Microcontroller methods of improving reliability in DC brushless motors and cooling fans

• US 7,711,439 B2
• Filed: 05/03/2007
• Issued: 05/04/2010
• Est. Priority Date: 12/23/2004
• Status: Expired due to Fees

• Current Assignee: Minebea Mitsumi, Inc.
• Original Assignee: Minebea Company Limited (MinebeaMitsumi Inc.)
• Inventors: Hardt, Eric, Strike, Nigel D., Frankel, Scott
• Primary Examiner(s): Hartman, Jr.; Ronald D
• Application Number:
  US11/744,132
• Publication Number:
  US 20070219756A1
• Time in Patent Office: 1,097 Days
• Field of Search: 700299-300, 700/17, 700/83, 361/695, 361687-688, 702/96, 702/98, 702/132
• US Class Current: 700/17
• CPC Class Codes: H05K 7/20209 Thermal management, e.g. fan control

Abstract

A method of controlling a motor speed for a fan assembly includes receiving a duty cycle value at a microcontroller. The microcontroller receives a measured fan speed from a speed sensor. An expected fan speed is determined, where the expected fan speed corresponds to the duty cycle value. The measured fan speed is compared with the expected fan speed. A duty cycle of a motor driving signal is reduced if the measured fan speed is less than a predetermined fraction of the expected fan speed.

Claims

1. A method of monitoring operation of a cooling fan comprising:

obtaining a plurality of temperature measurements during operation of the cooling fan;

storing the plurality of temperature measurements in a memory;

storing information in a memory indicative of a cumulative number of revolutions of a motor of the cooling fan made over a period of time during operation of the cooling fan;

computing an estimated value indicative of a life of the cooling fan based on the cumulative number of revolutions of the motor and the temperature measurements including adjusting the cumulative number of revolutions using the temperature measurements;

displaying one or more messages when the estimated value of the life of the cooling fan exceeds a predetermined life of the cooling fan.

2. The method of claim 1 further comprising transmitting information stored in the memory to an external receiver.

3. The method of claim 2 wherein the transmitting is performed in response to retrieval by the external receiver.

4. The method of claim 1 further comprising modifying operation of the cooling fan based on some of the temperature measurements.

5. The method of claim 4 wherein modifying operation of the cooling fan is based on a comparison of said some of the temperature measurements with corresponding thresholds.

6. The method of claim 1 further comprising shutting down operation of the cooling fan based on the temperature measurements.

7. The method of claim 1 further comprising updating the number of revolutions of the motor as stored in the memory by a number of revolutions of the motor made during a second period of time.

8. The method of claim 1 further comprising updating the number of revolutions of the motor as stored in the memory by an adjusted number of revolutions of the motor made during a second period of time, wherein the adjusted number of revolutions of the motor is based on temperature measurements made during the second period of time.

9. A cooling fan comprising:

a fan unit comprising an impeller and a motor operatively coupled to the impeller;

a memory; and

a controller unit operatively coupled to the fan unit to operate the fan unit,

wherein the controller is configured to perform steps of;

obtaining a plurality of temperature measurements during operation of the cooling fan;

storing the plurality of temperature measurements in the memory;

storing in the memory a number of revolutions of the motor;

incrementing the number of revolutions of the motor during operation of the cooling fan so that the number of revolutions of the motor represents a total number of revolutions of the motor made over a period of time during operation of the cooling fan;

computing an estimated life of the cooling fan based on the number of revolutions of the motor and the plurality of temperature measurements, wherein the number of revolutions is adjusted based on the plurality of temperature measurements; and

displaying one or more messages when the estimated life of the cooling fan exceeds a predetermined life of the cooling fan.

10. The cooling fan of claim 9 further comprising a transmitter, the controller further configured to transmit one or more of the temperature measurements to an external receiver via the transmitter.

11. The method of claim 9 wherein the controller is further configured to modify an operation of the cooling fan based on some of the temperature measurements.

12. The method of claim 9 wherein the controller is further configured to transmit an error message based on a comparison of some of the temperature measurements with corresponding thresholds.

13. The method of claim 9 further wherein the controller is further configured to shut down operation of the cooling fan based on a comparison of some of the temperature measurements with corresponding thresholds.

14. The cooling fan of claim 9 wherein the controller is further configured to perform a step of updating the number of revolutions of the motor as stored in the memory by a number of revolutions of the motor made during a second period of time.

15. The cooling fan of claim 9 wherein the controller is further configured to perform a step of updating the number of revolutions of the motor as stored in the memory by an adjusted number of revolutions of the motor made during a second period of time, wherein the adjusted number of revolutions of the motor is based on temperature measurements made during the second period of time.

16. The cooling fan of claim 9 wherein the controller is further configured to perform a step of displaying one or more messages determined based on the temperature measurements and the number of revolutions of the motor.

17. The cooling fan of claim 9 wherein the controller is a microcontroller.

18. A cooling fan comprising:

an impeller;

a motor coupled to the impeller;

a temperature sensor;

a memory; and

a controller operatively coupled to the motor to operate the motor, the controller configured to;

receive temperature measurements during operation of the motor;

store the temperature measurements in the memory;

store a number of revolutions of the motor;

update the number so that the number is a cumulative number of revolutions of the motor made during operation of the motor;

compute an estimated life of the cooling fan based on the cumulative number of revolutions of the motor and the temperature measurements, wherein the cumulative number of revolutions is adjusted based on the temperature measurements; and

display one or more messages when the estimated life of the cooling fan exceeds a predetermined life of the cooling fan.

19. A method of monitoring operation of a cooling fan comprising storing a revolution count representative of the number of revolutions made by a motor of the cooling fan after a first period of time has elapsed, incrementing the revolution count after a second period of time has elapsed by a number of revolutions made by the motor of the cooling fan during the second period of time, wherein the revolution count indicates a cumulative count of the total number of revolutions made by the motor of the cooling fan.

20. The method of claim 19 further comprising producing an alert signal when the revolution count exceeds a predetermined number.

21. The method of claim 19 wherein the number of revolutions made by the motor during the second period of time is modified based on a temperature of the cooling fan during the second period of time, wherein the revolution count is incremented by the number of revolutions so modified.