Brushless motor and driving control device therefor

• US 6,469,463 B2
• Filed: 03/22/2001
• Issued: 10/22/2002
• Est. Priority Date: 03/22/2000
• Status: Active Grant

• Current Assignee: NSK Limited
• Original Assignee: NSK Limited
• Inventors: Endo, Shuji, Chen, Hui
• Primary Examiner(s): Ro, Bentsu
• Application Number:
  US09/814,181
• Publication Number:
  US 20020011811A1
• Time in Patent Office: 579 Days
• Field of Search: 318/138, 318/254, 318/439, 318/700, 318/721, 318/722, 318/801, 318/724
• US Class Current: 318/400.23
• CPC Class Codes: B62D 5/046 Controlling the motor
• CPC Class Codes: H02P 6/10 Arrangements for controlling torque ripple, e.g. providing reduced torque ripple
• CPC Class Codes: H02P 6/14 Electronic commutators

Abstract

There is provided a brushless motor and a driving control device therefor both of which can restrain the occurrence of current variations, torque variations and noise in the brushless motor, thereby constructing an electrically-operated power steering system of low noise and good steering feeling. In the driving control device for the brushless motor having a current variation rate control part which controls a current variation rate during commutation, and having plural excitation phases, the current variation rate control part terminates commutation transient time which is the time for which phase currents are in a transient state during a commutation operation, within ½ of commutation interval time which is the time required from the starting time of a certain commutation until the starting time of the next commutation.

Claims

1. A driving control device for a brushless motor having plural excitation phases, which device includes a current variation rate control part which controls a current variation rate during commutation, wherein the current variation rate control part terminates commutation transient time which is the time for which phase currents are in a transient state during a commutation operation, within {fraction (1/2)} of commutation interval time which is the time required for the starting time of a certain commutation until the starting time of the next commutation.

2. A driving control device for a brushless motor according to claim 1, wherein an electrical time constant of the brushless motor, which constant contains the impedance of a driving circuit, is {fraction (1/6)} or less of the commutation interval time.

3. A driving control device for a brushless motor according to claim 2, wherein the current variation rate control part limits the energization interval during which to supply a driving current for a fall phase of the commutation phase of an excitation coil.

4. A driving control device for a brushless motor according to claim 1, wherein the current variation rate control part limits the energization interval during which to supply a driving current for a fall phase of the commutation phase of an excitation coil.

5. A driving control device for a brushless motor according to claim 1 or 2, wherein the current variation rate control part controls the commutation transient time by executing commutation-phase current control by using a rotational speed of the brushless motor as a variable.

6. A driving control device for a brushless motor according to claim 5, wherein the current variation rate control part limits the energization interval during which to supply a driving current for a fall phase of the commutation phase of an excitation coil.

7. A driving control device for a brushless motor according to claim 1 or 2, wherein the current variation rate control part controls the commutation transient time by executing commutation-phase current control by using a rotational electrical angle of the brushless motor as a variable.

8. A driving control device for a brushless motor according to claim 7, wherein the current variation rate control part limits the energization interval during which to supply a driving current for a fall phase of the commutation phase of an excitation coil.