Ground Rack Bar Manufacturing for Precise Steering Shaft Joining
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Solution Overview
Problem
Rack bars in steering devices often suffer from poor shape accuracy due to residual working strain, which affects the operation and joining precision, especially when shaft members with rack teeth are shortened, leading to increased costs and material waste during joining processes.
Innovation Solution
A method involving plastic working to form rack teeth along the entire length of a shaft member, followed by grinding the outer peripheral surface to improve shape accuracy and remove working strain, ensuring precise straightness and diameter consistency, applicable to both hollow and solid rack bars.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If rack teeth are formed by plastic working (forging or pressing), then productivity is improved and variable-pitch rack teeth can be produced, but shape accuracy of the toothed section deteriorates due to residual working strain
Solution Approach 1:
The invention applies preliminary action by performing grinding treatment on the outer peripheral surface of the shaft member before the plastic working process. This preliminary grinding removes the surface layer that will later undergo plastic deformation, and subsequent final grinding after plastic working restores the dimensional accuracy. This sequence of preliminary preparation, processing, and final correction resolves the contradiction between high-speed plastic working and precise dimensional requirements.
2Length of moving object
If the shaft section is shortened to downsize the steering device, then compactness is improved, but joining accuracy deteriorates because centering cannot be performed using only the shortened shaft section
Solution Approach 1:
The invention extends the ground outer peripheral surface from the traditional shaft section into the toothed section area. By utilizing the outer peripheral surface of the toothed section as the centering reference surface through continuous grinding, the effective length for accurate centering is extended without increasing the overall shaft section length. This dimensional extension resolves the contradiction between compactness and joining accuracy.
3Manufacturing precision
If the outer peripheral surface is ground over the entire length including the toothed section, then shape accuracy and joining accuracy are improved, but manufacturing complexity increases
Solution Approach 1:
The invention makes the outer peripheral surface of the toothed section serve multiple functions: it acts as both the centering reference surface for accurate joining and as a supporting surface for rack guide installation. By赋予 the toothed section outer peripheral surface this dual function, the need for separate reference surfaces is eliminated, simplifying the overall manufacturing process while maintaining high precision.
4Manufacturing precision
If cutting is performed after joining to conform shaft members, then joining accuracy is improved, but production time and material waste increase
Solution Approach 1:
The invention performs preliminary grinding of the outer peripheral surface before the joining process, establishing accurate centering and positioning references in advance. This preliminary preparation eliminates the need for post-joining cutting operations to achieve conformance, as the ground surfaces already provide the necessary dimensional accuracy. This resolves the contradiction by achieving precision before joining rather than after, thereby eliminating time-consuming cutting operations and material waste.
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 enhances the shape accuracy of rack bars, facilitating more accurate centering and joining of shaft members, reducing material waste and production time, and lowering costs by eliminating the need for additional cutting steps.
Implementation Method 1
grinding an outer peripheral surface of the shaft member over the entire length of the shaft member including the toothed section
Implementation Method 2
forming a toothed section having a plurality of rack teeth on a shaft member by a plastic working
Data Source
Figure 1
Figure 2A~2C
Figure 3
AI summary
A rack bar (1, 21, 31) includes a shaft member (S1) having a toothed section (2, 12, 22). The toothed section (2, 12, 22) has a plurality of rack teeth (3, 13, 23), and extends over a portion of an entire length of the shaft member (S1) along a longitudinal direction of the shaft member (S1). The shaft member (S1) has a grinding-finished outer peripheral surface extending over the entire length of the shaft member (S1) including the toothed section (2, 12, 22). A method for manufacturing the rack bar (1, 21, 31) includes forming the toothed section (2, 12, 22) by plastic working and grinding the outer peripheral surface to improve shape accuracy.