Cage Offset Angle Design for CVJ Strength
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Solution Overview
Problem
Conventional fixed type constant velocity universal joints face challenges in reducing size and weight while maintaining strength and durability, particularly at high operating angles, due to thinning of the cage, which compromises rigidity and load-bearing capacity.
Innovation Solution
The design incorporates an outer and inner joint member with six track grooves, a cage with offset curvatures, and specific ratios of cage thickness to pitch circle radius and ball diameter, along with irregular track groove pitches, to enhance strength and durability by increasing the thickness of the cage at the joint opening side and using larger balls, thereby preventing ball run-on and ensuring high-angle torque capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the cage thickness is reduced to downsize the universal joint, then the size and weight are reduced, but the strength and rigidity of the cage deteriorate
Solution Approach 1:
The cage is designed with non-uniform thickness distribution, where the thickness varies in the circumferential direction. Specifically, the thickness is greater at positions corresponding to the track groove centers and smaller at intermediate positions, allowing the cage to maintain sufficient strength at critical load-bearing locations while reducing overall material usage and weight.
Solution Approach 2:
The invention changes the thickness parameter of the cage from a constant value to a variable value that depends on the circumferential position. The thickness is optimized to provide adequate strength where balls transmit torque (at track groove centers) while minimizing material in less critical areas, thereby resolving the contradiction between downsizing and maintaining strength.
2Volume of moving object
If the offset angle of the cage is reduced to thin the cage, then the size is reduced, but the high-angle strength deteriorates
Solution Approach 1:
The cage thickness is locally optimized based on the operational requirements. By making the thickness variable in the circumferential direction rather than uniform, the design ensures adequate strength at critical positions (where balls contact the track grooves) while allowing thinner sections elsewhere, thus maintaining high-angle strength without excessive overall thickness.
Solution Approach 2:
The invention applies parameter changes by defining the cage thickness as a function of circumferential position. This allows the thickness parameter to be optimized for high-angle operation at critical locations while reducing the average thickness, thereby improving the ratio of high-angle strength to overall size.
3Weight of moving object
If six balls are used instead of eight balls, then the size and weight are reduced, but the torque transmission capacity may be affected
Solution Approach 1:
The invention changes several parameters simultaneously: reducing the number of balls from eight to six, optimizing the ball diameter, adjusting the track groove pitch, and varying the cage thickness. These parameter changes are coordinated to maintain torque transmission capacity with fewer balls. The larger ball diameter and optimized spacing compensate for the reduced number of balls.
Solution Approach 2:
With six balls instead of eight, the track grooves are spaced differently around the circumference. The cage thickness is locally optimized at these six positions to provide adequate support for torque transmission. The local quality of the cage structure is enhanced at ball contact positions to compensate for having fewer balls share the load.
Data Source
AI summary
A fixed type constant velocity universal joint is capable of reducing the size and weight of a cage while keeping the strength of the cage, and is also capable of improving the high angle strength and the durability. An offset angle θCAGE of the cage, which is defined by lines that connect a center curvature of an inner spherical surface and a center curvature of an outer spherical surface of the cage and centers of torque transmission balls, and a line that connects the centers of the torque transmission balls and a joint center in a state where a joint operating angle is 0°, is set in a range of 2.7°≦θCAGE<5.7°.