Compact Clutch Design for Power Window Motors
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Solution Overview
Problem
Conventional clutches used in power window motors are bulky due to radially projecting engaging projections, which increase the radial size and hinder compact design requirements.
Innovation Solution
A clutch design featuring a driven-side rotor with a driven-side coupling portion and control surfaces positioned differently in the axial direction, allowing for reduced radial size by preventing the clutch from projecting radially and enabling efficient rotational force transmission when the driving-side rotor rotates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If engaging projections project radially outward from the shaft portion to transmit rotational force, then rotational force transmission is achieved, but the radial size of the clutch increases
Solution Approach 1:
The patent repositions the control surface and driven-side coupling portion at different axial positions rather than having engaging projections extend radially outward. This dimensional reorganization allows the clutch to transmit rotational force without increasing radial size, as the coupling mechanism operates in the axial direction instead.
Solution Approach 2:
Instead of having engaging projections extend radially outward from the shaft to transmit force, the patent inverts the approach by positioning the control surface and coupling portion at different axial positions, with the control surface facing radially outward. This inverted configuration achieves force transmission while maintaining compact radial dimensions.
2Ease of manufacture
If the control surface and driven-side coupling portion are positioned at the same axial location, then assembly is simplified, but the radial size increases
Solution Approach 1:
The patent resolves the contradiction by separating the control surface and driven-side coupling portion in the axial dimension. The control surface is positioned at a first axial position while the driven-side coupling portion is positioned at a second axial position, allowing both components to function effectively without increasing radial size.
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 design reduces the radial size of the clutch and motor, enhances rotational force transmission efficiency, and minimizes noise and component count, while maintaining stable operation and assembly simplicity.
Implementation Method 1
The rolling elements are each located between the clutch housing and one of the control surfaces. When the driving-side rotor is driven to rotate, the driving-side rotor is engaged with the engaging projections of the driven-side rotor with respect to the circumferential direction. Accordingly, the rotational driving force from the rotary shaft is transmitted to the worm shaft via the driving-side rotor and the driven-side rotor.
Implementation Method 2
When the driving-side rotor is not driven to rotate, the rolling element is held between the inner circumferential surface of the clutch housing and the control surface so as to prevent the driven-side rotor from rotating.
Data Source
AI summary
A clutch is provided that includes an annular clutch housing, a driving-side rotor, a driven-side rotor having a control surface, and a rolling element located between the inner circumferential surface of the clutch housing and the control surface. The control surface faces radially outward in the clutch housing. When the driving-side rotor rotates, the rotational driving force of the driving-side rotor is transmitted to the driven-side rotor. When the driving-side rotor is driven to rotate, the rolling element rotates together with the driven-side rotor. When the driving-side rotor is not driven to rotate, the rolling element is held between the inner circumferential surface of the clutch housing and the control surface so as to prevent the driven-side rotor from rotating.