Hollow Steering Shaft Forging 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 forging to form a spline shaft part and an intermediate shaft part from a single pillar-shaped material, where a hole is recessed and elongated axially, reducing the need for cutting and allowing for deep hole formation without cutting, thereby reducing weight and improving torque transmission reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If multiple shaft parts are coupled by press-fitting to form a hollow steering shaft, 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 parts (first shaft and second shaft) into a single integrated shaft component. The hollow structure is formed directly during forging by creating a cavity within the single piece, eliminating the need for separate shaft components and their associated press-fitting assembly processes. This reduces component count while maintaining the weight reduction benefit of the hollow design.
2Weight of moving object
If multiple shaft parts are coupled by press-fitting, then the weight of the steering shaft is reduced, but production cost increases due to fitting processes
Solution Approach 1:
The patent combines the hollow structure formation with the single-piece forging process. A mandrel is used during forging to create the hollow cavity directly within the single shaft component, eliminating subsequent fitting operations. This integration of hollow formation into the primary manufacturing process reduces production steps and associated costs while achieving the weight reduction goal.
3Weight of moving object
If deep hole is formed by cutting using a drill, then the weight of the steering shaft is reduced, but the time required for cutting is prolonged and production cost increases
Solution Approach 1:
The patent performs the hollow structure formation during the initial forging process rather than as a subsequent operation. The mandrel is positioned and the cavity is formed during forging, before any cutting or drilling operations. This preliminary action eliminates the need for time-consuming deep hole drilling operations while achieving the same weight reduction effect.
4Weight of moving object
If cutting is performed on a pillar-shaped material to form deep holes, then the weight of the steering shaft is reduced, but position accuracy of the hole decreases and working defects occur due to cutting chips
Solution Approach 1:
The patent forms the hollow cavity structure during the forging process itself, using a mandrel to define the cavity shape and position before any cutting operations. This ensures high position accuracy is achieved during the forming stage when the material is plastic and can be precisely shaped, avoiding the position accuracy degradation that occurs with subsequent drilling of deep holes in rigid material.
Solution Approach 2:
The patent converts the potential harm of cutting chips and working defects into a benefit by avoiding cutting operations entirely for the hollow structure formation. Instead of using cutting (which generates chips and defects), the patent uses forging with a mandrel, which produces clean surfaces and precise geometry without generating harmful cutting chips, thereby improving manufacturing precision.
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 a lower cost by eliminating the need for multiple components and cutting processes, while enhancing the strength and accuracy of the shaft.
Implementation Method 1
the mandrel supports the inner part of the hole part to prevent the hole part from being crushed
Implementation Method 2
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 spline shaft part and the intermediate shaft part are formed
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 spline shaft part and the intermediate shaft part are formed, and prolonging a length along the axial direction of the hole part at the same time by forging.