Method Of Calibration Of A Park Brake Of A Continuously Variable Transmission

摘要

A method of calibrating a hydraulically operated park brake of a continuously variable transmission of a vehicle. With the vehicle moving at a set, slow speed within a specified range, and the park brake off, a search technique is used, wherein the brake hydraulic pressure is reduced by application of a control signal of a selected test value to apply the brake. When the selected test value is reached, it is held constant, and a condition in a HSU of the transmission is monitored for a change indicative of engagement of the park brake. This will expectedly be in the form of a pressure change and more particularly an increase indicating initial contact between the plates of the brake, and if the HSU change is not detected, the step will time out and another control signal value will be tested.

主权项

1. A method of calibrating a hydraulically operated park brake of a vehicle, comprising steps of:
a. propelling the vehicle using the transmission, with all brakes off; b. monitoring a pressure condition in a hydrostatic power unit of the transmission, including recording a base pressure value in the unit; c. controlling the park brake in a predetermined manner using a first control signal value, and determining a resulting change in a pressure condition in the hydrostatic power unit, and: i. if the resulting change in the pressure condition in the hydrostatic power unit is more than a first predetermined value, then releasing the park brake and repeating steps a.-c. to control the park brake using a second control signal value expected to produce a lower resulting change in the pressure condition in the hydrostatic power unit; and ii. if the resulting change in the pressure condition in the hydrostatic power unit is less than a second predetermined value, then releasing the park brake and repeating steps a.-c. to control the park brake using a control signal value expected to produce a higher resulting pressure in the hydrostatic power unit; and d. if the resulting pressure in the hydrostatic power unit after performing steps a.-c. is between the first predetermined value and the second predetermined value, then recording the control signal value as the calibration value.