Variable Valve Timing Spool Reduces Lock Shifting Resistance
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Solution Overview
Problem
Existing variable valve timing control devices face challenges in quickly shifting to the lock state due to high flow path resistance and fluid viscosity, especially at low temperatures, which hinders responsiveness and limits downsizing of the device.
Innovation Solution
The design includes a valve unit with a spool and connecting bolt featuring through holes for fluid ports, allowing the second pump port and lock port to communicate only at the unlock position and draining fluid to the lock port at the lock position, reducing pressure influence and enhancing responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the flow path resistance of the lock discharge flow path is high, then the device structure is simplified, but the lock mechanism cannot quickly shift to the lock state especially at low temperature
Solution Approach 1:
The lock discharge flow path is segmented into multiple sections: the lock discharge port, the discharge flow path inside the spool, and the communication flow path. By segmenting the flow path and providing multiple discharge routes, the system reduces flow path resistance while maintaining structural simplicity, enabling quick lock state shifting even at low temperatures.
Solution Approach 2:
The spool acts as an intermediary component that controls fluid flow between the lock discharge port and the discharge flow path. The spool's position determines whether the lock discharge port communicates with the discharge flow path, allowing rapid discharge of fluid from the recessed portion to achieve quick lock state shifting.
2Productivity
If the spool size is increased to accommodate more ports and control amount, then the fluid control capability is improved, but the device cannot be downsized in the direction along the rotary axis
Solution Approach 1:
The ports (advanced-angle port, retarded-angle port, lock port, first pump port, second pump port) are arranged in the circumferential direction rather than extending the spool length along the rotary axis. This dimensional change allows the spool to control multiple fluid paths without increasing the device length, enabling downsizing while maintaining fluid control capability.
Solution Approach 2:
The spool serves multiple functions: it controls the advanced-angle chamber, the retarded-angle chamber, and the lock mechanism through its land portions. By making the spool multi-functional, the design reduces the need for separate control components, allowing downsizing of the device while maintaining comprehensive fluid control capability.
3Adaptability or versatility
If the lock member and lock recessed portion are always relatively displaced, then the intermediate lock state is achieved, but the shift to lock state is difficult compared to contact states
Solution Approach 1:
The system preliminarily positions the lock member and lock recessed portion in an intermediate lock state where they are relatively displaced. From this preliminary position, the lock mechanism can quickly shift to the final lock state when the lock member and lock recessed portion reach the engageable position, as the fluid discharge path is already prepared and optimized for rapid discharge.
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 enables quick shifting of the lock mechanism to the lock state even at high viscosity conditions and allows for downsizing of the device by reducing the dimension along the rotary axis, improving responsiveness and fluid flow efficiency.
Implementation Method 1
a valve unit including a connecting bolt which is coaxially disposed with the rotary axis, and which connects the driven-side rotational body to the camshaft. The connecting bolt is formed with an advanced-angle port communicating with the advanced-angle chamber, a retarded-angle port communicating with the retarded-angle chamber
Implementation Method 2
the valve unit includes a spool having plural land portions at an outer circumference of the spool, and being formed with a drain flow path inside the spool. The valve unit closes the second pump port with the land portion of the spool and allows the lock port to communicate with the drain flow path
Implementation Method 3
the intermediate lock mechanism is unlocked by the supply of the fluid to the lock flow path, and is shifted in a lock state by the discharge of the fluid from the lock discharge flow path
Data Source
AI summary
A variable valve timing control device includes a valve unit including a spool having a plurality of land portions at an outer circumference of the spool, and being formed with a drain flow path inside the spool. The valve unit allows a second pump port and a lock port to communicate with each other in a case where the spool is set at an unlock position where a lock state of a lock mechanism is released, and the valve unit closes the second pump port with the land portion of the spool and allows the lock port to communicate with the drain flow path in a case where the spool is set at a lock position where the lock mechanism is allowed to be shifted in the lock state.