Electric linear motion actuator
In this electric linear motion actuator, a linear motion mechanism and an electric motor are arranged in line along the same axis, which is an axis of a rotation input/output shaft of the linear motion mechanism. The electric motor includes a stator and a rotor which are arranged such that the directions of magnetic poles thereof for generating interlinkage magnetic flux contributing to a torque are parallel to a rotation shaft of a motor. The rotor has torque generating surfaces at both faces in the axial direction thereof. The stator has first and second excitation mechanisms arranged on both sides in the axial direction of the rotor. The first and second excitation mechanisms have independent first and second system coil groups. A power supply system for independently supplying power to the first and second system coil groups is provided.
1. An electric linear motion actuator comprising:
an electric motor;
a linear motion mechanism having a rotation input/output shaft and configured to convert rotary motion of the electric motor to linear motion of a linear motion portion via the rotation input/output shaft; and
a control device configured to control the electric motor, wherein
the linear motion mechanism and the electric motor are arranged in line along the same axis, which is an axis of the rotation input/output shaft of the linear motion mechanism,
the electric motor includes a stator and a rotor which are arranged such that directions of magnetic poles thereof for generating interlinkage magnetic flux contributing to generating a torque are parallel to a rotation shaft of the electric motor,
the rotor has respective torque generating surfaces at both faces in an axial direction of the rotor,
the stator has a plurality of excitation mechanisms arranged on both sides in the axial direction of the rotor, respectively, the plurality of excitation mechanisms including independent coil groups in such a manner that one or more systems of the independent coil groups are provided for one of the excitation mechanisms in the axial direction, and thus two or more systems of the independent coil groups are provided in total for both the excitation mechanisms in the axial direction, and
a power supply system configured to independently supply power to the independent coil groups is provided.
2. The electric linear motion actuator as claimed in claim 1 , wherein
the control device includes a motor power abnormality determination section configured to determine whether or not a state of power supply to each excitation mechanism is normal, on the basis of a predetermined relationship of current and voltage in the excitation mechanism.
3. The electric linear motion actuator as claimed in claim 2 , wherein
the motor power abnormality determination section determines whether or not the state of power supply to each excitation mechanism is normal, on the basis of information including a comparison between a predetermined relationship of average current and average voltage in the plurality of excitation mechanisms, and a predetermined relationship of current and voltage in each excitation mechanism.
4. The electric linear motion actuator as claimed in claim 2 , wherein
the control device includes:
a power supply limitation/interruption function section configured to, when the motor power abnormality determination section has determined that the state of power supply to one of the excitation mechanisms is abnormal, limit or interrupt supply of power to the one excitation mechanism; and
a complement function section configured to complement a torque that is reduced due to the limitation or interruption of supply of power to the one excitation mechanism, by the other excitation mechanism whose power supply state has been determined to be normal by the motor power abnormality determination section.
5. The electric linear motion actuator as claimed in claim 4 , wherein
the control device has an axial load estimating function section configured to estimate a magnitude of an axial load caused by linear motion of the linear motion portion of the linear motion mechanism, and
the power supply limitation/interruption function section limits a motor current so that a current applicable to the electric motor is smaller than that in a case where the supply of power is not limited or interrupted, when the state of power supply to the one excitation mechanism has been determined to be abnormal and the axial load estimated by the axial load estimating function section is smaller than a predetermined magnitude.