Needle Stroke Switch Insulation via Ceramic Sleeve
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Solution Overview
Problem
Existing needle lift switches in fuel injectors face challenges with mechanical wear leading to electrical conductivity issues under mechanical stress, compromising long-term insulation and reliability, especially under high-pressure conditions.
Innovation Solution
A needle lift switch featuring a seat plate with ceramic and/or plastic parts for insulation, where the ceramic parts, such as zirconium oxide, provide dimensional stability and wear resistance, ensuring electrical isolation from the injector housing and preventing direct contact, with a sleeve-shaped design for radial centering and protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a DLC layer is applied to insulate the seat plate, then electrical insulation is achieved, but the robustness and long-term reliability under mechanical stress are insufficient
Solution Approach 1:
The patent uses a composite structure combining metal seat plate with ceramic or plastic insulating parts. The ceramic/plastic materials provide both electrical insulation and mechanical robustness, overcoming the limitations of DLC coating which lacks sufficient mechanical strength under preload stress.
Solution Approach 2:
The seat plate is divided into separate functional components: the metal seat plate base and separate ceramic or plastic insulating parts. This segmentation allows each component to optimize its properties - metal for structural strength and ceramic/plastic for insulation and wear resistance.
2Strength
If the seat plate is axially preloaded by a screw, then mechanical fastening is achieved, but the insulating layer becomes electrically conductive due to mechanical wear
Solution Approach 1:
Ceramic or plastic parts are introduced as intermediary elements between the metal seat plate and the screw fastening system. These intermediaries protect the electrical insulation from direct mechanical contact and wear caused by axial preload, maintaining electrical stability while allowing mechanical fastening.
3Reliability
If a ceramic or plastic part is used for insulation, then wear resistance and dimensional stability are improved, but the device complexity increases
Solution Approach 1:
The ceramic or plastic parts serve multiple functions simultaneously: electrical insulation, mechanical wear resistance, dimensional stability under pressure, and ease of manufacture. This multi-functionality justifies the added structural elements by consolidating multiple requirements into single components.
Solution Approach 2:
The patent changes the material parameters from coated metal (DLC) to solid ceramic or plastic materials. This parameter change fundamentally improves wear resistance and dimensional stability while the simple geometric forms of these parts keep manufacturing complexity manageable.
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
The solution ensures reliable long-term electrical insulation and robustness under high-pressure and pulsating conditions, preventing mechanical wear-induced conductivity issues and maintaining injector performance.
Implementation Method 1
at least one ceramic and/or plastic part which contacts the seat plate in order to create the insulation of the seat plate from the injector housing surrounding it
Implementation Method 2
a pressure level is built up using the high-pressure fuel available, which acts on the nozzle needle in the closing direction
Implementation Method 3
This control chamber or control valve is typically connected to the high-pressure fuel area via an inlet throttle
Implementation Method 4
the pressure in the control chamber and the closing force acting on the nozzle needle is reduced because the high-pressure fuel in the control chamber can flow out
Implementation Method 5
a small, closable outlet throttle through which the fuel can escape to a low-pressure area
Implementation Method 6
the at least one ceramic and/or plastic part has a sleeve shape, in particular a ring shape or a cylinder jacket shape, which is suitable for radially surrounding the seat plate, wherein preferably the seat plate is inserted into the sleeve-shaped ceramic and/or plastic part in order to achieve radial centering of the seat plate
Data Source
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AI summary
The invention relates to a needle stroke switch and to a fuel injector having such a needle stroke switch, the needle stroke switch for a fuel injector comprising a seat plate having a plate-like main body and a passage connecting the two planar sides of the plate-like main body, an anchor element which can be lifted off from the passage in the seat plate and can be placed thereon to form a seal, and a control valve which is arranged on the side of the seat plate opposite the anchor element and is designed to interact with a nozzle needle. The seat plate is electrically isolated from an injector housing surrounding it and an electrical connection to the injector housing is possible only via the nozzle needle which interacts with the seat plate. Furthermore, the needle stroke switch is characterised in that at least one ceramic and/or plastic part is provided which contacts the seat plate in order to isolate the seat plate from the injector housing surrounding it.