Engine Control Ignition Timing Retard for Torque Shock Reduction
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Solution Overview
Problem
Existing engine control methods during fuel cutoff after a malfunction diagnosis of the exhaust gas recirculation system lead to unstable combustion and torque shock due to the introduction of combustion gas into the intake air, causing rapid engine torque changes and vibrations.
Innovation Solution
An engine control device that adjusts the ignition timing retard control by setting a more advanced initial ignition timing and reducing the retard amount when the elapsed period from the malfunction diagnosis to fuel cutoff is short, and maintains this timing for a shorter period, thereby reducing torque shock and alleviating vehicle body vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the engine returns from fuel cutoff immediately after malfunction diagnosis of the EGR system, then the amount of new air flowing into the cylinder increases, but combustion becomes unstable and torque shock occurs
Solution Approach 1:
The control device performs preliminary action by retarding ignition timing before the engine returns from fuel cutoff. The ECU detects the transition from fuel cutoff state and applies ignition timing retard control during the initial explosions after return, preventing unstable combustion and torque shock before they occur. This is evident in the flowchart where the ECU determines fuel cutoff termination and applies retard control in steps S3-S5.
Solution Approach 2:
The control device changes the ignition timing parameter dynamically based on engine operating conditions. When the engine returns from fuel cutoff, the ECU retards ignition timing by a predetermined amount (e.g., 5-15 degrees CA) during initial explosions, then gradually returns to base ignition timing. This parameter change stabilizes combustion despite the sudden increase in new air flow.
2Object-affected harmful factors
If ignition timing is retarded at the initial explosion after return from fuel cutoff, then torque shock is reduced, but engine torque rise is suppressed excessively when new air flow is already increased
Solution Approach 1:
The control device applies partial action by retarding ignition timing only during the initial explosions after fuel cutoff return, rather than continuously. The retard control is applied for a limited number of explosions (e.g., first 1-3 explosions) until combustion stabilizes, then the ECU returns to base ignition timing. This partial application reduces torque shock without excessively suppressing engine torque when combustion recovers.
Solution Approach 2:
The control device dynamically adjusts ignition timing based on real-time detection of combustion stability and engine operating conditions. The ECU monitors crankshaft acceleration and other parameters to determine when retard control should be applied and when to return to base timing. This dynamic control optimizes the balance between torque shock reduction and power delivery.
3Reliability
If the EGR valve is forcedly opened and closed during fuel cutoff for malfunction diagnosis, then the EGR system functionality is detected, but combustion gas is introduced into intake air causing unstable combustion
Solution Approach 1:
The control device extracts the malfunction diagnosis function from normal engine operation by performing it specifically during fuel cutoff periods. The ECU forces the EGR valve to open and close only when fuel is cut off, separating the diagnosis function from combustion phases. This allows EGR system testing without introducing combustion gas into the intake air during active combustion.
Solution Approach 2:
The control device performs preliminary action by completing the EGR malfunction diagnosis during fuel cutoff before normal combustion resumes. The ECU detects EGR valve functionality by monitoring intake air flow changes during forced valve operations while fuel is cut off, ensuring the diagnosis is completed before combustion gas could contaminate the intake air and cause unstable combustion.
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 effectively suppresses torque shock and reduces vehicle body vibrations by ensuring the engine torque rises before torsional strain release, maintaining stable combustion, and preventing abrupt torque changes.
Implementation Method 1
combustion is resumed in a condition where air containing combustion gas is introduced into the cylinder
Data Source
AI summary
A control device for an engine including an EGR system, the control device includes an electronic control unit. The electronic control unit is configured to forcedly open and close an EGR valve and make a malfunction diagnosis of the EGR system, during fuel cutoff, perform ignition timing retard control when the engine returns from the fuel cutoff, and set the ignition timing at a start point of the ignition timing retard control to a more advanced value when an elapsed period from the malfunction diagnosis of the EGR system to a return from the fuel cutoff is short, as compared with the case where the elapsed period is long, so as to reduce a retard amount of the ignition timing at the start point of the ignition timing retard control, relative to the ignition timing immediately before the start of the ignition timing retard control.