Brushless motor and motor control device

• US 9,692,342 B2
• Filed: 09/28/2015
• Issued: 06/27/2017
• Est. Priority Date: 10/24/2014
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Kabune, Hideki, Kano, Ryo, Suzuki, Takashi
• Primary Examiner(s): Leykin, Rita
• Application Number:
  US14/867,438
• Publication Number:
  US 20160118923A1
• Time in Patent Office: 638 Days
• Field of Search: 31840002, 318724, 318473, 318634, 318641, 31840022, 318471
• CPC Class Codes: B62D 5/0403 characterised by constructional features, e.g. common housing for motor and gear box
• CPC Class Codes: B62D 5/046 Controlling the motor
• CPC Class Codes: B62D 5/0496 by using a temperature sensor
• CPC Class Codes: H02K 3/28 Layout of windings or of connections between windings windings for pole-changing H02K17/06, H02K17/14, H02K19/12, H02K19/32
• CPC Class Codes: H02P 25/22 Multiple windings; Windings for more than three phases
• CPC Class Codes: H02P 29/66 Controlling or determining the temperature of the rotor

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.

Claims

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.