CVT Movable Sheave Position Detection via Cam-Rotation Linkage

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Solution Overview

Problem

Existing continuously variable transmissions (CVTs) with non-contact position detecting sensors for movable sheaves have complex structures, which complicates the detection of the sheave's axial position.

Innovation Solution

A continuously variable transmission with an electronically controlled position detecting mechanism that uses a rotational shaft and a rotation sensor to detect the position of a movable sheave based on the rotational angle of the shaft, incorporating a cam to convert linear motion into rotational motion and a torsion spring for enhanced accuracy and simplicity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a non-contact position detecting sensor based on magnetic field is used to detect the axial position of the movable sheave, then the detection function is achieved, but the structure becomes complicated

Engineering Contradiction:
Improveposition detection accuracyVSAvoidsensor structure complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces the magnetic field-based non-contact sensor with a mechanical contact-type position detecting sensor that directly contacts the movable sheave. This mechanical approach simplifies the sensor structure while maintaining position detection accuracy, resolving the contradiction between measurement precision and device complexity

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent uses a cam mechanism to convert the axial position of the movable sheave into rotational motion, creating a mechanical copy of the position information. This allows the position to be detected through rotational angle measurement, simplifying the overall detection system structure

Inventive Principle:
Principle #26Copying

2Measurement precision

If the shaft is disposed in a close position to the rotational shaft supporting the movable sheave, then the detection accuracy is enhanced, but the assembly complexity increases

Engineering Contradiction:
Improveposition detection accuracyVSAvoidassembly ease
Core Design Contradiction:
Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent positions the shaft in the radial direction close to the rotational shaft, utilizing the radial dimension to achieve close proximity for accurate detection. This spatial arrangement allows the cam on the shaft to effectively convert axial motion to rotational motion while maintaining manufacturability

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The shaft serves multiple functions: it supports the cam for position conversion, provides a mounting position for the rotation sensor, and maintains close proximity to the rotational shaft for accurate detection. This multi-functionality reduces the need for additional components, simplifying assembly

Inventive Principle:
Principle #6Universality (Multi-functionality)

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 allows for a simple and cost-effective configuration to accurately detect the position of the movable sheave, reducing component count and assembly complexity while enhancing detection accuracy.

Implementation Method 1

The shaft may include a cam converting a linear motion of the movable sheave in the axial direction into a rotational motion of the shaft

Methodology Applied
Scientific EffectCam mechanism: Cam

Implementation Method 2

a rotation sensor detecting a rotational angle of the shaft. The position detecting mechanism detects a position of the movable sheave based on the rotational angle of the shaft detected by the rotation sensor

Methodology Applied
Scientific EffectRotation sensing:

Implementation Method 3

The position detecting mechanism may further include an urging member urging the shaft to one side of a rotational direction of the shaft

Methodology Applied
Scientific EffectMechanical urging force: Spring

Implementation Method 4

The support member may include a bushing disposed on the first end of the shaft. The bushing may extend along the shaft. In this case, the shaft can be inhibited from tilting with respect to the support member

Methodology Applied
Scientific EffectMechanical support and constraint:

Data Source

PatentEP4628752A1Continuously variable transmission and straddled vehicle including same
Publication Date: 2025.10.08 YAMAHA MOTOR CO LTD
  • EP4628752A1 patent drawingFigure 1
  • EP4628752A1 patent drawingFigure 2
  • EP4628752A1 patent drawingFigure 3

AI summary

The present continuously variable transmission (15) includes a rotational shaft (22), a movable sheave (57), and a position detecting mechanism (100); the movable sheave (57) being supported by the rotational shaft (22) to be movable in the axial direction of the rotational shaft (22); the position detecting mechanism (100) including a shaft (104), rotated in conjunction with the movement of the movable sheave (57), and a rotation sensor (102) detecting the rotational angle of the shaft (104); the position detecting mechanism (100) detecting the position of the movable sheave (57) based on the rotational angle of the shaft (104) detected by the rotation sensor (102).