Friction Welding Rack Teeth Alignment
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Solution Overview
Problem
The existing method of producing racks for electric power steering devices is complicated and time-consuming due to the need for additional cutting work to correct axial misregistration caused by thermal strain during hot working.
Innovation Solution
A method involving friction welding of three bar pieces - a first bar piece with first rack teeth, a second bar piece with second rack teeth, and an intermediate piece - aligned along a common axis and held at a predetermined intersection angle, then subjected to relative rotation for friction welding to join them, eliminating the need for additional machining and simplifying the production process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hot working is used to form rack teeth on bar pieces, then the rack teeth can be formed efficiently, but thermal strain causes axial misregistration between first and second rack teeth
Solution Approach 1:
The rack is divided into multiple separate bar pieces (first bar piece with first rack teeth, second bar piece with second rack teeth) that are formed independently through hot working. Each bar piece can be manufactured separately and then joined together, allowing the thermal strain effects to be managed at the joining stage rather than compromising the overall alignment
Solution Approach 2:
A third bar piece is introduced as an intermediary element that is friction-welded between the first and second bar pieces. This intermediary piece serves as a mediator that facilitates the connection between the two main rack segments while maintaining the predetermined intersection angle θ between the rack teeth, thereby compensating for any axial misregistration that occurred during independent hot working
2Manufacturing precision
If cutting work is added to correct axial misregistration, then precision of rack teeth alignment is improved, but the production process becomes complicated and time-consuming
Solution Approach 1:
The predetermined intersection angle θ is established during the friction welding process itself, before final assembly. By pre-setting the angular relationship between the first and second rack teeth through the friction welding of the third bar piece, the need for subsequent cutting or machining operations to correct alignment is eliminated
Solution Approach 2:
The conventional mechanical cutting or machining process used to correct axial misregistration is replaced with a friction welding process. The friction welding mechanically joins the bar pieces while simultaneously establishing the correct angular relationship through the predetermined intersection angle θ, substituting a thermal-mechanical process for a purely mechanical correction process
3Manufacturing precision
If cutting work is added to correct axial misregistration, then precision of rack teeth alignment is improved, but production time increases
Solution Approach 1:
The joining operation and alignment operation are merged into a single friction welding process. The friction welding simultaneously accomplishes both the mechanical joining of the bar pieces and the establishment of the correct angular relationship between rack teeth, eliminating the need for separate cutting or alignment operations that would consume additional time
Solution Approach 2:
The friction welding process maintains continuous useful action by performing both joining and alignment functions in one uninterrupted operation. The bar pieces are friction-welded in a continuous process that establishes the predetermined intersection angle θ throughout the welding operation, eliminating idle time or sequential operations that would otherwise be required for separate alignment corrections
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 method allows for the efficient production of precision racks without the complexity and time-consuming processes of the conventional method, ensuring accurate alignment and meshing of rack teeth, thereby improving the efficiency and accuracy of the electric power steering device.
Implementation Method 1
carrying out a second process in which each of the first and second bar pieces (31, 32) and the intermediate piece (33, 33′) are brought into contact with each other at mutually facing ends and subjected to a relative rotation therebetween for a friction welding thereby to join the first bar piece (31), the intermediate piece (33, 33′) and the second bar piece (32) together by the friction welding
Data Source
AI summary
A method of producing a rack is proposed, which comprises aligning a first bar piece, an intermediate piece and a second bar piece in order along a common axis; carrying out a first process in which the first and second bar pieces are stationarily held while showing a predetermined intersection angle between the first rack teeth on the first bar piece and the second rack teeth on the second bar piece; and carrying out a second process in which each of the first and second bar pieces and the intermediate piece are brought into contact with each other at mutually facing ends and subjected to a relative rotation therebetween for a friction welding thereby to join the first bar piece, the intermediate piece and the second bar piece together by the friction welding.