METHOD FOR CONTROLLING A PRESSURE GRADIENT OF A POWER BRAKE SYSTEM

Abstract

A method for controlling a maximum permissible pressure gradient of a power brake system of a motor vehicle. The method includes continuously calculating a maximum permissible pressure gradient, starting from a current motor speed gradient and motor speed of an external-force brake pressure generator, taking into account a predefined maximum permissible motor speed and a predefined maximum permissible motor speed gradient. In a next step, the maximum permissible pressure gradient is continuously transmitted to brake pressure demand units, so that, in the case of a braking event, the pressure gradient requested by the brake pressure demand units or resulting from a requested pressure is generally less than or equal to the maximum permissible pressure gradient.

Claims

1. A method for controlling a maximum permissible pressure gradient of a power brake system of a motor vehicle, the method comprising the following steps: continuously calculating a maximum permissible pressure gradient, starting from a current motor speed gradient and motor speed of an external-force brake pressure generator, taking into account a predefined maximum permissible motor speed and a predetermined maximum permissible motor speed gradient; and continuously transmitting the maximum permissible pressure gradient to brake pressure demand units so that, in the case of a braking event, a pressure gradient requested by the brake pressure demand units or resulting from a requested pressure is less than or equal to the maximum permissible pressure gradient.

2. The method according to claim 1, wherein, in predefined braking situations of the brake pressure demand units, a pressure gradient or a pressure gradient resulting from the requested pressure, is required which lies above the maximum pressure gradient.

3. The method according to claim 1, wherein a brake fluid volume provided by the external-force brake pressure generator is used to brake a single axle.

4. The method according to claim 1, wherein, a brake pressure at a rear axle and a brake pressure at a front axle are controlled independently of one another.

5. The method according to claim 1, wherein an additional braking torque is applied by recuperation to reduce the pressure gradient.

6. The method according to claim 1, wherein one axle of the motor vehicle is braked entirely by recuperation.

7. A power brake system, comprising: a comfort control unit configured to calculate a maximum permissible pressure gradient; an external-force brake pressure generator, via which a pressure for vehicle brakes can be generated for braking the vehicle; and brake pressure demand units via which, for braking the motor vehicle, a pressure gradient or pressure can be transmitted to the external-force brake pressure generator; wherein the power brake system is configured to: continuously calculate a maximum permissible pressure gradient, starting from a current motor speed gradient and motor speed of the external-force brake pressure generator, taking into account a predefined maximum permissible motor speed and a predetermined maximum permissible motor speed gradient; and continuously transmit the maximum permissible pressure gradient to the brake pressure demand units so that, in the case of a braking event, a pressure gradient requested by the brake pressure demand units or resulting from a requested pressure is less than or equal to the maximum permissible pressure gradient.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG. 1 shows an exemplary embodiment of a power brake system for carrying out method according to an example embodiment of the present invention.

[0020] FIG. 2 shows an exemplary embodiment of a method for controlling a maximum permissible pressure gradient of a power brake system, according to an example embodiment of the present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0021] FIG. 1 shows an exemplary embodiment of a power brake system 1 for carrying out the method according to the present invention. The power brake system 1 comprises an external-force brake pressure generator 4 which generates hydraulic brake pressure by means of which wheel brakes 8 of the power brake system 1 can be braked. In addition, a driver braking request detection unit 12 is provided, by means of which a braking request of the driver is detected and forwarded to the external-force brake pressure generator 4.

[0022] The power brake system 1 additionally comprises assistance systems 16 which represent a brake pressure demand unit, via which, independently of the driver braking request, a pressure gradient p.sub.grad is requested at the external-force brake pressure generator 4 in order to brake the motor vehicle. Although in this exemplary embodiment a pressure gradient is requested by the brake pressure demand units, it is also possible to request only a pressure which is to be reached in a specific time. In addition, a further brake pressure demand unit formed by an external control device 20 can be present, which requests from the external-force brake pressure generator 4 a pressure gradient p.sub.grad.

[0023] In addition, the power brake system 1 comprises a comfort control unit 24, in which, starting from a current motor speed gradient n.sub.grad and the motor speed n.sub.M of the external-force brake pressure generator 4, while taking into account a maximum speed n.sub.max and a maximum speed gradient n.sub.max.grad, a maximum permissible pressure gradient p.sub.max.grad can be calculated. This maximum permissible pressure gradient p.sub.max.grad is communicated continuously to each brake pressure demand unit 16, 20, so that the pressure gradient p.sub.grad requested by these units 16, 20 does not exceed this value. This ensures that the noise and vibrations generated by the external-force pressure generator 4 lie below a perceptible range.

[0024] FIG. 2 shows an exemplary embodiment of a method for controlling a maximum permissible pressure gradient p.sub.max.grad of a power brake system 4. In a first method step A, starting from the current motor speed gradient n.sub.grad and the current speed n.sub.M of the external-force brake pressure generator 4, while taking into account a predefined maximum permissible motor speed n.sub.max and a maximum motor speed gradient n.sub.max.grad, a maximum permissible pressure gradient p.sub.max.grad is calculated. In a second method step B, this maximum permissible pressure gradient p.sub.max.grad is transmitted to all brake pressure demand units 16, 20, so that, in the case of a braking event, the pressure gradient p.sub.grad requested by the brake pressure demand unit 16, 20 is generally smaller than or equal to the maximum permissible pressure gradient p.sub.max.grad.

[0025] These steps are carried out continuously, so that for each current state of the external-force brake pressure generator 4 the maximum permissible pressure gradient p.sub.max.grad of the brake pressure demand units 16, 20 is known. Perceptible noise and vibrations can thereby be avoided.