Brushless motor and motor control device

Patent metadata

Field	Value
Publication number	US-9692342-B2
Application number	US-201514867438-A
Country	US
Kind code	B2
Filing date	Sep 28, 2015
Priority date	Oct 24, 2014
Publication date	Jun 27, 2017
Grant date	Jun 27, 2017

Abstract

A brushless motor for an electric power steering device that assists a steering operation includes: a stator having a plurality of winding sets for a plurality of systems respectively; and a rotator having a ferrite magnet. In the motor, a maximum current flowing without any demagnetization at high temperature is large. Hence, the torque of the motor is easily ensured at high temperature. In particular, when a failure occurs in one system, it is easy to ensure the torque of the normal system even at high temperature.

First claim

What is claimed is:

1. A motor control device that controls energization of a brushless motor for an electric power steering device that assists a steering operation, the brushless motor comprising a stator having a plurality of winding sets for a plurality of systems respectively, and a rotator having a ferrite magnet, the motor control device comprising:
a plurality of inverters for the systems respectively, each of which corresponds to a winding set of a respective system, and supplies an alternating current to the winding set of the respective system;
a current command value calculation device that calculates a dq-axis current command value for energizing the winding sets;
a temperature estimation device that estimates temperature of the ferrite magnet; and
a temperature rising control device that calculates a temperature rising dq-axis current command value, to be added to the dq-axis current command value, for flowing a temperature rising current in the winding sets when an estimated temperature is lower than a predetermined value;
a maximum current limit device that controls the dq-axis current command value, wherein:
the maximum current limit device decreases a maximum current limit value of the dq-axis current command value when the temperature estimated by the temperature estimation device is reduced.

2. The motor control device according to claim 1 , wherein:
the temperature rising control device sets the temperature rising dq-axis current command value so that a q-axis sum of the temperature rising current in all of the systems becomes zero.

3. The motor control device according to claim 2 , wherein:
the temperature rising control device sets the temperature rising dq-axis current command value so that each of a d-axis sum and a q-axis sum of the temperature rising current in all of the systems becomes zero.

4. The motor control device according to claim 1 , further comprising:
a failure detection device that detects a failure of one of the inverters and the winding sets, wherein:
when the failure of one of an inverter and a corresponding winding set in one of the systems is detected by the failure detection device, the motor control device stops an output from the inverter in a failure system, and controls an output from an inverter in a normal system to compensate a brake torque generated in the failure system.

5. The motor control device according to claim 4 , further comprising:
a maximum current limit device that controls the dq-axis current command value for each of the winding sets in a respective system, wherein:
when the failure of one of the winding set and the inverter in one of the systems is detected by the failure detection device, the maximum current limit device increases a maximum current limit value of the dq-axis current command value in the normal system when the temperature estimated by the temperature estimation device is increased.

6. A motor control device that controls energization of a brushless motor for an electric power steering device that assists a steering operation, the brushless motor comprising a stator having a plurality of winding sets for a plurality of systems respectively, and a rotator having a ferrite magnet, the motor control device comprising:
a plurality of inverters for the systems respectively, each of which corresponds to a winding set of a respective system, and supplies an alternating current to the winding set of the respective system;
a current command value calculation device that calculates a dq-axis current command value for energizing the winding sets;
a temperature estimation device that estimates temperature of the ferrite magnet; and
a temperature rising control device that calculates a temperature rising dq-axis current command value, to be added to the dq-axis current command value, for flowing a temperature rising current in the winding sets when an estimated temperature is lower than a predetermined value, wherein:
the temperature rising control device sets the temperature rising dq-axis current command value so that a q-axis sum of the temperature rising current in all of the systems becomes zero.

Assignees

• Denso Corp

Inventors

• Kano Ryo
• Suzuki Takashi
• Kabune Hideki

Classifications

• H02P25/22 Primary

  Multiple windings; Windings for more than three phases · CPC title

• B62D5/046

  Controlling the motor · CPC title

• H02K3/28

  Layout of windings or of connections between windings (windings for pole-changing H02K17/06, H02K17/14, H02K19/12, H02K19/32) · CPC title

• H02P29/66

  Controlling or determining the temperature of the rotor · CPC title

• B62D5/0403

  characterised by constructional features, e.g. common housing for motor and gear box · CPC title