Commercial Vehicle Parking Brake Valve Control Logic
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Solution Overview
Problem
Pneumatic parking brake systems in commercial vehicles can inadvertently release when the driver is absent, leading to unsafe situations due to pressure buildup, and existing safety measures can cause delays and confusion for drivers when releasing the brake.
Innovation Solution
A parking brake system with a pneumatically controlled handbrake valve, a relay valve, an electronic control unit, and a 2/2-way solenoid valve that prevents ventilation of spring-loaded cylinders unless the driver is present and the auxiliary brake pressure is reached, ensuring the parking brake remains engaged when unoccupied.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the handbrake valve is actuated to ventilate the relay valve control input, then the parking brake is released, but the parking brake may inadvertently release when the driver is absent due to pressure buildup
Solution Approach 1:
A new valve device is introduced as an intermediary between the handbrake valve and the relay valve control input. This valve device receives the control signal from the handbrake valve and conditionally transfers it to the relay valve based on driver presence detection, thereby mediating the connection and preventing unintended brake release while maintaining intentional release capability
Solution Approach 2:
The system incorporates feedback through driver presence detection (via seat sensor, seat belt sensor, or pedal actuation sensor) that continuously monitors whether the driver is in the cab. This feedback information is used by the electronic control unit to dynamically control the valve device, enabling or disabling the brake release function based on real-time driver presence status
2Reliability
If the overflow valve is blocked to prevent parking brake release when driver is absent, then safety is improved, but the trailer brake system filling is delayed causing driver confusion
Solution Approach 1:
The brake control system is segmented into separate control paths: the new valve device controls only the parking brake system independently, while the overflow valve continues to supply compressed air to the trailer brake system without restriction. This segmentation allows the parking brake safety function to operate independently without interfering with trailer brake filling operations
Solution Approach 2:
The safety control function for preventing unintended parking brake release is extracted from the overflow valve and implemented through a separate valve device controlled by driver presence detection. This extraction allows the overflow valve to maintain its primary function of supplying compressed air to the trailer brake system without the side effect of delaying filling 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
This solution reliably prevents unintended release of the parking brake when the driver is absent and allows for controlled release only when safe conditions are met, enhancing safety and reducing driver confusion by preventing pressure-related issues.
Implementation Method 1
a relay valve which has a control input that can be controlled pneumatically by the hand brake valve
Implementation Method 2
spring-loaded cylinders, which are preferably assigned to the rear axle of the commercial vehicle
Data Source
Figure 1
AI summary
The invention relates to a parking brake system for a commercial vehicle, comprising a handbrake valve, a relay valve having a control input pneumatically actuated by the handbrake valve, a working input connected to a compressed air supply of the commercial vehicle, and a working output connected to at least one spring brake cylinder, an electronic control unit, and a valve device arranged between the handbrake valve and the control input of the relay valve, which can be electrically switched by the electronic control unit, wherein an indicator that can be electrically evaluated by the electronic control unit is available when a person is present to drive the commercial vehicle, and wherein the electronic control unit is suitable to prevent the at least one spring brake cylinder from being vented by means of the electrically switchable valve device when the indicator is not present.