Electrohydraulic Braking Pre-Pressure Control
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Solution Overview
Problem
Existing 'brake-by-wire' systems for motor vehicles lack an efficient method for controlling electro-hydraulic braking systems with electrically controllable pressurization devices, particularly in managing pre-pressures for various brake control functions like ABS, TCS, and ESP, which require precise pressure distribution across wheels.
Innovation Solution
A method and device for controlling an electro-hydraulic braking system using a cylinder-piston arrangement with an electrically activated inlet and outlet valve system, allowing for dynamic setting of pre-pressures in the pressure chamber based on driver requests and assist functions, with a suction cycle mechanism to manage pressure distribution across wheels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If pre-pressure is set too high in the pressure chamber, then brake pressure can be built up quickly, but fluid may need to be discharged from the reservoir which takes time and reduces system responsiveness
Solution Approach 1:
The patent implements dynamic control of the pressurization device piston position based on real-time braking requirements. The control unit continuously adjusts the piston position to maintain optimal pre-pressure levels, allowing the system to rapidly build pressure when needed while avoiding excessive pressure that would require time-consuming discharge operations. This dynamic adjustment optimizes both response speed and efficiency.
2Quantity of substance
If the piston is traversed by a large amount in the suction cycle, then more brake fluid can be drawn from the reservoir, but the piston may reach its limit position and require system reset
Solution Approach 1:
The control unit continuously monitors the piston position and brake fluid pressure levels, using this feedback information to dynamically adjust the suction cycle parameters. When the piston approaches its limit position or when sufficient fluid has been drawn, the control unit modulates the suction cycle to prevent excessive travel, thereby maintaining optimal operation without requiring system resets while ensuring adequate fluid supply.
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
Enables efficient and precise control of brake pressures across all wheels, ensuring reliable operation under various braking conditions, including ABS, TCS, and ESP, by dynamically adjusting pre-pressures and managing fluid volume to prevent under-braking and maintain optimal wheel slip.
Implementation Method 1
an electric motor-driven piston (3) which, in a cylinder, generates a central pre-pressure for the wheel brakes of a motor vehicle
Implementation Method 2
an inlet valve (6), which serves for allowing brake fluid to flow from a reservoir (11) into the cylinder (4)
Implementation Method 3
an outlet valve (7), which serves for allowing brake fluid to flow from the cylinder (4) back into the reservoir (11)
Data Source
AI summary
A method for controlling an electro-hydraulic braking system for motor vehicles, including providing an antilock control function, and a further brake pressure control function which can be activated in a “brake-by-wire” mode. A pressurization device, activated by an electronic control unit can be connected to hydraulically actuated wheel brakes through at least one pressure regulating valve. The pressurization device having a cylinder-piston arrangement with a chamber, the piston of which can be displaced relative to a rest position by an electromechanical actuator. A set pressure value is determined for each wheel brake activating the cylinder-piston arrangement such that a predetermined pre-pressure, which is determined from the set pressure values, is set in the chamber by displacement of the piston.