Hill hold method and system
A hill-hold method and system for a vehicle with manual transmission provides automated brake release timing when the vehicle's clutch is still disengaged to minimize or even prevent backward coasting of such a vehicle on a non-zero grade or hill by delaying full release of the brakes when the vehicle operator is in the transition of releasing the brake pedal and moving to the accelerator pedal.
1. A method of providing a hill-hold function for a vehicle equipped with a manual transmission and clutch, the method comprising:
providing a selectively variable orifice in a brake hydraulic line of the vehicle, operative to fully close at zero vehicle speed and actuation of a brake pedal of the vehicle;
opening the variable orifice at a first rate upon detection of release of the brake pedal while the clutch is disengaged and the throttle is starting to increase; and
opening the variable orifice at a second rate higher than the first rate upon detection of clutch activation.
2. The method of claim 1 further comprising:
skipping the opening of the variable orifice at the first rate and upon release of the brake immediately opening the variable orifice at the second rate whenever a substantially level roadway is detected.
3. The method of claim 2 wherein the substantially level roadway is detected using a grade sensor.
4. The method of claim 2 wherein the substantially level roadway is detected by absence of reverse rotation of wheels of the vehicle upon brake release.
5. An arrangement for providing a hill-hold function in a vehicle equipped with a manual transmission and clutch, the arrangement comprising:
a selectively variable orifice positioned in a hydraulic brake fluid line of the vehicle;
an auxiliary brake controller coupled to a control input of the selectively variable orifice operative to open and close the selectively variable orifice at a rate determined by a signal presented to the control input;
an electronic vehicle control module coupled to the auxiliary brake controller; and
a clutch pedal position sensor, a throttle sensor, a vehicle speed sensor and a brake pedal sensor, each coupled to a respective input of the electronic vehicle control module;
the electronic vehicle control module operative to signal the auxiliary brake controller to fully close the selectively variable orifice whenever the vehicle speed sensor detects zero vehicle speed and the brake pedal sensor detects actuation of a brake pedal of the vehicle;
the electronic vehicle control module further operative to signal the auxiliary brake controller to open the selectively variable orifice at a first rate whenever the brake pedal sensor detects release of the brake pedal, the clutch pedal position sensor detects disengagement of a clutch of the vehicle, and the throttle sensor detects initiation of increase of a throttle of the vehicle; and
the electronic vehicle controller further operative to signal the auxiliary brake controller to open the selectively variable orifice at a second rate higher than the first rate when the clutch pedal position sensor detects clutch activation.
6. The arrangement of claim 5 further comprising a non-level roadway sensor coupled to the electronic vehicle control module, and wherein the vehicle control module activates and deactivates the auxiliary brake controller as a function of a signal from the non-level roadway sensor in addition to signals from one or more of the clutch pedal position sensor, the throttle sensor, the vehicle speed sensor and the brake pedal sensor.
7. The arrangement of claim 6 wherein the non-level roadway sensor comprises a non-zero grade sensor.
8. The arrangement of claim 6 wherein the non-level roadway sensor comprises a wheel direction of rotation sensor.