Patent Publication Number: US-11641999-B2

Title: Cleaner

Description:
BACKGROUND 
     1. Field 
     The present disclosure relates to a cleaner, and more particularly, to a cleaner capable of easily sweeping a foreign material on a floor. 
     2. Description 
     A cleaner is a device that cleans a floor by inhaling a foreign material such as a dust on the floor or wiping a foreign material on the floor. Recently, a cleaner capable of mopping a floor has been developed. In addition, a robot cleaner is a device that cleans while driving or traveling on its own. 
     In Korean Patent Publication No. 10-1602790 (hereinafter, referred to as KR&#39;790), a robot cleaner capable of traveling while performing wet-type cleaning using a wet-type cleaner is disclosed. 
     In KR&#39;790, the robot cleaner includes a pair of cleaners arranged in a left-right direction, and a driving unit that rotates each cleaner by providing driving force. In KR&#39;790, both of wet-type cleaning and traveling are performed through the pair of cleaners, but inhaling of a foreign material on a floor is impossible. 
     In Korean Patent Laid-Open Publication No. 10-2005-0034112 (hereinafter, referred to as KR&#39;112), a robot cleaner equipped with a dust container and a mop. In KR&#39;112, since a wheel and a motor for traveling or driving of the robot cleaner and a suction fan and a motor for inhaling a dust should be separately provided, an operation structure may be complex. 
     Particularly, in KR&#39;112, since a dust is inhaled through a pressure difference by a suction fan, power consumption may be large and a large noise may be generated. 
     Further, in the conventional art, since a robot cleaner proceeds only by friction force of spin mops and a water level of stored water in a water tank is variable, it may be difficult to effectively mop a floor and driving power may be not sufficient. 
     Particularly, it may be very difficult for the conventional wet-type robot to adjust a traveling direction by friction force with rotating mops. Accordingly, cleaning is performed only by a random driving, and cleaning by a pattern driving being able to meticulously clean is impossible. 
     Further, in the conventional art, since the cleaning is possible only by the random driving, meticulous cleaning at a corner of a floor or an area adjacent to a wall may be difficult. 
     SUMMARY 
     In a cleaner traveling or moving by friction force of a spin mop, if there is a suction fan for sucking a dust, power consumption may be large and a volume of the cleaner may be large. If the suction fan is omitted or removed from the cleaner using the spin mop, an ability to inhale a dust may be reduced and thus a large dust or foreign material on a floor may remain after cleaning. Accordingly, the present disclosure is for providing a cleaner being able to solve the problem and to collect a foreign material only by rotational force of an agitator through including a dustpan that guides the foreign material when the agitator rotates. 
     The present disclosure is also for providing a cleaner being able to easily sweep up a foreign material on a floor through rotation of an agitator disposed at a front side of a mop module. 
     The present disclosure is for providing a cleaner equipped with a dustpan being able to effectively sweep up a foreign material on a floor and avoiding contact with an obstacle on a floor. 
     The present disclosure is for providing a cleaner being able to effectively sweep up a foreign material on a floor in a structure where an agitator and a dust housing are integrated with each other. 
     The present disclosure is for providing a cleaner being able to clean a foreign material on a floor at a front side of a pair of mop modules before the foreign material is in contact with the mop module in a cleaner that travels and mop the floor by rotation of the pair of mop modules. 
     The present disclosure is for providing a cleaner having a structure where an agitator and a dust housing are integrated with each other. 
     When a body of a cleaner has a circular shape or a shape close to a circular shape, rotation in place is easy. When the rotation in place is easy, a cleaner can easily escape from an obstacle area or a corner. However, when the body of the cleaner has the circular shape, a width of an agitator is limited to be smaller than a diameter of the body so that the agitator is not disturbed by an obstacle during the body rotates. Accordingly, the present disclosure is for providing a cleaner being able to maximize a width of an agitator in a state that the agitator does not protrude from the body by disposing a storage space that stores a foreign material collected from the agitator at a front side than the agitator. Therefore, a size of an area to be cleaned at once is not reduced. In this instance, the cleaner according to the present disclosure makes rotation of the body easy by limiting the width of the agitator to be smaller than a diameter of the body. 
     The present disclosure is for providing a cleaner being able to make rotation of a body easy by a circular shape of the body. In this instance, the cleaner according to the present disclosure can reduce friction between an obstacle and spin mops, make rotation of the body easy, and maximize a size of an area to be cleaned at once when the body rotates by disposing rotation axes of a pair of spin mops to be eccentrical or deviated from a center of the body and disposing a part of each spin mop to be overlapped with the body vertically. 
     The present disclosure is also for providing a robot cleaner or a mobile robot being able to increase friction force between a mop and a floor regardless of a water-level change in a water tank for effective mopping and traveling and to perform a pattern driving that allows meticulous cleaning through accurate driving. 
     A robot cleaner or a mobile robot according to the present disclosure includes an agitator rotating and collecting a foreign material on a floor and a dustpan for guiding the foreign material moved by the agitator into an inside of a dust housing. The dustpan covers a part of an outer circumferential surface of the agitator and independently rotates with the agitator. Accordingly, insufficient cleaning power of the agitator can be compensated and the dustpan can be prevented from being damaged. 
     When the dustpan of the present disclosure interferes with an obstacle on the floor, the dustpan is rotated and accommodated into a collection space positioned at the inside of a dust housing. 
     More particularly, a cleaner according to the present disclosure includes a dust housing, an agitator, and a dustpan. The dust housing has a collection opening surface toward a floor. The agitator is disposed at an inside of the dust housing, is rotatably assembled with the dust housing, and is exposed to an outside through the collection opening surface. The agitator is in contact with the floor to sweep up a foreign material on the floor into the inside of the dust housing. The dustpan is installed on any one of the dust housing and the agitator and guides the foreign material moved by the agitator into the inside of the dust housing. The dustpan surrounds a part of an outer circumferential surface of the agitator and is installed to independently rotate with the agitator. 
     The dustpan is rotatable with respect to a rotation axis. Accordingly, when the dustpan interferes with an obstacle on the floor, the dustpan can be rotated and accommodated into a collection space positioned at the inside of the dust housing. 
     The agitator may rotate from a front side to a rear side and the dustpan may be disposed at a rear side of the agitator. The foreign material moved to the rear side is guided to the collection space by the dustpan. 
     The dustpan may be installed on the dust housing. The dustpan may cover a part of the outer circumferential surface and parts of both side surfaces of the agitator, thereby minimizing a breakaway of the foreign material to an outside the dustpan. 
     A rotation axis of the dustpan may be positioned at a rotation axis of the agitator. 
     The dust housing may include a housing assembly, the collection opening surface, a partition, and a storage opening surface. The housing assembly may have a collection space and a storage space at an inside of the housing assembly. The collection opening surface may be disposed at a bottom surface of the housing assembly, communicate with a lower side of the collection space, and be exposed toward the floor. The partition may be disposed at the inside of the housing assembly and partition the collection space and the storage space. The storage opening surface may be disposed at one of the housing assembly or the partition and guide the foreign material in the collection space to the storage space. The agitator and the dustpan may be disposed at the collection space. 
     The rotation axis of the agitator may extend in a left-right direction. The dustpan may be disposed at an opposite side of the partition with respect to the rotation axis of the agitator. 
     The cleaner may further include a pan elastic member having one end fixed to the dustpan and the other end fixed to the housing assembly. The dustpan may be further provided with a first pan fixing portion where the one end of the pan elastic member is fixed. The housing assembly may be further provided with a second pan fixing portion where the other end of the pan elastic member is fixed. 
     The first pan fixing portion may be disposed higher than the second pan fixing portion. 
     The rotation axis of the agitator may extend in a left-right direction. The first pan fixing portion and the second pan fixing portion may be disposed at an opposite side of the partition with respect to the rotation axis of the agitator. 
     The cleaner according to the present disclosure may further include a dustpan stopper disposed at the housing assembly. The dustpan stopper may form a mutual interference structure with the dustpan to limit rotation of the dustpan. The dustpan stopper may be disposed within a rotation radius of the dustpan. 
     The dustpan stopper may be disposed at a lower side of the dustpan. 
     The dustpan may further include a guide pan housing formed to surround a part of the outer circumferential surface of the agitator, and a side pan housing disposed at one side of the guide pan housing and surrounding a side portion of the agitator. 
     The guide pan housing may include a curved portion surrounding the outer circumferential surface of the agitator, and a dust guard coupled to a lower end of the curved portion and in contact with the floor. The dust guard may protrude to a lower side of the collection opening surface and may be formed of an elastic material. 
     A curvature center of the curved portion may be disposed at an inside of the agitator. 
     The cleaner according to the present disclosure may further include a through hole penetrating the side pan housing and a pan guide inserted into the through hole at the side surface of the housing assembly. A side portion of the agitator may be rotatably supported by the housing assembly through penetrating the through hole. The side pan housing may be rotated through being supported by the pan guide. 
     In addition, a cleaner according to the present disclosure includes a body, and a sweep module installed on a lower portion of the body to collect a foreign material. 
     The sweep module includes an agitator rotating and collecting the foreign material on a floor, a storage space where the foreign material collected by the agitator is stored, and a dustpan for guiding the foreign material moved by the agitator into an inside of a dust housing. The dustpan covers a part of an outer circumferential surface of the agitator and independently rotates with the agitator. A rotation axis of the dustpan may be positioned at a rotation axis of the agitator. 
     The dustpan may be disposed at an area of 40% to 70% of an arbitrary circle surrounding an outer circumference of the agitator. 
     The dustpan may move within an arc having a center angle of 180 degrees to 220 degrees at an orbit of the arbitrary circle surrounding the outer circumference of the agitator. The dustpan may have a smaller length than the arc. 
     Further, a cleaner according to the present disclosure includes a body having a circular shape when view from an upper side, and a sweep module installed on a lower portion of the body to collect a foreign material and completely overlapped with the body vertically. The sweep module includes an agitator rotating and collecting the foreign material on a floor and a storage space where the foreign material collected by the agitator is stored. The storage space may be disposed at a front side than the agitator. 
     Also, the cleaner according to the present disclosure may further include a spin mop that is rotated. A mop portion may be attached to a lower surface of the spin mop. 
     Firstly, according to the present disclosure, interference or impact with or from an obstacle can be minimized since a dustpan is rotated and is accommodated into a collection space positioned at inside of a dust housing when the dustpan is interfered with the obstacle on a floor. 
     Secondly, according to the present disclosure, a collected foreign material can be transferred to a collection space, even if a dustpan collides with an obstacle on a floor, since the dustpan is rotatable with respect to a rotation axis of the agitator. 
     Thirdly, according to the present disclosure, a collected foreign material can be transferred to a collection space in a state confined between a dustpan and an agitator since the dustpan is in contact with an outer circumferential surface of the agitator. 
     Fourthly, according to the present disclosure, a dustpan can be returned to its original position by using an elastic force of a pan elastic member since the pan elastic member connects the dustpan and a housing assembly, 
     Fifthly, according to the present disclosure, an impact due to a contact with an obstacle can be minimized since a dust guard, which is disposed at a lower end of the dustpan and is in contact with a floor, is formed of an elastic material. 
     Sixthly, according to the present disclosure, excessive rotation of a dustpan can be prevented by a dustpan stopper disposed at a housing assembly and disposed within a rotational radius of the dustpan. 
     Seventhly, according to the present disclosure, resistance against a driving or traveling direction of a cleaner can be minimized and a dustpan disposed at a rear side of an agitator can effectively collect a foreign material moved through sweeping of the agitator since the agitator rotates from a front side to a rear side. 
     Eighthly, according to the present disclosure, by disposing an agitator close to a center of a body in a structure in which the agitator and a dust housing are integrated with each other, the agitator is not disturbed by an external obstacle and a width of the agitator in a left-right direction can be maximized. Thereby, a cleaning area can be maximized, a body can escape quickly when trapped in the obstacle, and the body can rotate easily. 
     Ninthly, according to the present disclosure, rotation of a cleaner can be easy by a circular shape of a body. A size of an area to be cleaned by a spin mop at once can be maximized and rotation of a body is not disturbed by a shape of the spin mop when the body rotates, since rotation axes of a pair of spin mops are eccentrical or deviated from a center of the body and a part of each spin mop is overlapped with the body vertically. That is, a part of each spin mop is exposed to an outside of the body. Even if the spin mop is exposed to the outside of the body, the spin mop has a circular shape, and thus, friction between an obstacle and the spin mop is reduced when the body rotates. Accordingly, the rotation of the body can be easy. 
     Tenthly, according to the present disclosure, a body has a circular shape and a dry-type module does not protrude to an outside of the body. Accordingly, the cleaner can be freely rotated at any position in a cleaning area. Also, an agitator can have a sufficiently large width, and thus, a cleaning range can be wide. Further, a mopping operation while collecting a foreign material having a relatively large size can be performed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of a cleaner according to a first embodiment of the present disclosure. 
         FIG.  2    is a left side view of the cleaner shown in  FIG.  1   . 
         FIG.  3    is a bottom perspective view of the cleaner shown in  FIG.  1   . 
         FIG.  4    is a front cross-sectional view of the cleaner shown in  FIG.  1   . 
         FIG.  5    is a perspective view of a sweep module shown in  FIG.  3   . 
         FIG.  6    is a bottom perspective view of the sweep module shown  FIG.  5   . 
         FIG.  7    is a right cross-sectional view of the sweep module shown in  FIG.  5   . 
         FIG.  8    is an exploded perspective view of the sweep module shown in  FIG.  3   . 
         FIG.  9    is an exploded perspective view of the sweep module viewed from a right side of  FIG.  8   . 
         FIG.  10    is a partially exploded perspective view of the sweep module shown in  FIG.  5   . 
         FIG.  11    is a plan view of the cleaner of  FIG.  1    in a state that a case is removed. 
         FIG.  12    is a bottom view of the cleaner shown in  FIG.  11   . 
         FIG.  13    is a right cross-sectional view of the cleaner shown in  FIG.  11   . 
         FIG.  14    is a horizontal cross-sectional view showing an inside of an installation space of the cleaner shown in  FIG.  1   . 
         FIG.  15    is an enlarged perspective view of a first lever shown in  FIG.  8   . 
         FIG.  16    is an enlarged perspective view of a second lever shown in  FIG.  9   . 
         FIG.  17    is an enlarged perspective view of the second lever viewed from a left side of  FIG.  16   . 
         FIG.  18    is a partially exploded perspective view of the sweep module showing a coupled structure of an agitator shown in  FIG.  5   . 
         FIG.  19    is an exploded perspective view showing an assembled structure of a driven coupling shown in  FIG.  18   . 
         FIG.  20    is a perspective view viewed from a left side of  FIG.  19   . 
         FIG.  21    is a right cross-sectional view showing the agitator of  FIG.  18   . 
         FIG.  22    is an exploded perspective view of a driving unit viewed from a left side of  FIG.  18   . 
         FIG.  23    is an exploded perspective view of a dust housing shown in  FIG.  5   . 
         FIG.  24    is an enlarged view of a dustpan shown in  FIG.  23   . 
         FIG.  25    is an exploded perspective view of the dust housing shown in  FIG.  5    when viewed from an upper left side. 
         FIG.  26    is an exploded perspective view of the dust housing shown in  FIG.  5    when viewed from a lower left side. 
         FIG.  27    is an exploded perspective view of the dust housing shown in  FIG.  5    when viewed from a rear side. 
         FIG.  28    is an exploded perspective view of the dust housing shown in  FIG.  5    when viewed from a lower front side. 
         FIG.  29    is a cross-sectional view showing a dustpan stopper shown in  FIG.  7   . 
         FIG.  30    is an exemplary operation view of the dustpan according to the first embodiment of the present disclosure. 
         FIG.  31    is a bottom view showing the cleaner of FIG. for explaining a weight center and lowest ends of spin mops according to the present disclosure. 
         FIG.  32    is a plan view of the cleaner of  FIG.  1    viewed from an upper side in a state that a case is removed from the body for explaining the weight center according to the present disclosure. 
         FIG.  33    is a bottom view of a cleaner according to another embodiment of the present disclosure for explaining a relationship between a weight center and other components. 
     
    
    
     DETAILED DESCRIPTION 
     Expressions referring to directions such as a front direction (a frontward direction or a forward direction) (F), a rear direction (a rearward direction) (R), a left direction (a leftward direction) (Le), a right direction (a rightward direction) (Ri), an upper direction (an up direction or an upward direction) (U), and a down direction (an downward direction) (D), or so on may be defined base on a driving direction of a cleaner (a vacuum cleaner). This is just for explaining the present disclosure with reference to the accompanying drawings to be clearly understood. Therefore, directions may be defined differently depending on where a reference is placed. 
     For example, a direction parallel to an imaginary line connecting a central axis of a left spin mop and a central axis of a right spin mop may be defined as a left-right direction. A direction perpendicular to the left-right direction and parallel to the central axes of the spin mops or has an error angle within 5 degrees with the central axes of the spin mops may be defined as an up-down direction or a vertical direction. A direction perpendicular to each of the left-right direction and the up-down direction may be defined as a front-back direction or a longitudinal direction. A front direction may mean a main traveling direction of a mobile robot or a main traveling direction of a pattern traveling of a mobile robot. In this instance, the main traveling direction may mean a vector sum value of directions traveling in a predetermined time. 
     A term of ‘first’, ‘second’, ‘third’, or so on in front of a component mentioned below is only to avoid confusion between the component being referred to and other component, and does not relate to an order, an importance, or a master-servant relationship between components. For example, an embodiment only having a second component without a first component may be possible. 
     A term of ‘a mop’ mentioned hereinafter may have any of materials such as fabric or paper, and may be a multi-use product being able to be used repeatedly through washing or a disposable product. 
     The present disclosure may be applied to a cleaner (for example, a vacuum cleaner) manually moved by a user or a robot cleaner traveling or driving on its own. Hereinafter, an embodiment will be described based on a robot cleaner. 
       FIG.  1    is a perspective view of a cleaner according to a first embodiment of the present disclosure.  FIG.  2    is a left side view of the cleaner shown in  FIG.  1   .  FIG.  3    is a bottom perspective view of the cleaner shown in  FIG.  1   .  FIG.  4    is a front cross-sectional view of the cleaner shown in  FIG.  1   . 
     Referring to  FIG.  1    to  FIG.  4   , a cleaner  1  according to an embodiment of the present disclosure may include a body  30  having a controller. The cleaner  1  may include a mop module  40  to mop a floor (a surface to be cleaned) while being in contact with the floor. The cleaner  1  may include a sweep module  2000  provided to collect a foreign material on the floor. 
     The mop module  40  may be disposed at a lower side of the body  30  and may support the body  30 . The sweep module  2000  may be disposed at the lower side of the body  30  and may support the body  30 . In the present embodiment, the body  30  may be supported by the mop module  40  and the sweep module  2000 . The body  30  may form an appearance or an exterior. The body  30  may be arranged to connect the mop module  40  and the sweep module  2000 . 
     The mop module  40  may form an appearance or an exterior. The mop module  40  is disposed at the lower side of the body  30 . The mop module  40  is disposed at a rear side of the sweep module  2000 . The mop module  40  provides driving force for a movement of the cleaner  1 . In order to move the cleaner  1 , the mop module  40  may be preferably disposed at the rear side of the cleaner  1 . 
     The mop module  40  may be provided with at least one mop portion  411  to mop the floor while rotating. The mop module  40  may include at least one spin mop  41 , and the spin mop  41  may rotate in a clockwise direction or a counterclockwise direction when viewed from an upper side. The spin mop  41  may be in contact with the floor. 
     In the present embodiment, the mop module  40  may include a pair of spin mops  41   a  and  41   b . The pair of spin mops  41   a  and  41   b  may rotate in a clockwise direction or a counterclockwise direction when viewed from an upper side, and may mop the floor through rotation. When the pair of spin mops  41   a  and  41   b  are viewed from a traveling direction of the cleaner, a spin mop disposed at a left side may be referred to as a left spin mop  41   a , and a spin mop disposed at a right side may be defined as a right spin mop  41   b.    
     Each of the left spin mop  41   a  and the right spin mop  41   b  may be rotated with respect to its rotation axis. The rotation axis may be arranged in an up-down direction. The left spin mop  41   a  and the right spin mop  41   b  may be rotated independently of each other. 
     Each of the left spin mop  41   a  and the right spin mop  41   b  may include a mop portion  411 , a rotating plate  412 , and a spin shaft  414 . Each of the left spin mop  41   a  and the right spin mop  41   b  may include a water container (a water receiving portion)  413 . 
     The left spin mop  41   a  and the right spin mop  41   b  may be rotatably installed on a lower portion of the body  30 , be in contact with a floor, and move the body  30 . 
     Rotation axes osa and osb (see  FIG.  31   ) of the pair of spin mops may cross a lower surface of the body and be vertically overlapped with the body. The rotation axes osa and osb of the pair of spin mops may be eccentrical or deviated from a center of the body, and a part of the left spin mop  41   a  and a part of the right spin mop  41   b  may be vertically overlapped with the body  30 . 
     Therefore, according to the present disclosure, rotation of the body is not hindered or disturbed by a shape of the spin mop when the body rotates. That is, when a part of each spin mop is exposed to an outside of the body, the spin mop has a circular shape, and thus, friction between an obstacle and the spin mop is reduced when the body rotates. Accordingly, the rotation of the body can be easy. 
     That is, if entire portions of the left spin mop  41   a  and right spin mop  41   b  overlap vertically with the body  30 , rotational motion of the body  30  is easy, but an area to be cleaned at once is too small. Thus, according to the present disclosure, the left spin mop  41   a  and the right spin mop  41   b  may be exposed at the outside of the body  30  to a degree that it does not disturb the rotation of the body  30 , and an area to be cleaned by the left spin mop  41   a  and the right spin mop  41   b  can be maximized. 
     A ratio of an area where the left spin mop  41   a  or the right spin mop  41   b  is vertically overlapped with the body may be preferably 85% to 95% of each spin mop. Considering a relationship with a sweep module, a position where each spin mop is exposed may be preferably positioned between a lateral side and a rear side of the body  30 . A distance between a center of the body  30  and the rotation axis osa of the left spin mop  41   a  may be the same as a distance between the center of the body  30  and the rotation axis osb of the right spin mop  41   b.    
     The sweep module  2000  may form an appearance or an exterior. The sweep module  2000  may be disposed at a front side of the mop module  40 . In order to prevent a foreign material on the floor from first contacting the mop module  40 , the sweep module  2000  may preferably disposed at the front side of the cleaner  1  in a traveling direction. 
     The sweep module  2000  may be spaced apart from the mop module  40 . The sweep module  2000  may disposed at the front side of the mop module  40  and be in contact with the floor. The sweep module  2000  may be installed on a lower portion of the body  30 . 
     The sweep module  2000  may be completely overlapped with the body  30  vertically. In this instance, the phrase of “the sweep module  2000  is completely overlapped with body  30  vertically” may mean that an entire portion of the sweep module  2000  is vertically overlapped with the body  30  and the sweep module  2000  is not exposed to an outside of the body  30  when viewed from an upper side. 
     The sweep module  2000  may be in contact with the floor and may collect the foreign material at the front side of the sweep module  2000  to an inside when the cleaner  1  moves. The sweep module  2000  may be disposed at a lower side of the body  30 . A width of the sweep module  2000  in a left-right direction may be smaller than a width of the mop module  40  in the left-right direction. 
     The body  30  may include a case  31  forming an appearance or an exterior and a base  32  disposed at a lower side of the case  31 . An outer surface of the body  30  may form at least a part of a circle having a radius having an error with a reference radius within a reference error range. Specifically, when viewed from a vertical direction, 50% or more of the body  30  may form a part of a circular shape, and the remaining portion of the body  30  may have a shape close to a circular shape in consideration of coupling with other components or elements. In this instance, the circular shape may not mean a complete circle of mathematical meaning, but may mean a circle of engineering meaning with error. 
     The case  31  may form a side surface and an upper surface of the body  30 . The base  32  may form a bottom surface of the body  30 . 
     In the present embodiment, the case  31  may have a cylindrical shape with an open bottom surface. When viewed in a top view, an overall shape of the case  31  may be a circular shape. Since the case  31  has a plane shape of a circular shape, a rotation radius when rotating can be minimized. An outer surface of the case  31  may form at least a part of a circle having a radius having an error with a reference radius within a reference error range. 
     The case  31  may include an upper wall  311  having an overall shape in a circular shape, and a side wall  312  formed integrally with the upper wall  311  and extending downward from an edge of the upper wall  311 . 
     A part of the sidewall  312  may be open. An opened portion of the side wall  312  may be defined as a water-tank insertion opening (a water-tank insertion hole or a water-tank insertion portion)  313 , and a water tank  81  may be detachably installed through the water-tank insertion opening  313 . The water-tank insertion opening  313  may be disposed at a rear side based on the traveling direction of the cleaner. Since the water tank  81  is inserted through the water-tank insertion opening  313 , the water-tank insertion opening  313  may be preferably disposed close to the mop module  40 . 
     The mop module  40  may be coupled to the base  32 . The sweep module  2000  may be coupled to the base  32 . A controller Co and a battery Bt may be disposed in an inner space formed by the case  31  and the base  32 . In addition, a mop driving unit (a mop driver)  60  may be disposed on the body  30 . A water supply module  80  may be disposed at the body  30 . 
     The base  32  may include a base body  321 , a base guard  322 , and an insertion hole  323 . The base body  321  may cover the opened bottom surface of the case  31 . The base guard  322  may be formed along an outer edge of the base body  321  and protrude downward from the edge of the base body  321 . The insertion hole  323  may penetrate through the base body  321  in an up-down direction, and the sweep module  2000  may be detachably inserted into the insertion hole  323 . 
       FIG.  5    is a perspective view of the sweep module shown in  FIG.  3   .  FIG.  6    is a bottom perspective view of the sweep module shown  FIG.  5   .  FIG.  7    is a right cross-sectional view of the sweep module shown in  FIG.  5   .  FIG.  8    is an exploded perspective view of the sweep module shown in  FIG.  3   .  FIG.  9    is an exploded perspective view of the sweep module viewed from a right side of  FIG.  8   .  FIG.  10    is a partially exploded perspective view of the sweep module shown in  FIG.  5   . 
     With reference to  FIG.  5    to  FIG.  10   , the sweep module  2000  may be detachably mounted or installed on the body  30  through the insertion hole  323 . The sweep module  2000  may be positioned at a front side than the mop module  40  and collect a foreign material at the front side of the mop module  40 . The sweep module  2000  may be detachably assembled with the base  32 . The sweep module  2000  in an assembled state with the base  32  may be separated from the base  32  through a lever  2500 . 
     An installation space  325  in which the sweep module  2000  is mounted is formed at the base  32 . In the present embodiment, a storage housing  326  forming the installation space  325  may be further provided. The storage housing  326  may be assembled with the base  32  and may be disposed at an upper side of the insertion hole  323 . 
     The storage housing  326  may protrude to an upper side from the base body  321 . 
     A lower side of the storage housing  326  may be opened to communicate with the insertion hole  323 . An interior space of the storage housing  326  provides the installation space  325 . The installation space  325  of the storage housing  326  corresponds to a shape of the sweep module  2000 . 
     The sweep module  2000  may include a dust housing  2100 , an agitator  2200 , a driving unit  2300 , a driving coupling  2320 , a driven coupling  2220 , and a lever  2500 . The dust housing  2100  may be detachably assembled with the body  30 , and a foreign material may be stored in the dust housing  2100 . The agitator  2200  may be rotatably assembled with the dust housing  2100 . The driving unit  2300  may be installed on the body  30  and provide rotational force to the agitator  2200 . The driving coupling  2320  may be disposed at the driving unit  2300  and transmit the rotational force of the driving unit  2300  to the agitator  2200 . The driven coupling  2220  may transmit the rotational force of the driving coupling  2320  to the agitator  2200 . The lever  2500  may be disposed at the dust housing  2100 . The lever  2500  may couple or separate the driving coupling  2320  and the driven coupling  2220  by receiving operation force. 
     The dust housing  2100  accommodates the agitator  2200 . A foreign material collected through the rotation of the agitator  2200  may be stored in the dust housing  2100 . That is, the dust housing  2100  provides an installation and operation structure of the agitator  2200 , and also provides a storage space for a foreign material. 
     The dust housing  2100  may include a collection space  2102  for a rotation of the agitator  2200  and a storage space  2104  for storing a foreign material. The dust housing  2100  may longitudinally extend in a left-right direction. A width of the dust housing  2100  may be narrower than a width of the mop module  40 . 
     The dust housing may be formed by separately fabricating a structure for the collection space  2102  and a structure for the storage space  2104  and assembling them each other. In the present embodiment, the collection space  2102  and the storage space  2104  are disposed in the dust housing  2100 , and a partition  2145  for partitioning the collection space  2102  and the storage space  2104  may be disposed. 
     In the present embodiment, the dust housing  2100  may include an upper housing  2110 , a lower housing  2140 , a dust cover  2150 . The upper housing  2110  may provide an upper outer shape. The lower housing  2140  may be disposed at a lower side of the upper housing  2110  and be coupled to the upper housing  2110 . The dust cover  2150  may detachably assembled with at least one of the upper housing  2110  and the lower housing  2140 . 
     The collection space  2102  and the storage space  2104  are formed by assembling the upper housing  2110  and the lower housing  2140 . That is, the upper housing  2110  may provide an upper partial space of the collection space  2102  and an upper partial space of the storage space  2104 , and the lower housing  2140  may provide the remaining lower space of the collection space  2102  and the remaining lower space of the storage space  2014 . 
     In the present embodiment, the collection space  2102  may be positioned at a rear side of the storage space  2104 . 
     That is, the storage space  2104  is positioned at a front side of the collection space  2102 , and the dust cover  2150  is positioned at a front side than the upper housing  2110 . 
     In addition, the storage space  2014  may be disposed at a front side of the agitator  2200 . When the body of the cleaner has a circular shape or a shape close to a circular shape, rotation in place is easy. When the rotation in place is easy, the cleaner can easily escape from an obstacle area or a corner. However, when the body of the cleaner has a circular shape, a width of an agitator is limited to be smaller than a diameter of the body so that the agitator is not disturbed by the obstacle during the body rotates. Accordingly, in the present disclosure, rotation of the body can be easy by limiting the width of the agitator to be smaller than the diameter of the body. Also, the width of the agitator can be maximized in a state that the agitator does not protrude from the body by disposing the storage space that stores a foreign material collected from the agitator at a front side than the agitator. Therefore, a size of an area to be cleaned at once is not reduced. 
     The upper housing  2110  and the lower housing  2140  may be integrally assembled. The upper housing  2110  and the lower housing  2140  that are integrally assembled may be defined as a housing assembly  2001 . 
     The dust cover  2150  is detachably assembled with the housing assembly. When the dust cover  2150  is separated from the housing assembly, the storage space  2104  is exposed to an outside. The foreign material stored in the storage space  2104  may be discarded when the dust cover  2150  is separated. 
     The upper housing  2110  provides an upper surface, a left upper surface, a right upper surface, and a rear surface of the dust housing  2100 . The upper housing  2110  forms an upper side of the collection space  2102  and the storage space  2104 . The upper housing  2110  provides upper partial portions of the collection space  2102  and the storage space  2104 . 
     The upper housing  2110  may include a first upper housing portion  2112 , a second upper housing portion  2114 , a third upper housing portion  2116 , and a fourth housing portion  2118 . The first upper housing portion  2112  may form an upper wall of the storage space  2104 . The second upper housing portion  2114  may be integrally connected with the first upper housing portion  2112  and forms an upper wall and a rear wall of the collection space  2102 . The third upper housing portion  2116  may provide a part of a left wall of the collection space  2102  and the storage space  2104 , and the fourth upper housing portion  2118  may provide a part of a right wall of the collection space  2102  and the storage space  2104 . 
     A shape of the first upper housing  2112  is not limited. However, since the second upper housing portion  2114  accommodates the agitator  2200 , the second upper housing portion  2114  may have a shape corresponding to a shape of the agitator  2200 . 
     At least a part of the second upper housing portion  2114  may have a curvature center at a rotation axis of the agitator  2200 . At least a part of the second upper housing portion  2114  may have an arc shape. 
     In the present embodiment, the second upper housing portion  2114  may have a radius of curvature R 1  greater than a diameter of the agitator  2200 . An outer edge of the agitator  2200  may be preferably in contact with an inner surface of the second upper housing portion  2114 . 
     A foreign material collected through a contact of the agitator  2200  and the second upper housing portion  2114  may be moved to the storage space  2104  along the inner surface of the second upper housing portion  2114 . When the agitator  2200  and the second upper housing  2114  are spaced apart from each other, the foreign material collected by the agitator  2200  may fall back to the floor. 
     A collection opening surface  2101  may be formed at the lower housing  2140 . The collection opening surface  2101  may be exposed to the floor. The agitator  2200  may penetrate the collection opening surface  2101  and protrude to a down side than the collection opening surface  2101 . 
     The collection opening surface  2101  may be disposed at a rear side than the storage space  2102 . 
     The lower housing  2140  may be disposed at a lower side of the upper housing  2110  and may be spaced apart from the upper housing  2110  to form a storage opening surface  2103 . In the present embodiment, the lower housing  2140  and the upper housing  2110  may be spaced apart from each other in the up-down direction. 
     The lower housing  2140  may include a first lower housing portion  2142 , a third lower housing portion  2146 , a fourth lower housing portion  2148 , and a partition  2145 . The first lower housing portion  2142  may form a lower wall of the storage space  2104  and has the collection opening surface  2101  where the foreign material is collected. The third lower housing portion  2146  may provide a rest of the left wall of the collection space  2102  and the storage space  2104 , and the fourth lower housing portion  2148  may provide a rest of the right wall of the collection space  2102  and the storage space  2104 , The partition  2145  may be integral with the first lower housing portion  2142 , and may partition the collection space  2102  and the storage space  2104 . 
     In the present embodiment, the first lower housing portion  2142 , the third lower housing portion  2146 , the fourth lower housing portion  2148 , and the partition  2145  may be formed to have an integral structure. Unlike the present embodiment, any one of the first lower housing portion  2142 , the third lower housing portion  2146 , the fourth lower housing portion  2148 , or the partition  2145  may be separately manufactured and then be assembled. 
     A left wall  2011  of the housing assembly  2001  may be provided through assembling the third lower housing portion  2146  and the third upper housing portion  2116 . A right wall  2012  of the housing assembly  2001  may be provided through assembling the fourth lower housing portion  2148  and the fourth upper housing portion  2118 . 
     A left rotation axis of the agitator  2200  may penetrate the left wall  2011  of the housing assembly, and a right rotation axis of the agitator  2200  may penetrate the right wall  2012  of the housing assembly. 
     The partition  2145  may protrude to an upper side from the first lower housing portion  2142 . A length of the partition  2145  in the left-right direction may correspond to or relate to a length of the agitator  2200  in the left-right direction. The length of the partition  2145  in the left-right direction may be greater than the length of the agitator  2200  in the left-right direction. 
     The partition  2145  may include a first partition portion  2145   a  and a second partition portion  2145   b . The first partition portion  2145   a  may protrude to an upper side from the first lower housing portion  2142 , form the collection opening surface  2101 , and partition the collection space  2102  and the storage space  2104 . The first partition portion  2145   a  may be not in contact with the agitator  2200 . The second partition portion  2145   b  may extend to an upper side from the first partition portion  2145   a , partition the collection space  2102  and the storage space  2104 , and be in contact with the agitator  2200 . 
     The first partition portion  2145   a  may protrude to the upper side from the first lower housing portion  2142 . The collection opening surface  2101  may be formed between the first partition portion  2145   a  and a rear end  2140   b  of the first lower housing portion  2142 . 
     A length L 1  of the collection opening surface  2101  in a front-rear direction may be smaller than a diameter of the agitator  2200 . Since the length L 1  of the collection opening surface  2101  in the front-rear direction is smaller than the diameter of the agitator  2200 , the agitator  2200  cannot be drawn out to an outside through the collection opening surface  2101 . 
     The agitator  2200  may be mounted on an upper side of the lower housing portion  2140 , and a lower end of the agitator  2200  may protrude to an outside of the collection opening surface  2101  and thus may be in contact with the floor. 
     The first partition portion  2145   a  may be not in contact with the agitator  2200 . 
     However, the second partition portion  2145   b  may be in contact with the agitator  2200 . 
     The second partition portion  2145   b  may have an arc shape. A curvature center of the second partition  2145   b  may be positioned at a rotation axis Ax of the agitator  2200 . A radius of curvature R 2  of the second partition  2145   b  may be equal to or smaller than a diameter of the agitator  2200 . 
     The second partition portion  2145   b  may have a curved surface facing the agitator  2200 . An upper end  2147   a  of the second partition portion  2145   b  may be positioned higher than the rotation axis Ax of the agitator  2200 . 
     The upper end  2147   a  of the second partition portion  2145   b  may protrude to a rear side of the first partition portion  2145   a.    
     The upper end  2147   a  of the second partition portion  2145   b  may be sharply formed. An inclined surface  2147   b  may be formed at the upper end  2147   a  of the second partition portion  2145   b . The inclined surface  2147   b  may separate a foreign material attached to a surface of the agitator  2200  and guide the foreign material to the storage space  2104 . 
     When assembling the upper housing  2110  and the lower housing  2140 , a discharge surface  2105  that is opened to a front side may be formed. The discharge surface  2105  may be formed at a front surface of the housing assembly  2001 , and a dust cover  2150  may open and close the discharge surface  2105 . 
     The dust cover  2150  may be disposed at a front side of the housing assembly  2001  and may cover the discharge surface  2105 . The foreign material in the storage space  2104  may be discharged to an outside of the sweep module  2000  through the discharge surface  2105 . 
     The dust cover  2150  may be detachably assembled with the housing assembly  2001 . In the present embodiment, the dust cover  2150  and the housing assembly  2001  may be assembled through a mutually-engaged structure (a mutually-fastened structure, a mutually-locked structure, or a mutually-hooked structure). The mutually-engaged structure may be released by operation force of a user. 
     For the mutually-engaged structure of the dust cover  2150  and the housing assembly  2001 , a protrusion  2151  may be formed at one of the dust cover  2150  and the housing assembly  2001 , and an engaged groove  2152  may be formed at the other of the dust cover  2150  and the housing assembly  2001 . 
     In the present embodiment, the engaged groove  2152  is formed at the dust cover  2150 , and the protrusion  2151  is formed at the housing assembly  2001 . 
     A number of engaged grooves  2152  corresponds to a number of protrusions  2151 . A plurality of protrusions  2151  may be disposed. The protrusions  2151  may be disposed at the upper housing  2110  and the lower housing  2140 , respectively. 
     In the present embodiment, two protrusions  2151  are disposed at the upper housing  2110 , and two protrusions  2151  are also disposed at the lower housing  2140 . 
     If it is necessary to distinguish, protrusions disposed at the upper housing  2110  are referred to as upper protrusions  2151   a  and  2151   b , and protrusions disposed at the lower housing  2140  are referred to as lower protrusions  2151   c  and  2151   d.    
     The upper protrusions  2151   a  and  2151   b  protrude to an upper side at an upper surface of the upper housing  2110 . The lower protrusion  2151   c  and  2151   d  protrude to a lower side at a bottom surface of the lower housing  2140 . 
     At the dust cover  2150 , upper engaged grooves  2152   a  and  2152   b  corresponding to the upper protrusions  2151   a  and  2151   b  are formed, and lower engaged groove  2152   c  and  2152   d  corresponding to the lower protrusions  2151   c  and  2151   d  are formed. 
     The dust cover  2150  may include a front cover portion  2153 , a top cover portion  2154 , a left cover portion  2155 , and a right cover portion  2156 , and a bottom cover portion  2157 . The front cover portion  2153  may be disposed to face the discharge surface  2105 . The top cover portion  2154  may protrude from an upper edge of the front cover portion  2153  toward the housing assembly. The left cover portion  2155  may protrude from a left edge of the front cover portion  2153  toward the housing assembly, and the right cover portion  2156  may protrude from a right edge of the front cover portion  2153  toward the housing assembly. The bottom cover portion  2157  may protrude from a lower edge of the front cover portion  2153  toward the housing assembly side. 
     The dust cover  2150  may have a concave insertion space from a rear side to a front side. The left cover portion  2155  and the right cover portion  2156  may be arranged to be inclined toward the front side. 
     The upper engaged groove  2152   a  and  2152   b  are formed at the top cover portion  2154 . The lower engaged groove  2152   c  and  2152   d  are formed at the bottom cover portion  2157 . The upper engaged groove  2152   a  and  2152   b  and the lower engaged groove  2152   c  and  2152   d  may be preferably disposed to be opposite to each other. 
     The upper engaged groove  2152   a  and  2152   b  or the lower engaged groove  2152   c  and  2152   d  may have a shape of a groove or a hole. 
     The housing assembly  2001  may have an insertion portion  2160  being inserted into the insertion space and being in close contact with an inner surface of the dust cover  2150 . The insertion portion  2160  may be located at a front side of the upper housing  2110  and the lower housing  2140 . 
     The insertion portion  2160  may include a top insertion portion  2164 , a left insertion portion  2165 , a right insertion portion  2166 , and a bottom insertion portion  2167 . The top insertion portion  2164  may form an upper side of the discharge surface  2105  and protrude to a front side. The left insertion portion  2165  may form a left side of the discharge surface  2105  and protrude to a front side. The right insertion portion  2166  may form a right side of the discharge surface  2105  and protrude to a front side. The bottom insertion portion  2167  may form a lower side of the discharge surface  2105  and protrude to a front side. 
     In the present embodiment, the top insertion portion  2164 , the left insertion portion  2165 , the right insertion portion  2166 , and the bottom insertion portion  2167  are connected. Unlike the present embodiment, the top insertion portion  2164 , the left insertion portion  2165 , the right insertion portion  2166 , and the bottom insertion portion  2167  may be separated. An area of the insertion portion  2160  may become narrower as it goes from a rear side to a front side. 
     The top insertion portion  2164  may be in close contact with the top cover portion  2154 , the left insertion portion  2165  may be in close contact with the left cover portion  2155 , the right insertion portion  2166  may be in close contact with the right cover portion  2156 , and the bottom insertion portion  2167  may be in close contact with the bottom cover portion  2157 . 
     In the present embodiment, the upper protrusions  2151   a  and  2111   b  are formed at the top insertion portion  2164 , and the lower protrusions  2151   c  and  2151   d  are formed at the bottom insertion portion  2167 . 
     The upper protrusions  2151   a  and  2151   b  may be inserted into the upper engaged groove  2152   a  and  2152   b  from a lower side to an upper side of the upper engaged groove  2152   a  and  2152   b  to form a mutually-engaged structure. The lower protrusions  2151   c  and  2151   d  may be inserted into the lower engaged groove  2152   c  and  2152   d  from an upper side to a lower side of the lower engaged groove  2152   c  and  2152   d  to form a mutually-engaged structure. 
     By operation force of a user to pull the dust cover  2150 , the dust cover  2150  or the insertion portion  2160  is elastically deformed and thus the mutually-engaged structure is released. 
     The agitator  2200  may be disposed to be rotated in the housing assembly  2001 . 
     The agitator  2200  may be disposed between the upper housing  2110  and the lower housing  2140 . The agitator  2200  may be disposed at the upper housing  2110 . In the present embodiment, the agitator  2200  is disposed at the lower housing  2140  and rotates while being supported by the lower housing  2140 . 
     A rotation axis of the agitator  2200  is disposed in the left-right direction and the agitator  2200  may rotate forward or backward. 
     The housing assembly  2001  may further include a first journal  2010  and a second journal  2020  supporting the agitator  2200 . The first journal  2010  is disposed at a left side of the housing assembly  2001 , and the second journal  2020  is disposed at a right side of the housing assembly  2001 . 
     The first journal  2010  and the second journal  2020  penetrate the housing assembly  2001  in the left-right direction and communicate with the collection space  2102 . 
     In the present embodiment, the first journal  2010  and the second journal  2020  may have a cylindrical shape. Unlike the present embodiment, at least one of the first journal and the second journal may have a semi-cylindrical shape. When the first journal and the second journal have a semi-cylindrical shape, the first journal and the second journal are arranged to support the rotation axis of the agitator  2200  at a lower side. 
     The dust housing  2100  may be mounted on the installation space  325  of the base  32 , and a lever  2500  may be disposed to couple or separate the base  32  and the dust housing  2100 . 
       FIG.  11    is a plan view of the cleaner of  FIG.  1    in a state that a case is removed.  FIG.  12    is a bottom view of the cleaner shown in  FIG.  11   .  FIG.  13    is a right cross-sectional view of the cleaner shown in  FIG.  11   .  FIG.  14    is a horizontal cross-sectional view showing an inside of an installation space of the cleaner shown in  FIG.  1   . 
     Referring to  FIG.  11    to  FIG.  14   , the sweep module  2000  may further include a housing elastic member  327  that provides elastic force to the dust housing  2100 . The housing elastic member  327  may be disposed at the installation space  325 . 
     The housing elastic member  327  may be disposed at the base  32 , and more particularly, may be installed on the storage housing  326 . In the present embodiment, the housing elastic member  327  may be a plate spring. In order to install the housing elastic member  327  of the plate spring, an installation structure for fitted-fixing may be disposed at the storage housing  326 . 
     The housing elastic member  327  may elastically support an upper surface of the dust housing  2100 . 
     The storage housing  326  is provided with an elastic-member storage portion  328  that protrudes to an upper side to have a convex shape at the installation space  325 . An elastic-member storage space  328   b  in which the housing elastic member  327  is accommodated may be formed at a lower side of the elastic-member storage portion  328 . 
     The elastic member storage portion  328  may further include an elastic-member opening surface  328   a  opened in an up-down direction. The elastic-member opening surface  328   a  may communicate with the elastic-member storage space  328   b  and the installation space  325 . 
     In addition, an elastic-member support portion  329 , which is disposed at a lower side of the elastic-member storage space  328   b  and is connected to the storage housing  326 , may be further disposed. 
     The elastic-member support portion  329  may be positioned at a lower side than the elastic-member storage portion  328 . 
     The housing elastic member  327  may be inserted between the elastic-member storage portion  328  and the elastic-member support portion  329 . The housing elastic member  327  may be exposed to an upper side of the storage housing  326  through the elastic-member opening surface  328   a.    
     The housing elastic members  327  may be positioned at both sides of the elastic-member support portion  329 , respectively. 
     The elastic member storage portion  328  may longitudinally extend in the left-right direction, and the elastic-member support portion  329  may be disposed in the left-right direction. 
     The housing elastic member  327  may include a first elastic portion  327   a , a second elastic portion  327   b , and a third elastic portion  327   c . The first elastic portion  327   a  may be positioned at an upper side of the elastic-member support portion  329 . The second elastic portion  327   b  may extend to one side (a left side in the present embodiment) from the first elastic portion  327   a  and be disposed in the elastic-member storage space  328   b . The third elastic portion  327   c  may extend to the other side (a right side in the present embodiment) from the first elastic portion  327   a  and be disposed in the elastic-member storage space  328   b.    
     Each of the second elastic portion  327   b  and the third elastic portion  327   c  may be bent from the first elastic portion  327   a.    
     The second elastic portion  327   b  and the third elastic portion  327   c  may be positioned at a lower side of the elastic-member storage portion  328 . The second elastic portion  327   b  may be disposed to be inclined toward a left down side, and the third elastic portion  327   c  may be disposed to be inclined toward a right down side. 
     When the dust housing  2100  is inserted into the installation space  325 , the second elastic portion  327   b  and the third elastic portion  327   c  may elastically support an upper surface of the dust housing  2100 . 
     When the mutually-engaged structure of the dust housing  2100  and the base  32  is released by the first lever  2510  and the second lever  2520 , the second elastic portion  327   b  and the third elastic portion  327   c  push the dust housing  2100  to a lower side and moves the dust housing  2100  to an outside of the storage housing  326 . 
     By the elastic force of the housing elastic member  327 , a user can easily separate the dust housing  2100  from the installation space  325 . 
     Since the elastic-member support portion  329  supports the housing elastic member  327 , the housing elastic member  327  can be prevented from being separated to the installation space  325 . Even if the dust housing  2100  is repeatedly mounted and separated, the housing elastic member  327  is firmly supported by the elastic-member support portion  329 . 
     An arrangement of a collection space and a storage space of a sweep module will be described in more detail with reference to  FIG.  6   ,  FIG.  7   ,  FIG.  13   , and  FIG.  14   . 
     In the present embodiment, the body  30  may have a circular shape when viewed in a top view. More particularly, a front side or a front portion of the body  30  (a portion at a front side of a traveling direction) may have a circular shape. When a front side F of the body  30  has a circular shape, a rotational radius can be minimized. 
     More particularly, in the present embodiment, a diameter M of each spin mop  41   a  and  41   b  that moves the cleaner may be larger than a radius of the body  30 . When viewed in the top view, since the diameter M of each spin mop  41   a  and  41   b  is larger than the radius of the body  30 , a center O of the body  30  is positioned between the spin mops  41   a  and  41   b.    
     When the rotation radius of the body  30  is minimized, a volume of the body  30  can be maximized within the same rotation radius, and accordingly, an internal volume of the body  30  can be increased. As the internal volume of the body  30  increases, a volume of the water tank  81  or the storage space  2104  can become larger. 
     The sweep module  2000  may be positioned at a front side than the map module  40 . More particularly, the sweep module  2000  may be positioned at a front side than the spin mops  41   a  and  41   b , and the collection opening surface  2101  may be positioned at a front side than each spin mop  41   a  and  41   b . Since the foreign material on a floor is swept through the collection opening surface  2101 , each of the spin mops  41   a  and  41   b  should not be overlapped with the collection opening surface  2101 . Due to this arrangement, a width W 1  of the sweep module  2000  in a left-right direction may be smaller than a diameter of the body  30 . 
     In the present embodiment, the sweep module  2000  may have selectively detachable structure to the installation space  325  formed at the base  32 . 
     Thus, the storage space  2104  and the collection space  2102  of the sweep module  2000  may be disposed at an inside of the installation space  325 . The collection space  2102  may be disposed at a rear side than the storage space  2104 . When viewed in a top view, the collection space  2102  may be disposed closer to the center O of the body  30  than the storage space  2104 . 
     In the present embodiment, the collection space  2102  and the storage space  2104  may be disposed on the same plane. 
     In order to maximize a width of the agitator  2200  that determines a cleaning area, the agitator  2200  should be disposed close to the center O of the body  30 . 
     Since the collection space  2102  is disposed closer to the center O of the body  30  having a shape close to a circular shape when viewed in a top view, the storage space  2104  may be disposed at a front side than the collection space  2102 . 
     In the present embodiment, in a structure in which the mop module  40  is disposed at a rear side of the cleaner in the traveling direction and the sweep module  2000  is disposed at a front side of the mop module  40 , the storage space  2104  in which the foreign material is stored is positioned at a front side of the collection space  2102 . 
     The agitator  2200  is disposed in a left-right direction and rotated in a front-rear direction. In order to minimize interference with the rotated agitator  2200 , a length of the collection space  2102  in the front-right direction may be equal to or larger than a diameter of the agitator  2200 . 
     A maximum width of the sweep module  2000  in the left-right direction is defined as a maximum width W 1 , and a minimum width of the sweep module  2000  in the left-right direction is defined as a minimum width W 2 . The maximum width W 1  may be a width of the sweep module  2000  in the left-right direction when the first side cover  2170  and the second side cover  2180  of the dust housing  2100  are included. The minimum width W 2  may be a width of the front cover portion  2153  of the dust cover  2150  in the left-right direction. The minimum width W 2  may be positioned at a front side than the maximum width W 1 . 
     When viewed in a top view, since the body  30  may have a shape close to a circular shape, a front side of the sweep module  2000  positioned at a front side than the center O may have an arc shape. 
     Since the installation space  325  corresponds to the sweep module  2000 , a maximum width at a rear side of the installation space  325  may be equal to or larger than the maximum width W 1 , and a maximum width at a front side of the installation space  325  may be equal to or larger than the minimum width W 2 . 
     Since the collection space  2102  and the storage space  2104  are disposed at an inside of the sweep module  2000 , widths of the collection space  2102  and the storage space  2104  may be smaller than the maximum width W 1 . 
     A maximum width of the installation space  325  is defined as a maximum width S 1 , and a minimum width of the installation space  325  is defined as a minimum width S 3 . Since the collection space  2102  and the storage space  2104  are partitioned based on the partition  2145  of the dust housing  2100 , a width of the partition  2145  in the left-right direction is defined as a width S 2 . 
     The width S 2  of the partition  2145  may be smaller than the maximum width S 1  of the installation space  325  and may be larger than the minimum width S 3  of the installation space  325 . 
     Since the agitator  2200  is disposed at the collection space  2102 , a width Aw of the agitator  2000  in the left-right direction may be smaller than a maximum width of the collection space  2102 . 
     The width Aw of the agitator  2000  in the left-right direction may be greater than an interval of spin shafts  414  and may be smaller than a width W 1  of the installation space in the left-right direction. 
     Since the agitator  2200  is disposed at the collection space  2102 , when the width of the collection space  2102  in the left-right direction is maximized, the width Aw of the agitator  2000  in the left-right direction may be larger. When the width Aw of the agitator  2000  in the left-right direction is maximized, an area to be cleaned at once can be maximized. 
     In the present embodiment, since the partition  2145  partitions the collection space  2102  and the storage space  2014 , a front-side width S 2  of the collection space  2102  may be equal to a rear-side width S 2  of the storage space  2104 . 
     Unlike the present embodiment, the front-side width of the collection space  2102  and the rear-side width of the storage space  2104  may be different. In this case, a foreign material collected at both ends of the agitator  2200  may not be moved to the storage space  2014 . 
     In order to maximally utilize the width Aw of the agitator  2000  in the left-right direction, the rear-side width S 2  of the storage space  2104  may be the same as the front-side width S 2  of the collection space  2102 , as in the present embodiment. Due to a thickness of the dust housing  2100  in a manufacturing process, the rear-side width S 2  of the storage space  2104  may be slightly smaller. 
     The width Aw of the agitator  2000  in the left-right direction may be smaller than an interval between the left wall  2011  and the right wall  2012  of the dust housing  2100 . 
       FIG.  15    is an enlarged perspective view of the first lever shown in  FIG.  8   .  FIG.  16    is an enlarged perspective view of the second lever shown in  FIG.  9   .  FIG.  17    is an enlarged perspective view of the second lever viewed from a left side of  FIG.  16   . 
     Referring to  FIG.  9   ,  FIG.  10   , and  FIG.  15    to  FIG.  17   , the lever  2500  may be disposed between the base  32  and the dust housing  2100  and may form a mutually-engaged structure with respect to the base  32  and the dust housing  2100 . The lever  2500  may form a mutually-engaged structure with the dust housing  2100  in a direction of gravity and suppress the dust housing  2100  from being separated from a lower side of the base  32 . 
     A plurality of levers  2500  may be disposed, and form a mutually-engaged structure at a plurality of places of the dust housing  2100 . In the present embodiment, the lever  2500  includes a first lever  2510  and a second lever  2520 , and the first lever  2510  and the second lever  2520  are arranged in the left-right direction. 
     The first lever  2510  is disposed at a left side of the dust housing  2100 , and the second lever  2520  is disposed at a right side of the dust housing  2100 . 
     Operation mechanisms of the first lever  2510  and the second lever  2520  are the same, and only operation directions of the first lever  2510  and the second lever  2520  are opposite to each other. 
     The first lever  2510  disposed at the left side is moved to the right side to release the mutually-engaged structure with the base  32 , and the second lever  2520  disposed at the right side is moved to a left side to release the mutually-engaged structure with the base  32 . 
     The sweep module  2000  may include a first lever  2510 , a second lever  2520 , a first-lever elastic member  2541 , and a second-lever elastic member  2542 . The first lever  2510  may be disposed at one side of the housing assembly to be relatively movable in the left-right direction. The second lever  2520  may be disposed at the other side of the housing assembly to be relatively movable in the left-right direction. The first-lever elastic member  2541  may be disposed between the first lever  2510  and the dust housing  2100  and provide elastic force to the first lever  2510 . The second-lever elastic member  2252  may be disposed between the second lever  2520  and the dust housing  2100  and provide elastic force to the second lever  2520 . 
     Since the first lever  2510  and the second lever  2520  may have the same or similar structures, a structure of the first lever will be described as an example. 
     In the present embodiment, the dust housing  2100  may be provided with a first side cover  2170  covering or shielding the first lever  2510  and a second side cover  2180  covering or shielding the second lever  2520 . 
     Unlike the present embodiment, the first lever  2510  and the second lever  2520  may be exposed to an outside of the dust housing  2100  without the first side cover  2170  and the second side cover  2180 . Also, unlike the present embodiment, the first side cover  2170  may be disposed at a right side and the second side cover  2180  may be disposed at a left side. 
     The first side cover  2170  may be coupled to a left side of the housing assembly  2001 . The first side cover  2170  may have a shape corresponding to a left shape of the housing assembly  2001 . The first side cover  2170  may shield a shaft member  2201  of the agitator  2200  from being exposed to an outside. The first side cover  2170  may cover or shield most of the first lever  2510  and exposes only a portion for the mutually-engaged structure with the base  32 . 
     The first side cover  2170  may include a first side cover body  2173 , a through hole  2171  or  2172 , a hook portion  2174 , a journal-coupled portion  2175 , and a fastening portion  2176 . The first side cover body  2173  may be in close contact with one side of the housing assembly  2001 . The through hole  2171  or  2172  may be disposed to penetrate the first side cover body  2173 . The hook portion  2174  may protrude from the first side cover body  2173  toward the housing assembly  2001  and may be hooked-coupled with the housing assembly  2001 . The journal-coupled portion  2175  may protrude from the first side cover body  2173  toward the housing assembly  2001  and be mutually coupled to the journal  2010  (the first journal  2010  in the present embodiment). The fastening portion  2176  may couple the first side cover body  2173  and the housing assembly  2001  by a fastening member (not shown). 
     The fastening portion  2176  and the hook portion  2174  are disposed at opposite sides based on the journal-coupled portion  2175 . A plurality of hook portions  2174  may be arranged in an up-down direction. 
     The journal-coupled portion  2175  may be inserted into an inner diameter of the first journal  2010 . 
     The first lever  2510  may include an upper lever body  2512 , a lower lever body  2514 , and a lever engaging portion  2516 . The upper lever body  2512  may be disposed between the housing assembly  2001  and the first side cover  2170  and be elastically supported by the first-lever elastic member  2541 . The lower lever body  2514  may be disposed between the housing assembly  2001  and the first side cover  2170 , be integral with the upper lever body  2512 , be exposed to an outside of the housing assembly  2001 , and receive operation force of a user. The lever engaging portion  2516  may protrude from the upper lever body  2512  and be disposed to penetrate the through holes  2171  and  2172  of the first side cover  2170 . 
     The upper lever body  2512  may be disposed in an up-down direction, and the lower lever body  2514  may be disposed in a horizontal direction. 
     The lower lever body  2514  may be disposed to be exposed to an outside of the dust housing  2100 . The lower lever body  2514  may be positioned at a lower side of the upper lever body  2512 . The lower lever body  2514  may be exposed to an outside of a lower surface of the lower housing  2140 . 
     In the present embodiment, an operation portion  2519  protruding to a lower side from the lower lever body  2514  may further provided. Since the operation portion  2519  longitudinally extends in the front-rear direction, the operation portion  2519  may easily receive operation force of a user in the left-right direction. 
     A user may move the first lever  2510  by pushing the operation unit  2519  in the left-right direction. 
     The lever engaging portion  2516  may protrude from the upper lever body  2512  to an outside (a side opposite to the agitator). Since a number of the lever engaging portions  2516  corresponds to a number of through holes, a first lever engaging portion  2516   a  and a second lever engaging portion  2516   b  are disposed in the present embodiment. 
     The lever engaging portion  2516  has a structure that forms a mutually-engaged structure in a direction of gravity and minimizes forming a mutually-engaged structure in an opposite direction of gravity. Therefore, an upper surface of the lever engaging portion  2516  may have a round shape or an inclined surface to a lower side, and a lower surface of the lever engaging portion  2516  may have a flat surface. 
     If the levers  2510  and  2520  are not returned to initial positions when the levers  2510  and  2520  move, the sweep module  2000  may be separated from a fixed position because the mutually engaged structure is not formed. To prevent this, the sweep module  2000  may further include a structure for guiding a horizontal movement of the first lever  2510 . 
     The sweep module  2000  may include a first guide  2545 , a first guide hole  2518 , a second guide  2547 , and a second guide hole  2528 . The first guide  2545  may protrude to the first lever  2510  at one side (a left side in the present embodiment) of the dust housing  2100  and mutually interfere with the first lever  2510  to guide a movement direction of the first lever  2510 . The first guide hole  2518  may be formed at the first lever  2510 , and the first guide  2545  may be inserted into the first guide hole  2518  so that the movement of the first guide  2545  is guided. The second guide  2547  may protrude to the second lever  2520  at the other side (a right side in the present embodiment) of the dust housing  2100  and mutually interfere with the second lever  2520  to guide a movement direction of the second lever  2520 . The second guide hole  2528  may be formed at the second lever  2520 , and the second guide  2547  may be inserted to the second guide hole  2528  so that the movement of the second guide  2547  is guided. 
     The first guide  2545  may be formed in the movement direction of the first lever  2510 , and the second guide  2547  may be formed in the moving direction of the second lever  2520 . Thus, the first guide  2545  and the second guide  2547  may be formed in a horizontal direction. The first guide hole  2518  and the second guide hole  2528  may be formed in the horizontal direction to correspond to the first guide  2545  and the second guide  2547 . 
     The guide holes  2518  and  2528  may be disposed at either the upper lever body  2512  or the lower lever body  2514 . In the present embodiment, the guide holes  2518  and  2528  are formed to penetrate the upper lever body  2512  in the horizontal direction. 
     One end of the first-lever elastic member  2541  is supported by the dust housing  2100 , and the other end of the first-lever elastic member  2541  is supported by the first lever  2510 . The first-lever elastic member  2541  elastically supports the first lever  2510  toward an outside of the dust housing  2100 . 
     The sweep module  2000  may further include a structure for preventing displacement of the lever elastic members  2541  and  2542 . 
     In order to maintain an operation position of the first-lever elastic member  2541 , the sweep module  2000  may include a first position fixing portion  2517  and a second position fixing portion  2544 . The first position fixing portion  2517  may be disposed at the first lever  2510  and may be inserted into the other end of the first-lever elastic member  2541 . The second position fixing portion  2544  may be disposed at the dust housing  2100  and one end of the first-lever elastic member  2541  may be inserted into the second position fixing portion  2544 . 
     In the present embodiment, the first-lever elastic member  2541  and the second-lever elastic member  2542  may be formed of a coil spring. In the present embodiment, the first position fixing portion  2517  may have a boss shape, and the second position fixing portion  2544  may have a groove shape. 
     The first position fixing portion  2517  may be inserted into the first-lever elastic member  2541 , and the first position fixing portion  2517  may allow the first-lever elastic member  2541  to move in the left-right direction. Thus, a movement of the first-lever elastic member  2541  in the front-rear direction or in the up-down direction may be suppressed. 
     The second position fixing portion  2544  may have a groove shape, and the first-lever elastic member  2541  may be inserted into the second position fixing portion  2544 . The second position fixing portion  2544  may allow the first-lever elastic member  2541  to move in the left-right direction. Thus, a movement of the first-lever elastic member  2541  in the front-rear direction or in the up-down direction may be suppressed. 
     In the present embodiment, the second position fixing portion  2544  may be disposed between the first journal  2010  and the first guide  2545 . The second position fixing portion  2544  may include a first position fixing part  2544   a  and a second position fixing part  2544   b . The first position fixing part  2544   a  may have a concave shape at a portion of a lower side of the first journal  2010 , and the second position fixing part  2544   b  may have a concave shape at a portion of an upper side of the first guide  2545 . 
     When viewed from a later side, each of the first position fixing part  2544   a  and the second position fixing part  2544   b  may have a curved surface, and a curvature center of each of the first position fixing part  2544   a  and the second position fixing part  2544   b  may be positioned at an inside of the first-lever elastic member  2541 . 
     A radius of curvature of each of the first position fixing part  2544   a  and the second position fixing part  2544   b  may be larger than a diameter of the first-lever elastic member  2541 . 
     When the first lever  2510  is moved toward the housing assembly  2001  by operation force of a user, the lever engaging portion  2516  releases the mutually-engaged structure with the base  32 . In this instance, since the first-lever elastic member  2541  elastically supports the first lever  2510 , when the operation force of the user is removed, the first lever  2510  is moved back to the first side cover  2170  and the lever engaging portions  2516  are exposed to an outside of the through holes  2171  and  2172 . 
     The sweep module  2000  may be maintained in a state mounted on the base  32  through the mutually-engaged structure of the lever engaging portion  2516  protruding to an outside of the through holes  2171  and  2172  and the base  32 . 
     When the mutually-engaged structure between the lever engaging portion  2516  and the base  32  is released, the sweep module  2000  can be separated from the base  32 . 
     In the present embodiment, since the first lever  2510  and the second lever  2520  are disposed at the left and right sides of the sweep module  2000 , respectively, the sweep module  2000  can be separated from the body  30  only when both of the mutual engagements of the first lever  2510  and the second lever  2520  are released. 
     The first lever  2510  provides the mutually-engaged structure with the base  32  and releases the mutually-engaged structure with the base  32 . The second lever  2520  provides not only an act of the first lever  2510  but also a connection structure with the driving unit  2300 . 
     The second lever  2520  may include an upper lever body  2522 , a lower lever body  2524 , a lever engaging portion  2526 , and an operation portion  2529 . The upper lever body  2522  may be disposed between the housing assembly  2001  and the second side cover  2180  and be elastically supported by the second-lever elastic member  2542 . The lower lever body  2524  may be disposed between the housing assembly  2001  and the second side cover  2180 , be integral with the upper lever body  2522 , be exposed to an outside of the housing assembly  2001 , and receive operation force of a user. The lever engaging portion  2526  may protrude from the upper lever body  2522  and be disposed to penetrate through holes  2181  and  2182  of the second side cover  2180 . The operation portion  2529  may protrude to a lower side from the lower lever body  2524 . 
     When it is necessary to distinguish the lever engaging portion  2516  of the first lever from the lever engaging portion  2526  of the second lever, the lever engaging portion  2516  of the first lever is referred to as one-side lever engaging portion, and the lever engaging portion  2526  of the second lever is referred to as the other-side lever engaging portion. 
     The lever engaging portion  2526  may protrude from the lower lever body  2522  to an outside (a side opposite to the agitator). The lever engaging portion  2526  may include a first lever engaging portion  2526   a  and a second lever engaging portion  2526   b.    
     The lever engaging portion  2526  may form a mutually-engaged structure with an engaged groove  3266  formed at the storage housing  326  of the base  32 . 
     Since the lever engaging portion  2526  includes the first lever engaging portion  2526   a  and the second lever engaging portion  2526   b , the engaged groove  3266  may include a first engaged groove  3266   a  and a second engaged groove  3266   b  to correspond to them. With respect to the lever engaging portion  2516  of the first lever  2510 , an engaged groove (not shown) having the same structure may be formed. The first engaged groove  3266   a  and the second engaged groove  3266   b  may be formed at a sidewall  3262  of the storage housing  326 . 
     The first engaged groove  3266   a  and the second engaged groove  3266   b  may be positioned at a lower side than a driven coupling  2220  and a driving coupling  2320 . 
     In the present embodiment, a mutually-engaged structure is formed in a direction of gravity through the engaging groove and the lever engaging portions at one side and the other side of the sweep module  2000 , respectively. 
     Unlike in the present embodiment, only the first lever  2510  in which the driven coupler is not disposed may form the mutually-engaged structure downward with the base  32 . The other side of the sweep module  2000  may be supported by the body  30  through the driving coupling  2320  and the driven coupling  2220  described later. 
     In the present embodiment, the sweep module  2000  may be detachably coupled to the body  30  by the engaged groove at one side, the one-side lever engaging portion, the engaged groove at the other side, and the other-side lever engaging portion, the driving coupling  2320 , and the driven coupling  2220 . 
     The second side cover  2180  may include a second side cover body  2183 , a through hole  2181  or  2182 , a hook portion  2184 , a fastening portion  2186 , and an opening surface  2185 . The second side cover body  2183  may be in close contact with the other side (a right side in the present embodiment) of the housing assembly  2001 . The through hole  2181  or  2182  may be disposed to penetrate the second side cover body  2183 . The hook portion  2184  may protrude from the second side cover body  2183  toward the housing assembly  2001  and may be hooked-coupled with the housing assembly  2001 . The fastening portion  2186  may couple the second side cover body  2183  and the housing assembly  2001  by a fastening member (not shown). In order to transmit driving force of the driving unit  2300  to the agitator  2200 , the driving unit  2300  may penetrate the opening surface  2185 . 
     The opening surface  2185  may be disposed in the left-right direction. A first coupler  2310  of the driving unit  2300 , which will be described later, may be inserted through the opening surface  2185 . 
     The sweep module  2000  may include a second guide  2547 , a second guide hole  2528 , a third position fixing portion  2527 , and a fourth position fixing portion  2546 . The second guide  2547  may protrude to the second lever  2520  at the other side (a right side in the present embodiment) of the dust housing  2100  and mutually interfere with the second lever  2520  to guide a movement direction of the second lever  2520 . The second guide hole  2528  may be formed at the second lever  2520 , and the second guide  2547  may be inserted to the second guide hole  2528  so that the movement of the second guide  2547  is guided. The second position fixing portion  2527  may be disposed at the second lever  2520  and may be inserted into the other end of the second-lever elastic member  2542 . The fourth position fixing portion  2546  may be disposed at the dust housing  2100  and one end of the second-lever elastic member  2542  may be inserted into the fourth position fixing portion  2546 . 
     The agitator  2200  may include an agitator assembly  2210 , a driven coupling  2220 , a coupling elastic member  2230 , a coupling stopper  2270 . The agitator assembly  2210  may sweep a foreign material on a floor into the collection space  2102  through rotation. The driven coupling  2220  may receive rotational force from the driving unit  2300  and may be relatively movably disposed between the driving unit  2300  and the agitator assembly  2210 . The coupling elastic member  2230  may be disposed between the agitator assembly  2210  and the driven coupling  2220 , provide elastic force to the driven coupling  2220 , and press the driven coupling  2220  toward the driving unit  2300 . The coupling stopper  2270  may penetrate the driven coupling  2220  and be coupled to the agitator assembly  2210 , and form a mutually-engaged structure with the driven coupling  2220  in a left-right direction to prevent the driven coupling  2220  from being separated. 
     The agitator assembly  2210  may include an agitator body  2240 , a shaft member  2201 , a collection member  2250 , and a bearing  2600 . The agitator body  2240  may be disposed at the collection space  2102 , and be rotated by receiving the rotational force of the driving unit  2300 . The shaft members  2201  may be disposed at one side and the other side of the agitator body  2240 , respectively, provide a rotation center of the agitator body  2240 , and be rotatably supported by the dust housing  2100 . The collection member  2250  may be installed on an outer circumferential surface of the agitator body  2240  and sweep a foreign material into the collection space  2102 . The bearing  2600  may provide rolling friction to the shaft member  2201 . 
     In the present embodiment, the driven coupling  2220  may be assembled detachably with a lever (the second lever  2520  in the present embodiment) and the shaft member  2201  and may move together with the lever. In the present embodiment, the coupling of the driven coupling  2220  with the driving unit  2300  may be released by operation force of a user applied to the second lever  2520 . 
     The driven coupling  2220  may move toward the shaft member  2201 , and the coupling with the driving unit  2300  may be released. The driven coupling  2220  may relatively move in a horizontal direction between the agitator assembly  2210  and the driving unit  2300 . 
     The agitator body  2240  may be disposed in the left-right direction. The agitator body  2240  may be disposed at an inside of the collection space  2102 . 
     The collection member  2250  may be formed along an outer circumferential surface of the agitator body  2240 . The collection member  2250  may protrude radially outward from the outer circumferential surface of the agitator body  2240 . The collection member  2250  may rotate together with the agitator body  2240  when the agitator body  2240  rotates. The collection member  2250  may penetrate the collection opening surface  2101  and be in contact with the floor. The collection member  2250  may be composed of a plurality of brushes. 
     When the agitator assembly  2210  rotates, the collection member  2250  may be contact with the foreign material on the floor and move the foreign material into the collection space  2102 . 
       FIG.  18    is a partially exploded perspective view of the sweep module showing a coupled structure of the agitator shown in  FIG.  5   .  FIG.  19    is an exploded perspective view showing an assembled structure of the driven coupling shown in  FIG.  18   .  FIG.  20    is a perspective view viewed from a left side of  FIG.  18   .  FIG.  21    is a right cross-sectional view showing the agitator of  FIG.  18   . FIG. is an exploded perspective view of the driving unit viewed from a left side of  FIG.  18   . 
     Referring to  FIG.  16    to  FIG.  18   , the shaft members  2201  may be disposed at one side and the other side of the agitator body  2240 , respectively. The shaft member  2201  may form a center of rotation of the agitator assembly  2210 . 
     The shaft member  2201  may be disposed in the left-right direction. The shaft member  2201  may penetrate left and right sides of the collection space  2102 . 
     In the present embodiment, the shaft member  2201  may penetrates the left wall  2011  and the right wall  2012  of the dust housing  2100 . The shaft member  2201  may be integral with the agitator body  2240 . 
     In the present embodiment, the shaft member  2201  may be separably or detachably assembled with the agitator body  2240 . The shaft member  2201  and the agitator body  2240  may form a mutually-engaged structure in a rotation direction of the agitator  2200 , but may be separated in a rotation-axis direction (a left-right direction in the present embodiment) of the agitator  2200 . 
     The agitator assembly  2210  and the shaft member  2201  may be detachably assembled, Therefore, only the agitator assembly  2210  can be replaced. That is, the agitator assembly  2210  may be separated from the dust housing  2100  in a state that each shaft member  2201  is assembled to the dust housing  2100 . 
     Since the agitator  2200  is a consumable element, the agitator  2200  may be periodically replaced. Through a coupling structure of the shaft member  2201  and the agitator body  2240 , only the agitator body  2240  may be separated from the dust housing  2100  without an entire separation of the agitator  2200 . The shaft member  2201  and the agitator body  2240  maintain a state of a mutually-engaged structure. 
     The shaft member  2201  may include a rotating shaft body  2202 , a shaft portion  2203 , and a coupling guide  2204 . The rotating shaft body  2202  may be mutually coupled to the agitator body  2240 . The shaft portion  2203  may protrudes from the rotating shaft body  2202  toward the driving unit  2300 , provide a rotation center of the agitator  2200 , and be coupled with the bearing  2260 . The coupling guide  2204  may protrude from the shaft portion  2203  toward the driving portion  2300  more and penetrate the driven coupling  2220 . The coupling stopper  2270  may be coupled to the coupling guide  2204 . 
     The rotating shaft body  2202  may have a disk shape. The shaft portion  2203  may protrude from the rotating shaft body  2202  toward the driving portion  2300 . 
     A diameter or a size of the shaft portion  2203  may be smaller than a diameter of the rotating shaft body  2202 . 
     The shaft portion  2203  may have a cylindrical shape. An outer surface of the shaft portion  2203  may be inserted into the bearing  2260 . The shaft portion  2203  may be inserted into and supported by the bearing  2260 . 
     The coupling guide  2204  may further protrude from the shaft portion  2203  toward the driving portion  2300  more. Curvature centers of the coupling guide  2204  and the shaft portion  2203  may be located on the same rotation center. 
     A diameter of the coupling guide  2204  may be smaller than a diameter of the shaft portion  2203 , and a first step  2205  may be formed between the coupling guide  2204  and the shaft portion  2203  due to a diameter difference. 
     One end of the coupling elastic member  2230  may be supported by the first step  2205 . 
     The coupling guide  2204  may further include a through portion  2206  penetrating the driven coupling  2220 . A coupling stopper  2270  may be fixed to the through portion  2206 . 
     The driven coupling  2220  may move in the left-right direction along the coupling guide  2204 . Since the driven coupling  2220  is elastically supported by the coupling elastic member  2230 , the driven coupling  2220  may be kept in close contact with the driving unit  2300  when external force is not applied. 
     In the present embodiment, the coupling guide  2204  may have a circular columnar shape, and the through portion  2206  may have a polygonal column shape (a hexagonal column shape in the present embodiment). 
     The through portion  2206  may be inserted into the driven coupling  2220  and form a mutually-engaged structure in a rotation direction of the agitator  2200 . 
     On the other hand, the shaft member  2201  is provided with a key groove  2207  for a mutually-engaged structure with the agitator body  2240 . The key groove  2207  may be disposed on an opposite side of the shaft portion  2203  based on or with respect to the rotating shaft body  2202 . The key groove  2207  may be disposed at a side facing the agitator body  2240 . The key groove  2207  may have a shape of an atypical polygon. The key groove  2207  may be open in a radial direction of the rotation axis. 
     A key  2247 , which is inserted into the key groove  2207 , may be formed at the agitator body  2240 . The key  2247  may protrude toward the shaft member  2201  or the driven coupling  2220 . 
     The driven coupling  2220  may include a coupling body  2222 , a first guide groove  2224 , a second guide groove  2226 , a second step  2225 , and a power transmission groove  2228 . The coupling body  2222  may be coupled with a lever (the second lever  2520  in the present embodiment). The first guide groove  2224  may be formed at one side (a left side in the present embodiment) of the coupling body  2222  to have a concave shape, The coupling guide  2204  may be inserted and the coupling elastic member  2230  may be inserted into the first guide groove  2224 . The second guide groove  2226  may communicate with the first guide groove  2224 , and penetrate the coupling body  2222 . The through portion  2206  may be inserted to the second guide groove  2226 . The second step  2225  may be disposed between the first guide groove  2224  and the second guide groove  2226 , and the first step  2205  may be supported by the second step  2225 . The power transmission groove  2228  may be formed at the other side (the right side in the present embodiment) of the coupling body  2222  to have a concave shape. The driving coupling  2320  coupled to the driving unit  2300  may be detachably inserted into the power transmission groove  2228 . 
     A diameter of the first guide groove  2224  may be larger than a diameter of the coupling elastic member  2230 . A diameter of the coupling elastic member  2230  may be larger than a diameter of the coupling guide  2204  and smaller than a diameter of the first guide groove  2224 . 
     The first guide groove  2224  may have a circular hollow shape. 
     The second guide groove  2226  may have a shape corresponding to a shape of the through portion  2206 . In the present embodiment, the second guide groove  2226  has a hollow shape which side surface has a hexagonal shape. 
     The coupling body  2222  may be provided with a groove  2223 , which has a concave shape to an inside in a radial direction at an outer side surface. A diameter of the groove  2223  may be smaller than an outer surface diameter of the coupling body  2222 . 
     A coupling groove  2523  may be formed at the upper lever body  2522  of the second lever  2520 . The coupling groove  2523  may be inserted into the groove  2223  and thus may be engaged with the driven coupling  2220 . 
     The groove  2223  may be perpendicular to a rotation center of the agitator  2200 . 
     The second lever  2520  may be coupled to or separated from the driven coupling  2220  in the up-down direction and form a mutually-engaged structure with the driven coupling  2220  in the left-right direction. 
     The second lever  2520  may further include a first extension portion  2522   a  and a second extension portion  2522   b  extending from an upper side of the upper lever body  2522 . The coupling groove  2523  may be formed between the first extension portion  2522   a  and the second extension portions  2522   b.    
     The first extension portion  2522   a  and the second extension portion  2522   b  are structures for more robust assembly with the driven coupling  2220 . The first extension portion  2522   a  and the second extension portion  2522   b  may be contact with one side surface  2223   a  and the other side surface  2223   b  of the groove  2223 . 
     The coupling stopper  2270  may penetrate the driven coupling  2220  and may be fastened to the through portion  2206 . The driven coupling  2220  may move in the left-right direction between the coupling stopper  2270  and the shaft member  2201 . 
     A head  2702  of the coupling stopper  2270  may interfere with the power transmission groove  2228  of the driven coupling  2220  and prevent the driven coupling  2220  from being separated to a right side. A coupling portion  2274  of the coupling stopper  2270  may be inserted into and fastened to a fastening groove  2207  of the through portion  2206 . 
     The driving coupling  2320  may be inserted into the power transmission groove  2228  and may be coupled to the power transmission groove  2228  to transmit rotational force. The power transmission groove  2228  may have any of various shapes or forms. In the present embodiment, the power transmission groove  2228  may have a hexagonal groove when viewed from a lateral side. 
     A diameter of the power transmission groove  2228  may be larger than a diameter of the second guide groove  2226 . The power transmission groove  2228  and the second guide groove  2226  may communicate with each other. The first guide groove  2224  may be disposed at one side of the second guide groove  2226  to be communicated with the second guide groove  2226  and the power transmission groove  2228  may be disposed at the other side of the second guide groove  2226  to be communicated with the second guide groove  2226 . 
     The power transmission groove  2228  may be open toward the other side, and the first guide groove  2224  may be open toward one side. 
     When the driven coupling  2220  is coupled to the upper lever body  2522 , the power transmission groove  2228  may be positioned at the other side of the upper lever body  2522  and the first guide groove  2224  may be positioned at one side of the upper lever body  2522 . 
     The second lever  2520  may form a mutually-engaged structure with the driven coupling  2220  with respect to a direction perpendicular to the shaft member  2201 . In addition, the lever engaging portion  2526  of the second lever  2520  may form a mutually-engaged structure with the base  32 . 
     When the driving coupling  2320  and the driven coupling  2220  are mutually coupled, the driven coupler  2220  may protrude to an outside of the dust housing  2100 . Specifically, the driven coupling  2220  may penetrate the opening surface  2185  of the second side cover  2180  and may protrude to an outside than the second side cover  218 . 
     By the operation of the second lever  2520 , the driven coupling  2220  may be moved to the same position with the opening surface  2185  or to an inside than the opening surface  2185 . When the driven coupling  2220  is moved to the same portion with the opening surface  2185  or to the inside than the opening surface  2185 , the driven coupling  2220  can be prevented from being interfered with the base  32  and the dust housing  2100  can be easily separated. 
     Therefore, a moving distance of the second lever  2520  may be greater than a thickness of the driven coupler  2220  and the driving coupling  2320  in a coupled state. 
     When the second lever  2520  is pressed toward the agitator  2200 , the second lever  2520  moves toward the agitator  2200 . Thus, the mutually-engaged structure of the lever engaging portion  2526  and the base  32  is released and the dust housing  2100  is in a state being able to be separated from the base  32 . 
     In addition, when the second lever  2520  is pressed toward the agitator  2200 , the coupling elastic member  2230  may be compressed and the driven coupling  2220  may move toward the agitator  2200 . 
     When the driven coupling  2220  moves toward the agitator  2200  by the second lever  2520 , the driven coupling  2220  and the driving unit  2300  are physically separated and the dust housing  2100  is in a state being able to be separated from the base  32 . 
     Since the sweep module  2000  according to the present embodiment has a structure in which the agitator  2200  is installed on the inside of the sweep module  2000 , the dust housing  2100  should be physically separated from the driving unit  2300  when the dust housing  2100  is separated from the base  32 . 
     The movement of the second lever  2520  not only releases the coupling of the dust housing  2100  and the base  32  but also releases the coupling of the driven coupling  2220  and the driving unit  2300  at the same time. 
     In this instance, since the second lever  2520  is hidden or shield inside the dust housing  2100  and only the operation unit  2529  is exposed to the outside, a coupling structure of the driven coupling  2220  is not exposed to the outside. In particular, since the second side cover  2180  shields or blocks most of the second lever  2520 , damage to the second lever  2520  due to external impact can be minimized. 
     Even if the second lever  2520  is repeatedly used, the second lever  2520  moves only at an inside of the dust housing  2100  and thus separation or damage of the second lever  2520  can be minimized. 
     In addition, since the side covers  2170  and  2180  shield or cover the levers  2510  and  2520  inside the dust housing  2100 , an intrusion of an external foreign material or the like to portions where the levers  2510  and  2520  can be minimized. Accordingly, reliability according to the operation can be ensured. 
     Then, when the operation force applied to the second lever  2520  is removed, the driven coupling  2220  moves toward the other side by elastic force of the coupling elastic member  2230 . 
     In this instance, since the shaft member  2201  penetrates through the driven coupling  2220  and the coupling stopper  2270  is coupled to the shaft member  2201 , the driven coupling  2220  can be prevented from being separated from the shaft member  2201 . That is, the driven coupling  2220  may move along an axis direction of the shaft member  2201 , but may be prevented from being separated from the shaft member  2201  by the coupling stopper  2270 . 
     The driving unit  2300  may include a drive housing  2310 , a sweep motor  2330 , a power transmission assembly  2340 , and a driving coupling  2320 . The drive housing  2310  may be assembled with the body  30 . The sweep motor  2330  may be assembled with a drive housing  2310 . The power transmission assembly  2340  may be disposed at an inside of the drive housing  2310  and be assembled with the sweep motor  2330  to receive rotational force. The driving coupling  2320  may be coupled to the power transmission assembly  2340  and be selectively engaged with the driven coupling  2220 . 
     Since the agitator  2200  is disposed inside the sweep module  2000  and the sweep motor  2330  is disposed inside the body  30 , the driving coupling  2320  and the driven coupling  2220  transmitting the rotational force to the agitator  2200  may have selectively-detachable structure. If the driving coupling  2320  and the driven coupling  2220  are not detachable, the dust housing  2100  cannot be separated from the body  30 . 
     The drive housing  2310  may be fixed to the body  30 . The drive housing  2310  is fixed to the base  32  in the present embodiment. The drive housing  2310  is a structure for installing the power transmission assembly  2340  and the sweep motor  2330 . 
     The drive housing  2310  may have any of various shapes of forms. In the present embodiment, the drive housing  2310  shields or covers the power transmission assembly  2340  therein, and exposes only the sweep motor  2330  and the driving coupling  2320  to the outside. 
     The drive housing  2310  may include a first drive housing  2312  and a second drive housing  2314 , a coupling-installed portion  2315 , and a hole  2316 . The first drive housing  2312  and the second drive housing  2314  may form an outer shape. The coupling-installed portion  2315  may be disposed at one of the first drive housing  2312  and the second drive housing  2314 , and the driving coupling  2320  may be disposed at the coupling-installed portion  2315 . The hole  2316  may be disposed at one of the first drive housing  2312  and the second drive housing  2314 , and a motor shaft of the sweep motor  2330  may penetrate the hole  2316 . 
     The power transmission assembly  2340  may be disposed between the first drive housing  2312  and the second drive housing  2314 . 
     In the present embodiment, the first drive housing  2312  is disposed at one side (toward the agitator  2200 ), and the second drive housing  2314  is disposed at the other side (at an outside). 
     In the present embodiment, the coupling-installed portion  2315  is disposed at the first drive housing  2312 . The driving coupling  2320  is disposed at the coupling-installed portion  2315  and is connected to the power transmission assembly  2340 . The driving coupling  2320  may rotate in a state that the driving coupling is installed on the coupling installation unit  2315 . 
     The driving coupling  2320  has a shape corresponding to a shape of the power transmission groove  2228  of the driven coupling  2220 . In the present embodiment, the driving coupling  2320  has a hexagonal shape when viewed from a lateral side. The driving coupling  2320  may be selectively engaged with the driven coupling  2220  through the opening surface  2185  of the second side cover  2180 . 
     The driving coupling  2320  may protrude toward the second side cover  2180  than one side (a left side) of the first drive housing  2312  in a state that the driving coupling  2320  is assembled to the drive housing  2310 . 
     A rotation center of the driving coupling  2320  is disposed at the left-right direction and may match the rotation center of the agitator  2200 . 
     In the present embodiment, the first drive housing  2312  may have a space formed therein, and the power transmission assembly  2340  may be rotatably installed in the space. The second drive housing  2314  may have a shape or a form of a cover covering the first drive housing  2312 . 
     The drive housing  2310  may further include a first fastening portion  2317  and a second fastening portion  2318 . The first fastening portion  2317  and the second fastening portion  2318  may be disposed at the first drive housing  2312 . The first fastening portion  2317  and the second fastening portion  2318  may be formed so that a fastening member is installed on the first fastening portion  2317  or the second fastening portion  2318  in an up-down direction. 
     A motor axis of the sweep motor  2330  may be disposed in the left-right direction. The sweep motor  2330  may be disposed at one side or the other side of the drive housing  2310 . 
     The sweep motor  2330  may be disposed toward an inside of the body  30  based on or with respect to the drive housing  2310 . A volume of the body  30  may be minimized by arranging the sweep motor  2330  at a side of the agitator  2200 . 
     In the present embodiment, a motor axis direction Mx of the sweep motor  2330  and a rotation axis Ax of the agitator  2200  may be parallel. In the present embodiment, a rotation center of the agitator  2200 , a rotation center of the shaft member  2201 , a center of the driven coupling  2220 , and a center of the driving coupling  2320  are located on a line of the rotation axis Ax of the agitator  2200 . 
     In the present embodiment, the sweep motor  2330  is positioned at an upper side than the dust housing  2100 . The sweep motor  2330  is positioned at a rear side than the dust housing  2100 . The sweep motor  2330  is positioned at an upper side than the installation space  325  and the storage housing  326  of the base  32 . 
     The power transmission assembly  2340  may include a plurality of gears. A number and a shape of gears included in the power transmission assembly  2340  may be various depending on a number of revolutions and transmitted torque. 
       FIG.  23    is an exploded perspective view of the dust housing shown in  FIG.  5   .  FIG.  24    is an enlarged view of a dustpan shown in  FIG.  23   .  FIG.  25    is an exploded perspective view of the dust housing shown in  FIG.  5    when viewed from an upper left side.  FIG.  26    is an exploded perspective view of the dust housing shown in  FIG.  5    when viewed from a lower left side.  FIG.  27    is an exploded perspective view of the dust housing shown in  FIG.  5    when viewed from a rear side.  FIG.  28    is an exploded perspective view of the dust housing shown in  FIG.  5    when viewed from a lower front side.  FIG.  29    is a cross-sectional view showing a dustpan stopper shown in  FIG.  7   .  FIG.  30    is an exemplary operation view of the dustpan according to the first embodiment of the present disclosure. 
     A dustpan will be described in more detail with reference to  FIG.  7   ,  FIG.  18   , and  FIG.  23    to  FIG.  28   . 
     The sweep module  2000  may further a dustpan  2800 . The dustpan  2800  may be disposed at an inside of the collection space  2102  and may be disposed between the dust housing  2100  and the agitator  2200 . A lower end of the dustpan  2800  may protrude to a floor through the collection opening surface  2101 . 
     The sweep module  2000  may further include a pan elastic member  2850  that is assembled to the dust housing  2100  and the dustpan  2800  and provides elastic force to the dustpan  2800 . 
     By the elastic force of the pan elastic member  2850 , a lower end of the dustpan  2800  may penetrate through the collection opening surface  2101  and maintain a protruding state at a lower side. 
     In the present embodiment, the pan elastic member  2850  is disposed to press the lower end of the dustpan to the floor. Unlike the present embodiment, the lower end of the dustpan may be in contact with the floor only by a weight or a self-load of the dustpan. 
     The dustpan  2800  may be installed to be rotatable relative to the agitator  2200 . The dustpan  2800  may be rotatably installed with the dust housing  2100 . The dustpan  2800  may surround the agitator  2200 . 
     The dustpan  2800  may include a guide pan housing  2830 , a first side pan housing  2810 , and a second side pan housing  2820 . The guide pan housing  2830  may surround a part of an outer surface of the agitator  2200 . The first side pan housing  2810  may be disposed at one side (a left side in the present embodiment) of the guide pan housing  2830  and cover one side of the agitator  2200 . The second side pan housing  2820  may be disposed at the other side (a right side in the present embodiment) of the guide pan housing  2830  and cover the other side of the agitator  2200 . 
     The guide pan housing  2830  may be disposed to surround a part of an outer circumferential surface of the agitator  2200  having a cylindrical shape. A portion of the agitator  2200  surrounded by the guide pan housing  2830  may be associated with a rotational direction of the agitator  2200 . 
     In the present embodiment, the agitator  2200  is rotated from a front side to a rear side based on or with respect to a driving direction or a traveling direction of the cleaner. When viewed from a right surface based on the driving direction or the traveling direction of the cleaner, the agitator  2200  may rotate in a clockwise direction. 
     Since the agitator  2200  rotates from the front side to the rear side, it assists in driving or moving the cleaner. Since the agitator  2200  rotates from the front side to the rear side, a foreign material on a floor may be moved to a rear side by the agitator  2200 . 
     The dustpan  2800  sweeps up the foreign material moved to the rear side of the agitator  2200 . 
     Thus, the guide pan housing  2830  may be formed to surround a back surface of the agitator  2200 . The guide pan housing  2830  may be in close contact with an outer surface of the agitator  2200 . Since the guide pan housing  2830  is in close contact with an outer circumferential surface of the agitator  2200 , a foreign material may be confined between the agitator  2200  and the guide pan housing  2830 . The foreign material confined between the agitator  2200  and the guide pan housing  2830  may be rotated together with the agitator  2200  and moved to the storage space  2104 . 
     The guide pan housing  2830  may be preferably formed to surround the agitator  2200  from a bottom to an upper portion in order to easily transfer the foreign material. 
     The guide pan housing  2830  may have a curved surface, and a curvature center of the guide pan housing  2830  may be disposed at an inside of the agitator  2200 . 
     The curvature center of the guide pan housing  2830  may be disposed at the rotation axis Ax of the agitator  2200 . A radius of curvature of an inner surface of the guide pan housing  2830  may be the same as a radius of curvature of an outer surface of the agitator  2200 . 
     The guide pan housing  2830  may include a curved portion  2832 , a flat portion  2834 , and a dust guard  2836 . The curved portion  2832  may be formed to surround a rear side of the outer circumferential surface of the agitator  2200 . The flat portion  2832  may extend from an upper end of the curved portion  2832  and formed of a flat surface. The dust guard  2836  may be coupled to a lower end of the curved portion  2832  and be in contact with a floor. 
     The dust guard  2836  may be coupled to the lower end of the curved portion  2832 . The dust guard  2836  may be preferably formed of a material having elasticity. By the elasticity of the dust guard  2836 , a contact property with a floor can be enhanced, thereby preventing the foreign material from escaping between the dust guard  2836  and the floor. 
     During operation of the cleaner, the dust guard  2836  may protrude to a lower side than the collection opening surface  2101 . The dust guard  2836  may protrude to a lower side than a lower surface of the lower housing  2140 . 
     A lower end of the dust guard  2836  may be positioned at a lower side than the collection opening surface  2101 . When the dust guard  2836  and an obstacle of or on a floor collide or interfere with each other, the dust guard  2836  may be accommodated into the collection space  2102 . 
     The dust guard  2836  may collide with a hard structure on or of the floor while the cleaner drives or travels. The dust guard  2836  formed of an elastic material may cushion or relieve an impact during the collision. 
     When the guide pan housing collides with the structure on or of the floor, the guide pan housing  2830  may cushion or relieve an impact through rotation. This structure will be described later. 
     A length of the guide pan housing  2830  in the left-right direction may be longer than the agitator  2200 . The first side pan housing  2810  and the second side pan housing  2820  may cover a left side and a right side of the agitator  2200 , respectively. 
     Since the first side pan housing  2810  and the second side pan housing  2820  have the same structure and bisymmetrical or laterally symmetrical to each other, the second side pan housing  2820  will be described as an example. 
     A first through hole (not shown) through which the agitator  2200  penetrates may be formed at the first side pan housing  2810 . A second through hole  2821  through which the agitator  2200  penetrates may be formed at the second side pan housing  2820 . 
     In the present embodiment, the agitator body  2240  and the shaft member  2201  may installed to penetrate through the through hole  2821 . 
     The side pan housings  2810  and  2820  may be rotated around or with respect to the rotation axis Ax of the shaft member  2201 . The side pan housings  2810  and  2820  may be supported by a component or an element (e.g., the agitator body, the shaft member, or so on) of the agitator  2200  to be rotated in the front-rear direction. 
     However, since the agitator  2200  is configured to rotate, when the side pan housings  2810  and  2820  are supported by the agitator  2200 , the side pan housings  2810  and  2820  may also rotate. Therefore, in the present embodiment, the side pan housings  2810  and  2820  are assembled with the dust housing  2100  and rotated in the front-rear direction in a state assembled with the dust housing  2100 . 
     The side pan housings  2810  and  2820  are rotatably assembled with the left wall  2011  and the right wall  2012  of the dust housing  2100 , respectively. 
     The left wall  2011  may include an upper left wall  2011   a  disposed at the upper housing  2110  and a lower left wall  2011   b  formed at the lower housing  21040 . The right wall  2012  may include an upper right side wall  2012   a  disposed at the upper housing  2110  and a lower right side wall  2012   b  formed at the lower housing  2140 . 
     The first journal  2010  may be disposed between the upper left wall  2011   a  and the lower left wall  2011   b , and the second journal  2020  may be disposed between the upper right wall  2012   a  and the lower right wall  2012   b.    
     A first journal groove  2015  by which the first journal  2010  is supported may be formed between the upper left wall  2011   a  and the lower left wall  2011   b . The first through hole may be positioned at an inside with respect to the first journal  2010 . The first through hole may be disposed at an inside of the first journal groove  2015  and communicate with the first journal groove  2015 . 
     A second journal groove  2016  by which the second journal  2020  is supported may be formed between the upper right wall  2012   a  and the lower right wall  2012   b . The second through hole  2821  may be positioned at an inside with respect to the second journal  2020 . The second through hole may be disposed at an inside of the second journal groove  2016  and communicate with the second journal groove  2016 . 
     A plurality of pan guides  2860  inserted into an inside of the first through hole and guiding rotation of the first side pan housing  2810  may be disposed at an inner side surface of the upper left wall  2011   a  and the lower left wall  2011   b.    
     Similarly, a plurality of pan guides  2860  inserted into an inside of the second through hole and guiding rotation of the second side pan housing  2820  may be disposed at an inner side surface of the upper right wall  2012   a  and the lower right wall  2012   b.    
     The pan guides  2860  at the left wall may protrude toward the right wall, and the pan guides  2860  at the right wall may protrude toward the left wall. 
     The plurality of pan guides  2860  may be disposed within the same radius with respect to the rotation axis Ax and have the same radius of curvature. The pan guides  2860  may be inserted into the through hole  2821  from outsides of the side pan housings  2810  and  2820 . 
     The pan guide  2860  disposed at the left side may support the first side pan housing  2810 , and the pan guide  2860  disposed at the right side may support the second side pan housing  2820 . 
     The guide pan housing  2830  may rotate around or with respect to a rotation axis Ax in a state supported by the pan guide  2860 . 
     One end of the pan elastic member  2850  may be fixed to the dustpan  2800  and the other end of the pan elastic member  2860  may be fixed to the dust housing  2100 . The pan elastic member  2850  may return the dustpan  2800  to an initial position through elastic force. 
     The pan elastic member  2850  may be disposed at any of various positions. In the present embodiment, the pan elastic member  2850  may be coupled to a side pan housing and a dust housing  2100  (a lower housing in the present embodiment). 
     The pan elastic members  2850  may be disposed at the left side and the right side of the dustpan  2800 , respectively, and provide elastic force in the same direction at both sides of the dustpan  2800 . The pan elastic member  2850  may include a first pan elastic member and a second pan elastic member. 
     A first pan fixing portion  2842  to which one end of the pan elastic member  2850  is fixed may be disposed at the second side pan housing  2820 , and a second pan fixing portion  2844  to which the other end of the pan elastic member  2850  is fixed may be disposed at the lower housing  2140  (specifically, a right wall). 
     The first pan fixing portion  2842  may be disposed at an upper side than or higher than the second pan fixing portion  2844 . The first pan fixing portion  2842  may be disposed at a rear side than the second pan fixing portion  2844 . 
     The pan elastic member  2850  may provide elastic force so that a lower end of the dustpan  2800  is rotated to a lower side. 
     In the present embodiment, since the dustpan  2800  is disposed at a rear side of the agitator  2200 , the first pan fixing portion  2842  and the second pan fixing portion  2844  may be disposed at a rear side than the rotation axis Ax. 
     When the agitator  2200  rotates, force to move the body  30  to a front direction may be provided through friction force by the agitator  2200  and the floor. 
     The foreign material on the floor is swept and moved to the rear side by the rotation of the agitator  2200 , and the dustpan  2800  sweeps up the moved foreign material. 
     Referring to  FIG.  30   , when the dustpan  2800  collides with a structure or an obstacle on or of the floor while the cleaner drives, the dustpan  2800  may be rotated around or with respect to the rotation axis Ax. 
     In the collision, the dust guard  2836  of the dustpan  2800  is rotated about or with respect to the rotation axis Ax and may be accommodated into the collection space  2102 . 
     That is, when the dust guard  2836  and an obstacle collide with each other, the dust guard  2836  is rotated to an upper side to reduce an impact and may be accommodated into the collection space  2102 , thereby avoiding interference with the obstacle. 
     In the collision, the first pan fixing portion  2842  is rotated from a rear side to a front side to expand the pan elastic member  2850 . When the interference due to the obstacle is removed, the dustpan  2800  is rotated to an original position by the elastic force of the pan elastic member  2850 . 
     When the dustpan  2800  collides with an obstacle, the dustpan  2800  may be rotated by mutual interference with the obstacle. Thus, a front side of the body  30  can be prevented from being lifted away from the floor and a height of the body  30  can be kept constant. 
     The dustpan  2800  rotates independently with the agitator  2200 . In this instance, the phrase that the dustpan  2800  rotates may mean that the dustpan  2800  moves as a circular movement at a part of a circular orbit surrounding the agitator  2200 . 
     The dustpan  2800  may be disposed at an area of 40% to 70% of an arbitrary circle surrounding the outer circumference of the agitator  2200 . Specifically, most of the area of 40% to 70% of the arbitrary circle where the dustpan  2800  is disposed may be disposed at a rear side than the rotation axis of the agitator  2200 . Therefore, the foreign material moved by the agitator  2200  may be guided to the storage space positioned at a front side than the agitator  2200 . 
     The dustpan  2800  may move within an arc having a center angle of 180 degrees to 220 degrees at an arbitrary circular orbit (an orbit of an arbitrary circle) CK surrounding the outer circumference of the agitator  2200  and may have a smaller length than the arc. Most of the arc may be disposed at a rear side than the rotation axis of the agitator  2200 . Specifically, the dustpan  2800  may form an arc having a central angle of 170 degrees to 200 degrees at the arbitrary circular orbit surrounding the outer circumference of the agitator  2200 . 
     Meanwhile, referring to  FIG.  29   , in order to prevent the dustpan  2800  from being excessively rotated to the floor, a dustpan stopper  2870  may be formed at least one of the dustpan  2800  and the dust housing  2100 . 
     The dustpan stopper  2870  is disposed within a rotation radius of the dustpan  2800 . In the present embodiment, the dustpan stopper  2870  is disposed within rotation radii of the side pan housings  2810  and  2820 . 
     Specifically, the dustpan stopper  2870  may be disposed at the lower housing  2140 , and lower ends  2812  and  2822  of the side pan housing  2820  may be mutually interfered with the dustpan stopper  2870 . 
     The dustpan stopper  2870  may be disposed at a lower side than the lower end  2822  of the side pan housing  2820  and may support the lower end  2822 . 
     Since the lower end  2822  is supported by the dustpan stopper  2870 , excessive rotation of the dustpan  2800  can be prevented even when the elastic force of the pan elastic member  2850  is provided. 
     In the present embodiment, the dustpan stopper  2870  is disposed at the collection opening surface  2101 . 
     The dustpan stopper  2870  may be disposed at a side portion of the guide pan housing  2830 . 
     On the other hand, when the dustpan  2800  is rotated due to interference with an obstacle, an upper end  2835  of the flat portion  2834  may be in contact with an upper end  2147   a  of the partition  2145 . 
     When the upper end  2835  of the flat portion  2834  and the upper end  2147   a  of the partition  2145  are in contact with each other, the rotation of the dustpan  2800  is restricted. 
     In particular, in order to prevent a collision when the flat portion  2834  and the partition  2145  are in contact with each other, a lower surface of the upper end  2835  may be formed as an inclined surface  2835   b  and the inclined surface  2835   b  may be in contact with and supported by an inclined surface  2147   b  of the partition  2145 . 
     In this instance, the inclined surface  2835   b  of the upper end  2835  may be positioned at an upper side than the inclined surface  2147   b  of the partition  2145 . 
     That is, when the dustpan  2800  is rotated, the flat portion  2834  is supported by the partition  2145  and the rotation of the dustpan  2800  is restricted, thereby preventing damage to the pan elastic member  2850 . 
     In addition, since the flat portion  2834  is supported by the partition  2145 , the dustpan  2800  can be prevented from being excessively rotated and the dustpan  2800  can be prevented from not returning to an initial position due to the excessive rotation. 
     When bottoms of the pair of spin mops  41   a  and  41   b  provided to be symmetrical to each other with respect to the central longitudinal line Po are parallel to a horizontal plane, a robot cleaner may not stably drive and a driving control may be difficult. Therefore, according to the present disclosure, each spin mop  41  is inclined downward toward an outside front side. Hereinafter, an inclination and a motion of a spin mop  41  will be described. 
     The central longitudinal line Po means a line parallel to a front-rear direction and passing through a geometric center Tc of a body. The central longitudinal line Po may be defined as a line passing through the geometric center Tc of the body while being perpendicular to an imaginary line connecting a central axis of the left spin mop and a central axis of the right spin mop. 
     Referring to  FIG.  31   , a point where the spin rotation axis Osa of the left spin mop  41   a  and a lower surface of the left spin mop  41   a  cross is shown, and a point where the spin rotation axis Osb of the right spin mop  41   b  and a lower surface of the right spin mop  41   b  intersect is shown. When viewed from a lower side, among rotational directions of the left spin mop  41   a , a clockwise direction is defined as a first normal direction w 1   f  and a counterclockwise direction is defined as a first reverse direction w 1   r . When viewed from a lower side, among rotational directions of the right spin mop  41   b , a clockwise direction is defined as a second normal direction w 2   f  and a counterclockwise direction is defined as a second reverse direction w 2   r . In addition, when viewed from a lower side, ‘an acute angle between an inclined direction of a lower surface of the left spin mop  41   a  and a left-right direction axis’ and ‘an acute angle between an inclined direction of a lower surface of the right spin mop  41   a  and a left-right direction axis’ are defined as inclination-direction angles Ag 1   a  and Ag 1   b , respectively. The inclination-direction angle Ag 1   a  of the left spin mop  41   a  and the inclination-direction angle Ag 1   b  of the right spin mop  41   b  may be the same. Further, referring to  FIG.  6   , ‘an angle between a lower surface I of the left spin mop  41   a  and an imaginary horizontal surface H’ and ‘an angle between a lower surface I of the right spin mop  41   b  and an imaginary horizontal surface H’ are defined as inclination angles Ag 2   a  and Ag 2   b.    
     A right end of the left spin mop  41   a  and a left end of the right spin mop  41   b  may be in contact with each other or adjacent or close to each other. Therefore, an area where mopping or wiping is not performed between the left spin mop  41   a  and the right spin mop  41   b  can be reduced. 
     When the left spin mop  41   a  rotates, a point Pla that receives the greatest friction force from a floor or a ground at a lower surface of the left spin mop  41   a  may be positioned at a left side of a rotation center Osa of the left spin mop  41   a . Among the lower surface of the left spin mop  41   a , a greater load may be transmitted to the floor or the ground at the point Pla than the other point. Thus, the greatest friction force may be generated at the point Pla. In the present embodiment, the point Pla is disposed at a left front side of the rotation center Osa. In another embodiment, the point Pla may be disposed at an exact left side or at a left rear side based on the rotation center Osa. 
     When the right spin mop  41   b  rotates, a point Plb that receives the greatest friction force from a floor or a ground at a lower surface of the right spin mop  41   b  may be positioned at a right side of a rotation center Osb of the right spin mop  41   b . Among the lower surface of the right spin mop  41   b , a greater load may be transmitted to the floor or the ground at the point Plb than the other point. Thus, the greatest friction force may be generated at the point Plb. In the present embodiment, the point Plb is disposed at a right front side of the rotation center Osb. In another embodiment, the point Pla may be disposed at an exact right side or at a right rear side based on the rotation center Osb. 
     The lower surface of the left spin mop  41   a  and the lower surface of the right spin mop  41   b  may be inclined, respectively. The inclination angle Ag 2   a  of the left spin mop  41   a  and the inclination angle Ag 2   b  of the right spin mop  41   b  may be an acute angle. The inclination angles Ag 2   a  and Ag 2   b  may be small so that points having the greatest friction force are positioned at the points Pla and Plb and entire portions of lower surfaces of the mop portions  411  are in contact with or touch the floor according to rotational motion of the left spin mop  41   a  and the right spin mop  41   b.    
     The lower surface of the left spin mop  41   a  forms a downward slope as a whole in a left direction. The lower surface of the right spin mop  41   b  forms a downward slope as a whole in a right direction. Referring to  FIG.  6   , the lowest point Pla at the lower surface of the left spin mop  41   a  is positioned at a left side portion. The highest point Pha at the lower surface of the left spin mop  41   a  is positioned at a right side portion. The lowest point Plb at the lower surface of the right spin mop  41   b  is positioned at a right side portion. The highest point Phb at the lower surface of the right spin mop  41   b  is positioned at a right side portion. 
     According to the embodiment, an inclination-direction angles Ag 1   a  and Ag 1   b  may be 0 degrees. Further, according to the embodiment, when viewed from a lower side, a lower surface of the left spin mop  41   a  may be inclined to have an inclined-direction angle Ag 1   a  in a clockwise direction with respect to a left-right direction axis, and a lower surface of the right spin mop  41   b  may be inclined to have an inclined-direction angle Ag 1   b  in a counterclockwise direction with respect to the left-right direction axis. In the present embodiment, when viewed from a lower side, a lower surface of the left spin mop  41   a  is inclined to have an inclined-direction angle Ag 1   a  in a counterclockwise direction with respect to the left-right direction axis, and a lower surface of the right spin mop  41   b  is inclined to have an inclined-direction angle Ag 1   b  in a clockwise direction with respect to the left-right direction axis. 
     The movement of the cleaner  1  is achieved by friction force with the floor or the ground generated by the mop module  40 . 
     The mop module  40  may generate ‘a forward-moving friction force’ for moving the body  30  in a front direction, or ‘a rearward-moving friction force’ for moving the body  30  in a rear direction. The mop module  40  may generate ‘a left-moment friction force’ to rotate or turn the body  30  left, or ‘a right-moment friction force’ to rotate or turn the body  30  right. The mop module  40  may generate friction force in which any one of the forward-moving friction force and the rearward-moving friction force is combined with any one of the left moment friction force and the right moment friction force. 
     In order for the mop module  40  to generate the forward-moving friction force, the left spin mop  41   a  may rotate at a predetermined rpm R 1  in the first normal direction w 1   f  and the right spin mop  41   b  may rotate at the predetermined rpm R 1  in the second normal direction w 2   f.    
     In order for the mop module  40  to generate the rearward-moving friction force, the left spin mop  41   a  may rotate at a predetermined rpm R 2  in the first reverse direction w 1   r  and the right spin mop  41   b  may rotate at the predetermined rpm R 2  in the second reverse direction w 2   r.    
     In order for the mop module  40  to generate the right-moment friction force, the left spin mop  41   a  may rotate at a predetermined rpm R 3  in the first normal direction w 1   f , and the right spin mop  41   b  may rotate in the second reverse direction w 2   r , may stop without rotation, or may rotate at a rpm R 4  smaller the rpm R 3  in the second normal direction w 2   f.    
     In order for the mop module  40  to generate the left-moment friction force, the right spin mop  41   b  may rotate at a predetermined rpm R 5  in the second normal direction w 2   f , and the left spin mop  40   b  may rotate in the first reverse direction w 1   r , may stop without rotation, or may rotate at a rpm R 6  smaller the rpm R 5  in the second normal direction w 1   f.    
     Hereinafter, an arrangement of components or elements for improving friction force of the spin mops  41  arranged at a left side and a right side, improving stability in a left-right direction and a front-rear direction, and achieving stable driving regardless of a water level in a water tank  81 . 
     Referring to  FIGS.  31  and  32   , so as to increase the friction force by a spin mop  41  and limit occurrence of eccentricity in one direction when the mobile robot rotates, a mop motor  61  and a battery Bt that are relatively heavy may be disposed on an upper portion of a spin mop  41 . 
     Specifically, a left-mop motor  61   a  may be disposed on a left spin mop  41   a  (at an upper side of the left spin mop  41   a ), and a right-mop motor  61   b  may be disposed on a right spin mop  41   b  (at an upper side of the right spin mop  41   b ). That is, at least a part of the left-mop motor  61   a  may be vertically overlapped with the left spin mop  41   a . Preferably, an entire portion of the left-mop motor  61   a  may be vertically overlapped with the left spin mop  41   a . At least a part of the right-mop motor  61   b  may be vertically overlapped with the right spin mop  41   b . Preferably, an entire portion of the right-mop motor  61   b  may be vertically overlapped with the right spin mop  41   b.    
     More specifically, the left-mop motor  61   a  and the right-mop motor  61   b  may be vertically overlapped with an imaginary central horizontal line HL connecting a spin rotation axis Osa of the left spin mop  41   a  and a spin rotation axis Osb of the right spin mop  41   b . Preferably, a weight center (a center of gravity) MCa of the left-mop motor  61   a  and a weight center (a center of gravity) MCb of the right-mop motor  61   b  may be vertically overlapped with the imaginary central horizontal line HL connecting the spin rotation axis Osa of the left spin mop  41   a  and the spin rotation axis Osb of the right spin mop  41   b . Alternatively, a geometric center of the left-mop motor  61   a  and a geometric center of the right-mop motor  61   b  may be vertically overlapped with the imaginary central horizontal line HL connecting the spin rotation axis Osa of the left spin mop  41   a  and the spin rotation axis Osb of the right spin mop  41   b . The left-mop motor  61   a  and the right-mop motor  61   b  may be symmetrical with respect to a central longitudinal line Po. 
     Since the weight center MCa of the left-mop motor  61   a  and the weight center MCb of the right-mop motor  61   b  do not deviate from the spin mop  41 , and the left-mop motor  61   a  and the right-mop motor  61   b  are symmetrical to each other. Accordingly, the friction force of the spin mop  41  can be enhanced and running performance and a left-right balance can be maintained. 
     Hereinafter, the spin rotation axis Osa of the left spin mop  41   a  is referred to as a left spin rotation axis Osa, and the spin rotation axis Osb of the right spin mop  41   b  is referred to as a right spin rotation axis Osb. 
     The water tank  81  is disposed at a rear side than the central horizontal line HL, and an amount of water in the water tank  81  is variable. In order to maintain a stable front-rear balance regardless of a water level of the water tank  81 , the left-mop motor  61   a  may be deviated to a left side from the left spin rotation axis Osa. The left-mop motor  61   a  may be deviated to a left front side from the left spin rotation axis Osa. Preferably, the geometric center of the left-mop motor  61   a  or the weight center MCa of the left-mop motor  61   a  may be deviated to the left side from the left spin rotation axis Osa, or the geometric center of the left-mop motor  61   a  or the weight center MCa of the left-mop motor  61   a  may be deviated to the left front side from the left spin rotation axis Osa. 
     The right-mop motor  61   b  may be deviated to a right direction from the right spin rotation axis Osb. The right-mop motor  61   b  may be deviated to a right front side from the right spin rotation axis Osb. Preferably, the geometric center of the right-mop motor  61   b  or the weight center MCb of the right-mop motor  61   b  may be deviated to the right side from the right spin rotation axis Osb, or the geometric center of the right-mop motor  61   b  or the weight center MCb of the right-mop motor  61   b  may be deviated to the right front side from the right spin rotation axis Osb. 
     Since the left-mop motor  61   a  and the right-mop motor  61   b  apply pressure at a position deviated from an outer front side from a center of each spin mop  41 , pressure is concentrated on the outer front side of each spin mop  41 . Therefore, running performance can be improved by the rotational force of the spin mop  41 . 
     The left spin rotation axis Osa and the right spin rotation axis Osb are disposed at a rear side than the center of the body  30 . The central horizontal line HL may be disposed at a rear side of the geometric center Tc of the body  30  and a weight center (a center of gravity) WC of the mobile robot. The left spin rotation axis Osa and the right spin rotation axis Osb are spaced apart at the same distance from the central longitudinal line Po. 
     A left driving joint  65   a  may be disposed on the left spin mop  41   a  (at an upper side of the left spin mop  41   a ), and a right driving joint  65   a  may be disposed on the right spin mop  41   b  (at an upper side of the right spin mop  41   b ). 
     In the present embodiment, one battery Bt may be installed. At least a part of the battery Bt may be disposed on the left spin mop  41   a  and the right spin mop  41   b  (at upper sides of the left spin mop  41   a  and the right spin mop  41   b ). The battery Bt that is relative heavy is disposed on the spin mop  41  (at the supper side of the spin mop  41 ) to improve friction force by the spin mop  41  and reduce eccentricity caused by the rotation of the mobile robot. 
     Specifically, a part of a left portion of the battery Bt may be vertically overlapped with the left spin mop  41   a , and a part of a right portion of the battery Bt may be vertically overlapped with the right spin mop  41   b . The battery Bt may be vertically overlapped with the central horizontal line HL and may be vertically overlapped with the central longitudinal line Po. 
     More specifically, a weight center (a center of gravity) BC of the battery Bt or a geometric center of the battery Bt may be disposed at the central longitudinal line Po and may be disposed at the central horizontal line HL. The weight center BC of the battery Bt or the geometric center of the battery Bt may be disposed at the central longitudinal line Po, may be disposed at a front side of the central horizontal line HL, and may be disposed at a rear side of the geometric center Tc of the body  30 . 
     The weight center of the battery Bt or the geometric center of the battery Bt may be disposed at a front side than the water tank  81  or a weight center PC of the water tank  81 . The weight center BC of the battery Bt or the geometric center Tc of the battery Bt may be disposed at a rear side than a weight center (a center of gravity) SC of the sweep module  2000 . 
     One battery Bt is disposed at a middle portion between the left spin mop  41   a  and the right spin mop  41   b  and is disposed at the central horizontal line HL and the central longitudinal line Po. The battery Bt that is heavy holds centers during rotation of the spin mops  41  and provides weight on the spin mop  41 , thereby improving friction force by the spin mop  41 . 
     A height of the battery Bt (a height of a lower end of the battery Bt) may be the same as heights of the left-mop motor  61   a  and the right-mop motor  61   b  (heights of lower ends of the left-mop motor  61   a  and the right-mop motor  61   b ). Alternatively, the battery Bt may be disposed on the same plane as the left-mop motor  61   a  and the right-mop motor  61   b . The battery Bt may be disposed between the left-mop motor  61   a  and the right-mop motor  61   b . The battery Bt may be disposed at an empty space between the left-mop motor  61   a  and the right-mop motor  61   b.    
     At least a part of the water tank  81  may be disposed on the left spin mop  41   a  and the right spin mop  41   b  (at upper sides of the left spin mob  41   a  and the right spin mop  41   b ). The water tank  81  may be disposed at a rear side than the central horizontal line HL and may be vertically overlapped with the central longitudinal line Po. 
     More specifically, a weight center (a center of gravity) PC of the water tank  81  or a geometric center of the water tank  81  may be disposed at the central longitudinal line Po and may be positioned at a front side than the central horizontal line HL. As another example, the weight center PC of the water tank  81  or the geometric center of the water tank  81  may be disposed at the central longitudinal line Po and may be positioned at a rear side than the central horizontal line HL. In this instance, the phrase that the weight center PC of the water tank  81  or the geometric center of the water tank  81  is disposed at the rear side than the central horizontal line HL may mean that weight center PC of the water tank  81  or the geometric center of the water tank  81  is vertically overlapped with a region deviated rearward from the central horizontal line HL. The weight center PC of the water tank  81  or the geometric center of the water tank  81  may be vertically overlapped with the body  30  without going beyond the body  30 . 
     The weight center PC of the water tank  81  or the geometric center of the water tank  81  may be disposed at a rear side than the weight center BC of the battery Bt. The weight center of the water tank  81  PC or the geometric center of the water tank  81  may be disposed at a rear side than the weight center SC of the sweep module  2000 . 
     A height of the water tank  81  (a height of a lower end of the water tank  81 ) may be the same as heights of the left-mop motor  61   a  and the right-mop motor  61   b  (heights of lower ends of the left-mop motor  61   a  and the right-mop motor  61   b ). Alternatively, the water tank  81  may be disposed on the same plane as the left-mop motor  61   a  and the right-mop motor  61   b . The water tank  81  may be disposed at an empty space between the left-mop motor  61   a  and the right-mop motor  61   b.    
     The sweep module  2000  may be disposed at a front side than the spin mops  41 , the battery Bt, the water tank  81 , the mop driving unit  60 , the right-mop motor  61   b , and the left-mop motor  61   a  at the body. 
     The weight center SC of the sweep module  2000  or a geometric center of the sweep module  2000  may be disposed at the central longitudinal line Po and may be disposed at a front side than the geometric center Tc of the body  30 . When viewed from an upper side, the body  30  may have a circular shape and the base  32  may have a circular shape. The geometrical center Tc of the body  30  may means a center of the body  30  when the body  30  has the circular shape. Specifically, when viewed from an upper side, the body  30  may have a circular shape with a half-diameter error of less than 3%. 
     Specifically, the weight center SC of the sweep module  2000  or the geometric center of the sweep module  2000  may be disposed at the central longitudinal line Po, and may be disposed at a front side than the weight center BC of the battery Bt, the weight center PC of the water tank  81 , the weight center MCa of the left-mop motor  61   a , the weight center MCb of the right-mop motor  61   b , and the weight center WC of the mobile robot. 
     Preferably, the weight center SC of the sweep module  2000  or the geometric center of the sweep module  2000  may be disposed at a front side than the central horizontal line HL and a front end of the spin mops  41 . 
     The sweep module  2000  may include a dust housing  2100  having a storage space  2104 , an agitator  2200 , and a sweep motor  2330  as described above. 
     The agitator  2200  may be rotatably installed on the dust housing  2100  and may be disposed at a rear side than the storage space  2104 . Therefore, the agitator  2200  may have an appropriate length to cover the left and right spin mops  41   a  and  41   b  and not to protrude to an outside of the body. 
     A rotation axis of the agitator  2200  may be parallel to the central horizontal line HL, and a center of the agitator  2200  may be positioned at the imaginary central longitudinal line Po. Therefore, a large foreign material flowing into the spin mops  41  can be effectively removed by the agitator  2200 . The rotation axis of the agitator  2200  may be disposed at a front side of the geometric center Tc of the body  30 . A length of the agitator  2200  may be preferably longer than a distance between the left spin rotation axis Osa and the right spin rotation axis Osb. The rotation axis of the agitator  2200  may be disposed to be adjacent to a front end of the spin mop  41 . 
     A left caster  58   a  and a right caster  58   b  being in contact with the floor may be further provided at both ends of the dust housing  2100 . The left caster  58   a  and the right caster  58   b  are rolled while being in contact with the floor and may move up and down by elastic force. The left caster  58   a  and the right caster  58   b  may support the sweep module  2000  and a part of the body. The left caster  58   a  and the right caster  58   b  may protrude from a lower end of the dust housing  2100  to a lower side. 
     The left caster  58   a  and the right caster  58   b  are disposed at a line parallel to the central horizontal line HL, and may be disposed at a front side than the central horizontal line HL and the agitator  2200 . An imaginary line connecting the left caster  58   a  and the right caster  58   b  may be disposed at a front side than the central horizontal line HL, the agitator  2200 , and the geometric center Tc of the body  30 . The left caster  58   a  and the right caster  58   b  may be bisymmetrical to each other with respect to the central longitudinal line Po. The left caster  58   a  and the right caster  58   b  may be spaced apart at the same distance from the central longitudinal line Po. 
     The geometric center Tc of the body  30 , the weight center WC of the mobile robot, the weight center SC of the sweep module  2000 , and the weight center BC of the battery Bt may be disposed in an imaginary quadrangle formed by sequentially connecting the left caster  58   a , the right caster  58   b , the right spin rotation axis Osb, and the left spin rotation axis Osa. The battery Bt, which is relatively heavy, the left spin rotation axis Osa, and the right spin rotation axis Osb may be disposed to be adjacent to the central horizontal line HL. Then, a main load of the mobile robot may be applied to the spin mops  41  and a remaining sub-load may be the left caster  58   a  and the right caster  58   b.    
     The sweep motor  2330  may disposed at the central longitudinal line Po. When the sweep motor  2330  is disposed at one side based on the central longitudinal line Po, the pump  85  is disposed at the other side based on the central longitudinal line Po (refer to  FIG.  19   ) so that a sum weight center of the sweep motor  2330  and the pump  85  may be disposed on the central longitudinal line Po. 
     Therefore, the weight center of the mobile robot at a relatively front side is maintained regardless of the water level of the water tank  81  disposed at a rear side, thereby increasing friction force by the spin mop  41 . Also, the weight center WC of the mobile robot is disposed to be adjacent to the geometric center Tc of the body  30  and thus stable driving can be achieved. 
     A weight center (a center of gravity) COC of a controller Co or a geometric center of the controller Co may be disposed at a front side than the geometric center Tc of the body  30  and the central horizontal line HL. At least a 50% or more portion of the controller Co may be vertically overlapped with the sweep module  2000 . 
     The weight center WC of the mobile robot may be disposed at the central longitudinal line Po, may be disposed at a front side than the central horizontal line HL, may be disposed at a front side than the weight center BC of the battery Bt, and may be disposed at a front side than the weight center PC of the water tank  81 , may be disposed at a rear side than the weight center SC of the sweep module  2000 , and may be disposed at a rear side than the left caster  58   a  and the right caster  58   b.    
     By disposing components or elements symmetrically with respect to the central longitudinal line Po or considering weights of the components or elements, the weight center WC of the mobile robot is disposed at the central longitudinal line Po. Accordingly, stability in a left-right direction can be improved. 
       FIG.  33    is a bottom view of a mobile robot according to another embodiment of the present disclosure for explaining a relationship between a weight center and other components. 
     Referring to  FIG.  33   , an embodiment will be described. A difference compared to the embodiment described with reference to  FIG.  31    will be mainly described. A component or an element that is not described with respect to  FIG.  33    may be regarded as the same as that of the embodiment described with reference to  FIG.  31   . 
     A weight center WC of a mobile robot and a geometric center Tc of a body  30  may be disposed in an imaginary second quadrangle SQ 2  formed by sequentially connecting a left caster  58   a , a right caster  58   b , a right spin rotation axis Osb, and a left spin rotation axis Osa. A weight center MCa of a left-mop motor, a weight center MCb of a right-mop motor, and a weight center PC of a water tank may be disposed at an outside of the imaginary second quadrangle SQ 2 . 
     Also, a weight center WC of a mobile robot, a geometric center Tc of a body  30 , a weight center BC of a battery Bt may be disposed in an imaginary second quadrangle SQ 2  formed by sequentially connecting a left caster  58   a , a right caster  58   b , a right spin rotation axis Osb, and a left spin rotation axis Osa. 
     In addition, a weight center WC of a mobile robot, a geometric center Tc of a body  30 , and a weight center SC of a sweep module  2000 , may be disposed in an imaginary second quadrangle SQ 2  formed by sequentially connecting a left caster  58   a , a right caster  58   b , a right spin rotation axis Osb, and a left spin rotation axis Osa. 
     Further, a weight center WC of a mobile robot, a geometric center Tc of a body  30 , a weight center SC of a sweep module  2000 , and a weight center BC of a battery Bt may be disposed in an imaginary second quadrangle SQ 2  formed by sequentially connecting a left caster  58   a , a right caster  58   b , a right spin rotation axis Osb, and a left spin rotation axis Osa. 
     The weight center WC of the mobile robot, the geometric center TC of the body, the weight center SC of the sweep module  2000 , and the weight center BC of the battery Bt may be disposed in the second quadrangle SQ 2 , and the weight center MCa of the left-mop motor and the weight center MCb of the right-mop motor may be disposed at an outside of the second quadrangle SQ 2 . Then, the mobile robot can apply appropriate friction force to the mop portion while stably travelling. 
     The weight center WC of the mobile robot and the geometric center TC of the body may be disposed in the second quadrangle SQ 2 , and the weight center MCa of the left-mop motor and the weight center MCb of the right-mop motor may be disposed at an outside of the second quadrangle SQ 2 . Then, the mobile robot can apply appropriate friction force to the mop portion while stably travelling. 
     The weight center WC of the mobile robot and the geometric center TC of the body may be disposed in an imaginary first quadrangle SQ 1  formed by sequentially connecting the left caster  58   a , the right caster  58   b , the lowest point at a lower surface of the right spin mop  41   b , and the lowest point at a lower surface of the left spin mop  41   a . The weight center MCa of the left-mop motor and the weight center MCb of the right-mop motor may be disposed at an outside of the first quadrangle SQ 1 . 
     Firstly, according to the present disclosure, interference or impact with or from an obstacle can be minimized since a dustpan is rotated and is accommodated into a collection space positioned at inside of a dust housing when the dustpan is interfered with the obstacle on a floor. 
     Secondly, according to the present disclosure, a collected foreign material can be transferred to a collection space, even if a dustpan collides with an obstacle on a floor, since the dustpan is rotatable with respect to a rotation axis of the agitator. 
     Thirdly, according to the present disclosure, a collected foreign material can be transferred to a collection space in a state confined between a dustpan and an agitator since the dustpan is in contact with an outer circumferential surface of the agitator. 
     Fourthly, according to the present disclosure, a dustpan can be returned to its original position by using an elastic force of a pan elastic member since the pan elastic member connects the dustpan and a housing assembly, 
     Fifthly, according to the present disclosure, an impact due to a contact with an obstacle can be minimized since a dust guard, which is disposed at a lower end of the dustpan and is in contact with a floor, is formed of an elastic material. 
     Sixthly, according to the present disclosure, excessive rotation of a dustpan can be prevented by a dustpan stopper disposed at a housing assembly and disposed within a rotational radius of the dustpan. 
     Seventhly, according to the present disclosure, resistance against a driving or traveling direction of a cleaner can be minimized and a dustpan disposed at a rear side of an agitator can effectively collect a foreign material moved through sweeping of the agitator since the agitator rotates from a front side to a rear side. 
     Eighthly, according to the present disclosure, by disposing an agitator close to a center of a body in a structure in which the agitator and a dust housing are integrated with each other, the agitator is not disturbed by an external obstacle and a width of the agitator in a left-right direction can be maximized. Thereby, a cleaning area can be maximized, a body can escape quickly when trapped in the obstacle, and the body can rotate easily. 
     Ninthly, according to the present disclosure, rotation of a cleaner can be easy by a circular shape of a body. A size of an area to be cleaned by a spin mop at once can be maximized and rotation of a body is not disturbed by a shape of the spin mop when the body rotates, since rotation axes of a pair of spin mops are eccentrical or deviated from a center of the body and a part of each spin mop is overlapped with the body vertically. That is, a part of each spin mop is exposed to an outside of the body. Even if the spin mop is exposed to the outside of the body, the spin mop has a circular shape, and thus, friction between an obstacle and the spin mop is reduced when the body rotates. Accordingly, the rotation of the body can be easy. 
     Tenthly, according to the present disclosure, a body has a circular shape and a dry-type module does not protrude to an outside of the body. Accordingly, the cleaner can be freely rotated at any position in a cleaning area. Also, an agitator can have a sufficiently large width, and thus, a cleaning range can be wide. Further, a mopping operation while collecting a foreign material having a relatively large size can be performed.