Combustion Pressure Sensor Welding Structure for Uniform Sensitivity
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Solution Overview
Problem
Conventional combustion pressure sensors face challenges in achieving uniformity in the depth of the joint portion due to thermal inertia, leading to variations in the effective pressure reception radius and sensitivity, which affects detection accuracy.
Innovation Solution
A combustion pressure sensor design with a predetermined clearance portion and a limited depth of welding, where the joint surfaces are planarly contacted and welded, ensuring a consistent welding depth and reducing sensitivity variations by containing weld spatters within the clearance area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If welding is performed to join the pressure reception member and case member, then the joint strength is improved, but the uniformity of welding depth deteriorates due to thermal inertia
Solution Approach 1:
A groove is formed in advance on the pressure reception member at the welding position. This preliminary structural preparation guides the welding process to achieve uniform welding depth throughout the joint circumference, eliminating the thermal inertia problem that causes non-uniform welding depth in conventional continuous welding.
Solution Approach 2:
The welding is divided into multiple discrete welding positions around the joint circumference, with grooves formed at each position. Welding is performed sequentially at these segmented positions rather than continuous welding, which allows thermal inertia to be reset between positions and ensures uniform welding depth.
2Measurement precision
If the effective pressure reception radius is increased to improve sensitivity, then the detection accuracy is improved, but the variation in sensitivity increases due to welding non-uniformity
Solution Approach 1:
The groove is formed in advance to define the exact welding position and depth. This preliminary action ensures that the pressure reception member's effective pressure reception radius remains consistent across all welding positions, eliminating sensitivity variations while maintaining high detection accuracy.
Solution Approach 2:
The groove structure creates a mechanical constraint that ensures uniform welding depth, which in turn ensures uniform effective pressure reception radius of the diaphragm. This uniformity eliminates sensitivity variations and improves reliability of detection accuracy.
3Strength
If welding depth is increased to improve joint strength, then the joint strength is improved, but the effective pressure reception radius varies
Solution Approach 1:
The groove is formed in advance with the desired depth and dimensions. This preliminary action sets a physical limit on welding depth, ensuring that even with increased welding intensity for stronger joints, the welding depth remains uniform and does not vary the effective pressure reception radius.
Solution Approach 2:
The groove provides localized geometric constraints at the welding position, ensuring that welding depth is controlled locally at each segmented position. This local quality control ensures uniform effective pressure reception radius while allowing sufficient joint strength through proper groove design.
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 results in a highly accurate and reliable combustion pressure sensor with reduced sensitivity displacement and improved manufacturing ease, capable of consistent performance across various applications, including internal combustion engines and functional components like injectors and spark plugs.
Implementation Method 1
a piezoelectric element which converts a pressing force based on the combustion pressure into a signal
Implementation Method 2
a welding portion in which the joint surfaces are joined to each other
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
When a combustion pressure sensor (5, 5A...) is formed that includes at least: a case member (31...) which has a joint surface (31a...) on the side of a tip end and in which an opening portion is provided; a joint surface (41a...) which is brought into planar contact with the joint surface (31a...) of the case member (31...) so as to block the opening portion; a pressure reception member (40 ...) on which a combustion pressure acts; a welding portion (J2...) in which the joint surfaces (31a and 41a...) are joined to each other; and a piezoelectric element (10...) which is stored in the case member (31 ...) and converts a pressing force based on the combustion pressure transmitted from the pressure reception member (40...) into a signal, on the side of one edge side in at least the one joint surface (41a...), the one joint surface (41a...) is limited to a given depth of welding (t...) from the other edge side, a predetermined clearance portion (90...) is provided so as to form a predetermined gap with the opposite other joint surface (31a...) and a welding portion (J2...) is provided which includes at least all the limited joint surface (41a...) from the other edge side in the one joint surface (41a...).