EP2699790B1 - Component, in particular of a fuel injection system, having a surface - Google Patents

Description

The present invention relates to cooperating components, in particular a fuel injection system, each having a surface, wherein the at least one surface has a structure which counteracts adherence of a reactive medium, in particular a fuel, a biofuel, an additive and / or a fatty acid. Furthermore, the invention relates to a method for producing at least one component of two interacting components, each having a surface, wherein a structure is applied to the surface of the at least one component, the adherence of a reactive medium, in particular a fuel, a biofuel, an additive and / or a fatty acid counteracts. The surface has an altered surface texture, in particular with regard to the surface properties and their surface structure.

State of the art

Such cooperating components are known from the DE 102 32 050 A1 known. These components are a valve needle and a valve body of a fuel injection valve, wherein the valve needle tip of the valve needle and the associated valve seat in the valve body have microwells, which are intended to cause a reduction in wear of the cooperating components. The wear occurs in particular upon impact of the valve needle tip on the valve seat, wherein this impact occurs abruptly for fast closing of the injection openings in the valve body. When the valve needle is moved away from the valve seat for release of the injection openings, the valve needle tip moves away from the valve seat by a defined path so that fuel can flow to the injection openings through the annular gap formed between the valve pin tip and the valve seat.

From the DE 10 2004 063 165 A1 An injection valve is known which has knobs in the region of injection ports controlled by a valve needle. These nubs, which are arranged in the injection openings, are intended to prevent adhesion of dirt particles to the surface of the injection openings. The injection openings are bores with a small diameter, which are incorporated in the valve body.

The DE 103 44 584 A1 relates to a fuel injection valve in which a valve seat with a predetermined surface roughness is to be produced. The generation of the surface roughness is effected by a coating of the valve seat. In this case, the surface thus produced with the defined surface roughness lies outside the range of interacting components, that is to say the valve seat and a valve needle tip. The purpose of this surface roughness is to reduce a vortex intensity of the fuel jet.

The object of the invention is to change the surface condition of at least one component of a component group in such a way that the possibility of the adhesion of deposits is reduced or the effects thereof are minimized.

Disclosure of the invention Advantages of the invention

This object is achieved in that the components are two interacting, mutually moving components which form a fit with a guide play, and in that the surface has a surface texture determined by a mean roughness Ra and the arithmetic mean roughness has a value of> = 0.2 μm. The corresponding method for producing such a component provides that the structure of the surface of at least one component of the two interacting, mutually moving components that form a fit with a guide play is designed such that their nature is of an arithmetic mean roughness Ra with a value> = 0.2 microns is determined. Here, the surface texture, so the surface property and the Surface structure designed to minimize adhesive. This refinement or this method is based on the recognition that such a component or groups of components may increasingly be with a reactive medium, in particular a fuel (diesel fuel, gasoline), a biofuel, an additive, a fatty acid or any mixture thereof , Contact, in which the possibility of the formation of deposits and / or of aging products in the medium is increased by the basic nature of the medium or by the inclusion of additives. Such deposits and aging products preferably adhere to the medium-carrying, ie fluid-carrying surfaces of the individual components. By this adhesion but the mobility of, for example, each other moving components is reduced so much that it can lead to jamming or sticking of the component groups. If, for example, the components are designed to execute a switching function in the case of narrow guide plays, the guided component can be prevented from switching by such a jamming or gluing. By virtue of the fact that at least one surface of one of the interacting components is minimized in adhesive force, deposits or aging products can not or only to a small extent apply adhesive forces to this component, so that the risk of breakdown of the corresponding component group is minimized. In the most general embodiment, however, only one surface of a component is designed according to the invention in order to counteract attachment of a medium or of a fluid. In this case, the surface condition is determined by an arithmetic mean roughness Ra and the average roughness Ra of the surface of the component has a value of> = 0.2 μm. In a further embodiment, the surface condition of an average roughness Rz is determined and the surface roughness Rz of the surface has a value of> = 0.2 microns, in particular> = 1.5 microns, on. Finally, in another embodiment, the surface finish is determined by a profile depth Pt and the profile depth P _{t of} the surface has a value of> = 0.2 μm, in particular> = 2 μm. All of these values characterize limit values below which the mutual holding force or adhesive force of components communicating with one another is extremely small with even slight changes in the surface textures mentioned above increases. On the other hand, these values ensure that the sliding properties of the interacting components are unimpaired.

In a development of the invention, the structure is a screw thread structure or a rhombic structure or one of the two structures or a combination of the two structures is applied. These structures have proven to be particularly suitable to counteract adhesion of a reactive medium.

In a further development of the invention, the surface is processed by a grinding process, a laser structuring process or a hard turning process, and consequently the corresponding component is ground, laser-structured (for example by a pulsed laser and a structure or lotus effect of the grooves) or hard twisted. As a grinding process, for example, a center grinding process is in question, in which there is a formation of the surface with an outer contour, for example a cylindrical surface that matches or at least resembles the screw thread structure. Another grinding process is a cross-grinding process in which the surface assumes a structure that corresponds to or at least resembles the rhombic structure. A cross-grinding takes place in particular in an internal grinding process of holes. It is common to all these surface treatment processes that they can be represented reliably with a reasonable workload.

In a development of the invention, the component is an arbitrary component of a fuel injection system, in particular a fuel pump, a fuel injector or another system-critical component such as a switching valve. Particularly in the case of a fuel injection system, the problem of adhering the individual components to the interacting component groups, for example when additives or a biodiesel mixture are added, which in turn lead to deposits upon aging of the biodiesel, occurs for the respective fuel.

The object of the invention is therefore preferably usable with cooperating components of a fuel injection system, wherein the fuel injection system is operated with a fuel having at least one biodiesel mixture. In particular, in such fuel injection systems operated with a biodiesel mixture, the constituents of the admixture adhere to metallic surfaces by a polar character of the fatty acids contained in the biodiesel mixture. At the same time, a reduction of the adhesive force can be achieved by a reduction of the material carrying component Rmr (0,1), (0,2) and (0,3) (according to Abbott).

In this case, starting from an initial value with a first material-carrying component Rmr, the material-carrying component can be reduced by up to 65% of the material-carrying component Rmr according to an Abbott curve of the surface of the component. By way of example, the material carrying component Rmr (0,1) has a value <= 25%, the material carrier component Rmr (0,2) has a value <= 45% and the material carrier component Rmr (0,3) has a value <= 65%.

Advantageous developments of the invention are described in the drawings, in which an illustrated in the figures embodiment of the invention is described in detail.

Brief description of the drawings

Figur 1

ein Anwendungsbeispiel der Erfindung an einem Kopplermodul eines Kraftstoffeinspritzsystems,

Figur 2

eine Versuchsanlage zur Bildung eines Führungsspiels zwischen einem Kopplerkolben und einer Abzugsglocke zu einer Belagsablagerungsbestimmung ,

Figur 3

ein Diagramm mit der Darstellung der Auswirkungen verschiedener Oberflächenbeschaffenheiten einer Komponente in Abhängigkeit der gleichbleibenden Oberfläche einer Gegenkomponente,

Figur 4

ein Diagramm mit dem exponentiellen Zusammenhang zwischen einer Klebekraft und einer Veränderung der Oberflächenbeschaffenheit einer Komponente und

Figur 5

ein Diagramm mit einer Darstellung der prozentualen Verteilung von Oberflächenbeschaffenheiten einer Komponente gegenüber einer Klebekraft der Komponente.

Show it:

FIG. 1

an application example of the invention to a coupler module of a fuel injection system,

FIG. 2

a pilot plant for forming a guide clearance between a coupler piston and a take-off bell to a deposit deposit determination,

FIG. 3

a diagram showing the effects of different surface properties of a component as a function of the constant surface of a counter component,

FIG. 4

a diagram with the exponential relationship between an adhesive force and a change in the surface finish of a component and

FIG. 5

a diagram showing the percentage distribution of surface properties of a component against a sticking force of the component.

Embodiment of the invention

The left picture of the FIG. 1 shows a coupler module of a fuel injection system of an internal combustion engine. This fuel injection system is designed in particular for use in a common-rail fuel injection system, in which fuel is stored under pressure of from about 1600 bar in a memory. This fuel is supplied from a fuel tank of a high-pressure pump and this memory From the memory, fuel is taken from fuel injectors via high pressure lines as needed. The fuel injectors are electrically actuated for actuation and inject the fuel into a combustion chamber of the internal combustion engine. Such a fuel injector has such a coupler module as part of the electrically controlled fuel metering device. Such common rail fuel injection systems are used in particular in auto-ignition internal combustion engines, which are operated with diesel fuel. This diesel fuel is increasingly biodiesel in the order of up to 20%, possibly even beyond going added. Alternatively, the diesel fuel can also be replaced by alternative fuels which have at least similar ignition properties as diesel fuel. All of these alternative fuels or biodiesel have the property that at least parts of their constituents can adhere to metallic surfaces and form deposits due to the polar character of the fatty acids they contain.

The fuel - flushed coupler module according to the left picture of the FIG. 1 has a coupler sleeve 1 with a continuous cylindrical bore into which two coupler pistons 2 are inserted. Such a coupler piston 2 with an annular flange, which prevents the complete immersion of the coupler piston 2 in the bore is in the right figure of FIG. 1 shown in an enlarged scale. The two coupler pistons are guided, for example, with a guide clearance of 4 μm in the coupler sleeve 1. The coupler transmits a force exerted by a piezoelectric actuator on the upper coupler piston 2 force on the lower coupler piston 2, which ultimately transmits the movement caused by the piezoelectric actuator on a valve piston for driving a valve needle of the fuel injector. The valve needle is moved by the described device from a closed position to an open position and vice versa. In the open position, fuel is injected into an associated combustion chamber of the internal combustion engine through injection openings of a valve needle body of the fuel injector controlled by the valve needle. The invention is explained in the present case on such a coupler module, but is applicable to any other component group of a Kraftstoffeinspritzsytems.

The inventively designed component is the coupler piston 2 or the coupler sleeve 1 or both as a component group.

The pilot plant according to FIG. 2 has a module with a base 3, which has a cylindrical recess into which a coupler piston 2 is inserted and clamped with its annular flange. The actual coupler piston 2 is surrounded by a discharge bell 4, the cylindrical bore for receiving the actual coupler piston 2 with respect to the diameter and the surface finish of the bore of the coupler sleeve 1 corresponds.

Through a channel 5a, for example, a diesel fuel mixed with biodiesel is fed into the take-off bell 4, guided past the fit between the coupler piston 2 and the take-off bell 4 on the thus formed guide play with a guide clearance of preferably 5 μm and through the passage 5b in the base part 3 dissipated. The guide play can be varied between 3 μm and 14 μm. To carry out the experiment, for example, in a time frame of several hours, days or weeks, biofuel-added diesel fuel or even concentrated biofuel is fed to the pilot plant. For evaluating the experiment, the force with which the extraction bell 4 must be lifted in order to release itself from the coupler piston 2 retained in the base part is measured. From the measured values obtained with trigger bells 4 (or optionally coupler pistons 2), which have different surface properties, it is possible to determine which surface finish is optimized for, for example, different biofuels. Consequently, the surface texture determined in this way has the property that constituents of the biodiesel do not adhere or adhere poorly to this metallic surface.

The FIG. 3 shows a diagram showing the effects of various surface textures of a component (for example, the trigger bell 4 or the piston 2) depending on the constant surface of a counter-component (for example, the coupler piston 2). The surface textures are characterized by an arithmetic mean roughness Ra, an average roughness Rz and a profile depth Pt. The Gradients of the individual surface textures indicate the relationship to the respective breaking force F. The breaking force F thus denotes the previously described release force of the withdrawal bell 4. It can be seen that the breaking force F is the lowest in each case when the arithmetic mean roughness Ra and the profile depth Pt are large. At initially significantly decreasing values of the individual surface textures, the breaking force F _increases only to a comparatively slight _extent up to a common limit F _grenz .

FIG. 4 shows in analogy to FIG. 3 a diagram with the exponential relationship between an adhesive force and a change in the surface structure of a component and at different Materialtraganteilen Rmr according to the so-called Abbott curve at -0.1, -0.2 and -0.3 (Rmr (0.1); (0.2); (0.3)). Here, too, it can be seen that up to a limit value F _{grenz there is} a clear change in the breaking force as a function of the percentage of load.

FIG. 5 shows in diagram form in three different modules MD1, MD2 and MD3 have the different combinations of surface textures (surface property and surface structure). In particular, this graph shows the effects of the arithmetic mean roughness Ra, the average roughness depth Rz and the profile depth Pt versus the different material support rates Rmr and in particular the breaking force F. Module MD1 shows an equal ratio of all values that can be represented by the implementation of the invention. Module MD2 shows that a reduction of the average arithmetic mean roughness Ra, the average roughness depth Rz and the profile depth Pt and an increase in the material carrying component Rmr lead to an increase in the breaking force F. Then, as shown in the module MD3, the arithmetic mean roughness Ra, the average roughness Rz and the tread depth PT only slightly further reduced and there is an increase in the material carrying part Rmr, in particular the breaking force F increases rapidly. Applied to the subject matter of the present invention, this means that in the balanced module MD1 the possibility of the effects of adhering deposits on the respective surface is minimized. In contrast, the possibility of the effect of the adhesion of deposits on the respective surface is very high in module MD3.

Claims (11)

1. Interacting components, in particular of a fuel injection system, each having a surface, wherein the at least one surface has a structure which counteracts adhesion of a reactive medium, in particular of a fuel, of a biofuel, of an additive and/or of an aliphatic acid,
   characterized in that the components are two interacting components which move relative to one another and which form a fit with a guide clearance, and in that the surface has a surface condition defined by an average roughness value Ra, and the arithmetic average roughness value has a value of >= 0.2 µm.
2. Component according to Claim 1,
   characterized in that the structure is a screw thread structure or a rhomboidal structure.
3. Component according to Claim 1 or 2,
   characterized in that the surface condition is defined by an average roughness depth Rz and the average roughness depth Rz has a value of >= 2 µm.
4. Component according to one of the preceding claims,
   characterized in that the surface condition is defined by a profile depth Pt and the profile depth Pt has a value of >= 2 µm.
5. Component according to one of the preceding claims,
   characterized in that the surface is ground, laser-structured or hard-turned.
6. Method for producing at least one component of two interacting components, each having a surface, wherein, to the surface of the at least one component, there is applied a structure which counteracts adhesion of a reactive medium, in particular of a fuel, of a biofuel, of an additive and/or of an aliphatic acid,
   characterized in that the structure of the surface of at least one component of the two interacting components which move relative to one another and which form a fit with a guide clearance is configured such that the condition thereof is defined by an arithmetic average roughness value Ra with a value of >= 0.2 µm.
7. Method according to Claim 6,
   characterized in that a screw thread-like structure or a rhombic structure is applied to the surface of the component.
8. Method according to either of Claims 6 and 7,
   characterized in that the surface of the component is machined by way of a grinding process, a laser structuring process or a hard turning process.
9. Method according to Claim 8,
   characterized in that the grinding process is a centre grinding process or a cross-grinding process.
10. Method according to one of Claims 6 to 9,
    characterized in that the structure of the surface is configured such that the condition thereof is defined by an average roughness depth Rz with a value of >= 2 µm and/or by a profile depth Pt of the surface with a value of >= 2 µm.
11. Method according to one of Claims 6 to 10,
    characterized in that, proceeding from an initial value with a first material contact area Rmr, the material contact area Rmr is reduced, in accordance with an Abbott curve of the surface of the component, by up to 65%.

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