Brake-By-Wire Hydraulic Volume Relief Without Outlet Valve Noise
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Solution Overview
Problem
In electrohydraulic 'brake-by-wire' systems, surplus brake fluid volume mismatch leads to noise and driver disturbance when outlet valves are opened to dissipate excess volume, potentially causing irritation and leakage, especially under slight pressure differences.
Innovation Solution
The braking system incorporates a secondary pressure chamber and a normally open separating valve that redirects surplus brake fluid into the secondary pressure chamber, allowing it to flow back into the reservoir through 'blow holes' when the brake pedal is released, minimizing noise and valve wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If outlet valves are opened to dissipate surplus brake fluid volume, then the hydraulic volume balance is restored, but noise is generated causing driver disturbance and potential leakage
Solution Approach 1:
The patent introduces a simulator as an intermediary component between the master brake cylinder and the wheel brakes. The simulator absorbs surplus brake fluid volume through its compressible air chamber, acting as a mediator that prevents the need to open outlet valves. This resolves the contradiction by providing a third element that handles the volume imbalance without generating noise or causing driver disturbance.
Solution Approach 2:
The patent utilizes the compressibility parameter of the air chamber in the simulator to dynamically absorb volume changes. By changing the physical state parameter (compressibility) of the air chamber, the system can accommodate surplus brake fluid volume without requiring valve operations, thereby eliminating noise while maintaining hydraulic balance.
2Reliability
If outlet valves are opened frequently to dissipate surplus volume, then hydraulic balance is maintained, but valve wear increases reducing lifespan
Solution Approach 1:
The simulator serves as a intermediary that absorbs volume surpluses through its compressible air chamber, preventing frequent outlet valve operations. This mediator role reduces mechanical wear on the outlet valves while maintaining hydraulic balance, extending valve lifespan without compromising system reliability.
Solution Approach 2:
The simulator's air chamber automatically absorbs and releases brake fluid volume based on system pressure conditions without requiring active control or valve operations. This self-service mechanism handles volume balancing passively, minimizing outlet valve activation and reducing wear while maintaining hydraulic equilibrium.
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 method effectively dissipates surplus brake fluid volume without noise, reducing driver disturbance and extending valve lifespan by minimizing outlet valve activation, maintaining a balanced hydraulic volume without opening the outlet valves.
Implementation Method 1
the second separating valve is opened in the by-wire operating mode if a release of the brake pedal by the driver is detected, so that surplus pressure medium can flow into the secondary pressure chamber
Implementation Method 2
The actual braking is thus achieved by active pressure build-up in the brake circuits by means of the pressure-providing device
Implementation Method 3
The hydraulic volume displaced from the master brake cylinder by the driver by pedal actuation flows into the simulator
Data Source
AI summary
A braking system for vehicles includes wheel brakes, a pressure-providing device for actuating the wheel brakes, a master brake cylinder having a primary pressure chamber, a secondary pressure chamber, and a secondary piston. The primary pressure chamber is separated from a first set of the wheel brakes by a first, normally open separating valve, and the secondary pressure chamber is separated from a second set of the wheel brakes by a second, normally open separating valve. A pressure medium reservoir is connected to the secondary pressure chamber in the unactuated state of the secondary piston, the braking system is activated in order to actively build up pressure in the brakes in a by-wire operating mode by the pressure-providing device. In the event of a pressure medium surplus in the wheel brakes, the second separating valve is opened if a release of the brake pedal by the driver is detected.