reference will now be made in detail to the preferred embodiments of the present invention , examples of which are illustrated in the accompanying drawings . as shown in fig1 through 3 , a robot cleaner in accordance with the present invention , comprises a suction unit 60 installed within a cleaner body 1 for sucking dirt on a floor ; a driving unit 50 for moving the cleaner body 1 ; at least one navigation sensor 30 installed at one side of the cleaner body 1 for sensing a position of an obstacle ; a detecting unit 10 mounted at the cleaner body 1 for detecting a height between a bottom of the cleaner body 1 and a floor ; and a control unit 11 controlling each of the mentioned components and controlling the suction unit 60 in response to signal from the detecting unit 10 , thus adjusting a suction force of the suction unit 10 . the suction unit 60 comprises a fan motor 2 installed inside the cleaner body 1 and generating a suction force for sucking dirt on a floor ; a filter container 4 installed in the vicinity of the fan motor 2 and having a filter 3 for filtering dirt sucked by the fan motor 2 ; a suction head 6 through which dirt on a floor is sucked , the suction head 6 provided at a lower portion of the cleaner body 1 and connected to the filter container 4 through a connection pipe 5 ; and a brush 7 rotatably disposed in the suction head , for brushing dirt attached on a floor . the driving unit 50 comprises a driving wheel 8 rotatably installed at the cleaner body 1 ; a driving motor 51 connected to the driving wheel 8 , for rotating the driving wheel ; and at least one supporting wheel 12 installed at a bottom of the cleaner body 1 to be rotated by movement of the cleaner body 1 , for supporting the cleaner body 1 on a floor . the navigation sensor 30 includes an ultrasonic wave transmitter 31 installed at a front and central portion in the cleaner body 1 , for transmitting ultrasonic waves ; and ultrasonic wave receiver 32 respectively installed at upper and lower sides of the ultrasonic transmitter 31 , for receiving ultrasonic waves reflected by an obstacles and for outputting signals to the control unit 11 . as shown in fig4 , the detecting unit 10 comprises an auxiliary wheel 9 formed in a cylindrical shape , inserted into a recessed portion 90 in a bottom of the cleaner body 1 to be contacted with a floor , and rotated by movement of the cleaner body 1 ; a connecting link 101 hingedly connected to a hinge shaft 94 protruded from both ends of the auxiliary wheel 9 , penetrating a through hole 92 in the recessed portion , and pivotally connected to a pivot shaft 104 fixed in the cleaner body 1 ; and a sensing unit disposed in the vicinity of one end of the connecting link 101 , for sensing the amount of rotation of the connecting link 101 and measuring the amount of vertical displacement of the wheel . the auxiliary wheel 9 and the connecting link 101 are displaced in a vertical direction according to unevenness of a floor by their weight . herein , in order that the auxiliary wheel 9 and the connecting link 101 are smoothly moved , preferably , an elastic member 102 of which one end is fixed to the body 1 and another end is fixed to the connecting link 101 is provided so that a preset elastic force is applied to the connecting link 101 and the auxiliary wheel 9 . the elastic member 102 may be a coil spring , but is not limited thereto . various forms such as a torsion bar or the like may be applied as the elastic member 102 . by such an elastic member 102 , the auxiliary wheel 9 is always in contact with a floor , and the cleaner body 1 maintains a horizontal state . the sensing unit comprises a rotating plate 112 installed at an end of the connecting link 101 and has a plurality of slits 111 having different shapes from each other ; and an optical sensor 115 including a light emitter 113 for emitting light toward the rotating plate 112 and a light receiver 114 for receiving light passing through the slits 111 of the rotating plate 112 . preferably , the detecting unit 10 is installed at the front in a direction that the cleaner body 1 travels on the basis of the suction head 6 in order to cope with a height between a bottom of the cleaner body 1 and a floor by measuring them . meanwhile , a battery 21 is installed in the cleaner body 1 . a charging terminal unit 23 is provided at a rear surface of the body 1 and includes a charging terminal 22 connected to a connection terminal 26 of a power terminal unit 25 installed on a wall surface 24 of a room , for charging the battery 21 . in addition , a light - emitting unit 41 is installed at the lower side of the power terminal unit 25 and emits an optical signal for inducing a cleaner body 1 toward a power terminal unit 25 , and a light - receiving unit 42 is installed at a lower side of the charging terminal unit 23 and receives an optical signal emitted from the light - emitting unit 41 . when a user operates a robot cleaner in accordance with the present invention constructed as above , the control unit 11 and the navigation sensor 30 are operated , and a driving wheel 8 connected to the driving motor 51 is rotated . thusly , the robot cleaner travels a cleaning zone along a set pattern , and simultaneously , the fan motor 2 is driven . accordingly , the cleaning is made by sucking dirt on a floor to the filter 3 through the suction head 6 and the connection pipe 5 and filtering the sucked dirt . as shown in fig5 and 6 , when the cleaner body 1 carries out the cleaning operation and travels a concaved portion 121 or a convexed portion 122 , since the cleaner body 1 , particularly the suction head 6 , is not moved along a curved surface of the concaved portion 121 or the convexed portion 122 , but is always moved in a state of maintaining its horizontal state . accordingly , a height between the bottom of the cleaner body 1 and the floor is changed . therefore , the height between the bottom of the cleaner body 1 and the floor is measured by the detecting unit 10 , and a suction force is variously applied in accordance with the respective portion . that is , as shown in fig5 , when the cleaner travels a concaved portion 121 lower than a level ground , the auxiliary wheel 9 is pushed downwardly by an elastic force of the elastic member 102 or a self - weight of the auxiliary wheel 9 . accordingly , the connecting link 101 and the rotating plate 112 are rotated centering on the pivot shaft 104 ( counterclockwise in fig5 ), the amount of displacement of the rotating plate 112 is sensed by the optical sensor 115 . and , the amount of displacement of the rotating plate 112 , sensed by the optical sensor 115 is inputted to the control unit 11 , and the control unit 11 increases a rotation force of the fan motor 2 according to the inputted value , to thereby increase a suction force , so that dirt on the concaved portion 121 can be sucked . in addition , as shown in fig6 , when the cleaner travels the convexed portion 122 , the auxiliary wheel 9 is pushed upwardly by the convexed portion 122 . accordingly , the connecting link 101 and the rotating plate 112 are rotated centering on the pivot shaft 104 ( clockwise in fig6 ), and the amount of displacement of the rotating plate 112 is sensed by the optical sensor 115 . and , the amount of displacement of the rotating plate 112 , sensed by the optical sensor 115 is inputted to the control unit 11 , and the control unit 11 decreases a rotation force of the fan motor 2 according to the inputted value , so that dirt is sucked with a relatively small suction force . hereinafter , operations of the robot cleaner in accordance with the present invention will now be described with reference to fig7 . the letter ‘ s ’ in the drawing means each step . first , when a user operates a switch of a cleaner , the cleaner moves in a cleaning zone according to the preset pattern , and performs a cleaning operation ( s 1 ). when the cleaner travels an uneven portion of a floor while carrying out cleaning operation in the cleaning zone , the detecting unit 10 senses the amount of vertical displacement of the auxiliary wheel 9 ( s 2 ). that is , the light - receiving unit 114 measures how much light emitted by the light - emitting unit 113 of the optical sensor 115 passes through slits formed at the rotating plate , and its resulting value is outputted to the control unit 11 . and , the control unit 11 performs an operation of comparing the measured value of vertical displacement of the auxiliary wheel 9 and a preset reference value ( s 3 ). after the amount of vertical displacement of the auxiliary wheel 9 and a preset reference value have been compared , if it is determined that the cleaner travels a concaved portion 121 lower than a level ground , a rotation force of the fan motor 2 is increased , thereby increasing a suction force for sucking dirt . if it is determined that the cleaner travels a convexed portion 122 higher than a level ground , a rotation force of the fan motor 2 is decreased , thereby decreasing a suction force for sucking dirt . in addition , if the floor is even , or unevenness of the floor is very small , the suction force is adjusted to a suction force set in an early stage ( s 4 ). then , the control unit 11 determines whether a cleaning operation of a cleaner has been completed ( s 5 ). and , if the cleaning operation has not been completed , cleaning is performed again . if the cleaning operation has been completed , the cleaner returns to the power terminal unit 25 , and the battery 21 is charged ( s 6 ). as so far described , the robot cleaner in accordance with the present invention senses the unevenness of the floor , and variously controls a suction force thereof , thus cleaning efficiency can be improved . as the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof , it should also be understood that the above - described embodiments are not limited by any of the details of the foregoing description , unless otherwise specified , but rather should be construed broadly within its spirit and scope as defined in the appended claims , and therefore all changes and modifications that fall within the metes and bounds of the claims , or equivalence of such metes and bounds are therefore intended to be embraced by the appended claims .
a robot cleaner includes a suction device installed within a cleaner body , that sucks dirt on a floor ; a driver that moves the cleaner body ; a detector mounted at the cleaner body , that detects a height between a bottom of the cleaner body and the floor ; and a controller that controls the suction device in response to signal from the detector to adjust a suction force of the suction device in accordance with the height between the bottom of the cleaner body and the floor .