GB2376991A

GB2376991A - Releasing a vehicle electric parking brake upon a significant reduction in engine speed to throttle pedal displacement ratio

Info

Publication number: GB2376991A
Application number: GB0115783A
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: GB0115783D0; GB2376991B

Abstract

An electric parking brake control system 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; vehicle engine speed greater than idle; and vehicle engine loading (defined by a significant reduction in the ratio between engine speed and throttle pedal displacement, relative to the ratio obtained under the same conditions when the vehicle is unloaded), reflecting a drivers intention to pull away from rest. The ratio reduction may be significant in that the ratio drops below a mapped curve (lower than free running characteristic to eliminate transients) for a specific time. An inclination sensor may modify one or more parameter to adjust for local conditions.

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) vehicle engine speed greater than idle ; and (iii) vehicle engine loading.

Preferably, vehicle engine loading is defined by a significant reduction in the ratio between engine speed and throttle pedal displacement, relative to the ratio obtained under the same conditions when the vehicle engine is unloaded.

It will be understood to a person skilled in the art that slight variations may occur in the ratio as a result of other engine parameters. Therefore, the reduction in ratio must be significant before engine loading is inferred. Preferably, the ratio must drop below a mapped curve for a specific time (to accommodate for delays in engine response).

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 one or more of the following parameters which determine whether the EPB control module signals the release of the park brake force :- (i) engine speed; and/or (ii) the ratio between engine speed and throttle pedal displacement; and/or (iii) the time a significant reduction in the ratio between engine speed and throttle pedal displacement, relative to the ratio obtained under the same conditions when the vehicle engine is unloaded, must be maintained.

Thus the system can be fine-tuned to adjust for parking conditions, i. e. whether the vehicle is parked on a flat surface or on a hill.

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 relationship between throttle pedal position and engine speed for a free-running (unloaded) engine (clutch disengaged); Figure 2 shows a graph of the throttle pedal position against engine speeds (revolutions); and Figure 3 shows a system diagram of an EPB system in accordance with one aspect of the invention.

Referring now to the figures, Figure 1 defines a graph of unloaded steady state engine speed 20 and throttle pedal position 10 over time.

Figure 2 is an example of a mapped plot used to determine when to release the park brake. It is to be noted that the profile illustrated is significantly lower than the free running engine characteristics to account for performance variations and transients. Loading of the engine is detected when the engine speed drops significantly below the mapped curve for a specific time (to accommodate for delays in engine response). When the EPB control module detects engine loading in this way, the module will signal for the park brake to be released.

Figure 3 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 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 of engine speed and throttle position over time. 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) vehicle engine speed greater than idle ; and (iii) vehicle engine loading as defined by a significant reduction in the ratio between engine speed and throttle pedal displacement, relative to the ratio obtained under the same conditions when the vehicle is unloaded.
2. An electric parking brake control system for a vehicle according to claim 1 wherein the reduction in ratio must be maintained for a predetermined time to accommodate for delays in vehicle engine response.
3. An electric parking brake control system according to claim 1 or claim 2 further comprising a manual override mechanism.
4. An electric parking brake control system according to any one of the preceding claims further comprising an inclination sensor to adjust one or more of the following parameters which determine whether the EPB control module signals the release of the park brake force :- (i) engine speed; and/or (ii) the ratio between engine speed and throttle pedal displacement ; and/or (iii) the time a significant reduction in the ratio between engine speed and throttle pedal displacement, relative to the ratio obtained under the same conditions when the vehicle engine is unloaded, must be maintained.
5. An electric parking brake control system substantially as described hereinabove and with reference to the accompanying system diagram.

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6. A vehicle comprising an electric parking brake control system according to any one of the preceding claims.
7. 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 claim 1 to 5.
8. A method of applying a park brake force to a vehicle substantially as described hereinabove and with reference to the accompanying system diagram.