Electrohydraulic Brake System Dynamic Gap Control
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Solution Overview
Problem
Existing electrohydraulic vehicle brake systems face challenges in minimizing hydraulic components while maintaining effective pressure modulation and avoiding unwanted pressure equalization, particularly with the reduction of valves to a single 2/2-way valve per wheel brake.
Innovation Solution
An electrohydraulic motor vehicle brake system with a master cylinder and an electromechanical actuator that includes a gap in the power transmission path between the brake pedal and the piston, where the gap length is dependent on pedal travel, allowing for decoupling and hydraulic actuation, and featuring a mechanical actuator for push-through mode and a hydraulic simulation device for pedal reaction behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the number of hydraulic valves is minimized to a single 2/2-way valve per wheel brake, then the device complexity is reduced, but unwanted pressure equalization occurs when valves are open simultaneously
Solution Approach 1:
The patent implements a highly dynamic electromechanical actuator that can rapidly open and close valves in a time-division multiplexed manner. This dynamic control ensures that only one valve is open at any given time, preventing pressure equalization while maintaining the minimized valve configuration. The actuator's high-speed response capability allows it to switch between wheels faster than the hydraulic pressure can equalize, thus resolving the contradiction between few valves and reliable pressure control.
2Device complexity
If an electromechanical actuator acts directly on the master cylinder piston, then the hydraulic components can be reduced, but safety risks increase due to potential failure modes
Solution Approach 1:
The patent segments the brake system into two independent channels, each with its own electromechanical actuator and master cylinder piston. This segmentation ensures that a failure in one channel does not compromise the other, maintaining safety while reducing overall hydraulic component complexity. Each channel can operate independently, providing redundancy and fail-safe operation.
Solution Approach 2:
The patent incorporates a mechanical actuator that can be actuated by a brake pedal as a backup system. This mechanical actuator serves as a cushioning measure against electromechanical actuator failure. In the event of electrical or electronic failure, the mechanical actuator can still provide braking force through direct mechanical action on the master cylinder piston, thus beforehand preparing for potential failure modes and maintaining safety.
3Adaptability or versatility
If a gap is introduced in the power transmission path between brake pedal and piston, then decoupling is achieved for hydraulic actuation, but mechanical actuation capability is reduced
Solution Approach 1:
The patent makes the gap length dynamic rather than fixed. The gap can be adjusted based on the operating mode: in normal hydraulic braking mode, the gap is maintained to allow independent electromechanical actuation; in emergency mechanical braking mode, the gap can be closed or reduced to restore direct mechanical force transmission from the brake pedal to the piston. This dynamic adjustment resolves the contradiction between decoupling capability and mechanical force transmission.
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 configuration enhances safety by providing controlled brake pressure modulation and haptic feedback, while reducing the risk of unwanted pressure equalization and allowing for efficient hydraulic fluid management, thereby improving the overall performance and reliability of the brake system.
Implementation Method 1
The gear arrangement consists of a ball screw drive with a ball screw nut coupled in a torque-proof manner to a rotor of the electric motor and a ball screw spindle acting on the tandem piston
Implementation Method 2
a master cylinder with at least one piston accommodated therein so that it can be displaced... actuating the piston in a 'push-through', PT, mode
Data Source
AI summary
The invention relates to an electrohydraulic motor vehicle brake system. The brake system comprises a master cylinder, an electromechanical actuator for actuating a piston, which is accommodated in the master cylinder, in a brake-by-wire (BBW) mode of the brake system, and a mechanical actuator, which can be actuated by means of a brake pedal, for actuating the piston in a push-through (PT) mode of the brake system. In the BBW mode, a gap having a defined gap length is present in a force transmission path between the brake pedal and the piston for decoupling the brake pedal from the piston. The brake system is configured such that in the BBW mode the gap length is dependent on a pedal travel of the brake pedal.