Torque Limiter Shaft Geometry Without Parallel Pins

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Solution Overview

Problem

The use of parallel pins to restrict rotation on shafts in image forming apparatuses increases machining and assembly costs due to the need for additional processing and precise alignment.

Innovation Solution

A shaft design with a rotation restricting portion that includes an outer circumferential portion and engaging portions with a tip of R shape, allowing direct engagement with a torque limiter without the need for parallel pins, formed through forging to reduce machining and assembly costs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If parallel pins are used to restrict rotation on the shaft, then the rotation restriction function is achieved, but the machining and assembly costs increase due to additional processing and precise alignment requirements

Engineering Contradiction:

Improverotation restriction functionVSAvoidmachining and assembly costs

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The invention merges the rotation restricting function into the shaft itself by providing a rotation restricting portion with an engaging portion that directly engages with the torque limiter. This eliminates the need for separate parallel pins and their associated machining and assembly operations, thereby reducing manufacturing costs while maintaining the rotation restriction function.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The invention extracts the rotation restriction function from the separate parallel pin component and integrates it into the shaft structure. The rotation restricting portion with the engaging portion is provided directly on the shaft, allowing it to restrict rotation without requiring additional parallel pin components.

Inventive Principle:

Principle #2Taking out (Extraction)

2Reliability

If multiple parts and machining operations are used to fix the torque limiter to the shaft, then the torque limiter can be securely mounted, but the manufacturing cost increases

Engineering Contradiction:

Improvetorque limiter mounting securityVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The invention merges the torque limiter mounting function into a simplified structure where the rotation restricting portion with the engaging portion on the shaft directly engages with the torque limiter. This eliminates the need for multiple separate parts and complex machining operations such as cutting and press fitting, thereby reducing manufacturing cost while maintaining secure mounting.

Inventive Principle:

Principle #5Merging (Combining)

3Reliability

If the engaging portion has a complex shape for precise engagement, then the rotation restriction is more reliable, but the forging process becomes more difficult

Engineering Contradiction:

Improveengagement reliabilityVSAvoidforging difficulty

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The engaging portion is designed with an R-shaped tip portion that has a curved surface. This curved shape facilitates smooth engagement with the torque limiter during the forging process, reducing forging difficulty while maintaining reliable rotation restriction functionality.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The invention optimizes the geometric parameters of the engaging portion, specifically the R-shaped tip portion with controlled radius and width, to achieve a balance between engagement reliability and forgeability. The width in the direction perpendicular to the inserting direction is specifically designed to be insertable into the torque limiter's engaging portion.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS20260042627A1Shaft and image forming apparatus

Publication Date: 2026.02.12 CANON KK

AI summary

A shaft on which a torque limiter is mounted includes a rotation restricting portion. The rotation restricting portion is inserted into and engaged with an engaging portion of the torque limiter. The rotation restricting portion is provided with an outer circumferential portion which is projected in an outer diameter direction from an outer circumference of the shaft and of which an outer circumferential surface is formed parallel with an outer circumferential surface of the shaft and an engaging portion connected to the outer circumferential portion and engaging with the engaging portion of the torque limiter. The engaging portion of the rotation restricting portion is provided with a tip portion of a R shape opposing the engaging portion of the torque limiter, and a width thereof in a direction perpendicular to an inserting direction into the engaging portion of the torque limiter is a width capable of being inserted into the engaging portion of the torque limiter.