Piezoelectric Sensor Electrode Overlap for Fuel Injector Pressure Measurement
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Solution Overview
Problem
Existing fuel injectors face challenges in achieving high resolution and signal quality from piezoelectric sensors while minimizing their size, which affects the accuracy of fuel pressure measurement and nozzle needle control, especially due to wear over time.
Innovation Solution
The arrangement of the two electrodes of the piezoelectric element, with partial overlap and electrical isolation, allows for maximum ceramic surface area utilization, minimizing the sensor's size by avoiding lateral protrusion and using an insulating element, either as a separate component or coating, to enhance electrical isolation and simplify production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the piezoelectric element is made larger to increase sensor signal resolution, then the measurement precision is improved, but the device size and recess requirements increase
Solution Approach 1:
The patent transitions from a conventional planar electrode arrangement to a three-dimensional overlapping configuration where the first electrode extends beyond the second electrode's boundary and folds back to overlap with it. This dimensional change allows the electrodes to occupy the same projected area while maintaining electrical isolation through vertical separation, thereby maximizing the active sensing area without increasing the device's footprint.
Solution Approach 2:
The first electrode is folded back to overlap with the second electrode, creating a nested configuration where one electrode is partially contained within the projected area of the other. This nesting allows both electrodes to be positioned on the piezoelectric element's surface without lateral protrusion, effectively utilizing the available surface area while maintaining compact dimensions.
2Measurement precision
If the electrode area is increased to improve signal generation, then the measurement precision is improved, but the device complexity increases due to additional insulation requirements
Solution Approach 1:
An insulating element is introduced as an intermediary component positioned between the first and second electrodes in their overlapping region. This mediator prevents electrical short-circuiting while allowing the electrodes to maintain close proximity for optimal signal generation. The insulating element can be a separate component or a coating applied to one of the electrodes, providing electrical isolation without requiring complex insulation structures.
3Manufacturing precision
If the piezoelectric element is made smaller to reduce device size, then the manufacturing precision is improved, but the sensor signal resolution decreases
Solution Approach 1:
By utilizing the vertical dimension through electrode overlap and folding, the patent enables a compact piezoelectric element design that maintains large active electrode area. The overlapping electrodes are separated in the vertical direction rather than requiring lateral expansion, allowing high signal resolution to be achieved within a smaller footprint suitable for precise manufacturing.
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 higher sensor signal resolution with a smaller footprint, improving fuel pressure measurement accuracy and reducing thermal stress, while maintaining a compact form factor and ease of assembly.
Implementation Method 1
a sensor element designed as a piezoelectric element is bonded to the surface of the injector housing... strains or tensile stresses are generated by the piezoelectric element, which is bonded to the area of this deformation. These stresses are transferred to the piezoelectric element via the adhesive layer, resulting in a corresponding voltage signal.
Data Source
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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).wherein the measuring device (30) comprises a sensor element (32) designed as a piezoelectric element (31; 31a) with two electrodes (35, 36), wherein the sensor element (32) is at least indirectly connected to the deformation area (27), wherein a first electrode (35) on the side of the sensor element (32) facing away from the deformation area (27) forms an overlap area (40) with a second electrode (36), and wherein in the overlap area (40) of the two electrodes (35, 36) these are arranged at least partially, preferably completely, electrically insulated from each other.