Brake Actuator Segmentation for Pedal Feel and Reliability
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Solution Overview
Problem
Existing vehicle brake systems with travel simulators face issues of pedal loss, reliability concerns, and safety risks due to failure of the brake booster, leading to increased pedal forces and potential accidents, while also requiring long installation lengths and complex solutions.
Innovation Solution
The introduction of a further piston-cylinder unit, or auxiliary piston, operated by the actuating device, which is connected to the main cylinder via a current-controlled solenoid valve, allowing for reduced pedal travel losses and improved reliability by providing additional hydraulic volume in case of brake booster failure, and is diagnosable for fault detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a travel simulator is used in the brake system, then the pedal feel is improved and braking comfort is enhanced, but in the event of brake booster failure the pedal loss increases and reliability deteriorates
Solution Approach 1:
The brake system is divided into two independent piston-cylinder units: a first unit with a travel simulator for normal operation, and a second unit without a travel simulator for emergency operation. This segmentation allows the system to provide both comfortable pedal feel during normal braking and reliable direct force transmission during brake booster failure, eliminating the trade-off between these two requirements.
2Reliability
If a mechanical fallback solution is implemented with a solenoid valve to isolate the travel simulator, then reliability is improved, but the device complexity increases and installation length increases
Solution Approach 1:
Instead of adding complex isolation mechanisms to a single piston-cylinder unit, the system is segmented into two independent units from the beginning. The second piston-cylinder unit is designed without a travel simulator, providing a simple mechanical fallback path that directly transmits pedal force to the brake circuit, thereby achieving reliability without increasing device complexity.
3Reliability
If the brake system is designed with a long installation length to accommodate complex fallback solutions, then reliability is improved, but the installation space requirement increases and crash safety is compromised
Solution Approach 1:
The two piston-cylinder units are integrated into a compact arrangement where the second unit is positioned adjacent to the first unit within the same brake system housing. This merging of functions into a unified compact structure provides both normal and emergency braking capabilities while minimizing installation length and improving crash safety by reducing the space between the brake pedal and engine.
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 provides a short installation length, high reliability, and reduced pedal travel losses, enabling the brake system to maintain functionality and safety even in the event of brake booster failure, while allowing for cost and weight savings by operating at lower pressures.
Implementation Method 1
further comprising a solenoid valve, which connects the first piston-cylinder unit and the second piston-cylinder unit to one another in a controllable manner
Implementation Method 2
the at least one working space of which is to be connected to at least one wheel brake of the vehicle via at least one hydraulic line
Data Source
AI summary
An actuating device for a vehicle brake system may include a first piston-cylinder unit, the at least one working space of which is to be connected to at least one wheel brake of the vehicle via at least one hydraulic line, an electromechanical drive device and an actuating device, in particular a brake pedal. Methods for operating a vehicle brake system including such an actuating device and for diagnosing various portions of a vehicle brake system (e.g., but not limited to, a feed valve or a travel simulator) are also presented.