Brake Control Valve Bistable Pressure Design
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Solution Overview
Problem
Existing brake control valves for commercial vehicles fail to maintain a bistable brake control pressure effectively, leading to unintentional release of the parking brake due to vibrations, which can cause the vehicle to roll away, and require multiple valve seats for operation, complicating the design and increasing the risk of failure.
Innovation Solution
A brake control valve design with a switching element coupled to an electric motor via a self-locking drive, positioned between the supply and vent ports, and an additional valve seat to separate the supply and brake control pressure connections, ensuring bistable pressure settings and improved safety by preventing unintentional pressure changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two different valve seats are used to generate bistable brake control pressure with a single switching element, then the brake control pressure can be switched between high and low states, but the device complexity increases and the reliability decreases due to more potential failure points
Solution Approach 1:
The patent merges the functions of two separate valve seats into a single integrated valve seat structure. The switching element interacts with one valve seat that has two distinct sealing surfaces or regions, allowing the same switching element to control both the supply connection and vent connection to the brake control pressure chamber. This reduces the number of separate valve seats from two to one, simplifying the device structure while maintaining the bistable pressure control function.
Solution Approach 2:
The single valve seat is designed with multi-functionality, serving both as the supply valve seat and the vent valve seat. The switching element, when in different positions, seals against different regions of the same valve seat - one region controls the supply port connection to the brake control pressure chamber, while the other region controls the vent port connection. This universal valve seat design eliminates the need for separate valve seats and reduces overall device complexity.
2Device complexity
If the supply port and vent port are located on the same side of the channel, then the valve structure is compact, but the brake control pressure switches abruptly between high and low states causing unintentional parking brake release due to vibrations
Solution Approach 1:
The patent transitions from a two-dimensional arrangement where supply and vent ports are on the same side of the channel to a three-dimensional configuration. The valve seat is positioned at an angle or in a different spatial plane relative to the switching element's movement path. This dimensional change creates a more gradual transition zone where the switching element progressively seals off the supply port while opening the vent port, preventing abrupt pressure changes and the associated reliability issues with vibration-induced unintended brake release.
3Device complexity
If a single switching element controls both supply and vent connections, then the device complexity is reduced, but the risk of unintentional pressure changes increases without proper positioning
Solution Approach 1:
The patent introduces an intermediary chamber or transition zone between the supply port and vent port connections. The switching element does not directly switch between fully open supply and fully closed vent positions; instead, it moves through an intermediary state where the brake control pressure chamber is gradually transitioned from supply pressure to vented state. This intermediary transition prevents abrupt pressure changes that could cause unintended parking brake release, maintaining reliability while using only a single switching element.
Data Source
Figure 1
Figure 2
AI summary
The valve (10) has an electromotor (18) coupled over a self-locking drive (20) i.e. linear jackscrew actuator, with a movable shift element (16), which is movable in an axial direction (14) opposite to a valve housing (12). Valve seats (22, 24) are spaced apart from one other in the axial direction and arranged opposite to the valve housing. The shift element tightly abuts in the valve seats in a shift position (26) and another shift position, respectively, and is moveable relative to a carriage (30) in the axial direction. The drive is coupled over the carriage with the shift element.