Electric power steering apparatus

• US 20040007419A1
• Filed: 05/27/2003
• Published: 01/15/2004
• Est. Priority Date: 05/27/2002
• Status: Active Grant

• Current Assignee: Koyo Seiko Co., Ltd. (Toyota Motor Corporation)
• Original Assignee: Koyo Seiko Co., Ltd. (Toyota Motor Corporation)
• Inventors: Maeda, Naoki, Kotaka, Kenichi, Tokumoto, Yoshitomo, Shiba, Mahito
• Granted Patent: US 6,973,991 B2
• Time in Patent Office: Days
• US Class Current: 180/446
• CPC Class Codes: B62D 5/0472 for damping vibrations
• CPC Class Codes: B62D 6/10 characterised by means for sensing or determining torque
• CPC Class Codes: G01L 3/104 involving permanent magnets

Abstract

A driving control unit (21b) of a controller (21) determines which of an input shaft (32) and an output shaft (33) in a steering shaft (3) is dynamically superior and when the output shaft (33) is dynamically superior to the input shaft (32), a motor (6) is driven so that torque resulting in a time integral value smaller than a time integral value of relative torque between the input shaft (32) and the output shaft (33) is generated in a backward assist direction.

Claims

1. An electric power steering apparatus for applying rotation force of a motor to a steering system including a steering member and steering wheels for performing a steering assist, the power steering apparatus comprising:

an input shaft coupled to the steering member;

an output shaft;

a torsion bar coupling the input shaft to the output shaft;

an input shaft rotation detection unit for outputting a signal in response to rotation of the input shaft;

an output shaft rotation detection unit for outputting a signal in response to rotation of the output shaft;

a computation unit for obtaining information concerning torque transmitted between the input and output shafts and angular displacement with respect to each of the input and output shafts on the basis of outputs of the input shaft rotation detection unit and the output shaft rotation detection unit; and

a driving control unit for generating steering assist force by driving the motor in response to the torque transmitted between the input and output shafts, wherein the driving control unit determines which of the input shaft and the output shaft is dynamically superior based on the obtained information and when the output shaft is dynamically superior to the input shaft, the driving control unit controls the motor so that torque smaller than the torque transmitted between the input and output shafts is generated in a backward assist direction.

2. The electric power steering apparatus according to claim 1, wherein when the output shaft is dynamically superior to the input shaft, the driving control unit controls the motor so that torque resulting in a time integral value smaller than a time integral value of the torque transmitted between the input and output shafts is generated in a backward assist direction.

3. The electric power steering apparatus according to claim 1, wherein the information obtained by the computation unit includes angular speed and angular acceleration, and the determination made by the driving control unit is made based on either of the angular speed and the angular acceleration.

4. The electric power steering apparatus according to claim 1, wherein a waveform of torque generated in the backward assist direction is a damped oscillatory waveform.

5. An electric power steering apparatus for a steering system including a steering member and steering wheels comprising:

an input shaft coupled to the steering member;

an output shaft;

a torsion bar coupling the input shaft to the output shaft;

a first target plate made of magnetic material fixed to the input shaft, the first target plate having spur gear shape having a first predetermined number of teeth;

a second target plate made of magnetic material fixed to the output shaft, the second target plate having spur gear shape having the first predetermined number of teeth;

a third target plate made of magnetic material fixed to the output shaft, the third target plate having spur gear shape having a second predetermined number of teeth, in which the first predetermined number and the second predetermined number are mutually prime;

a first pair of magnetic sensors opposed to the first target plate;

a second pair of magnetic sensors opposed to the second target plate;

a third pair of magnetic sensors opposed to the third target plate; and

a computation unit for obtaining an absolute rotation position and a rotating direction of the output shaft based on outputs from the first, second and third magnetic sensors.