Electrohydraulic Brake Force Boosting in Fallback Mode
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Solution Overview
Problem
In electrohydraulic motor vehicle brake systems, especially in 'brake-by-wire' systems, a failure or defect can lead to deactivation of the electrical brake pressure generator, resulting in excessively long braking distances during fallback modes where the vehicle relies solely on mechanical push-through for braking, as there is no control of the electrical brake-pressure generator.
Innovation Solution
A method and electrohydraulic actuating assembly that determine the required brake force boost by assessing current vehicle deceleration and actuating force, using an electromechanical actuator to provide additive force components to the brake master cylinder, even in mechanical push-through modes, allowing for continuous brake force enhancement without relying on sensor inputs for braking intention detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electrical brake-pressure generator is deactivated in fallback mode, then the system reliability is improved by eliminating sensor dependency, but the braking distance increases excessively
Solution Approach 1:
The system uses self-service by determining the actuating force indirectly through vehicle deceleration measurement and current brake force boost assessment, rather than relying on external sensor inputs. The control unit calculates the required brake force boost based on these parameters, enabling the electromechanical actuator to provide appropriate assistance even in fallback mode without sensor dependency
Solution Approach 2:
The system implements feedback by continuously measuring vehicle deceleration and using this information to determine the actuating force and required brake force boost. The control unit adjusts the electromechanical actuator output based on the measured deceleration and calculated boost requirements, creating a closed-loop control system that maintains effective braking in fallback mode
2Ease of operation
If the mechanical push-through is permanently connected, then the ease of operation is improved by providing direct brake force transmission, but the brake force boost capability is lost in failure modes
Solution Approach 1:
The system applies dynamics by enabling the electromechanical actuator to dynamically adjust and provide brake force boost in addition to the mechanical push-through transmission. The actuator can modulate its output based on measured vehicle deceleration and calculated requirements, transforming the static mechanical connection into a dynamic, adaptive braking system that maintains boost capability even when mechanical push-through is permanently connected
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 ensures reliable brake force boosting in fallback modes, reducing excessively long braking distances and maintaining brake system functionality even in the absence of sensor inputs, thereby enhancing the reliability and usability of 'brake-by-wire' systems and electrohydraulic brake force boosting systems.
Implementation Method 1
controlling an electromechanical actuator, which acts upon the brake master cylinder, to achieve the required brake force boost
Implementation Method 2
an actuating force on a brake pedal acts upon a brake master cylinder of the brake system by means of a mechanical push-through
Data Source
AI summary
The invention relates to a technique for boosting the brake force of an electrohydraulic motor vehicle brake system in a mode in which, as a result of a mechanical push-through, an actuating force onto a brake pedal acts upon a master cylinder of the brake system. According to an aspect of this technique, the method comprises the steps of: determining a value of a first variable indicating a current deceleration of the vehicle; determining, based on the first variable, a value of a second variable indicating the actuating force; determining, based on the second variable, a required brake boost; and controlling an electromechanical actuator acting upon the master brake cylinder to obtain the required brake boost.