CVT Pulley Roller-Arm Assembly for Axial Shift and Torque Transfer
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Solution Overview
Problem
Conventional snowmobile powertrains with continuously variable transmissions (CVT) have separate parts for axial displacement and torque transmission, increasing cost and weight, which is undesirable.
Innovation Solution
A pulley design for CVT that integrates axial displacement and torque transmission using a thrust portion of the arm with multiple contact points on a roller assembly, allowing for simultaneous axial movement and torque transfer between the movable and fixed sheaves, with centrifugal actuators aligned with roller assemblies to manage these functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If separate parts are used for axial displacement and torque transmission, then the functions are clearly divided, but the cost and weight of the primary pulley increase
Solution Approach 1:
The patent combines axial displacement and torque transmission functions into a single integrated component. The arm structure includes both a thrust portion for axial displacement and a torque transmission portion that directly engages with the spider, eliminating the need for separate torque transmission mechanisms while reducing overall component count, weight, and cost
2Device complexity
If separate parts are used for axial displacement and torque transmission, then the functions are clearly divided, but the cost and weight of the primary pulley increase
Solution Approach 1:
The integration of multiple functions into the arm structure reduces the total number of parts that need to be manufactured, assembled, and inventoried. This simplification directly lowers manufacturing complexity and cost while maintaining clear functional differentiation through the integrated design
3Length of moving object
If the arm pivots outwards to displace the movable sheave axially, then axial displacement is achieved, but torque transmission must be maintained through separate mechanisms
Solution Approach 1:
The arm is designed as a multi-functional component where the same structure performs both axial displacement (through pivoting of the thrust portion) and torque transmission (through engagement of the torque transmission portion with the spider). This eliminates the need for separate torque transmission mechanisms while maintaining both functions simultaneously
4Power
If multiple contact points are used between the arm and roller, then torque transmission efficiency is improved, but the complexity of the roller assembly increases
Solution Approach 1:
The roller is designed with a curved track portion that complements the thrust portion geometry, creating multiple natural contact points as the arm pivots. This curved geometry achieves enhanced torque transmission through distributed contact while maintaining a simple roller structure without complex internal mechanisms
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 integrated design reduces the cost and weight of the pulley while maintaining efficient torque transmission and axial displacement, optimizing the performance of the CVT system.
Implementation Method 1
The centrifugal actuators generally consist of centrifugal weights in the form of adjusting arms. Each arm is connected to the movable sheave of the primary pulley by a pin, and pivots outwards about its corresponding pin. As they pivot, the arms are in contact with corresponding rollers disposed on a spider fixed relative to the fixed sheave. When the adjusting arms pivot outwards as a result of centrifugal force, the adjusting arms slide against their corresponding roller and the axially movable sheave is pushed towards the fixed sheave.
Implementation Method 2
The movable sheave is movable axially toward the fixed sheave by the action of the centrifugal actuators and away from the fixed sheave by a biasing spring.
Implementation Method 3
The thrust portion of the arm has at least one contact point with the track portion of the roller.
Data Source
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AI summary
A pulley for a CVT has a fixed sheave, a movable sheave, a spider, a biasing member biasing the movable sheave axially away from the fixed sheave, at least one centrifugal actuator and at least one roller assembly. The at least one centrifugal actuator has an arm pivotally connected to one of the movable sheave and the spider. The arm has a thrust portion pushing against a track portion of a roller of the at least one roller assembly upon rotation of the CVT, the roller being rotationally connected to another one of the movable sheave and the spider. The roller receives the thrust portion of the arm on the track portion thereof such that the thrust portion of the arm remains in contact with the track portion of the roller. The arm and the roller thereby transfer axial and rotational forces between the spider and the movable sheave.