Knocking Sensor Insulation with Polyphenylene Sulfide
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Knocking sensors face reduced insulation resistance at high temperatures, affecting their accuracy and frequency characteristics, due to the limitations of polyamide resin moldings used in existing designs.
Innovation Solution
The knocking sensor employs a resin molding made of polyphenylene sulfide or a copolymer of tetrafluoroethylene and ethylene, which maintains high surface resistivity at elevated temperatures, allowing for thinner insulating plates without compromising insulation properties, thus ensuring effective insulation and accurate knocking detection at temperatures of 150°C or more.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polyamide resin is used for the resin molding, then the knocking sensor can be manufactured with good moldability, but the insulation resistance is reduced at high temperatures of 150°C or more
Solution Approach 1:
The patent changes the material parameter of the resin molding from polyamide resin to polyphenylene sulfide or copolymer of tetrafluoroethylene and ethylene. This material substitution fundamentally alters the thermal and electrical properties, enabling the resin to maintain high surface resistivity (1.0×10^10Ω or more) at temperatures of 150°C or more, thereby resolving the insulation resistance degradation issue while preserving manufacturing capabilities
Solution Approach 2:
The patent employs specific resin materials (polyphenylene sulfide or copolymer of tetrafluoroethylene and ethylene) that possess both good moldability and superior high-temperature electrical insulation properties. These composite material selections provide a balanced solution that simultaneously addresses manufacturing requirements and high-temperature reliability requirements
2Measurement precision
If the thickness of insulating plates is reduced, then the frequency characteristics are improved, but the insulation resistance may be compromised
Solution Approach 1:
The patent changes the surface resistivity parameter of the resin molding material to 1.0×10^10Ω or more at 150°C, which compensates for the reduced insulation plate thickness. This material parameter change allows the insulating plates to be made thinner (0.05 mm to 0.50 mm) without compromising overall insulation performance, thereby improving frequency characteristics while maintaining adequate insulation resistance
Solution Approach 2:
The use of high-performance resin materials with superior electrical properties enables the design of thinner insulating structures. The resin molding material's high surface resistivity compensates for the reduced thickness, allowing optimization of frequency characteristics while maintaining insulation integrity
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 solution enhances the insulation characteristics and accuracy of knocking detection in high-temperature environments without disturbing the frequency characteristics, enabling reliable operation at temperatures up to 150°C or more.
Implementation Method 1
a piezoelectric element 150...an upper insulating plate 135 that electrically insulates the upper electrode plate 160 from the weight 170
Data Source
AI summary
There is provided a knocking sensor that has good insulation characteristics even at an operating temperature of 150° C. or more and is excellent in the accuracy of knocking detection. The knocking sensor 10 includes a sensor body 20 including: a metal shell 12 that includes a cylindrical portion 12a and a flange portion 12b positioned at one end of the cylindrical portion 12a and protruding outward in a radial direction; an annular piezoelectric element 15; upper and lower electrode plates 16 and 14 that are superimposed on upper and lower surfaces of the piezoelectric element 15; a weight 17 that is disposed so that the piezoelectric element 15 is interposed between the weight and the flange portion 12b; a lower insulating plate 13 that is disposed between the flange portion 12b and the lower electrode plate 14; and an upper insulating plate 13t that is disposed between the upper electrode plate 16 and the weight 17; and a resin molding 11 that covers the sensor body 20. Further, the thickness of each of the upper and lower insulating plates 16 and 14 is in the range of 0.05 mm to 0.50 mm, and the resin molding 11 is made of polyphenylene sulfide having good heat resistance.