Piezo Sensor Mounting in Fuel Injector
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Solution Overview
Problem
Conventional injectors with pressure sensors attached using adhesive connections face issues with tensile stress, durability, and signal measurement potential due to inhomogeneous strain conditions, especially under varying temperatures and pressures.
Innovation Solution
A sensor is prestressed between a recess aligned with the high-pressure line and a cover in the injector body, eliminating the need for adhesives and ensuring the sensor is axially loaded with pressure fluctuations, with thermal expansion coefficient matching for temperature compensation, and a pressure distributor for enhanced signal transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the sensor is attached to the injector body using adhesive connection, then the sensor can be mounted in the recess, but the sensor experiences high tensile stress and reduced durability under pressure fluctuations and temperature variations
Solution Approach 1:
The patent replaces the adhesive connection system with a mechanical prestressing system. The sensor is mounted in a recess and prestressed axially between the injector body and a cover, eliminating the need for adhesives. This mechanical prestressing system better withstands pressure fluctuations and temperature variations, significantly improving sensor durability and reliability under harsh operating conditions.
2Ease of manufacture
If the sensor is attached using adhesive connection, then the sensor can be installed, but the adhesive introduces inhomogeneous strain conditions that reduce signal measurement potential
Solution Approach 1:
The patent replaces the adhesive bonding system with a direct mechanical prestressing system. The sensor is axially prestressed between the injector body and cover, creating homogeneous strain conditions that fully exploit the sensor's measurement potential. This eliminates the inhomogeneous strain distribution caused by adhesive layers, thereby improving signal quality and measurement precision.
3Ease of manufacture
If conventional adhesive attachment is used, then the sensor can be fixed, but the adhesive degrades over time under extreme temperatures between -40°C and +160°C, reducing system robustness
Solution Approach 1:
The patent replaces the temperature-sensitive adhesive system with a robust mechanical prestressing system. The sensor is axially prestressed between the injector body and a cover that is welded to the injector body. This mechanical connection method is far more resistant to extreme temperature variations (-40°C to +160°C) and maintains its integrity throughout the injector's service life, significantly extending the sensor's operational duration.
Solution Approach 2:
The patent utilizes thermal expansion principles by designing the prestressing system with materials and geometries that compensate for thermal expansion and contraction between -40°C and +160°C. The cover and injector body are designed with appropriate thermal expansion coefficients to maintain stable prestress on the sensor across the full temperature range, preventing adhesive degradation and ensuring long-term reliability.
4Reliability
If the sensor is prestressed axially between the bottom wall and cover, then the sensor durability is improved and adhesive is eliminated, but the manufacturing process becomes more complex
Solution Approach 1:
The patent segments the injector body structure by introducing a separate cover component that closes the recess and provides the prestressing interface. This segmentation allows the sensor to be axially prestressed between the injector body bottom wall and the cover, improving durability while enabling standardized manufacturing processes for each component.
Solution Approach 2:
The patent changes the manufacturing approach from adhesive bonding to mechanical prestressing, which requires precise control of prestress forces and geometric parameters. The cover is designed with specific dimensions and the welding process is optimized to achieve the required prestress levels, transforming the manufacturing complexity into precise parameter control rather than complex assembly procedures.
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 sensor durability and signal quality by reducing tensile stress, ensuring reliable operation over extended temperatures and service life, and maintaining structural integrity without adhesive-related risks.
Implementation Method 1
the sensor is prestressed under pressure. This is particularly advantageous since the mechanical load on the material of the sensor can be adjusted by the preload, so that the load experiences a lower tensile stress
Implementation Method 2
the sensor is loaded axially, for example with a force emanating from a pressure fluctuation of the medium
Implementation Method 3
the influence of operating temperatures and ambient temperatures can be at least largely compensated for by skillful selection of the thermal expansion coefficients of the lengths involved
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
The invention relates to an injector comprising an injector body 1 and a nozzle body 2 with a bore 4a accommodating a nozzle needle 5, wherein the nozzle needle 5 is translationally movable in the bore 4a, and a nozzle needle tip 7 cooperating with a nozzle body seat 8, wherein the nozzle body seat 8 is associated with at least one nozzle opening 9, which is controlled by the nozzle needle 5 and connected to a high-pressure line 10, 10a for a medium in the injector body 1 and the nozzle body 2, and wherein a piezoceramic sensor 15 is provided for detecting a pressure profile of the medium. According to the invention, an injector with a sensor 15 for determining a pressure profile of a medium guided through the injector is provided, which is functionally improved.This is achieved by inserting the sensor 15 in a recess 12 aligned with the high-pressure line 10, 10a, and by closing the recess 12 on the side facing away from the high-pressure line 10, 10a with a cover 18 welded to the injector body 1 or nozzle body 2.