Fluid pump speed control

1. A system comprising:

a fluid sump;

a torque-limited fluid pump having a calibrated steady-state speed, wherein the torque-limited fluid pump draws fluid from the fluid sump and circulates the fluid under pressure;

a component that receives the fluid that is circulated by the torque-limited fluid pump;

a temperature sensor positioned with respect to the fluid sump and configured to measure a temperature of the fluid in the fluid sump; and

a controller having a processor and a tangible, non-transitory storage medium on which is recorded instructions for controlling the speed of the torque-limited fluid pump;

wherein the controller is configured to:

detect a soak condition of the component using the measured temperature;

calculate a speed of the torque-limited fluid pump as a function of the calibrated steady-state speed and a calibrated overspeed value; and

command the calculated speed from the torque-limited fluid pump for a calibrated duration only when the soak condition is detected.

2. The system of claim 1 , wherein the controller is further configured to reduce the speed of the torque-limited fluid pump to the calibrated steady-state speed after the calibrated duration has elapsed.

3. The system of claim 1 , wherein the calibrated duration is determined by the controller as a linear function of the measured fluid temperature.

4. The system of claim 3 , wherein the calibrated duration at a measured temperature of 0° C. is less than about 5 s, and wherein the calibrated duration at a measured temperature of −40° C. is less than about 30 s.

5. The system of claim 1 , further comprising a direct current (DC) power supply, wherein the torque-limited fluid pump is an electric fluid pump that is driven via electricity supplied by the DC power supply.

6. The system of claim 5 , further comprising a power inverter module that is electrically connected to the DC power supply, wherein the torque-limited fluid pump is electrically connected to the power inverter module.

7. The system of claim 1 , wherein the component is a vehicle transmission, and wherein the torque-limited fluid pump is a transmission pump.

8. The system of claim 1 , wherein the calibrated overspeed value is approximately equal to the calibrated steady-state speed.

9. A method comprising:

measuring a temperature of a fluid in a fluid sump of a transmission using a temperature sensor;

detecting a soak condition of the transmission by comparing, via a controller, the measured fluid temperature to a threshold temperature;

calculating a pump speed of a torque-limited fluid pump as a function of a steady-state speed of the torque-limited fluid pump and a calibrated overspeed value during the soak condition;

temporarily increasing the steady-state speed of the torque-limited fluid pump for a calibrated duration only when the soak condition is detected; and

reducing the speed of the torque-limited fluid pump to the steady-state speed after the calibrated duration has elapsed.

10. The method of claim 9 , further comprising:

recording the calibrated overspeed value and the calibrated duration, indexed by different fluid temperatures, in a lookup table that is accessible by the controller.

11. The method of claim 10 , further comprising:

electrically connecting the torque-limited fluid pump to a power inverter module in a vehicle; and

using the electrically-connected torque-limited fluid pump to deliver the fluid to a vehicle transmission.

12. The method of claim 9 , wherein the calibrated overspeed value is approximately equal to the steady-state speed.

13. A system for controlling a torque-limited fluid pump, the system comprising:

a processor in communication with the torque-limited fluid pump; and

tangible, non-transitory storage medium in communication with the processor, and on which is recorded a steady-state speed of the torque-limited fluid pump, a lookup table, and instructions for controlling the speed of the torque-limited fluid pump;

wherein the processor is configured to execute the instructions from the storage medium to thereby:

receive a measured fluid temperature describing a temperature of a supply of fluid circulated via the torque-limited fluid pump;

read the steady-state speed of the torque-limited fluid pump from the storage medium;

extract, from the lookup table, a calibrated overspeed value and a calibrated duration corresponding to the measured fluid temperature; and

temporarily increase the steady-state speed of the torque-limited fluid pump by adding a calibrated overspeed value to the steady-state speed, for a calibrated duration, until the measured fluid temperature exceeds a temperature threshold.

14. The system of claim 13 , wherein the processor is further configured to reduce the speed of the torque-limited fluid pump to the steady state speed after the calibrated duration has elapsed.

15. The system of claim 14 , further comprising:

a temperature sensor positioned with respect to the fluid sump and configured to measure the fluid temperature in proximity to the fluid sump.

16. The system of claim 14 , wherein the processor linearly increases the calibrated duration between a measured temperature of −10° C. and a measured temperature of −40° C.

17. The system of claim 14 , wherein the processor is a component of a hybrid vehicle controller and the torque-limited fluid pump is an electric pump for a vehicle transmission.