Motor drive control device, motor unit, and motor drive control method

A motor drive control device comprising:

• a control unit configured to monitor a rotational state of a rotor of a two-phase stepping motor, set an energization angle representing a magnitude of an electric angle for continuously energizing, of coils of two phases of the two-phase stepping motor, a coil of one phase in one direction based on the rotational state of the rotor, and generate a control signal for controlling driving of the two-phase stepping motor based on the set energization angle;
• and
• a drive unit configured to drive the coils of two phases based on the control signal, wherein
• the control unit monitors a load of the rotor as the rotational state of the rotor, and sets the energization angle such that the energization angle decreases as the load of the rotor decreases, wherein
• the control unit has, as operation modes, a one-two-phase excitation mode of alternately repeating one-phase excitation of exciting the coil for one phase of the coils of two phases, and two-phase excitation of exciting the coils for two phases of the coils of two phases, and a one-phase excitation mode of exciting the coil for one phase of the coils of two phases, and
• the control unit sets the energization angle to 90° and selects the one-phase excitation mode when the measurement value of the load of the rotor becomes equal to or smaller than a lower limit threshold value, and sets the energization angle to a value larger than 90° and selects the one-two-phase excitation mode when the measurement value of the load of the rotor becomes equal to or larger than an upper limit threshold value.

A motor drive control method for controlling driving of a two-phase stepping motor by a motor drive control device, the motor drive control method comprising:

• a first step of monitoring, by the motor drive control device, a rotational state of a rotor of the two-phase stepping motor;
• a second step of setting, by the motor drive control device, an energization angle representing a magnitude of an electric angle for continuously energizing, of coils of two phases of the two-phase stepping motor, a coil of one phase in one direction, based on the rotational state of the rotor;
• a third step of generating, by the motor drive control device, a control signal for controlling driving of the two-phase stepping motor based on the energization angle set in the second step;
• and
• a fourth step of driving, by the motor drive control device, the coils of two phases based on the control signal, wherein
• the first step includes a step of monitoring a rotational speed of the rotor as the rotational state of the rotor, and the second step includes a fifth step of setting the energization angle such that the energization angle decreases as the rotational speed of the rotor increases, wherein
• the motor drive control device has, as operation modes, a one-two-phase excitation mode of alternately repeating one-phase excitation of exciting the coil for one phase of the coils of two phases, and two-phase excitation of exciting the coils for two phases of the coils of two phases, and a one-phase excitation mode of exciting the coil for one phase of the coils of two phases, and
• the fifth step includes a step of setting the energization angle to 90° and selecting the one-phase excitation mode when the rotational speed of the rotor becomes equal to or larger than an upper limit threshold value, and a step of setting the energization angle to a value larger than 90° and selecting the one-two-phase excitation mode when the rotational speed of the rotor becomes equal to or smaller than a lower limit threshold value smaller than the upper limit threshold value.