Fixed Constant Velocity Joint With Offset Ball Center of Gravity
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Solution Overview
Problem
Existing constant velocity joints face inefficiencies and reduced service life due to high axial force components and internal friction caused by large articulation angles, which are exacerbated by complex manufacturing processes such as increasing the number of balls or using counter-track joints.
Innovation Solution
A constant velocity joint design that shifts the center of gravity of the balls relative to the joint's median plane, allowing for a more uniform force distribution and reduced manufacturing complexity by maintaining the number of balls and avoiding counter-rotating ball tracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sufficiently large axial offsets are used to ensure adequate control at medium and large articulation angles, then control reliability is improved, but axial force components and internal friction increase, reducing joint efficiency
Solution Approach 1:
The patent changes the geometric parameters of the ball raceways, specifically using different opening angles for alternating ball raceway pairs. This parameter variation allows the joint to maintain control reliability at large articulation angles while reducing the axial force components and internal friction that would otherwise increase with larger axial offsets.
Solution Approach 2:
The patent introduces asymmetry into the otherwise symmetric Rzeppa joint design by creating counter-track joints where alternating ball raceway pairs have different opening angles. This asymmetric configuration allows differential force distribution that reduces internal friction while maintaining control, resolving the contradiction between reliability and energy loss.
2Manufacturing precision
If the number of balls is increased from six to eight to ensure sufficient positioning at small control angles, then positioning accuracy is improved, but device complexity and manufacturing effort increase
Solution Approach 1:
Instead of increasing the number of balls, the patent changes the opening angle parameters of the ball raceways. By varying the opening angles of alternating raceway pairs, the joint achieves sufficient positioning accuracy at small control angles while maintaining the simpler six-ball configuration, thus avoiding increased device complexity.
3Force
If counter-track joints with alternating opening angles are used to balance forces on the cage, then force balance is improved, but manufacturing complexity increases
Solution Approach 1:
The patent implements counter-track joints with alternating opening angles to create force balance on the cage. By making alternating ball raceway pairs have different opening angles, the forces acting on the cage balance each other out, improving force distribution while the patent accepts the associated manufacturing complexity as necessary for achieving this force balance.
Data Source
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AI summary
The invention relates to a constant velocity fixed joint (1) comprising: an outer joint part (2) having a plurality of ball races (7) on the internal periphery, and an inner joint part (3) having a plurality of ball races (8) on the outer periphery, wherein in each case one ball race (7) on the outer joint part (2) and one ball race (8) on the inner joint part (3) form a ball race pair; one ball (6) per ball race pair for torque transmission; and a cage (4) which is arranged between the outer joint part (2) and the inner joint part (3) and has apertures (5) in which the balls (6) are accommodated. The common centre of gravity S of all balls (6) has an axial offset a relative to a joint centre plane E. The joint centre plane E is a plane through a point M and normal to the central axis of the cage (4), M being the centre point between two points PA and PI, PA being the intersection point of the central axis of the cage (4) with the line of action WA of the normal force resulting from the contact of the cage (4) with the outer joint part (2) and PI being the intersection point of the central axis of the cage (4) with the line of action WI of the normal force resulting from the contact of the cage (4) with the inner joint part (3).