Valve Timing Control Device Stress Reduction
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Solution Overview
Problem
Existing valve opening and closing timing control apparatuses face stress concentration issues due to the small contact surface area between engagement projections and bores, requiring precise processing and lacking effective lubricant discharge mechanisms, especially in deceleration mechanisms with many teeth.
Innovation Solution
A differential deceleration mechanism with a coupling member that allows linear displacement of engagement portions, reducing stress concentration and incorporating a penetration groove for lubricant discharge, which stabilizes the ring gear and facilitates downsizing of the apparatus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If engagement projections engage with engagement bores to transmit rotational force, then the driven-side rotational member rotates by the required angle, but stress concentration occurs due to small contact surface area
Solution Approach 1:
The patent divides the single engagement point into multiple engagement projections (typically three) distributed around the circumference. Each projection engages with a corresponding bore, distributing the transmitted force across multiple contact points. This segmentation reduces stress concentration at each individual contact surface while maintaining the required rotational precision.
Solution Approach 2:
The patent transitions from point contact to surface contact by designing engagement projections with cylindrical outer surfaces that engage with bores having corresponding inner cylindrical surfaces. This dimensional change from point to surface contact increases the contact area, reducing stress concentration while maintaining precise angular positioning.
2Strength
If multiple engagement bores and projections are used to reduce stress concentration, then stress distribution improves, but processing time and accuracy requirements increase
Solution Approach 1:
The patent applies different geometric characteristics to different parts of the engagement mechanism. The engagement projections have specific cylindrical dimensions optimized for stress distribution, while the bores are designed with matching dimensions. The spacing and distribution of multiple projections are carefully designed to balance stress distribution with manufacturability, reducing overall processing complexity compared to alternative designs.
3Ease of operation
If the inner diameter of the engagement bore is specified greater than the outer diameter of the engagement projection, then clearance is provided for rotation, but excess stress is generated upon contact
Solution Approach 1:
The patent optimizes the dimensional parameters of the engagement projections and bores. The outer diameter of engagement projections and the inner diameter of bores are designed to be substantially equal, minimizing clearance while avoiding excessive contact stress. This parameter optimization achieves the balance between allowing necessary rotation and preventing stress concentration.
4Power
If gears with large number of teeth are combined in the deceleration mechanism, then deceleration ratio is achieved, but lubricant discharge becomes difficult
Solution Approach 1:
The patent extracts the lubricant from the enclosed deceleration mechanism through specifically designed discharge paths. The meshing gears are positioned and dimensioned to create natural lubricant flow paths, and discharge openings are provided at strategic locations to enable efficient lubricant ejection from the mechanism, preventing lubricant accumulation and ensuring continuous operation.
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
The solution effectively reduces stress concentration and enhances lubricant circulation, improving the accuracy and efficiency of valve timing control while allowing for a more compact design.
Implementation Method 1
an electric actuator (an electromagnetic portion in Patent document 1)
Implementation Method 2
a part of teeth provided at the inner gear being meshed with a part of teeth provided at an inner periphery of the ring gear
Implementation Method 3
an inner gear (a planetary gear in Patent document 1) is supported at an eccentric shaft eccentric to a center axis of the driving-side rotational member
Data Source
Figure 1
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AI summary
A phase adjustment mechanism is constructed as a differential deceleration mechanism where a ring gear is relatively rotated on a basis of a difference in the number of teeth between the ring gear and an inner gear by revolution of an eccentric axis with reference to a rotation axis by an electric actuator. A coupling member is provided including a first engagement portion engaging with a driving-side rotational member in a displaceable manner in a first direction serving as a radial direction and a second engagement portion engaging with the inner gear in a displaceable manner in a second direction orthogonal to the first direction.