WO2005068825A1

WO2005068825A1 - Valve needle, and valve

Info

Publication number: WO2005068825A1
Application number: PCT/EP2005/050095
Authority: WO
Inventors: Eberhard Kull; Werner Fruth; Jürgen Schindlatz
Original assignee: Siemens Aktiengesellschaft
Priority date: 2004-01-19
Filing date: 2005-01-11
Publication date: 2005-07-28
Also published as: DE102004002678B4; DE102004002678A1; DE112005000139A5

Abstract

Disclosed is a valve comprising a valve member (2) within which a seat is embodied and a valve needle (4) that is provided with a seat area, said seat area resting against the seat of the valve member (2) in a closed position of the valve needle (4). The area of the valve member (2) seat and/or the seat area of the valve needle (4) is/are provided with a sequence of layers encompassing at least one first adhesive layer (14), a first wear-resistant layer (16), a second adhesive layer (18), and a second wear-resistant layer (20).

Description

description

Valve needle and valve

The invention relates to a valve needle and a valve with a valve body, in which a seat is formed, and with a valve needle, which has a seating area which is in contact with the seat of the valve body in a closed position of the valve needle.

Valves of this type are used in particular for supplying fuel in combustion chambers of internal combustion engines. Valves of this type are increasingly supplied with fluid, in particular fuel, which is at a very high pressure, for example up to 2000 bar in diesel internal combustion engines. Valves of this type are increasingly being driven by means of piezo drives, which have been given a very fast switching and thus allow several partial injections during a working cycle of a cylinder of the internal combustion engine. Depending on the operating state, for example, up to five partial injections are carried out per working cycle of the cylinder.

In its closed position, the valve needle rests with its seating area on a seat of a valve body of the valve. With each injection process, the valve needle is moved into a position away from the closed position and then moved back into the closed position. Due to the high forces with which the valve needle is pressed into the seat of the valve body in its seating area and the very frequent movements of the valve needle back and forth from its closed position during operation, the valve needle is subjected to very heavy wear. When the injection valve is closed, microrelative movements of the seat area and occur of the seat of the valve body, which lead to high abassive loads on the valve needle and the valve body even before the yield point is reached. As a result, the spray pattern and the tightness of the injection valve can change negatively, and a failure of the valve may occur.

An injection valve is known from DE 100 38 954 A1, the valve needle of which is provided with a metallic adhesion promoter layer and a diamond-like wear protection layer applied thereon. The thickness of the wear protection layer is in the range from 0.05 to a maximum of 4 μm. Due to the ever increasing number of partial injections during a working cycle of a cylinder and increasing demands on the overall service life of the valve or the valve needle, these requirements can no longer be met with such a wear protection layer.

From WO 01/61182 a valve with a valve needle is also known, which is coated with a diamond-like carbon layer.

The object of the invention is to provide a valve needle and a valve which are reliable over a long period of operation.

The object is achieved by the features of the independent claims. Advantageous embodiments of the invention are characterized in the subclaims.

The invention is characterized by a valve needle and a valve with a valve needle and with a valve body, in which a seat is formed. The valve needle has a seating area which is in contact with the seat of the valve body in a closed position of the valve needle. The valve body is provided in the area of the seat and / or the valve needle is provided in the seat area with a layer sequence of at least one adhesive layer, a first wear protection layer and a second adhesive layer with a second wear protection layer. The wear protection layers can thus have a thickness which can ensure that excessive residual stresses do not occur which can lead to the wear protection layers flaking off. On the other hand, due to the multiple wear protection layer, the valve needle or the valve body can be protected even under highly abrasive conditions for a very long operating time.

The layer structure also has the advantage that wear protection layers, which may be thinner, have a higher elasticity than a single, correspondingly thicker wear protection layer. If, on the other hand, the thickness of a single wear protection layer is greatly increased, it can only cope with extremely small deformations without causing cracks. The total elasticity of the layer sequence is increased by the adhesive layers, which have elastic properties.

An even longer service life can be guaranteed if the layer sequence of the first adhesive layer and the first protective layer is repeated several times.

In a further advantageous embodiment of the invention, there is a gradual transition from the respective adhesive slide to the next wear protection layer and versa. This has the advantage that the good tribological properties of the wear protection layers, i.e. the low coefficient of friction, the high hardness and a lower wear coefficient, are also present to a corresponding extent in the transition area from the respective adhesive layer to the wear protection layer and vice versa.

It is particularly advantageous if the wear protection layers are diamond-like carbon layers. Diamond-like carbon layers of this type are distinguished by a very high proportion of carbon and a high number of tetragonal carbon bonds, so-called sp ³ compounds. Diamond-like carbon layers have diamond-like properties and are therefore extremely hard and have a low wear coefficient.

In a further advantageous embodiment of the invention, the adhesive layers are each a metal layer. Corresponding metal layers are characterized by good adhesive properties for the wear protection layers. They ensure a very good durability of the wear protection layers due to the good heat conduction properties - creation of metals and a related improved heat dissipation from the wear protection layers. This is a significant advantage, especially when the valve or the valve needle is used under high operating temperatures, since the individual wear protection layers are better protected against thermal destruction. The improved heat dissipation can be extremely effective, especially in connection with diamond-like carbon layers

Graphitization of the diamond-like carbon layers can be prevented, that is, a conversion of the sp3 carbon bond into graphite-typical sp2 Carbon bonds. In this way, the wear protection can be guaranteed over a very long operating period even under extreme operating conditions.

In a further advantageous embodiment of the invention, the adhesive layer comprises reactive compounds. For example, Nitrides or carbides have a high hardness and wear resistance if, for example, as a reaction partner for the metal component Nitrogen, oxygen or a carbon gas is used.

Embodiments of the invention are explained below with reference to the schematic drawings. Show it:

1 shows a valve,

2a shows an enlargement of a section of the valve according to FIG. 2 in the region of a tip of a valve needle and FIGS. 2b and 2c further enlargements of the valve needle in the region of the valve tip.

Elements of the same construction and function are provided with the same reference symbols in all figures.

An injection valve 1 has a valve body 2 with a recess 3, into which a valve needle 4 is inserted. The valve needle 4 has a guide 5, in the area of which it is guided in the recess 3 of the valve body 2. The recess 3 has a blind hole 6 from which a nozzle opening 7 is guided through the valve body 2 to the outside and through which the fuel is metered into the combustion chamber of the cylinder of the internal combustion engine. In the area of a tip 8 of the valve needle 4, the valve needle 4 has a seating area 9 with that it comes into contact with a seat 10 of the valve body 2 in the closed position shown in FIG. 1 and thus seals the blind hole 6 and thus also the nozzle opening 7 from a supply bore 11 for supplying fuel.

The valve needle (FIGS. 2a to 2c) is coated, at least in its seating area 9, with a layer sequence described below. However, it can also be coated in a wider area, for example in the entire area of the tip 8 of the valve needle 4 or even up to its guide 5 or including its guide 5, with the layer sequence described below. Alternatively or additionally, the valve body 2 can also be coated with the following layer sequence at least in the region of the seat 10 of the valve body. However, valve needle 4 is preferably coated with the layer sequence, since this is simpler in terms of production technology.

The layer sequence consists at least of a first adhesive layer 14, a first wear protection layer 16, a second adhesive layer 18 and a second wear protection layer 20. The adhesive layers 14, 18, 22 are designed such that they adhere well to the wear protection layers 16, 20. 24 ensure. The adhesive layers 14, 18, 22 preferably consist of pure metals, for example Cr, Ti, Al, W, Wc or are reactive compounds, for example with nitrogen, that is to say hard material layers or with nitrogen and oxygen, that is to say oxynitrides or with a reactive gas, a hydrocarbon gas layer.

The wear protection layers 16, 20, 24 preferably consist of diamond-like carbon layers which are distinguished by a very high carbon content and in which the Carbon atoms enter into a large number of sp ^ compounds, so-called tetragonal carbon compounds. Such diamond-like carbon layers are also referred to as DLC layers, as amorphous, diamond-like carbon ac: ho- or also as a hydrogen-free carbon layer ta-c layers. The abrasion wear coefficient of such layers is below 1 x 10- ^ ⁵ rct ^ N - ^ - irf ^" !. The sliding friction coefficients of these layers are dry at μ <0.2 and in diesel-lubricated arrangements significantly lower.

Such carbon-containing wear protection layers can be deposited, for example, by means of a CVD (= chemical vapor d-position) process, but can also be carried out by means of an azero plasma process.

The individual wear protection layer is preferably between about 0.1 to 3 µm thick. The individual adhesive layer 14, 18, 22 is preferably a few hundredths to tenths thick. With such an alternating layer sequence, a total layer thickness of, for example, 10 μm can easily be produced. If the adhesive layers 14, 18, 22 have good thermal conductivity, a graphitization of the wear protection layers 16, 20, 24 is reliably avoided even under a high thermal load, as occurs in internal combustion engines. So it can be advantageous to provide a large number of adhesive layers and wear protection layers to achieve less thick but also very thick total layer thicknesses, so as to keep the thermal load on the individual wear protection layer low. It can also be advantageous to make the inner wear protection layers thinner than the outer wear protection layers. For example, in addition to the first and second adhesive layers 14, 18 and the first and second wear protection layers 16, 20, a third adhesive layer 22 (FIG. 2C) and a third wear protection layer 24 can also be provided. However, additional adhesive layers and wear protection layers can also be provided. Appropriate process control during the deposition of the adhesive layers and the wear protection layers can also result in a gradual transition from the respective adhesive layer to the wear protection layer and vice versa. In this way, correspondingly adapted tribological properties can also be ensured in the area of the transition. The layer sequence described enables total layer thicknesses of 10 μm and above to be produced. Of course, the total layer thicknesses can also be significantly less than 10 μm.

Claims

claims

1. Valve needle for a valve (1) which has a seating area (9) with a layer sequence applied thereon from at least a first adhesive layer (14), a first wear protection layer (16), a second adhesion layer (18) and a second wear protection layer (20).

2. Valve needle according to claim 1, in which the layer sequence of the first adhesive layer (14) and the first wear protection layer (16) is repeated several times.

3. Valve needle according to one of the preceding claims, in which there is a gradual transition from the respective adhesive layer (14, 18, 22) to the next wear protection layer (16, 20, 24) and vice versa.

4. Valve needle according to one of the preceding claims, wherein the wear protection layer (16, 20, 24) is a diamond-like carbon layer.

5. Valve needle according to one of the preceding claims, wherein the adhesive layer (14, 18, 22) is a metal layer.

6. Valve needle according to one of the preceding claims, wherein the adhesive layer comprises reactive compounds.

7. Valve with a valve body (2), in which a seat (10) is formed, and with a valve needle (4), which has a seating area (9) which is in contact with the valve needle (4) in a closed position Seat (10) of the valve body (2), the valve body (2) in the area of the seat (10) and / or the valve needle (4) in the seat area (9) with a Layer sequence comprising at least a first adhesive layer (14), a first wear protection layer (16), a second adhesion layer (18) and a second wear protection layer (20) is provided.

8. Valve according to claim 7, wherein the layer sequence of the first adhesive layer (14) and the first wear protection layer (16) is repeated several times.

9. Valve according to one of claims 7 or 8, in which a gradual transition from the respective adhesive layer (14, 18, 22) to the next wear protection layer (16, 20, 24) and vice versa.

10. Valve according to one of claims 7 to 9, in which the wear protection layer (16, 20, 24) is a diamond-like carbon layer.

11. Valve according to one of claims 7 to 10, wherein the adhesive layer (14, 18, 22) is a metal layer.

12. Valve according to one of claims 7 to 11, wherein the adhesive layer comprises reactive compounds.