Brake System Pressure Control via Segmented Valve Overflow
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Solution Overview
Problem
Existing brake systems, particularly 'brake-by-wire' systems, face challenges in achieving finely metered control of brake pressures while minimizing noise generation, often resulting in significant noise due to high-frequency actuator reversals and rapid multiplex valve operations.
Innovation Solution
The method involves initially closing all inlet valves and building up pressure in specific groups of wheel brakes by overflowing only the relevant inlet valves, using an electrically controllable pressure supply device, with control characteristics determined to ensure precise control and minimize noise. Outlet valves are used for independent pressure reduction, maintaining the brake system pressure higher than the wheel brakes to prevent pressure medium escape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-frequency actuator reversals and rapid multiplex valve operations are used to achieve finely metered brake pressure control, then brake pressure control precision is improved, but noise generation increases significantly
Solution Approach 1:
The brake system is divided into multiple brake circuits with independent pressure control. Each brake circuit has its own pressure control valve that can be controlled independently, allowing precise pressure control without requiring high-frequency switching of a single multiplex valve. This segmentation eliminates the need for rapid valve operations that generate noise.
Solution Approach 2:
The patent uses periodic actuation of pressure control valves in a controlled sequence rather than continuous high-frequency switching. The valves are actuated in a rhythmic pattern that allows pressure to build and equalize between cycles, reducing impact noises while maintaining precise pressure control through the periodic adjustment of brake pressures in different circuits.
2Speed
If pressure control valves are actuated rapidly to build up brake pressure quickly, then brake response speed is improved, but impact noises from valve operations increase
Solution Approach 1:
The system pre-charges accumulators with hydraulic fluid before brake application is needed. When brake pressure is required, the pre-charged accumulators can immediately supply pressure without requiring rapid valve opening, thus achieving fast brake response without the impact noises associated with sudden valve operations.
Solution Approach 2:
Accumulators serve as intermediary energy storage devices between the hydraulic pump and the brake circuits. They buffer the pressure supply, allowing smooth pressure buildup without direct coupling between the pump and brakes, thereby eliminating impact noises from rapid valve actuation while maintaining fast response through the stored hydraulic energy.
3Measurement precision
If multiplex valves are opened and closed in rapid succession to control individual wheel brakes, then individual wheel brake pressure control is improved, but noise from valve impact increases
Solution Approach 1:
Instead of using a single multiplex valve that must switch rapidly between different wheel brakes, the system segments the control function by providing dedicated pressure control valves for each brake circuit. This allows each valve to control its associated brakes continuously without rapid switching, achieving precise individual wheel brake pressure control without the impact noises of multiplex valve operations.
Solution Approach 2:
Rather than closing valves rapidly to control pressure (which causes impact noise), the system inverts the approach by using normally open valves that remain open and only close when pressure control is needed. This reversal of the normal valve operation mode reduces the frequency of rapid closures and associated impact noises while maintaining precise pressure control capability.
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 approach significantly reduces impact noises from intake valves, allows precise control of brake pressures, and prevents pressure medium escape, resulting in a quieter and more accurate brake pressure management system.
Implementation Method 1
the electromagnetic force generated by the solenoid is equal to the biasing force of the valve spring
Implementation Method 2
a pressure build-up to a predetermined pressure value in a predetermined group of one or more wheel brakes is carried out by shifting a pressure medium volume into the predetermined group of wheel brakes
Implementation Method 3
a sum of the force based on the fluid pressure difference and the electromagnetic force generated by the solenoid is equal to the biasing force of the valve spring
Data Source
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AI summary
The invention relates to a method for operating a brake system for motor vehicles, comprising several wheel brakes (8, 9, 10, 11), an electrically controllable pressure supply device (5, 100), which can dispense a determinable pressure medium volume (V) for actuating the wheel brakes, and an analogized or analog-controlled inlet valve (6a-6d), which is arranged in each wheel brake between the pressure supply device and the wheel brake, for adjusting wheel-individual brake pressures (pn). A check valve (50a-50d) is connected in each case in parallel to the inlet valves, which opens in the direction of the pressure supply device, wherein, at the start of a wheel-individual brake pressure control, all the inlet valves (6a-6d) are closed, and wherein a pressure build-up is carried out in a predetermined group (A1, A2) of one or more wheel brakes (8, 11, 8, 11) by displacing a pressure medium volume (VA) into the predetermined group (A1, A2) of wheel brakes by means of the pressure supply device (5, 100). Each inlet valve of the one or more wheel brakes (8, 11, 8, 11) of the predetermined group (A1, A2) is controlled in such a way that the inlet valve is overflowed, wherein each inlet valve of the remaining wheel brakes (9, 10, 11, 8, 9, 10, 9, 10) is controlled in such a way that the inlet valve remains closed. The invention also relates to a brake system.