Redundant Hydraulic Brake Pressure Layout for ESP Failure Backup
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Solution Overview
Problem
Existing brake systems for autonomous driving and electric vehicles face challenges in reducing weight and dimensions while ensuring high reliability, safety, and redundancy, particularly in the event of ESP failure, where they often compromise on braking distance and stability.
Innovation Solution
A brake system with a dual pressure supply unit configuration, including an electromotive drive and a motor-pump unit, connected via hydraulic lines and solenoid valves, allowing for selective pressure distribution between brake circuits to ensure redundancy and emergency braking functionality, along with a compact design that eliminates the need for additional components like tandem brake cylinders.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a redundant pressure supply with ESP unit and pump is used to guarantee brake function in autonomous driving mode, then reliability is improved, but device complexity and length increase
Solution Approach 1:
The patent combines the ESP unit with the brake booster function into an integrated system. The ESP unit serves dual purposes: providing pressure supply redundancy for autonomous driving mode and enabling ABS function through pressure modulation. This merging eliminates the need for separate redundant components while maintaining reliability requirements.
Solution Approach 2:
The ESP unit is designed to perform multiple functions: it acts as a redundant pressure supply for autonomous driving, provides ABS pressure modulation capability, and enables backup braking functionality. This multi-functionality reduces overall system complexity while meeting multiple safety requirements simultaneously.
2Reliability
If BKV motor is used for pressure modulation to enable ABS function, then ABS functionality is achieved, but braking distance optimization is limited due to common pressure control for all wheels
Solution Approach 1:
The system dynamically switches between different pressure control modes. The ESP unit can operate in autonomous driving mode with full redundancy, in ABS mode with pressure modulation capability, or in backup mode. This dynamic adaptability allows optimal braking performance for different operating conditions while maintaining ABS functionality.
3Ease of operation
If e-booster with follow-up booster function is used for BKV control, then brake assistance is provided, but pedal travel becomes excessively long in case of fading or brake circuit failure
Solution Approach 1:
The system incorporates a travel simulator that provides haptic feedback to the driver before actual brake circuit failure occurs. This cushioning mechanism maintains realistic pedal feel and travel characteristics by simulating the mechanical feedback that would normally come from the brake circuits, even when they fail or fade.
4Reliability
If multiple pistons and solenoid valves are used in brake booster with ESP unit, then redundant pressure supply is achieved, but assembly length and complexity increase
Solution Approach 1:
The patent implements a nested arrangement where the ESP unit is positioned within or alongside the brake booster assembly. The pump, motor, and control valves are integrated into a compact configuration that utilizes the existing brake booster structure, thereby achieving redundancy without proportionally increasing overall assembly length.
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 compact, reliable, and safe brake system that maintains optimal braking performance and stability even in the event of ESP failure, with reduced weight and dimensions, and supports advanced driver assistance functions.
Implementation Method 1
a first pressure supply unit, having an electromotive drive which is configured to supply a pressure medium to at least one brake circuit and at least one second brake circuit
Implementation Method 2
a motor-pump unit, which is configured to supply the pressure medium to at least one of the brake circuits
Implementation Method 3
a second pressure supply unit, which configured to supply the pressure medium to at least one of the brake circuits, wherein the second pressure supply unit is connected to the motor-pump unit via at least one first hydraulic line and via at least one second hydraulic line
Implementation Method 4
The valve unit comprises at least one feed valve, via which the third hydraulic line can be at least partially reversibly shut off, wherein an isolating valve is arranged in at least one of the hydraulic lines
Data Source
AI summary
A brake system may include a first pressure supply unit having an electromotive drive and arranged to supply pressure medium to first and second brake circuits; a motor-pump unit to supply pressure medium to at least one of the brake circuits; a second pressure supply unit, connected to the motor-pump unit via first and second hydraulic lines and arranged to supply pressure medium to at least one of the brake circuits; and a valve unit. The second pressure supply unit may be connected via a third hydraulic line to at least one of the brake circuits. The valve unit may include at least one feed valve via which the third hydraulic line may be at least partially reversibly shut off. An isolating valve may be disposed in at least one of the hydraulic lines to at least partially reversibly shut off the at least one hydraulic line.