Trailer Brake Control Valve Layout for Power-Fail Brake Holding
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Solution Overview
Problem
Existing control devices for towing vehicle-trailer combinations lack sufficient security measures, as they can become unbraked due to power supply disruptions or control failures, particularly on slopes, when the 2/2-way solenoid valve switches from its energized blocking position to a de-energized open position, leading to safety hazards.
Innovation Solution
A control device with a direct connection from the bistable valve to the air volume-increasing valve, ensuring stable operation even in power failures, and an electrically controllable valve device that bridges the bistable valve, maintaining the desired ventilation states for both connections, including the parking and driving states, and a test state to verify the braking condition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a 2/2-way solenoid valve is used to control the spring-loaded brake during test functions, then the test function can be performed, but the system becomes vulnerable to power supply failures causing unintended unbraking
Solution Approach 1:
The patent inverts the control logic by using a bistable valve that maintains the brake in a held state by default, rather than requiring continuous energization to maintain the held state. The valve only changes state when specifically triggered, reversing the conventional approach where continuous power is needed to maintain control.
Solution Approach 2:
The patent introduces a bistable valve as an intermediary between the control system and the spring-loaded brake. This intermediary valve with its memory function decouples the direct dependency between power supply and brake holding, allowing the brake to remain held even when power is lost.
2Extent of automation
If electromagnetic valves are used for brake control, then automated control is achieved, but the system becomes dependent on power supply continuity
Solution Approach 1:
The bistable valve serves itself by maintaining its switching position through its inherent memory function without requiring external power or control signals. Once switched to a position, it remains there autonomously, eliminating the need for continuous power supply to maintain the control state.
Solution Approach 2:
The patent replaces the electromechanical solenoid valve with a purely mechanical bistable valve that uses mechanical memory (such as a cam mechanism or spring-loaded latch) to maintain its state, substituting electronic power-dependent control with a power-independent mechanical system.
3Loss of energy
If the solenoid valve is de-energized during power failure, then power consumption is reduced, but the brake holding function is lost
Solution Approach 1:
The bistable valve is switched to the desired position before power failure occurs, and this position is then maintained by the valve's memory function. The action of setting the brake holding state is performed in advance and persists without requiring continued energy input, even during power failures.
Solution Approach 2:
The patent prepares the system by establishing the brake holding state through the bistable valve before any power failure can occur. This preparatory action creates a cushion of reliability, ensuring that even when power is lost, the brake remains held due to the pre-established state in the memory valve.
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a control device for controlling at least the parking brake of a towing vehicle of a towing vehicle/trailer combination, said parking brake comprising at least one spring brake cylinder, and for controlling the service brake of a trailer of the towing vehicle/trailer combination, containing at least the following: a) a compressed air supply connection (1) which can be connected to a compressed air storage container, b) an air quantity boosting valve device (9), the inlet (9.2) of which can be connected to the compressed air supply connection (1), the outlet (9.3) of which can be connected to a working connection (28) with the at least one spring brake cylinder, and which has a pneumatic control inlet (9.1) for supplying a control pressure in order to control the pressure at the outlet (9.3) of the air quantity boosting valve device (9), c) an electrically actuatable bistable valve (5) with an inlet (5.1) which can be connected to the compressed air supply connection (1) and to an outlet (5.2) that can be connected to the control inlet (9.1) of the air quantity boosting valve device (9), the outlet (5.2) of the bistable valve being connectable either to the bistable valve inlet (5.1) or to a pressure sink (5.3), d) an electronic control unit (10) which is electrically connected to the bistable valve (5) and which controls the bistable valve (5), and e) at least two ventilatable or evacuatable connections (29.1, 29.2) for a trailer control valve device which controls the service brakes of the trailer, one connection (29.1) of the connections (29.1, 29.2) being ventilated and the other connection (29.2) of the connections (29.1, 29.2) being evacuated when the vehicle is parked and one connection (29.1) and the other connection (29.2) being ventilated when the vehicle is traveling, wherein f) the inlet (5.1) of the bistable valve (5) is connected to a connection (29.1). According to the invention, g) the outlet (5.2) of the bistable valve (5) is directly and constantly connected to the control inlet (9.1) of the air quantity boosting valve device (9), and h) a valve device (7; 7') is provided which can be at least partly electrically controlled by the control unit (10) and which is designed to connect the other connection (29.2) to the inlet (5.1) or to the outlet (5.2) of the bistable valve (5) or to a pressure sink (7.12').