Motor drive unit and method of detecting malfunction of motor drive unit

• US 6,335,600 B1
• Filed: 09/06/2000
• Issued: 01/01/2002
• Est. Priority Date: 09/07/1999
• Status: Expired due to Fees

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Fujita, Shuji, Kasai, Eiji
• Primary Examiner(s): Dang, Khanh
• Application Number:
  US09/655,916
• Time in Patent Office: 482 Days
• Field of Search: 318/254, 318/139, 318/798-805, 318/812, 318/434, 318/811, 388/903
• US Class Current: 318/434
• CPC Class Codes: B62D 5/0487 detecting motor faults B62D5/0496 takes precedence
• CPC Class Codes: H02H 7/0838 with H-bridge circuit
• CPC Class Codes: H02P 7/0094 wherein the position is detected using the ripple of the current caused by the commutator
• CPC Class Codes: H02P 7/04 by means of a H-bridge circuit
• CPC Class Codes: Y10S 388/903 Protective, e.g. voltage or current limit

Abstract

A DC motor is connected to diagonal positions of a bridge circuit having of four sides including switching elements and reflux diodes. At least one of two terminals is connected to a power line, and at least the other terminal is grounded. By performing pulse width modulation control of the switching elements, operation of the DC motor is controlled. When the DC motor is in operation, the sum of the terminal voltages of the DC motor is equal to the power voltage. When the DC motor is out of operation, the sum of the voltages is set to a predetermined voltage. If the sum of the voltages has deviated from the power voltage or the predetermined voltage by at least a predetermined value, the occurrence of a malfunction is judged.

Claims

1. A motor drive unit, comprising:

a bridge circuit having four sides that each have a switching element;

an electric motor having two ends connected to the bridge circuit;

a motor drive device which operates the electric motor by connecting one of the switching elements to a power line and grounding an other one of the switching elements and which controls the electric motor by performing pulse width modulation control of the switching elements; and

a malfunction judgment controller which judges the occurrence of a malfunction in at least one of the bridge circuit, the electric motor and the motor drive device when a sum of respective voltages at the two ends of the electric motor is different from a first predetermined value set based on a power voltage by a second predetermined value or more during operation of the electric motor.

2. The motor drive unit according to claim 1, further comprising:

a current detection controller which detects a current flowing through the electric motor; and

an operation judgment controller which judges, based on the detected current, whether the electric motor is in operation or out of operation.

3. The motor drive unit according to claim 1, further comprising:

a continuation detection controller which detects whether or not the malfunction judgment device continuously judges the occurrence of a malfunction; and

a failure processing controller which performs failure processing if the malfunction continues for a predetermined period.

4. The motor drive unit according to claim 3, wherein:

the failure processing includes at least one of stopping operating the electric motor, issuing a warning, and recording a type of the malfunction as a diagnosis code.

5. A motor drive unit, comprising:

a bridge circuit having four sides that each have a switching element;

an electric motor having two ends connected to the bridge circuit;

a motor drive device which operates the electric motor by connecting one of the switching elements to a power line and grounding an other one of the switching elements and which controls the electric motor by performing pulse width modulation control of the switching elements; and

a malfunction judgment controller which judges the occurrence of a malfunction in at least one of the bridge circuit, the electric motor and the motor drive device when the electric motor is out of operation by judging when a sum of respective voltages at the two ends of the electric motor is different from a first predetermined value set based on a power voltage by a second predetermined value or more, wherein the sum of respective voltage values are determined in advance based on the voltage values at the two ends of the electric motor during a turned-off state when operating normally.

6. The motor drive unit according to claim 5, further comprising:

a current detection controller which detects a current flowing through the electric motor; and

an operation judgment controller which judges, based on the detected current, whether the electric motor is in operation or out of operation.

7. The motor drive unit according to claim 5, further comprising:

a continuation detection controller which detects whether or not the malfunction judgment device continuously judges the occurrence of a malfunction; and

a failure processing controller which performs a failure processing if the malfunction continues for a predetermined period.

8. The motor drive unit according to claim 7, wherein:

the failure processing includes at least one of stopping operating the electric motor, issuing a warning, and recording a type of the malfunction as a diagnosis code.

9. A motor drive unit, comprising:

a bridge circuit having four sides that each have a switching element;

an electric motor having two ends connected to the bridging circuit;

a motor drive device which operates the electric motor by connecting one of switching elements to a power line and grounding an other one of the switching elements and which controls the electric motor by performing pulse width modulation control of the switching elements; and

a circuit which sets terminal voltages at the two ends of the electric motor to a lower power voltage during a turned-off state of all the switching elements, wherein the circuit comprises;

a pull-up resistor connected to at least one of the two ends of the electric motor and to the power line; and

a pull-down resistor connected to at least the other of the two ends of the electric motor and to the ground; and

a malfunction judgment controller which judges the occurrence of a malfunction in at least one of the bridge circuit, the electric motor and the motor drive device when a sum of the respective voltages at the ends of the electric motor is different from a first predetermined value s et based on a power voltage by a second predetermined value or more during operation of the electric motor.

10. The motor drive unit according to claim 9, further comprising:

a continuation detection controller which detects whether or not the malfunction judgment device continuously judges the occurrence of a malfunction; and

a failure processing controller which performs a failure processing if the judgment of the occurrence of the malfunction continues for a predetermined period.

11. The motor drive unit according to claim 10, wherein:

the failure processing includes at least one of stopping operating the electric motor, issuing a warning, and recording a detected state of the malfunction as a diagnosis code.

12. A method of detecting a malfunction for a motor drive unit having a bridge circuit having four sides that each have a switching element, an electric motor having at ends connected to the bridge circuit, a power circuit which operates the electric motor by connecting one of the switching elements to a power line and grounding an other one of the switching elements, and a motor drive device which controls the electric motor by performing pulse width modulation control of the switching elements, comprising the steps of:

detecting a sum of the voltages at the switching elements of the electric motor; and

judging the occurrence of a malfunction in at least one of the bridge circuit, the electric motor and the motor drive device if the sum of respective voltages at the two ends of the electric motor is different from a first predetermined value set based on a power voltage by a second predetermined value or more during operation of the electric motor.

13. A method of detecting a malfunction for a motor drive unit having a bridge circuit having four sides that each have a switching element, an electric motor having two ends connected to the bridge circuit, a power circuit which operates the electric motor by connecting one of the switching elements to a power line and grounding an other one of the switching elements, and a motor drive device which controls the electric motor by performing pulse width modulation control of the switching elements, comprising the steps of:

detecting a sum of the voltages at the two ends of the electric motor; and

judging the occurrence of a malfunction in at least one of the bridge circuit, the electric motor and the motor drive device, when the electric motor is out of operation, if the detected sum of respective voltages is different from a first predetermined value set based on a power voltage at the power line by a second predetermined value or more, wherein the sum of voltage values are determined in advance based on the voltage values at the two ends of the electric motor during a turned-off state.

14. A method of detecting a malfunction for a motor drive unit having a bridge circuit having four sides that each have a switching element, an electric motor having two ends connected to the bridge circuit, a power circuit which operates the electric motor by connecting one of the switching elements to a power line and grounding an other one of the switching elements, and a motor drive device which controls the electric motor by performing pulse width modulation control of the switching elements, comprising the steps of:

setting terminal voltages at the two ends of the electric motor to a lower power voltage during a turned-off state of all the switching elements by connecting at least one of the two ends of the electric motor to the power line through a pull-up resistor and grounding at least one of the other of the two ends of the electric motor through a pull-down resistor;

detecting a sum of the voltages at the switching elements of the electric motor; and

judging the occurrence of a malfunction in at least one of the bridge circuit, the electric motor and the motor drive device if a sum of the respective terminal voltages of the electric motor is different from a first predetermined value set based on a power voltage by a second predetermined value or more.