Valve Timing Control via Differential Thermal Expansion
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Solution Overview
Problem
The existing valve opening and closing timing control apparatus experiences phase holding instability due to fluid leakage from advanced and retarded angle chambers, especially at increased temperatures, leading to fluctuations in relative rotational phase caused by centrifugal forces and cam fluctuation torque.
Innovation Solution
The apparatus incorporates a drive-side and driven-side rotational member with defined advanced and retarded angle chambers, a mounting member with tubular walls, and communication passages with different thermal expansion coefficients to manage fluid supply and leakage, ensuring stable phase control by adjusting fluid flow based on temperature-induced clearances and passage resistances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the spool is disposed at a neutral position to maintain intermediate phase, then the valve opening and closing timing control apparatus can hold an intermediate position, but fluid leakage from advanced angle chamber and retarded angle chamber deteriorates phase holding stability due to centrifugal force and cam fluctuation torque
Solution Approach 1:
The patent converts the harmful effect of fluid leakage into a beneficial feature by designing communication passages that allow leaked fluid to be reused. The leaked fluid from advanced angle chamber and retarded angle chamber is channeled back through the communication passages to maintain fluid pressure and compensate for losses, thereby maintaining phase holding stability even at high temperatures where leakage increases.
2Device complexity
If the spool is housed at the inner portion of the connection bolt, then the number of components is reduced and the apparatus is downsized, but fluid leakage cannot be effectively controlled
Solution Approach 1:
The connection bolt is designed with multi-functionality: it serves both as a mounting structure to hold the spool and as a fluid conduit through its internal hollow portion. The communication passages are formed within the connection bolt structure itself, allowing it to perform both mechanical support and fluid control functions simultaneously, thereby maintaining reliability without increasing component count.
3Ease of operation
If communication passages are provided to supply fluid to advanced angle chamber and retarded angle chamber, then phase control is enabled, but fluid leakage increases with temperature causing centrifugal force effects
Solution Approach 1:
The communication passages act as intermediary channels that connect the fluid supply system to both the advanced angle chamber and retarded angle chamber. These passages enable controlled fluid distribution for phase adjustment while also providing a return path for leaked fluid, mediating between the conflicting requirements of phase control capability and leakage prevention.
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 configuration maintains relative rotational phase stability by compensating for increased fluid leakage at higher temperatures, preventing phase fluctuations and ensuring accurate timing control despite cam fluctuation torque.
Implementation Method 1
Fluid controlled by the operation of the spool valve is supplied to or discharged from an advanced angle chamber and a retarded angle chamber
Implementation Method 2
A thermal expansion coefficient of a material forming the driven-side rotational member is greater than a thermal expansion coefficient of a material forming the mounting member
Data Source
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AI summary
To construct a valve opening and closing timing control apparatus which may restrain a fluctuation of a relative rotational phase by a supply of fluid to an advanced angle chamber and a retarded angle chamber even in a case where a leakage amount of fluid from the advanced angle chamber and the retarded angle chamber increases with an increase of a temperature. A driven-side rotational member is connected to a camshaft by a mounting member and a spool is movably provided at an inner portion of a tubular wall portion of the mounting member. A first flow passage connecting a first port of the tubular wall portion and the advanced angle chamber to each other and a second flow passage connecting a second port of the tubular wall portion and the retarded angle chamber to each other are provided at the driven-side rotational member. A thermal expansion coefficient of a material forming the driven-side rotational member is greater than a thermal expansion coefficient of a material forming the mounting member.