Gear Housing Rib Structure for Worm-Wheel Deformation Control

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Solution Overview

Problem

Existing gear housings in electric assist devices experience deformation due to meshing reaction forces, and existing rib structures do not effectively suppress this deformation during use.

Innovation Solution

The gear housing design includes a wheel housing section with a tubular portion and a worm housing section connected by ribs that extend in the radial direction, connecting fitting tubular portions for the worm and wheel bearings, enhancing structural rigidity and preventing deformation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If ribs are added to connect worm housing section and wheel housing section, then deformation suppression is improved, but manufacturing complexity increases

Engineering Contradiction:

Improvegear housing deformation suppressionVSAvoidhousing structure complexity

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The gear housing is segmented into functionally distinct sections: a wheel housing section accommodating the worm wheel and a worm housing section accommodating the worm, connected by ribs. This segmentation allows targeted reinforcement at connection points while maintaining manufacturing feasibility through modular design.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Ribs are strategically positioned at specific locations where meshing reaction forces are transmitted, providing localized reinforcement exactly where needed. The ribs connect the wheel housing section and worm housing section at points experiencing separation and twisting forces, optimizing structural efficiency without unnecessary complexity.

Inventive Principle:

Principle #3Local quality

2Strength

If rib positions are optimized for deformation suppression, then housing rigidity is improved, but material fluidity during manufacturing deteriorates

Engineering Contradiction:

Improvehousing rigidityVSAvoidmaterial fluidity

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The rib design parameters (position, size, shape) are optimized to balance structural reinforcement with manufacturing considerations. Ribs are positioned to provide maximum rigidity improvement while maintaining adequate material flow paths during casting or injection molding, resolving the conflict between strength and ease of manufacture.

Inventive Principle:

Principle #35Parameter changes

3Power

If meshing reaction forces are transmitted to housing sections, then torque transmission is improved, but housing deformation increases

Engineering Contradiction:

Improvetorque transmissionVSAvoidhousing deformation

Core Design Contradiction:

PowerVSStability of the object's composition

Solution Approach 1:

The ribs act as structural countermeasures against the separating and twisting forces generated by meshing reaction forces. By providing opposing structural support at the connection between wheel housing section and worm housing section, the ribs prevent deformation while allowing the meshing forces to be effectively transmitted for torque generation.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

Data Source

PatentUS12466467B2Gear housing and electric assist device

Publication Date: 2025.11.11 NSK STEERING & CONTROL INC

AI summary

The gear housing including a wheel housing section, a worm housing section, and a one side rib that protrudes from a side surface on one side in the axial direction of a bottom portion for wheel of the wheel housing section and connects a fitting tubular portion for wheel of the wheel housing section and a fitting tubular portion for worm on one side in the axial direction of the worm housing section into which a bearing for worm or a bearing holder holding the bearing for worm is internally fitted.