Electric Power Steering Assembly Coaxiality Guide Shaft Bush
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Solution Overview
Problem
The conventional electric power steering device assembly process faces difficulties in securing coaxiality between the output shaft and the lower shaft, leading to lowered operability due to potential contact between the torque detection sleeve and the torque detection concave-convex part, which complicates the assembly process.
Innovation Solution
The electric power steering device configuration includes a torsion bar with specific coupling shaft parts and a bush, where the axial distance from the bush to the torque detection concave-convex part is made greater than the distance from the guide shaft part to the torque detection sleeve, allowing the guide shaft to be inserted into the bush before the sleeve contacts the concave-convex part, ensuring coaxiality and preventing contact during assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the conventional assembly process is used, then the assembly can be completed, but the operability is lowered due to potential contact between the torque detection sleeve and the torque detection concave-convex part
Solution Approach 1:
The patent applies preliminary action by pre-configuring the axial distances of the bush and guide shaft part before assembly occurs. Specifically, the axial distance from the bush to the torque detection concave-convex part is designed to be greater than the axial distance from the guide shaft part to the torque detection sleeve, ensuring that the guide shaft part enters the bush before the sleeve contacts the concave-convex part. This pre-established geometric relationship prevents assembly issues without requiring complex adjustment procedures during the actual assembly process.
2Ease of operation
If the axial distance from the bush to the torque detection concave-convex part is increased, then contact between the sleeve and concave-convex part is prevented, but the overall device length increases
Solution Approach 1:
The patent applies local quality by making the axial distance adjustment localized rather than increasing the overall device length. The specific region between the bush and torque detection concave-convex part has an increased axial distance to prevent contact, while other portions of the device maintain their original compact dimensions. This localized dimensional adjustment allows the sleeve to clear the concave-convex part during assembly without proportionally increasing the entire device length.
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 effectively prevents contact between the torque detection sleeve and the torque detection concave-convex part, improving the assembly operability by securing coaxiality and allowing smooth advancement of components, thus enhancing the overall assembly process.
Implementation Method 1
The torsion bar includes a first coupling shaft part and a second coupling shaft part which are provided at both axial end portions, a spring shaft part which is provided at an axially intermediate part
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A first connecting part of a torsion bar is connected to a spline hole of a lower shaft, once the proximal end part of a torque-detecting sleeve has been externally fitted on and secured to a cylindrical part provided on the lower shaft, a second connecting shaft part of the torsion bar is inserted from the trailing end side into the inner side of an output shaft. When the lower shaft and the output shaft get closer to each other in the axial direction, the leading end part of a guide shaft part is advanced into the inner-diameter side of the trailing end part of a bush prior to the leading end part of the torque-detecting sleeve being advanced to the outer-diameter side of a part having protrusions and recesses for detecting torque.