Worm Wheel Electro-Deposition Machining
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Solution Overview
Problem
The existing manufacturing methods for worm gear reducers in electric power steering devices face challenges in ensuring sufficient contact area and durability due to the need for a larger hob cutter diameter to accommodate a larger lead angle, which increases manufacturing costs and reduces mechanical strength.
Innovation Solution
A manufacturing method using a machining worm with a tooth pitch and diameter matching the operational worm, coated with abrasive grains by electro-deposition, is employed to extend the contact area and ensure mechanical strength, allowing for a smaller machining worm diameter without compromising durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a larger hob cutter diameter is used to accommodate a larger lead angle, then the lead angle increases enabling reverse operation, but the mechanical strength of the hob cutter decreases and manufacturing costs increase
Solution Approach 1:
The patent replaces the conventional hob cutter machining method with an electro-deposition process. Instead of mechanically cutting teeth with a hob cutter, the invention deposits a tooth portion containing abrasive grains onto the worm shaft surface through electro-deposition, thereby avoiding the mechanical strength limitations of large-diameter hob cutters while achieving the required lead angle for reverse operation
Solution Approach 2:
The invention changes the fundamental parameter of tooth formation from mechanical cutting to electro-deposition. By controlling deposition parameters such as current density, deposition time, and electrolyte composition, the worm shaft teeth can be formed with precise geometry and appropriate hardness without being constrained by hob cutter mechanical strength limitations
2Adaptability or versatility
If a larger hob cutter diameter is used to accommodate a larger lead angle, then the lead angle increases enabling reverse operation, but manufacturing costs increase
Solution Approach 1:
The patent replaces the conventional hob cutter machining method with an electro-deposition process. Instead of mechanically cutting teeth with a hob cutter, the invention deposits a tooth portion containing abrasive grains onto the worm shaft surface through electro-deposition, thereby avoiding the mechanical strength limitations of large-diameter hob cutters while achieving the required lead angle for reverse operation
Solution Approach 2:
The electro-deposition process uses a relatively simple deposition setup compared to precision large-diameter hob cutter manufacturing. The tooth portion is deposited as a consumable layer containing abrasive grains, which can be renewed by re-deposition if worn, avoiding the need for expensive large-diameter hob cutters
3Adaptability or versatility
If the outer diameter of the worm is decreased to increase the lead angle, then reverse operation becomes possible, but the contact area of the tooth portion decreases
Solution Approach 1:
The patent creates a composite tooth portion by incorporating abrasive grains within the deposited material matrix. This composite structure allows the tooth portion to maintain small outer diameter for high lead angle while the abrasive grains provide enhanced contact area and load-bearing capacity, preventing the contact area reduction that would normally occur with smaller worm diameters
Solution Approach 2:
The electro-deposition process enables localized enhancement of the tooth portion properties. By controlling deposition parameters, the tooth portion can be formed with higher material density and embedded abrasive grains in the contact regions, concentrating the contact area enhancement where it is most needed while maintaining the overall small worm diameter
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 effectively increases the contact area and mechanical strength of the worm wheel, reducing sliding resistance and manufacturing costs while maintaining high operational efficiency.
Implementation Method 1
diameters of tip and root portions of the tooth of the machining worm are equal to or more than those of the operational worm and abrasive grains are provided on a surface of the machining worm by means of electro-deposition
Implementation Method 2
abrasive grains are provided on a surface of the machining worm by means of electro-deposition; rotating the machining worm and the worm wheel with meshing each other so as to machining the tooth portion of the worm wheel
Data Source
AI summary
A manufacturing method for a worm wheel, the worm wheel meshed with an operational worm at usage, has steps of preparing a worm wheel, in which at least a surface layer of a tooth portion is made of synthetic resin, preparing a machining worm, in which pitch of teeth of the machining worm in an axial direction thereof is the same as that of an operational worm, diameters of tip and root portions of the tooth of the machining worm are equal to or more than those of the operational worm and abrasive grains are provided on a surface of the machining worm by means of electro-deposition, disposing the machining worm in a twisting position relative to the worm wheel and rotating the machining worm and the worm wheel with meshing each other so as to machining the tooth portion of the worm wheel.