Valve Device Switching Reliability Low Temperature Friction
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Solution Overview
Problem
Pneumatically driven switching valve devices in electrically operable parking brake systems face challenges in maintaining absolute switching reliability, especially at low temperatures due to high friction forces, which can lead to unintended vehicle movement.
Innovation Solution
A valve device with a displaceable valve seat and radial seals, where the valve seat follows the pilot piston during initial movement, reducing static friction, and a spring force aids in overcoming adhesion, while a stop limits further movement to ensure reliable switching, and an active surface in the air bleed space enhances sealing and reduces wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pneumatically driven switching valve device is used in an electrically operable parking brake system, then the system can achieve reliable switching between drive and park modes, but at low temperatures high friction forces prevent reliable switching and can lead to unintended vehicle movement
Solution Approach 1:
The patent applies preliminary action by introducing compressed air into the air bleed space before the switching operation is required. This pre-pressurization creates a force that acts on the valve seat to reduce static friction and adhesion forces between the valve seat and pilot piston, ensuring the valve can switch reliably even at low temperatures where friction would normally be too high
Solution Approach 2:
The patent uses compressed air as an intermediary substance to mediate between the pneumatic control input and the valve seat. The air pressure in the air bleed space acts as a mediator force that reduces the adhesion between the valve seat and pilot piston, enabling reliable switching without direct mechanical contact forces that would be affected by temperature
2Ease of manufacture
If the valve seat is made stationary to simplify the structure, then manufacturing is easier, but the pilot piston experiences high static friction and adhesion forces that prevent reliable switching at low temperatures
Solution Approach 1:
The patent applies dynamics by making the valve seat displaceable rather than stationary. The valve seat can move axially in response to pressure changes in the air bleed space, allowing it to follow the pilot piston during initial movement. This dynamic capability reduces static friction forces while maintaining a simple structure where the valve seat is guided by a stop
3Device complexity
If the pilot piston is designed to move directly against a stationary valve seat, then the switching mechanism is simple, but abrasive wear occurs between the pilot piston and valve seat
Solution Approach 1:
The patent reduces wear by making the valve seat dynamic rather than stationary. The valve seat follows the pilot piston's initial movement, which converts static friction into dynamic friction and significantly reduces abrasive wear between the sealing surfaces. The valve seat is constrained by a stop to maintain proper positioning after the initial movement
Solution Approach 2:
The compressed air in the air bleed space acts as an intermediary that reduces direct contact forces between the pilot piston and valve seat. By pressurizing the air bleed space, a force is generated that pushes the valve seat away from the pilot piston, reducing adhesion and abrasive wear during switching operations
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
Ensures reliable and defined switching of the parking brake system between drive and park modes, maintaining safety and reducing abrasive wear, even at low temperatures.
Implementation Method 1
a pilot piston, which is guided in an axially displaceable manner in the valve housing by way of radial seals
Implementation Method 2
the pilot piston is lifted from the first valve seat by a spring force
Data Source
AI summary
A valve device is provided for a pneumatic brake system of a commercial vehicle and comprises a pilot piston, radial seals and at least one valve seat, which can be displaced in the direction of motion of the pilot piston.