Capacitive Exhaust Gas Sensor Adapter Sleeve Design
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Solution Overview
Problem
Existing capacitive exhaust gas sensors face challenges in achieving high accuracy due to manufacturing tolerances, which affect the alignment and consistency of the anode and cathode sleeves, leading to deviations in the coaxiality and thus the precision of the measurement signals.
Innovation Solution
The sensor design incorporates an adapter sleeve connected to the anode conductor via an electrical insulator, allowing for decoupling of manufacturing tolerances and enabling precise coaxial alignment of the anode and cathode sleeves, with a brazing process and specific material selection to manage thermal expansion, ensuring an exact and constant air gap for improved measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the anode conductor is directly connected to the housing and cathode sleeve, then the device complexity is reduced, but the manufacturing precision and coaxiality alignment deteriorate due to accumulated tolerances
Solution Approach 1:
The sensor structure is segmented into multiple independent components: adapter sleeve, anode conductor, anode sleeve, housing, and cathode sleeve. Each component is manufactured separately with its own tolerance range, preventing the accumulation of tolerances that would occur in a direct connection design. The adapter sleeve acts as a reference element that decouples the tolerance chains between the anode conductor and the housing/cathode sleeve assembly.
Solution Approach 2:
The adapter sleeve serves as an intermediary component between the anode conductor and the housing/cathode sleeve assembly. It provides a stable reference surface and connection interface that mediates the alignment between components, ensuring coaxiality while allowing each component to be manufactured within standard tolerance ranges.
2Manufacturing precision
If high-precision direct connection methods are used, then the coaxiality alignment improves, but the ease of manufacture deteriorates due to stricter tolerance requirements
Solution Approach 1:
By segmenting the structure into multiple components with independent tolerance ranges, each component can be manufactured using standard precision methods without requiring ultra-precise machining. The adapter sleeve absorbs and decouples the tolerance accumulations, allowing easier manufacturing of individual parts.
Solution Approach 2:
The adapter sleeve is nested within the housing, and the anode conductor is nested within the adapter sleeve. This nested arrangement allows the adapter sleeve to provide a reference framework that guides the positioning of inner components, achieving high coaxiality through cumulative alignment rather than requiring each interface to be ultra-precise.
3Stability of the object's composition
If the anode and cathode sleeves are rigidly fixed together, then the structural stability improves, but the measurement precision deteriorates due to inability to compensate for thermal expansion differences
Solution Approach 1:
The connection between the housing and cathode sleeve is designed to allow controlled movement or adjustment in response to thermal expansion. The adapter sleeve material selection and connection design enable the structure to adapt to temperature changes, maintaining the air gap dimensions and coaxiality within acceptable ranges despite thermal effects.
Solution Approach 2:
The patent explicitly addresses thermal expansion by selecting adapter sleeve material with appropriate thermal expansion characteristics and designing connections that accommodate differential expansion between components. This allows the structure to maintain measurement precision across varying temperatures by compensating for thermal effects rather than resisting them rigidly.
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 design achieves a high-resolution, accurate measurement signal comparable to resistive sensors, reducing excessive deviation in coaxiality and maintaining measurement precision across varying temperatures, thereby enhancing the sensor's accuracy and reliability.
Implementation Method 1
The anode conductor is rigidly connected to the adapter sleeve by means of an electrical insulator
Implementation Method 2
the anode conductor and the insulator are connected to the adapter sleeve by means of a soldered connection. In particular, a brazing process is used with temperatures, for example, up to 950 °C
Implementation Method 3
The adapter sleeve, together with the anode conductor and the insulator, forms an assembly that can be connected to the separately manufactured housing during production. Thus, manufacturing tolerances that occur when connecting the anode conductor to the adapter sleeve can be compensated for when coupling the assembly to the housing
Data Source
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AI summary
The invention relates to a sensor (100) for a motor vehicle comprising: an anode conductor (101), an anode sleeve (102) which is connected to the anode conductor (101), an adapter sleeve (103), wherein the anode conductor (101) is rigidly connected by means of an electrical insulator (104) to the adapter sleeve (103), a housing (105), a connection (106) which connects the housing (105) and the adapter sleeve (103) to one another, a cathode sleeve (107) which is connected to the housing (105), wherein the anode sleeve (102) and the cathode sleeve (107) are arranged coaxially with respect to one another within the scope of the production tolerances.