CVT Roller Guide Path Geometry for Pulley Stress Reduction
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Solution Overview
Problem
The existing belt-type continuously variable transmission devices experience stress concentration at the boundary between the guide surface and the end face due to the reaction force from the driving belt, which affects the durability of the pulley.
Innovation Solution
A recessed surface is introduced between the guide surface and the end face, reducing stress concentration and allowing for improved durability by preventing radial movement of the roller weight from the hub, thus avoiding stress concentration on the hub and simplifying processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the guide surface is connected to the end face at an acute angle to guide roller weight displacement, then the pulley can achieve variable transmission ratio, but stress concentrates at the boundary between the guide surface and the end face
Solution Approach 1:
The patent applies curvature by replacing the acute angle connection between the guide surface and end face with a curved surface. This curved surface smoothly connects the guide surface to the end face, eliminating the stress concentration that occurs at sharp corners while maintaining the functional geometry needed for variable transmission ratio through roller weight displacement.
2Ease of operation
If the guide surface crosses the hub outer circumferential surface at an acute angle, then the roller weight can be displaced to push the movable umbrella body, but stress concentrates on the boundary between the guide surface and the hub
Solution Approach 1:
The patent introduces a curved surface that connects the guide surface to the hub outer circumferential surface, replacing the acute angle intersection. This curved transition reduces stress concentration at the hub boundary while preserving the ability of the roller weight to displace and push the movable umbrella body for transmission ratio adjustment.
3Reliability
If a recessed surface is introduced between the guide surface and end face to reduce stress, then durability is improved, but the structure becomes more complex
Solution Approach 1:
The patent implements a curved surface that integrates the stress reduction function into the existing structure without creating a separate recessed cavity. This curved transition surface achieves stress distribution and durability improvement while maintaining structural simplicity and avoiding additional manufacturing complexity.
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 recessed surface effectively reduces stress at the boundary between the guide surface and the end face, enhancing the durability of the pulley by distributing the reaction force and preventing hub stress concentration, while maintaining a large reduction ratio and ease of processing.
Implementation Method 1
The roller weight is configured to displace the movable umbrella body toward the fixed umbrella body, as the roller weight radially moves away from the driving shaft by a centrifugal force that is generated during rotation of the driving shaft.
Data Source
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AI summary
A belt-type continuously variable transmission device (54) includes a roller weight and a guide path (88). The roller weight is pressed on a back side of an umbrella surface of a movable umbrella body (61b). The roller weight is configured to displace the movable umbrella body (61b) toward a fixed umbrella body, as the roller weight radially moves away from a driving shaft by a centrifugal force that is generated during rotation of the driving shaft. The guide path (88) is formed on the back side of the umbrella surface of the movable umbrella body (61b) and includes a guide surface (86a) and an end face (89a). The guide surface (86a) is configured to guide radial movement of the roller weight while restricting circumferential displacement of the roller weight. The end face (89a) is configured to restrict radial movement of the roller weight. The guide surface (86a) is connected to the end face (89a) by a recessed surface (92) that is recessed at the end face (89a). This structure provides a belt-type continuously variable transmission device, configured to reduce stress that is generated at a boundary between a guide surface for a roller weight and an end face.