Variable Valve Mechanism Control for Engine Torque Response
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Solution Overview
Problem
Existing engine control systems experience delays in valve timing control during sudden acceleration, leading to reduced engine torque due to reliance on mapping data that does not account for rapid changes in intake air, resulting in inappropriate valve timing adjustments based on engine operation states.
Innovation Solution
An engine control device with a variable valve mechanism that uses separate opening/closing period settings based on intake air amount and output shaft rotation speed, with an acceleration determination unit to switch between these settings, allowing for timely valve timing control adjustments during varying acceleration states without relying on intake air data when acceleration is high.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If valve timing control uses mapping data based on engine speed and intake air amount, then appropriate valve timing can be achieved under steady conditions, but responsiveness deteriorates during sudden acceleration due to delay in detecting intake air changes
Solution Approach 1:
The system dynamically switches between two control modes: using intake air amount during steady-state operation for accurate valve timing control, and using engine speed alone during acceleration states for rapid response. The acceleration state determination unit detects when the engine is accelerating and triggers a mode switch, allowing the control strategy to adapt to changing operating conditions and resolve the contradiction between precision and responsiveness
Solution Approach 2:
The control system changes the input parameters used for valve timing control based on the detected acceleration state. During acceleration, it switches from using intake air amount (which has detection delay) to using engine speed (which responds immediately). This parameter substitution allows the system to maintain appropriate control responsiveness while preserving the ability to achieve accurate valve timing when conditions permit
2Measurement precision
If valve timing control waits for intake air amount increase before adjusting timing, then control accuracy is maintained, but time delay occurs during sudden acceleration reducing engine torque
Solution Approach 1:
The acceleration state determination unit proactively detects acceleration conditions before the intake air amount fully reflects the change. When acceleration is detected, the system preemptively switches to the engine-speed-based control mode, allowing valve timing adjustment to begin immediately rather than waiting for intake air sensor data to update. This preliminary detection and action prevents the time loss that would otherwise occur
Solution Approach 2:
The acceleration state determination unit acts as an intermediary that bridges the gap between the slow-to-response intake air amount sensor and the fast-responding engine speed sensor. By detecting acceleration state independently, it triggers the switch to using engine speed as the control parameter, effectively mediating between the conflicting requirements of measurement precision and response speed
Data Source
AI summary
When an acceleration flag is not set, an amount of target rotation tvttbb1 of a variable valve mechanism is set on the basis of an amount of intake air and an engine speed. On the other hand, when the acceleration flag is set, an amount of target rotation of the variable valve mechanism is set on the basis of the engine speed, a cooling water temperature, and an atmospheric pressure. As described above, when the acceleration flag is not set, i.e., when the amount of intake air does not change excessively, the amount of target rotation based on the amount of intake air is used, so that the valve timing can be controlled appropriately.