Sensor Element Cover Design for Gas Flow Velocity
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Solution Overview
Problem
Conventional sensor devices for detecting specific components in exhaust gas, such as particulate matter, face challenges with reduced detection sensitivity and output response due to low gas flow velocity, especially during engine startup, which can lead to particulate matter not reaching the detection section and potential sensor element cracking from moisture ingress.
Innovation Solution
The sensor device features a unique element cover configuration with a large clearance section and a small clearance section connected without a step, increasing gas flow velocity through the Venturi effect, and preventing moisture ingress by eliminating a gas flow hole in the outer cover's tip face, ensuring high flow velocity and reduced eddy currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional element cover with a single cover or simple double cover structure is used, then the structure is simple and easy to manufacture, but the gas flow velocity is reduced and eddy currents are generated, leading to reduced detection sensitivity and output response
Solution Approach 1:
The element cover is divided into an inner cover and an outer cover with a space between them, creating a segmented structure. This segmentation allows the gas flow to be guided more effectively through the detection section, increasing flow velocity and reducing eddy currents, thereby improving detection sensitivity without excessive complexity
Solution Approach 2:
The clearance between the inner and outer covers is designed with varying dimensions - larger at certain sections and smaller at others - to optimize gas flow characteristics locally. This local quality variation enhances flow velocity at the detection section while managing overall structural complexity
2Reliability
If the element cover structure is simplified to reduce complexity, then manufacturing is easier, but gas flow velocity decreases and moisture can ingress through gas flow holes, causing sensor element cracking
Solution Approach 1:
The gas flow hole in the tip face of the outer cover is eliminated (taken out) from the design. Instead, gas enters through side holes in the outer cover and flows through the space between the covers to reach the detection section, preventing moisture ingress that would cause cracking while maintaining structural reliability
Solution Approach 2:
The space between the inner and outer covers acts as an intermediary flow path, guiding gas flow away from direct exposure to moisture-prone areas while maintaining detection functionality. This intermediary structure protects the sensor element from moisture-related damage
3Productivity
If the gas flow velocity is increased to improve detection sensitivity, then output response improves, but the risk of moisture ingress and sensor element cracking increases
Solution Approach 1:
Instead of increasing gas flow velocity directly through the tip face (which would cause moisture ingress), the design inverts the approach by entering gas through side holes and guiding it through the inter-cover space. This achieves high flow velocity for improved output response while preventing moisture-related harmful effects
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 sensitivity and output response by maintaining high gas flow velocity to the detection section, even at low flow velocities, while preventing water-related cracking issues, thereby improving the overall performance of the sensor device.
Implementation Method 1
The sensor device features a unique element cover configuration with a large clearance section and a small clearance section connected without a step, increasing gas flow velocity through the Venturi effect
Data Source
AI summary
A sensor device is equipped with a housing having an element cover retaining a sensor element such that a detection section of the sensor element is positioned at the tip end of the sensor element. The element cover includes an inner cover provided with inner side holes and an inner tip face hole respectively provided therein, and an outer cover provided with outer side holes in a side thereof, with the tip position of the outer side holes located closer to the tip end than is the tip position of the inner cover. Between the outer surface of the inner cover and the inner surface of the outer cover there is a large clearance section at the tip end and a small clearance section at the base end, providing a flow path that is shaped for connecting the large clearance section and the small clearance section without a step.