Segmented Support Shaft for Accurate Resin Case Fixation
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Solution Overview
Problem
The existing motor devices for decelerating and outputting the rotation of an armature shaft in power window and sunroof devices face issues with the accurate fixation of a steel support shaft to a resin case, leading to variations in the spacing between the fixing leg and the support shaft, which affects the operation of the driven object.
Innovation Solution
A motor device design featuring a support shaft with a large-diameter part embedded in the case, a small-diameter part exposed outside, and a step part between them, where the small-diameter part is formed through a drawing process to improve dimensional accuracy and resistance, ensuring accurate positioning and secure fixation within the case.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a steel support shaft is fixed to a resin case using insert molding, then the support shaft can be securely fixed, but dimensional accuracy of the support shaft external diameter varies leading to positioning errors
Solution Approach 1:
The support shaft is segmented into two distinct parts: a large-diameter portion for embedding in the resin case and a small-diameter portion for precise positioning. This segmentation allows each part to optimize its function - the large-diameter part provides sufficient surface area for strong fixation while the small-diameter part achieves high dimensional accuracy through drawing process, thereby resolving the contradiction between fixation strength and manufacturing precision.
Solution Approach 2:
Different portions of the support shaft are given different diameters and functions. The large-diameter part is optimized for mechanical bonding strength within the resin case, while the small-diameter part is optimized for dimensional accuracy and positioning precision. This local differentiation of quality allows simultaneous achievement of strong fixation and high precision.
2Ease of manufacture
If the support shaft external diameter has low dimensional accuracy, then manufacturing is easier, but the support shaft cannot be set accurately in the mold causing rattling and inclination
Solution Approach 1:
The support shaft is divided into segments with different manufacturing requirements. The large-diameter part can be manufactured with standard tolerances for ease of production, while the small-diameter part is specifically processed through drawing to achieve high dimensional accuracy. This segmentation resolves the contradiction by allowing different manufacturing approaches for different functional regions.
3Device complexity
If the support shaft is made with uniform diameter, then manufacturing is simpler, but the fixation strength and positioning accuracy cannot be simultaneously optimized
Solution Approach 1:
Rather than using a uniform diameter shaft, the invention segments the shaft into large-diameter and small-diameter portions. This segmentation enables the large-diameter part to provide strong fixation through increased surface area while the small-diameter part provides precise positioning. The relatively simple two-part structure minimizes complexity increase while significantly improving reliability.
Solution Approach 2:
The shaft structure applies local quality differentiation where the large-diameter portion is optimized for fixation strength and the small-diameter portion is optimized for positioning accuracy. This localized optimization of structural properties achieves high reliability without requiring complex multi-component designs.
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 design enhances the dimensional accuracy and secure fixation of the support shaft, stabilizing the motor device's performance and preventing variations from product to product, thereby improving yield and ensuring stable operation of the driven object.
Implementation Method 1
the small-diameter part is formed through a drawing process which presses a round bar made of steel and set in a die from an axial direction to push an axial tip end side of the round bar into a small-diameter part molding recess provided in the die
Data Source
AI summary
Provided are a motor device and a method for manufacturing the same that can accurately and consistently provide a support shaft to a case and enhance the strength for fixing the support shaft to the case. A small-diameter part having a smaller diameter than a large-diameter part is formed through drawing. The large-diameter part and a step part are embedded in a gear case. The small-diameter part is exposed outside the gear case. The dimensional accuracy (dimensional tolerance ±α) of the external diameter of the small-diameter part is enhanced. The small-diameter part can be set, without rattling, in a lower mold for molding the gear case. Consequently, the support shaft can be accurately and consistently provided to the gear case. Because the large-diameter part and the step part are embedded in the gear case, the resistance of the support shaft against pulling from the gear case can be enhanced.