Sensor Device Double Cover Flow Guide
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Solution Overview
Problem
Conventional sensor devices, particularly particulate matter (PM) sensors in exhaust gas purification systems, face challenges in detection sensitivity at low exhaust gas flow velocities and are prone to water condensation issues, leading to potential sensor element damage.
Innovation Solution
The sensor device incorporates a double-structured element cover with inner and outer covers, featuring guide members that direct exhaust gas flow to enhance detection sensitivity and prevent water condensation by positioning outer side holes closer to the tip end, forming specific flow passages, and using inclined guide members to maintain high flow velocity and reduce eddy currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-structured element cover is used, then the device complexity is reduced, but the detection sensitivity at low flow velocities deteriorates and water condensation issues occur
Solution Approach 1:
The element cover is divided into an inner cover and an outer cover as separate components. The inner cover contains the sensor element and forms a first flow passage, while the outer cover provides a second flow passage with guide members. This segmentation allows independent optimization of each cover's function, improving detection sensitivity while managing complexity through modular design.
Solution Approach 2:
The inner cover is nested within the outer cover, with the inner cover positioned inside the hollow interior of the outer cover. This nested configuration allows the dual-structured element cover to be integrated into the sensor device without significantly increasing overall size, while still providing the benefits of separate flow passages for improved detection performance.
2Reliability
If guide members are positioned closer to the tip end, then water condensation is prevented, but the device complexity increases
Solution Approach 1:
Guide members are strategically positioned only in specific locations on the outer cover where water condensation is most likely to occur. The guide members have inclined surfaces that direct gas flow locally to prevent condensation at critical areas, rather than requiring a complete redesign of the entire element cover structure.
3Measurement precision
If inclined guide members are used to maintain high flow velocity, then detection sensitivity improves, but the device complexity increases
Solution Approach 1:
The guide members are designed with specific inclination angles and dimensions to optimize gas flow velocity. By adjusting geometric parameters such as the inclination angle of the guide member surfaces and the spacing between guide members, the flow velocity can be maintained at optimal levels for detection sensitivity without requiring complex active control systems.
Data Source
AI summary
A sensor device includes an element cover at the tip end of a housing, retaining a sensor element. An outer cover is provided with outer side holes, with the tip position of the outer side holes being farther toward the tip end than is the tip position of an inner cover, and a first flow passage having a gas flow direction that is at right angles to the axial direction is formed at the inner side of the outer cover. An inner side hole in the inner cover is open to a second flow passage provided between the side surfaces of the inner cover and the outer cover, and a detection surface of the sensor element is located on an extension line in an extension direction of a guide member which extends obliquely into the interior of the inner cover from the tip-position edge of the inner side hole.