Misfire Detection Threshold Adjustment for Dual Injection Engines

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Solution Overview

Problem

In vehicles with engines equipped with both cylinder and port injection valves, rotation fluctuations can lead to false misfire determinations when switching between injection modes, as the misfire determination threshold is not adequately adjusted, causing incorrect assessments of engine misfires.

Innovation Solution

Implementing an electronic control unit that dynamically adjusts the misfire determination threshold between cylinder and port injection modes, setting a higher threshold in the cylinder injection mode and a lower threshold in the port injection mode, and changing the threshold values based on elapsed time or rotation speed to prevent false misfire determinations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the misfire determination threshold is set to a first value in the cylinder injection mode and a second value smaller than the first value in the port injection mode, then the accuracy of misfire detection is improved, but false determination of misfire may occur during mode transition

Engineering Contradiction:

Improvemisfire detection accuracyVSAvoidfalse determination rate

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The misfire determination threshold is dynamically adjusted based on the injection mode. In the cylinder injection mode, a first threshold value is used, while in the port injection mode, a second smaller threshold value is used. This dynamic adaptation allows the system to maintain high detection accuracy for each mode's characteristic rotation fluctuations while preventing false determinations during mode transitions.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The threshold parameter is changed according to the injection mode being executed. The system switches between different threshold values (first value for cylinder injection, second value for port injection) based on the operational mode, thereby optimizing misfire detection accuracy for each mode's specific rotation fluctuation characteristics.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If the misfire determination threshold is immediately changed when switching injection modes, then the detection accuracy is improved, but false misfire determination occurs due to continued large rotation fluctuation

Engineering Contradiction:

Improvemisfire detection accuracyVSAvoidfalse misfire determination

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The system prepares for mode transition by continuing to use the appropriate threshold value for the current mode during the transition period. When switching from cylinder to port injection mode, the first threshold value is maintained until the mode transition is complete, preventing false misfire determinations that would occur if the threshold were immediately changed while rotation fluctuation remains large.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system cushions against false determination by maintaining the original threshold value during the transition period. This beforehand cushioning prevents the harmful effect of false misfire detection that would occur if the threshold were immediately changed while the engine rotation fluctuation is still adapting to the new injection mode.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Device complexity

If a single misfire determination threshold is used for both injection modes, then the system complexity is reduced, but the misfire detection accuracy decreases due to different rotation fluctuation characteristics

Engineering Contradiction:

Improvethreshold setting complexityVSAvoidmisfire detection accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

Different threshold values are applied to different injection modes based on their local characteristics. The cylinder injection mode uses a first threshold value suited for its larger rotation fluctuations, while the port injection mode uses a second smaller threshold value appropriate for its smaller fluctuations. This local optimization improves detection accuracy without requiring complex adaptive algorithms.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The misfire determination system is segmented into mode-specific threshold settings. Instead of using a single universal threshold, the system divides the threshold setting into distinct values for cylinder injection mode and port injection mode, thereby optimizing detection accuracy for each mode's specific rotation fluctuation characteristics.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS9951710B2Vehicle and control method for vehicle

Publication Date: 2018.04.24 TOYOTA JIDOSHA KK

AI summary

An electronic control unit sets a misfire determination threshold to a first value in the cylinder injection mode, and sets the misfire determination threshold to a second value smaller than the first value in the port injection mode, and determines that a misfire occurs in the engine when a rotation fluctuation of the engine is larger than the misfire determination threshold. In a case where the cylinder injection mode is changed to the port injection mode, when a predetermined period has elapsed from the change, the electronic control unit changes the misfire determination threshold from the first value to the second value.