Granted Patent B2

US 8,068,966 · App. 12/249,563 · Granted Nov 29, 2011

Abstract

Claims (24)

1. A method for monitoring a powertrain system including a hybrid transmission coupled to an engine selectively operative in engine-on and engine-off states during ongoing operation of the powertrain system and including an auxiliary hydraulic pump selectively operative to pump hydraulic fluid in a hydraulic circuit of the hybrid transmission, the method comprising:

monitoring a plurality of enable criteria;

commanding the auxiliary hydraulic pump to operate at a predetermined speed only when all the enable criteria are met;

monitoring an operating speed of the auxiliary hydraulic pump;

comparing the commanded speed and the monitored operating speed of the auxiliary hydraulic pump; and

inhibiting the engine-off state based upon a difference between the commanded speed and the monitored operating speed of the auxiliary hydraulic pump.

2. The method of claim 1 , wherein the enable criteria comprise the engine in an engine-off state, the powertrain system in a key-on state, the auxiliary hydraulic pump in an enabled state, the auxiliary hydraulic pump in an available state, and a temperature of the hydraulic fluid within a predetermined range.

3. The method of claim 2 , wherein the enable criteria comprising the temperature of the hydraulic fluid within a predetermined range includes a minimum temperature threshold and a maximum temperature threshold.

4. The method of claim 3 , wherein the minimum temperature threshold and the maximum temperature threshold each include temperature hysteresis.

5. The method of claim 1 , comprising inhibiting the engine-off state when the difference between the commanded speed and the monitored operating speed of the auxiliary hydraulic pump exceeds a predetermined threshold.

6. The method of claim 5 , further comprising identifying a speed performance fault when the difference between the commanded speed and the monitored operating speed of the auxiliary hydraulic pump exceeds the predetermined threshold.

7. The method of claim 6 , monitoring the speed performance faults, and detecting an auxiliary pump fault when a predetermined number of speed performance faults have occurred.

8. The method of claim 7 , further comprising inhibiting engine operation in the engine-off state when an auxiliary pump fault has been detected.

9. The method of claim 1 , further comprising permitting the engine-off state after a predetermined elapsed time subsequent to inhibiting the engine-off state.

10. The method of claim 9 , further comprising inhibiting the engine-off state until a key-on event after a predetermined number of cycles of permitting and inhibiting the engine-off state.

11. A method for monitoring a powertrain system including a hybrid transmission connected to an engine selectively operative in engine-on and engine-off states during ongoing operation of the powertrain system and including an auxiliary hydraulic pump selectively operative to pump hydraulic fluid in the hybrid transmission, the method comprising:

monitoring the engine state;

commanding the auxiliary hydraulic pump to operate at a predetermined speed when the engine is operated at the engine-off state;

monitoring hydraulic pressure in the hybrid transmission;

determining an operating speed of the auxiliary hydraulic pump based upon the monitored hydraulic pressure;

comparing the commanded speed and the determined operating speed of the auxiliary hydraulic pump; and

inhibiting the engine-off state when the a difference between the commanded speed and the determined operating speed of the auxiliary hydraulic pump exceeds a predetermined threshold.

12. The method of claim 11 , comprising determining the predetermined threshold based upon a temperature of the hydraulic fluid.

13. The method of claim 11 , further comprising permitting the engine-off state after an elapsed time period.

Assignments (17)