Main Brake Cylinder for a Hydraulic Vehicle Brake System and Method for Operating Same
AssigneeRobert Bosch GmbH
InventorMichael Kunz
Life of this patent
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Abstract
A main brake cylinder for a hydraulic vehicle brake system of a motor vehicle is disclosed. The main brake cylinder includes an electric motor that is operated as a generator for decelerating the motor vehicle. For service braking, pressure is applied to a brake circuit by the main brake cylinder and to another brake circuit by a hydraulic pump. In order to reduce a pedal force, a first piston has a smaller piston surface and a second piston only moves if a greater brake fluid volume is required. A preloaded hydraulic accumulator limits an increase in pressure.
Claims7
A hydraulic vehicle brake system of a motor vehicle comprising:
- a master brake cylinder including:
- a brake circuit having two pistons including a first piston and a second piston,
- a carrier device, and
- an electric machine configured to be operated as a generator for decelerating the motor vehicle, and
- a hydro-accumulator which communicates with the master brake cylinder,
- wherein the carrier device is configured such that after movement of the first piston by a prespecified piston travel, the carrier device carries the second piston with the first piston, and
- wherein a piston area of both of the two pistons active for displacement of brake fluid from the master brake cylinder is greater than a piston surface of the first piston active for displacement of brake fluid from the master brake cylinder, and
- wherein the hydro-accumulator is configured to have a pretension such that it only receives brake fluid from the master brake cylinder when a master brake cylinder pressure is greater than a maximum design pressure of the vehicle brake system.
A method for operation of a hydraulic vehicle brake system of a motor vehicle which comprises a master brake cylinder with two pistons for a brake circuit of the vehicle brake system and a carrier device which after movement of a first of the two pistons over a pre-specified piston travel carries the second piston with the first piston, wherein a piston surface area of both pistons active for displacement of brake fluid from the master brake cylinder is greater than a piston surface of the first piston active for displacement of brake fluid from the master brake cylinder, and wherein the brake circuit of the vehicle brake system is connected via an isolating valve to the two pistons of the master brake cylinder, which valve is closed in service braking, wherein the motor vehicle comprises an electric machine which in service braking is operated as a generator and decelerates the motor vehicle, that the vehicle brake system comprises a hydraulic pump with which in service braking a brake pressure is generated and that a wheel brake pressure in at least one wheel brake of the vehicle brake system is regulated depending on activation of the master brake cylinder and on a deceleration effect of the electric machine operated as a generator.
Dependencies are inferred from the claim text.