Gas Sensor Insulator With Segmented Through-Holes
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Solution Overview
Problem
Gas sensors measuring exhaust gas from internal combustion engines face challenges with dew condensation causing leakage current, which affects measurement accuracy, especially when measuring infinitesimally small NOx gas concentrations due to incomplete sealing and temperature fluctuations.
Innovation Solution
A gas sensor design with a contact-spring insulator featuring lead-insertion-hole protrusions and through-holes that isolate connecting terminals and contact springs, preventing dew condensation water from spreading and minimizing leakage current by directing it into recesses and outer peripheral surfaces, ensuring the chambers remain isolated and reducing the risk of electrical noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the gas sensor is equipped with inlet holes and filter to admit reference air, then the sensor can obtain reference gas for measurement, but water vapor can enter the lead cover and cause leakage current
Solution Approach 1:
The lead cover internal space is segmented into multiple isolated chambers (first chamber for connecting terminals, second chamber for contact springs, third chamber for sensor device) using partition walls. This segmentation prevents water vapor that enters through inlet holes from spreading across all components, isolating the harm to specific chambers and preventing leakage current between electrically connected components.
Solution Approach 2:
Partition walls act as intermediary structures between chambers. These walls with through-holes allow controlled gas flow while physically blocking water vapor accumulation and spread. The intermediary structure enables reference air to reach the sensor while preventing harmful water vapor from causing electrical leakage.
2Reliability
If the sealing mechanism is made tighter to prevent exhaust gas entry, then the lead cover sealing is improved, but complete hermetic sealing becomes difficult and water vapor condensation risk increases
Solution Approach 1:
Instead of attempting complete hermetic sealing of the entire lead cover, the invention segments the internal space into isolated chambers. This allows the sealing mechanism to focus on preventing exhaust gas entry while the segmentation prevents water vapor condensation from affecting electrical components, even if some water vapor enters through imperfect seals.
Solution Approach 2:
The harmful effect of water vapor condensation is extracted and isolated into specific chambers away from electrical components. By separating the condensation-prone areas from sensitive electrical parts through partition walls, the system tolerates imperfect sealing without suffering from leakage current.
3Volume of moving object
If contact springs and connecting terminals are placed close together for compact design, then the device size is reduced, but dew condensation water can simultaneously touch both causing leakage current
Solution Approach 1:
The lead cover internal volume is segmented into separate chambers for connecting terminals and contact springs using partition walls. This segmentation maintains compact overall size while preventing water droplets from simultaneously contacting both electrical components, as they are physically isolated in different chambers.
Solution Approach 2:
The problem of spatial proximity causing leakage current is solved by adding a dimensional barrier (partition wall) between components. Instead of increasing distance in the same space, the invention uses a third dimension (the partition wall structure) to separate components while maintaining compact footprint.
4Measurement precision
If the gas sensor operates at high temperature to prevent water condensation, then measurement accuracy is maintained, but temperature fluctuations cause water vapor to condense when temperature drops
Solution Approach 1:
The sensor device is isolated in a separate chamber from the lead cover internal space where temperature fluctuations occur. This segmentation allows the sensor to maintain stable operating temperature while the lead cover experiences external temperature changes, preventing condensation from affecting measurement accuracy.
Solution Approach 2:
Partition walls with controlled through-holes act as intermediaries that allow thermal isolation between the sensor chamber and the lead cover interior. This intermediary structure enables the sensor to maintain stable temperature for accurate measurement while the external lead cover handles temperature fluctuations without causing condensation on sensitive components.
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 design effectively minimizes leakage current and enhances measurement accuracy by preventing dew condensation from interfering with electrical connections, maintaining stable operation even under varying temperature conditions.
Implementation Method 1
water vapor, having entered the lead cover, is drained without being condensed along the same path as when it enters the lead cover. A change in temperature of the gas sensor arising from splashing with rain, however, may cause the water vapor in the lead cover to become liquid.
Data Source
AI summary
A gas sensor is provided which includes a sensor device, a plurality of contact springs, an insulator, a plurality of connecting terminals, and a lead cover. The insulator has an end surface which faces the connecting terminals and also includes as many protrusions as the contact springs. The insulator also has formed therein holding holes in which the contact springs are disposed. Each of the protrusions has formed therein a through-hole which communicates between an end surface of the protrusion and one of the holding holes. The through-holes are discrete from each other and formed one in each of the protrusions. This minimizes a risk of occurrence of leakage current between the contact springs or the connecting terminals arising from dew condensation and ensures a high degree of measurement accuracy of the gas sensor.