MAP Sensor Encapsulation Using Self-Levelling Adhesive
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Solution Overview
Problem
Current manifold absolute pressure (MAP) sensor assemblies in internal combustion engines require two different encapsulation materials for accurate pressure measurement, leading to complex and costly assembly processes and potential inaccuracies due to the need for precise coverage of the pressure-sensing surface.
Innovation Solution
A simplified MAP sensor assembly using a single encapsulation material with controlled viscosity, allowing direct exposure of the pressure-sensing surface to air, eliminating the need for a foam and simplifying the assembly process while ensuring accurate pressure measurement by using a self-levelling adhesive with a viscosity range of 70,000-90,000 centipoise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two different encapsulation materials are used to fill the space between the external housing unit and sensor unit, then the pressure-sensing surface can be protected while maintaining air communication, but the assembly process becomes complex and costly
Solution Approach 1:
The patent combines the functions of two separate encapsulation materials into a single material system. The lower viscosity material provides both the air communication pathway and the protective encapsulation, eliminating the need for a separate foam layer and high viscosity material layer, thus simplifying the assembly process while maintaining measurement accuracy
Solution Approach 2:
The encapsulation material is applied with spatially varying properties: a first portion with lower viscosity near the pressure-sensing surface to maintain air communication, and a second portion with higher viscosity in the surrounding areas for protective encapsulation. This local differentiation allows a single material to fulfill multiple functions
2Ease of manufacture
If foam material is used to cover the sensor unit, then the sensing element remains in communication with air, but the assembly requires precise application to avoid covering the pressure-sensing surface
Solution Approach 1:
The patent changes the viscosity parameter of the encapsulation material to achieve self-regulating behavior. The material has a viscosity range (70,000-90,000 centipoise) that prevents it from flowing onto the pressure-sensing surface while still allowing air communication, eliminating the need for precise manual application and reducing manufacturing precision requirements
3Device complexity
If a single encapsulation material is used, then assembly is simplified and costs are reduced, but the material must be carefully selected to maintain air communication with the pressure-sensing surface
Solution Approach 1:
The patent specifies a precise viscosity range (70,000-90,000 centipoise) for the single encapsulation material to ensure it maintains air communication pathways while providing adequate encapsulation. This parameter control allows a single material to replace multiple materials without sacrificing measurement reliability
Solution Approach 2:
The encapsulation material acts as an intermediary substance that bridges the protective function and the air communication function. By carefully selecting its viscosity properties, it mediates between the need to protect the sensor unit and the need to maintain air pathways to the pressure-sensing surface
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 assembly complexity and costs, enhances measurement accuracy by maintaining direct air communication with the pressure-sensing surface, and ensures reliable operation by preventing the encapsulation material from covering the sensitive area.
Implementation Method 1
using a self-levelling adhesive with a viscosity range of 70,000-90,000 centipoise
Data Source
AI summary
A pressure sensor assembly includes an external housing unit; a sensor unit received within the external housing unit, the external housing unit has an external surface including a mounting surface; a sensing element mounted within the sensor unit and including a pressure-sensing surface; a substrate upon which the mounting surface is mounted; an air passage to enable air to impinge on the sensing element; and a filling passage, separate from the air flow passage, for the introduction of an encapsulation material onto the sensor unit, during assembly. The encapsulation material covers at least a part of the external surface of the sensor unit but does not cover the pressure-sensing surface of the sensing element which remains directly exposed to air within the air passage.