Electric Power Steering Worm Gear Housing With Inclined Casing End
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Solution Overview
Problem
Existing electric power steering devices are limited by their size, making it difficult to further reduce their dimensions due to the parallel orientation of the lid member to the worm wheel, which impedes efficient reduction of the housing height.
Innovation Solution
The electric power steering device is designed with an inclined orientation of the casing end part and a unique arrangement of flanges and seals, allowing for a smaller footprint by reducing the height of the housing and optimizing the placement of components such as the worm wheel and worm shaft.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the lid member is disposed substantially parallel to the worm wheel to facilitate machining, then the machining work can be carried out with ease, but the height of the housing cannot be further reduced
Solution Approach 1:
The patent applies asymmetry by making the opening part of the casing end part inclined rather than parallel to the worm wheel. The opening part is positioned closer to the worm wheel on one side than on the other side, creating an asymmetric configuration that reduces housing height while maintaining machining feasibility through the inclined design
Solution Approach 2:
The patent changes the orientation of the opening part from a parallel arrangement (two-dimensional plane) to an inclined arrangement that utilizes the third dimension. This dimensional change allows the opening part to be positioned at an angle relative to the worm wheel, enabling height reduction while preserving manufacturing accessibility
2Volume of moving object
If the tip end of the casing end part is disposed as low as possible to reduce device size, then the overall size can be reduced, but the sealing effectiveness may be compromised
Solution Approach 1:
The patent applies local quality by providing different distances from the end surface of the worm wheel to the tip end of the casing end part at different locations. The opening part is positioned at a first distance on one side and a second distance on the other side, creating localized variations that maintain sealing effectiveness at critical areas while minimizing overall device size
Solution Approach 2:
The asymmetric positioning of the opening part allows the casing end part to be optimized for sealing at specific locations while reducing height at others. The inclined configuration ensures that the opening part remains at an appropriate distance from the worm wheel where sealing is critical, while allowing height reduction at non-critical areas
Data Source
AI summary
An electric power steering device includes an assist pinion shaft, a worm wheel attached to an end part on the Z2 side of the assist pinion shaft, a worm shaft that has shaft teeth meshing with wheel teeth, and a casing that houses the worm shaft and the worm wheel. Among a plurality of parts of the wheel teeth, a first part is a part that meshes with the shaft teeth, and a second part is a part located on the opposite side of the first part with a central axis interposed therebetween. The first distance from an end surface on the Z1 side of the first part to a tip end of a casing end part is greater than the second distance from an end surface on the Z1 side of the second part to a tip end of the casing end part.