CVT Drive Sheave Assembly With One-Way Belt Braking Lock
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Solution Overview
Problem
Traditional engine braking systems for continuously variable transmissions (CVTs) are inefficient as they rely on the inner surface of the belt engaging a sleeve that is free to rotate, lacking a reliable mechanism to effectively clamp down on the belt during engine braking conditions, especially in vehicles like ATVs and UTVs that require robust terrain handling.
Innovation Solution
The implementation of a drive sheave assembly with an axial activation member and a one-way engagement member that moves axially within a central recess of the fixed sheave, allowing the one-way engagement member to lock onto the sleeve during engine braking, thereby engaging the belt and transferring torque effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the sleeve is free to rotate on the post during engine braking, then the belt can engage the sleeve, but the engine braking efficiency is insufficient due to lack of clamping force
Solution Approach 1:
The one-way engagement member transitions between a free-rotating state (during normal operation) and a locked state (during engine braking), dynamically adapting the system's mechanical constraints based on operational conditions. This allows the sleeve to be free-rotating when not braking but locked when braking is required, resolving the contradiction between reliability and clamping force
Solution Approach 2:
The one-way engagement member acts as an intermediary between the sleeve and the axial activation member, transmitting rotational lock-up forces from the axial activation member to the sleeve during engine braking. This mediator enables the transfer of clamping force while maintaining the free-rotation capability when not engaged
2Force
If the one-way engagement member locks onto the sleeve during engine braking, then clamping force is improved, but the device complexity increases due to additional components
Solution Approach 1:
The one-way engagement member performs multiple functions: it acts as a locking mechanism during engine braking, a free-rotating connector during normal operation, and a force transmission element between the axial activation member and sleeve. This multi-functionality reduces the need for separate dedicated components, offsetting the complexity increase
Solution Approach 2:
The one-way engagement member is nested within the central recess of the fixed sheave assembly, with the axial activation member positioned within the one-way engagement member. This nested arrangement consolidates multiple functional elements into a compact integrated structure, minimizing the space and complexity required for the braking system
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 solution provides a reliable and efficient engine braking system for CVTs by ensuring the belt is securely engaged during braking conditions, enhancing the vehicle's control and stability, particularly in challenging terrains.
Implementation Method 1
The one-way engagement member is configured to rotate freely on the sleeve when the sleeve rotates in a first direction and lock onto the rotation of the sleeve when the sleeve rotates in a second direction
Data Source
AI summary
A drive sheave assembly of a continuously variable transmission is provided that includes a post, a fixed sheave, a movable sheave assembly, a sleeve and an engine braking assembly. The engine braking assembly includes an axial activation member, a one-way engagement member and a flange. The axial activation member is statically mounted within a central recess of the fixed sheave. The axial activation member is movably connected with the one-way engagement member. A central passage of the one-way engagement member is configured to engage a portion of the sleeve. The flange is coupled to the one-way engagement member to selectively engage a side of an endlessly looped member with axial movement of the one-way engagement member during an engine braking condition.