By-Wire Brake Circuit Separation for Leak-Tolerant Fallback Braking
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Solution Overview
Problem
Existing by-wire electronic braking systems face challenges in maintaining operation when a leak occurs, potentially damaging the ECU and failing to generate sufficient braking pressure due to the lack of a tandem master cylinder and effective circuit separation mechanisms.
Innovation Solution
A brake system incorporating a tandem master cylinder with normally open, electrically actuated inlet valves, electrically controllable linear actuators, and a normally closed circuit separation valve, allowing pressure redistribution between two independent line sections to maintain braking functionality even when one circuit leaks and the ECU is inoperable.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If a single master cylinder circuit is used with circuit separation valve, then by-wire operation can be maintained longer with comfortable braking, but the system cannot generate enough pressure when a leak occurs and ECU may be damaged
Solution Approach 1:
The system divides the braking circuit into two independent circuits using a tandem master cylinder, where the first circuit connects to the brake pedal and the second circuit connects to the linear actuator. This segmentation ensures that a leak in one circuit does not compromise the other, allowing the system to maintain braking pressure generation capability even when one circuit fails.
Solution Approach 2:
The system prepares for potential failures by having redundant pressure sources (both the brake pedal-driven master cylinder and the linear actuator) ready to provide braking pressure. The circuit separation valve is pre-configured to isolate circuits, and the control unit is programmed to automatically switch to degraded mode with mechanical fallback when a leak is detected, ensuring continuous braking capability without ECU damage.
2Reliability
If leak monitoring and management is implemented to locate leak location, then proper degraded operation mode can be determined, but the system requires complicated monitoring and management mechanisms
Solution Approach 1:
The system extracts the leak detection function from complex monitoring mechanisms and implements it through simple pressure sensors that detect pressure differences between the two circuits. When a pressure difference is detected, the system automatically determines the degraded operation mode and activates the appropriate fallback mechanism, eliminating the need for complicated leak location determination.
Solution Approach 2:
The system uses the existing hydraulic pressure in the two circuits as the monitoring mechanism itself. The pressure sensors continuously monitor the circuits, and when a leak is detected, the system automatically switches to degraded mode with mechanical fallback, providing self-diagnosis and self-correction without requiring complex external monitoring systems.
3Reliability
If mechanical fallback operation is activated by switching off motor-powered pressure provider, then the system can operate with higher pedal effort, but the driver experiences higher force and longer stroke requirements
Solution Approach 1:
The system prepares for potential linear actuator failure by having the brake pedal-driven master cylinder ready to provide braking pressure through the circuit separation valve. When the linear actuator fails or a leak is detected, the system automatically switches to degraded mode where the mechanical pedal system provides braking pressure, ensuring continuous braking capability though with increased pedal effort.
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
Enables continued braking operation with reduced pedal effort and pressure maintenance, even when a non-catastrophic leak causes ECU inoperability, by redirecting pressure from the tandem master cylinder to unaffected wheel brakes, thus preventing complete hydraulic failure.
Implementation Method 1
A manually actuated brake pedal is configured to operate the tandem master cylinder. A brake supply line is hydraulically connected with each of the first and second pressure chambers via respective first and second, normally open and electrically operated separation valves
Implementation Method 2
An electrically controllable linear actuator has a pressure chamber hydraulically connected to the brake supply line via a normally closed, electrically operated connection valve. A reservoir contains a pressure medium for supplying the first and second pressure chambers of the tandem master cylinder and the pressure chamber of the linear actuator
Implementation Method 3
A normally closed, electrically operated circuit separation valve is provided in the brake supply line separating, in the normally closed condition thereof, the brake supply line into a first line section hydraulically communicating the second pressure chamber of the tandem master cylinder with only the inlet valves associated with the front wheel brakes, and a second line section hydraulically communicating the pressure chamber of linear actuator with only the inlet valves associated with the second pair of wheel brakes
Data Source
AI summary
A brake system for a motor vehicle comprises a normally closed circuit separation valve such that the system is configured to operate in 1) in a by-wire mode when the circuit separation valve is open, such that pressure only from a pressure chamber of a linear actuator is delivered to both first and second pairs of wheel brakes, and 2) in a circuit separation mode with the circuit separation valve in the normally closed position, such that pressure from a tandem master cylinder is delivered only to the first pair of wheel brakes, and such that pressure from the pressure chamber of the linear actuator is concurrently delivered only to the second pair of wheel brakes. The system can provide braking pressure even in the event of a by-wire braking module leak that causes inoperability of an ECU.