Patent Publication Number: US-2023148818-A1

Title: Cleaner

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. Application No. 17/526,392, filed on Nov. 15, 2021, which is a continuation of U.S. Application No. 16/333,131, filed on Dec. 19, 2019, which is U.S. National Phase entry under 35 U.S.C. § 371 from PCT International Application No. PCT/KR2017/007551, filed Jul. 14, 2017, which claims the benefit of priority of U.S. Provisional Application No. 62/362,358, filed Jul. 14, 2016, the contents of all of which are incorporated herein by reference in their entireties. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a cleaner that performs mopping. 
     Description of Related Art 
     A cleaner is a device that performs cleaning by suctioning dirt such as dust from the floor or mopping dirt on the floor. Recently, a cleaner capable of performing mopping has been developed. In addition, a robot cleaner is a device that performs cleaning autonomously via self-driving. 
     There has been known a robot cleaner capable of moving using a mop surface as the prior art (Korean Registered Patent No. 10-1602790). 
     1. Korean Registered Patent No. 10-1602790 (Registered Date: Mar. 7, 2016) 
     Technical Problem 
     A first object of the present invention is to increase frictional force between a mop and a floor surface so that a cleaner performs a mopping operation and travels effectively. 
     The aforementioned robot cleaner of the prior art is supported by a pair of left and right mops in a two-point support manner, and thus has a problem in that stability in the forward-and-backward direction is deteriorated. A second object of the present invention is to solve this problem, thereby improving the stability of the robot cleaner in the leftward-and-rightward direction and in the forward-and-backward direction. 
     The aforementioned robot cleaner of the prior art moves via rotation of a pair of left and right mops. However, the frictional force that is generated by rotation of the pair of mops varies frequently, and it is therefore difficult for the robot cleaner of the prior art to travel straight. If the robot cleaner cannot travel straight, an area that is not wiped by the robot cleaner increases in a floor surface on which the robot cleaner needs to travel straight, e.g. a floor surface near a wall. A third object of the present invention is to solve this problem. 
     The aforementioned robot cleaner of the prior art, which moves via rotation of a pair of left and right mops, has limitations pertaining to a traveling speed and a traveling route. A fourth object of the present invention is to solve this problem, thereby enabling the robot cleaner to realize various traveling speeds and traveling routes. 
     The aforementioned robot cleaner of the prior art, which moves via rotation of a pair of left and right mops, has a problem in that it is difficult to perform a mopping operation without rotating in place or moving linearly. A fifth object of the present invention is to solve this problem, thereby enabling the robot cleaner to perform a mopping operation even when the robot cleaner stays in place without rotating. 
     A sixth object of the present invention is to efficiently remove moisture that is left on a floor surface after a wet mopping operation. 
     A seventh object of the present invention is to provide a cleaner that performs mopping and sterilization at the same time. 
     An eighth object of the present invention is to provide a device that is capable of performing a wet mopping operation and a dry cleaning operation (dry mopping, vacuum cleaning, and/or sweeping using brushes) in combination, thereby performing a thorough and efficient mopping operation. 
     Technical Solution 
     In accordance with the present invention, the above and other objects can be accomplished by the provision of a cleaner including a first cleaning module including a left spin mop and a right spin mop provided so as to come into contact with a floor while rotating in a clockwise direction or in a counterclockwise direction when viewed from the upper side, a second cleaning module configured so as to come into contact with the floor at a position spaced apart from the left spin mop and the right spin mop in a forward-and-backward direction, a body supported by the first cleaning module and the second cleaning module, and a water supply module configured to supply water to the first cleaning module and including a water tank disposed inside the body. 
     The body may move via rotation of the left spin mop and the right spin mop without a separate driving wheel. 
     The second cleaning module may include a rolling member configured to rotate about a rotation axis extending in the horizontal direction. 
     The body may move via rotation of at least one of the left spin mop, the right spin mop, or the rolling member without a separate driving wheel. 
     Water supplied by the water supply module may reach the first cleaning module before reaching the floor. 
     The direction in which the rolling member rotates may be changeable. 
     When the first cleaning module performs a predetermined constant rotation operation, the rolling member may perform two or more different rotation operations. 
     The second cleaning module may include a mop unit or a brush, a rotary member for fixing the mop unit or the brush, a first shaft member for connecting one end portion of the rotary member and the body to each other, a second shaft member for connecting the opposite end portion of the rotary member and the body to each other, and a rolling drive unit for providing drive force for rotating the rolling member. 
     The rolling member may rotate about a rotation axis extending in the leftward-and-rightward direction. 
     The rolling member may include any one of a mop unit for mopping the floor and a brush for sweeping the floor. 
     The first cleaning module may include a left rotating plate for fixing a mop unit of the left spin mop, a left spin shaft fixed to the left rotating plate to rotate the left rotating plate, a left spin-drive unit for providing power required for rotating the left spin shaft, a right rotating plate for fixing a mop unit of the right spin mop, a right spin shaft fixed to the right rotating plate to rotate the right rotating plate, and a right spin-drive unit for providing power required for rotating the right spin shaft. 
     The point on the bottom surface of the left spin mop that receives largest frictional force from the floor may be located to the left of the rotation center of the left spin mop, and the point on the bottom surface of the right spin mop that receives largest frictional force from the floor may be located to the right of the rotation center of the right spin mop. 
     The second cleaning module may include a rolling member including a mop unit configured to rotate about a rotation axis extending in the leftward-and-rightward direction. The contact area between the rolling member and the floor may overlap the entire area of the gap between the rotation center of the left spin mop and the rotation center of the right spin mop when viewed from the front side. 
     The water supply module may supply water to the first cleaning module without supplying water to the second cleaning module. Each of the first cleaning module and the second cleaning module may be configured to mop the floor. 
     The water tank may be disposed such that the center of gravity of the water tank is located closer to a portion of the first cleaning module that contacts the floor than to a portion of the second cleaning module that contacts the floor in the forward-and-backward direction. 
     The cleaner may further include a battery for supplying power. The battery may be disposed such that the center of gravity of the battery is located closer to a portion of the first cleaning module that contacts the floor than to a portion of the second cleaning module that contacts the floor in the forward-and-backward direction. 
     The cleaner may further include an ultraviolet (UV) light-emitting diode configured to emit UV rays downwards and disposed between the first cleaning module and the second cleaning module. 
     The cleaner may further include a sterilized-water-generating module configured to generate sterilized water via electrolysis of water inside the water tank. 
     The cleaner may further include a sensing module including at least one of a bumper for sensing contact with an external obstacle, an obstacle sensor for sensing an external obstacle that is spaced apart from the cleaner, or a cliff sensor for sensing presence or absence of a cliff on a traveling surface, and a controller configured to receive a sensing signal from the sensing module and to control autonomous travel of the cleaner. 
     Advantageous Effects 
     The cleaner is supported by the first cleaning module and the second cleaning module, thereby enhancing mopping efficiency. 
     In addition, the stability of the cleaner in the leftward-and-rightward direction may be ensured by the left spin mop and the right spin mop, which are arranged in the leftward-and-rightward direction, and the stability of the cleaner is also improved by the second cleaning module, which is disposed behind the first cleaning module and is brought into contact with the floor. 
     Specifically, on the basis of the support point of the first cleaning module, the second cleaning module prevents the cleaner from overturning in the backward direction, and the mop surface of the first cleaning module prevents the cleaner from overturning in the forward direction. 
     In addition, since wobbling of the cleaner in the leftward-and-rightward direction is minimized by the frictional force provided by the second cleaning module, the cleaner is capable of traveling straight while being moved by the frictional force of the mop surface. 
     In addition, through the provision of the water tank disposed inside the body, the body transmits a relatively large load to the first cleaning module, thereby performing more effective mopping. 
     In addition, through the provision of the water supply module for supplying water to the first cleaning module, the cleaner is capable of performing wet mopping without requiring the user to supply water to the mop. 
     In addition, through the provision of the rolling member that rotates about a rotation axis extending in the horizontal direction, additional moving force may be efficiently applied to the body via rotation of the rolling member. Accordingly, it is possible to realize various types of traveling motion (traveling route and traveling speed) of the cleaner. 
     In addition, through the provision of the rolling member that rotates about a rotation axis extending in the leftward-and-rightward direction, moving force may be additionally applied to the body in the forward-and-backward direction via rotation of the rolling member. Accordingly, it is possible to realize various and efficient traveling motion of the cleaner. 
     When the first cleaning module performs a predetermined constant rotation operation, the rolling member is capable of performing two or more different rotation operations. Accordingly, it is possible to realize various traveling routes and traveling speeds of the cleaner. 
     In addition, since the rotating direction of the rolling member can be changed, it is possible to combine one of two types of frictional force generated in two directions by the rolling member with the frictional force generated by the first cleaning module. Accordingly, the cleaner is capable of performing various operations. Specifically, the allowable maximum speed of the cleaner in the forward-and-backward direction may be further increased. In addition, the cleaner is capable of turning to the right or to the left with various turning radii. In addition, the cleaner is capable of turning to the right or to the left while moving backward, and is capable of performing mopping via rotation while the body stays in place. 
     In addition, in the configuration in which water is first sprayed onto the floor and left and right spin mops subsequently wipe the floor, there is a high probability that some water is left on the floor and that only a portion of the spin mop is wet with a large amount of water and thus water is not evenly supplied to the entire area of the spin mop. The present invention is configured such that water reaches the first cleaning module before reaching the floor, thereby reducing the probability that water is left on the floor after mopping and facilitating dispersion of water to the entire area of the spin mop. 
     By allowing the contact area between the rolling member and the floor to overlap the entire area of the gap between the rotation center of the left spin mop and the rotation center of the right spin mop, the rolling member performs an operation of mopping an area of the floor that corresponds to the gap between the left spin mop and the right spin mop, thereby supplementing the mopping operation of the first cleaning module. In addition, the rolling member performs an operation of mopping an area of the floor to which relatively low frictional force is applied from the mop surface of the first cleaning module, thereby supplementing the mopping operation of the first cleaning module. 
     In addition, by allowing the center of gravity of the water tank and/or the center of gravity of the battery to be located relatively close to the first cleaning module, it is possible to further increase the ratio of the size of the load that is transmitted to the first cleaning module to the size of the load that is transmitted to the second cleaning module and to allow the first cleaning module, which is capable of realizing various operations, to primarily control the travel of the cleaner. 
     Through the provision of the UV LED that is disposed between the first cleaning module and the second cleaning module, when the cleaner performs cleaning while moving forwards, the UV LED radiates UV rays to the floor mopped by the first cleaning module to sterilize the same, and subsequently the second cleaning module performs an operation of cleaning the floor sterilized by the UV rays. 
     By supplying sterilized water to the first cleaning module, the UV LED radiates UV rays to the floor mopped with the sterilized water by the first cleaning module to sterilize the same, and subsequently the second cleaning module performs an operation of cleaning the floor sterilized by the UV rays. 
     Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of a cleaner  100  according to an embodiment of the present invention. 
         FIG.  2    is a perspective view of the cleaner  100  in  FIG.  1    viewed at a different angle. 
         FIG.  3 A  is a front elevational view of the cleaner  100  in  FIG.  1   . 
         FIG.  3 B  is a front elevational view of a cleaner  100 ′ according to another embodiment of the present invention. 
         FIG.  4    is a rear elevational view of the cleaner  100  in  FIG.  1   . 
         FIG.  5    is a (left) side elevational view of the cleaner  100  in  FIG.  1   . 
         FIG.  6    is a bottom view of the cleaner  100  in  FIG.  1   . 
         FIG.  7    is a top view of the cleaner  100  in  FIG.  1   . 
         FIG.  8    is a vertical cross-sectional view of the cleaner  100  taken along line S1-S1’ in  FIG.  6   . 
         FIG.  9    is a vertical cross-sectional view of the cleaner  100  taken along line S2-S2’ in  FIG.  6   . 
         FIG.  10    is a vertical cross-sectional view of the cleaner  100  taken along line S3-S3’ in  FIG.  6   . 
         FIG.  11    is a vertical cross-sectional view of the cleaner  100  taken along line S4-S4’ in  FIG.  6   . 
         FIG.  12    is a vertical cross-sectional view of the cleaner  100  taken along line S5-S5’ in  FIG.  7   . 
         FIG.  13    is a perspective view illustrating the inner surface of a case  11  of the cleaner  100  in  FIG.  1   . 
         FIG.  14    is a perspective view illustrating the state in which a water tank opening/closing unit  153  is removed from the cleaner  100  in  FIG.  1   . 
         FIGS.  15 A and  15 B  are perspective views illustrating the state in which the case  11  is removed from the cleaner  100  in  FIG.  1   . 
         FIGS.  16 A and  16 B  are perspective views illustrating the state in which a battery  160  is removed from the cleaner  100  in  FIGS.  15 A and  15 B . 
         FIG.  17    is a top view of the cleaner  100  in  FIGS.  16 A and  16 B . 
         FIG.  18    is a vertical partial cross-sectional view of the cleaner  100  taken along line S6-S6’ in  FIG.  17   . 
         FIG.  19    is a perspective view of a first cleaning module  120  and a second cleaning module  130  of the cleaner  100  in  FIG.  1   . 
         FIG.  20    is a perspective view of spin mops  120   a  and  120   b  in  FIG.  19   . 
         FIG.  21    is a top view of the spin mops  120   a  and  120   b  in  FIG.  20   . 
         FIG.  22    is a vertical cross-sectional view of the spin mops  120   a  and  120   b  taken along line S7-S7’ in  FIG.  21   . 
         FIG.  23    is a perspective view illustrating the state in which a mop unit  121  is removed from the spin mops  120   a  and  120   b  in  FIG.  20   . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Expressions referring to directions such as “front (F)/rear (R)/left (Le)/right (R)/upper (U)/lower (D)” mentioned below are defined based on the illustrations in the drawings, but this is merely given to describe the present invention for clear understanding thereof, and it goes without saying that the respective directions may be defined differently depending on where the reference is placed. 
     With regard to any one spin mop with reference to  FIG.  22   , the center axis X is the rotational axis about which the spin mop rotates, the centrifugal direction XO is the direction moving away from the center axis X, and the counter-centrifugal direction XI is the direction approaching the center axis X. 
     The use of terms, in front of which adjectives such as “first”, “second”, and “third” are used to describe constituent elements mentioned below, is intended only to avoid confusion of the constituent elements, and is unrelated to the order, importance, or relationship between the constituent elements. For example, an embodiment including only a second component but lacking a first component is also feasible. 
     The “mop” mentioned below may be variously embodied in terms of material, such as cloth or paper material, and may be used repeatedly by washing, or may be disposable. 
     The present invention may be applied to a cleaner that is manually moved by a user, a robot cleaner that autonomously travels, or the like. Hereinafter, the present embodiment will be described with reference to a robot cleaner. 
     Referring to  FIGS.  1  to  16 B , a cleaner  100  according to an embodiment of the present invention includes a body  110  and a controller  20  mounted in the body  110 . The cleaner  100  includes a first cleaning module  120  for supporting the body  110 . The cleaner  100  includes a second cleaning module  130  for supporting the body  110 . The body  110  is supported by the first cleaning module  120  and the second cleaning module  130 . 
     The first cleaning module  120  is configured to perform mopping via contact with the floor. The first cleaning module  120  includes a left spin mop  120   a  and a right spin mop  120   b , which are configured to perform mopping while rotating clockwise or counterclockwise when viewed from the upper side. The left spin mop  120   a  and the right spin mop  120   b  are configured so as to come into contact with the floor. The first cleaning module  120  is disposed at the lower side of the body  110 . The first cleaning module  120  is disposed in front of the second cleaning module  130 . The cleaner  100  may be configured such that the body  110  can move via rotation of the first cleaning module  120  without a separate driving wheel. That is, the body may move via rotation of the left spin mop  120   a  and the right spin mop  120   b  without a separate driving wheel. Here, the term “driving wheel” refers to a wheel having a traveling function to move the body, and thus an auxiliary wheel, which does not have a traveling function but supports the body with respect to the floor, is not considered a driving wheel. 
     The first cleaning module  120  includes a pair of spin mop modules  120 . The first cleaning module  120  includes a left spin mop module  120 , which is provided with a left spin mop  120   a . The first cleaning module  120  includes a right spin mop module  120 , which is provided with a right spin mop  120   b . The left spin mop module  120  and the right spin mop module  120  are configured to perform mopping. Each of the left spin mop module  120  and the right spin mop module  120  includes a mop unit  121 , a rotating plate  122 , a water supply reservoir  123 , a spin shaft  128 , a spin-drive unit  124 , and a driving transmission unit  127 . Each of the left spin mop module  120  and the right spin mop module  120  includes a tilting frame  125 , a tilting rotary shaft  126 , and an elastic member  129 . The components that the first cleaning module  120  includes may be understood as components that each of the left spin mop module  120  and the right spin mop module  120  includes. 
     The second cleaning module  130  is configured so as to come into contact with the floor. The second cleaning module  130  may be configured to perform mopping via contact with the floor. The second cleaning module  130  is disposed at the lower side of the body  110 . The second cleaning module  130  is disposed behind the first cleaning module  120  so as to come into contact with the floor. 
     In the present embodiment, the second cleaning module  130  is configured to perform mopping via rotation thereof. In another example, the second cleaning module may include a mop pad, which performs mopping via sliding on the floor along with the movement of the body  110 . In a further example, the second cleaning module may be configured to perform a vacuum-cleaning operation. 
     The second cleaning module  130  may include a rolling member  130   a . 
     The second cleaning module  130  may be configured to perform mopping or sweeping via rotation thereof. The rolling member  130   a  may include a mop unit  131  for mopping the floor or a brush (not shown) for sweeping the floor. 
     In the present embodiment, the rolling member  130   a  includes a mop unit  131  for mopping the floor. The mop unit  131  is provided so as to be rotatable. The mop unit  131  may rotate about a rotation axis that extends in the substantially horizontal direction. The mop unit  131  may rotate about a rotation axis that extends in the substantially leftward-and-rightward direction. 
     In another example, the rolling member  130   a  may include a brush for sweeping the floor. The brush may be rotatably provided. The brush may rotate about a rotation axis that extends in the substantially horizontal direction. The brush may rotate about a rotation axis that extends in the substantially leftward-and-rightward direction. The cleaner may include a dust container. When the brush sweeps the floor, a foreign substance having a relatively large volume may be introduced into the dust container. 
     Although the present invention will be described below with reference to the present embodiment, the concrete configuration for the cleaning operation of the second cleaning module  130  may be variously modified. 
     The second cleaning module  130  is configured to perform mopping while rotating clockwise or counterclockwise when viewed from one side (the left side or the right side). The cleaner  100  may be configured such that the body  110  can move via rotation of the second cleaning module  130  without a separate driving wheel. The body  110  may move via rotation of the rolling member  130   a  without a separate driving wheel. 
     The cleaner  100  is configured such that the body  110  moves via rotation of at least one of the first cleaning module  120  or the second cleaning module  130  without a separate driving wheel. The body  110  may move only via rotation of the first cleaning module  120 . The body  110  may move only via rotation of the second cleaning module  130 . The body  110  may move via rotation of the first cleaning module  120  and rotation of the second cleaning module  130 . The cleaner  100  is configured such that the body  110  moves via rotation of at least one of the left spin mop  120   a , the right spin mop  120   b , or the rolling member  130   a  without a separate driving wheel. 
     The cleaner  100  includes a water supply module  150  for supplying water required for mopping. The water supply module  150  may supply water required for the mopping operation of the first cleaning module  120  or the second cleaning module  130 . In the present embodiment, the water supply module  150  supplies water to the first cleaning module  120 . The water supply module  150  supplies water to the left spin mop module  120  and the right spin mop module  120 . The water supply module  150  supplies water to the left spin mop  120   a  and the right spin mop  120   b . 
     The water supply module  150  includes a water tank  151  for storing water that is to be supplied to the first cleaning module  120  or the second cleaning module  130 . In the present embodiment, the water tank  151  stores water that is to be supplied to the first cleaning module  120 . The water tank  151  is disposed within the body  110 . 
     The water supplied by the water supply module  150  reaches the first cleaning module before reaching the floor. The water supplied by the water supply module  150  reaches the left spin mop  120   a  and the right spin mop  120   b  before reaching the floor. The water supplied by the water supply module  150  is supplied to the top surfaces of the left spin mop  120   a  and the right spin mop  120   b , and penetrates the left spin mop  120   a  and the right spin mop  120   b . 
     The first cleaning module  120  and the second cleaning module  130  are configured to mop the floor. In the present embodiment, the first cleaning module  120  is configured to perform wet mopping (mopping with water), and the water supply module  150  supplies water to the first cleaning module  120 . In addition, in the present embodiment, the second cleaning module  130  is configured to perform dry mopping (mopping without water), and the water supply module  150  does not supply water to the second cleaning module  130 . In the present embodiment, the water supply module  150  supplies water only to the first cleaning module  120 , but not to the second cleaning module  130 . According to the present embodiment, configured as described above, when the cleaner  100  performs a cleaning operation via forward movement, the first cleaning module  120  may first perform a wet mopping operation with respect to the floor surface, and subsequently the second cleaning module  130  may perform a dry mopping operation with respect to the wet-mopped floor surface. 
     Hereinafter, the embodiment will be described under the assumption that the first cleaning module  120  performs wet mopping and the second cleaning module  130  performs dry mopping, but the invention is not limited thereto. The water supply module  150  may be configured to supply water to the second cleaning module  130 , rather than to the first cleaning module  120 , or may be configured to supply water to both the first cleaning module  120  and the second cleaning module  130 . 
     The cleaner  100  includes a battery  160  for supplying power. The battery  160  may supply power required for rotation of the first cleaning module  120 . The battery  160  may supply power required for rotation of the second cleaning module  130 . 
     Referring to  FIG.  11   , the center of gravity Mw of the water tank  151  refers to the center of gravity Mw of the water tank  151  and water W in the state in which the water tank  151  is filled with water W. The center of gravity Mw of the water tank  151  may be located closer to the portion of the first cleaning module  120  that contacts the floor than to the portion of the second cleaning module  130  that contacts the floor in the forward-and-backward direction. Because water W has a relatively high specific gravity, the water W may increase the ratio of the amount of weight of the body  110  that is applied to the first cleaning module  120  to the amount of weight of the body  110  that is applied to the second cleaning module  130 . Accordingly, the rotation of the first cleaning module  120  has a greater influence on the movement of the body  110  than the rotation of the second cleaning module  130 . 
     Referring to  FIG.  11   , the center of gravity Mb of the battery  160  may be located closer to the portion of the first cleaning module  120  that contacts the floor than to the portion of the second cleaning module  130  that contacts the floor in the forward-and-backward direction. Because the battery  160  has a relatively high specific gravity, the battery  160  may increase the ratio of the amount of weight of the body  110  that is applied to the first cleaning module  120  to the amount of weight of the body  110  that is applied to the second cleaning module  130 . Accordingly, the rotation of the first cleaning module  120  has a greater influence on the movement of the body  110  than the rotation of the second cleaning module  130 . 
     The cleaner  100  includes a case  11  forming the external appearance thereof. The case  11  forms the top surface, the front surface, the rear surface, the left surface and the right surface of the body  110 . The cleaner  100  includes a base  13  forming the bottom surface of the body  110 . The first cleaning module  120  is fixed to the base  13 . The second cleaning module  130  is fixed to the base  13 . The cleaner  100  includes a rolling member housing  12 , which is disposed at the base  13  and is recessed upwards in order to receive the upper portion of the rolling member  130   a . The controller  20 , the water supply module  150  and the battery  160  are disposed in the internal space, which is defined by the case  11 , the base  13  and the rolling member housing  12 . 
     The cleaner  100  includes a water tank opening/closing unit  153  for opening or closing the water tank  151 . The water tank opening/closing unit  153  is disposed at the top surface of the body  110 . The cleaner  100  may include a water level indicator (not shown) for indicating the water level in the water tank  151 . The water level indicator may be formed of a transparent material so that a user can observe the water level in the water tank  151  disposed in the body  110 . 
     The cleaner  100  includes a sensing module (not shown) for sensing the external circumstances. The sensing module may include at least one of a bumper  115  for sensing contact with an external obstacle, an obstacle sensor  16  for sensing an external obstacle that is spaced apart from the cleaner, or a cliff sensor  17  for sensing the presence or absence of a cliff on the traveling surface (the floor). The sensing module may include an image sensor (not shown) for capturing an image of the external circumstances. The cleaner  100  may be configured to move autonomously. It is possible to realize a robot cleaner  100  that is capable of traveling autonomously using information sensed by the sensing module. 
     The cleaner  100  includes the obstacle sensor  16  that senses an obstacle ahead of the cleaner  100 . The obstacle sensor  16  may include a plurality of obstacle sensors  16   a ,  16   b  and  16   c . The obstacle sensor  16  is disposed at the front surface of the body  110 . 
     The cleaner  100  includes the cliff sensor  17 , which senses the presence or absence of a cliff on the floor within the region to be cleaned. The cliff sensor  17  may include a plurality of cliff sensors  17   a ,  17   b  and  17   c . The cliff sensor  17   a  may sense the presence or absence of a cliff ahead of the first cleaning module  120 . The cliff sensors  17   b  and  17   c  may sense the presence or absence of a cliff behind the second cleaning module  130 . Referring to  FIG.  11   , the cliff sensor  17  senses the presence or absence of a cliff by transmitting a sensing signal in the downward direction CS. The cliff sensor  17   a  senses the presence or absence of a cliff in the region ahead of the lowest points P1a and P1b of the first cleaning module  120 . The cliff sensors  17   b  and  17   c  sense the presence or absence of a cliff in the region behind the lowest point (the portion that contacts the floor) of the second cleaning module  130 . 
     The cleaner  100  may include a power switch (not shown) for turning on or off the supply of power. The cleaner  100  may include an input unit (not shown), to which a user inputs various commands. The cleaner  100  may include a communication module (not shown) for communicating with an external device. 
     The cleaner  100  includes an ultraviolet (UV) light-emitting diode (LED)  18  that emits UV rays downwards. The UV LED  18  is disposed between the first cleaning module  120  and the second cleaning module  130 . The UV LED  18  is disposed at the bottom surface of the body  110  so as to emit UV rays to the external floor surface. The UV LED  18  is disposed at the bottom surface of the base  13 . The UV LED  18  may include a plurality of UV LEDs  18   a  and  18   b . The UV LEDs  18   a  and  18   b  include a UV LED  18   a  disposed between the left spin mop  120   a  and the rolling member  130   a  and a UV LED  18   b  disposed between the right spin mop  120   b  and the rolling member  130   a . Accordingly, when the cleaner  100  performs a cleaning operation via forward movement, the first cleaning module  120  may first perform an operation of mopping the floor, the UV LED  18  may radiate UV rays to the mopped floor to sterilize the same, and subsequently the second cleaning module  130  may perform an operation of cleaning the floor sterilized by the UV rays. 
     The cleaner  100  may include the communication module (not shown), which is configured to communicate with a predetermined network. According to the communication protocol, the communication module may be implemented using a wireless communication technology, such as IEEE 802.11 WLAN, IEEE 802.15 WPAN, Ultra-Wide Band (UWB), Wi-Fi, ZigBee, Z-wave, Bluetooth, or the like. For example, the communication module may include a UWB sensor so as to detect the current indoor location of the cleaner  100 . 
     The cleaner  100  may include an inertial measurement unit (IMU) (not shown). The cleaner  100  may stabilize the traveling motion thereof based on information from the IMU. 
     The cleaner  100  includes the controller  20  for controlling the autonomous travel thereof. The controller  20  may receive a sensing signal from the sensing module and may control the traveling of the cleaner. The controller  20  may process the sensing signal of the obstacle sensor  16 . The controller  20  may process the sensing signal of the cliff sensor  17 . The controller  20  may process the sensing signal of the bumper  115 . The controller  20  may process the sensing signal of the UWB sensor and the sensing signal of the IMU. The controller  20  may process the signal of the input unit or the signal transmitted via the communication module. The controller  20  may control the water supply module  150 . The controller  20  may control a pump  155  so as to adjust the supplied amount of water. The amount of water that is supplied to the spin mop module  120  per unit time may be adjusted by controlling the pump  155 . In another example, the controller  20  may control a valve, which will be described later, in order to control whether to supply water. The controller  20  includes a printed circuit board (PCB)  20  disposed inside the body  110  (refer to  FIGS.  15 A to  16 B ). 
     The body  110  forms the external appearance of the cleaner. The body  110  includes a first unit  111 , which is disposed at the upper side of the first cleaning module  120 , and a second unit  112 , which is disposed at the upper side of the second cleaning module  130  (refer to  FIG.  5   ). The first unit  111  and the second unit  112  are formed integrally with each other. The bottom surface of the body  110 , which is formed between the first cleaning module  120  and the second cleaning module  130 , is recessed upwards so as to form a body gap  110   c . The body gap  110   c  may be disposed between the first unit  111  and the second unit  112 . The body gap  110   c  may be formed such that the left and right surfaces of the body  110  are recessed inwards. 
     The body  110  includes the bumper  115  for sensing external shocks. The bumper  115  is disposed at the upper side of the rotating plate  122  of the first cleaning module  120 . The bumper  115  is disposed at the front portion and the lateral portions of the body  110 . The bumper  115  may include a plurality of bumpers  115   a  and  115   b . The bumper  115   a  may be disposed at the front portion and the left portion of the left spin mop  120   a . The bumper  115   b  may be disposed at the front portion and the right portion of the right spin mop  120   b . 
     The cleaner  100  includes a contact unit  1151 , which is disposed at the edge of the body  110  so as to contact an external object. The contact unit  1151  is formed to extend from the front portion of the body  110  to the lateral portion of the body  110  so as to be bent along the body  110 . The cleaner  100  includes a bumper switch  1152 , which senses whether the contact unit  1151  is pressed by an external object. The bumper switch  1152  may be configured to be pressed by the contact unit  1151  when the contact unit  1151  is pushed. The bumper switch  1152  may include a first bumper switch  1152   a , which is disposed behind the front portion of the contact unit  1151 . The bumper switch  1152  may include a second bumper switch  1152   b , which is disposed inwards from the lateral portion of the contact unit  1151 . When the contact unit  1151  is pushed back, the first bumper switch  1152   a  is pressed. When the contact unit  1151  is pushed laterally, the second bumper switch  1152   b  is pressed. 
     The body  110  includes the case  11  and the base  13 , which form the external appearance of the cleaner. 
     The base  13  has therein an opening, in which a tilting frame  125  is disposed. The tilting frame  125  is connected to the base  13  via a tilting rotary shaft  126 . The tilting rotary shaft  126  is rotatably fixed to the base  13 . 
     The base  13  includes a limit for limiting the rotation range of the tilting frame  125 . The limit may include an upper-end limit  13   d  and a lower-end limit  13   f . 
     The base  13  includes the upper-end limit  13   d  for limiting the upward-rotation range of the tilting frame  125 . The left upper-end limit  13   d  may be disposed on the left of the left tilting frame  125 . The right upper-end limit  13   d  may be disposed on the right of the right tilting frame  125 . The left upper-end limit  13   d  is disposed so as to contact an upper-end-limit contact portion  125   f  of the left spin mop module  120 . The right upper-end limit  13   d  is disposed so as to contact an upper-end-limit contact portion  125   f  of the right spin mop module  120 . The upper-end-limit contact portion  125   f  may be disposed at the tilting frame  125 . When the cleaner  100  is normally placed on an external horizontal plane, the upper-end-limit contact portion  125   f  is in contact with the upper-end limit  13   d , and inclination angles A g   1  and A g   2  have the smallest values. 
     The base  13  includes the lower-end limit  13   f  for limiting the downward-rotation range of the tilting frame  125 . The lower-end limit  13   f  may be disposed at the inner surface of the base  13 . The lower-end limit  13   f  may be disposed at the lower side of the spin-drive unit  124 . The lower-end limit  13   f  is configured to contact a lower-end-limit contact portion  120   f  when the tilting frame  125  is maximally rotated in the downward direction. The lower-end-limit contact portion  120   f  may be disposed at the bottom surface of the spin-drive unit  124 . When the cleaner  100  is normally placed on an external horizontal plane, the lower-end-limit contact portion  120   f  is spaced apart from the lower-end limit  13   f . In the state in which there is no force on the bottom surfaces of the spin mops  120   a  and  120   b  to push the same upwards, the tilting frame  125  is rotated to a maximum angle, the lower-end-limit contact portion  120   f  comes into contact with the lower-end limit  13   f , and the inclination angles A g   1  and A g   2  have the largest values. 
     The base  13  includes a second support portion  13   b  for fixing an end of the elastic member  129 . When the tilting frame  125  is rotated, the elastic member  129  is elastically deformed or elastically restored by a first support portion  125   d  fixed to the tilting frame  125  and the second support portion  13   b  fixed to the base  13 . 
     The base  13  includes a tilting rotary shaft support portion  13   c  for supporting the tilting rotary shaft  126 . The tilting rotary shaft support portion  13   c  supports two opposite ends of the tilting rotary shaft  126 . 
     The base  13  may include a separate support member  13   a  for supporting the tilting frame  125 . The support member  13   a  may be formed as a part separate from the remaining portion of the base  13 . The support member  13   a  extends along the periphery of the opening formed in the bottom surface of the base  13 . The support member  13   a  has an opening formed in the center portion thereof, and the tilting frame  125  is disposed in the opening. 
     The support member  13   a  may include the second support portion  13   b . The support member  13   a  may include the tilting rotary shaft support portion  13   c . The support member  13   a  may include the upper-end limit  13   d . The support member  13   a  includes a support member fixing portion  13   e , which is coupled to the other portion of the base  13 . 
     Referring to  FIGS.  2  to  6 ,  9  to  11 , and  19   , the second cleaning module  130  is configured to contact the floor behind the first cleaning module  120 . The second cleaning module  130  is configured to perform mopping via contact with the floor along with the movement of the body  110 . The second cleaning module  130  is configured to perform dry mopping. 
     The second cleaning module  130  may include the rolling member  130   a , which rotates about a rotation axis Or that extends in the horizontal direction. In the present embodiment, the rotation axis Or extends in the leftward-and-rightward direction. However, in another embodiment, the rotation axis Or may extend in the forward-and-backward direction, or may extend in a direction intermediate to the forward-and-backward direction and the leftward-and-rightward direction. Accordingly, a force that moves the body  110  in the horizontal direction (the direction perpendicular to the rotation axis Or) may be applied to the body  110  by rotation of the rolling member  130   a . Since the moving force generated by the rolling member  130   a  is additionally applied to the body  110  in addition to the moving force applied to the body  110  by the first cleaning module  120 , it is possible to realize various types of traveling motion of the cleaner  100 . 
     In the present embodiment, the second cleaning module  130  includes the rolling member  130   a , which rotates about the rotation axis Or, which extends in the leftward-and-rightward direction. The rolling member  130   a  may rotate about the rotation axis Or, which extends in the direction parallel to the direction in which the left spin mop  120   a  and the right spin mop  120   b  are arranged. Accordingly, a force that moves the body  110  in the forward-and-backward direction may be applied to the body  110  by rotation of the rolling member  130   a . Since the moving force generated by the rolling member  130   a  is additionally applied to the body  110  in the forward-and-backward direction in addition to the moving force applied to the body  110  by the first cleaning module  120 , it is possible to efficiently realize various types of traveling motion of the cleaner  100 . A detailed explanation of the various types of traveling motion will be made later. 
     Referring to  FIGS.  6  and  10   , when viewed from the right side, the clockwise rotation direction of the rolling member  130   a  is defined as a third forward direction  w   3   f , and the counterclockwise rotation direction of the rolling member  130   a  is defined as a third reverse direction  w   3   r . 
     When the cleaner  100  moves forwards, the rolling member  130   a  follows the first cleaning module  120 , and performs an operation of mopping the floor that has been cleaned by the first cleaning module  120 . The rolling member  130   a  is configured to perform a dry mopping operation so as to remove moisture from the floor that has been wet-mopped by the left spin mop  120   a  and the right spin mop  120   b . In the present embodiment, the second cleaning module  130  includes one rolling member  130   a . However, in another embodiment, the second cleaning module  130  may include a plurality of rolling members. Each of the rolling members may be configured to rotate about a corresponding one of the rotation axes that are arranged parallel to each other. 
     The second cleaning module  130  includes the mop unit  131  or the brush. A portion of the weight of the body  110  may be transmitted to the floor via the mop unit  131  or the brush. The mop unit  131  or the brush is arranged to surround the periphery of a rotary member  132 . The mop unit  131  or the brush is arranged along the periphery about the rotation axis Or. The mop unit  131  or the brush may be fixedly coupled to the rotary member  132 , or may be separably coupled to the rotary member  132 . 
     In the present embodiment, the second cleaning module  130  includes the mop unit  131 . A portion of the weight of the body  110  may be transmitted to the floor via the mop unit  131 . The mop unit  131  is arranged to surround the periphery of the rotary member  132 . The mop unit  131  is arranged along the periphery about the rotation axis Or. The mop unit  131  may be fixedly coupled to the rotary member  132 , or may be separably coupled to the rotary member  132 . 
     The second cleaning module  130  includes the rotary member  132 , which is configured so as to rotate. 
     The mop unit  131  or the brush of the rolling member  130   a  is fixed to the rotary member  132 . The rotary member  132  may rotate together with the mop unit  131  or the brush. 
     In the present embodiment, the mop unit  131  of the rolling member  130   a  is fixed to the rotary member  132 . The rotary member  132  may rotate together with the mop unit  131 . 
     The rotary member  132  is rotated by receiving drive force from a rolling drive unit  137 . The rotary member  132  rotates about the rotation axis Or. 
     The rotary member  132  is formed in a cylindrical shape. The rotary member  132  is formed so as to be elongated in the direction in which the rotation axis Or extends. The rotary member  132  has therein a hollow portion  132   s . The mop unit  131  is fixed to the outer circumferential surface of the rotary member  132 . 
     The second cleaning module  130  includes a first shaft member  134 , which is disposed at one end portion of the rotary member  132 . The second cleaning module  130  includes a second shaft member  135 , which is disposed at the opposite end portion of the rotary member  132 . The first shaft member  134  and the second shaft member  135  are respectively disposed at the two opposite ends of the second cleaning module  130  in the direction in which the rotation axis Or extends. In the present embodiment, the first shaft member  134  is disposed at the right end portion of the rotary member  132 , and the second shaft member  135  is disposed at the left end portion of the rotary member  132 . The one end portion of the rotary member  132  is recessed in the inward direction, and the first shaft member  134  is disposed in the recessed portion in the one end portion of the rotary member  132 . The opposite end portion of the rotary member  132  is recessed in the inward direction, and the second shaft member  135  is disposed in the recessed portion of the opposite end portion of the rotary member  132 . 
     The first shaft member  134  connects the one end portion of the rotary member  132  and the body  110  to each other. The first shaft member  134  is fixedly connected to the rotary member  132 . The first shaft member  134  is formed to protrude in the direction in which the rotation axis Or extends. In the present embodiment, the first shaft member  134  protrudes to the right. The first shaft member  134  is inserted into a recess formed in a drive force transmission unit  137   a  so as to rotate simultaneously when the drive force transmission unit  137   a  rotates. The cross-section of the first shaft member  134  that is perpendicular to the rotary shaft Or has a shape other than a circular shape (for example, a polygonal shape). The drive force transmission unit  137   a  has therein a recess formed in a shape that corresponds to the shape of the first shaft member  134 . 
     The second shaft member  135  connects the opposite end portion of the rotary member  132  and the body  110  to each other. The second shaft member  135  is rotatably connected to the rotary member  132 . The second shaft member  135  is formed to protrude in the direction in which the rotation axis Or extends. In the present embodiment, the second shaft member  135  protrudes to the left. The second shaft member  135  is fixedly inserted into recesses formed in the body  110  and a coupler  117 . When the first shaft member  134  is rotated by the drive force transmission unit  137   a , the rotary member  132  and the mop unit  131  rotate together with the first shaft member  134 . The rotary member  132  rotates relative to the fixed second shaft member  135 . A bearing may be disposed between the second shaft member  135  and the rotary member  132 . The cross-section of the second shaft member  135  that is perpendicular to the rotary shaft Or has a shape other than a circular shape (for example, a polygonal shape). The body  110  and/or the coupler  117  have therein recesses formed in a shape that corresponds to the shape of the second shaft member  135 . 
     The second cleaning module  130  includes the rolling drive unit  137  that provides drive force for rotating the rolling member  130   a . The rolling drive unit  137  provides drive force for rotating the rotary member  132 . The rolling drive unit  137  includes a motor  137   d . The motor  137   d  is disposed in the body  110 . The rolling drive unit  137  includes a gear assembly  137   c  for transmitting torque of the motor  137   d . The gear assembly  137   c  includes a plurality of gears that mesh with each other and rotate. For example, the gears may include a driving gear, which rotates together with the shaft of the motor  137   d , and a driven gear, which meshes with the driving gear and rotates. The driven gear may be provided in a plural number, and the plurality of driven gears may mesh with each other and may rotate. The rolling drive unit  137  may include a shaft  137   b , which rotates together with any one of the driven gears. The rolling drive unit  137  may include the drive force transmission unit  137   a  that transmits rotational force to the first shaft member  134 . The shaft  137   b  transmits the rotational force of the one of the driven gears to the drive force transmission unit  137   a . The drive force transmission unit  137   a  has therein a recess, into which the first shaft member  134  is inserted. The shaft  137   b , the drive force transmission unit  137   a  and the first shaft member  134  rotate together with each other. 
     The cleaner  100  may include the coupler  117 , which is separably coupled to the body  110 . The coupler  117  is disposed at the base  13 . The coupler  117  supports the lower end of the second shaft member  135 . The second shaft member  135  is supported by the base  13 . The coupler  117  may have therein a recess, into which the second shaft member  135  is inserted. The rotary member  132  and the mop unit  131  may be removed from or coupled to the body  110  using the coupler  117 . For example, in the state in which the coupler  117  is removed, a user is capable of easily drawing the first shaft member  134  out of the drive force transmission unit  137   a  after pulling the end portion of the rotary member  132 , at which the second shaft member  135  is disposed, out of the body  110 . Conversely, in the state in which the coupler  117  is removed, the end portion of the first shaft member  134  may first be inserted into the recess in the drive force transmission unit  137   a , and subsequently the second shaft member  135  and the coupler  117  may be inserted into the body  110 . In order to maintain the coupling of the rotary member  132  to the body  110 , a user may fix the coupler  117  to the body  110 . Further, in order to remove the rotary member  132  from the body  110 , a user may remove the coupler  117  from the body  110 . 
     Referring to  FIGS.  1  to  6 ,  8 ,  10 , and  12  to  23   , the first cleaning module  120  includes the left spin mop  120   a  and the right spin mop  120   b , which are configured to contact the floor while rotating clockwise or counterclockwise when viewed from the upper side. The first cleaning module  120  is configured to perform mopping via rotation of the left spin mop  120   a  and the right spin mop  120   b . 
     Among the components of the first cleaning module  120 , a component in which “left” is affixed to the front of the name thereof is a component for operating the left spin mop  120   a , and a component in which “right” is affixed to the front of the name thereof is a component for operating the right spin mop  120   b . In a description related to the components of the first cleaning module  120 , when it is unnecessary to distinguish “left” and “right” from each other, the corresponding description may be applied to both “left” and “right”. 
     Referring to  FIG.  6   , the point at which the rotation axis of the left spin mop  120   a  and the bottom surface of the left spin mop  120   a  meet is defined as a rotation center Osa of the left spin mop  120   a . The point at which the rotation axis of the right spin mop  120   b  and the bottom surface of the right spin mop  120   b  meet is defined as a rotation center Osb of the right spin mop  120   b . When viewed from the lower side, the clockwise rotation direction of the left spin mop  120   a  is defined as a first forward direction  w   1   f , and the counterclockwise rotation direction of the left spin mop  120   a  is defined as a first reverse direction  w   1   r . When viewed from the lower side, the counterclockwise rotation direction of the right spin mop  120   b  is defined as a second forward direction  w   2   f , and the clockwise rotation direction of the right spin mop  120   b  is defined as a second reverse direction  w   2   r . 
     Referring to  FIG.  6   , when the left spin mop  120   a  rotates, the point Pla on the bottom surface of the left spin mop  120   a  that receives the largest frictional force from the floor is located to the left of the rotation center Osa of the left spin mop  120   a . The largest frictional force may be generated at the point Pla by transmitting a larger load from the point Pla to the floor than from any other point on the bottom surface of the left spin mop  120   a . In the present embodiment, the point Pla is located exactly to the left of the rotation center Osa. However, in another embodiment, the point Pla may be located to the left and in front of the rotation center Osa or to the left and behind the rotation center Osa. 
     Referring to  FIG.  6   , when the right spin mop  120   b  rotates, the point Plb on the bottom surface of the right spin mop  120   b  that receives the largest frictional force from the floor is located to the right of the rotation center Osb of the right spin mop  120   b . The largest frictional force may be generated at the point Plb by transmitting a larger load from the point Plb to the floor than from any other point on the bottom surface of the right spin mop  120   b . In the present embodiment, the point Plb is located exactly to the right of the rotation center Osb. However, in another embodiment, the point Plb may be located to the right and in front of the rotation center Osb or to the right and behind the rotation center Osb. 
     The point Pla and the point Plb are located at positions that are bilaterally symmetrical to each other. 
     In order to make the point Pla receive larger frictional force from the floor than any other point on the bottom surface of the left spin mop  120   a  (or in order to make the point Plb receive larger frictional force from the floor than any other point on the bottom surface of the right spin mop  120   b ), configuration may be variously made according to the embodiments set forth below. 
     In one embodiment illustrated in  FIG.  3 A , the left spin mop  120   a  may be arranged such that the bottom surface thereof is inclined downwards in the direction from the rotation center Osa to the point Pla. In this case, the point Pla becomes the lowest point Pla on the bottom surface of the left spin mop  120   a . In this case, the angle that the bottom surface I 1  of the left spin mop  120   a  makes with an imaginary horizontal plane H and the angle that the bottom surface I 2  of the right spin mop  120   b  makes with the imaginary horizontal plane H are defined as the inclination angles A g   1  and A g   2 . The angle that the bottom surface I 1  of the left spin mop  120   a  makes with the external horizontal plane H is the inclination angle A g   1 , and the angle that the bottom surface I 2  of the right spin mop  120   b  makes with the external horizontal plane H is the inclination angle A g   2 . These two inclination angles A g   1  and A g   2  may be the same as each other. 
     In another embodiment illustrated in  FIG.  3 B , the left spin mop  120   a  may be arranged such that the bottom surface thereof lies horizontally. The embodiment may be configured such that a moment is applied to the left spin mop  120   a  using an elastic member. The moment applied to the left spin mop  120   a  is a clockwise moment when viewed from the front side. In this case, even when the left spin mop  120   a  lies horizontally with respect to the external horizontal plane H, the point Pla comes into strongest contact with the external horizontal plane H, thereby generating the largest frictional force. A detailed description of a first embodiment and a second embodiment for realizing the above characteristics will now be made. 
     In the first embodiment, the first cleaning module  120  is disposed at a tilting frame  125 , which will be described later. The moment may be applied to the first cleaning module  120  by the elastic force of an elastic member  129 , which will be described later. As shown in  FIG.  3 B , in the state in which the upper-end-limit contact portion  125   f  is in contact with the upper-end limit  13   d , the bottom surfaces of the spin mops  120   a  and  120   b  are arranged parallel to the horizontal plane H. In particular, when the left spin mop  120   a  lies horizontally, the elastic member  129  is elastically deformed to the maximum extent. When the point Pla of the left spin mop  120   a  is located at a lower position than any other point, the extent of elastic deformation of the elastic member  129  is reduced. 
     In the second embodiment, a plurality of springs (not shown) may be arranged on the top surface of a lower rotating plate (not shown), which fixes the bottom surface of the left spin mop  120   a , in the rotation direction about the rotation axis. In this case, an upper rotating plate (not shown), which supports the upper ends of the springs, may be arranged at a downward incline in the direction from the rotation center Osa to the point Pla. When the upper rotating plate rotates, the respective springs also rotate and undergo elastic compression and elastic restoration repeatedly. At this time, among the springs, the spring that is disposed near the point Pla on the basis of the rotation center Osa is compressed to the largest extent. Accordingly, the point Pla receives larger frictional force from the floor than any other point on the bottom surface of the left spin mop  120   a . 
     In order to make the point Plb receive larger frictional force from the floor than any other point on the bottom surface of the right spin mop  120   b , the above-described embodiment, the first embodiment, and the second embodiment may be applied in the same manner by those skilled in the art. Hereinafter, a description will be made with reference to the above-described embodiment (refer to  FIG.  3 A ). 
     The bottom surface of the left spin mop  120   a  and the bottom surface of the right spin mop  120   b  are each arranged at an incline. The inclination angle A g   1  of the left spin mop  120   a  and the inclination angle A g   2  of the right spin mop  120   b  are acute angles. In the present embodiment, the inclination angles A g   1  and A g   2  respectively range from about 3 to 6 degrees. The inclination angles A g   1  and A g   2  may be set to be small such that the points Pla and Plb receive the largest frictional force and such that the entire bottom area of the mop unit  121  contacts the floor via rotation of the left spin mop  120   a  and the right spin mop  120   b . 
     The bottom surface of the left spin mop  120   a  extends at a downward incline in the leftward direction. The bottom surface of the right spin mop  120   b  extends at a downward incline in the rightward direction. Referring to  FIG.  6   , the bottom surface of the left spin mop  120   a  has the lowest point Pla located at the left portion thereof. The bottom surface of the left spin mop  120   a  has the highest point Pha located at the right portion thereof. The bottom surface of the right spin mop  120   b  has the lowest point Plb located at the right portion thereof. The bottom surface of the right spin mop  120   b  has the highest point Phb located at the left portion thereof. 
     Referring to  FIG.  6   , the movement of the cleaner  100  is implemented by the frictional force that the first cleaning module  120  and/or the second cleaning module  130  generate with the floor. 
     The first cleaning module  120  may generate forward-movement frictional force for moving the body  110  forwards or backward-movement frictional force for moving the body  110  backwards. The first cleaning module  120  may generate leftward-moment frictional force for turning the body  110  to the left or rightward-moment frictional force for turning the body  110  to the right. The first cleaning module  120  may generate frictional force that is a combination of any one of the forward-movement frictional force and the backward-movement frictional force and any one of the leftward-moment frictional force and the rightward-moment frictional force. 
     The second cleaning module  130  may generate forward-movement frictional force for moving the body  110  forwards or backward-movement frictional force for moving the body  110  backwards. 
     In order to generate the forward-movement frictional force, the first cleaning module  120  may rotate the left spin mop  120   a  at a predetermined number of revolutions per minute (rpm) R 1  in the first forward direction  w   1   f , and may rotate the right spin mop  120   b  at the predetermined rpm R 1  in the second forward direction  w   2   f . 
     In order to generate the forward-movement frictional force, the second cleaning module  130  may rotate the rolling member  130   a  in the third forward direction  w   3   f . 
     In order to generate the backward-movement frictional force, the first cleaning module  120  may rotate the left spin mop  120   a  at a predetermined rpm R 2  in the first reverse direction  w   1   r , and may rotate the right spin mop  120   b  at the predetermined rpm R 2  in the second reverse direction  w   2   r . 
     In order to generate the backward-movement frictional force, the second cleaning module  130  may rotate the rolling member  130   a  in the third reverse direction  w   3   r . 
     In order for the first cleaning module  120  to generate the rightward-moment frictional force, the left spin mop  120   a  may be rotated at a predetermined rpm R 3  in the first forward direction  w   1   f , and the right spin mop  120   b  may be operated as follows: (i) it may be rotated in the second reverse direction  w   2   r ; (ii) it may be stopped without rotation; or (iii) it may be rotated in the second forward direction  w   2   f  at a predetermined rpm R 4 , which is lower than the rpm R 3 . 
     In order for the first cleaning module  120  to generate the leftward-moment frictional force, the right spin mop  120   b  may be rotated at a predetermined rpm R 5  in the second forward direction  w   2   f , and the left spin mop  120   a  may be operated as follows: (i) it may be rotated in the first reverse direction  w   1   r ; (ii) it may be stopped without rotation; or (iii) it may be rotated in the first forward direction  w   1   f  at a predetermined rpm R 6 , which is lower than the rpm R 5 . 
     It is possible for the body  110  to move or to stay in place via a combination of the frictional force generated by the first cleaning module  120  and the frictional force generated by the second cleaning module  130 . 
     In order for the cleaner  100  to move straight forwards, both the first cleaning module  120  and the second cleaning module  130  may generate the forward-movement frictional force. In another example, any one of the first cleaning module  120  and the second cleaning module  130  may generate the forward-movement frictional force, and the remaining one thereof may remain stationary without rotating. In a further example, any one of the first cleaning module  120  and the second cleaning module  130  may generate relatively large forward-movement frictional force, and the remaining one thereof may generate relatively small backward-movement frictional force. 
     In order for the cleaner  100  to move straight backwards, both the first cleaning module  120  and the second cleaning module  130  may generate the backward-movement frictional force. In another example, any one of the first cleaning module  120  and the second cleaning module  130  may generate the backward-movement frictional force, and the remaining one thereof may remain stationary without rotating. In a further example, any one of the first cleaning module  120  and the second cleaning module  130  may generate relatively large backward-movement frictional force, and the remaining one thereof may generate relatively small forward-movement frictional force. 
     In order to turn the cleaner  100  to the right, the first cleaning module  120  may generate the rightward-moment frictional force, and the rolling member  130   a  may be operated as follows: (i) it may be rotated in the third forward direction  w   3   f , (ii) it may be stopped without rotation, or (iii) it may be rotated in the third reverse direction  w   3   r . 
     In order to turn the cleaner  100  to the left, the first cleaning module  120  may generate the leftward-moment frictional force, and the rolling member  130   a  may be operated as follows: (i) it may be rotated in the third forward direction  w   3   f , (ii) it may be stopped without rotation; or (iii) it may be rotated in the third reverse direction  w   3   r . 
     In order for the cleaner  100  to stay in place, both the first cleaning module  120  and the second cleaning module  130  may remain stationary without rotating. In another example, any one of the first cleaning module  120  and the second cleaning module  130  may generate forward-movement frictional force, and the remaining one thereof may generate backward-movement frictional force that has the same magnitude as the forward-movement frictional force. In particular, in the latter case, while the body  110  stays in place, the first cleaning module  120  and the second cleaning module  130  may respectively rotate and perform an operation of mopping a certain area of the floor. 
     According to the above-described processes of controlling the movement of the body  110 , the direction in which the rolling member  130   a  rotates can be changed. Accordingly, it is possible to combine any one of the forward-movement frictional force and the backward-movement frictional force, which are generated by the rolling member  130   a , with the frictional force generated by the first cleaning module  120 , thereby facilitating various types of movement of the cleaner  100 . Specifically, it is possible to increase the maximum speed of the cleaner  100  in the forward-and-backward direction, to enable the cleaner  100  to be turned to the right or to the left with various turn radii, to enable the cleaner  100  to be turned to the right or to the left while traveling backwards, and to enable the cleaner  100  to perform a mopping operation via rotation while the body  110  stays in place. 
     While the first cleaning module  120  performs a predetermined constant rotation operation (an operation of generating the forward-movement frictional force, the backward-movement frictional force, the leftward-moment frictional force, or the rightward-moment frictional force), the rolling member  130   a  may perform two or more different rotation operations. While the first cleaning module performs a predetermined constant rotation operation, the rolling member  130   a  may be controlled to rotate in the third forward direction  w   3   f . While the first cleaning module performs a predetermined constant rotation operation, the rolling member  130   a  may be controlled to rotate in the third reverse direction  w   3   r . While the first cleaning module performs a predetermined constant rotation operation, the rolling member  130   a  may be controlled to remain stationary without rotating. While the first cleaning module performs a predetermined constant rotation operation, the rolling member  130   a  may be controlled to rotate in the third forward direction  w   3   f  at one selected from among two or more predetermined RPMs. While the first cleaning module performs a predetermined constant rotation operation, the rolling member  130   a  may be controlled to rotate in the third reverse direction  w   3   r  at one selected from among two or more predetermined RPMs. As such, it is possible to realize various traveling routes and traveling speeds of the cleaner  100 . 
     The contact area between the rolling member  130   a  and the floor may be formed to be elongated in the leftward-and-rightward direction. The right end of the left spin mop  120   a  and the left end of the right spin mop  120   b  may be spaced a predetermined distance apart from each other. When viewed from the front side, the contact area between the rolling member  130   a  and the floor may overlap the entire area of the gap between the left spin mop  120   a  and the right spin mop  120   b . The gap between the left spin mop  120   a  and the right spin mop  120   b  is a portion of the first cleaning module  120  that may not perform mopping sufficiently well. When the cleaner  100  moves in the forward-and-backward direction, the rolling member  130   a  performs an operation of mopping an area of the floor that corresponds to the gap, thereby supplementing the mopping operation of the first cleaning module  120 . 
     The contact area between the rolling member  130   a  and the floor may be formed to be elongated in the leftward-and-rightward direction. When viewed from the front side, the contact area between the rolling member  130   a  and the floor may overlap the entire area between the rotation center Osa of the left spin mop  120   a  and the rotation center Osb of the right spin mop  120   b . The right side of the rotation center Osa of the left spin mop  120   a  and the left side of the rotation center Osb of the right spin mop  120   b  are portions to which relatively low frictional force is applied, and thus may not perform mopping sufficiently well, compared to the left side of the rotation center Osa of the left spin mop  120   a  and the right side of the rotation center Osb of the right spin mop  120   b . When the cleaner  100  moves in the forward-and-backward direction, the rolling member  130   a  performs an operation of mopping an area of the floor located between the rotation center Osa of the left spin mop  120   a  and the rotation center Osb of the right spin mop  120   b , thereby supplementing the mopping operation of the first cleaning module  120 . 
     Referring to  FIGS.  20  to  23   , the first cleaning module  120  includes the rotating plate  122 , which is rotatably provided at the lower side of the body  110 . The rotating plate  122  may be formed by a circular plate member. The mop unit  121  is fixed to the bottom surface of the rotating plate  122 . The spin shaft  128  is fixed to the center portion of the rotating plate  122 . 
     The first cleaning module  120  includes the left rotating plate  122 , which fixes the mop unit  121  of the left spin mop  120   a , and the right rotating plate  122 , which fixes the mop unit  121  of the right spin mop  120   b . 
     The rotating plate  122  includes a mop-fixing member  122   c , which fixes the mop unit  121 . The mop unit  121  may be separably fixed to the mop-fixing member  122   c . The mop-fixing member  122   c  may be a piece of Velcro tape or the like disposed at the lower side of the rotating plate  122 . The mop-fixing member  122   c  may be a hook or the like disposed on the edge of the rotating plate  122 . 
     The rotating plate  122  includes a slope  122   d , which is disposed on the lower end of the spin shaft  128  so that the water inside a water supply space Sw moves downwards along the slope  122   d  due to the force of gravity. The slope  122   d  is formed along the periphery of the lower end of the spin shaft  128 . The slope  122   d  is downwardly inclined in the centrifugal direction XO. The entire slope  122   d  may be formed in a truncated cone shape. The lower end of the spin shaft  128  is fixed to the upper center of the slope  122   d . 
     A water supply hole  122   a  vertically penetrates the rotating plate  122 . The water supply hole  122   a  connects the water supply space Sw to the lower side of the rotating plate  122 . The water inside the water supply space Sw moves to the lower side of the rotating plate  122  through the water supply hole  122   a . The water inside the water supply space Sw moves to the mop unit  121  through the water supply hole  122   a . The water supply hole  122   a  is located in the center portion of the rotating plate  122 . The water supply hole  122   a  is located so as to avoid the spin shaft  128 . 
     The rotating plate  122  may be provided with a plurality of water supply holes  122   a  therein. A connecting portion  122   b  is disposed between the respective water supply holes  122   a . The connecting portion  122   b  interconnects the portion of the rotating plate  122  in the centrifugal direction XO and the portion of the rotating plate  122  in the counter-centrifugal direction XI on the basis of the water supply hole  122   a . 
     The plurality of water supply holes  122   a  may be spaced apart from each other in the peripheral direction of the spin shaft  128 . The water supply holes  122   a  may be spaced apart from each other by a constant distance. Accordingly, when the rotating plate  122  rotates, water is supplied evenly to the mop unit  121  in all directions on the basis of the spin shaft  128 . 
     The water supply holes  122   a  are disposed in the centrifugal direction XO in the lower end portion of the slope  122   d . Accordingly, the water, which has moved downwards along the slope  122   d  due to the force of gravity and centrifugal force, may be introduced into the water supply holes  122   a . The side surface of the water supply hole  122   a  in the counter-centrifugal direction XI may be aligned with the lower end portion of the slope  122   d . 
     The side surface Qh of the water supply hole  122   a  in the centrifugal direction XO and the side surface Qw of the water supply reservoir  123  in the counter-centrifugal direction XI are provided so as to extend vertically. The side surface Qh of the water supply hole  122   a  in the centrifugal direction XO and the side surface Qw of the water supply reservoir  123  in the counter-centrifugal direction XI are disposed on substantially the same vertical line. Accordingly, the water, which is forced to move in the centrifugal direction XO by the centrifugal force, is finally introduced into the water supply hole  122   a . 
     The side surface Qh of the water supply hole  122   a  in the centrifugal direction XO forms a cylindrically curved surface. The side surface Qw of the water supply reservoir  123  in the counter-centrifugal direction XI forms a cylindrically curved surface. Both the side surface Qh of the water supply hole  122   a  in the centrifugal direction XO and the side surface Qw of the water supply reservoir  123  in the counter-centrifugal direction XI form a cylindrically curved surface. 
     The first cleaning module  120  includes the mop unit  121 , which is configured so as to be brought into contact with the floor. The mop unit  121  is coupled to the lower side of the rotating plate  122 . The mop unit  121  is disposed on each of the bottom surface of the left spin mop  120   a  and the bottom surface of the right spin mop  120   b . The mop unit  121  may be fixedly disposed on the rotating plate  122 , or may be disposed in a manner such that it is replaceable. The mop unit  121  may be separably fixed to the rotating plate  122  via a piece of Velcro tape, a hook, or the like. The mop unit  121  may be configured as a mop alone, or may include a mop and a spacer (not shown). The mop serves to perform mopping in contact with the floor. The spacer may be disposed between the rotating plate  122  and the mop and may serve to adjust the position of the mop. The spacer may be separably fixed to the rotating plate  122 , and the mop may be separably fixed to the spacer. Needless to say, the mop  121   a  may be separably fixed to the rotating plate  122  without the spacer. 
     Referring to  FIGS.  8 ,  10 , and  18  to  23   , the first cleaning module  120  includes the spin shaft  128 , which is configured to rotate the rotating plate  122 . The spin shaft  128  is fixed to the rotating plate  122  and transmits the torque of the spin-drive unit  124  to the rotating plate  122 . The spin shaft  128  is connected to the upper side of the rotating plate  122 . The spin shaft  128  is disposed on the upper center of the rotating plate  122 . The spin shaft  128  is fixed to the rotation center Osa or Osb of the rotating plate  122 . The spin shaft  128  includes a gear-fixing portion  128   a  for fixing a gear  127   b . The gear-fixing portion  128   a  is disposed on the upper end of the spin shaft  128 . 
     The first cleaning module  120  includes a left spin shaft  128 , fixed to the left rotating plate  122  to rotate the left rotating plate  122 , and a right spin shaft  128 , fixed to the right rotating plate  122  to rotate the right rotating plate  122 . 
     The spin shaft  128  extends perpendicular to the rotating plate  122 . The left spin shaft  128  is disposed perpendicular to the bottom surface of the left spin mop  120   a , and the right spin shaft  128  is disposed perpendicular to the bottom surface of the right spin mop  120   b . In an embodiment in which the bottom surface of the spin mop  120   a  or  120   b  is inclined relative to the horizontal plane, the spin shaft  128  is tilted relative to the vertical axis. The upper end of the spin shaft  128  is tilted to one side relative to the lower end. The upper end of the left spin shaft  128  is tilted leftward relative to the lower end. The upper end of the right spin shaft  128  is tilted rightward relative to the lower end. 
     The tilting angle of the spin shaft  128  relative to the vertical axis may be changed depending on the rotation of the tilting frame  125  about the tilting rotary shaft  126 . The spin shaft  128  is rotatably coupled to the tilting frame  125  so as to be integrally tilted with the tilting frame  125 . When the tilting frame  125  is tilted, the spin-drive unit  124 , the driving transmission unit  127 , the spin shaft  128 , the rotating plate  122 , the water supply reservoir  123 , and the mop unit  121  are integrally tilted. 
     The first cleaning module  120  includes the water supply reservoir  123 , which is disposed at the upper side of the rotating plate  122  so as to accommodate water therein. The water supply reservoir  123  defines the water supply space Sw in which water is accommodated. The water supply reservoir  123  surrounds the periphery of the spin shaft  128  and is spaced apart from the spin shaft  128  so as to define the water supply space Sw therebetween. The water supply reservoir  123  allows the water supplied to the upper side of the rotating plate  122  to be collected in the water supply space Sw until the water passes through the water supply hole  122   a . The water supply space Sw is disposed at the upper side of the center portion of the rotating plate  122 . The water supply space Sw has a cylindrical volume overall. The upper side of the water supply space Sw is open so that the water is introduced into the water supply space Sw through the upper side of the water supply space Sw. 
     The water supply reservoir  123  protrudes upwards from the rotating plate  122 . The water supply reservoir  123  extends in the peripheral direction of the spin shaft  128 . The water supply reservoir  123  may be formed by a ring-shaped rib. The water supply hole  122   a  is located in the inner lower surface of the water supply reservoir  123 . The water supply reservoir  123  is spaced apart from the spin shaft  128 . 
     The side surface Qw of the water supply reservoir  123  in the counter-centrifugal direction XI faces the outer peripheral surface of the spin shaft  128 . The side surface Qw is spaced apart from the spin shaft  128 . The side surface Qw is smoothly connected to the side surface Qh in the vertical direction. The lower end of the water supply reservoir  123  is fixed to the rotating plate  122 . The water supply reservoir  123  has a free upper end. 
     The first cleaning module  120  includes the spin-drive unit  124 , which provides drive force for rotating the spin mop  120   a  or  120   b . The first cleaning module  120  includes a left spin-drive unit  124 , which provides power required for rotating the left spin shaft  128 , and a right spin-drive unit  124 , which provides power required for rotating the right spin shaft  128 . The left spin-drive unit  124  provides drive force required for rotating the left spin shaft  128 . The right spin-drive unit  124  provides drive force required for rotating the right spin shaft  128 . 
     The first cleaning module  120  includes the driving transmission unit  127 , which transmits the torque of the spin-drive unit  124  to the spin shaft  128 . The driving transmission unit  127  may include a plurality of gears and/or a belt, for example. 
     In the present embodiment, the driving transmission unit  127  includes a first gear  127   a  fixed to a rotating shaft of the spin-drive unit  124 . The first gear  127   a  may be a worm gear. The driving transmission unit  127  may include a second gear  127   b , which is engaged and rotated with the first gear  127   a . The second gear  127   b  may be a spur gear. The second gear  127   b  is fixed to the spin shaft  128  so as to allow the spin shaft  128  to be rotated simultaneously with the rotation of the second gear  127   b . 
     The first cleaning module  120  includes the tilting frame  125 , which is disposed on the body  110  so as to be tiltable within a predetermined angular range. The inclination angle A g   1  or A g   2  of the tilting frame  125  may be changed depending on the state of the floor. The tilting frame  125  may perform a suspension function for the spin mop  120   a  or  120   b  (a function of supporting the weight and alleviating vertical vibration). The tilting frame  125  is tiltably supported by the base  13 . The tilting frame  125  rotatably supports the spin shaft  128 . 
     The first cleaning module  120  includes the left tilting frame  125 , which supports the left spin shaft  128 . The left tilting frame  125  is rotatable within a predetermined range about a left tilting rotary shaft  126 . 
     The first cleaning module  120  includes the right tilting frame  125 , which supports the right spin shaft  128 . The right tilting frame  125  is rotatable within a predetermined range about a right tilting rotary shaft  126 . 
     For example, when the left spin mop  120   a  is brought into contact with a recessed portion in the floor, the inclination angle A g   1  of the left spin mop  120   a  may be increased within a predetermined range by the left tilting frame  125 . When the right spin mop  120   b  is brought into contact with a recessed portion in the floor, the inclination angle A g   2  of the right spin mop  120   b  may be increased within a predetermined range by the right tilting frame  125 . 
     The tilting frame  125  includes a frame base  125   a  defining the bottom surface thereof. The spin shaft  128  is disposed so as to vertically penetrate the frame base  125   a . The frame base  125   a  may be configured by a plate, which forms a vertical thickness. The tilting rotary shaft  126  rotatably interconnects the base  13  and the frame base  125   a . 
     The cleaner  100  includes a water supply cabinet  125   b , which is disposed at the upper side of the water supply reservoir  123 . The tilting frame  125  may include the water supply cabinet  125   b . 
     The water supply cabinet  125   b  may accommodate the spin shaft  128  therein. The water supply cabinet  125   b  may be disposed at the lower side of the body  110 . The water supply cabinet  125   b  may cover the upper side of the water supply reservoir  123 . When viewed from the upper side, the water supply cabinet  125   b  may cover the upper side of the water supply reservoir  123 . The water supply cabinet  125   b  defines a space recessed upwards from the lower side of the body  110  so as to accommodate the upper end portion of the water supply reservoir  123 . The water supply cabinet  125   b  is fixed to the frame base  125   a . The water supply cabinet  125   b  defines the space recessed upwards from the bottom surface of the frame base  125   a . The water is introduced into the space defined by the water supply cabinet  125   b  through a water feeder  125   c . The water supply cabinet  125   b  may minimize scattering of water, and thus all the water may be introduced into the water supply reservoir  123 . 
     The water supply cabinet  125   b  includes a spin-shaft support portion  125   b   1 , which rotatably supports the spin shaft  128 . A bearing B may be provided between the spin-shaft support portion  125   b   1  and the spin shaft  128 . The bearing B may include a first bearing B 1  disposed at the lower side, and a second bearing B 2  disposed at the upper side. 
     The lower end portion of the spin-shaft support portion  125   b   1  is inserted into the water supply space Sw of the water supply reservoir  123 . The inner peripheral surface of the spin-shaft support portion  125   b   1  supports the spin shaft  128 . The outer peripheral surface of the spin-shaft support portion  125   b   1  faces the inner peripheral surface Qw of the water supply reservoir  123 . Accordingly, the spin-shaft support portion  125   b   1  may stably support the spin shaft  128 , and may guide water to be easily collected in the water supply space Sw. 
     The lower end portion of the spin-shaft support portion  125   b   1  is disposed between the spin shaft  128  and the inner peripheral surface Qw of the water supply reservoir  123 . The outer peripheral surface of the lower end portion of the spin-shaft support portion  125   b   1  is spaced apart from the inner peripheral surface Qw of the water supply reservoir  123   so as to define the water supply space Sw therebetween. The slope  122   d  is disposed on the lower end portion of the spin-shaft support portion  125   b   1 . 
     The water supply cabinet  125   b  includes partitions  125   b   2  and  125   b   3 , which protrude from the spin-shaft support portion  125   b   1 . The partitions  125   b   2  and  125   b   3  cover the upper end portion of the water supply reservoir  123 . The partitions  125   b   2  and  125   b   3  cover the upper end and the outer peripheral surface of the water supply reservoir  123 . The partitions  125   b   2  and  125   b   3  are disposed in the centrifugal direction XO of the spin-shaft support portion  125   b   1 . The partitions  125   b   2  and  125   b   3  are fixed to and supported by the frame base  125   a . The partitions  125   b   2  and  125   b   3  support the spin-shaft support portion  125   b   1 . 
     The partitions  125   b   2  and  125   b   3  include a first partition  125   b   2 , which covers the upper end of the water supply reservoir  123 . The first partition  125   b   2  protrudes from the spin-shaft support portion  125   b   1  in the centrifugal direction XO. The partitions  125   b   2  and  125   b   3  include a second partition  125   b   3 , which covers the upper end portion of the outer peripheral surface of the water supply reservoir  123 . The second partition  125   b   3  protrudes downwards from the first partition  125   b   2 . The second partition  125   b   3  has a free lower end. 
     The cleaner  100  includes the water feeder  125   c , which guides the water to move from the inside of the body  110  into the water supply reservoir  123 . The tilting frame  125  may include the water feeder  125   c , which receives water from the water supply module  150 . 
     The water feeder  125   c  receives the water from a supply pipe  156 . The water feeder  125   c  forms a water flow passage. The water feeder  125   c  guides the water to pass through the water supply cabinet  125   b  and to be introduced into the water supply reservoir  123 . One end of the flow passage formed by the water feeder  125   c  is connected to the end of the supply pipe  156 . The opposite end of the flow passage formed by the water feeder  125   c  is disposed in the water supply space Sw. One end of the flow passage formed by the water feeder  125   c  is disposed outside the water supply cabinet  125   b  (inside the body  110 ), and the opposite end thereof is disposed inside the water supply cabinet  125   b  (in the portion in which the water supply space Sw is disposed). The water feeder  125   c  is fixed to the tilting frame  125 . The water feeder  125   c  is fixed to the water supply cabinet  125   b . 
     The tilting frame  125  includes the first support portion  125   d , which supports one end of the elastic member  129 . The second support portion  13   b , which is disposed at the base  13 , supports the opposite end of the elastic member  129 . The second support portion  13   b  may be formed at the support member  13   a  of the base  13 . When the tilting frame  125  is tilted about the tilting rotary shaft  126 , the position of the first support portion  125   d  is changed and the length of the elastic member  129  is changed. 
     The first support portion  125   d  is fixed to the tilting frame  125 . The first support portion  125   d  is disposed on the right portion of the left tilting frame  125 . The first support portion  125   d  is disposed on the left portion of the right tilting frame  125 . 
     The second support portion  13   b  is fixed to the base  13 . The second support portion  13   b  is disposed in the right area of the left spin mop module  120 . The second support portion  13   b  is disposed in the left area of the right spin mop module  120 . 
     The first support portion  125   d  is fixed to the tilting frame  125 . When the tilting frame  125  is tilted, the first support portion  125   d  is also tilted with the tilting frame  125 . The first support portion  125   d  protrudes away from the tilting rotary shaft  126  so that the portion to which one end portion of the elastic member  129  is fixed is spaced a predetermined distance apart from the tilting rotary shaft  126 . In the state in which the inclination angle A g   1  or A g   2  is the minimum value, the distance between the first support portion  125   d  and the second support portion  13   b  is the greatest. In the state in which the inclination angle A g   1  or A g   2  is the maximum value, the distance between the first support portion  125   d  and the second support portion  13   b  is the shortest. The elastic member  129  is provided so as to undergo elastic tension stress as the inclination angle A g   1  or A g   2  is reduced to the minimum value. 
     Referring to  FIG.  8   , when the left tilting frame  125  rotates in the counterclockwise direction about the tilting rotary shaft  126  when viewed from the rear side, the second support portion  13   b  moves leftwards and the elastic member  129  is shortened and elastically restored. When the left tilting frame  125  rotates in the clockwise direction about the tilting rotary shaft  126  when viewed from the rear side, the second support portion  13   b  moves rightwards and the elastic member  129  is lengthened and elastically deformed. When the right tilting frame  125  rotates in the clockwise direction about the tilting rotary shaft  126  when viewed from the rear side, the second support portion  13   b  moves rightwards and the elastic member  129  is shortened and elastically restored. When the right tilting frame  125  rotates in the counterclockwise direction about the tilting rotary shaft  126  when viewed from the rear side, the second support portion  13   b  moves leftwards and the elastic member  129  is lengthened and elastically deformed. 
     The tilting frame  125  includes a motor support portion  125   e , which supports the spin-drive unit  124 . The motor support portion  125   e  may support the driving transmission unit  127 . 
     The tilting frame  125  includes the upper-end-limit contact portion  125   f , which is configured so as to be brought into contact with the upper-end limit  13   d . The top surface of the upper-end-limit contact portion  125   f  may be brought into contact with the bottom surface of the upper-end limit  13   d . The left upper-end-limit contact portion  125   f  may be disposed on the left end of the left tilting frame  125 . The right upper-end-limit contact portion  125   f  may be disposed on the right end of the right tilting frame  125 . 
     The first cleaning module  120  includes the tilting rotary shaft  126 , which is a rotating shaft of the tilting frame  125 . The tilting rotary shaft  126  extends in the direction perpendicular to the inclined direction of the spin mop  120   a  or  120   b . The tilting rotary shaft  126  may extend in the horizontal direction. In the present embodiment, the tilting rotary shaft  126  extends in the forward-and-backward direction. 
     The first cleaning module  120  includes the left tilting rotary shaft  126 , which extends in the direction perpendicular to the inclined direction of the bottom surface of the left spin mop  120   a . The first cleaning module  120  includes the right tilting rotary shaft  126 , which extends in the direction perpendicular to the inclined direction of the bottom surface of the right spin mop  120   b . 
     The first cleaning module  120  includes the elastic member  129 , which applies elastic force to the tilting frame  125 . The elastic member  129  stretches when the tilting frame  125  is rotated downwards, and shrinks when the tilting frame  125  is rotated upwards. The elastic member  129  enables shock-absorbing (elastic) operation of the tilting frame  125 . The elastic member  129  applies a moment to the tilting frame  125  so that the inclination angle A g   1  or A g   2  is increased. The elastic member  129  may be disposed such that the entirety thereof extends a long length in the leftward-and-rightward direction. 
     Referring to  FIGS.  12 ,  16 A and  16 B , the first cleaning module  120  includes the lower-end-limit contact portion  120   f , which is configured to be brought into contact with the lower-end limit  13   f . The bottom surface of the lower-end-limit contact portion  120   f  may be brought into contact with the top surface of the lower-end limit  13   f . The lower-end-limit contact portion  120   f  may be disposed on the lower portion of the spin-drive unit  124 . The spin-drive unit  124  may be disposed so as to protrude horizontally from the tilting frame  125 . The lower-end-limit contact portion  120   f  is disposed on the lower portion of the protruding portion of the spin-drive unit  124 . 
     Referring to  FIGS.  11 , and  16 A  to  18 , the water supply module  150  supplies water to the first cleaning module  120 . In the drawings, the water W filling the water tank  151  and the water flow direction WF are illustrated. The water supply module  150  supplies water to the water supply space Sw. The water supply module  150  includes the water tank  151 , which stores water therein. The water tank  151  is disposed inside the body  110 . The water tank  151  is disposed at the upper side of the spin mops  120   a  and  120   b . 
     In the present embodiment, the water supply module  150  includes a pump  155  for applying pressure to the water W inside the water tank  151  so as to move the water. The pump  155  may apply pressure to the water so as to move the water to the spin mop module  120 . The pump  155  may apply pressure to the water W inside the water tank  151  so as to supply the water to the water supply space Sw. 
     Although not illustrated, in another embodiment, the water supply module may include a valve, and when the valve is opened, the water inside the water tank may move to the first cleaning module due to the weight thereof without the pump. 
     Although not illustrated, in a further embodiment, the water supply module may include a water-permeable cap. The water-permeable cap may be disposed in the supply pipe so that the water moves through the water-permeable cap. The water-permeable cap may be configured to reduce the flow rate of the water. 
     Hereinafter, a description will be made based on the present embodiment including the pump  155 , but the invention is not necessarily limited thereto. 
     The water supply module  150  includes the supply pipe  156 , which guides the movement of the water W from the water tank  151  to the first cleaning module  120 . The supply pipe  156  interconnects the water tank  151  and the water feeder  125   c  to guide the movement of the water. The supply pipe  156  may flexibly bend according to the tilting of the tilting frame  125 . 
     The supply pipe  156  includes a first supply pipe  156 - 1 , which guides the movement of the water W from the water tank  151  to the pump  155 , and a second supply pipe  156 - 2 , which guides the movement of the water W from the pump  155  to the first cleaning module  120 . One end of the first supply pipe  156 - 1  is connected to the lower portion of the water tank  151 , and the opposite end thereof is connected to the pump  155 . One end of the second supply pipe  156 - 2  is connected to the pump  155 , and the opposite end thereof is connected to the water feeder  125   c . 
     The second supply pipe  156 - 2  includes a common pipe  156 - 2   m , which guides the movement of the water at an upstream side. One end of the common pipe  156 - 2   m  is connected to the pump  155 , and the opposite end thereof is connected to a three-way connector  156 - 2   t . 
     The second supply pipe  156 - 2  includes a first branch pipe  156 - 2   a  for guiding the movement of the water W to the left spin mop module  120 , and a second branch pipe  156 - 2   b  for guiding the movement of the water W to the right spin mop module  120 . The first branch pipe  156 - 2   a  guides some of the water inside the common pipe  156 - 2   m  to the left spin mop module  120 . The second branch pipe  156 - 2   b  guides the remaining water inside the common pipe  156 - 2   m  to the right spin mop module  120 . One end of the first branch pipe  156 - 2   a  is connected to the three-way connector  156 - 2   t , and the opposite end thereof is connected to the water feeder  125   c  of the left spin mop module  120 . One end of the second branch pipe  156 - 2   b  is connected to the three-way connector  156 - 2   t  and the opposite end thereof is connected to the water feeder  125   c  of the right spin mop module  120 . 
     The second supply pipe  156 - 2  includes the three-way connector  156 - 2   t , which connects the common pipe  156 - 2   m , the first branch pipe  156 - 2   a , and the second branch pipe  156 - 2   b  with each other. The three-way connector  156 - 2   t  forms a T-shaped flow passage overall. The three-way connector  156 - 2   t  includes a flow passage portion, which extends in the forward-and-backward direction and is connected to the common pipe  156 - 2   m . The three-way connector  156 - 2   t  includes two branch flow-passage portions, which extend in two directions from the flow-passage portion connected to the common pipe  156 - 2   m . The two branch flow-passage portions are respectively connected to the first branch pipe  156 - 2   a  and the second branch pipe  156 - 2   b . 
     A description related to the water flow direction WF will be made below with reference to  FIGS.  11 ,  17  and  18   . The pump  155  may be driven to cause movement of the water W. The water W inside the water tank  151  is introduced into the water feeder  125   c  via the supply pipe  156 . The water W inside the water tank  151  sequentially passes through the first supply pipe  156 - 1  and the second supply pipe  156 - 2 . The water W inside the water tank  151  sequentially passes through the common pipe  156 - 2   m  and the first branch pipe and is introduced into the water feeder  125   c  of the left spin mop module  120 . The water W inside the water tank  151  sequentially passes through the common pipe  156 - 2   m  and the second branch pipe and is introduced into the water feeder  125   c  of the right spin mop module  120 . The water introduced into the water feeder  125   c  passes through the tilting frame  125  and is introduced into the water supply reservoir  123 . The water introduced into the water supply reservoir  123  passes through the water supply hole  122   a  and is introduced into the center portion of the mop unit  121 . The water introduced into the center portion of the mop unit  121  moves to the edge of the mop unit  121  due to the centrifugal force generated by the rotation of the mop unit  121 . The water remaining on the floor surface is mopped by the mop unit  131  of the second cleaning module  130 , which follows the mop unit  121  at the rear side thereof. 
     Referring to  FIG.  15 A  to  18 , the body  110  includes a battery support unit  14  for supporting the battery  160 . The battery  160  is disposed on the upper side of the supply pipe by the battery support unit  14 . The battery support unit  14  serves to guide the position of the supply pipe  156 . The common pipe  156 - 2   m , the first branch pipe  156 - 2   a  and the second branch pipe  156 - 2   b  are components in which water, which has a relatively high specific gravity, is accommodated. Therefore, it is desirable for the common pipe  156 - 2   m , the first branch pipe  156 - 2   a  and the second branch pipe  156 - 2   b  to be arranged so as to be bilaterally symmetrical to each other in order to evenly distribute the weight that is applied to the left spin mop  120   a  and the right spin mop  120   b . To this end, the battery support unit  14  guides the positions of the common pipe  156 - 2   m , the first branch pipe  156 - 2   a  and the second branch pipe  156 - 2   b . 
     The battery support unit  14  includes a supporter  14   a  disposed at the lower side of the battery  160 . The supporter  14   a  supports the battery  160 . The supporter  14   a  may be disposed between the left spin mop module  120  and the right spin mop module  120 . The supporter  14   a  is disposed at the center portion of the body  110  in the leftward-and-rightward direction. The supporter  14   a  may be formed in a square column shape overall. 
     The battery support unit  14  includes a stopper  14   b  for restricting the horizontal movement of the battery  160 . The stopper  14   b  includes a first stopper  14   b   1 , which contacts the front surface of the battery  160 , and a second stopper  14   b   2 , which contacts the rear surface of the battery  160 . 
     The battery support unit  14  has therein a main recess  14   g , into which the common pipe  156 - 2   m  is inserted. The main recess  14   g  is formed in the supporter  14   a . The main recess  14   g  is formed in the rear surface of the supporter  14   a . The common pipe  156 - 2   m  is fixed in the main recess  14   g , and the position of the common pipe  156 - 2   m  is therefore maintained. 
     The battery support unit  14  forms two branch recesses  14   h , into which the first branch pipe  156 - 2   a  and the second branch pipe  156 - 2   b  are inserted. The two branch recesses  14   h  are formed in the supporter  14   a . The two branch recesses  14   h  are respectively formed at portions of the supporter  14   a  that are located in the leftward-and-rightward direction. Because the first branch pipe  156 - 2   a  and the second branch pipe  156 - 2   b  are respectively fixed in the two branch recesses  14   h , the positions of the first branch pipe  156 - 2   a  and the second branch pipe  156 - 2   b  are maintained. 
     The supporter  14   a  may guide the position of the three-way connector  156 - 2   t . The three flow passage portions of the three-way connector  156 - 2   t  may be respectively inserted into the main recess  14   g  and the two branch recesses  14   h . 
     Referring to  FIGS.  11  to  14   , the cleaner  100  may further include a sterilized-water-generating module  170 . The sterilized-water-generating module  170  may be configured to generate sterilized water via electrolysis of water inside the water tank  151 . For example, hypochlorous acid (HClO) sterilized water may be generated via electrolysis using a chlorine component contained in the tap water. The sterilized-water-generating module  170  may be disposed at the water tank  151 . 
     The sterilized-water-generating module  170  includes a pair of electrodes  171 , which are spaced apart from each other. One of the pair of electrodes  17  is a positive (+) electrode, and the other one is a negative (-) electrode. The electrolysis of water is performed and the sterilized water is generated by electric charges supplied from the pair of electrodes  171 . The sterilized-water-generating module  170  includes a power connector  173 , which receives electric energy of the battery  160 . Power is supplied to the electrodes  171  through the power connector  173 . The sterilized-water-generating module  170  includes a module case  175 , which accommodates the electrodes  171  therein. The power connector  173  may be disposed at the bottom surface of the module case  175 . The sterilized-water-generating module  170  includes a communication portion  177 , in which an opening is formed so as to allow the sterilized water generated by the electrodes  171  to be introduced into the water tank  151  therethrough. The communication portion  177  is disposed at the upper side of the module case  175 .