CVT Moving Pulley Assembly with Intermediary Collar Alignment

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Solution Overview

Problem

Conventional continuously variable transmissions (CVTs) face complexity in assembling the crank shaft and moving pulley due to misalignment of keyways, leading to inefficient and cumbersome assembly processes.

Innovation Solution

The implementation of a power unit with a rotating shaft and a moving pulley featuring cylindrical boss and shaft side holes, detent members, and a collar portion with lubricant holding capabilities, which allows for precise alignment and smooth movement, reducing friction and the likelihood of detent member dislodgment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If keyways are formed on the boss of the moving pulley and the crank shaft to enable integral rotation, then the moving pulley and crank shaft can rotate integrally, but the assembly work becomes complex due to misalignment of keyways

Engineering Contradiction:

Improveintegral rotation of moving pulley and crank shaftVSAvoidassembly workability

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

A collar is introduced as an intermediary component between the crank shaft and moving pulley. The collar includes positioning protrusions that engage with positioning recesses on the moving pulley, serving as a mediator to ensure accurate alignment and prevent keyway misalignment during assembly. This intermediary element simplifies the assembly process while maintaining reliable integral rotation.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The collar is pre-positioned on the crank shaft with its positioning protrusions already aligned. This preliminary positioning action allows the moving pulley to be easily attached without requiring complex alignment procedures, as the collar has already established the correct rotational position before the moving pulley is installed.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If the key is press fit into the keyway to prevent coming-off, then the key is secured, but the keyways may get out of position before the key is press fitted, requiring re-alignment

Engineering Contradiction:

Improvekey retentionVSAvoidassembly time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The collar acts as a mediator that maintains keyway alignment during the key insertion process. The positioning protrusions on the collar engage with recesses on the moving pulley before the key is fully inserted, preventing the keyways from misaligning during the press-fit operation. This eliminates the need for re-alignment and reduces assembly time.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The collar's positioning protrusions provide preliminary anti-action by preventing misalignment before it can occur during key insertion. This preemptive measure counteracts the tendency of keyways to get out of position, ensuring they remain aligned throughout the key press-fit process.

Inventive Principle:

Principle #9Preliminary anti-action

3Reliability

If multiple detent members are used to prevent misalignment, then positional agreement is maintained, but the structure becomes more complex

Engineering Contradiction:

Improvepositional agreementVSAvoidassembly structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The collar performs multiple functions: it positions the moving pulley, retains the detent members, and maintains keyway alignment. By consolidating these functions into a single component rather than using separate elements for each function, the overall structure remains simple while achieving reliable positional agreement.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The collar combines the positioning mechanism and detent member retention mechanism into a single integrated component. The positioning protrusions and detent member holes are both features of the collar, merging multiple functions into one element and avoiding the complexity of separate positioning and retention devices.

Inventive Principle:

Principle #5Merging (Combining)

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 enhances the workability of assembling the moving pulley and crank shaft, stabilizes the rotating shaft, and facilitates easy exchange of components, improving assembly efficiency and durability.

Implementation Method 1

a lubricant accumulating portion having a clearance between an outer peripheral surface of the shaft portion and an inner peripheral surface of the lubricant holding portion and accumulating a lubricant in the clearance

Methodology Applied

Scientific EffectLubrication: Lubrication

Implementation Method 2

centrifugal forces generated by the rotating shaft are balanced with each other, so that stability in rotation of the rotating shaft is achieved

Methodology Applied

Scientific EffectCentrifugal force: Centrifugal Force

Data Source

PatentUS8371972B2Power unit and straddle-type vehicle

Publication Date: 2013.02.12 YAMAHA MOTOR CO LTD

AI summary

An engine unit includes a crank shaft that receives a driving force of an engine and a moving pulley that is movable in an axial direction. Keyholes are formed on an outer peripheral surface of the crank shaft. Axially extending guide holes are formed on a boss portion of the moving pulley in positions that correspond to the keyholes. Ends of keys are mounted to the keyholes. The guide holes receive therein bases of the keys to guide relative movements of the moving pulley and the crank shaft in an axial direction.