Spool Clearance Segmentation in Valve Timing Control
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Solution Overview
Problem
Existing valve opening/closing timing control apparatuses face challenges in maintaining accuracy while ensuring responsiveness, often requiring strict accuracy management and resulting in increased sliding resistance due to complex configurations.
Innovation Solution
The apparatus includes a connecting bolt with advanced and retarded angle ports, a sleeve with communication holes, and a spool with land portions and intermediate apertures, allowing for efficient fluid supply with reduced pressure loss and sliding resistance by setting specific clearances and using a compression coil spring for biasing, enabling easy management of accuracy and improved responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the spool is slidably fitted onto the sleeve with coincident axes, then responsiveness is improved, but manufacturing precision requirements increase significantly
Solution Approach 1:
The patent divides the clearance into two independent segments: first clearance between the spool and sleeve, and second clearance between the spool and connecting bolt. This segmentation allows each clearance to be controlled independently, reducing the overall manufacturing precision requirement while maintaining responsiveness. The spool can slide smoothly without requiring all three axes (inner surface of connecting bolt, spool axis, and outer surface of sleeve) to be coincident with high accuracy.
2Loss of energy
If multiple clearances are set to small values, then pressure loss is reduced, but sliding resistance increases
Solution Approach 1:
The patent applies different clearance values to different locations of the spool assembly. The first clearance (between spool and sleeve) is set to a smaller value to reduce pressure loss in the fluid passage, while the second clearance (between spool and connecting bolt) is set to a larger value to reduce sliding resistance. This local differentiation of clearance sizes optimizes both pressure loss and sliding resistance simultaneously.
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 allows for efficient fluid supply with minimal pressure loss and low sliding resistance, enhancing the responsiveness of the valve opening/closing timing control apparatus while simplifying accuracy management and reducing the complexity of the machining process.
Implementation Method 1
a compression coil spring that biases the spool in a protruding direction
Data Source
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AI summary
A valve opening/closing timing control apparatus (A) includes: a driving side rotator (20) configured to rotate synchronously with a crankshaft (1) of an internal combustion engine (E); a driven side rotator (30) disposed coaxially with a rotation axis (X) of the driving side rotator and configured to rotate integrally with a valve opening/closing camshaft (5); a connecting bolt (40) disposed coaxially with the rotation axis to connect the driven side rotator to the camshaft, and having an advanced angle port (41a) and a retarded angle port (41b) formed to extend from an outer peripheral surface to an inner space (40S) thereof, the advanced angle port and the retarded angle port communicating with an advanced angle chamber (Ca) and a retarded angle chamber (Cb) between the driving side rotator and the driven side rotator, respectively; and a valve unit (Vb) disposed in the inner space of the connecting bolt.