Pressure Sensor Bonding Structure Prevents Adhesive Creep
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Solution Overview
Problem
Existing pressure sensors with capillaries inserted into pressure transmission holes face issues where adhesive creep due to capillary action blocks the pressure transmission path, leading to inaccurate measurements and degradation of adhesive strength.
Innovation Solution
A pressure sensor design featuring a sensor diaphragm with a plate shape, a pressure-chamber defining member with a recess and countersink, and a connecting pipe bonded without adhesive at its first end portion, creating a space that prevents capillary action and maintains a high-strength bonded structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesive is used to bond the connecting pipe to the pressure transmission hole, then bonding strength is improved, but capillary action causes adhesive to creep up and block the pressure transmission path
Solution Approach 1:
The patent applies local quality by creating a countersink with a larger diameter at the bonding interface, while maintaining a smaller diameter at the opening to prevent adhesive creep. This localized geometric variation allows adhesive to be present where needed (at the bonding interface) while preventing it from migrating into the pressure transmission path.
Solution Approach 2:
The pressure transmission hole is segmented into two distinct regions: a countersink portion for bonding and a pressure transmission portion for fluid flow. This segmentation separates the bonding function from the pressure transmission function, allowing each to be optimized independently without interference.
2Reliability
If gap between hole wall surface and connecting pipe is expanded to prevent capillary action, then adhesive creep is prevented, but adhesive layer thickness increases and bonding strength degrades
Solution Approach 1:
The countersink creates a localized region with different geometric properties than the main hole. The larger diameter in the countersink region prevents capillary action and adhesive creep, while the smaller diameter at the opening maintains effective bonding contact, thus resolving the contradiction between preventing creep and maintaining bonding strength.
Solution Approach 2:
The countersink acts as an intermediary structure between the connecting pipe and the pressure transmission path. It provides a transition zone that controls adhesive behavior, allowing the adhesive layer to be thick enough for strong bonding while preventing it from migrating into the pressure transmission path.
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 design secures the pressure transmission path while ensuring a high-strength bonded structure, preventing adhesive blockage and maintaining accurate pressure measurement.
Implementation Method 1
the connecting pipe being exposed to the recess and bonded to the hole with an adhesive
Implementation Method 2
a capillary action may occur to allow the adhesive to creep up in the pressure transmission hole
Data Source
AI summary
A pressure sensor includes a sensor diaphragm, a pressure-chamber defining member joined to a sensor diaphragm, the pressure-chamber defining member including a recess and a through hole that is open in the recess, the recess having an opening closed by the sensor diaphragm, a connecting pipe having a first end portion inserted into the through hole while being exposed to the recess and bonded to the hole with an adhesive, and a pressure transmission medium filled in the recess and the connecting pipe. A space is disposed around the first end portion of the connecting pipe, and the adhesive is not disposed at the first end portion of the connecting pipe.