Electric motor control unit

• US 20030169007A1
• Filed: 02/19/2003
• Published: 09/11/2003
• Est. Priority Date: 02/19/2002
• Status: Active Grant

• Current Assignee: Nissan Motor Co., Ltd., Yazaki Corporation
• Original Assignee: Nissan Motor Co., Ltd., Yazaki Corporation
• Inventors: Nakayama, Makoto, Saito, Hironori, Ashiya, Hiroyuki
• Granted Patent: US 6,927,549 B2
• Time in Patent Office: Days
• US Class Current: 318/471
• CPC Class Codes: H02P 29/02 Providing protection against overload without automatic interruption of supply protection against faults of stepper motors H02P8/36
• CPC Class Codes: Y10S 388/934 Thermal condition

Abstract

An electric motor control unit mounted in an automotive vehicle has a motor (3) that is variable in its rotational speed. A temperature sensing element (18s) is arranged to contact a busbar so that relays (15b) and (15c) permit switching operation in response to detection of abnormal heat generation. This controls an electrical power supply to the motor to decrease the rotational speed of the motor without complete stopping of the motor. The rotational speed of the motor returns to a normal speed from the decreased speed by switching operation of the relays (15b) and (15c) with diminishing of the abnormal heat generation.

Claims

1. An electric motor control unit mounted in an automotive vehicle characterized in that the motor control unit comprises:

a motor supplied with an electrical power from a battery, the motor being variable in its rotational speed,

a temperature sensing element disposed at a position of the motor control unit where abnormal heat is generated due to overcurrent supplied to the motor, and

a rotational speed control means for reducing the rotational speed of the motor without stopping the motor based on detection of abnormal heat generation by the temperature sensing element.

2. The motor control unit according to the claim 1 characterized in that the motor is used for driving a cooling fan of a radiator.

3. The motor control unit according to the claim 2 characterized in that the rotational speed control means has a plurality of relays arranged between the battery and the motor, and at least one of the relays permits switching operation based on detection of abnormal heat generation to control an electrical power supplied to the motor so as to reduce the rotational speed of the motor.

4. The motor control unit according to the claim 3 characterized in that the motor has four terminals including three input terminals for changing the rotational speed of the motor to become any of high, middle, and low speeds by selecting on-off states of the three input terminals, and each of the relays is respectively connected to each of the three input terminals, wherein the relays can switch the on-off states of the input terminals based on detection of abnormal heat generation by the temperature sensing element so that the rotational speed of the motor can be changed from the high speed to the low speed.

5. The motor control unit according to the claim 3 characterized in that the motor has three terminals including two input terminals for changing the rotational speed of the motor to become any of high and low speeds by selecting on-off states of the two input terminals, and each of the relays is respectively connected to each of the two input terminals, wherein the relays can switch the on-off states of the input terminals based on detection of abnormal heat generation by the temperature sensing element to change the rotational speed of the motor from the high speed to the low speed.

6. The motor control unit according to the claim 3 characterized in that the motor has two terminals including one input terminal, the rotational speed of the motor being variable with current supplied to the input terminal, and two of the relays are connected to the input terminal for allowing the rotational speed of the motor to be variable, wherein the relays can perform switching operation based on detection of abnormal heat generation by the temperature sensing element to change the rotational speed of the motor to a lower one.

7. The motor control unit according to the claim 3 characterized in that at least one of relays operates to reduce the rotational speed of the motor when a temperature detected by the temperature sensing element is higher than a reference temperature showing abnormal heat generation, and the one of relays operates to return the rotational speed of the motor to a normal speed when a temperature detected by the temperature sensing element has become lower than the reference temperature.

8. The motor control unit according to the claim 7 characterized in that the one of relays operates to reduce the rotational speed of the motor when a temperature detected by the temperature sensing element is higher than the reference temperature, and the reduced speed of the motor is kept until a predetermined release command is given to the motor control unit.

9. The motor control unit according to the claim 3 characterized in that the temperature sensing element is a thermistor one end of which is grounded and the other end of which is connected to the one of relays, the thermistor having a resistance variable with its temperature, and the one of the relays performs switching operation in response to the thermistor resistance varied with abnormal heat generation of the motor.

10. The motor control unit according to the claim 9 characterized in that the thermistor has positive characteristics in which the resistance increases along a quadratic curve with increase of a temperature of the thermistor.

11. The motor control unit according to the claim 10 characterized in that the temperature sensing element contacts a busbar disposed between the battery and the motor to electrically connect thereto to detect a temperature of the busbar which is selected as the position for detecting abnormal heat generation.

12. An electric motor control unit mounted in an automotive vehicle, the motor control unit having a motor supplied with an electrical power from a battery, the motor being variable in its rotational speed,

the motor control unit comprises:

a temperature sensing means disposed at a position of the motor control unit where abnormal heat is generated due to overcurrent supplied to the motor, and

a rotational speed control means for reducing the rotational speed of the motor without stopping the motor based on detection of abnormal heat generation by the temperature sensing means.