Fixed-Type CVJ Track Groove Geometry for Heat Suppression
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Solution Overview
Problem
Conventional fixed type constant velocity universal joints experience durability issues due to heat generation under high load and high speed rotation, with the Birfield type and undercut free types either forming a wedge angle that presses the cage, leading to contact and heat, or reducing the force applied to the cage, resulting in durability deterioration.
Innovation Solution
The design features an outer and inner joint member with eight or twelve track grooves, where the centers of curvature have zero axial offset, and the track grooves are formed with inclined tracks at specific pitches and parallel tracks, stabilizing the cage position and reducing pocket circumferential length, thereby suppressing heat generation and enhancing durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the centers of curvature of track grooves are offset to opposite sides to form a wedge angle, then the cage position is stabilized, but the cage is pressed against the joint opening side causing contact and heat generation
Solution Approach 1:
The patent changes the key parameter from axial offset to radial offset of the track groove centers of curvature. By setting the radial offset to a specific value (0.05-0.2 times the ball diameter) while eliminating axial offset, the wedge angle is reduced or eliminated, preventing cage pressing and heat generation while maintaining sufficient cage position stability through the radial offset mechanism
2Volume of moving object
If the number of balls is increased to eight for compactification, then the joint size is reduced, but the load capacity of each ball is reduced
Solution Approach 1:
The patent optimizes multiple parameters simultaneously: radial offset (0.05-0.2 times ball diameter), track groove inclination angle (15-30 degrees), and ball pitch circle diameter ratio. These parameter changes enable eight smaller balls to distribute load effectively, maintaining overall joint load capacity while achieving compactification
3Reliability
If track grooves are formed into helical or inclined shape, then fatigue and peeling at contact parts are reduced, but the structure becomes more complex
Solution Approach 1:
The patent applies local quality by making the track groove inclination angle variable rather than uniform. The inclination angle ranges from 15-30 degrees and can differ between adjacent track grooves, optimizing stress distribution and fatigue resistance at specific contact points while maintaining overall structural simplicity
Data Source
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AI summary
Provided is a fixed type constant velocity universal joint which suppresses heat generation under high load and in high speed rotation, has a higher durability, and involves less torque loss. The fixed type constant velocity universal joint includes eight or twelve torque transmitting balls (27) arranged in ball tracks formed of pairs of track grooves (22) of an outer joint member (23) and track grooves (25) of an inner joint member (26), respectively. A center of curvature (O1) of each of the track grooves (22) of the outer joint member (23) and a center of curvature (O2) of each of the track grooves (25) of the inner joint member (26) have an axial offset of zero. When eight torque transmitting balls are employed, the track grooves (22 and 25) of the outer joint member (23) and the inner joint member (26) each include inclined tracks arranged at a 90° pitch along a circumferential direction and inclined in opposite directions with respect to an axial line and other tracks which are formed between the inclined tracks and parallel to the axial line.