Electric Power Steering Worm Shaft Assembly Using Segmented Elastic Member
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Solution Overview
Problem
Conventional electric power steering apparatuses face difficulties in assembly due to the need for precise alignment of serrations between the damping coupler, driving shaft, and worm shaft, leading to increased assembly time and compromised clearance compensating function.
Innovation Solution
The electric power steering apparatus features a boss with a spoke-like patterned coupling hole and an elastic member with vanes that do not suppress the movement of the worm shaft, allowing for simplified assembly by forming a clearance space between the vanes and the insertion hole, enabling the driving shaft and worm shaft to be coupled without axial or radial interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If serrations are used to connect the damping coupler, driving shaft, and worm shaft, then the rotational force transfer is ensured, but the assembly process becomes complex and time-consuming due to the need for precise alignment
Solution Approach 1:
The patent extracts the alignment requirement from the connection process by using a flange structure with bolt holes instead of serrations. The flange structure allows for connection without the need for precise angular alignment, thereby reducing assembly time while maintaining rotational force transfer capability through the bolted flange connection.
Solution Approach 2:
Instead of using interlocking serrations that require precise alignment, the patent inverts the approach by using a flange structure with clearance holes that can be easily aligned and secured with bolts. This inversion transforms a complex alignment problem into a simple bolting operation.
2Strength
If the elastic member is tightly fitted between the boss and worm shaft, then the connection strength is improved, but the movement of the worm shaft in axial and radial directions is suppressed
Solution Approach 1:
The patent applies local quality by providing clearance spaces at specific locations between the elastic member and the boss insertion hole, while maintaining a tight fit in other areas. This allows the elastic member to provide connection strength through friction and contact in most regions, while the localized clearances permit necessary axial and radial movement of the worm shaft.
Solution Approach 2:
The elastic member is segmented with vanes that create localized clearance spaces, allowing different regions of the elastic member to have different functional properties - some regions provide tight connection while others allow movement. This segmentation resolves the contradiction between connection strength and movement freedom.
3Reliability
If the elastic member is designed to compensate for clearance, then the engagement stability is improved, but the assembly process becomes more complex
Solution Approach 1:
The elastic member is designed to automatically compensate for clearance through its inherent elasticity and the clearance spaces provided in its structure. The elastic member self-adjusts to maintain stable engagement without requiring complex assembly procedures or additional adjustment mechanisms, thereby improving engagement stability while keeping the assembly process simple.
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
This configuration simplifies the assembly process, reduces the time required for assembly, and maintains the rotational force transfer without disturbing the radial movement of the worm shaft, ensuring stable engagement and efficient operation.
Implementation Method 1
an elastic member having vanes extending in the spoke-like pattern in the radial direction from a center thereof to be inserted into and engaged in the insertion hole, the elastic member being closed at one axial end and formed with a fastening hole at the other axial end
Data Source
AI summary
Disclosed is an electric power steering apparatus for a vehicle and a method of assembling the same. According to the present invention, an elastic member provided between a boss and a worm shaft does not suppress the movement of the worm shaft in the axial direction and in the radial direction, a process of assembling the driving shaft of the motor and the worm shaft can be simplified, and a time required for assembly can be reduced.