Pressure Switch Function Testing in Vehicle Tank Ventilation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for testing the function of pressure switches in tank ventilation systems of motor vehicles are unreliable, leading to incorrect diagnoses and failure to identify leaks, especially when the pressure switch is stuck in the closed state.
Innovation Solution
A method that detects the switched state of the pressure switch and increases the pressure in the tank ventilation system above a predefined limit, identifying a defect if the pressure switch remains in the low-pressure position after the measure is taken, using a tank ventilation valve to pneumatically connect or separate the system from the intake pipe based on engine operation, acceleration, and temperature conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the existing method monitors coolant temperature reduction and pressure switch closure after vehicle shutdown, then a leak can be detected when pressure switch is closed, but incorrect diagnoses occur when pressure switch is defective (stuck closed) and leaks remain undetected
Solution Approach 1:
The system applies preliminary anti-action by actively counteracting the stuck-closed state of the pressure switch. When the pressure switch remains closed despite pressure equalization (indicating a defect), the system actuates the tank ventilation valve to force open the pressure equalization path, thereby overcoming the defective switch's stuck state and enabling accurate leak detection
Solution Approach 2:
The tank ventilation valve serves as an intermediary component that mediates between the control unit and the pressure equalization path. By actuating this valve, the system creates a forced pressure equalization that bypasses the defective pressure switch, allowing the system to distinguish between a truly closed switch and a stuck-closed defective switch
2Measurement precision
If the pressure switch is stuck in closed state, then the system cannot identify leaks in tank ventilation system, but adding complex testing equipment increases system complexity and cost
Solution Approach 1:
The system applies self-service by using its existing components (tank ventilation valve, control unit, and pressure switch) to perform the defect detection function. The control unit utilizes information from the pressure switch state and coolant temperature monitoring that already exists in the system, combined with actuation of the existing tank ventilation valve, to detect pressure switch defects without requiring additional specialized testing equipment
3Reliability
If frequent testing is performed to improve reliability, then more testing cycles are needed, but this increases testing time and system operation duration
Solution Approach 1:
The system implements periodic action by performing pressure switch function tests at predetermined intervals or under specific operating conditions (such as after vehicle shutdown when coolant temperature drops). This periodic testing approach ensures reliable defect detection while minimizing the total testing time by concentrating tests at optimal moments rather than continuously monitoring
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 method provides reliable testing of the pressure switch function, preventing incorrect diagnoses and ensuring accurate identification of defects, allowing for frequent and accurate testing both when the engine is running and at standstill, without the need for additional pressure pumps, thus improving the overall reliability of the tank ventilation system testing.
Implementation Method 1
a tank ventilation valve of the tank ventilation system, which valve is arranged in a connecting line between a fuel vapor accumulator and an intake pipe of the internal combustion engine, is actuated such that the tank ventilation system is pneumatically connected to the intake pipe
Data Source
AI summary
The switched state of a pressure switch in a tank ventilation system of a motor vehicle is used for testing the function of the tank ventilation system, the pressure switch being in a low-pressure position if the pressure in the tank ventilation system is lower than a predefined pressure limit while being in a high-pressure position if that is not the case. A defective pressure switch can result in wrong assessments. Disclosed is a method for testing the function of the pressure switch, the method encompassing the following steps: a switched state of the pressure switch is detected; a measure is carried out that increases the pressure in the tank ventilation system above the pressure limit if the pressure switch is in the low-pressure position; a defect of the pressure switch is identified if the pressure switch remains in the low-pressure position after carrying out the measure.