Sensor Mounting Structure Radial Force Shift for Thermal Loosening
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Solution Overview
Problem
Temperature sensors mounted to exhaust gas purifiers face loosening issues due to thermal stress caused by differences in thermal expansion coefficients between the sensor material and the mount body material, leading to reduced assembly efficiency and potential joint strength deformation.
Innovation Solution
A sensor design featuring a tubular rib with a protruding portion and a rotatable mounting member, where the contact position and pressing force are shifted radially outward to enhance the seal and reduce stress on the joint, using a flat and inclined surface configuration to concentrate the pressing force and prevent deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a temperature sensor is mounted to an exhaust gas purifier using a threaded portion, then the sensor can detect temperature, but thermal stress from temperature changes causes the threaded portion to loosen
Solution Approach 1:
The sensor mounting structure performs preliminary sealing and positioning actions through the rib's forward-facing surface contact with the mount body before the threaded portion is fully tightened. This preliminary action creates a stable base that prevents the threaded portion from loosening due to subsequent thermal expansion and contraction cycles.
Solution Approach 2:
The rib structure provides localized sealing and stress distribution at the forward-facing surface contact point with the mount body. This local quality enhancement at the sealing interface prevents uniform loosening of the entire threaded portion by concentrating the sealing function at a specific location that experiences thermal stress.
2Temperature
If a high heat resistant material is used for the temperature sensor to protect against thermal stress, then heat resistance is improved, but the difference in thermal expansion coefficient with the mount body increases causing the threaded portion to loosen more easily
Solution Approach 1:
The rib structure provides localized sealing and stress distribution at the forward-facing surface contact point with the mount body. This local quality enhancement at the sealing interface prevents uniform loosening of the entire threaded portion by concentrating the sealing function at a specific location that experiences thermal stress.
Solution Approach 2:
The sensor mounting structure performs preliminary sealing and positioning actions through the rib's forward-facing surface contact with the mount body before the threaded portion is fully tightened. This preliminary action creates a stable base that prevents subsequent loosening due to thermal expansion and contraction cycles.
3Reliability
If stress is applied to the tapered surface of the rib to tighten the threaded portion, then loosening is prevented, but the stress is transmitted to the tubular member causing reduction in joint strength or deformation
Solution Approach 1:
The sealing function is extracted from the tapered surface contact area and relocated to the rib's forward-facing surface. This extraction removes the harmful stress concentration from the tubular member joint area while maintaining the necessary tightening function through the threaded portion, thereby preserving joint strength.
Solution Approach 2:
The rib structure provides localized sealing and stress distribution at the forward-facing surface contact point with the mount body. This local quality enhancement at the sealing interface prevents uniform loosening of the entire threaded portion by concentrating the sealing function at a specific location that experiences thermal stress.
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 effectively restrains loosening of the threaded portion, maintains joint strength, and improves assembly efficiency without impairing workability, even under high-temperature conditions.
Implementation Method 1
thermal stress is applied to the threaded portion of the temperature sensor and the mounting hole of the mount body to thereby cause them to expand and contract
Data Source
AI summary
A sensor (200) includes a temperature sensitive element (203); a first tubular member (212); a tubular rib (240); a second tubular member (260); and a tubular mounting member (250) that surrounds the rib through the second tubular member, is rotatable with respect to the rib, and has a threaded portion (254). The rib includes a main body (243) and a protruding portion (242). A flat portion (244L) is formed on a rearward-facing surface of the protruding portion, and an inclined surface (242b) is formed radially outward of the flat portion. A forward-facing surface (250f) of the mounting member is in line contact with the inclined surface at a prescribed contact position (P), and an intersection (R) of the inclined surface and a perpendicular (M) thereto from a radially innermost point (Q) of a forward-facing surface (244f) of the protruding portion is located radially inward of the contact position.