Gas Sensor Weld Joint Corrosion Prevention
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Solution Overview
Problem
Conventional laser weld joints in gas sensors are susceptible to corrosion due to water penetration and accumulation, which can lead to prolonged exposure and damage, especially in automotive exhaust gas sensors.
Innovation Solution
A corrosion-resistant weld joint structure is achieved by forming a larger penetration depth weld joint that extends from the front end of the protection cover to the metal shell, ensuring the weld joint is exposed to the atmosphere for easy vaporization of water and preventing long-term contact with moisture, while also allowing for easy positioning and fixing during laser welding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the laser weld joint is formed at a position axially away from the front edge of the protection cover, then the welding process is easier to implement, but water penetrates into the narrow gap between the metal shell and protection cover causing corrosion of the weld joint
Solution Approach 1:
Instead of positioning the weld joint away from the front edge for easier manufacturing, the patent inverts the approach by extending the weld joint to reach the front edge of the protection cover. This reversal of the conventional welding position eliminates the narrow open gap that causes water accumulation, thereby preventing corrosion while maintaining manufacturing feasibility through proper process control
Solution Approach 2:
The patent extracts or eliminates the harmful narrow open gap between the protection cover and metal shell by extending the weld joint to the front edge. This removal of the gap prevents water from penetrating and accumulating in the space, directly addressing the corrosion problem without compromising the welding process
2Reliability
If the weld joint extends to the front end of the protection cover, then water penetration and accumulation are prevented, but positioning and fixing during welding becomes more difficult
Solution Approach 1:
The patent applies preliminary action by providing positioning and fixing structures on both the metal shell and protection cover before the welding process. These pre-installed positioning features facilitate accurate alignment and secure fixing of the components, making the extended weld joint to the front edge feasible without compromising manufacturing ease
Solution Approach 2:
The positioning and fixing structures act as intermediaries between the metal shell and protection cover, enabling precise alignment and stable positioning during the welding process. These intermediary elements make it possible to extend the weld joint to the front edge while maintaining ease of manufacturing
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
The solution effectively prevents water from penetrating and accumulating in the gap between the metal shell and protection cover, thereby protecting the weld joint from corrosion and ensuring the gas sensor's reliability and longevity.
Implementation Method 1
irradiating a laser beam from the outside of the protection cover to form a laser weld joint between the front end portion of the protection cover and the rear end portion of the metal shell
Implementation Method 2
water penetrates into the narrow gap between the metal shell and the protection cover by capillary action
Data Source
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AI summary
There is provided a gas sensor, which includes a sensor element extending axially of the gas sensor and having a gas sensing portion at a front end thereof and an electrode portion at a rear end thereof, a cylindrical metal shell retaining therein the sensor element with the gas sensing portion and the electrode portion protruding from front and rear ends of the metal shell, respectively, and having a flange portion and a rear end portion located on a rear side of the flange portion, a cylindrical protection cover having a front end fitted onto the rear end portion of the metal shell so as to cover the electrode portion and a weld joint through which the entire circumference of the front end of the protection cover is joined through the metal shell. The weld joint extends from an end face of the protection cover to the metal shell.