Fuel Injector Needle Position Detection Using Elastic Contactor
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Solution Overview
Problem
Conventional fuel injectors face challenges in accurately detecting the needle position due to tolerances and alignment issues, leading to false contacts and reduced reliability in opening and closing operations.
Innovation Solution
A fuel injector with an elastic contactor element that follows the needle's movement to close a detection circuit in two distinct positions, avoiding resistive coatings and improving detection reliability by using a flexible contact part that contacts different points within the control chamber based on the needle's position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If resistive surface coatings are used on contact surfaces to detect needle position, then needle position detection is enabled, but tolerances on the needle cause positioning play and misalignment leading to false contacts
Solution Approach 1:
The patent introduces an intermediary detection system using resistive surface coatings on stationary contact surfaces within the control chamber. These coatings detect needle position through electrical resistance changes when the needle approaches or contacts them, serving as a mediator between the needle and the detection circuit without requiring direct mechanical contact between precision components.
Solution Approach 2:
The patent replaces direct mechanical contact-based position detection with an electrical field-based detection system. Instead of relying on mechanical switches or direct physical contacts that suffer from wear and misalignment, the system uses changes in electrical resistance through the fuel medium caused by the needle's proximity to coated surfaces, substituting mechanical detection with electrical field detection.
2Reliability
If the needle tip makes lateral contact with the nozzle body at the periphery of the seat, then contact is established, but the contact opening/closing occurs prematurely compared to the actual opening or closing
Solution Approach 1:
The resistive coatings act as intermediaries positioned at specific locations within the control chamber to detect the true opening and closing events. By placing these coatings at strategic positions where the needle passes during opening and closing, the system detects the actual valve events rather than premature lateral contacts at the needle tip periphery.
Solution Approach 2:
The patent moves the detection from the traditional needle tip contact point to a different spatial dimension within the control chamber. Instead of detecting at the needle tip where lateral contact occurs, the detection surfaces are positioned in the control chamber volume where the needle passes during its full stroke, detecting position changes in a different spatial plane.
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
Enhances the accuracy of needle position detection, preventing false contacts and improving the reliability of injection events by calibrating at different pressure levels, ensuring precise determination of the injector's open and closed states.
Implementation Method 1
an elastic contact element capable of following the movement of the needle
Data Source
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AI summary
Fuel injector for an internal combustion engine, comprising an injection nozzle (12) with a body (16) in which there is positioned a needle (14) able to move between a closed position (PF), in which a first end (48) of the needle rests against a seat (32) and closes off injection orifices (34) of the nozzle, and a wide open position (PO), in which the first end of the needle is lifted off its seat (32) and allows injection; a filled control chamber (46) and an associated control valve. The injector comprises a device for detecting the position of the needle, comprising an elastic contactor element (62) able to accompany the movement of the needle so as to adopt two positions in which it closes a detection circuit, the two positions respectively corresponding to the closed (PF) and wide open (PO) positions of the needle. The contactor element (62) comprises a base part (64) fixedly mounted and electrically insulated, and an elastically flexible contact part (66) which extends into the chamber and is at a predetermined electrical potential, the contact part (66) pressing against the end part of the needle while at the same time being electrically insulated therefrom.