Worm Reducer Elastic Member Rotation Regulation
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Solution Overview
Problem
Conventional worm reducers in electric power steering systems experience backlash and striking noise due to deformation of arc-shaped elastic portions used for rotation regulation, which compromises noise attenuation and durability.
Innovation Solution
A worm reducer design incorporating a worm shaft, worm wheel, bearing, and an elastic member with an arc-shaped buffer portion and a rotation regulation portion that includes a hollow portion to prevent load transmission and regulate rotation, thereby preventing deformation and striking noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a solid positioning protrusion is used to regulate rotation of the arc-shaped elastic portion, then the rotation can be regulated, but the protrusion deforms under load and transmits deformation load to the elastic portion, causing it to deform and lose noise attenuation capability
Solution Approach 1:
The positioning protrusion is divided into two functional parts: a rigid positioning portion that engages with the housing to prevent rotation, and an elastic absorbing portion that absorbs deformation load through elastic deformation. This segmentation allows the rigid part to provide stable rotation regulation while the elastic part protects the main buffer portion from deformation load, maintaining noise attenuation capability.
Solution Approach 2:
The elastic absorbing portion acts as an intermediary element between the rigid positioning protrusion and the arc-shaped buffer portion. It absorbs and isolates the deformation load generated during rotation regulation, preventing this load from being transmitted to the buffer portion. This intermediary structure ensures that the buffer portion maintains its elastic properties and noise attenuation function.
2Force
If the arc-shaped elastic portion is designed to extend in the load direction to provide sufficient buffer capacity, then it can attenuate bearing movement, but it becomes susceptible to rotation and deformation under load
Solution Approach 1:
The positioning protrusion is designed with asymmetric geometry: it extends in the load direction to provide sufficient buffer capacity for bearing movement attenuation, while having reduced width in the circumferential direction to minimize engagement area with the housing. This asymmetric design allows the protrusion to be compliant under radial load while maintaining stable rotational positioning through the separate positioning portions.
Solution Approach 2:
Different portions of the positioning protrusion have different mechanical properties: the absorbing portion is designed with high elasticity to comply under load, while the positioning portions engaging with the housing have higher rigidity for stable rotation regulation. This local differentiation of mechanical properties allows the single component to simultaneously provide both buffer capacity and rotation stability.
3Stability of the object's composition
If the solid positioning protrusion engages with the inner wall surfaces of the recess to regulate rotation, then rotation is controlled, but deformation load is applied to the arc-shaped elastic portion causing striking noise
Solution Approach 1:
The elastic absorbing portion serves as an intermediary that absorbs the deformation load generated when the positioning protrusion engages with the housing wall surfaces. By placing this elastic element between the rigid positioning structure and the arc-shaped buffer portion, it prevents the deformation load from reaching the buffer portion, thereby eliminating the source of striking noise while maintaining rotation control functionality.
Solution Approach 2:
The deformation load that would normally cause harmful striking noise is converted into beneficial elastic deformation of the absorbing portion. The harmful effect of load-induced deformation is redirected to a dedicated elastic element designed to absorb such deformations, transforming the potential harm into a protective mechanism that shields the main buffer portion from damage.
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
The solution effectively suppresses striking noise and maintains the durability of the elastic member, achieving a low-noise operation in the worm reducer and electric power steering system.
Implementation Method 1
an elastic member including an arc-shaped buffer portion that is interposed between the portion of the inner surface of the housing and an outer peripheral surface of the bearing
Implementation Method 2
The rotation regulation portion includes a hollow portion which suppresses load transmission from the rotation regulation portion to the buffer portion
Data Source
Figure 1
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Figure 3
AI summary
A first end portion (21a) of a worm shaft (21) and a first bearing (22) that supports the first end portion (21a) are housed in a first end housing portion in a housing (20). The first end portion (21a) is urged toward a worm wheel (24) by an urging member (25). A rotation regulation portion housing recess (80) is formed in a portion that defines the first end housing portion on an inner surface (20a) of the housing (20). An elastic member (60) includes an arc-shaped buffer portion (61) that is interposed between the portion that defines the inner surface (20a) and an outer peripheral surface of the first bearing (22), and a rotation regulation portion (62) that extends from the buffer portion (61) and is housed in the rotation regulation portion housing recess (80). The rotation regulation portion (62) includes a hollow portion which suppresses load transmission from the rotation regulation portion (62) to the buffer portion (61) during rotation regulation.