CN-114174133-B - Method for operating a hydraulic external force vehicle brake system for autonomous driving

Abstract

In order to operate a hydraulic external force vehicle brake system for autonomous driving, the invention proposes that a second external force brake pressure generator is used to generate a brake pressure if the first external force brake pressure generator does not generate a brake pressure or does not generate a sufficient brake pressure after a predetermined first period of time (t 1 ). If there is no failure notification from the first external braking pressure generator within a second period (t 2 ) longer than the first period (t 1 ), interrupting the process of generating braking pressure with the second external braking pressure generator.

Inventors

• T. Brux

Assignees

• 罗伯特·博世有限公司

Dates

Publication Date

20260505

Application Date

20200428

Priority Date

20190718

Claims (6)

1. 1. Method for operating a hydraulic external force vehicle brake system for autonomous driving, having a first external force brake pressure generator (3) and a second external force brake pressure generator (4), to which hydraulic wheel brakes (2) are connected, characterized in that if after a predetermined first time period (t 1 ) from the receipt of a brake signal of the first external force brake pressure generator (3) no predetermined brake pressure (p 1 ) is generated and a brake signal still exists, the brake pressure is generated with the second external force brake pressure generator (4) in the case of the brake signal, and if no fault notification of the first external force brake pressure generator (3) is present within a predetermined second time period (t 2 ) from the receipt of the brake signal, which is longer than the first time period (t 1 ).
2. 2. The method according to claim 1, characterized in that the process of generating braking pressure with the second external force braking pressure generator (4) is interrupted if the first external force braking pressure generator (3) generates a predetermined braking pressure or a vehicle equipped with the external force vehicle braking device (1) is stopped within a predetermined second period of time (t 2 ) which is longer than the first period of time (t 1 ) since the reception of the braking signal.
3. 3. Method according to claim 1 or 2, characterized in that the second external force brake pressure generator (4) is used for generating a brake pressure immediately upon receipt of a brake signal if the first external force brake pressure generator (3) is not yet ready to generate a brake pressure.
4. 4. Method according to claim 1 or 2, characterized in that the second external braking pressure generator (4) is used immediately to generate a braking pressure upon receipt of a braking signal if there is a failure notification of the first external braking pressure generator (3).
5. 5. Method according to claim 1 or 2, characterized in that the method is not performed if a predetermined braking pressure is generated differently from the braking pressure generator (3) with the first external force and/or a vehicle equipped with the external force vehicle braking device (1) is decelerated at a predetermined deceleration differently from the braking device (1) with the external force.
6. 6. Method according to claim 1 or 2, characterized in that the external braking pressure generator (3, 4) has an electronic control device (18, 19).

Description

Method for operating a hydraulic external force vehicle brake system for autonomous driving Technical Field The present invention relates to a method for operating a hydraulic external force vehicle brake device for land vehicles autonomously driven on public roads at or below level 4 or level 5. The term "autonomous driving" refers to a possible solution for autonomous driving, but the vehicle brake device according to the invention can also be used for land vehicles that are not autonomous or are autonomous at a lower level. Background In order to drive autonomously below class 4 (the driver can be required to intervene) and class 5 (the highest class; no driver is required), it is necessary to have redundant external force vehicle brake devices that exclude complete failure of the vehicle brake device with the probability of being in abutment with safety, without requiring driver intervention. Publication DE 1020114220440 A1 discloses an electrohydraulic external force vehicle brake system having two brake systems each having an external force brake pressure generator with a pressure source that can be driven electrically and a brake pressure control valve device for each wheel brake. One brake unit is connected to the other brake unit and the hydraulic wheel brakes are connected to one of the brake units such that the wheel brakes can be actuated with one of the brake units and with the other brake unit through one of the brake units. In the event of a failure or malfunction of one brake unit, the wheel brakes can thus be actuated with the other brake unit without driver intervention. The corresponding movable brake assembly adjusts the wheel brake pressure in the wheel brakes. Disclosure of Invention The object of the invention is to lose as little time as possible in order to build up a brake pressure with the second external force brake pressure generator if the first external force brake pressure generator does not generate a brake pressure or in any case does not generate sufficient brake pressure during external force braking. In principle, however, not two external braking pressure generators should be operated, but only one external braking pressure generator should be operated as often as possible. The vehicle brake system provided for the method according to the invention has two external brake pressure generators with which brake pressures for actuating the hydraulic wheel brakes of the vehicle brake system can be generated. The external force brake pressure generator can have a hydraulic pump or a piston-cylinder unit, wherein the hydraulic pump can be driven by an electric motor, and the piston of the piston-cylinder unit can be displaced in the cylinder by the electric motor, for example by a helical gear and, if appropriate, by an interposed mechanical reduction gear. Another possibility for an external braking pressure generator is a master brake cylinder which can be actuated with a controllable negative pressure brake booster or an electromechanical brake booster. This list is exemplary and not exhaustive. According to the invention, the second external braking pressure generator is used to generate a braking pressure if the first external braking pressure generator does not generate a predetermined braking pressure after a predetermined first period of time from the receipt of the braking signal and the braking signal is still present. If the braking should be applied with an external force, the braking signal can be a braking maneuver by the driver of the vehicle. The brake signal can also be generated independently of the driver of the vehicle, for example independently of an autonomous vehicle actuating device, independently of the distance adjusting mechanism of the vehicle travelling in front, or in the event of too rapid an approach to another vehicle or other obstacle. If a failure of the first external braking pressure generator is detected in a second period of time longer than the first period of time since the receipt of the braking signal, the wheel brake can be operated with the braking pressure generated by the second external braking pressure generator. The time from the end of the first period until the failure of the first external force braking pressure generator is identified is saved. If no failure of the first external braking pressure generator is detected within the second time period, the process of generating braking pressure with the second external braking pressure generator can be interrupted in a further embodiment of the method according to the invention. It is thereby avoided that the second external force brake pressure generator is used to operate the vehicle brake system, which, despite the presence of the brake signal, should not or should not be operated in such a way that the first external force brake pressure generator generates a brake pressure. For example, the vehicle brake system can be actuated by a third external brake pressure generator, f