Gear Sleeve Adhesion via Primer Layer and Preheating
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Solution Overview
Problem
The existing manufacturing methods for gear components in electric power steering systems face challenges in enhancing adhesive strength between the sleeve and resin member without voids, particularly when using high molecular weight thermoplastic resins, which are prone to displacement due to radial forces, leading to inadequate durability and increased energy consumption during post-curing processes.
Innovation Solution
A method involving the formation of a primer layer on the sleeve using a thermoplastic resin-based adhesive with a melting point lower than the resin member, applied via electrostatic spraying and heated to flow and adhere before injection molding, allowing for enhanced adhesion without post-curing and simplifying the mold structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high molecular weight thermoplastic resin is used to ensure durability, then the gear durability life is improved, but the resin is prone to entrained voids during injection molding and may not conform properly to the sleeve recesses and protrusions
Solution Approach 1:
The sleeve is preheated before injection molding to delay solidification of the high molecular weight thermoplastic resin, allowing sufficient time for the resin to properly conform to the recesses and protrusions on the sleeve surface, thereby preventing entrained voids while maintaining durability
Solution Approach 2:
The temperature parameter of the sleeve is changed by applying heat before injection molding, which alters the viscosity characteristics of the thermoplastic resin during molding, enabling proper flow and conformance without void formation
2Manufacturing precision
If the sleeve is preheated to suppress voids, then the resin conformance is improved, but the adhesive strength fails to be enhanced because coupling agents are decomposed and inactivated
Solution Approach 1:
The coupling agent application step is removed from the process sequence, eliminating the problem of coupling agent decomposition during preheating while still achieving void-free molding through sleeve preheating alone
Solution Approach 2:
The sleeve surface itself acts as an intermediary between the thermoplastic resin and the metal core, using surface recesses and protrusions combined with thermal preheating to achieve both proper conformance and adequate adhesion without requiring additional coupling agents
3Strength
If a thermosetting resin or high heat resistance thermoplastic resin is applied as adhesive before preheating, then adhesion strength should be enhanced, but the adhesive undergoes thermosetting reaction or loses adhesiveness during preheating
Solution Approach 1:
Instead of using expensive heat-resistant adhesives with complex curing requirements, the invention uses the inherent mechanical interlocking through recesses and protrusions combined with simple thermal preheating, eliminating the need for adhesive curing steps and reducing process complexity
4Weight of moving object
If the resin member is formed without fiber reinforcement to reduce weight, then the weight is reduced, but the durability life becomes insufficient and the resin member may be damaged by radial forces
Solution Approach 1:
The invention creates a composite structure by integrally molding the thermoplastic resin over the metal sleeve, forming a unified resin member-sleeve assembly where the metal sleeve provides structural support and the resin provides functional teeth and surface properties, achieving both weight reduction and enhanced durability
5Strength
If post-curing is performed to enhance adhesive strength, then the adhesion is improved, but the manufacturing energy increases and the demand for weight reduction is not satisfied
Solution Approach 1:
The adhesive bonding action is performed preliminarily during the injection molding process itself through the preheated sleeve and proper resin flow, eliminating the need for separate post-curing operations and reducing total manufacturing energy consumption
Solution Approach 2:
The adhesive bonding function is merged with the injection molding process by using the molding conditions themselves to achieve proper adhesion, combining multiple functions into a single manufacturing step and eliminating additional energy-intensive curing 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
This approach significantly improves the axial pull-out and radial tensile load ratios, effectively preventing resin member displacement and enhancing the durability life of the gear while reducing manufacturing energy and environmental impact.
Implementation Method 1
heated to flow and adhere before injection molding
Implementation Method 2
heated to flow and adhere
Implementation Method 3
shrinkage of the injection-molded resin member, that is, clinging of the resin member
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3
AI summary
Over an outer peripheral surface of a sleeve (3), a primer layer (2) is formed that is a thermoplastic resin-based adhesive thermally melted at a temperature lower than a melting point of a thermoplastic resin formed into a resin member to exhibit adhesiveness. With the sleeve (3) preheated, a thermoplastic resin to be formed into the resin member (5) is annularly injection-molded over an outer periphery of the sleeve (3).