Hollow Rack End Portion Diameter Reduction and Strength Enhancement
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Solution Overview
Problem
The existing hollow rack used in automotive power steering systems faces challenges in maintaining the strength of the end portion, particularly the internal threaded portion, which can lead to loosening of screws and slippage of ball joints due to insufficient hardness, especially under increased load from larger vehicles.
Innovation Solution
A method and apparatus for reducing the diameter of the hollow rack's end portion by forming depressions and using a compression die with a jig system to deform the end portion, combined with high-frequency hardening and tempering processes to enhance the strength and accuracy of the threaded portion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the end portion of the hollow rack is ground to reduce diameter, then the assembly and disassembly properties are improved, but the strength of the end portion is lowered
Solution Approach 1:
The end portion of the hollow rack is divided into multiple segments through grooves, creating a stepped structure with different diameters. This segmentation allows the end portion to have reduced diameter for better assembly properties while maintaining the overall structural integrity and strength through the segmented design.
Solution Approach 2:
The hollow rack exhibits local quality variation where the end portion has a reduced diameter compared to the main body. This local modification improves assembly and disassembly properties at the end portion without compromising the overall strength of the rack, as the main body retains its full diameter and structural integrity.
2Strength
If the diameter of the end portion is reduced by pressing a compression die, then the strength is maintained, but the number of processing steps increases
Solution Approach 1:
The groove formation process and the diameter reduction process are merged into a single integrated operation. The compression die simultaneously forms the grooves and reduces the diameter of the end portion, eliminating the need for separate processing steps and reducing overall device complexity.
Solution Approach 2:
The grooves are formed in advance during the compression die pressing operation, before final assembly. This preliminary action of groove formation integrated with diameter reduction simplifies the overall manufacturing process by combining multiple operations into one preliminary step.
3Manufacturing precision
If multiple processing steps are used to reduce end portion diameter, then processing precision is maintained, but productivity decreases
Solution Approach 1:
Multiple processing functions (groove formation and diameter reduction) are merged into a single compression die pressing operation. This integration maintains processing precision through the controlled single-step operation while significantly improving productivity by eliminating sequential processing steps.
Solution Approach 2:
The compression die pressing operation continuously performs both groove formation and diameter reduction in a single uninterrupted action. This continuous useful action maintains precision through consistent controlled deformation while improving productivity by eliminating idle time between separate operations.
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
The method effectively reduces the number of processing steps, increases the strength of the end portion, and maintains the processing accuracy of the internal threaded portion, preventing delayed destruction and ensuring reliable operation under increased loads.
Implementation Method 1
pressing a compression die having an inside diameter smaller than the diameter of the outside periphery of the portion on the other end side onto the outer periphery of the end portion on the other end side projected from the jig up to a press-in depth determined preliminarily based on the rack such that the die approaches the jig so as to deform the end portion on the other end side plastically whereby the end is narrowed
Implementation Method 2
nipping the portion on the one end side with a jig including a first jig member having a pair of convex portions which are to be fitted to the depressions in contact with the tooth side face and the inclined portion
Data Source
AI summary
The one end side portion is nipped by a jig including a jig member having a pair of convex portions which are to be fitted to a depressions in contact with a tooth side face and a inclined portion and positioning a bar and a jig member which is to be clamped/opened with respect to the jig member. A die having an inside diameter smaller than the diameter of the outer periphery is pressed onto the outer periphery of the end portion of the cylindrical end side portion projected from the jig up to a press-in depth determined preliminarily based on the rack, so as to reduce the diameter of the end portion.