Transmission Motor Shaft Coupling With Snap Ring Positioning

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Solution Overview

Problem

The machining of the bottom surface of the recess in the motor shaft of a hydraulic motor for positioning the input shaft of the planetary speed reduction mechanism is complicated and increases manufacturing costs.

Innovation Solution

The use of a snap ring on the outer periphery of the drive shaft to position the motor shaft and drive shaft axially, eliminating the need for precise machining of the bottom surface of the spline hole and allowing for easier assembly and reduced manufacturing steps.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the bottom surface of the recess in the motor shaft is precisely machined to ensure positioning accuracy, then the positioning accuracy of the input shaft and motor shaft is improved, but the manufacturing complexity and cost increase

Engineering Contradiction:

Improvepositioning accuracyVSAvoidmanufacturing complexity

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

A positioning ring is introduced as an intermediary component between the motor shaft and input shaft. The positioning ring features an outer peripheral surface that contacts the end surface of the motor shaft and an inner peripheral surface that contacts the end surface of the input shaft, serving as a mediator to achieve accurate positioning without requiring complex machining of the motor shaft recess bottom surface

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The positioning function is segmented from the motor shaft structure and embodied in a separate positioning ring component. This allows the positioning ring to be manufactured independently with standard machining processes, while the motor shaft recess can be manufactured with simpler, less precise machining

Inventive Principle:

Principle #1Segmentation

2Manufacturing precision

If the bottom surface of the recess is precisely machined, then the positioning accuracy is improved, but the manufacturing cost increases

Engineering Contradiction:

Improvepositioning accuracyVSAvoidmanufacturing cost

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The positioning ring acts as a mediator that transfers the positioning function from the complex motor shaft recess to a simpler, standalone component. This segmentation allows the positioning ring to be manufactured using cost-effective machining processes, thereby reducing the overall manufacturing cost while maintaining positioning accuracy

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The positioning ring can be manufactured as a relatively simple, inexpensive component compared to the costly precision machining required for the motor shaft recess. By using a separate, easier-to-manufacture component, the overall system cost is reduced

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Data Source

PatentUS12438415B2Transmission-equipped motor

Publication Date: 2025.10.07 KYB CORP

AI summary

In a transmission-equipped motor, a spline portion is formed at an end portion of a drive shaft of a transmission, and a spline hole with which the spline portion is engaged is formed on an end surface of a motor shaft of a hydraulic motor. A snap ring which contacts an end surface of the motor shaft having the spline hole is provided on an outer periphery of the drive shaft having the spline portion so that the snap ring positions the motor shaft and the drive shaft.