Variable Valve Cam Switching Timing to Prevent Noise and Wear
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Solution Overview
Problem
Variable valve devices experience abnormal noise and reduced durability due to malfunctions in the switching operation of the cam, particularly when the switching operation occurs during valve lift.
Innovation Solution
The oil supply to the switching mechanism is controlled by an oil control valve, starting at the end timing of the valve lift or in a zero range where no lift occurs, ensuring the switching operation is not hindered by the valve lift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the switching operation of the cam is performed regardless of the camshaft phase, then the valve lift amount can be changed, but abnormal noise may be generated due to malfunction of the switching operation during valve lift
Solution Approach 1:
The oil supply timing is advanced to start before the valve lift begins, preparing the switching mechanism in advance. The control unit determines the valve lift start timing based on camshaft rotation angle and throttle opening, then supplies oil to the switching mechanism before this timing, ensuring the switching operation is ready and avoids malfunction during the actual valve lift.
Solution Approach 2:
The control unit uses feedback from sensors detecting camshaft rotation angle and throttle opening to dynamically adjust the oil supply timing. This feedback mechanism allows the system to adapt the switching operation timing to actual operating conditions, preventing abnormal noise while maintaining valve lift change capability.
2Productivity
If the switching operation is performed during valve lift, then the valve lift amount can be adjusted, but the durability of the variable valve device is reduced due to abnormal noise and malfunction
Solution Approach 1:
The system performs the switching operation in advance before the valve lift starts by controlling oil supply timing. The control unit calculates the valve lift start timing from camshaft rotation angle and throttle opening, then initiates oil supply to the switching mechanism before this timing, completing the cam switching action before the valve begins to lift, thus avoiding stress and noise during switching.
Solution Approach 2:
The patent replaces mechanical timing-based switching with a controlled oil supply system that uses sensor feedback and electronic control to determine optimal switching timing. This substitution allows precise control of the switching operation to occur at the optimal moment (before valve lift), improving durability while maintaining adjustment capability.
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 suppresses abnormal noise and improves the durability of the variable valve device by preventing malfunctions during the switching operation.
Implementation Method 1
an oil pressure for the switching mechanism is controlled by an oil control valve, and oil starts to be supplied from the oil control valve to the switching mechanism at an end timing of a valve lift or in a zero range
Data Source
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Figure 3A~3B
AI summary
There is provided a variable valve device provided in a cylinder head and capable of changing a valve lift amount, including: a camshaft on which a plurality of cams with different valve lift amounts are formed; a switching mechanism configured to switch a cam for moving a valve among the plurality of cams; and an oil control valve configured to control an oil pressure for the switching mechanism. Oil starts to be supplied from the oil control valve to the switching mechanism at an end timing of a valve lift or in a zero range in which no valve lift occurs.