Polyacetal Resin Insert Molded Body for Fuel Pump Connectors
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Solution Overview
Problem
Existing insert molded bodies for electrical connection connectors in fuel pumps face challenges in achieving high airtightness performance, particularly when using polyacetal resin members, and require complex manufacturing processes involving adhesives and sealants, leading to increased costs and potential air leakage issues.
Innovation Solution
A polyacetal resin composition with a specific formulation of 100 parts by mass of polyacetal resin and 30 to 150 parts by mass of thermoplastic polyester elastomer, combined with surface roughening of the metallic insert member to enhance adhesion, allowing direct joining without adhesives or sealants, resulting in a high airtightness insert molded body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a heat activatable adhesive is applied on the insert member surface and then thermoplastic resin is injection-molded, then integration between metal and resin is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent extracts and eliminates the adhesive layer from the manufacturing process. Instead of applying heat-activatable adhesive and then injection-molding, the invention uses a polyacetal resin composition that directly bonds to the metal insert member surface through chemical affinity, removing the intermediate adhesive step and simplifying the manufacturing process while maintaining reliable integration.
Solution Approach 2:
The patent changes the material parameter by using polyacetal resin composition instead of conventional thermoplastic resin. The polyacetal resin's chemical structure provides natural affinity for metal surfaces, enabling direct bonding without adhesives. This parameter change in resin type fundamentally alters the bonding mechanism from physical adhesion (requiring adhesives) to chemical affinity (direct bonding).
2Reliability
If surface treatment with alkaline/acidity solution and silane coupling agent is performed, then adhesion between metal and resin is improved, but manufacturing time and cost increase
Solution Approach 1:
The patent removes the multi-step surface treatment process (alkaline/acidity solution treatment followed by silane coupling agent application) and replaces it with direct bonding using polyacetal resin. The resin's inherent chemical affinity for metal surfaces eliminates the need for these time-consuming surface preparation steps while achieving equivalent or superior adhesion.
Solution Approach 2:
The polyacetal resin composition performs the bonding function self-service by utilizing its own chemical structure to bond directly to the metal insert member. Instead of requiring external surface treatment chemicals and coupling agents, the resin itself provides the bonding capability through its chemical affinity for metal surfaces, eliminating multiple processing steps.
3Reliability
If grooving is performed on the insert member surface, then airtightness at the joining interface is improved, but manufacturing complexity increases
Solution Approach 1:
The patent changes the bonding mechanism parameter from mechanical interlocking (requiring grooves and resin flow into grooves) to chemical bonding (direct molecular-level adhesion between polyacetal resin and metal surface). This parameter change eliminates the need for grooving while achieving superior airtightness through chemical affinity, reducing manufacturing complexity.
4Ease of manufacture
If conventional thermoplastic resin is used for fuel pump connector, then ease of manufacture is maintained, but airtightness performance is insufficient under fuel pressure
Solution Approach 1:
The patent changes the resin material parameter from conventional thermoplastic resin to polyacetal resin composition. The polyacetal resin provides superior chemical affinity for metal surfaces, creating a more reliable bond that maintains airtightness under fuel pressure. This material parameter change enhances both bonding reliability and airtightness performance while remaining compatible with standard injection molding processes.
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 solution provides a cost-effective and simplified manufacturing process for insert molded bodies with very high airtightness performance, as demonstrated by the absence of air-bubble leakage under pressure testing, while maintaining sufficient stiffness and fuel resistance.
Implementation Method 1
a thermoplastic polyester elastomer (B) having an amorphous structure
Implementation Method 2
a polyacetal resin composition including 100 parts by mass of a polyacetal resin (A) and 30 parts by mass or more and 150 parts by mass or less of a thermoplastic polyester elastomer (B)
Data Source
Figure 1A~1B
Figure 2
Figure 3A~3B
AI summary
To provide, easily and at low cost, an insert molded body which exhibits extremely high airtightness and has a polyacetal resin member serving as a substrate. The insert molded body 1 of the present invention is provided with an insert member 10 and a polyacetal resin member 20, wherein the insert member 10 and the polyacetal resin member 20 are joined directly rather than being joined via an adhesive layer, etc. Here, the polyacetal resin member 20 is a molded body of a polyacetal resin composition, said composition containing 100 parts by mass of (A) a polyacetal resin and 30-150 parts by mass of (B) a thermoplastic polyester elastomer. The insert member is preferably a metal member which has been subjected to a roughening treatment. Further, since the insert molded body 1 exhibits extremely high airtightness and the decrease of rigidity thereof caused by swelling, etc. due to a fuel oil is small, it is preferable that the insert molded body 1 be used as a component of an electrical connector for a fuel pump.