel  104  in that it has only a rolling function for the floor. 
     The auxiliary wheel  105  may support the cleaner body  100  together with the driving wheel  104 . The auxiliary wheel  105  is configured to assist the driving of the cleaner body  100 . 
     The plurality of auxiliary wheels  105  may be rotatably provided at the front and rear centers of the cleaner body  100  around a lateral center line passing through the center of the plurality of driving wheels  104 . 
     A battery (not shown) that supplies power to the robot cleaner is mounted on the cleaner body  100 . The battery may be configured to be rechargeable, and configured to be detachable from a bottom surface portion of the cleaner body  100 . 
     A sensing unit  103  may be disposed on the cleaner body  100 . The sensing unit  103  may be disposed at a front side of the cleaner body  100 . The sensing unit  103  may be located at a predetermined height from a front surface of the cleaner body  100 . 
     The sensing unit  103  may be configured to detect an obstacle or a geographic feature in front to disallow the cleaner body  100  to collide with the obstacle using ultrasonic waves. 
     When the robot cleaner is configured to perform a vacuum cleaning function, air containing dust and foreign matter may be sucked through an opening disposed at a bottom portion of the cleaner body  100 . 
     A brush module  102  that sweeps up dust and foreign matter on the floor may be mounted in the opening. 
     When the brush module  102  is separated from the cleaner body  100 , the mop module may be detachably coupled to a bottom surface of the cleaner body  100  to replace the separated brush module  102 . 
     A user may selectively mount the brush module  102  or the mop module on the cleaner body  100  according to the purpose of cleaning. 
     The controller may recognize a module mounted on the cleaner body  100  to perform an operation corresponding thereto. 
     For example, when the brush module  102  is mounted on the cleaner body  100 , the controller may drive a motor and a fan to generate a suction force for sucking air from the floor. Furthermore, a rotation drive unit (not shown) may be driven to allow the brush module  102  connected to the rotation driving unit to sweep up dust and foreign matter on the floor. 
     When the mop module is mounted on the cleaner body  100 , the controller may drive the rotation drive unit. The mop module connected to the rotation drive unit is rotated by the driving of the rotation drive unit to wipe the floor. The controller controls not to drive the motor and the fan while the mop module is mounted on the cleaner body  100 . 
     Dust and foreign matter in the air sucked in through the brush module  102  are filtered and collected in a dust container (not shown), and the air from which the dust and foreign matter are separated is discharged to an outside of the cleaner body  100 . 
     A suction passage (not shown) that guides air flowing in through the opening to the dust container and an exhaust passage (not shown) that guides the flow of air from the dust container to an outside of the cleaner body  100  are disposed inside the cleaner body  100 . 
     The dust container may be detachably accommodated inside the cleaner body  100 . 
     The dust container may include at least one of a filter and a cyclone for filtering dust and foreign matter in the sucked air. 
     When the cleaner body  100  collides with an obstacle while driving, the collision may mainly occur at a front surface portion or both end portions of the left and right sides of the cleaner body  100 . 
     At a front side of the cleaner body  100 , a bumper  110  may be mounted on a front surface of the cleaner body  100  in order to mitigate an impact when colliding with an obstacle. 
     The bumper  110  may extend long along the left and right circumferences of the cleaner body  100  to cover the front surface and both end portions of the left and right sides of the cleaner body  100 . 
     The bumper  110  may extend in a top-down direction of the cleaner body  100 . The bumper  110  has a predetermined height. 
     A lower end of the bumper  110  may be located higher than a bottom surface of the cleaner body  100 . 
     An upper end of the bumper  110  may be located lower than the sensing unit  103 . 
     The bumper  110  may be formed of an elastic material to absorb shock when the cleaner body  100  collides with an obstacle. 
     The bumper  110  is configured to be movably supported in an inward direction of the cleaner body  100  by a support portion  120  when colliding with an obstacle. 
     The support portion  120  may support the bumper  110  such that the bumper  110  is movable in a front-rear direction of the cleaner body  100  with respect to the cleaner body  100 . 
     The bumper  110  may be mounted to be suspended while an upper end portion thereof is mounted on the support portion  120 . 
     To this end, an engaging hook  111  at an upper end of the bumper  110  may be disposed to protrude above the support portion  120 . A rear end portion of the engaging hook  111  may be defined in a downwardly bent shape to be caught by the support portion  120 . 
     According to this configuration, the engaging hook  111  may be prevented from being released from the support portion  120 . 
     The support portion  120  may be disposed between the bumper  110  and a front surface portion of the cleaner body  100 . The support portion  120  may be defined in a curved shape along the front surface portion and the left and right sides of the cleaner body  100 . 
     The support portion  120  may be configured to include a support body  121 , an engaging protrusion  122 , and a fitting portion  123 . 
     A rear end portion of the support body  121  is supported on a front surface portion of the cleaner body  100 , and the support body  121  may horizontally extend forward in a cantilever shape. 
     The engaging protrusion  122  is disposed to protrude upward from a front end of the support body  121  such that the engaging hook  111  is caught. The engaging protrusion  122  may extend long along left and right circumferences of the support portion  120 . 
     A protruding length of the engaging hook  111  may be disposed to correspond to that of the support body  121 . 
     At least part of the engaging hook  111  is disposed to overlap the support body  121  in a top-down direction. 
     According to this configuration, since an end portion of the engaging hook  111  is movable in a front-rear direction on an upper surface of the support body  121 , an upper end portion of the bumper  110  may be supported by the support portion  120  to be movable forward, backward, left, and right while being suspended on the support portion  120 . 
     The fitting portion  123  may be provided at a rear end portion of the support body  121 . A plurality of fitting portions  123  may be disposed to be spaced apart from one another along a circumference of the support body  121 . 
     The fitting portion  123  may be provided with fitting grooves on both left and right side surfaces with an intermediate partition wall interposed therebetween. The fitting portion  123  may be formed in an H-shape or I-shape. A plurality of slits may be disposed on a front surface of the cleaner body  100 . 
     The intermediate partition wall of the fitting portion  123  is fitted along the slit, and both left and right end portions of the slit of the cleaner body  100  are fitted into the fitting grooves on both sides thereof, thereby allowing the support portion  120  to be coupled to the cleaner body  100 . 
     A plurality of protruding portions  113  may be disposed at a lower end of the bumper  110  such that a lower end portion of the bumper  110  is not inclined toward an inside of the cleaner body  100  than an upper end portion of the bumper  110 , and a front surface of the bumper  110  maintains a top-down direction while the upper end portion of the bumper  110  is suspended on the support portion  120 . 
     The protruding portion  113  may be disposed to protrude horizontally toward an inside of the cleaner body  100 . 
     The plurality of protruding portions  113  may be spaced apart from one another on both left and right sides along a circumference of the bumper  110 . The plurality of protruding portions  113  may be symmetrically spaced apart from each other on both left and right sides with respect to a front-rear center line passing through a longitudinal center of the bumper  110  in a front-rear direction. The plurality of protruding portions  113  may be symmetrically disposed with respect to the front-rear center line. 
     The protruding portion  113  may extend along a partial section of the left and right circumferences of the bumper  110 . One side surface of the protruding portion  113  may protrude in a curvature radial direction perpendicular to a curved surface of the bumper  110 , and the other side surface of the protruding portion  113  may be disposed to protrude obliquely with respect to the curved surface of the bumper  110 . 
     An outer circumferential length of the protruding portion  113  may extend longer than an inner circumferential length of the protruding portion  113 . The protruding portion  113  may have a trapezoidal plate structure. 
     The protruding portion  113  may be accommodated on one side of the mounting guide  150  to be described later and movably supported an inside of the cleaner body  100  by the mounting guide  150 . 
     According to this configuration, the protruding portion  113  is accommodated in a second accommodating portion  153  disposed on one side of the mounting guide  150  to stably guide the movement of the bumper  110 . 
     Although the sensing unit  103  detects an obstacle in front of the cleaner body  100 , when there is an obstacle in a blind spot that cannot be sensed by the sensing unit  103  or an obstacle suddenly appears, a collision between the robot cleaner and the obstacle may occur. 
     When such a collision occurs, the cleaner body  100  needs to be controlled so as to be separated from the obstacle through a retreat or change of direction. For this, the detection of a collision with an obstacle is required preferentially. 
     Hereinafter, a collision detection portion for detecting a collision with an obstacle will be described in more detail. 
       FIG.  5    is an assembly view showing a shape in which a collision detection portion mounted on a front surface of the cleaner body  100  in  FIG.  3    is viewed from a bottom surface. 
       FIG.  6    is an exploded view of the bumper  110 , the support portion  120 , the cliff sensor  130 , and the shielding module  140  (the mounting guide  150 , the cover plate  142 , the cam  141 ) in  FIG.  5   . 
       FIG.  7    is a bottom view showing the mounting guide  150  in  FIG.  6   . 
       FIG.  8    is a bottom view showing the cover plate  142 , the cam  141 , and the rotation shaft  145  in  FIG.  6   . 
       FIG.  9    is an enlarged conceptual view showing a shape in which the shielding module  140  is mounted on a bottom surface of the cleaner body  100  taken along line IX-IX in  FIG.  5   . 
     An opening portion  101  is disposed on a bottom surface of the cleaner body  100  to open downward. The opening portion  101  may be disposed on left and right sides of the bottom surface of the cleaner body  100  with the brush module  102  or the mop module therebetween. 
     The cliff sensor  130  that detects a terrain below may be disposed inside the opening portion  101 . The cliff sensor  130  may be disposed above the opening portion  101 . The cliff sensor  130  may be mounted inside the cleaner body  100 . 
     The cliff sensor  130  may be exposed to a lower side of the cleaner body  100  through the opening portion  101 . 
     The cliff sensor  130  may include a sensor housing, a housing cover, a light emitting portion  131 , and a light receiving portion  132 . 
     Fastening portions may be disposed to protrude from both end portions of the sensor housing. The fastening portion may be defined in a ring shape having a fastening hole disposed therein. The fastening portion may fasten both sides of the sensor housing to the cleaner body  100  using a fastening member such as a screw passing through the fastening hole. 
     The housing cover is mounted to cover an open lower portion of the sensor housing. 
     The light emitting portion  131  is configured to irradiate light (e.g., infrared rays) to a lower side of the opening portion  101 . 
     The light receiving portion  132  is configured to receive reflective light reflected from the floor. 
     According to this configuration, light is irradiated downward from the light emitting portion  131  through the opening portion  101 , and reflective light is reflected from the floor and received by the light receiving portion  132 . 
     The controller may measure a time period taken from a time point at which light is irradiated from the light emitting portion  131  to the completion of reception by the light receiving portion  132  to measure a distance between the cliff sensor  130  and the floor. 
     Accordingly, in a case where there is a step protrusion that is sharply lowered in front of the cleaner body  100 , when the reception time period of the reflective light is rapidly increased, and there is a cliff in front, the reflected light is not received by the light receiving portion  132 . 
     The cliff sensor  130  may be disposed to be inclined with respect to a bottom surface of the cleaner body  100  such that the light emitting portion  131   s  irradiate light toward the floor at a lower front side thereof. 
     According to this configuration, the cliff sensor  130  may detect a terrain at a lower front side of the cleaner body  100 , and accordingly, there is an advantage capable of performing an evasive operation by detecting a geographic feature on an expected path of the cleaner body  100  in advance. 
     Unlike an inclined disposition structure of the cliff sensor  130 , the cliff sensor  130  may also be configured to be vertically disposed on a bottom surface of the cleaner body  100  such that the light emitting portion  131  irradiates light to be perpendicular to the floor on which the cleaner body  100  is supported. 
     When it is detected that the terrain below is lowered to a predetermined level or more through the cliff sensor  130 , the controller may change the control of the driving wheel  104  in a preset manner. 
     For example, the controller may control the drive motor to rotate the robot cleaner so as to drive only one driving wheel  104  or drive both driving wheels  104  in different directions. 
     Alternatively, the controller may drive the driving wheel  104  in an opposite direction such that the robot cleaner moves backward in a reverse direction. 
     Meanwhile, the cleaner body  100  is provided with a collision detection portion that detects a physical collision with an obstacle. The collision detection portion includes the bumper  110  and the cliff sensor  130  described above. 
     The bumper  110  is movably mounted to the support portion  120 , and the bumper  110  is disposed to protrude forward from a front surface of the cleaner body  100  in a state where no external force is applied. 
     When the bumper  110  collides with an obstacle, a portion of the bumper  110  is configured to be movable toward an inside of the cleaner body  100  by being pushed by an external force. 
     When the bumper  110  is spaced apart from the obstacle, the bumper  110  is moved to an outside of the cleaner body  100 , that is, to a front side of the cleaner body  100 , and returned to an original position, for example, a position at which the bumper  110  protrudes forward from a front surface of the cleaner body  100 . 
     For the inward and outward movements of the bumper  110 , an elastic member (not shown) may be disposed between the bumper  110  and the cleaner body  100 . The elastic member may be configured to elastically push the bumper  110  to an outside of the cleaner body  100 . 
     Alternatively, the bumper  110  may be elastically supported by the cleaner body  100  to be movable inwardly. 
     To this end, the bumper  110  may be provided with the elastic support portion  120  elastically supported by the cleaner body  100 . In this case, there is an advantage of reducing production cost and simplifying structure in that an elastic member is not required. 
     In a robot cleaner in the related art, a detection element that detects an inward movement of the bumper  110 , for example, a micro switch, an infrared sensor, and the like are provided inside the bumper  110 . However, in this case, there are problems such as an increase in production cost due to the detection element and an increase in the volume of the cleaner body  100  due to the mounting of the detection element. 
     The present disclosure provides the cliff sensor  130  and the shielding module  140  as described above as an element that detects an inward movement of the bumper  110  when colliding with an obstacle. 
     Hereinafter, this will be described in detail. 
     A plurality of shielding modules  140  may be disposed symmetrically to each other on both left and right sides with respect to a front-rear center line passing through the center of the cleaner body  100  in a front-rear direction. The plurality of shielding modules  140  may be disposed adjacent to both left and right end portions of the bumper  110 , respectively. 
     The shielding module  140  is configured to selectively expose the cliff sensor  130  in conjunction with the bumper  110 . 
     The shielding module  140  may include a mounting guide  150 , a cam  141 , a cover plate  142 , a rotation shaft  145 , and an elastic element  146 . 
     The mounting guide  150  may be defined in the form of an arc-shaped plate. 
     The mounting guide  150  is mounted on a bottom surface of the cleaner body  100 . Coupling portions  1501  may be disposed to protrude from front and rear end portions of the mounting guide  150  in a circumferential direction thereof. A coupling hole may be formed inside the coupling portion  1501 . The coupling portion  1501  may couple the mounting guide  150  and the cleaner body  100  by allowing a fastening portion such as a screw to pass through the coupling hole. 
     The mounting guide  150  may be disposed between the bumper  110  and the opening portion  101 . 
     An outer peripheral edge portion of the mounting guide  150  may be disposed adjacent to the bumper  110 , and an inner peripheral edge portion of the mounting guide  150  may be disposed adjacent to the opening portion  101 . 
     A first accommodating portion  151  may be concavely disposed on one side of the mounting guide  150 , and a second accommodating portion  153  may be concavely disposed on the other side of the mounting guide  150 . The first accommodating portion  151  and the second accommodating portion  153  may be partitioned by a partition wall  154 . 
     The first accommodating portion  151  is configured to accommodate the cam  141  and the cover plate  142 . The cam  141  is configured to be in contact with the bumper  110 . The cover plate  142  is configured to selectively expose the cliff sensor  130 . 
     The cam  141  and the cover plate  142  are configured to rotate together around the same rotation shaft  145 . The cam  141  and the cover plate  142  may be connected to each other by a hinge portion  143  surrounding the rotation shaft  145 . 
     The hinge portion  143  may be defined in a ring shape. A hinge hole may be disposed inside the hinge portion  143 . The hinge portion  143  may be hinge-coupled to the rotation shaft  145  by allowing the rotation shaft  145  to pass through the hinge hole. 
     The cam  141  and the cover plate  142  may extend in a rotational radial direction with a preset phase angle therebetween. Here, the phase angle may be an acute angle smaller than 90 degrees. 
     One side of the cam  141  may be supported by being connected to one side of the hinge portion  143 . 
     One side of the cover plate  142  may be supported by being connected to the other side of the hinge portion  143 . One side of the hinge portion  143  may be located in front of the other side of the hinge portion  143  toward the bumper  110 . A connection portion may extend between the cover plate  142  and the hinge portion  143 , and the cover plate  142  and the hinge portion  143  may be connected by the connection portion. The connection portion may extend in a curved shape to surround one edge of the opening portion  101 . 
     The cam  141  may be formed in a right-angled triangle shape. Among the corners of the cam  141 , a corner portion meeting at a right angle may be connected to the hinge portion  143 . 
     An edge surface of the cam  141  may be composed of three surfaces, that is, an inclined surface  1411 , a bottom surface  1412 , and a height surface  1413 . 
     The inclined surface  1411  is inclined with respect to the bottom surface  1412  and the height surface  1413 . 
     The inclined surface  1411  is configured to be in contact with the guide protrusion  112  disposed to protrude from the bumper  110 . The guide protrusion  112  may be integrally connected to the bumper  110  by a connecting rib. 
     The connecting rib may include a first connecting rib and a second connecting rib. 
     The first connection rib may extend from an inner surface of the bumper  110  toward an inner side of the cleaner body  100  in a curvature radial direction of the bumper  110 . 
     The second connecting rib may be disposed to extend in a circumferential direction from an inner end of the first connecting rib. 
     The guide protrusion  112  is disposed to protrude downward from the second connecting rib. The guide protrusion  112  may be defined in various shapes, such as a rectangular, a circular cross-sectional shape, and the like. 
     Three surfaces of the cam  141  may extend in the following directions from an initial position prior to the occurrence of a bumping operation of the bumper  110  (with reference to  FIG.  8   ). 
     The bottom surface  1412  may extend in a left-right lateral direction of the cleaner body  100 . 
     The height surface  1413  may extend in a front-rear direction of the cleaner body  100 . 
     The inclined surface  1411  may extend to be inclined in a direction intersecting the bottom surface  1412  and the height surface  1413 . 
     A length of the bottom surface  1412  may be longer than that of the height surface  1413 . 
     The inclined surface  1411  is brought into contact with the guide protrusion  112  of the bumper  110  in conjunction with the movement of the bumper  110 . 
     The inclined surface  1411  extends in a direction intersecting a movement direction of the guide protrusion  112 . 
     Both side corners of the inclined surface  1411  meeting the bottom surface  1412  and the height surface  1413  may be disposed to be rounded in a curved shape. 
     According to this configuration, when the bumper  110  collides with an obstacle, the cam  141  may be rotated about the rotation shaft  145  no matter which direction the guide protrusion  112  is pushed against the inclined surface  1411 . 
     Furthermore, the inclined surface  1411  of the cam  141  may serve to convert a linear movement of the guide protrusion  112  into a rotational movement of the cam  141 . 
     The cover plate  142  may be defined in a rectangular plate shape. The cover plate  142  may be disposed to be smaller than an opening area of the opening portion  101 . Each corner portion of the cover plate  142  may be disposed to be rounded in a curved shape. 
     The cover plate  142  may be connected to the hinge portion  143  by a connecting portion. One side of the connecting portion may be connected to one corner portion of the cover plate  142 , and the other side of the connecting portion may extend to be connected to the other side of the hinge portion  143 . 
     According to this configuration, the cover plate  142  may selectively expose the cliff sensor  130  before and after a collision between the bumper  110  and the obstacle. 
     For example, the cover plate  142  is disposed to reciprocally rotate between a first position and a second position about the rotation shaft  145 . 
     The first position is a position of the cover plate  142  before the bumper  110  collides with the obstacle. At the first position, the cover plate  142  is disposed not to overlap the opening portion  101  in a top-down direction. One side surface of the cover plate  142  may be disposed on a boundary line of one side of the opening portion  101 . 
     At the first position, the cover plate  142  may expose the cliff sensor  130 . Since the cliff sensor  130  irradiates light downward through the opening portion  101 , and then receives reflective light reflected from the floor after, it is unable to recognize an inward movement (bumping operation) of the bumper  110 . 
     The second position is a position of the cover plate  142  after the bumper  110  collides with the obstacle. 
     At the second position, the cover plate  142  is disposed to overlap the opening portion  101  in a top-down direction. 
     At the second position, the cover plate  142  may cover the cliff sensor  130 . Since the cliff sensor  130  irradiates light downward through the opening portion  101 , and then receives reflective light reflected by the cover plate  142  before the light reaches the floor, it is able to recognized an inward movement (bumping operation) of the bumper  110 . 
     Here, since the reception time period of reflective light reflected by the cover plate  142  is rapidly shortened compared to the reception time period of light reflected by the floor, the controller recognizes the bumping operation. 
     The reception time period of the reflective light by the cover plate  142  may be shorter than the reception time period of the reflected light by a step protrusion. A height between the cover plate  142  and the floor surface is located higher than that of an upper end of the step protrusion capable of passing through a lower portion of the bumper  110 . 
     A distance between the center of the rotation shaft  145  and an outermost portion of the cover plate  142  farthest therefrom is greater than a distance between a contact point of the inclined surface  1411  of the cam  141  in contact with the guide protrusion  112  and the center of the rotation shaft  145 . For example, the distance between the center of the rotation shaft  145  and the outermost portion of the cover plate  142  farthest therefrom may be 2 to 3 times greater compared to the distance between the contact point of the inclined surface  1411  of the cam  141  with which the guide protrusion  112  is in contact and the center of the rotation shaft  145 . 
     According to this configuration, a rotational movement distance of the cover plate  142  for the same time period during an inward movement of the bumper  110  may be greater than a movement distance of the guide protrusion  112  such that a movement speed of the cover plate  142  is much faster than that of the bumper  110 , thereby increasing a recognition speed of the inward movement of the bumper  110 . 
     Furthermore, during the inward movement of the bumper  110 , an amount of rotation of the cover plate  142  for the same time period may be much greater than an amount of rotation of the cam  141  by pushing the guide protrusion  112 , thereby improving the sensitivity of the bumper  110  to inward movement recognition. 
     The second accommodating portion  153  is configured to accommodate the protruding portion  113  protruding from a lower side of the bumper  110 . 
     The second accommodating portion  153  may be defined in a flat plate shape. The protruding portion  113  may also be defined in a flat plate shape. The protruding portion  113  may be in surface contact with the second accommodating portion  153 . The protruding portion  113  is configured to be slidable along the second accommodating portion  153  during the inward movement of the bumper  110 . 
     The protruding portion  113  may be configured to be inserted into the second accommodating portion  153 , thereby allowing the mounting guide  150  to guide the mounting of the bumper  110  so as to improve assembly performance. 
     The second accommodating portion  153  may be disposed at a front side of the first accommodating portion  151  in a circumferential direction. 
     The partition wall  154  may be disposed between the first accommodating portion  151  and the second accommodating portion  153 . The partition wall  154  may extend in a direction crossing an outer edge portion and an inner edge portion of the mounting guide  150 . 
     The first accommodating portion  151  and the second accommodating portion  153  may be disposed to be open in opposite directions to each other. 
     As the protruding portion  113  of the bumper  110  is accommodated from an outside of the first accommodating portion  151  to an inside thereof, the first accommodating portion  151  may be disposed to be open to face a protrusion direction of the protruding portion  113  of the bumper  110 . Part of the protruding portion  113  of the bumper  110  may be disposed to overlap the first accommodating portion  151  in a top-down direction. 
     As the cam  141  and the cover plate  142  are rotationally moved from an inside of the second accommodating portion  153  toward the opening portion  101 , the second accommodating portion  153  may be disposed to be open in a rotation direction of the cam  141  and the cover plate  142  (a direction covering the cliff sensor  130 ). 
     A first shielding wall  155  may extend from one end (an outside) of the partition wall  154  toward one end (a rear end) of the mounting guide  150  along an outer edge portion of the mounting guide  150 . The first shielding wall  155  is configured to block an outer boundary of the first accommodating portion  151 . The first shielding wall  155  is configured to open an inner boundary of the first accommodating portion  151 . 
     A second shielding wall  156  may extend from the other end (an inside) of the partition wall  154  toward the other end (a front end) of the mounting guide  150  along an inner edge portion of the mounting guide  150 . The second shielding wall  156  is configured to block an inner boundary of the second accommodating portion  153 . The second shielding wall  156  is configured to open an outer boundary of the second accommodating portion  153 . 
     According to this configuration, the first shielding wall  155  may block the cam  141  and the cover plate  142  from being released from the first accommodating portion  151  to an outside of the first accommodating portion  151 . 
     The second shielding wall  156  may prevent the protruding portion  113  from being excessively inserted into the second accommodating portion  153  to be released from the second accommodating portion  153  to an inside of the cleaner body  100  during the inward movement of the bumper  110 . 
     The mounting guide  150  has a guide hole  152  for limiting a movement range of the guide protrusion  112 . 
     The guide hole  152  may be disposed to pass through the first accommodating portion  151  in a top-down direction. The guide hole  152  may be disposed to overlap the guide protrusion  112  in a top-down direction. The guide protrusion  112  may be inserted into the first accommodating portion  151  by passing through the guide hole  152 . The guide protrusion  112  passing through the guide hole  152  is configured to be in contact with the inclined surface  1411  of the cam  141  at an inside of the first accommodating portion  151 . 
     The guide hole  152  may be defined in a trapezoidal shape. The guide hole  152  may be defined to have a circumferential width that becomes wider from an outside of the mounting guide  150  to an inside thereof. 
     An inner surface of a circumferential surface of the guide hole  152  may be disposed to be inclined with respect to an outer surface of the circumferential surface. 
     The guide hole  152  may be disposed to have a radial width that becomes wider from a front side to a rear side of the mounting guide  150 . 
     According to this configuration, it may be possible not only to limit an unnecessary movement range of the guide protrusion  112 , but also to secure an effective distance of the guide protrusion  112  so as to sufficiently transmit a pushing force to the inclined surface  1411  when the guide protrusion  112  pushes the inclined surface  1411  of the cam  141 . 
     The mounting guide  150  includes a shaft coupling portion  1502  for coupling with the rotation shaft  145 . 
     The shaft coupling portion  1502  may be disposed to protrude in a circular ring shape from an inner surface of the mounting guide  150 . A through hole may be disposed in the shaft coupling portion  1502  to pass therethrough in a top-down direction. 
     The shaft coupling portion  1502  and the hinge portion  143  of the mounting guide  150  may be disposed to overlap in a top-down direction. 
     The rotation shaft  145  may be disposed in a tubular shape. The rotation shaft  145  may be inserted into and coupled to the hinge hole of the hinge portion  143  and the through hole of the shaft coupling portion  1502 . The rotation shaft  145  may be configured to be rotatably supported by the cleaner body  100  with respect to the shaft coupling portion  1502  together with the hinge portion  143 . 
     The shielding module  140  includes an elastic element  146  for restoring the cover plate  142  to an original position. 
     The elastic element  146  is configured to restore the cover plate  142  from the second position (covers the cliff sensor  130 ) to the first position (exposes the cliff sensor  130 ). 
     The elastic element  146  may be implemented as a spring. 
     One end of the spring may be fixed to the mounting guide  150 . The other end of the spring may be fixed to the cover plate  142 . 
     A first fixing protrusion  157  may be disposed to protrude from the first shielding wall  155  of the mounting guide  150 , and one end of the spring may be fixed to the first fixing protrusion  157 . However, the present disclosure is not limited thereto, and one end of the spring may be fixed to the cleaner body  100 . 
     A second fixing protrusion  158  may be disposed to protrude from the cover plate  142 , and the other end of the spring may be fixed to the second fixing protrusion  158 . 
     Hereinafter, a collision recognition method between the shielding module  140  and the cliff sensor  130  according to the present disclosure when the bumper  110  collides with an obstacle will be described in detail. 
       FIG.  10    is a conceptual view showing a shape in which the cover plate  142  is at a first position to expose the cliff sensor  130  before a collision between the bumper  110  and the obstacle. 
       FIG.  11    is a cross-sectional view taken along line XI-XI in  FIG.  10   . 
       FIG.  12    is a conceptual view showing a shape in which the cover plate  142  is at a second position to cover the cliff sensor  130  after the bumper  110  collides head-on with an obstacle in  FIG.  10   . 
       FIG.  13    is a cross-sectional view taken along line XIII-XIII in  FIG.  12   . 
       FIG.  14    is a conceptual view showing a shape in which the cover plate  142  is at a second position to cover the cliff sensor  130  after the bumper  110  collides laterally with an obstacle in  FIG.  10   . 
     Referring to  FIG.  10   , before the bumper  110  collides with the obstacle, the cover plate  142  exposes the cliff sensor  130  downward through the first position, that is, the opening portion  101 . 
     In this case, as illustrated in  FIG.  11   , the light emitting portion  131  of the cliff sensor  130  irradiates light to a terrain below, and the light receiving portion  132  of the cliff sensor  130  receives reflective light reflected from the terrain below. 
     The controller may receive a detection signal from the cliff sensor  130  and measure a time received by the light receiving portion  132  to detect a terrain below. 
     Referring to  FIG.  12   , after the bumper  110  collides head-on with an obstacle, the bumper  110  is pushed backward. 
     The guide protrusion  112  of the bumper  110  comes into contact with the inclined surface  1411  of the cam  141  while being accommodated in the guide hole  152  of the mounting guide  150  to push the cam  141  backward. The cam  141  rotates clockwise based on the drawing about the rotation shaft  145 . 
     The cover plate  142  rotates from the first position to the second position while maintaining a constant phase angle with the cam  141  about the rotation shaft  145 . The first position is a position where the cliff sensor  130  is exposed through the opening portion  101 , and the second position is a position where the cliff sensor  130  is covered by the cover plate  142 . At the second position, the cover plate  142  and the cliff sensor  130  may be disposed to overlap in a top-down direction. 
     As the bumper  110  collides head-on with an obstacle, the cover plate  142  may cover at least part of the opening portion  101  to close the cliff sensor  130 . 
     As illustrated in  FIG.  13   , the light emitting portion  131  of the cliff sensor  130  irradiates light to the cover plate  142 , and the light receiving portion  132  of the cliff sensor  130  receives reflective light reflected from the cover plate  142 . The cover plate  142  is located higher than a terrain below (the floor on which the vacuum cleaner drives). 
     The controller may receive a detection signal from the cliff sensor  130  to measure a time received by the light receiving portion  132 , compare a preset time value with the measured time value, and recognize that the bumper  110  has collided head-on with the obstacle when it is determined that the measured time value is abruptly smaller than a preset time value. 
     Here, a distance h between the center of the cover plate  142  and the center of the rotation shaft  145  is two times or more greater than a distance g between a contact point of the inclined surface  1411  of the cam  141  in contact with the guide protrusion  112  and the center of the rotation shaft  145 . 
     A rotational movement distance (an amount of rotation) of the cover plate  142  is much larger than a rotational movement distance (an amount of rotation) of the cam  141  pushed by the guide protrusion  112 , so a rotational speed of the cover plate  142  is much faster compared to a rotation speed of the cam  141 . 
     This means that the rotational speed of the cover plate  142  is faster than an inward movement speed of the bumper  110 . 
     Accordingly, as the rotation speed of the cover plate  142  is accelerated, the sensitivity of collision detection using the cliff sensor  130  may be improved. 
     Referring to  FIG.  14   , when the bumper  110  collides laterally with an obstacle, the guide protrusion  112  of the bumper  110  moves from right to left based on the drawing while being accommodated in the guide hole  152 , but one side surface of the guide hole  152  is disposed to be inclined from right toward left rearward, and the guide protrusion  112  is guided by the guide hole  152  to move from right to left rearward. 
     A lateral collision between the bumper  110  and the obstacle is different from a head-on collision between the bumper  110  and the obstacle in that a movement direction of the guide protrusion  112  is guided by the guide hole  152  to move from right to left rearward. 
     The other operations and effects of the cam  141  and the cover plate  142  are the same as or similar to those of the above-described embodiments of  FIGS.  12  and  13   , and thus a redundant description will be omitted. 
     Therefore, according to the present disclosure, the shielding module  140  provided at a lower portion of the cleaner body  100  separately from the bumper  110  may selectively expose the cliff sensor  130  in conjunction with an inward movement of the bumper  110 , thereby detecting a collision between the bumper  110  and the obstacle. 
     In addition, the shielding module  140  includes the cam  141  and the cover plate  142  that rotate with the same phase angle around the same rotation shaft  145 . A distance between the center of the cover plate  142  and the center of the rotation shaft  145  is configured to be greater compared to a distance between a contact point of the inclined surface  1411  of the cam  141  in contact with the guide protrusion  112  of the bumper  110  and the center of the rotation shaft  145 . For this reason, a rotational movement speed of the cover plate  142  rotating to cover the cliff sensor  130  is much faster than an inward movement speed of the bumper  110 . Accordingly, a sensitivity between the bumper  110  and the obstacle to collision detection is improved using the cliff sensor  130 . 
     Moreover, the guide protrusion  112  protruding from an inner surface of the bumper  110  is provided on the bumper  110 , and the shielding module  140  is provided with the guide hole  152  for limiting a movement range of the guide protrusion  112 . The guide hole  152  is disposed to be inclined such that the guide protrusion  112  is able to move the inclined surface  1411  of the cam  141  backward during a head-on collision of the bumper  110  as well as a lateral collision of the bumper  110 . For this reason, the cover plate  142  may be guided to cover the cliff sensor  130  in all collision directions of the bumper  110 , thereby increasing the reliability of collision detection.