Variable Valve Timing Equalizing Passage for Pressure Pulsation
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Solution Overview
Problem
Conventional variable valve timing (VVT) systems face issues with the response speed of the stopper member due to increased pressure loss when engaging the oil-filled engaging hole, and are susceptible to fluid pressure pulsations, which can lead to unexpected locking or unlocking of the housing and vane rotor, compromising the variable angular range and stability.
Innovation Solution
A variable valve timing apparatus with a restricting member, such as a hollow cylindrical stopper piston, that features an equalizing passage to communicate the engaging hole and holding hole, allowing fluid flow and canceling out oil pressure pulsations on both ends, ensuring stable engagement and operation without the need for a relief passage, thus maintaining a wide variable angular range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the engaging hole is filled with oil, then the stopper member can be engaged with the engaging hole to lock the housing and vane rotor, but the response speed of the stopper member is lowered due to increased pressure loss when squeezing oil back into the oil passage
Solution Approach 1:
The oil passage is divided into a main passage and a bypass passage. The bypass passage provides an alternative route for oil to escape when the stopper member engages with the engaging hole, reducing the pressure loss and improving response speed while maintaining reliable locking through the main passage.
Solution Approach 2:
The bypass passage acts as an intermediary channel that mediates the oil flow during the engagement process. It allows oil to be discharged from the engaging hole without requiring the stopper member to squeeze oil back through the main passage, thereby reducing resistance and improving response speed.
2Speed
If a relief passage is provided to discharge oil from the engaging hole, then the response speed of the stopper member is improved, but a shut down valve is required to control oil leakage, which increases device complexity
Solution Approach 1:
The bypass passage is integrated directly into the housing structure as a permanent feature, combining the relief function with the existing structural elements. This eliminates the need for separate shut down valves and complex actuation mechanisms, reducing device complexity while maintaining improved response speed.
3Loss of substance
If the vane rotor is widened in circumferential direction to seal the engaging hole, then oil leakage is controlled, but the variable angular range of the VVT is reduced
Solution Approach 1:
The sealing function is segmented between the main passage and bypass passage. The main passage provides the primary sealing path, while the bypass passage provides a controlled leakage path. This segmentation allows the vane rotor to maintain a narrower circumferential width, preserving variable angular range while controlling oil leakage through the coordinated action of both passages.
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 design enhances the response speed and stability of the stopper member, preventing unexpected movements and ensuring accurate control of the phase angle between the crankshaft and camshaft, while maintaining a wide variable angular range and reducing oil leakage.
Implementation Method 1
the restricting member being formed in a hollow cylindrical shape which defines an equalizing passage capable of communicating the engaging hole and the holding hole to flow the fluid
Implementation Method 2
the restricting member being formed in a hollow cylindrical shape which defines an equalizing passage capable of communicating the engaging hole and the holding hole to flow the fluid when the restricting member enters into the engaging hole
Data Source
AI summary
A variable valve timing apparatus includes a stopper piston which has an equalizing passage in an axial direction. Even if the engaging hole is filled with the oil, the equalizing passage enables the oil flows from an engaging hole to a holding hole when the stopper piston enters into the engaging hole. It is possible to form a vane as narrow as possible, and to enlarge a variable angular range. In addition, the stopper piston has both end faces which are substantially identical in surface area. Even if pulsation arises in oil pressure, pressures acting on both end faces of the stopper piston can be substantially cancelled and position of the stopper piston can be stabilized.