Hydraulic Brake System Parking Actuation Control
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Solution Overview
Problem
The existing hydraulic brake systems in motor vehicles exhibit unusual pedal behavior when enabling the parking brake function due to superimposition of actuator and pressure generator forces, leading to unintended pedal movement towards the floor and back, which can be unsettling for the driver.
Innovation Solution
The pressure generator is controlled in dependence on the movement and rate of the actuator element, compensating volume increases by conveying hydraulic medium into the brake circuit to maintain consistent pedal position, and a switching valve prevents return flow to retain pressure, with optional redundancy from an electromechanical brake booster and pump configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If both the actuator and pressure generator are actuated to enable the parking brake function, then the total clamping force on the wheel brake is improved, but the brake pedal exhibits unusual movement behavior towards the floor and back
Solution Approach 1:
The pressure generator is actuated in advance before the actuator element contacts the brake piston. This preliminary action increases the hydraulic pressure in the brake circuit beforehand, so that when the actuator displaces the brake piston, the brake pedal does not move towards the floor. The control device detects the actuator element movement and triggers the pressure generator to build pressure proactively, preventing the unusual pedal movement while maintaining the desired clamping force.
2Force
If the actuator displaces the brake piston to increase clamping force, then the parking brake function is improved, but the hydraulic pressure reduces causing the brake pedal to move towards the floor
Solution Approach 1:
The control device continuously monitors the position and movement of the actuator element and adjusts the pressure generator operation accordingly. When the actuator element moves towards the brake piston, the control device detects this movement and triggers the pressure generator to increase hydraulic pressure in response. This feedback mechanism ensures that hydraulic pressure is maintained at the appropriate level throughout the braking process, preventing pedal movement while achieving the required clamping force.
3Stability of the object's composition
If the pressure generator increases hydraulic pressure to maintain brake pedal position, then the pedal stability is improved, but energy consumption increases
Solution Approach 1:
The pressure generator is not operated continuously but rather in periodic, controlled intervals based on actuator element movement detection. The control device triggers the pressure generator only when the actuator element approaches or contacts the brake piston, rather than maintaining constant pressure generation. This periodic operation maintains brake pedal stability while significantly reducing energy consumption compared to continuous pressure generation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution stabilizes the brake pedal behavior during parking brake engagement, preventing unexpected movement and ensuring consistent pressure retention, thereby enhancing driver experience and vehicle safety.
Implementation Method 1
a hydraulic pressure is generated in the brake system or the respective brake circuit, said pressure acting on one or multiple wheel brakes in order to displace a brake piston
Implementation Method 2
The valves of the brake circuit are subsequently closed in such a manner that the pressure can no longer escape from the wheel brake and as a consequence the braking force is maintained
Implementation Method 3
an electromechanical actuator which is allocated to the wheel brake, said actuator having a movable actuator element, in particular a spindle nut, for actuating the wheel brake
Implementation Method 4
An adhesive friction is generated by means of the clamping procedure, said friction acting in a braking manner on the brake disk and thereby on a wheel of the motor vehicle
Data Source
AI summary
A method for operating a hydraulic brake system of a motor vehicle includes enabling a parking brake function by actuating a pressure generator and an actuator such that the pressure generator and the actuator together generate a total clamping force at a wheel brake, and actuating the pressure generator based on a movement of an actuator element and/or a brake piston, the movement generated by the actuator. The brake system includes the wheel brake having the brake piston, a brake pedal device, the pressure generator configured to actuate the wheel brake, the actuator assigned to the wheel brake and having the actuator element configured to actuate the wheel brake. A force that displaces the brake piston in order to actuate the wheel brake is generated by the pressure generator and/or the actuator.