Rotary Forging Hub Spline Straightness via Periodic Reciprocation
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Solution Overview
Problem
The existing method for manufacturing wheel-supporting rolling bearing units is costly and compromises durability due to inefficient rotary forging processes, particularly in forming the hub-side face spline, which affects the meshing quality with the constant velocity joint.
Innovation Solution
The method involves rotary forging using a roll with an inclined central axis, periodically changing the interval between the roll support and the hub main body stage to optimize the formation of the hub-side face spline, ensuring proper engagement and minimizing the inclined angle to maintain straightness and durability while reducing manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the inclined angle of the roll's central axis is increased to reduce pressing force, then manufacturing cost is reduced, but the straightness of tooth surfaces deteriorates
Solution Approach 1:
The patent applies periodic reciprocating motion to the roll during rotary forging. The roll moves back and forth in the axial direction while rotating, creating periodic contact zones that distribute the forming action throughout the tooth surface. This periodic action allows the use of a larger inclined angle (reducing pressing force) while maintaining straightness, because the repeated contact patterns ensure uniform material flow and tooth formation without local deformation
Solution Approach 2:
The patent introduces dynamic motion by combining rotation of the roll about the hub's central axis with reciprocating motion along the axial direction. This dynamic approach transforms the static pressing force into a controlled, time-varying process where the contact point moves continuously, allowing optimization of both force magnitude and tooth surface quality through motion control rather than force magnitude alone
2Ease of manufacture
If conventional rotary forging is used with a roll whose central axis is parallel to the hub main body's central axis, then manufacturing process is simple, but the tooth surfaces become deformed and durability is compromised
Solution Approach 1:
The patent introduces asymmetry by inclining the roll's central axis relative to the hub main body's central axis. This asymmetric configuration creates a controlled non-uniform contact pattern during rotary forging, which prevents the localized deformation that occurs with symmetric (parallel) alignment. The inclined angle creates a progressive forming action that distributes stress more evenly, producing straighter tooth surfaces and improving meshing durability
Solution Approach 2:
By combining the inclined axis configuration with periodic reciprocating motion, the patent creates a periodic forming action that systematically works through the entire tooth surface. This periodic action ensures that each portion of the tooth receives uniform forming treatment, eliminating the deformation issues that would otherwise require complex process control to prevent
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the durability of the rolling bearing unit by maintaining the straightness of the tooth surfaces and reducing manufacturing costs by preventing excessive force application and equipment size increases, thus improving the meshing performance with the constant velocity joint.
Implementation Method 1
a hub-side face spline that is a concavo-convex section in a circumferential direction is formed on an end surface of the other end portion in the axial direction by performing rotary forging
Implementation Method 2
the roll is rotated about the central axis of the hub main body in a state in which the processing surface of the roll is pressed toward the end surface of the other end portion in the axial direction
Data Source
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AI summary
A method for manufacturing a rolling bearing unit is provided to periodically reciprocate a stage (38) in a vertical direction by rotating and driving a servo motor (44) while rotating a roll about a central axis of a hub main body using a roll driving motor (43) in a state in which a processing surface of the roll is pressed against other end surface of a caulking section in an axial direction. A period of the reciprocation is restricted by a relation between a rotation position of the roll about the central axis of the hub main body and an engaged state between concave sections, which are sections between a plurality of processed teeth formed in the processing surface of the roll, and a face spline tooth formed by the concave section.