Transmission service warm-up feature

摘要

A service warm-up feature warms transmission fluid to normal operating temperature faster than normal idle without requiring continuous technician attention. This facilitates checking the transmission fluid level. The feature increases the warm-up rate by commanding an increased line pressure and an increased idle speed, which causes more heat to be generated as the fluid flows through restrictions at an increased flow rate with an increased pressure drop. The warm-up rate may be further increased by holding the turbine shaft stationary to increase torque converter heat generation. Various precautions prevent accidental vehicle movement.

主权项

1. A transmission having a service warm-up feature, the transmission comprising:
a sump configured to hold a quantity of fluid; a pump configured to draw the fluid from the sump and deliver the fluid to a valve body at a line pressure and a flow rate; and a controller programmed to
in a normal idle mode, command the line pressure to a nominal pressure value and command the flow rate to a nominal flow value,in response to activation of the service warm-up feature, command the line pressure to a revised pressure value and command the flow rate to a revised flow value such that a product of the revised pressure value and the revised flow value exceeds a product of the nominal pressure value and the nominal flow value to accelerate fluid warm-up, andin response to a fluid temperature reaching a first threshold suitable for checking transmission fluid level while operating at the revised pressure value and the revised flow value, resume operation in the normal idle mode.