Hydraulic Unit Vacuum Prevention Piston
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Solution Overview
Problem
The existing hydraulic units for motor vehicle brake systems face challenges in achieving rapid pressure reduction in wheel brakes to prevent wheel locking during conventional and regenerative braking, while also avoiding the creation of vacuum in wheel brakes without relying on a stiff check valve spring, which requires high hydraulic actuating forces and complicates the design.
Innovation Solution
The hydraulic unit design incorporates a piston with a spring that separates the pressure medium chamber from the second connection, allowing pressure medium to be discharged into the chamber only when sufficient pressure is released, eliminating the need for a strong check valve spring, and features a compact sealing element and non-return valve assembly to manage hydraulic connections efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a stiff check valve spring is used to prevent pressure medium flow into the low-pressure accumulator, then vacuum formation in wheel brakes is prevented, but high hydraulic actuating force is required and the design becomes complicated
Solution Approach 1:
The patent removes the check valve spring from the system entirely. Instead of using a spring-loaded check valve, the invention employs a simple non-return valve with a valve ball and conical valve seat that relies on the pressure differential itself to open and close, eliminating the need for a stiff spring and its associated complexity
Solution Approach 2:
The patent introduces a non-return valve as an intermediary element between the wheel brake circuit and the low-pressure accumulator. This valve mediates the pressure differential to control fluid flow direction without requiring active control elements or stiff springs
2Reliability
If a strong piston spring is used to enable self-emptying of the low-pressure accumulator, then the accumulator can overcome the check valve closing force, but high hydraulic actuating force is required during brake slip control
Solution Approach 1:
The patent removes the piston spring from the system. Instead of using a spring-loaded piston, the invention employs a piston that moves freely based on pressure differential, with sealing provided by an elastic sealing element that deforms under pressure to maintain seals without requiring spring force
Solution Approach 2:
The piston system serves itself by utilizing the pressure differential between the low-pressure accumulator and the wheel brake circuit to automatically move the piston and open/close the non-return valve, eliminating the need for external spring forcing
3Adaptability or versatility
If the outlet valves are open during regenerative braking to allow brake fluid diversion into the low-pressure accumulator, then regenerative braking is enabled, but rapid pressure reduction in wheel brakes becomes difficult
Solution Approach 1:
The non-return valve acts as a mediator that allows bidirectional communication between the wheel brake circuit and low-pressure accumulator while maintaining unidirectional flow control. During regenerative braking, it allows fluid to flow into the accumulator; during emergency braking, it allows rapid fluid return to the wheel brakes
Solution Approach 2:
The system dynamically adapts its flow characteristics based on operating conditions. The non-return valve automatically changes its flow state depending on the pressure differential, enabling both regenerative braking mode and rapid pressure reduction mode without mechanical intervention
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 design enables rapid pressure reduction in wheel brakes, prevents vacuum formation, and reduces the hydraulic actuating force required, ensuring priority of brake pressure to the low-pressure accumulator over wheel brakes, thus enhancing braking control and dynamics.
Implementation Method 1
an elastic sealing element is provided between the piston and the second connection, which separates the hydraulic connection provided between the second connection and the pressure medium chamber in the basic position of the piston
Implementation Method 2
a piston with a spring that separates the pressure medium chamber from the second connection, allowing pressure medium to be discharged into the chamber only when sufficient pressure is released
Implementation Method 3
a nonreturn valve that blocks in the direction of the pressure medium chamber
Data Source
Figure 1
Figure 2
AI summary
The invention relates to a hydraulic unit for a motor vehicle brake system which operates according to the feedback principle, for which purpose a low-pressure accumulator (26) is provided between the outlet valves (23) of the wheel brakes (21) and a pump (27), and the piston (3) of which low-pressure accumulator, in the basic position, disconnects the hydraulic connection between a pressure medium chamber (4) and a connection (2) leading to the pump (27) such that, in the empty state of the low-pressure accumulator (26), the wheel brakes (21) are reliably disconnected from the suction side of the pump.