Motor controller

1. A motor controller having a driving control unit of a brushless motor that includes a rotor having magnetic pole position detecting magnets attached thereto and a predetermined number of poles, a stator having multiple phase exciting windings, and position detecting units provided in correspondence to individual phases of the stator for detecting magnetic poles of the magnetic pole position detecting magnets and for outputting detection signals with logic levels corresponding to polarities of the magnetic poles, wherein the driving control unit is connected to output signal lines of the position detecting units of the brushless motor, successively receives output patterns based on the detection signals from the position detecting units via the output signal lines, and rotates the rotor by switching current supply to exciting windings of the individual phases of the stator in response to exciting patterns corresponding to the output patterns, the motor controller comprising:

a pattern checking unit for deciding that there is a shift of the rotor from a target position and a counterrotation of the rotor involved with the shift, if an output pattern based on a signal with a prescribed logic level corresponding to a short circuit to or disconnection from ground potential of at least one of the output signal lines is received, and if the output patterns based on the detection signals received before and after the output pattern are found to have different patterns by comparison.

2. The motor controller according to claim 1 , further comprising a timer output unit for starting counting from an abnormality decision by the pattern checking unit, and for outputting a signal indicating the abnormality decision during a period of the counting.

3. The motor controller according to claim 1 , wherein

the magnetic pole position detecting magnet has a number of magnetic poles twice a number of poles of the rotor; and

the position detecting units comprise Hall elements for detecting magnetic pole positions of the rotor from magnetic fluxes from the magnetic pole position detecting magnets, and the motor controller further comprising:

an integrating unit for multiplying driving duty ratios of pulse width modulation control by the driving control unit and position velocity indicating changes of actual position of the rotor; and

a comparing-deciding unit for comparing an integral value calculated by the integrating unit with a prescribed threshold, and for making a decision of counterrotation of the rotor when the integral value is less than the prescribed threshold.

4. The motor controller according to claim 3 , wherein

the comparing-deciding unit successively receives the integral values calculated by the integrating unit, and makes a decision that the rotor makes counterrotation if the integral values are less than a prescribed threshold by a predetermined number of consecutive times.

5. The motor controller according to claim 3 , wherein the comparing-deciding unit comprises:

a first comparing-deciding unit for successively receiving the integral values calculated by the integrating unit, and for outputting a signal with a logic level indicative of the counterrotation of the rotor if the integral values are less than a first threshold by a predetermined number of consecutive times; and

a second comparing-deciding unit for successively receiving the integral values calculated by the integrating unit, for making a decision that the rotor makes counterrotation if the integral values are less than a second threshold which is less than the first threshold by a number of consecutive times greater than the first comparing unit, and for outputting the signal with the logic level indicative of the counterrotation, and wherein the motor controller further comprises:

a timer output unit for starting counting from a moment of an abnormality decision by the pattern checking unit, and for outputting a signal with the logic level indicating the abnormality decision during a period of the counting;

an AND circuit for receiving output signals of the timer output unit and of the first comparing unit, and for performing AND operation between them; and

an OR circuit for receiving an AND operation result by the AND circuit and an output signal of the second comparing unit, and for outputting an OR operation between them as a final decision result as to the counterrotation of the rotor.

6. The motor controller according to claim 3 , wherein the driving control unit corrects the counterrotation of the rotor by correcting a sequence of switching the motor exciting patterns if the counterrotation of the rotor is decided.