Forged Steering Shaft Structure for Lightweight Torque Transmission
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Solution Overview
Problem
Steering shafts for automobiles face challenges in reducing weight and improving torque transmission reliability while minimizing production costs, as existing methods like press-fitting and deep hole cutting increase component count, production time, and risk of working defects.
Innovation Solution
A method involving a spline shaft part, stopper part, and intermediate shaft part formed from a single material through forging, where a hole part is recessed and extended axially, reducing cutting processes and weight, and enhancing torque transmission reliability by forming a deep hole with multiple forging steps and metal flow optimization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a second shaft is press-fitted to a hollow first shaft to reduce weight, then the weight of the steering shaft is reduced, but the number of components increases and production cost increases due to fitting processes
Solution Approach 1:
The patent merges multiple shaft components into a single integrated shaft structure. Instead of using separate hollow first shaft and second shaft that require press-fitting, the invention creates one unified shaft with varying wall thicknesses achieved through selective material removal from a solid shaft, eliminating the need for assembly operations while maintaining weight reduction benefits.
Solution Approach 2:
The patent applies segmentation by selectively removing material from specific regions of the shaft to create hollow portions with varying wall thicknesses. This allows weight reduction in non-critical areas while maintaining structural integrity in high-stress regions, achieving weight reduction without requiring multiple separate components.
2Weight of moving object
If deep hole cutting is used to form hollow sections in the steering shaft, then the weight is reduced, but the working time is prolonged and production cost increases
Solution Approach 1:
The patent replaces traditional mechanical cutting operations with a forming process. Instead of using cutting tools to remove material and create hollow sections, the invention uses a forming process that shapes the shaft with varying wall thicknesses directly, significantly reducing working time and eliminating cutting-related production issues.
Solution Approach 2:
The patent changes the manufacturing approach from subtractive (cutting) to formative. By using a forming process that directly creates the desired geometry with varying wall thicknesses, the method eliminates the time-consuming cutting operations while achieving the same weight reduction effect.
3Weight of moving object
If deep hole cutting is performed on a pillar-shaped material, then hollow sections are formed, but position accuracy of the hole decreases and working defects occur due to cutting chips
Solution Approach 1:
The patent replaces the cutting process with a forming process that avoids generating cutting chips. This eliminates the problems of chip accumulation affecting position accuracy and working defects, while still achieving weight reduction through selective material removal in controlled regions.
Solution Approach 2:
The patent converts the potential harm of material removal operations into a benefit by using a forming process that shapes the material without cutting. This approach eliminates the harmful effects of cutting chips while maintaining the ability to create hollow sections for weight reduction.
4Reliability
If multiple shaft parts are used and welded to secure reliability of torque transmission, then the reliability is improved, but the production cost increases
Solution Approach 1:
The patent merges multiple shaft parts into a single integrated component, eliminating the need for welding operations. The unified shaft structure with varying wall thicknesses maintains torque transmission reliability through optimized material distribution while reducing production cost by eliminating assembly operations.
Solution Approach 2:
The patent changes the manufacturing approach from assembling multiple parts to creating a single integrated component with varying wall thicknesses. This parameter change in the manufacturing process eliminates welding requirements while maintaining the structural integrity needed for reliable torque transmission.
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 reduces the weight and improves the reliability of torque transmission for steering devices at lower production costs by minimizing cutting processes and preventing working defects, while integrating components to eliminate fitting requirements.
Implementation Method 1
Due to this, even when force in a radial direction is applied to the hole part in drawing and the like, the mandrel supports the inner part of the hole part to prevent the hole part from being crushed.
Data Source
AI summary
To provide a method of manufacturing a shaft for a steering device, the shaft including a spline shaft part to be coupled with an input shaft, a stopper part to be coupled with an output shaft, and an intermediate shaft part that couples the spline shaft part with the stopper part. The method includes: a step of forming a hole part recessed in an axial direction from one end of a pillar-shaped material by forging; and a step of pressing the material in which the hole part has been formed into a die to perform drawing in a radial direction on a portion of the material at which the stopper part is formed and prolonging a length along the axial direction of the hole part at the same time by forging.