Redundant Brake Booster Layout With Decoupled Piston and ESP
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Solution Overview
Problem
Existing brake systems for autonomous driving and electric vehicles face challenges in achieving high fault tolerance, redundancy, and safety while maintaining optimal braking distance and stability, especially when ESP fails, and require a cost-effective design with reduced complexity and length.
Innovation Solution
A two-box brake system with a compact electric brake booster connected to a standard ESP unit via hydraulic lines, featuring a decoupled main cylinder piston from the motor drive and a parallel pressure supply system, allowing for independent axle-by-axle pressure regulation and reduced pedal travel sensitivity, enabling cost-effective and redundant pressure generation with reduced mechanical load on the motor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a redundant brake system with e-booster and ESP is implemented for autonomous driving, then fault tolerance and safety are improved, but device complexity and construction length increase
Solution Approach 1:
The patent combines the e-booster and ESP units into a single integrated brake system. The electric motor of the e-booster is coupled to the piston-cylinder unit, while the ESP unit shares the same hydraulic circuit and piston structure. This merging reduces the number of separate components and connections, thereby reducing overall system complexity while maintaining both BKV and ESP functions with their required redundancies.
Solution Approach 2:
The piston-cylinder unit serves multiple functions: it acts as the main cylinder for the e-booster, the booster cylinder for the ESP unit, and provides the hydraulic circuit for both BKV and ESP operations. The electric motor and control unit are designed to perform both brake pressure generation (BKV) and pressure modulation (ESP/ABS) functions. This multi-functionality reduces the need for separate dedicated components for each function, simplifying the overall system architecture.
2Reliability
If a redundant brake system with e-booster and ESP is implemented for autonomous driving, then fault tolerance and safety are improved, but the system length and weight increase
Solution Approach 1:
The ESP unit is nested within the e-booster structure. The ESP piston-cylinder unit is integrated into the e-booster's piston-cylinder assembly, with the ESP piston operating within the same hydraulic circuit and physical space as the e-booster components. This nesting arrangement allows the ESP functionality to be accommodated within the existing e-booster footprint, significantly reducing the overall system length compared to a separate ESP unit.
3Ease of operation
If the main cylinder piston is decoupled from the motor drive, then pedal travel characteristics are improved and volume absorption is reduced, but the mechanical connection is complicated
Solution Approach 1:
A travel simulator piston is introduced as an intermediary element between the brake pedal and the main cylinder piston. The travel simulator piston replicates the pedal travel characteristics and provides the necessary mechanical feedback to the driver, while being hydraulically coupled to the main cylinder. This intermediary allows the main cylinder piston to be decoupled from direct mechanical connection to the motor drive, enabling independent optimization of pedal characteristics and volume absorption without compromising the mechanical link.
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
The solution provides a cost-effective, compact, and redundant brake system that maintains optimal braking performance and stability even when ESP fails, with improved pedal characteristics and reduced power requirements, enhancing safety and operational efficiency.
Implementation Method 1
a brake system with a pedal, a piston-cylinder unit, and a hydraulic circuit for brake circuits (BK1, BK2)
Implementation Method 2
The electric motor (8) is coupled to the piston-cylinder unit (THZ, DV)
Implementation Method 3
brake system with a pedal, a piston-cylinder unit, and a hydraulic circuit for brake circuits
Data Source
AI summary
A brake system may include an actuating device, in particular a brake pedal; a first piston-cylinder unit having two pistons subjecting the brake circuits to a pressure medium via a valve device, wherein one of the pistons can be actuated by the actuation device; a second piston-cylinder unit having an electric motor drive, a transmission at least one piston to supply at least one of the brake circuits with a pressure medium via a valve device; and a motor pump unit with a valve device to supply the brake circuits with a pressure medium. The brake system may also include a hydraulic travel simulator with a pressure or working chamber which is connected to the first piston-cylinder unit.