Electric power steering apparatus

Patent metadata

Field	Value
Publication number	US-2017282966-A1
Application number	US-201515519581-A
Country	US
Kind code	A1
Filing date	Dec 25, 2015
Priority date	Dec 25, 2014
Publication date	Oct 5, 2017
Grant date	—

Abstract

An electric power steering apparatus that driving-controls a motor via inverters based on a current command value, and applies an assist force by the motor to a steering system, includes multi-system driving systems with the inverters for respective system-windings of the motor which is a multi-system motor, wherein respective multi-system current command value characteristics against a steering torque are applied so as to be disproportionate for left and right steering, to the respective multi-system driving systems, and an assist-control is performed in response to the individual current command value characteristics.

First claim

1 . An electric power steering apparatus that driving-controls a motor via inverters based on a current command value which is a steering command, and applies an assist force by means of said motor to a steering system of a vehicle, comprising:
multi-system driving systems with said inverters for respective system-windings of said motor which is a multi-system motor, wherein said electric power steering apparatus applies respective multi-system current command value characteristics against a steering torque so as to be disproportionate to said respective multi-system driving systems at a left steering maneuver and a right steering maneuver, and assist-controls in response to said individual current command value characteristics for said multi-system driving systems.

2 . The electric power steering apparatus according to claim 1 , wherein said multi-system current command value characteristics have offsets near a handle center and have characteristics that a difference of offset amounts is larger as an absolute value of said steering torque becomes larger.

3 . The electric power steering apparatus according to claim 2 , wherein a degree of said offset is changeable characteristic.

4 . The electric power steering apparatus according to claim 3 , wherein said changeable characteristic is a vehicle speed sensitive-characteristic.

5 . The electric power steering apparatus according to claim 4 , wherein said vehicle speed sensitive-characteristic has a smaller offset near said handle center, and has a larger or smaller degree of a difference of said offset amounts as said vehicle speed becomes higher.

6 . The electric power steering apparatus according to claim 1 , wherein all of said multi-system motor, said multi-system driving systems and said multi-system current command value characteristics are at least dual-system.

7 . The electric power steering apparatus according to claim 6 , wherein said motor has a dual-system windings of a star-connection.

8 . The electric power steering apparatus according to claim 6 , wherein said motor has a dual-system windings of a delta-connection.

9 . The electric power steering apparatus according to claim 1 , wherein all of said multi-system motor, said multi-system driving systems and said multi-system current command value characteristics are dual-system, one part of a dual-system motor is used to one direction region by a one-direction current command value, and other part of said dual-system motor is used to other direction region by an other-direction current command value.

10 . The electric power steering apparatus according to claim 9 , wherein said one-direction current command value has an offset 1 and said other-direction current command value has an offset 2 near a handle center.

11 . The electric power steering apparatus according to claim 10 , wherein said one-direction current command value increases as said steering torque becomes larger in said one direction region and said other-direction current command value increases as said steering torque becomes larger in said other direction region.

12 . The electric power steering apparatus according to claim 11 , wherein varying characteristics of said one-direction current command value and said other-direction current command value are changeable.

13 . The electric power steering apparatus according to claim 10 , wherein said offset 1 is equal to said offset 2 .

14 . The electric power steering apparatus according to claim 10 , wherein said offset 1 is different from said offset 2 .

15 . The electric power steering apparatus according to claim 13 , wherein said offset 1 and said offset 2 varies in response to said vehicle speed.

16 . An electric power steering apparatus that driving-controls a motor via inverters based on a current command value which is a steering command, and applies an assist force by means of said motor to a steering mechanism of a vehicle;
wherein said motor is at least dual-system motor and said inverters are provided for respective system-windings of said motor, wherein one part of said at least dual-system motor is used to one direction region by a one-direction current command value and other part of said at least dual-system motor is used to other direction region by an other-direction current command value, and wherein said one-direction current command value has an offset 1 and said other-direction current command value has an offset 2 near a handle center, and said offset 1 and said offset 2 are calculated based on a travel state of said vehicle and an acting force applied to said steering mechanism.

17 . The electric power steering apparatus according to claim 16 , wherein said offset 1 and said offset 2 vary in response to said acting force when said travel state of said vehicle is a straight-travel state.

18 . The electric power steering apparatus according to claim 17 , wherein in said straight-travel state, said offset 1 increases as said acting force becomes larger in said one direction region, and said offset 2 increases as said acting force becomes larger in said other direction region.

19 . The electric power steering apparatus according to claim 17 , wherein in said straight-travel state, said offset 2 decreases as said acting force becomes larger in said one direction region, and said offset 1 decreases as said acting force becomes larger in said other direction region.

20 . The electric power steering apparatus according to claim 17 , wherein said offset 1 and said offset 2 respectively return to initial values based on a rotational angle and said acting force of said steering mechanism when said vehicle deviates from said straight-travel state.

21 . The electric power steering apparatus according to claim 17 , wherein said offset 1 and said offset 2 gradually vary and gradually return to said respective initial values.

22 . The electric power steering apparatus according to claim 16 , wherein varying characteristics of said one-direction current command value and said other-direction current command value are changeable.

23 . The electric power steering apparatus according to claim 16 , wherein said acting force is a self-aligning torque or a steering torque.

Assignees

• Nsk Ltd

Inventors

• Fukuda Toshihiro
• Nomura Yasuhide
• Oumi Tamotsu

Classifications

• B62D5/046 Primary

  Controlling the motor · CPC title

• B62D5/0463

  calculating assisting torque from the motor based on driver input · CPC title

• H02P25/22

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

• B62D5/0466

  for returning the steering wheel to neutral position · CPC title

• B62D5/0403

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