Variable Valve Timing Actuator Noise Reduction
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Solution Overview
Problem
Existing variable valve timing systems generate noticeable operation sounds during engine stop, which can be perceived as unusual noise by passengers, and there is a lack of effective methods to minimize these sounds.
Innovation Solution
A variable valve timing apparatus and control method that reduces the actuator operation amount and sets an upper limit value of the operation amount smaller during engine stop, using an electric motor as the actuator, to minimize noise by adjusting the rotational speed difference between the electric motor and the camshaft, and includes a forced stopping mechanism to prevent prolonged operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the actuator operates at normal speed to change valve timing during engine stop, then the valve timing can be adjusted effectively, but the operation sound becomes noticeable and perceivable as noise by passengers
Solution Approach 1:
The patent applies parameter changes by reducing the actuator operation amount (rotational speed difference between actuator and camshaft) during engine stop conditions. The control unit modifies the operation parameters based on the engine state, specifically limiting the actuator operation amount to a predetermined value or a fraction of the normal operation amount when the engine is stopped, thereby reducing noise while maintaining necessary valve timing adjustment capability
2Object-affected harmful factors
If the actuator operation amount is reduced during engine stop, then the operation sound is minimized, but the valve timing adjustment speed is reduced
Solution Approach 1:
The patent implements dynamics by making the actuator operation amount adjustable based on operating conditions. The control unit dynamically determines the appropriate operation amount by detecting engine state (operating vs. stopped) and adjusts the operation parameters accordingly. This allows the system to optimize between noise reduction and adjustment speed based on real-time conditions
3Ease of operation
If the actuator operates continuously during engine stop, then the valve timing can be adjusted fully, but power consumption increases and overheating may occur
Solution Approach 1:
The patent applies partial action by limiting the actuator operation amount to a predetermined value or a fraction of the normal operation amount during engine stop. Instead of allowing full operation, the control unit restricts the operation to only the extent necessary for valve timing adjustment while preventing excessive operation that would cause overheating or unnecessary power consumption. The forced stopping mechanism ensures operation ceases when the target timing is reached
Data Source
AI summary
In a variable valve timing apparatus in which a phase of an intake valve is changed at an amount of change according to a rotational speed of relative rotation between an electric motor as an actuator and a camshaft, the set upper limit value of the rotational speed of relative rotation and a coefficient Nθ of conversion from a required phase-change amount to the rotational speed of relative rotation ΔNm in each control period are set at smaller values at the time of engine stop than at the time of engine operation. As a result, the rotational speed of the electric motor in the VVT operation at the time of engine stop is reduced thereby reducing the operation sound of the variable valve timing apparatus.