Oldham Coupling Engagement Geometry for Stable Valve Timing Phase Control
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Solution Overview
Problem
Existing valve opening-closing timing control apparatuses using electric actuators suffer from increased friction loss and reduced reliability due to partial engagement between the driving-side rotor and Oldham coupling, leading to abrasion and instability in phase adjustment mechanisms.
Innovation Solution
The apparatus includes a driving-side rotor synchronously rotating with a crankshaft, a driven-side rotor integral with a camshaft, and a phase adjustment mechanism using an Oldham coupling with engagement arms featuring flat surface portions that maintain overlapping contact during sliding, reducing friction and abrasion by ensuring continuous engagement without corner contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the engagement arms of the Oldham coupling are designed with smaller diameter than the driving-side rotor, then the phase adjustment mechanism can operate with eccentric rotation, but corner portions of the engagement arms come into contact with the groove portions causing increased friction loss and abrasion
Solution Approach 1:
The groove portions are designed with rounded inner side surfaces instead of sharp corners, creating a local quality change that prevents corner contact. This localized modification at the engagement interface eliminates the harmful corner contact while maintaining the overall eccentric rotation capability of the Oldham coupling.
Solution Approach 2:
The groove portions are pre-formed with rounded inner side surfaces before assembly, ensuring that the engagement arms slide along the curved surfaces rather than contacting corner portions. This preliminary design feature prevents the harmful contact condition from occurring during operation.
2Ease of operation
If the engagement arms slide with tilted contact against the groove portions, then the phase adjustment can be achieved, but friction loss increases and abrasion occurs reducing reliability
Solution Approach 1:
The inner side surfaces of the groove portions are designed with a specific curved profile that guides the engagement arms to slide in a more aligned manner. This local geometric modification reduces the tilt angle during sliding, thereby reducing friction loss and preventing corner contact while maintaining phase adjustment functionality.
3Adaptability or versatility
If only partial regions of the driving-side rotor and Oldham coupling engage, then the structure can accommodate eccentric motion, but the engagement state becomes unstable causing abrasion
Solution Approach 1:
The groove portions are designed with extended length and rounded inner side surfaces that ensure continuous surface contact with the engagement arms throughout the eccentric motion cycle. This localized design feature stabilizes the engagement state by maintaining consistent contact across the sliding interface rather than intermittent corner contact.
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 engagement state between the Oldham coupling and the driving-side rotor, minimizing friction loss and abrasion, thereby enhancing the reliability and efficiency of the phase adjustment mechanism.
Implementation Method 1
the engagement arms of the Oldham coupling engage with groove portions formed in the driving-side rotor... the engagement arms of the Oldham coupling to slide in a radial direction with respect to the groove portions of the driving-side rotor
Data Source
AI summary
An Oldham coupling includes an engagement arm. At least either a driving-side rotor or an input gear has an engagement portion engaged with the engagement arm and is connected to the Oldham coupling. The engagement arm has a pair of arm flat surface portions perpendicular to a rotational direction of the driving-side rotor. The engagement portion has a pair of engagement flat surface portions that the arm flat surface portions face in a sliding contact manner. Each arm flat surface portion is, within a range where the arm flat surface portion slides against a facing engagement flat surface portion, always in contact with an overlapping portion of the engagement flat surface portion with the arm flat surface portion when viewed from a direction perpendicular to a sliding direction of the Oldham coupling and in which the arm flat surface portion and the engagement flat surface portion overlap each other.