METHOD AND APPARATUS TO CONTROL CLUTCH PRESSURES IN AN ELECTRO-MECHANICAL TRANSMISSION

• US 20090112429A1
• Filed: 10/08/2008
• Published: 04/30/2009
• Est. Priority Date: 10/26/2007
• Status: Active Grant

• Current Assignee: Bayerische Motoren Werke AG, Daimler AG (Mercedes-Benz Group AG), Chrysler Group LLC (Stellantis NV)
• Original Assignee: GM Global Technology Operations Incorporated (General Motors Company)
• Inventors: NAQVI, ALI K., SAH, JY-JEN F.
• Granted Patent: US 8,560,191 B2
• Time in Patent Office: Days
• US Class Current: 701/68
• CPC Class Codes: F16H 2057/014 of friction elements in transmissions
• CPC Class Codes: F16H 2059/465 Detecting slip, e.g. clutch slip ratio
• CPC Class Codes: F16H 57/01 Monitoring wear or stress of gearing elements, e.g. for triggering maintenance
• CPC Class Codes: F16H 61/061 using electric control means

Abstract

A method for reducing occurrence of clutch slip in electromechanical transmission adapted to selectively transmit mechanical power to an output member through selective application of a hydraulically actuated clutch includes monitoring operation of said clutch, identifying an indication of clutch wear based upon said monitoring said operation, and increasing a minimum clamping force applied to said clutch based upon said indication of clutch wear.

Claims

1. Method for reducing occurrence of clutch slip in electro-mechanical transmission adapted to selectively transmit mechanical power to an output member through selective application of a hydraulically actuated clutch, said method comprising:

monitoring operation of said clutch;

identifying an indication of clutch wear based upon said monitoring said operation; and

increasing a minimum clamping force applied to said clutch based upon said indication of clutch wear.

2. The method of claim 1,

wherein monitoring said operation of said clutch comprises monitoring a slip speed of said clutch;

and

wherein identifying said indication of clutch wear comprises identifying a significant clutch slip event based upon said monitoring said slip speed.

3. The method of claim 2, wherein identifying said significant clutch slip event comprises:

indicating a clutch slip event if said slip speed exceeds a threshold slip magnitude; and

identifying said clutch slip event as significant if said slip speed remains in excess of said threshold slip magnitude throughout a threshold slip duration.

4. The method of claim 1, wherein increasing said minimum clamping force applied to said clutch comprises maintaining an increased minimum hydraulic line pressure.

5. The method of claim 4, wherein said increasing said minimum hydraulic line pressure comprises increasing a minimum offset hydraulic line pressure by an incremental increase.

6. The method of claim 4,

wherein monitoring said operation of said clutch comprises monitoring a slip speed of said clutch,

wherein said identifying said indication of clutch wear comprises identifying a significant clutch slip event based upon said monitoring said slip speed, and

further comprising when said significant clutch slip event is identified, initiating a remediation event comprising

increasing a hydraulic line pressure to a maximum pressure, and

when said slip speed is less than a threshold slip magnitude, decreasing said hydraulic line pressure to said increased minimum hydraulic line pressure.

7. The method of claim 6, wherein decreasing said hydraulic line pressure comprises utilizing a series of incrementally stepped down reductions in said hydraulic line pressure.

8. The method of claim 7, wherein initiating said remediation event further comprises:

if said slip speed exceeds said threshold slip magnitude during said decreasing said hydraulic line pressure, initiating a slip reoccurrence recovery cycle comprising;

increasing said hydraulic line pressure by a recovery increase;

monitoring slip speed through a threshold recovery duration after said incrementally increasing said hydraulic line pressure;

if said monitoring slip speed indicates that said slip speed is reduced less to than said threshold slip magnitude by the end of said threshold recovery duration, maintaining said hydraulic line pressure to at least a level set by said recovery increase; and

if said monitoring slip speed indicates that said slip speed is not reduced less to than said threshold slip magnitude by the end of said threshold recovery duration, reinitiating said remediation event.

9. Method for controlling hydraulic line pressure in electromechanical transmission adapted to selectively transmit mechanical power to an output member through selective application of a hydraulically actuated clutch, the method comprising:

monitoring slip speed in said clutch;

identifying a significant clutch slip event based upon said monitoring said slip speed; and

maintaining an increased minimum offset hydraulic line pressure based upon said identifying said significant clutch slip event.

10. The method of claim 9, wherein identifying said significant clutch slip event comprises:

indicating a clutch slip event if said slip speed exceeds a threshold slip magnitude; and

identifying said clutch slip event as significant if said slip speed remains in excess of said threshold slip magnitude throughout a threshold slip duration.

11. The method of claim 9, wherein maintaining said increased minimum offset hydraulic line pressure includes a fixed incremental increase.

12. The method of claim 9, wherein maintaining said increased minimum offset hydraulic line pressure includes an increase scaled to a magnitude of said significant clutch slip event.

13. The method of claim 9, further comprising:

when said significant clutch slip event is identified, initiating a remediation event comprising

increasing an offset hydraulic line pressure to a maximum pressure, and

when said slip speed is less than a threshold slip magnitude, decreasing said offset hydraulic line pressure to said increased minimum hydraulic line pressure.

14. The method of claim 13, wherein decreasing said offset hydraulic line pressure comprises utilizing a series of incrementally stepped down reductions in said offset hydraulic line pressure.

15. The method of claim 14, wherein said initiating said remediation event further comprises:

if said slip speed exceeds said threshold slip magnitude during said decreasing said offset hydraulic line pressure, reinitiating said remediation event.

16. Apparatus for reducing occurrence of clutch slip in an electro-mechanical transmission adapted to selectively transmit mechanical power to an output member through selective application of a hydraulically actuated clutch, said apparatus comprising:

said clutch including means to monitor clutch slip;

an electrically-powered auxiliary hydraulic pump;

an auxiliary hydraulic pump control module; and

an offset pressure module providing input to said auxiliary hydraulic pump control module, wherein said offset pressure module is programmed with logic comprising

a monitoring of said clutch slip,

an indication of a significant clutch slip event based upon said monitoring, and

a modulation of a hydraulic line pressure comprising an increased minimum hydraulic line pressure based upon said indication of said significant clutch slip event.

17. The apparatus of claim 16, wherein modulation of said line pressure further comprises:

a boost in said hydraulic line pressure to a maximum line pressure; and

after said clutch slip is significantly reduced, a reduction of said hydraulic line pressure in stepped increments to said increased minimum hydraulic line pressure.