Engine Knock Control via Airflow Limiting and Transmission Compensation
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Solution Overview
Problem
Vehicle engine knock control methods that retard spark timing to mitigate knock can lead to unstable combustion and reduced engine output torque, especially at high IMEP and low engine speeds, causing performance degradation and vehicle jerking.
Innovation Solution
Limiting airflow to the engine when spark timing is retarded beyond a threshold, and compensating for the torque reduction by adjusting transmission operating parameters, such as gear ratio and torque converter lock-up, to maintain vehicle performance and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If spark timing is retarded to mitigate knock, then knock is reduced, but engine output torque is reduced and combustion stability deteriorates
Solution Approach 1:
The system dynamically adjusts multiple parameters including spark timing, intake air amount, and transmission operating parameters based on real-time engine conditions. When knock is detected, spark timing is retarded and intake air is limited to suppress knock while maintaining combustion stability through coordinated parameter changes.
Solution Approach 2:
The control system continuously monitors engine knock and combustion stability, using this feedback to dynamically adjust spark timing and intake air amount. The system ramps in and ramps out automatic control based on detected conditions, creating a closed-loop control system that adapts to changing engine states.
2Reliability
If intake air is limited to control combustion instability, then combustion stability is improved, but engine output torque is reduced causing vehicle performance degradation
Solution Approach 1:
The transmission system acts as an intermediary to compensate for torque loss. When intake air is limited to maintain combustion stability, the transmission adjusts its operating parameters (gear ratio, torque converter lock-up) to multiply or direct torque, thereby compensating for the reduced engine output torque and maintaining vehicle performance.
Solution Approach 2:
The system coordinates changes in both engine parameters (intake air amount) and transmission parameters (gear ratio, torque converter operation) to achieve the dual goal of maintaining combustion stability while compensating for torque loss. The transmission parameters are adjusted in response to engine conditions to offset torque reduction.
3Speed
If automatic control of intake air is suddenly transitioned, then knock control response is improved, but vehicle jerking and performance issues occur
Solution Approach 1:
The system uses dynamic, gradual transitions (ramping) for both increasing and decreasing automatic control of intake air, rather than sudden step changes. This dynamic approach smooths the transition process, preventing vehicle jerking while maintaining effective knock control response. The ramping rate can be adjusted based on engine conditions.
Data Source
AI summary
Various systems and methods are described for controlling combustion stability in an engine driving a transmission. One example method comprises limiting airflow to the engine in response to a spark timing retarded beyond a spark retard threshold, the limiting airflow to the engine reducing engine torque output and compensating for the reduction in engine torque output by adjusting a transmission operating parameter.