Glow Plug Sensor Attachment Structure for Stable Combustion Pressure Measurement
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Solution Overview
Problem
The integration of a combustion pressure sensor with a glow plug in internal combustion engines faces challenges in maintaining the stability of sensitivity and linearity of output due to variations in the contact area between the tapered contact surface and seat surface, which are affected by axial force and combustion pressure, leading to potential measurement errors.
Innovation Solution
The attachment structure of the glow plug with a combustion pressure sensor includes a recessed portion in the seat facing portion, which is axially recessed and non-contact with the seat portion, ensuring a constant contact area regardless of axial force variations, thereby stabilizing the rigidity and sensitivity of the sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the contact area between the tapered contact surface and seat surface is increased to improve sensor sensitivity, then the measurement precision is improved, but the contact area varies with axial force leading to instability in sensitivity
Solution Approach 1:
The invention changes the geometric parameters of the seat facing portion by introducing a recessed portion that axially recesses from the seat facing portion. This geometric modification ensures that the contact area between the tapered contact surface and seat surface remains constant regardless of axial force variations, thereby maintaining stable sensor sensitivity while preserving measurement precision
Solution Approach 2:
The seat facing portion is segmented into different regions: a contact region with the tapered contact surface and a recessed portion that is axially recessed. This segmentation allows the contact area to be isolated and controlled independently from axial force variations, stabilizing the sensitivity parameter
2Measurement precision
If the contact area between the tapered contact surface and seat surface is increased to improve sensor linearity, then the measurement precision is improved, but the contact area varies with combustion pressure leading to instability in linearity
Solution Approach 1:
The recessed portion in the seat facing portion modifies the contact geometry such that the contact area remains invariant under combustion pressure variations. This parameter change ensures stable linearity of the sensor output while maintaining the improved measurement precision that results from adequate contact area
Solution Approach 2:
By segmenting the seat facing portion into a contact region and an axially recessed portion, the invention isolates the contact area from combustion pressure effects, thereby stabilizing the linearity parameter while preserving measurement precision
3Reliability
If the axial force on the glow plug is increased to improve sealing between the seat facing portion and seat portion, then the reliability is improved, but the contact area varies leading to measurement errors
Solution Approach 1:
The invention introduces a recessed portion that axially recesses from the seat facing portion, creating a geometric constraint that maintains constant contact area between the tapered contact surface and seat surface. This parameter change allows sealing to be achieved through the tapered geometry itself without relying on high axial force, thereby preventing measurement errors while maintaining reliability
Solution Approach 2:
The seat facing portion is divided into a contact region that provides sealing through tapered surface contact and an axially recessed portion that prevents axial force from varying the contact area. This segmentation enables sealing functionality to be decoupled from contact area stability, allowing reliable sealing without measurement errors
Data Source
AI summary
On an inner wall surface of a plug hole, an internal thread portion and a seat portion are formed. The seat portion has a tapered seat surface. A glow plug with a combustion pressure sensor includes a housing, a glow heater, a load transfer member, and a pressure detector. The housing has an external thread and a seat facing portion. The seat facing portion has a tapered contact surface in surface contact with the tapered seat surface. A recessed portion recessed to be in non-contact with the seat portion is formed annularly about a central axis of the housing.