Abstract:
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.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a robot cleaner and its operating method, and more particularly, to a robot cleaner and its operating method capable of improving cleaning efficiency by controlling a suction force according to a height between a cleaner and a floor. 
   2. Description of the Background Art 
   In general, a robot cleaner is a machine that detects a cleaning zone by itself, an obstacle or the like without operation of a user, cleans while moving by itself, moves to a charging station by itself when power of a battery is consumed, to be charged, and returns to a cleaning zone when the charging is completed, to perform a cleaning operation. 
   Such a robot cleaner includes a suction unit for sucking dirt on a floor; a driving wheel connected to a driving motor to make the robot cleaner travel; a navigation sensor for determining a position of a cleaner and a position of an obstacle or the like; and a control unit for automatically controlling the cleaner. The robot cleaner performs a cleaning operation, moving along a preset pattern, and an encoder connected to the driving wheel senses a rotation state of the driving wheel, to thereby determine a traveling state of the cleaner. 
   However, the conventional robot cleaner has following problems. 
   The conventional robot cleaner sucks dirt with the same suction force during cleaning operation. For this reason, dirt cannot be properly sucked at a concaved portion where a height between a bottom of a cleaner and itself is relatively high. Also, excessive suction force, which is stronger than a required suction force is applied to a convexed portion where a height between a bottom of the cleaner and itself is relatively low, thereby causing deterioration in efficiency of a cleaner. 
   SUMMARY OF THE INVENTION 
   Therefore, an object of the present invention is to provide a robot cleaner and its operating method capable of improving cleaning efficiency by controlling a suction force for sucking dirt on a floor according to a height between a cleaner and a floor. 
   To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a robot cleaner comprising a suction unit installed within a cleaner body, for sucking dirt on a floor; a driving unit for moving the cleaner body; a detecting unit mounted at the cleaner body, for detecting a height between a bottom of the cleaner body and a floor; and a control unit controlling the suction unit in response to signal from the detecting unit, for adjusting a suction force of the suction unit in accordance with the height between the bottom of the cleaner body and the floor. 
   To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided an operating method of a robot cleaner comprising a first step of carrying out cleaning operation by moving by itself and sucking dirt on a floor; a second step of detecting a height between a bottom of the cleaner and a floor; and a third step of controlling a suction force for sucking dirt on the floor in accordance with the height between the bottom of the cleaner and a floor. 
   The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a unit of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. 
     In the drawings: 
       FIG. 1  is a view showing a front side of a robot cleaner in accordance with the present invention; 
       FIG. 2  is a sectional view showing a robot cleaner in accordance with the present invention; 
       FIG. 3  is a view showing a bottom of a robot cleaner in accordance with the present invention; 
       FIG. 4  is a partially sectional view showing a detecting unit provided in a robot cleaner in accordance with the present invention; 
       FIGS. 5 and 6  are views showing operational states of a detecting unit provided in a robot cleaner in accordance with the present invention; and 
       FIG. 7  is a flow chart sequentially showing operation of a robot cleaner in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   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  FIGS. 1 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  FIG. 4 , 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  FIGS. 5 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  FIG. 5 , 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  FIG. 5 ), 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  FIG. 6 , 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  FIG. 6 ), 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  FIG. 7 . 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.