GB2419164A

GB2419164A - Brake system having a settable braking characteristic

Info

Publication number: GB2419164A
Application number: GB0520273A
Authority: GB
Inventors: Karl-Ernst Weiss; Johannes Eschler; Markus Hauk
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2004-10-06
Filing date: 2005-10-05
Publication date: 2006-04-19
Also published as: GB0520273D0; DE102004048605B3

Abstract

The invention relates to a brake system for motor vehicles, having a brake pedal (1), a brake pedal sensor (2) for detecting a brake actuation, a controller (3) which is connected to the sensor (1), and an actuator (4) for varying the brake application force acting on the wheel brakes (5), the braking deceleration being set by the controller (3) according to a predetermined braking characteristic (BF, 13, 14). In order to render possible a user-specific setting of the braking characteristic (BF, 13), the controller comprises a setting algorithm (9) by means of which a setting procedure (10 - 12) can be performed, in which the strength of the brake pedal actuation is ascertained and the braking characteristic (BF, 13, 14) is set in dependence thereon.

Description

Brake system having a gettable braking characteristic The invention

relates to a brake system for motor vehicles, according to the preamble of claim 1, and to a procedure for setting the braking characteristic of a vehicle brake, according to the preamble of claim 7.

Brake systems of modern vehicles normally comprise a vacuum-assisted brake booster, which boosts the braking force exerted by the driver. The mechanical design of the brake booster and of the rest of the brake system then determines the so-called braking characteristic, i.e. the relationship between the pedal travel, or the force applied to the brake pedal, and the braking deceleration of the vehicle resulting therefrom. The braking characteristic is usually a fixed relationship that is predefined by the system, and not variable.

On the other hand, ever more frequently modern vehicles are being equipped with electrohydraulic or electromechanical brake systems, in which the mechanical feedthrough between the brake pedal and the actual wheel brake is absent.

Instead, in the case of this type of brake system, the driver's braking intention is detected by sensor means and, for example, the pedal position or the pedal force is converted into an electrical signal, which is evaluated by a controller connected to the brake pedal. The controller then activates the actual brake actuators, such as, for example, electric motors or a hydraulic pump. The driver' s braking intention is then converted according to a predetermined braking characteristic which, in this case, is stored as an algorithm (braking function) in the controller. In the case of the aforementioned electromechanical brake systems, it is also not possible to modify the braking response as required.

It is therefore the object of the present invention to create a brake system and a corresponding procedure by which the braking characteristic of the vehicle can be individually set.

This object is achieved, according to the invention, by the features disclosed in claim 1 and in claim 7. Further developments of the invention constitute the subject-matter of the sub-claims.

An essential concept of the invention is that a setting procedure is performed (e.g. following a new startup of the vehicle), in which the driver actuates the brake pedal, and the braking characteristic is set in dependence on the extent of the actuation. In the setting procedure, the extent of the brake actuation (e.g. the braking force or the brake pedal travel) is then measured by sensor means at the brake pedal, and the braking characteristic is modified in dependence thereon. It thereby becomes possible to set the vehicle brakes, for example, to a more sensitive (comfortable) setting in the case of a weak pedal actuation, and more to a hard, sporty setting in the case of a strong pedal actuation. In the case of a comfortable brake setting, a relatively weak pedal actuation then effects a relatively high vehicle deceleration in the subsequent vehicle operation, whereas, in the case of a hard, sporty setting, a substantially stronger actuation of the brake pedal is necessary in order to achieve the same braking effect. The brake system can thus be set, for example, to individual requirements of male or female drivers, or of drivers preferring either a sporty or comfortable driving style.

In the case of a vehicle having an electrohydraulic or electromechanical brake system, only the braking function (e.g. one or more parameters of the algorithm) need be changed in order to modify the braking response. In the case of purely mechanical brake systems, a means such as, for example, a mechanical actuator, by means of which the braking response can be influenced, is preferably provided.

For this purpose, the brake booster may comprise, for example, a controllable valve, by means of which the vacuum in the vacuum chamber, and consequently the brake boosting, can be changed. The actuating means is preferably connected to a controller, and able to be activated by the latter.

In the case of known vehicles, the relationship between pedal force and pedal travel is usually predetermined in a fixed manner by the mechanical structure of the brake system. In the case of an electromechanical brake system, in which the mechanical feedthrough between the brake pedal and the actual wheel brake is absent, an element such as, for example, a spring, which acts on the brake pedal and which defines the force/path relationship, is normally provided to generate a pedal counterforce. According to the invention, it is proposed that the ratio of pedal force to pedal travel be made such that it can be set and, for this purpose, a device be provided by means of which a variable pedal counterforce can be set, such as, for example, a spring system having a gettable spring constant.

The device according to the invention may be activated by, for example, a controller. This option may be provided as an alternative or in addition to the setting of the pedal force/vehicle deceleration or pedal travel/vehicle deceleration characteristic.

The setting procedure is preferably performed when the vehicle is stationary, particularly before commencement of driving. The stationary vehicle state is particularly safe, and is therefore particularly suitable for setting of the braking. The setting routine may also be active during a defined interval of time after the vehicle is put into operation.

Various braking settings may also, for example, be stored in a memory and called up upon request. Setting of the braking response may also, for example, be semi-automatic, in a manner similar to the semi-automatic setting, known from the prior art, of the seat, the steering wheel or the interior/exterior mirror, through pressing of a memory key or through fingerprint identification.

The brake system according to the invention preferably also comprises a means for activating and/or deactivating the setting procedure for the setting of the braking characteristic. This enables the driver himself to decide whether or not a resetting of the brake system is to be performed. The driver is can enable and activate the setting routine by, for example, operating a switch.

Vehicles with an automatic transmission usually require the service brake to be depressed in order to move the gear selector lever out of the park position into the drive position. This operation can be used to set the braking characteristic at the same time. The braking characteristic is therefore preferably set in this operation on the basis of the brake actuation.

The invention is explained more fully in the following with reference to the appended drawings, wherein: Fig. 1 shows a schematic representation of an electromotive system, Fig. 2a shows a schematic representation of a path deceleration characteristic, Fig. 2b shows a schematic representation of a force deceleration characteristic, and Fig. 3 shows the essential procedural steps for setting the braking characteristic, in the form of a flow diagram.

Fig. 1 shows a schematic representation of an electromotive brake system of a motor vehicle. The brake system comprises, in essence, a brake pedal 1, a brake pedal sensor 2 (pedal valuator device), a controller 3 connected to the sensor, and a plurality of brake actuators (here, electric motors) 4 which can be activated by the controller 3. The controller 3 furthermore comprises an algorithm 9 for performing a setting procedure by means of which the braking characteristic, and thus the braking response of the vehicle, can be individually set.

In the case of a brake actuation during driving, the driver's braking intention is detected by means of the brake pedal sensor 2 and converted into a corresponding electrical signal, which is supplied to the controller 3.

The brake pedal sensor 2 may be realized, for example, as an angular displacement sensor, linear displacement sensor, force sensor or pressure sensor.

The controller 3 processes the electrical sensor signal and activates the brake actuators 4 of the wheel brakes 5 according to a braking function BF which is stored in the controller 3 and which defines the relationship between the strength of the brake actuation and the resulting vehicle deceleration.

Typical braking characteristics 13, 14, are represented in Figs. 2a and 2b, Fig. 2a showing a pedal travel/vehicle deceleration characteristic 13 and Fig. 2b showing a pedal force/pedal travel characteristic 14.

The braking function BF, and consequently the braking response of the vehicle, can be individually set by means of a setting procedure. In this case, during a setting phase the extent of the brake actuation is measured at the brake pedal (e.g. the braking force or the brake pedal travel), and the braking function BF, or one or more parameters of the braking function, is modified in dependence on the strength of the brake pedal actuation.

It thereby becomes possible to set the vehicle brakes 5, for example, to a more sensitive (comfortable) setting in the case of a weak pedal actuation, and more to a hard, sporty setting in the case of a strong pedal actuation.

Alternatively, or additionally, the ratio between the pedal force and pedal travel can also be modified. For this purpose, the brake system would have to comprise a device (not shown) which acts on the brake pedal in order to set a pedal counterforce, such as, for example, a spring system having a gettable spring constant, by means of which a variable pedal counterforce can be set.

In Figs. 2a and 2b, arrow a denotes the displacement of the pedal characteristics 13, 14 towards a comfortable setting, and arrow b denotes their displacement towards a harder setting.

A possible setting procedure, which is implemented through the algorithm 9, is represented in Fig. 3 by a flow diagram.

Fig. 3 shows the essential procedural steps of a procedure for setting the braking characteristic 13 of a brake system. In this case, it is first ascertained, in step 10, whether the travel status is such that setting of the braking response can be performed. Such a travel status is, for example, that the vehicle is stationary following a new startup. If this status is identified by the controller 3 in step 10 (case Y), the setting routine is started, in which the strength of the brake actuation is measured by sensor means in step 11, and the corresponding sensor is transmitted to the controller 3. The controller 3 thereupon, in step 12, modifies the braking function OF on the basis of the sensor signal, one or more parameters of the braking function being adjusted. In the case of a weak pedal actuation, the braking characteristic is set more to a comfortable setting, and in the case of a strong pedal actuation it is set more to a hard, sporty setting.

During the setting procedure, it is thus possible for the driver to selectively set a more comfortable or a harder braking characteristic through a higher or lower brake pedal force.

The setting of the brake system must, of course, remain within the legally set boundary values, and lie within the limits set by ergonomic considerations.

A successful brake calibration is preferably displayed to the driver by a corresponding optical or acoustic device.

Unless a new setting procedure is to be performed after each new startup of the vehicle, an enabling means 8, such as, for example, a switch or pushbutton, with which the driver can activate the setting procedure, may additionally be provided. In this case, the procedure of Fig. 3 would comprise an additional procedural step, in which the enabling is verified and the setting routine is performed only upon being enabled.

The setting procedure can also be performed, analogously, in the case of an electrohydraulic brake system or a mechanical brake system. In the case of a purely mechanical brake system, it is then necessary to provide a means such as, for example, an actuator, which enables the braking characteristic to be influenced. For this purpose, for example, the brake booster (not shown) may comprise a controllable valve by means of which the boosting of the brake booster can be set.

List of references 1 Brake pedal 2 Pedal valuator device 3 Controller 4 Brake actuators Wheel brakes 6 Brake discs 7 Electrical control lines 8 Enabling means 9 Setting algorithm -12 Procedural steps 13 Pedal travel/deceleration characteristic 14 Pedal force/pedal travel characteristic BE Braking function

Claims

Claims 1. Brake device for motor vehicles, comprising a brake pedal (1), a

sensor (2) for detecting a brake pedal actuation, and a controller (3) which is connected to the sensor (2), characterized in that the controller (3) comprises an algorithm (9) by means of which a setting procedure (10 12) can be performed for the purpose of setting the braking characteristic (BF, 13, 14), the driver actuating the brake pedal (1) as desired during the setting procedure (10 - 12), the sensor (2) measuring the extent of the brake pedal actuation and setting the braking characteristic (BF, 13, 14) in dependence thereon.
2. Brake device according to claim 1, characterized in that, in the case of an electromechanical brake system, the controller (3) comprises a braking function (BF) which is modified in dependence on the extent of the brake pedal actuation.
3. Brake device according to claim 1, characterized in that, in the case of a purely mechanical brake system, a means (3) is provided by means of which the braking characteristic (13, 14) can be varied.
4. Brake device according to any one of the preceding claims, characterized in that an enabling means (8) is provided, which is connected to the controller (3) and by means of which the setting procedure can be activated or deactivated.
5. Brake device according to any one of the preceding claims, characterized in that performance of the setting procedure (10 - 12) is only possible when the vehicle is stationary.
6. Brake device according to any one of the preceding claims, characterized in that the setting procedure (10 - 12) is performed automatically after each new startup of the vehicle.
7. Procedure for setting the braking characteristic of a >\; brake system, characterized in that a setting procedure (10 - 12) is performed in which the driver actuates the brake pedal (1) as desired, the extent of the brake pedal actuation is ascertained by sensor means, and the braking characteristic (BF, 13, 14) is modified in dependence thereon.
8. Procedure according to claim 7, characterized in that, upon actuation of the brake pedal (1) with a small force, a flatter pedal force/pedal travel characteristic (14) is set and, upon actuation with a large force, a steeper pedal force/pedal travel characteristic (14) is set.
9. Procedure according to claim 7, characterized in that, upon actuation of the brake pedal (1) with a small force during the setting procedure (10 - 12), a higher braking deceleration is set and, upon actuation with a large force, a lower braking deceleration is set, for brake pedal forces of equal magnitude in driving.
10. Procedure according to either of claims 7 or 8, characterized in that the setting procedure (10 - 12) is performed only if it has been previously activated by means of an enabling means (8).
11. Brake device substantially as hereinbefore described with reference to the accompanying drawings.
12. Procedure substantially as hereinbefore described with reference to the accompanying drawings.