Fuel Injector Sensor Housing with Axial Pretension
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Solution Overview
Problem
Existing fuel injectors face challenges in manufacturing due to the sensitivity of piezoelectric sensor elements to tensile stresses and the vulnerability of adhesive connections to external media, leading to potential malfunctions and increased scrap rates, as the functionality of the measuring device can only be checked after assembly and is prone to reliability issues over the service life.
Innovation Solution
The sensor element is housed in a sensor housing under axial pretension, allowing for preassembly and separate testing, and is connected to the injector housing indirectly via the sensor housing, which prevents tensile stresses and protects the piezoelectric element from external influences by using a closed housing design and a circumferential weld for robustness and media protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the sensor element is connected to the injector housing using an adhesive connection, then the sensor element can be mounted on the injector housing, but the adhesive connection is exposed to external influences that adversely affect the strength and reliability of the connection over the service life
Solution Approach 1:
The patent introduces a support device as an intermediary component between the sensor element and the injector housing. This support device is connected to the injector housing via an adhesive connection, while the sensor element is mechanically secured to the support device. This intermediary structure protects the adhesive connection from external influences (fuel, temperature, pressure) while maintaining the mounting functionality, thereby resolving the contradiction between ease of manufacture and reliability.
2Device complexity
If the sensor element is directly mounted on the injector housing, then the assembly process is simple, but the sensor element is sensitive to tensile stresses and malfunctions may occur
Solution Approach 1:
The support device serves as a mediator that absorbs and distributes mechanical stresses, particularly tensile stresses, away from the sensitive piezoelectric sensor element. The support device is designed to bear the mechanical loads while the sensor element remains protected, thus reducing device complexity compared to direct mounting while significantly improving reliability.
3Ease of manufacture
If the measuring device is assembled after the injector housing is manufactured, then the components can be connected to the injector housing, but the functionality can only be checked after assembly and faulty components result in scrap
Solution Approach 1:
The patent divides the measuring device into separable components: the sensor element and the support device. The support device can be assembled and tested independently before the sensor element is mounted. This segmentation allows for functional testing of the support device structure without requiring the complete assembly, enabling early detection of manufacturing defects and reducing scrap rates while maintaining ease of assembly.
4Reliability
If the sensor element is subjected to axial force in the direction of the adhesive connection to improve functionality, then the piezoelectric element functionality is improved, but the adhesive connection is exposed to tensile stresses that it cannot withstand
Solution Approach 1:
The support device acts as an intermediary that bears the axial compressive forces required for piezoelectric element functionality. The sensor element is preloaded through the support device structure, which transfers these forces mechanically rather than through the adhesive connection. This resolves the contradiction by maintaining the necessary mechanical preload for sensor functionality while protecting the adhesive connection from excessive tensile stresses.
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 solution enables pre-assembly testing of the measuring device, enhances the mechanical robustness of the sensor element, and prevents media ingress, improving reliability and reducing scrap rates by avoiding adhesive connections and ensuring the sensor element remains robust under tensile stresses.
Implementation Method 1
The sensor element having a piezoelectric element detects expansions or tensile stresses occurring in the contact area with the injector housing
Implementation Method 2
the injector housing has a deformation area in the area of the measuring device, which is designed to be elastically deformable as a function of the fuel pressure in the supply bore
Data Source
Figure 1
Figure 2~3
AI summary
The invention relates to a fuel injector (10), in particular a common-rail injector, with an injector housing (11) in which a high-pressure chamber (15) is formed, which can be supplied with pressurized fuel via a supply bore (19) arranged in the injector housing (11), with at least one injection opening (12) formed in the injector housing (11) and connected at least indirectly to the high-pressure chamber (15) for injecting fuel into the combustion chamber of an internal combustion engine, with an injection element (16) that releases or closes the at least one injection opening (12), and with a measuring device (30) for at least indirectly detecting the pressure in the high-pressure chamber (15) or the supply bore (19), wherein the measuring device (30) is configured to detect an elastic deformation of a deformation area (27) arranged in operative connection at least indirectly with the supply bore (19) or the high-pressure chamber (15).and wherein the measuring device (30) has a sensor element (32) which is arranged in operative connection with the surface (26) of the deformation area (27).