Variable Valve Timing Torsion Spring Installation
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Solution Overview
Problem
In variable valve timing control apparatuses, the torsion spring tends to tilt and potentially come out of its retaining groove when the vane rotor rotates relative to the housing, due to excessive diameter-reduction twisting, leading to instability and improper valve timing.
Innovation Solution
The torsion spring is designed with an outside diameter greater than the spring guide's inside diameter before installation, allowing it to be shrunk and securely fitted, minimizing the urging force and preventing tilt during rotation, with one end retained by the vane rotor and the other by the housing, and using a spring guide to accommodate the torsion spring axially.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the torsion spring is designed with a small outside diameter in free state, then it can be easily installed in the spring guide, but it tilts and may come out of the retaining groove when the vane rotor rotates
Solution Approach 1:
The patent changes the dimensional parameter of the torsion spring by designing its outside diameter in the free state to be larger than the inside diameter of the spring guide. This parameter change ensures that when the spring is installed and compressed, it maintains sufficient contact with the spring guide wall, preventing tilt and disengagement during rotation while still allowing for practical installation procedures
2Force
If the torsion spring is twisted in the diameter-reducing direction during rotation, then it provides the necessary urging force, but the gap between the spring and spring guide widens causing tilt
Solution Approach 1:
The patent applies preliminary action by pre-compressing the torsion spring during installation so that its outside diameter in the free state is larger than the spring guide's inside diameter. This preliminary compression creates initial contact pressure between the spring and guide wall, which maintains alignment stability during subsequent rotation and diameter-reducing twisting, preventing the spring from tilting or disengaging
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 stabilizes the torsion spring, ensuring precise valve timing control by preventing tilt and maintaining the spring's guiding effect, thus ensuring reliable engine startability and performance across varying operating conditions.
Implementation Method 1
a torsion spring forcing the vane rotor in one rotation direction with respect to the housing by a retaining configuration... the torsion spring being shrunk when the vane rotor relatively rotates with respect to the housing
Implementation Method 2
the vane rotor relatively rotating to an advanced angle side and to a retarded angle side with respect to the housing by selectively supplying/discharging working fluid to/from the advance working chamber and the retard working chamber
Data Source
AI summary
A variable valve timing control apparatus has a housing; a vane rotor relatively rotating with respect to the housing; a torsion spring always forcing the vane rotor in one rotation direction with respect to the housing; and a spring guide accommodating therein the torsion spring. At least a part of an outside diameter of the torsion spring, before being installed inside the spring guide, is formed to be greater than an inside diameter of an inner wall of the spring guide. In a free state of the torsion spring, after being installed inside the spring guide, in which an urging force of the torsion spring acting on the vane rotor becomes smallest, the outside diameter of the torsion spring is substantially same as the inside diameter of the inner wall of the spring guide or is smaller than the inside diameter of the inner wall of the spring guide.