Gas Sensor Inner Cover Vent Positioning for Airtightness
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Solution Overview
Problem
Existing gas sensors in internal combustion engines face accuracy issues due to air leakage at the seal portion between the sensor element and the housing, leading to incorrect oxygen concentration measurements and erroneous operation of the control system.
Innovation Solution
The gas sensor design includes a sensor element with a solid electrolyte body and measurement electrodes, housed within a structure with an inner and outer cover, where the axial distance from the base end of the internal space to the inner vent hole is between 0.2L and 0.65L, effectively preventing air from reaching the measurement electrode and improving airtightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sealing member filled with talc is provided between the sensor element and the housing to ensure airtightness, then the airtightness of the seal portion is improved, but air leakage still occurs and oxygen concentration measurement accuracy deteriorates
Solution Approach 1:
The element cover is divided into an inner cover and an outer cover, creating a dual-cover structure. The inner cover specifically covers the tip-end portion of the sensor element, while the outer cover covers the inner cover, forming a segmented protective structure that addresses air leakage at different locations
Solution Approach 2:
The inner cover acts as an intermediary component between the sensor element and the outer cover. It specifically addresses the air leakage path at the tip-end portion by providing an additional sealing layer and structural barrier, preventing atmospheric air from penetrating into the measurement region
2Measurement precision
If the airtightness is completely prevented, then measurement accuracy is improved, but this is difficult to achieve with conventional sealing methods
Solution Approach 1:
The inner cover is designed to preemptively block air leakage paths before atmospheric air can reach the sensor element. By positioning the inner cover at the tip-end portion and creating the dual-cover structure, the system establishes a preliminary barrier that prevents air from penetrating into the measurement region, ensuring accurate detection from the outset
Solution Approach 2:
The dual-cover structure with the inner cover provides a cushioning effect against air leakage. The inner cover absorbs and blocks the air leakage that occurs at the seal portion between the sensor element and housing, preventing this leakage from affecting the measurement electrode and reference electrode
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 configuration enhances detection accuracy by minimizing the influence of air leakage, ensuring precise oxygen concentration measurement and reducing deviations in stoichiometric air-fuel ratios.
Implementation Method 1
a sensor element including a solid electrolyte body having oxygen ion conductivity
Data Source
AI summary
A gas sensor is provided with: a sensor element having a solid electrolyte body, a measurement electrode and a reference electrode; a housing into which the sensor element is inserted; and an element cover arranged at the tip-end side of the housing. The element cover has an inner cover arranged so as to cover the tip-end portion of the sensor element from outside, and an outer cover arranged so as to cover the inner cover from outside. When L is defined as an axial distance from a base end of an internal space of the inner cover to the base end of the measurement electrode, an axial distance M from the base end of the internal space of the inner cover to the base end of an inner vent hole positioned in the most base-end side among the inner vent holes provided to the inner cover is 0.2L to 0.65L.