WO2012143178A1

WO2012143178A1 - Component, in particular of a fuel injection system, having a surface

Info

Publication number: WO2012143178A1
Application number: PCT/EP2012/054230
Authority: WO
Inventors: Frieder Buerkle; Andreas Ellenschlaeger
Original assignee: Robert Bosch Gmbh
Priority date: 2011-04-21
Filing date: 2012-03-12
Publication date: 2012-10-26
Also published as: DE102011007876A1; EP2699790B1; EP2699790A1

Abstract

Disclosed is a component, in particular of a fuel injection system, comprising a surface. According to the invention, in such a component, the constitution of a surface is changed in such a manner that the potential for adhesion and the effect of the adhesion of deposits are reduced. This is achieved in that the surface has a structure which counteracts the adhesion of a reactive medium, in particular of a fuel, of a biofuel, of an additive and/or of a fatty acid.

Description

description

Title:

COMPONENT, IN PARTICULAR A FUEL INJECTION SYSTEM, WITH A SURFACE

The present invention relates to a component, in particular a

Fuel injection systems, with a surface. Furthermore, the invention relates to a method for producing such a component. The surface has an altered surface texture, in particular with regard to the surface properties and their surface structure.

State of the art

Such components of a component group are known from DE 1 1 2008 002 560 T5. These components are subcomponents of a

Fuel injection system, in particular a fuel injector, for a

Internal combustion engine. For example, the valve needle and the

Valve needle receiving valve pin body improved resistance to wear on. This is to reduce the failure rates of the

Fuel! Njektors be achieved. This should be achieved by a special coating of the valve needle and / or the valve needle body. Examples of such a coating are a metal nitride coating or a DLC coating involving various physical

Deposition processes. Such optimized components of a

Fuel injection system can be operated with fuels that cause high wear rates - ie wear rates. Such fuels include, for example, a low lubricity diesel fuel, a very low sulfur fuel, certain biodiesel, and, for example, fuels having various fuel additives. The object of the invention is to modify 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 their effects are minimized.

DISCLOSURE OF THE INVENTION Advantages of the Invention This object is achieved in that the surface has a structure which counteracts adhesion of a reactive medium, in particular a fuel, a biofuel, an additive and / or a fatty acid. The corresponding method for producing such a component provides that a structure is applied to the surface of the component, which counteracts adhesion of a reactive medium, in particular a fuel, a biofuel, an additive and / or a fatty acid. The surface texture, ie the surface property and the surface structure, is designed to minimize adhesive force. 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, moving to each other

Components 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. Because at least one

Surface of one of the interacting components is adhesive-minimized, Deposits or aging products can not or only to a small extent apply adhesive forces to this component, so that the risk of failure 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 adhere a medium

or to counteract a fluid.

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 texture of an arithmetic mean roughness Ra is determined and the average roughness Ra of

Surface of the component has a value> = 0.2 μηι, in particular> = 0, 1, 5 μηι, on. In a further embodiment, the surface condition of an average roughness Rz is determined and the surface roughness Rz has the surface has a value of> = 0.2 μηι, in particular> = 1, 5 μηι, on. Finally, in another embodiment, the surface condition of a profile depth Pt is determined and the profile depth P _{t of} the surface has a value of> = 0.2 μηι, in particular> = 2 μηι, on. All these values indicate limit values below which the mutual holding force or adhesive force of

communicating with each other at a low level

Changes in the above surface textures extremely increases. On the other hand, these values ensure that the

Sliding properties of the interacting components are unaffected.

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 resulting structure or lotus effect (knobbly structure) 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-cutting process in which the surface assumes a structure that corresponds or at least resembles the rhombic structure. A cross-grinding takes place in particular in an internal grinding process of holes. All of these

Surface treatment processes have in common that they can be represented reliably with a reasonable workload.

In a further development of the invention, the component is an arbitrary component of a fuel injection system, in particular a fuel pump

Fuel injector or other system critical component such as

for example, a switching valve. Especially with a

Fuel injection system, the problem of adhering the individual components to the interacting component groups,

for example, with the addition of additives or a biodiesel mixture, which in turn lead to deposits on aging of the biodiesel, to the respective fuel on.

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 may be the material-carrying component Rmr after one

Abbott curve of the surface of the component can be reduced by up to 65%. 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

Show it:

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

Figure 2 shows a pilot plant for forming a guide game between a coupler piston and a take-off bell to a

Deposit deposit determination,

FIG. 3 shows a diagram with the illustration of the effects of different surface properties of a component as a function of the constant surface of a counter component,

Figure 4 is a diagram with the exponential relationship between an adhesive force and a change in the surface finish of a component and

Figure 5 is a diagram showing the percentage distribution of surface properties of a component against an adhesive force of the component.

Embodiment of the invention

The left figure of Figure 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 in a memory under a pressure of from about 1600 bar. This fuel is supplied from a fuel tank of a high-pressure pump and this memory Fuel from the store becomes fuel as needed! taken from the ejectors via high pressure lines. The fuel injectors are for a

Actuated electrically and inject the fuel into a combustion chamber of the internal combustion engine. Such a fuel! Njektor has such a coupler module as part of the electrically controlled

Fuel metering on. 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 that have at least similar ignition properties

Diesel fuel to be replaced. 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-pervaded coupler module according to the left-hand illustration of 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 Figure 1 in a

enlarged scale shown. The two coupler pistons are guided, for example, with a guide clearance of 4 μm in the coupler sleeve 1. The

Coupler transmits an example applied by a piezoelectric actuator on the upper coupler piston 2 force on the lower

Coupling piston 2, which ultimately caused by the piezoelectric actuator

Movement on a valve piston for controlling a valve needle of the

Fuel! Njektors transfers. The valve needle is described by the

Device moved 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 test facility according to FIG. 2 has a module with a base part 3 which has a cylindrical recess into which a coupler piston 2 with its annular flange is inserted and clamped. The actual

Coupling piston 2 is surrounded by a discharge bell 4, whose 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 corresponds to 1.

Through a channel 5a, for example, a blended with biodiesel diesel fuel is fed into the discharge bell 4, along the fit between the coupler piston 2 and the bell 4 at the Führungsspiel5 thus formed with a guide game of preferably 5 μηι passed and through the

Channel 5b discharged in the base part 3. The guide game can be varied between 3 μηι and 14 μηι. To carry out the experiment, for example, in a timeframe of several hours, days or weeks mixed with biofuel diesel fuel or even concentrated biofuel o the pilot plant fed. To evaluate the experiment, the force

measured, with the withdrawal bell 4 must be raised to be detached from the captured in the base coupler piston 2. From the measured values obtained with trigger bells 4 (or optionally also coupler pistons 2), which have different surface qualities, 5 it is possible to determine which surface finish is suitable for example

different biofuels is optimized. The thus determined

Consequently, surface properties have the property that constituents of the biodiesel do not adhere or adhere poorly to this metallic surface. o FIG. 3 shows a diagram with the representation of the effects

different surface properties of a component (for example, the 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 the beginning clearly decreasing values of the individual

Surface properties increases the breaking force F up to a common limit F _gre nz only relatively small.

FIG. 4 shows, analogously to FIG. 3, a diagram with the exponential relationship between an adhesive force and a change in the FIG

Surface structure of a component and at different

Material component ratios 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 _gre nz there is a clear change in the breaking force as a function of the percentage of support.

FIG. 5 diagrammatically shows the different combinations of surface properties (surface property and surface structure) for three different modules MD1, MD2 and MD3. 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

Object of the present invention, this means that in the

balanced module MD1 minimizes the possibility of the effects of adhering deposits on the respective surface. In contrast, the possibility of the effect of the adhesion of deposits on the respective surface is very high in module MD3. -9-

Claims

Component, in particular a fuel injection system, having a surface,

characterized in that the surface has a structure which counteracts adhesion of a reactive medium, in particular a fuel, a biofuel, an additive and / or a fatty acid.

Component according to claim 1,

characterized in that the structure is a

Screw thread structure or a diamond structure is.

Component according to claim 1 or 2,

characterized in that the surface condition of an arithmetic mean roughness Ra is determined and the arithmetic mean roughness Ra has a value> = 0.2 μηι.

Component according to one of claims 1 to 3,

characterized in that the surface condition of an average roughness Rz is determined and the average roughness Rz has a value> = 2 μηι.

Component according to one of the preceding claims,

characterized in that the surface texture of a

Profile depth Pt is determined and the profile depth Pt has a value> = 2 μηι.

Component according to the preceding claims,

characterized in that the surface is ground,

laser-textured or hard-twisted.

7. Method for producing a component characterized in that a structure is applied to the surface of the component, which counteracts adhesion of a reactive medium, in particular a fuel, a biofuel, an additive and / or a fatty acid.

Method according to claim 7,

characterized in that a helical or diamond-shaped structure is applied to the surface of the component.

Method according to one of claims 7 or 8,

characterized in that the surface of the component is processed by a grinding process, a laser structuring process or a hard turning process.

Method according to claim 9,

characterized in that the grinding process a

Center grinding process or a Kreuzschleiffschleifprozess is.

Method according to one of claims 7 to 10,

characterized in that the structure of the surface is designed so that their nature of an arithmetic mean roughness Ra with a value> = 0.2 μηι and / or an average roughness Rz with a value> = 2 μηι and / or a profile depth Pt of Surface with a value> = 2 μηι is determined.

Method according to one of claims 7 to 1 1,

characterized in that, starting from an initial value with a first material carrying component Rmr, the material carrying component Rmr is reduced by up to 65% according to an Abbott curve of the surface of the component.