Conical Cage Contact in Slip Ball Joints for Torque and Fatigue
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Solution Overview
Problem
Constant velocity plunging ball joints in motor vehicles face challenges in fatigue strength and torque encapsulation, particularly in side shaft applications where larger deflection angles are required, leading to reduced service life and increased costs.
Innovation Solution
The design incorporates a conically shaped inner contact surface of the cage with an opening angle greater than zero degrees, allowing for reduced angle of inclination of the second contact surface of the inner joint part, which increases the encapsulation of balls and enhances fatigue strength by allowing higher torque loading without compromising kinematics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the angle of inclination of the second contact surface of the inner joint part is increased to achieve larger deflection angles, then the deflection capability is improved, but the ball encapsulation is reduced leading to decreased fatigue strength
Solution Approach 1:
The invention changes the geometric parameters of the cage's inner contact surface by introducing a conical shape with a specific opening angle (greater than zero degrees). This parameter modification allows the cage to better accommodate the balls during deflection, maintaining optimal ball encapsulation and fatigue strength while enabling larger deflection angles through the modified contact geometry.
Solution Approach 2:
The invention introduces asymmetry by giving the inner contact surface of the cage a conical shape rather than a cylindrical shape. The opening angle of this cone creates an asymmetric geometry that optimizes ball retention during deflection, allowing the joint to achieve larger deflection angles without compromising ball encapsulation or fatigue strength.
2Duration of action of stationary object
If the cage design is modified to improve ball encapsulation and fatigue strength, then the service life is extended, but the manufacturing complexity increases
Solution Approach 1:
The conical inner contact surface is defined by a specific opening angle parameter that can be integrated into existing cage manufacturing processes. By establishing a standardized parameter (opening angle greater than zero degrees), the design achieves improved ball encapsulation and fatigue strength while maintaining compatibility with conventional manufacturing methods, thus limiting the increase in manufacturing complexity.
3Strength
If the opening angle of the inner contact surface is increased to maximize ball encapsulation, then the fatigue strength is enhanced, but the kinematic performance may be compromised
Solution Approach 1:
The invention optimizes the opening angle parameter of the conical inner contact surface to achieve a balance between ball encapsulation and kinematic performance. The opening angle is set to be greater than zero degrees but within a specific range that ensures both enhanced fatigue strength through improved ball retention and maintained kinematic performance for smooth joint operation.
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A constant-velocity slip ball joint (1), at least having a joint outer part (2) with an axis of rotation (3) and with outer ball races (4), a joint inner part (5) with inner ball races (6), a multiplicity of torque-transmitting bowls (7) which are guided in each case in outer and inner ball races (4, 6) which are assigned to one another, and a cage (8) which is equipped with a multiplicity of cage windows (9) which receive in each case one or more of the balls (7); wherein the joint inner part (5) is displaceable relative to the joint outer part (2) by a displacement travel (10) along the axis of rotation (3); wherein at least some of the outer ball races (4) and at least some of the inner ball races (6) have a race inclination angle (11) with respect to the central axis (3); wherein a ball race base (12) of each ball race (4, 6) has, along the displacement travel (10), an in each case constant spacing (13) to the axis of rotation (3) along a radial direction (14); wherein a largest deflection angle (15) of the joint inner part (5) relative to the joint outer part (2) is predefined by contact of an outer contact surface (16) of the cage (8) with a first contact surface (17) of the joint outer part (2) and/or by contact of an inner contact surface (18) of the cage (8) with a second contact surface (19) of the joint inner part (5); wherein the cage (8) has a cage central axis (20) and the inner contact surface (18) is of conical form; wherein the inner contact surface (18) has an opening angle (21) of greater than 0 angular degrees relative to the cage central axis (20).