GB2376990A

GB2376990A - Releasing a vehicle electric parking brake when a clutch pedal position approaches the biting point

Info

Publication number: GB2376990A
Application number: GB0115751A
Authority: GB
Inventors: Peter John Bennett; Simon Rouven Perkins
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2001-06-28
Filing date: 2001-06-28
Publication date: 2002-12-31
Anticipated expiration: 2021-06-28
Also published as: GB2376990B; GB0115751D0

Abstract

An electric parking brake control system (fig 5) for a vehicle comprises an electric park brake (EPB) assembly for applying a park brake force to the vehicle and an EPB control module. The EPB control module releases the park brake force exerted by the EPB assembly on receipt of signals indicating positive displacement of the vehicle throttle and that the vehicle clutch pedal position is approaching the biting point, reflecting a drivers intention to pull away from rest. Additionally, a gear selected signal and/or clutch pedal velocity may influence the system, the latter causing earlier brake release if the velocity is above a threshold, thus controlling both slow clutch movement (20, fig 1) or rapid clutch movement 220. An inclination sensor may further modify the parking brake release point.

Description

ELECTRIC PARKING BRAKE The present invention relates to an electrically powered parking brake. In particular, the present invention relates to a system and method for controlling the parking brake for a vehicle as it pulls away from rest.

Almost all vehicles have a parking brake mechanism, and most of these vehicles have a hand lever or foot activated lever for actuating the parking brake mechanism.

Typically, these levers are attached to a cable and cause displacement of the cable and operation of the attached parking brake mechanism.

The mechanisms underlying vehicle technology are constantly revised and updated in light of consumer preferences, vehicle presentation, packaging, marketing and increased safety obligations. In line with this, electric parking brake systems have been proposed as an alternative to the conventional manual parking brake mechanism. These have comprised an electric control means to signal the application and release of the parking brake mechanism in response to a predetermined combination of vehicle operating conditions.

One electric parking brake assembly discloses a system whereby the parking brake is actuated on depression of the foot brake together with a signal that the vehicle is stationary. Another assembly suggests a system whereby the parking brake is actuated by a combination of foot brake application and push button operation. In such disclosures the parking brake is de-actuated by accelerator depression and/or clutch depression and/or shift gear selection. None of these defining operating conditions clearly and unambiguously reflect the status and intention of the driver to pull away from rest.

It is an object of the present invention to provide an electric parking brake control system for a manual transmission vehicle that operates automatically to release the park brake as the driver initiates a pull away driving sequence. It is another object of

the present invention to provide an electric parking brake control system that ensures maximised safety for the driver. It is yet another object of the invention to provide an electric parking brake control system that provides a sensitive release of the park brake in response to the driver's driving style and parking conditions.

Accordingly, in one aspect the invention provides an electric parking brake control system for a vehicle, comprising an electric park brake (EPB) mechanism for applying a park brake force to the vehicle and an EPB control module, wherein the EPB control module releases the park brake force exerted by the EPB mechanism on receipt of signals which indicate :- (i) positive displacement of the vehicle throttle ; and (ii) the vehicle clutch pedal position is approaching the biting point.

Preferably, the system also monitors clutch pedal velocity.

Typically, release of the park brake force further requires an additional signal that indicates that a gear has been selected.

With conventional vehicle manual clutch operation systems, a lever (assumed to be a foot pedal in the description infra) is operated to cause the clutch to move between a position of fully disengaged to fully engaged. As the lever is moved from the disengaged to the fully engaged position, the clutch plates will at some point start to transmit torque from the engine through to the transmission. This point is known as the'bite-point'of the clutch.

In one embodiment, if the clutch pedal velocity as it approaches biting point is below a threshold velocity, the EPB control module will release the park brake force on receipt of signals (i) and (ii).

The threshold clutch pedal velocity may be from 20% to 50%, e. g. 20% or 25% or 30% or 40% or 50% of total clutch pedal displacement per second.

Thus, if the clutch pedal velocity as it approaches biting point is slow, that is, less than 50% and/or less than 40% and/or less than 30% and/or less than 25% and/or less than 20% of total displacement per second, the EPB control module will release the park brake force on receipt of signals (i) and (ii).

As used herein, total displacement means displacement from fully disengaged to fully engaged.

If the clutch pedal velocity as it approaches biting point is above a threshold velocity, the EPB control module may adjust the position (the apparent biting point) which the clutch pedal must approach before the park brake force is released.

Preferably, if the clutch pedal velocity as it approaches biting point is greater than the threshold velocity, that is, rapid, for example, between 20 and 100% and/or between 25 and 100% and/or between 30 and 100% and/or between 40 and 100% and/or between 50 and 100% of total displacement per second, the actual clutch position, or apparent biting point, at which the park brake is released will be adjusted by an amount which may be dependent on the velocity of the clutch pedal. Thus, the faster the pedal is released the earlier the EPB control module will signal for the park brake to be released.

This function is designed to allow the EPB control module to adapt to the driving style of the driver which may change depending on the situation, for example whether a vehicle is pulling away on a hill, towing a trailer, pulling away fast from a stopped position or pulling away cautiously, for example, when in the midst of heavy traffic.

The precise thresholds for each parameter will be specific to the type of vehicle to which the EPB system is applied.

Preferably, the electric parking brake control system further comprises a manual override mechanism. in one embodiment, the electric parking brake control system further comprises an inclination sensor to adjust the clutch pedal position at which the park brake force is released.

The inclination sensor may alternatively or in addition adjust the threshold clutch pedal velocity and/or the amount by which the apparent biting point is adjusted if the clutch pedal velocity is above the threshold value.

Thus the system can be fine tuned to adjust for parking conditions, i. e. whether on a flat surface or on a hill, and so prevent the vehicle from rolling back on steep hills.

In another aspect, the invention provides a vehicle comprising an electric parking brake control system as defined supra.

In still another aspect, the invention provides a method of releasing a park brake force from a vehicle comprising the use of an electric park brake system as described supra.

The invention will now be described further with reference to the accompanying drawings, in which :Figure 1 shows a graph of the clutch pedal position and clutch pedal velocity (% displacement per second) against time for a slow pull away situation; Figure 2 shows a graph of the clutch pedal position (%) and the EPB control module release request against time. Note: This data was extracted from the same experiment as Figure 1;

Figure 3 shows a graph of the clutch pedal position and clutch pedal velocity against time for a rapid pull away situation; Figure 4 shows a graph of the clutch pedal position (%) and the EPB control module release request against time. Note: This data was extracted from the same experiment as Figure 3; and, Figure 5 shows a system diagram of an EPB system in accordance with one aspect of the invention.

Referring now to the figures, Figures 1 and 2 illustrate the parameters when a driver pulls away form rest using a slow clutch pedal movement. The clutch pedal position 10; 110 is slowly raised from the disengaged position so that the clutch pedal velocity 20; 120 remains substantially unchanged. In this example, the EPB control module does not take into account the clutch pedal velocity and triggers the release of the park brake in response to the throttle and clutch pedal position.

In contrast, Figures 3 and 4 illustrate the parameters when a driver pulls away form rest using a fast clutch pedal movement. The clutch pedal position 210 is raised rapidly from the disengaged position so that the clutch pedal velocity 220 increases dramatically over a short time period. The EPB control module thus registers the high velocity of the pedal together with the clutch pedal position and triggers the release of the park brake in response.

Figure 5 illustrates a system diagram embodying one example of how the system may be implemented. The EPB control module is placed at the control centre of a network of connections to the vehicle throttle, clutch pedal and gearbox, and an engine management unit that detects inter alia, engine torque, engine acceleration and engine speed. A pedal sensor unit measures movement of the clutch pedal during use and signals to the control unit so that the control unit can detect the relationship between clutch speed and clutch position. In this particular example, information from an instrument cluster is displayed at a display window for maximum user information.

It will be understood that the present disclosure is for the purpose of illustration only and the invention extends to modifications, variations and improvements thereto.

The application of which this description and claims form part may be used as a basis for priority in respect of any subsequent application. The claims of such subsequent application may be directed to any feature or combination of features described therein. They may take the form of product, method or use claims and may include, by way of example and without limitation, one or more of the following claims :

Claims

Claims :- 1. An electric parking brake control system for a vehicle comprising an electric park brake (EPB) assembly for applying a park brake force to the vehicle and an EPB control module, wherein the EPB control module releases the park brake force exerted by the EPB assembly on receipt of signals to indicate :- (i) positive displacement of the vehicle throttle ; (ii) the vehicle clutch pedal position is approaching the biting point
2. An electric parking brake control system according to claim 1 which monitors the vehicle clutch pedal velocity.
3. An electric parking brake control system according to claim 1 or claim 2 wherein the EPB control module releases the park brake force exerted by the EPB assembly on receipt of a signal to indicate a gear has been selected.
4. An electric parking brake control system according to claim 2 or claim 3 wherein if the clutch pedal velocity as it approaches biting point is below a threshold velocity, the EPB control module will release the park brake force on receipt of signals (i) and (ii).
5. An electric parking brake control system according to claim 4 wherein the threshold clutch pedal velocity is 20% to 50% of total clutch pedal displacement per second.
6. An electric parking brake control system according to claim 4 or claim 5 wherein if the clutch pedal velocity as it approaches biting point is less than 50% and/or less than 40% and/or less than 30% and/or less than 25% and/or less than 20% of total displacement per second, the EPB control module will release the park brake force on receipt of signals (i) and (ii).

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7. An electric parking brake control system according to any one of the preceding claims wherein if clutch pedal velocity as it approaches biting point is above a threshold velocity, the EPB control module adjusts the position (the apparent biting point) which the clutch pedal must approach before the park brake force is released.
8. An electric parking brake control system according to claim 1 or claim 2 wherein if the clutch pedal velocity as it approaches biting point is between 20 and 100% of total displacement per second, the EPB control module adjusts the position (the apparent biting point) which the clutch pedal must approach before the park brake force is released.
9. An electric parking brake control system according to any one of the preceding claims further comprising a manual override mechanism.
10. An electric parking brake control system according to any one of the preceding claims further comprising an inclination sensor to adjust the clutch pedal position at which the park brake force is released.
11. An electric parking brake control system according to any one of claims 4 to 10 further comprising an inclination sensor to adjust the threshold clutch pedal velocity.
12. An electric parking brake control system according to any one of claims 7 to 11 further comprising an inclination sensor to adjust the amount by which the apparent biting point is adjusted if the clutch pedal velocity is above the threshold value.
13. An electric parking brake control system substantially as described hereinabove and with reference to the accompanying system diagram.

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14. A vehicle comprising an electric parking brake control system according to any one of the preceding claims.
15. A method of releasing a park brake force from a vehicle comprising the use of an electric park brake system according to any one of claims 1 to 13.
16. A method of applying a park brake force to a vehicle substantially as described hereinabove and with reference to the accompanying system diagram.