Torque Converter Clutch Control for Post-Oxygen Sensor Diagnostics
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Solution Overview
Problem
Traditional diagnostic systems for post-oxygen sensors in vehicles often require intrusive checks, which can increase exhaust emissions and cause engine instability, and may not complete the post oxygen performance diagnostic (POPD) test due to rapid engine speed decrease during deceleration fuel cutoff (DFCO) conditions.
Innovation Solution
A post oxygen performance diagnostic (POPD) system that includes a deceleration fuel cutoff (DFCO) portion, utilizing a torque converter control module to maintain engine speed by controlling the torque converter clutch (TCC) in a locked or controlled slip state during DFCO, ensuring the POPD test can be completed without engine speed reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If deceleration fuel cutoff (DFCO) is implemented during POPD testing, then exhaust emissions are reduced, but engine speed decreases rapidly causing the diagnostic test to fail
Solution Approach 1:
The torque converter clutch is engaged before and during the DFCO portion of the POPD test to prevent rapid engine speed decay. This preliminary action counteracts the natural deceleration effect, allowing the diagnostic test to complete successfully while maintaining low emissions.
Solution Approach 2:
The torque converter clutch acts as an intermediary mechanical element between the engine and transmission. By controlling TCC engagement, the system mediates between the need for fuel cutoff (emissions reduction) and the need to maintain engine speed for diagnostic testing.
2Measurement precision
If intrusive checks are used to diagnose oxygen sensors, then diagnostic accuracy is improved, but engine stability deteriorates and exhaust emissions increase
Solution Approach 1:
Instead of using aggressive intrusive checks that fully manipulate A/F ratio, the system uses partial action by leveraging the natural DFCO condition combined with TCC control. This provides sufficient diagnostic information without causing severe engine instability or emission spikes.
Solution Approach 2:
The system changes the operating parameters by maintaining engine speed through TCC control during the diagnostic test. This parameter modification allows the oxygen sensor diagnostic to proceed without the traditional intrusive A/F ratio manipulations that cause engine instability.
3Use of energy by moving object
If engine speed is allowed to decrease during DFCO, then fuel economy is improved, but the POPD test cannot be completed
Solution Approach 1:
The torque converter clutch is controlled in a periodic manner - engaged during the DFCO portion of the POPD test to maintain engine speed, and disengaged at other times to allow normal deceleration and fuel cutoff benefits. This periodic control allows both fuel economy and test completion.
Solution Approach 2:
The system performs preliminary engagement of the torque converter clutch before initiating the DFCO portion of the POPD test. This ensures engine speed is maintained throughout the diagnostic window, allowing the test to complete while still benefiting from fuel cutoff during non-test periods.
Data Source
AI summary
A system comprises a post oxygen performance diagnostic (POPD) module that performs a POPD of a post oxygen sensor, wherein the POPD includes a deceleration fuel cutoff (DFCO) portion. A torque converter control module adjusts operation of a torque converter clutch (TCC). The POPD module and the torque converter control module operate the TCC to control engine speed above a predetermined engine speed during the DFCO portion of the POPD. A method comprises performing a POPD of a post oxygen sensor, wherein the POPD includes a deceleration fuel cutoff (DFCO) portion and adjusting operation of a torque converter clutch (TCC) to control engine speed above a predetermined engine speed during the DFCO portion of the POPD.