Method of controlling a variable speed fan

• US 6,453,853 B1
• Filed: 12/04/2000
• Issued: 09/24/2002
• Est. Priority Date: 12/04/2000
• Status: Expired due to Fees

• Current Assignee: Detroit Diesel Corporation (Mercedes-Benz Group AG)
• Original Assignee: Detroit Diesel Corporation (Mercedes-Benz Group AG)
• Inventors: Hawkins, Jeffery Scott, Blake, Charles C., Mikulik, Ronald William, Weisman, Steve Miller
• Primary Examiner(s): Wolfe, Willis R.
• Assistant Examiner(s): Benton, Jason
• Application Number:
  US09/729,610
• Publication Number:
  US 20020066422A1
• Time in Patent Office: 659 Days
• Field of Search: 123/41.12, 123/41.11, 123/41.49
• US Class Current: 123/41.12
• CPC Class Codes: F01P 2023/08 Microprocessor; Microcomputer
• CPC Class Codes: F01P 2025/04 Pressure
• CPC Class Codes: F01P 2025/40 Oil temperature
• CPC Class Codes: F01P 2025/48 Engine room temperature
• CPC Class Codes: F01P 2031/00 Fail safe
• CPC Class Codes: F01P 7/044 using hydraulic drives
• CPC Class Codes: F01P 7/048 using electrical drives
• CPC Class Codes: F02D 2200/0414 Air temperature

Abstract

Various control strategies and techniques for controlling a variable speed fan in an internal combustion engine are provided. The various control techniques improve fuel economy by operating the fan at a speed sufficient to cool the engine, while avoiding unnecessarily higher speeds that result in poor fuel economy. Further, the fan may be completely disabled at cold start up to avoid over cooling, particularly in an engine using a charge air cooling system.

Claims

1. A method of control an internal combustion engine, the engine including a variable speed fan, the variable speed fan being driven in response to an applied fan request signal having a value between a predetermined maximum fan request value and a predetermined minimum fan request value, the engine being operable over an engine speed range between an idle speed and a full speed, the method comprising:

establishing a fan speed limit as a maximum allowable fan speed during operation of the engine at all engine speeds in the engine speed range;

determining an initial fan request signal based on engine operating conditions and having a value between the minimum fan request value and the maximum fan request value, wherein the maximum fan request value is sufficiently large to cause the fan speed to approach the fan speed limit as the engine speed approaches an intermediate speed between the idle speed and the full speed; and

determining the applied fan request signal by limiting the initial fan request signal based on engine speed such that the fan speed approaches the fan speed limit as the engine speed approaches the intermediate speed and the fan speed remains below the fan speed limit as the engine speed approaches the full speed, while the initial fan request signal value is the maximum fan request value, allowing higher fan speeds at lower engine speeds while avoiding fan overspeed at higher engine speeds.

2. The method of claim 1 further comprising:

monitoring the fan speed; and

limiting engine speed, as needed, to prevent the applied fan request signal from causing the fan speed to exceed the fan speed limit.

3. The method of claim 1 wherein determining the initial fan request signal further comprises:

determining a plurality of preliminary initial fan request signals, each request signal having a value based on at least one engine condition; and

determining the initial fan request signal as the preliminary fan request signal having the greatest value.

4. The method of claim 1 wherein the variable speed fan is a hydraulically driven fan wherein hydraulic oil is pumped by a pump to drive a hydraulic fan motor.

5. A method of controlling an internal combustion engine, the engine including a hydraulically driven variable speed fan wherein hydraulic oil is pumped by a pump to drive a hydraulic fan motor, the variable speed fan being driven in response to an applied fan request signal having a value between a maximum fan request value and a minimum fan request value, the engine being operable over an engine speed range between an idle speed and a full speed, the method comprising:

establishing a hydraulic oil threshold temperature for the hydraulic oil that drives the fan motor;

monitoring a temperature of the hydraulic oil;

determining an initial fan request signal having a value between the minimum fan request value and the maximum fan request value; and

determining the applied fan request signal as the initial fan request signal when the oil temperature falls below the oil threshold temperature, and determining the applied fan request signal as a modified fan request signal having a value greater than the initial fan request signal value to compensate for losses due to increased hydraulic oil temperature when the oil temperature exceeds the oil threshold temperature.

6. The method of claim 5 wherein determining the applied fan request signal further comprises:

determining a multiplier; and

determining the applied fan request signal as a modified fan request signal having a value that is a product of the multiplier and the initial fan request signal value when the oil temperature exceeds the oil threshold temperature.

7. The method of claim 5 wherein determining the applied fan request signal further comprises:

determining an adder; and

determining the applied fan request signal as a modified fan request signal having a value that is a sum of the adder and the initial fan request signal value when the oil temperature exceeds the oil threshold temperature.

8. A method of controlling an internal combustion engine, the engine being housed in an engine compartment and including a hydraulically driven variable speed fan wherein hydraulic oil is pumped by a pump to drive a hydraulic fan motor, the variable speed fan being selectively driven in response to an applied fan request signal based on engine operating conditions having a value between a maximum fan request value and a minimum fan request value, the engine being operable over an engine speed range between an idle speed and a full speed, the method comprising:

establishing an engine compartment temperature threshold;

monitoring a temperature in the engine compartment;

in the presence of the applied fan request signal, driving the hydraulic fan motor with the pump to drive the fan in accordance with the applied fan request signal; and

in the absence of the applied fan request signal, effectively disabling the fan when the temperature falls below the threshold, and otherwise, driving the hydraulic fan motor with the pump to drive the fan at a predetermined speed.

9. The method of claim 8 wherein the pump is a variable displacement pump and wherein effectively disabling the fan further comprises:

controlling the pump so that there is not any effective pump displacement.

10. The method of claim 8 where in effectively disabling the fan further comprises:

providing a bypass such that hydraulic oil that is pumped by the pump bypasses the hydraulic fan motor so that there is not any effective drive to the fan motor.

11. The method of claim 8 wherein the engine compartment temperature is an engine compartment air temperature.

12. The method of claim 11 wherein the engine compartment temperature is an intake manifold air temperature.

13. A method of-controlling an internal combustion engine in a vehicle having a transmission, the engine including a variable speed fan and the transmission including transmission oil, the variable speed fan being driven in response to an applied fan request signal based on engine conditions having a value between a maximum fan request value and a minimum fan request value, the engine being operable over an engine speed range between an idle speed and a full speed, the method comprising:

establishing a transmission oil threshold temperature for the transmission oil;

monitoring a temperature of the transmission oil;

determining a plurality of preliminary initial fan request signals, each request signal having a value based on at least one engine condition, wherein a transmission oil initial fan request signal is based on the transmission oil temperature and the threshold temperature; and

determining the applied fan request signal as the initial fan request signal with the greatest value.

14. The method of claim 13 wherein the transmission has an oil sump and wherein monitoring the temperature of the transmission oil further comprises:

monitoring the temperature of the transmission oil at the transmission oil sump.

15. A method of controlling an internal combustion engine in a vehicle having an air conditioning system, the engine including a variable speed fan and the air conditioning system including a condenser for transferring heat from a refrigerant during operation, the variable speed fan being driven in response to an applied fan request signal based on engine conditions and having a value between a maximum fan request value and a minimum fan request value, the engine being operable over an engine speed range between an idle speed and a full speed, the method comprising:

establishing a condenser threshold pressure;

monitoring a pressure in the condenser;

determining a plurality of preliminary initial fan request signals, each request signal having a value based on at least one engine condition, wherein a condenser initial fan request signal is based on the condenser pressure and the threshold pressure; and

determining the applied fan request signal as the initial fan request signal with the greatest value.

16. A computer readable storage medium having instructions stored thereon that are executable by a controller to perform a method of controlling an internal combustion engine, the engine including a variable speed fan, the variable speed fan being driven in response to an applied fan request signal having a value between a predetermined maximum fan request value and a predetermined minimum fan request value, the engine being operable over an engine speed range between an idle speed and a full speed, the medium further comprising:

instructions for establishing a fan speed limit as a maximum allowable fan speed during operation of the engine at all engine speeds in the engine speed range;

instructions for determining an initial fan request signal based on engine operating conditions and having a value between the minimum fan request value and the maximum fan request value, wherein the maximum fan request value is sufficiently large to cause the fan speed to approach the fan speed limit as the engine speed approaches an intermediate speed between the idle speed and the full speed; and

instructions for determining the applied fan request signal by limiting the initial fan request signal based on engine speed such that the fan speed approaches the fan speed limit as the engine speed approaches the intermediate speed and the fan speed remains below the fan speed limit as the engine speed approaches the full speed, while the initial fan request signal value is the maximum fan request value, allowing higher fan speeds at lower engine speeds while avoiding fan overspeed at higher engine speeds.

17. The medium of claim 16 further comprising:

instructions for monitoring the fan speed; and

instructions for limiting engine speed, as needed, to prevent the applied fan request signal from causing the fan speed to exceed the fan speed limit.

18. The medium of claim 16 wherein the instructions for determining the initial fan request signal further comprise:

instructions for determining a plurality of preliminary initial fan request signals, each request signal having a value based on at least one engine condition; and

instructions for determining the initial fan request signal as the preliminary fan request signal having the greatest value.

19. The medium of claim 16 wherein the variable speed fan is a hydraulically driven fan wherein hydraulic oil is pumped by a pump to drive a hydraulic fan motor.

20. A computer readable storage medium having instructions stored thereon that are executable by a controller to perform a method of controlling an internal combustion engine, the engine including a hydraulically driven variable speed fan wherein hydraulic oil is pumped by a pump to drive a hydraulic fan motor, the variable speed fan being driven in response to an applied fan request signal having a value between a maximum fan request value and a minimum fan request value, the engine being operable over an engine speed range between an idle speed and a full speed, the medium further comprising:

instructions for establishing a hydraulic oil threshold temperature for the hydraulic oil that drives the fan motor;

instructions for monitoring a temperature of the hydraulic oil;

instructions for determining an initial fan request signal having a value between the minimum fan request value and the maximum fan request value; and

instructions for determining the applied fan request signal as the initial fan request signal when the oil temperature falls below the oil threshold temperature, and determining the applied fan request signal as a modified fan request signal having a value greater than the initial fan request signal value to compensate for losses due to increased hydraulic oil temperature when the oil temperature exceeds the oil threshold temperature.

21. The medium of claim 20 wherein the instructions for determining the applied fan request signal further comprise:

instructions for determining a multiplier; and

instructions for determining the applied fan request signal as a modified fan request signal having a value that is a product of the multiplier and the initial fan request signal value when the oil temperature exceeds the oil threshold temperature.

22. The medium of claim 20 wherein the instructions for determining the applied fan request signal further comprise:

instructions for determining a adder; and

instructions for determining the applied fan request signal as a modified fan request signal having a value that is a sum of the adder and the initial fan request signal value when the oil temperature exceeds the oil threshold temperature.

23. A computer readable storage medium having instructions stored thereon that are executable by a controller to perform a method of controlling an internal combustion engine, the engine being housed in an engine compartment and including a hydraulically driven variable speed fan wherein hydraulic oil is pumped by a pump to drive a hydraulic fan motor, the variable speed fan being selectively driven in response to an applied fan request signal based on engine operating conditions having a value between a maximum fan request value and a minimum fan request value, the engine being operable over an engine speed range between an idle speed and a full speed, the medium further comprising:

instructions for establishing an engine compartment temperature threshold;

instructions for monitoring a temperature in the engine compartment;

instructions for, in the presence of the applied fan request signal, driving the hydraulic fan motor with the pump to drive the fan in accordance with the applied fan request signal; and

instructions for, in the absence of the applied fan request signal, effectively disabling the fan when the temperature falls below the threshold, and otherwise, driving the hydraulic fan motor with the pump to drive the fan at a predetermined speed.

24. The medium of claim 23 wherein the pump is a variable displacement pump and wherein the instructions for effectively disabling the fan further comprise:

instructions for controlling the pump so that there is not any effective pump displacement.

25. The medium of claim 23 wherein the instructions for effectively disabling the fan further comprise:

instructions for providing a bypass such that hydraulic oil that is pumped by the pump bypasses the hydraulic fan motor so that there is not any effective drive to the fan motor.

26. The medium of claim 23 wherein the engine compartment temperature is an engine compartment air temperature.

27. The medium of claim 26 wherein the engine compartment temperature is an intake manifold air temperature.

28. A computer readable storage medium having instructions stored thereon that are executable by a controller to perform a method of controlling an internal combustion engine in a vehicle having a transmission, the engine including a variable speed fan and the transmission including transmission oil, the variable speed fan being driven in response to an applied fan request signal based on engine conditions having a value between a maximum fan request value and a minimum fan request value, the engine being operable over an engine speed range between an idle speed and a full speed, the medium further comprising:

instructions for establishing a transmission oil threshold temperature for the transmission oil;

instructions for monitoring a temperature of the transmission oil;

instructions for determining a plurality of preliminary initial fan request signals, each request signal having a value based on at least one engine condition, wherein a transmission oil initial fan request signal is based on the transmission oil temperature and the threshold temperature; and

instructions for determining the applied fan request signal as the initial fan request signal with the greatest value.

29. The medium of claim 28 wherein the transmission has an oil sump and wherein the instructions for monitoring the temperature of the transmission oil further comprise:

instructions for monitoring the temperature of the transmission oil at the transmission oil sump.

30. A computer readable storage medium having instructions stored thereon that are executable by a controller to perform a method of controlling an internal combustion engine in a vehicle having an air conditioning system, the engine including a variable speed fan and the air conditioning system including a condenser for transferring heat from a refrigerant during operation, the variable speed fan being driven in response to an applied fan request signal based on engine conditions and having a value between a maximum fan request value and a minimum fan request value, the engine being operable over an engine speed range between an idle speed and a full speed, the medium further comprising:

instructions for establishing a condenser threshold pressure;

instructions for monitoring a pressure in the condenser;

instructions for determining a plurality of preliminary initial fan request signals, each request signal having a value based on at least one engine condition, wherein a condenser initial fan request signal is based on the condenser pressure and the threshold pressure; and

instructions for determining the applied fan request signal as the initial fan request signal with the greatest value.