In-Wheel Ring Gear Coupling for Precise Bearing Axis Alignment
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Solution Overview
Problem
Existing in-wheel drive devices face issues with thermal deformation of the ring gear and wheel bearing due to heat treatment, and difficulty in aligning the central axes of the ring gear and wheel bearing due to concave-convex structures, which degrade the quality of the device.
Innovation Solution
The in-wheel drive device incorporates a protruding portion on the ring gear and a recessed portion on the wheel bearing or speed reducer housing, allowing for engagement and alignment without the need for heat treatment, ensuring proper axis alignment and preventing slippage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If heat treatment is used to couple the ring gear to the wheel bearing, then the coupling strength is improved, but thermal deformation occurs degrading quality
Solution Approach 1:
The patent replaces the thermal coupling method with a mechanical coupling method using protruding portions and recessed portions. The protruding portions on the ring gear engage with corresponding recessed portions on the wheel bearing, achieving secure coupling without heat treatment, thereby avoiding thermal deformation while maintaining coupling strength.
Solution Approach 2:
The coupling interface is segmented into multiple protruding portions and recessed portions distributed around the ring gear and wheel bearing. This segmentation allows for precise alignment and distribution of coupling forces, achieving strong coupling without requiring thermal deformation.
2Ease of manufacture
If concave-convex portions are formed for coupling, then mechanical assembly is enabled, but central axis alignment becomes difficult
Solution Approach 1:
The patent uses asymmetric protruding and recessed portions that are strategically positioned to guide alignment. The asymmetric geometry ensures that the ring gear and wheel bearing can only assemble in the correct orientation, automatically aligning their central axes while maintaining ease of mechanical assembly.
3Device complexity
If the ring gear and wheel bearing are assembled with cylindrical shapes, then manufacturing is simplified, but precise alignment is difficult due to concave-convex portions
Solution Approach 1:
The patent adds radial protruding portions and corresponding recessed portions to the otherwise simple cylindrical structures of the ring gear and wheel bearing. This dimensional addition provides alignment features without significantly increasing overall structural complexity, enabling precise axis coincidence while maintaining manufacturing simplicity.
Data Source
AI summary
An in-wheel drive device includes: a wheel bearing including a hub and an outer race spaced apart outward in a radial direction from the hub; and a speed reducer including a ring gear coupled to the wheel bearing. An outer surface of the ring gear, in the radial direction, and an inner surface of the wheel bearing, in the radial direction, adjoin to define first and second regions. The ring gear includes a protruding portion disposed on the outer surface of the ring gear in the second region and having a shape protruding toward the inner surface of the wheel bearing. The wheel bearing includes a recessed portion disposed on the inner surface of the wheel bearing in the second region and having a shape corresponding to a shape of the protruding portion. The protruding portion and the recessed portion engage each other in the second region.