Dual-Piston Relay Valve Anti-Compounding Design
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Solution Overview
Problem
Current relay valves in commercial vehicle brake systems experience overloading of brake calipers when the parking brake and service brake are actuated simultaneously, due to inadequate balancing of forces, leading to potential roll-back issues, especially on inclines, and require complex valve configurations to manage pressure.
Innovation Solution
An axially movable service brake piston is positioned between the parking brake piston and the sleeve, forming a second compressed air chamber, allowing direct air pressure application without offset, eliminating the need for additional valves like select high valves, and creating a more linear force balancing, thus enhancing the anti-compound function and reducing assembly complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a select high valve is installed in the control line to provide anti-compound function, then the brake calipers are protected from overloading, but the device complexity increases and the response time is delayed
Solution Approach 1:
The patent combines the anti-compound function directly into the relay valve by integrating a service brake piston with a parking brake piston. The service brake piston receives service brake pressure and balances it against the parking brake spring force, eliminating the need for a separate select high valve. This merging of functions reduces device complexity while maintaining the anti-compound protection.
Solution Approach 2:
The service brake piston is positioned to receive service brake pressure in advance, before it can affect the parking brake caliper. The piston pre-balances the forces by allowing service brake pressure to act on its surface, creating a counteracting force that prevents overloading of the parking brake caliper springs before compounding can occur.
2Reliability
If a select high valve is used for anti-compound function, then brake caliper overloading is prevented, but the activation speed is reduced
Solution Approach 1:
The service brake piston receives service brake pressure directly and immediately, allowing the anti-compound balancing force to be established as soon as service brake pressure is applied. This eliminates the sequential delay inherent in select high valve systems where pressure must first build in the control line before affecting the relay valve.
Solution Approach 2:
The service brake piston acts as a direct intermediary between service brake pressure and the parking brake force balance. Instead of using a select high valve to compare pressures sequentially, the piston directly translates service brake pressure into a counteracting force on the parking brake spring, accelerating the anti-compound response.
3Reliability
If additional valves like select high valves are installed, then anti-compound function is achieved, but the space requirements and assembly complexity increase
Solution Approach 1:
The patent merges multiple functions into a single relay valve assembly. The relay valve simultaneously controls brake pressure application and provides anti-compound protection through the integrated service brake piston. This eliminates the need for separate select high valves and reduces the overall space required for the brake control system.
Solution Approach 2:
The relay valve is designed with multi-functionality, serving both as a pressure control device and an anti-compound protection device. The service brake piston within the relay valve performs the anti-compound function while the relay valve itself manages brake pressure application, creating a universal component that replaces multiple specialized valves.
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 configuration achieves quicker anti-compound function activation, reduces space and assembly requirements, and prevents brake caliper overloading by ensuring balanced forces, thereby avoiding roll-back effects during hill parking scenarios.
Implementation Method 1
a first spring element (6a) being provided, which acts on the sleeve (4) axially with a biasing force
Implementation Method 2
a second spring element (6b) being provided, which acts on the parking brake piston (3) axially with a further biasing force
Implementation Method 3
The second compressed air chamber (b) can be fed directly with compressed air from a service brake line (42)
Data Source
Figure 1
Figure 2
AI summary
The invention relates to a relay valve (1) for a vehicle, said valve comprising a parking brake piston (3) that is displaceable in a housing (2) and an axially displaceable cuff (4), a first compressed-air chamber (a) for receiving compressed air from a control line (31) being formed between the parking brake piston (3) and the housing (2). The valve is also provided with a first spring element (6a), which axially applies a pre-tensioning force to the cuff (4), and with a second spring element (6b), which axially applies another pre-tensioning force to the parking brake piston (3). According to the invention, an axially displaceable service brake piston (7) is arranged axially between the parking brake piston (3) and the cuff (4), the service brake piston resting at least radially against the parking brake piston (3) and radially against the housing (2) in a sealing manner, in order to form a second compressed-air chamber (b).