EPS Nut Pulley Reinforcement to Prevent Slipping and Denting
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Solution Overview
Problem
Existing electric power steering apparatuses experience efficiency degradation and steering instability due to slipping between the ball nut and nut pulley, with the nut pulley being prone to denting from belt tension and tooth jumping, leading to inaccurate assist steering force transmission and noise.
Innovation Solution
The apparatus enhances the rigidity of the nut pulley with a deformation preventing member, integrated through injection molding, to increase coupling force between the ball nut and nut pulley, preventing slipping and denting while reducing weight and noise, and ensuring accurate assist steering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the nut pulley is formed of plastic material to reduce weight, then weight is reduced, but the nut pulley is instantly dented by belt tension and tooth jumping occurs
Solution Approach 1:
The nut pulley is constructed as a composite structure combining plastic material with a deformation preventing member (metal reinforcement). The plastic portion maintains weight reduction while the embedded metal member provides the necessary rigidity to resist belt tension and prevent denting and tooth jumping.
2Ease of manufacture
If the ball nut and nut pulley are coupled through fitting, then assembly is simplified, but coupling force is insufficient causing slipping and power transmission efficiency degradation
Solution Approach 1:
The ball nut and nut pulley are merged into a single integrated component through injection molding, eliminating the fitting interface that caused slipping. This unified structure ensures reliable power transmission while maintaining manufacturing efficiency through automated molding processes.
Solution Approach 2:
The deformation preventing member is nested within the nut pulley structure during injection molding, creating a composite component where the metal reinforcement is embedded in the plastic material. This nested structure provides internal support without adding external complexity.
3Object-generated harmful factors
If the nut pulley is formed of plastic material, then weight is reduced and noise is reduced, but the nut pulley is instantly dented by belt tension
Solution Approach 1:
The nut pulley combines plastic material (for noise reduction and weight reduction) with a deformation preventing member (for strength). This composite approach allows the system to benefit from the noise-reducing properties of plastic while compensating for its weakness in resisting belt tension through the embedded reinforcement structure.
Data Source
AI summary
An electric power steering apparatus includes: a ball nut, which is coupled to a rack bar therein, slides the rack bar, and has a first coupling portion formed to protrude in radial directions from one side of an external circumferential surface such that a fastening member is coupled to the first coupling portion; a nut pulley having a second coupling portion, which is formed to protrude in radial directions from an internal circumferential surface having a hollow therein and which comes in contact with the first coupling portion and to which the fastening member is coupled, and having an external circumferential surface to which the belt is connected and rotates the ball nut; and a deformation preventing member coupled to an opposite end of a portion of the nut pulley in which the second coupling portion is formed.