Patent ID: 8092407

Claim:
A massage machine comprising: a chair; a driving unit which itself moves up and down along guide rails provided on a backrest of the chair; a first motor that moves the driving unit up and down along the guide rails; a pair of treatment head bases provided in the driving unit and driven reciprocally in opposite directions to each other along widthwise direction of the chair; a second motor that reciprocally drives the pair of treatment head bases in opposite directions to each other; treatment heads respectively supported on the pair of treatment head bases, and driven so that a major component of motion is in a plane substantially perpendicular to the backrest of the chair; a third motor that drives the treatment heads so that the major component of motion becomes substantially perpendicular to the backrest of the chair; and a control circuit that drives the first motor, the second motor and the third motor respectively independently of one another, and wherein at least one of the first motor, the second motor and the third motor is a brushless DC motor having a rotation number detecting circuit, and the control circuit having a rotation speed calculator that counts a time period between signals outputted from the rotation number detecting circuit of the brushless DC motor so as to calculate a rotation speed of the motor, a speed controller that compares a target rotation speed with the rotation speed obtained by calculation and conforms the rotation speed obtained by the calculation with the target rotation speed, and a voltage controller that controls a pulse voltage applied to a winding of the brushless DC motor by pulse width modulation (PWM) control using a target sinusoidal waveform and a triangular waveform having a predetermined carrier frequency which are overlaid on each other so as to define a pulse width as a time period from a first time when both of the target sinusoidal waveform and the triangular waveform intersect to a second time when both of the target sinusoidal waveform and the triangular waveform intersect, thereby allowing the current flowing through the winding of the brushless DC motor to have a substantially sinusoidal waveform.