Reducing Agent Diagnosis Pump Capacity Correction
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Solution Overview
Problem
The existing reducing agent adding device for internal combustion engines faces diagnostic accuracy issues due to variations in pump discharge capacity, leading to incorrect determination of device abnormalities, as the pressure decrease amount in the reducing agent passage is influenced by both pump efficiency and degradation over time.
Innovation Solution
An abnormality diagnosis device that adjusts the diagnostic parameter or threshold value based on the pump discharge capacity, using a pump control unit to maintain a predetermined pressure and an addition valve control unit to switch the valve state, with a diagnostic parameter obtaining unit and correction unit to rectify variations in diagnostic accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pressure decrease amount in the reducing agent passage is used as a diagnostic parameter, then the abnormality diagnosis can be performed, but the diagnostic accuracy decreases when pump discharge capacity varies
Solution Approach 1:
The patent changes the diagnostic parameter from absolute pressure decrease amount to pressure decrease amount per unit discharge amount. This parameter transformation normalizes the diagnostic metric, making it independent of pump discharge capacity variations. By dividing the pressure decrease amount by the discharge amount of reducing agent, the diagnostic parameter becomes comparable across different pump conditions, thereby resolving the contradiction between diagnostic accuracy and adaptability to pump variations.
2Ease of operation
If a fixed threshold value is used for abnormality determination, then the diagnosis process is simple, but incorrect diagnoses occur due to pump efficiency variations
Solution Approach 1:
The patent transforms the diagnostic parameter to pressure decrease amount per unit discharge amount, which inherently adjusts the threshold comparison basis. This parameter change maintains the simplicity of threshold-based diagnosis while improving reliability, because the normalized parameter accounts for pump efficiency variations. The threshold remains a fixed value for ease of operation, but the parameter transformation ensures it reliably indicates actual abnormalities rather than pump performance variations.
3Device complexity
If the pump discharge capacity is not considered in the diagnosis, then the diagnostic process is straightforward, but the diagnostic accuracy decreases due to initial tolerance and aging effects
Solution Approach 1:
The patent applies a parameter transformation that normalizes the pressure decrease amount by the discharge amount, effectively compensating for pump discharge capacity variations due to initial tolerance and aging. This approach increases diagnostic accuracy without significantly increasing device complexity, as it involves a computational adjustment rather than additional hardware. The normalized parameter enables accurate diagnosis across the pump's operational lifecycle.
Data Source
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AI summary
In an abnormality diagnosis device for a reducing agent adding device, a decrease in diagnostic accuracy under the influence of a pump discharge capacity is suppressed. In the abnormality diagnosis device which carries out an abnormality diagnosis of the reducing agent adding device by obtaining a diagnostic parameter which is a parameter correlated with an amount of pressure drop in a reducing agent passage (6) in the case where, from a state in which an addition valve (3) has been closed and in which a voltage to be applied to a pump (5) is controlled to a diagnostic voltage so that the pressure in the reducing agent passage (6) becomes a predetermined pressure, the addition valve (3) is made to open in a state where the voltage to be applied to the pump (5) is maintained at the diagnostic voltage, and by making a comparison between the diagnostic parameter and a predetermined threshold value, provision is made for a pump discharge capacity obtaining unit (8) configured to obtain the pump discharge capacity of the pump (5), and a correction unit (8) configured to correct the diagnostic parameter or the predetermined threshold value based on the pump discharge capacity of the pump (5), wherein the abnormality diagnosis is carried out by using the diagnostic parameter or the predetermined threshold value thus corrected.