Bistable Control Valve for Electric Parking Brake
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Solution Overview
Problem
Electrically actuated parking brake systems require absolute switching reliability, especially at low temperatures, to prevent unintended state changes during power failures and ensure safety, while minimizing wear on system components.
Innovation Solution
Incorporating a throttle between the control input and the second working connection of the pneumatic control valve device creates a temporary pressure difference, allowing dynamic switching without relying on static pressure states, and using only two radial seals for the control piston to reduce frictional forces, thereby ensuring bistability and design freedom.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a control valve device is designed with sufficient effective surfaces to ensure switching against spring force, then switching reliability is improved, but the valve device requires static pressure states that increase frictional forces and wear
Solution Approach 1:
The patent applies dynamic switching by introducing a throttle between the control input and second working connection, creating a temporary pressure difference during state transitions. This dynamic approach allows the control piston to switch states without requiring excessive effective surfaces, thereby reducing frictional forces on the radial seals while maintaining switching reliability through controlled pressure dynamics rather than static pressure balance
Solution Approach 2:
The patent changes the pressure parameter dynamically during switching by using a throttle to create a temporary pressure difference between the control input and second working connection. This parameter change enables the control piston to overcome spring force and frictional forces during transition, achieving reliable switching without requiring the valve device to be designed for static pressure states that would increase wear
2Reliability
If the control valve device is designed to switch safely at low temperatures, then switching reliability is improved, but the frictional forces increase due to temperature effects
Solution Approach 1:
The dynamic switching mechanism using a throttle creates a temporary pressure difference that provides additional force to overcome the increased frictional forces at low temperatures. This dynamic approach ensures reliable switching across a wide temperature range without requiring the valve device to be oversized for worst-case friction conditions
Solution Approach 2:
The throttle creates a preliminary pressure difference that counteracts the increased frictional forces before switching occurs at low temperatures. This preliminary anti-action ensures that the control piston can overcome the temperature-dependent friction and spring force to achieve reliable state transitions
3Reliability
If radial seals are used for controlling the control piston, then sealing is improved, but frictional forces increase during switching
Solution Approach 1:
The dynamic switching approach using a throttle reduces the pressure difference that radial seals must withstand during switching, thereby reducing frictional forces while maintaining sealing effectiveness. The temporary pressure difference created by the throttle allows switching to occur with lower seal friction than would be required under static pressure conditions
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 guarantees absolute switching reliability and minimizes wear on the control valve device, maintaining the parking brake state during power failures and preventing unintended transitions between states, while allowing for greater design flexibility and reduced frictional forces.
Implementation Method 1
creates a temporary pressure difference between the control input and the second working connection
Implementation Method 2
a throttle is provided between the control input and the second working connection
Implementation Method 3
the venting port is coupled to a control and venting valve device, the control and venting valve device is suitable for ventilating the venting port
Implementation Method 4
taking into account one of the control pistons The spring force driving it into its second switching state
Implementation Method 5
which reduces the frictional forces that have to be overcome when switching
Data Source
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AI summary
The invention relates to an electrically actuated parking brake system for a pneumatic brake system, with a bistable control valve assembly (22). At least one throttle (118) is provided. This ensures dynamic pressure conditions in the system during the switching of a control and venting valve assembly (72), at which the control valve assembly (22) switches.