SEAT PLATE FOR AN INJECTOR AND METHOD FOR MANUFACTURING SUCH A SEAT PLATE

Description

[0001] The present invention relates to a seat plate for an injector and to an injector comprising such a seat plate. Furthermore, the present invention also relates to a method for producing such a seat plate.

[0002] In internal combustion engines such as diesel or gasoline engines, fuel is typically injected into a combustion chamber via an injector in a specific quantity and for a specific duration. Due to the very short injection times, which are in the microsecond range, it is necessary to open and close the injector's outlet opening at a very high frequency. To precisely control these closing times and accurately detect the injector's condition, injector condition detection is required so that a higher-level control unit receives all information about an individual injector, especially information regarding its closing or opening times.

[0003] Such an injector typically has a nozzle needle (also: injector needle), which allows highly pressurized fuel to escape when an outlet hole in the injector is opened. This nozzle needle, in conjunction with this outlet opening, acts like a plug, allowing the fuel to escape when lifted. Therefore, it is necessary to raise this needle at relatively short intervals and then allow it to slide back into the outlet opening after a short time. Hydraulic servo valves can be used to trigger this movement. Such valves, in turn, are controlled by an electromagnet. Alternatively, a piezo element can be used, which reacts faster than the electromagnet-controlled valve.

[0004] Due to the high injection pressures of over 2500 bar, it is not possible to control or move the nozzle needle directly using a solenoid valve. The force required to open and close the nozzle needle would be too great, so such a process would only be feasible using very large electromagnets. However, such a design is not feasible due to the limited space available in an engine.

[0005] Typically, instead of direct control, so-called servo valves are used which control the nozzle needle and are themselves controlled by a solenoid valve or piezo valve. In a control chamber that interacts with the nozzle needle, a pressure level is built up with the help of the high-pressure fuel that acts on the nozzle needle in the closing direction. This control chamber is typically connected to the high-pressure fuel area via an inlet throttle. This control chamber also has a small, closable outlet throttle through which the fuel can escape. When this happens, the pressure in the control chamber and the closing force acting on the nozzle needle is reduced because the high-pressurized fuel in the control chamber can flow out. This causes the nozzle needle to move, opening up the outlet opening at the injector tip.In order to control the movement of the nozzle needle, the valve's outlet throttle is either closed or opened using an anchor element.

[0006] Since the general principle of an injector for injecting fuel is known to those skilled in the art, the functionality of this component will not be discussed in more detail.

[0007] As briefly mentioned above, injector condition detection is extremely important for the controlled operation of the injector. With existing injectors, it is unnecessary or very complex to provide an injector seat plate that is electrically separated from the injector housing and conducts current at specific points to connect the control valve and nozzle needle located below with the injector coil located above.

[0008] The seat plate of the injector is therefore a component which, according to the invention, is used both as a contact element to an injector coil and as an insulator to the injector housing. Furthermore, the seat plate contains a passage running from top to bottom, which represents the outlet throttle of an injector. By placing an armature element in place and sealing the passage, the control chamber below fills with high-pressure fuel via an inlet, so that the nozzle needle is forced into its closed position. When the armature element is lifted off a passage opening, the fuel stored under high pressure flows out and reduces the force acting on the nozzle needle, causing it to lift off its outlet openings and allowing fuel to flow out.

[0009] The detailed functioning of an injector is described, for example, in DE 10 2017 116 383.2 and WO 2017 / 186956 A1.

[0010] To date, insulation using a DLC layer (DLC stands for "diamond-like carbon") has been known, but it has been shown that the robustness of such a DLC layer is not sufficient for demanding injector designs. Especially when the seat plate is axially preloaded by a screw, improved robustness of the insulation layer is required.

[0011] It is therefore the aim of the present invention to provide a seat plate that overcomes the mentioned disadvantage and can also be used in challenging injector concepts.

[0012] This is achieved with a fuel injector according to claim 1 or with the aid of one of the methods for producing a seat plate listed in the claims. A seat plate that is particularly advantageous compared to the prior art, which ensures electrical separation of the seat plate from the injector housing and simultaneously conducts current at specific points to connect the control valve and the nozzle needle to the injector coil, is presented in independent claim 1. Further advantageous embodiments of the invention are set forth in the dependent claims.

[0013] A seat plate for an injector according to the invention comprises a plate-like base body with a first flat side, a second flat side, and at least one circumferential surface connecting the two flat sides, a passage extending through the plate-like base body from the first flat side to the second flat side, and an insulating layer arranged over the entire surface of the circumferential surface and partially on at least one of the two flat sides of the plate-like base body, wherein the plate-like base body consists of an electrically conductive material. The invention is characterized in that the insulating layer comprises a ceramic or consists of this ceramic.

[0014] The ceramic insulation layer improves the robustness and wear resistance of the insulation. Furthermore, in a standard sealing injector design, the high-pressure tightness of the components can also be improved. For example, an insulator can be designed so that the forces occurring during operation lead to increased compression, thus providing a better seal between the components.

[0015] Furthermore, according to the invention, the insulating layer is arranged over the entire surface of the circumferential casing and, with the exception of at least one continuous area without an insulating layer, over the entire surface of at least one of the two flat sides of the plate-like base body, and preferably the insulating layer forms a continuous surface. This design ensures that only a small area is provided as a conductive contact in the flat side, and the remainder is shielded by electrical insulation. This makes it possible to run an electrical line through the seat plate, which allows monitoring of an injector function.

[0016] According to the invention, it can be provided that the plate-like base body of the seat plate comprises or consists of hard metal, tungsten carbide and / or high-speed steel (HSS).

[0017] According to the invention, it can also be provided that the base body is made of hard metal, forming a tough core to absorb high forces, and that a brittle, wear-resistant ceramic layer is arranged on its outer surface, acting as an electrical insulator. The combination of a hard metal base body and a ceramic layer deposited on it has proven particularly advantageous, as the two properties of the different materials complement each other particularly well.

[0018] Preferably, the insulating layer is produced by means of two-component metal injection molding and / or thermal flame spraying.

[0019] In two-component metal injection molding, one of the two components can form the insulating layer and the other of the two components can form the base body.

[0020] In thermal spraying, the ceramic insulation layer is sprayed onto a preferably pretreated base material. The sprayed surface is not melted and is subjected to only minimal thermal stress. A layer forms as the spray particles flatten to a greater or lesser extent upon impact with the component surface, depending on the process and material. They adhere primarily through mechanical bonding and build up the spray layer layer by layer.

[0021] According to an advantageous modification, which does not fall under the wording of the claims, it can be provided that the insulating layer is arranged next to the lateral surface only on one of the two flat sides, so that the ceramic insulating layer can be formed as a sleeve into which the plate-like base body can be inserted.

[0022] It can also be provided that the insulating layer is created by a sintered foil.

[0023] In addition, it is possible that the insulating layer is designed to prevent electrical conductivity.

[0024] According to a further development of the invention, the plate-like base body is rotationally symmetrical or rotationally symmetrical to a rotation axis running centrally through the passage.

[0025] This is advantageous because it allows a seat plate to be installed into an injector without any orientation restrictions. Therefore, it is not necessary to maintain a specific orientation of the seat plate relative to other injector components using positioning pins or the like.

[0026] In addition, according to the invention, it can be provided that the passage has a smaller opening on one of the two flat sides than on the other flat side, and preferably the passage is an outlet throttle of an injector.

[0027] An example which does not fall under the wording of the claims also relates to a method for producing a seat plate according to one of the previously discussed aspects, wherein, in order to produce the insulating layer, the plate-like base body is inserted into a sleeve and connected to it.

[0028] Alternatively or additionally, it is possible to create the insulating layer by sintering a foil.

[0029] The invention further proposes producing the insulating layer or the base body and the insulating layer by a two-component metal injection molding.

[0030] According to an optional development of the invention, the insulating layer can be produced by thermal flame spraying.

[0031] Furthermore, the invention also includes an engine with a fuel injector having a seat plate according to the invention.

[0032] Further advantages, features, and details are described in the following figures. They show: Fig. 1: a partial sectional view of a conventional injector, Fig. 2: a sectional view of a seat plate according to the invention, and Fig. 3: a partial sectional view of an injector with a seat plate according to the invention.

[0033] Fig. 1 shows a partial sectional view of an injector 10 from the prior art. This injector has an inverse sealing concept, in which the sealing force decreases with an increase in pressure in the injector. However, the invention also encompasses the use of an injector with a regular sealing concept, in which the tightness increases with an increase in pressure.

[0034] The injector 10 can be seen, which has a housing 14 in which several injector components are arranged. Essential to the function of the injector 10 are the injector needle 15, the valve formed by the armature 11 and the seat plate 1, and the electromagnet 12, 13, which has a coil winding 16, an inner magnetic pole 12, and an outer magnetic pole 13. Furthermore, a recess is provided in the inner magnetic pole 12 for arranging the spring 17, which presses the armature element 11 toward the valve in order to close the outlet throttle of the valve in a fluid-tight manner when the electromagnet 12, 13 is de-energized.

[0035] If the electromagnet 12, 13 is activated, it pulls the armature element 11 away from the valve with the aid of magnetic force, allowing high-pressure fuel to flow out of the passage 6 from a control chamber that can be closed by the valve. Since this reduces the pressure in the control chamber acting on the injector needle 15, the needle can slide out of a closed position and allows fuel to be dispensed from the injector 10. If, however, the electromagnet 12, 13 is de-energized, the magnetic force acting on the armature element 11 decreases, so that the spring element 17 presses the armature element 11 against the outlet opening of the valve and seals the control chamber or passage 6. This increases the pressure acting on the injector needle 15, forcing it back into its closed position. Consequently, fuel no longer flows out of the outlet opening of the injector 10.

[0036] Figure 2 shows the seat plate 1 according to the invention in a side view. The approximately plate-shaped base body 2 has an upper flat side 3 and a lower flat side 4. The lateral surface 5 of the plate-like base body 2 connects the upper and lower flat sides 3, 4 of the base body 2. Also visible is the insulating layer 7, marked in bold black, which covers areas of the base body 2 for electrical insulation. The insulating layer 7 consists of or comprises ceramic.

[0037] In the illustration, the lower flat side 4 is free of the insulating layer 7. The same also applies to a continuous area located on the upper flat side 3, which, with the exception of this continuous area, is provided with the insulating layer 7 over its entire surface.

[0038] The continuous area on the upper, flat side 3, which is free of an insulating layer, makes it possible to create an electrically conductive connection from this area to the lower, flat side 4, so that elements of an injector 10 arranged above and below can communicate with each other via electrical signals. This communication can also be limited to detecting a state of the injector 10.

[0039] Fig. 3 shows a further seat plate 1 according to the invention in an injector 10. Unlike the seat plate 1 from the Fig. 2 This seat plate 1 now also has an insulating layer on the lower side 4 of the base body 2. Thus, an insulating layer runs inwards from the outer surface 5 on both flat sides 3, 4, so that the insulation against the injector housing 14 is improved.

[0040] An electrical line through the seat plate 1 is therefore not disturbed by contact with the injector housing.

[0041] The anchor element 11 for sealing the passage 6 is shown in its sealing position in the illustration, so that no fuel can flow out and the injector needle is pressed into its seat.

[0042] It is clear to the person skilled in the art that individual aspects discussed with reference to the respective figures can also be combined with one another and that not every detail shown in the figures is necessary for the success of the invention.

Claims

1. A fuel injector (10) having a valve for actuating a movement of an injector needle (15), wherein the valve has a seat plate (1) and an anchor element (11) that optionally rests on the seat plate (1) in order to either seal off or uncover a passage (6) extending through the seat plate (11), wherein the seat plate (1) comprises: a plate-shaped main body (2) having a first planar face (3), a second planar face (4) and at least one all-round lateral surface (5) interconnecting the two planar faces (3, 4), the passage (6), which extends through the plate-shaped main body (2) from the first planar face (3) to the second planar face (4), and an insulating layer (7), which is arranged over the entire all-round lateral surface (5) of the plate-shaped main body (2), wherein the plate-shaped main body (2) consists of an electrically conductive material, characterised in that the insulating layer (7) comprises or is a ceramic material, and the insulating layer (7) is partly arranged on both planar faces (3, 4) of the plate-shaped main body (2) such that, by way of a contiguous region on the upper planar face (3) that is free from insulating layer, it is possible to establish an electrically conductive connection from said region to the lower planar face (4), so that elements of an injector (10) arranged thereabove and therebelow are able to communicate with one another via electrical signals.

2. The injector (10) according to the preceding claim 1, wherein the insulating layer (7) is arranged over the entire all-round lateral surface (5) and, with the exception of at least one contiguous region free from insulating layer, over the entire surface of at least one of the two planar faces (3, 4) of the plate-shaped main body (2), and wherein the insulating layer (7) preferably forms a contiguous surface.

3. The injector (10) according to claim 1, wherein the plate-shaped main body (2) comprises or consists of hard metal, tungsten carbide and / or high-speed steel HSS and wherein the main body preferably consists of hard metal and forms a tough core for absorbing high forces, and the brittle wear-resistant ceramic layer, which acts as an electrical insulator, is arranged on the outer face thereof.

4. The injector (10) according to one of the preceding claims, wherein the insulating layer (7) is produced by means of two-component metal die-casting and / or thermal flame spraying.

5. The injector (10) according to one of the preceding claims, wherein the insulating layer (7) is produced by a sintered film.

6. The injector (10) according to one of the preceding claims, wherein the insulating layer (7) is configured to suppress an electrical conductivity.

7. The injector (10) according to one of the preceding claims, wherein the plate-shaped main body (2) is radially symmetric or rotationally symmetric to an axis of rotation running centrally through the passage (6).

8. The injector (10) according to one of the preceding claims, wherein the passage (6) has a smaller opening on one of the two planar faces (3, 4) than on the other planar face (3, 4), and the passage (6) is preferably an outlet throttle of an injector (10).

9. A method for producing an injector (10) according to one of the preceding claims, wherein the insulating layer (7) is produced by sintering a film.

10. A method for producing an injector (10) according to one of the preceding claims, wherein the insulating layer (7) or the main body (2) and the insulating layer (7) is / are produced by a two-component metal die-casting process.

11. The method for producing an injector (10) according to one of the preceding claims, wherein the insulating layer (7) is produced by thermal flame spraying.

12. A motor having a fuel injector (10) according to one of the preceding claims.