Integrated Shift Shaft Lost Motion for Compact Gear Shifting

Solution Overview

Problem

The existing shift devices for straddle type vehicles have a large shift pedal due to the external placement of the lost motion mechanism, limiting layout flexibility and user convenience.

Innovation Solution

A compact shift device design with a lost motion mechanism integrated into the shift shaft, delaying power transmission to the drive plate, improving operation feel by reducing immediate load transfer to the shift cam.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the lost motion mechanism is provided on the shift pedal outside the engine, then the operation feeling of the shift operation is improved by absorbing the load, but the shift pedal is increased in size and a degree of freedom of a layout of the shift device is reduced

Engineering Contradiction:

Improveoperation feelingVSAvoidshift pedal size

Core Design Contradiction:

Ease of operationVSVolume of moving object

Solution Approach 1:

The lost motion mechanism is merged with the shift shaft structure, integrating the load-absorbing function into the existing shift mechanism rather than adding it as a separate external component. This combines multiple functions into a unified structure, improving operation feeling while maintaining compact dimensions and layout flexibility.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The shift shaft is designed to serve multiple functions: it transmits shift operations and simultaneously incorporates the lost motion mechanism to absorb loads during shifting. This multi-functional design eliminates the need for separate dedicated components, reducing overall size while maintaining the load-absorbing capability that improves operation feeling.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Ease of operation

If the lost motion mechanism is provided on the shift pedal outside the engine, then the operation feeling of the shift operation is improved by absorbing the load, but a degree of freedom of a layout of the shift device is reduced

Engineering Contradiction:

Improveoperation feelingVSAvoidlayout flexibility

Core Design Contradiction:

Ease of operationVSAdaptability or versatility

Solution Approach 1:

The lost motion mechanism is merged with the shift shaft structure, integrating the load-absorbing function into the existing shift mechanism rather than adding it as a separate external component. This combines multiple functions into a unified structure, improving operation feeling while maintaining compact dimensions and layout flexibility.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The shift shaft is designed to serve multiple functions: it transmits shift operations and simultaneously incorporates the lost motion mechanism to absorb loads during shifting. This multi-functional design eliminates the need for separate dedicated components, reducing overall size while maintaining the load-absorbing capability that improves operation feeling.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Volume of moving object

If the lost motion mechanism is integrated into the shift shaft, then a compact structure is achieved and layout flexibility is improved, but the lost motion mechanism must be precisely integrated into the shift shaft structure

Engineering Contradiction:

Improveshift device sizeVSAvoidintegration precision

Core Design Contradiction:

Volume of moving objectVSManufacturing precision

Solution Approach 1:

The lost motion mechanism is segmented into distinct functional elements (spring component, engaging component, and shift shaft portions) that can be manufactured separately and then assembled. This segmentation allows each component to be produced with standard tolerances and then precisely positioned during assembly, reducing the overall manufacturing precision requirements compared to creating a fully integrated monolithic structure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces intermediary components such as the spring and engaging structures that facilitate the connection between the shift shaft portions. These intermediary elements provide tolerance compensation and ease of assembly, allowing the lost motion mechanism to be integrated into the shift shaft with manageable precision requirements while maintaining compact dimensions.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

Enhances user convenience and layout flexibility by absorbing the shift shaft's rotation with a lost motion mechanism, delaying power transmission to improve shift operation feel and reduce immediate load application.

Implementation Method 1

a lost motion mechanism is interposed between the shift shaft and the drive plate, and the rotation of the shift shaft is absorbed by the lost motion mechanism

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Data Source

PatentEP4332412B1Shift device

Publication Date: 2025.09.03 SUZUKI MOTOR CORP

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AI summary

A shift device that causes a transmission device to shift in response to a shift operation of a shift pedal includes a shift shaft configured to rotate in response to the shift operation of the shift pedal, a shift cam configured to rotate in a manner of being capable of changing a coupling state of shift gears of the transmission device, a drive plate configured to move the shift cam in response to the rotation of the shift shaft, and a lost motion mechanism interposed between the shift shaft and the drive plate. The lost motion mechanism is attached to one end portion of the shift shaft and absorbs the rotation of the shift shaft to delay power transmission to the drive plate.