SCR Pressure Sensor Adjustment Using Ambient Reference
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Solution Overview
Problem
The existing methods for adjusting pressure sensors in SCR systems during the switch-off phase are inadequate, particularly at low temperatures where the reduction agent solution freezes, leading to potential damage and unreliable pressure readings due to the buildup of pressure in the system.
Innovation Solution
The method involves switching off the delivery pump during the switch-off phase, allowing the pressure in the SCR system to equalize with ambient pressure, which is used as a new reference for the pressure sensor, enabling reliable adjustment and detection of pressure deviations, and utilizing a 4/2-way valve to adjust the transport direction and ventilate the system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the delivery pump operates during the switch-off phase to return reduction agent solution, then the system pressure builds up, but the pressure sensor cannot be reliably adjusted because the pressure does not equalize with ambient pressure
Solution Approach 1:
The method switches off the delivery pump at the beginning of the switch-off phase before the pressure equalization process occurs. This preliminary action creates the necessary condition for pressure equalization, allowing the pressure sensor to be adjusted reliably against ambient pressure reference before any pressure build-up occurs during the return flow process.
2Measurement precision
If the pressure sensor is adjusted during operation when the delivery pump is running, then continuous monitoring is maintained, but the pressure readings are unreliable due to pressure build-up from the return flow
Solution Approach 1:
The pressure sensor adjustment is performed periodically during the switch-off phase when the delivery pump is switched off. This periodic interruption allows pressure equalization to occur, providing reliable reference conditions for adjustment, while the system resumes normal operation afterward, maintaining overall continuous monitoring capability.
3Temperature
If the system operates at low temperatures, then the reduction agent solution freezes, but the pressure build-up during switch-off phase exacerbates the freezing risk
Solution Approach 1:
The delivery pump is switched off at the beginning of the switch-off phase, before the pressure equalization and return flow process occurs. This preliminary action prevents pressure build-up that would otherwise exacerbate freezing risks at low temperatures, while still allowing the system to complete the necessary return flow and ventilation functions.
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 approach ensures reliable pressure sensor adjustment and protection against freezing damage by using ambient pressure as a reference, allowing for accurate pressure measurements and system ventilation, effectively addressing the issue of pressure sensor malfunctions and freezing risks.
Implementation Method 1
a pressure sensor (22) is disposed between a delivery pump (21) and a dosing valve (32) on the pressure side of the delivery pump (21) and can measure a pressure there
Implementation Method 2
The section of the SCR system monitored by the pressure sensor is connected to the surroundings, for example via a return line, so that pressure equalization with the ambient pressure can occur
Implementation Method 3
In this case, the delivery pump or the return pump builds up a reduced pressure in the pressure line. By opening the dosing valve, the pressure line is ventilated and the reduction agent solution is sucked into the reduction agent tank
Data Source
AI summary
A method for adjusting a pressure sensor of an SCR system between a delivery pump and a dosing valve, with which the delivery pump is switched off during a switch-off phase of the SCR system and a pressure (pm) measured by the pressure sensor is detected at least during a section of the switch-off phase in which the delivery pump is switched off, and the adjustment of the pressure sensor is carried out by using the measured pressure (pm) as the reference pressure for the pressure sensor.