WO2007073968A1 - Fuel injector for an internal combustion engine, and method of producing a control valve for a fuel injector - Google Patents

Abstract

A fuel injector (10) for an internal combustion engine comprises a nozzle needle (16) which defines a control space (60) by means of a control surface (64). Furthermore, a control valve (32) is provided which can connect the control space (60) to a low-pressure region (52). It is proposed that the control valve (32) be completely integrated into the fuel injector (10).

Description

title

Fuel injector for an internal combustion engine, and method for producing a control valve for a Kraftstoffini ector

description

State of the art

The invention relates to a fuel injector for an internal combustion engine according to the preamble of claim 1. The invention further relates to a method for producing a

Control valve for a fuel injector according to the preamble of the independent claim.

From the market, common rail fuel injectors are known. These are used, for example, in internal combustion engines for motor vehicles. In such injection systems, the fuel is conveyed from a high-pressure pump into a high-pressure fuel rail ("rail") to which a plurality of fuel injectors are connected, which inject the fuel directly into a respective combustion chamber assigned to them.

For controlling a fuel injector such has a magnetically actuated control valve, which is mounted laterally or above the fuel injector at its end remote from the combustion chamber. When the solenoid valve is open, a control chamber, which is delimited by a nozzle needle of the fuel injector, connected to a low pressure region, whereby the pressure in the control chamber drops, which in turn leads to an opening of the nozzle needle. As a valve element of the control valve is usually a valve ball is used.

Object of the present invention is to provide a fuel injector, which is compact and inexpensive and has a long life. In addition, the injection should be able to be controlled very accurately. Disclosure of the invention

This object is achieved by a fuel injector with the features of claim 1. Another possible solution is given in the manufacturing method mentioned in the independent claim. Advantageous developments of the inventions are mentioned in subclaims. Important features of the invention are further set forth in the description and the drawing. It should be noted at this point that the features mentioned may also be essential for the invention in completely different combinations, without any explicit mention being made hereof.

Advantages of the invention

By integrating the control valve in the fuel injector, it is possible to minimize the distance between the control chamber and an injection nozzle of the fuel injector. This in turn allows the use of a very short, low-yielding nozzle needle or a short, acting on the nozzle needle closing piston, which allows direct control of the injection process. By integrating the control valve in the fuel injector this builds compact overall. In addition, the previously accumulated at the end remote from the combustion chamber of the fuel injector mass accumulation is reduced or avoided altogether, which reduces the load of the fuel injector due to engine vibrations. Moreover, as a result of the fact that no control valve is present any more at the projecting end of the fuel injector, the degrees of freedom for the arrangement of a high-pressure connection and a low-pressure connection are greater.

The term of the complete integration of the control valve in the fuel injector is understood to mean that the control valve including the valve element and actuating actuator lies completely within the housing of the fuel injector.

Due to the integration of the control valve in the fuel injector, it is possible to integrate a high-pressure fuel accumulator, which is connected to the control chamber, also in the fuel injector. A corresponding high-pressure fuel accumulator in the sense of a "common rail" to which all fuel injectors of the internal combustion engine are therefore no longer required. As a result, a cost saving is achieved and simplifies the installation of the fuel injector according to the invention. Due to the smaller distance between the control chamber and the volume of the fuel high-pressure accumulator, on the one hand, strong pressure drops to the beginning of an injection are avoided, and on the other hand, the high-pressure fuel accumulator serves as a damping volume at the end of an injection. Overall, this pressure oscillations are reduced in the high-pressure fluid system and thus reduces the mechanical stress on high pressure-loaded components of the fuel injector.

To fully integrate the control valve in the fuel injector is a

Miniaturization of the control valve required. This can for example be achieved in that the control valve has a multi-part body, which comprises a valve needle receiving a valve body and a partially plate-shaped sealing element with a sealing seat for the valve needle. As a result, an internal sealing seat and a corresponding internal processing of the sealing seat is avoided. Instead, the sealing seat is accessible from the outside and can be manufactured easily and in spite of small dimensions with high precision.

It is particularly preferred if the valve body and the sealing element are made of a one-piece blank by cutting. For example, first the blank can be pretreated, for example, subjected to a heat treatment, then the separation of the blank in a valve body and a sealing element, then a valve needle guide are incorporated on the sealing element of the sealing seat and in the valve body, and finally valve body and sealing element on the Separation point reassembled. This allows a very high positioning accuracy between the valve body and sealing element can be achieved in the installed position. The use of positioning pins or centering sleeves can be dispensed with. A good fluid seal even at high pressures is thus also made possible with the miniaturized control valve according to the invention.

If the separation of the blank in the valve body and sealing element by wire erosion, special positioning can be realized on the sealing element, which allow precise positioning of the sealing element to the valve body. If the separation is done, for example, by breaking, by initially introduced into the blank a lateral notch and at this the blank is then broken, the fracture surfaces are sufficient for positioning of the sealing element relative to the valve body.

If the control valve has a multi-part body and thus the sealing seat is easily accessible for processing, different particularly advantageous seat geometries can be realized: For example, a flat seat can be realized in which an undercut is present on the valve needle with a virtually burr-free sealing edge. The corresponding sealing seat on the sealing element is made flat. But it is also possible to realize a spherical shell seat. In this case, no undercut is present on the valve needle, but a vertical groove. Also possible is a concave configuration of this area of

Valve needle. In the sealing element a spherical shell-shaped seat is introduced. This has the advantage that axial tolerances can be compensated, which leads to a particularly high tightness of the control valve in the closed state.

drawings

Hereinafter, particularly preferred embodiments of the present invention will be explained in more detail with reference to the accompanying drawings. In the drawing show:

Figure 1 is a partially sectioned view of a fuel injector;

Figure 2 is an enlarged view of a portion II of the fuel injector of FIG

1;

Figure 3 is an enlarged and partially sectioned view of a portion of a first embodiment of a control valve of the fuel injector of Figure 1;

Figure 4 is a view similar to Figure 3 of a second embodiment;

Figure 5 is a perspective view of a first embodiment of a

Sealing element of a control valve of the fuel injector of Figure 1; Figure 6 is a view similar to Figure 5 of a second embodiment; and

Figure 7 is a side view of a blank for the production of a valve body and a

Sealing element of a control valve of the fuel injector of Figure 1.

Description of the embodiments

In FIG. 1, a fuel injector for an internal combustion engine bears the reference numeral 10 as a whole. It serves to inject fuel into a combustion chamber 12 directly assigned to it, which is indicated in FIG. 1 only by a dot-dash line. The injector includes one

Nozzle body 14, in which a nozzle needle 16 and acting on this closing piston 17 is received axially movable. At the projecting into the combustion chamber 12 end of the nozzle body 14 fuel outlet channels 18 are present and a housing-side valve seat (without reference numeral), with which the nozzle needle 16 cooperates.

The nozzle needle 16 has a conical pressure surface 20, the hydraulic force results in the opening direction of the nozzle needle 16 and which defines a pressure chamber 22. This is connected via a high pressure passage 24 with a large-volume fuel high-pressure accumulator 26, which is arranged in a housing member 28 of the fuel injector 10, which is located at the opposite end of the combustion chamber 12 of the fuel injector 10. The fuel high pressure accumulator 26 is connected to a high pressure port of the fuel injector 10 not shown in the drawing. Via a spring 30, which is supported on the nozzle body 14, the nozzle needle 16 is acted upon in the closing direction.

In the fuel injector 10, as is apparent in particular from Figure 2, a control valve 32 is integrated, with which the nozzle needle 16 can be actuated. The control valve 32 comprises a sealing element 34 adjoining the nozzle body 14 and designed as a sealing plate and a valve body 36 adjoining the sealing element 34. The housing element 28 in turn adjoins the housing element 28 in which the high-pressure fuel accumulator 26 is present. In the valve body 36, a stepped recess 38 is present, whose longitudinal axis is aligned in the present embodiment with that of the high-pressure fuel reservoir 26 and slightly offset from the longitudinal axis of the nozzle needle 16, which, however, extends parallel to the longitudinal axis of the nozzle needle 16. An adjacent to the sealing element 34 portion 38 a of the recess 38, which has a relatively small diameter, serves as a guide for a valve needle 40 of the control valve 32. This is connected at its upper in Figures 1 and 2 with an anchor plate 42, which to a electromagnetic actuator 44 belongs. In an upper area 38b of the larger-diameter recess 38 in FIGS. 1 and 2, an electromagnetic coil 45 of the electromagnetic actuator 44 is accommodated. A spring 46 is supported by a spring plate 48 on the housing member 28 and acts on the armature plate 42 and attached to this valve needle 40 in the closing direction of the coil 45 away.

The lower end of the valve needle 40 in FIGS. 1 and 2, when the control valve 32 is closed, works in a manner further explained in more detail below with a sealing seat 50 which is formed on the upper side of the sealing element 34. From the sealing seat 50, a discharge channel 52 leads to a low-pressure connection of the fuel injector 10 which is not visible in FIGS. 1 and 2. The region 38a of the recess 38 in the valve body 36 located in FIGS. 1 and 2 above the sealing seat 50 has a direct proximity to the sealing seat 50 Extension, through which an inflow space 54 is formed. This is connected via a present in the sealing element 34 and a channel 56 Abströmdrossel 58 with a control chamber 60 which is incorporated into the underside of the sealing element 34 in the region of the upper end of the nozzle needle 16. The control chamber 60 is connected via an inflow throttle 62 with the high pressure passage 24. The control space 60 delimiting the top of the closing piston 17 forms a control surface 64 with acting in the closing direction of the nozzle needle 16 hydraulic force resultant.

As is apparent from Figure 3, the sealing seat 50 may be formed on the sealing element 34 as a flat seat, whereas on the valve needle 40, an undercut 66 is present, which cooperates with the flat seat 50. Alternatively, as shown in Figure 4, the valve needle 40 have no undercut, but a perpendicular to the longitudinal axis of the valve needle 40 recess 68. The sealing seat is in turn spherical shell-shaped, which allows axial tolerances, ie an angular offset of the longitudinal axis of the valve needle 40 relative to the Seal seat 50, compensate. It can be seen from FIG. 1 that the control valve 32 is completely integrated into the fuel injector 10. In the miniaturization of the control valve 32 according to the invention 32 very close tolerances must be adhered to to ensure reliable operation of the control valve. With a diameter of the valve needle 40 of typically 1.5 mm, it is above all necessary that the positioning of the valve body 36 relative to the sealing element 34 or the positioning of the recess 38 to the sealing seat 50 be very precise. Therefore, it is proposed in the present case that the sealing element 34 and the valve body 36 are made of an initially one-piece blank. This is, in order to have the required strength, a pretreatment, for example, subjected to a heat treatment. The corresponding hardness distortion of the blank, when the blank is, for example, a cylindrical part, symmetrical.

Before the heat treatment, the recess 38 and the discharge channel 52 are introduced into the blank. After the heat treatment, the blank is separated into the valve body 36 and the sealing member 34, for example, by wire erosion. The area of the sealing seat 50 on the sealing element 34 is now easily accessible, so that the sealing seat 50 can be manufactured with high accuracy on the sealing element 34. Due to the symmetrical hardness distortion in the sealing element 34 and the valve body 36, the two parts can then be reassembled at the resulting separation point with a very high positioning accuracy. The use of positioning pins or on a centering can be dispensed with. Like from the

5 and 6, a fixing or positioning section in the form of notches 70a or in the form of a lateral bevel 70b can be introduced on the sealing element 34, by means of which a positioning of the sealing element 34 relative to the valve body 36 is ensured in a simple manner. As can be seen from FIG. 7, sealing element 34 and valve body 36 can also be produced from the one-piece blank by breaking, wherein the break is introduced via a defined notch 72. If the blank (reference numeral 74 in FIG. 7) is broken so that the sealing element 34 and the valve body 36 arise therefrom, the fracture surfaces are sufficient for positioning.

The fuel injector 10 shown in FIG. 1 operates as follows: Fuel is pumped into the high-pressure fuel accumulator 26 via a high-pressure fuel pump (not shown in FIG. 1). Thus, the high pressure is also present in the pressure chamber 22 and via the inflow throttle 62 in the control chamber 60 via the high-pressure passage 24. In this initial state, in that of Fuel injector 10 no fuel is discharged, the control valve 32 is closed, that is, that the coil 45 is de-energized and the valve needle 40 is pressed by the spring 46 to the seat 50. Due to the small diameter of the valve needle 40 of only 1.5 mm, in order to obtain the necessary surface pressure on the sealing seat 50, the spring force exerted by the spring 46 may be comparatively small. This in turn has the positive effect that coil 45 and armature 42 and thus the entire control valve 32 build comparatively small.

The connection from the control chamber 60 to the discharge channel 52 is interrupted. The forces acting on the nozzle needle 16 in the closing direction due to the spring 30 and due to the hydraulic force on the control surface 64 are greater in this state than acting on the pressure surface 20 in the opening direction of the nozzle needle 16 hydraulic force.

For injection, the coil 45 is energized. Thus, the valve needle 40 lifts off from the sealing seat 50, so that fuel can flow out of the control chamber 60 via the outflow throttle 58 to the outflow channel 52 and on to the low-pressure connection, not shown. As a result, the pressure in the control chamber 60 and the force acting on the control surface 64 in the closing direction hydraulic force decrease until the nozzle needle 16 opens and fuel can flow out of the fuel outlet channels 18. For completion of a fuel injection, the coil 45 is de-energized, whereby the valve needle 40 is pressed by the spring 46 against the sealing seat 50 and the connection between the control chamber 60 and outflow 52 is interrupted. Thus, the pressure in the control chamber 60 can rise again due to the fuel flowing in via the inflow throttle 62, which leads to an increase in the hydraulic force acting on the control surface 64 in the closing direction. If the forces acting in the closing direction on the nozzle needle 16 predominate, this again moves against its housing-side sealing seat (without reference numeral), so that the delivery of fuel through the fuel outlet channels 18 is ended.

It can be seen from FIG. 1 that the integration of the control valve 32 into the fuel injector 10, specifically in its axially central region, opens up the possibility of making the closing piston 17 comparatively short. This is therefore relatively stiff, which allows a direct control of the injection process. The integration of the control valve 32 in the axial center of the fuel injector 10 space is created for the accommodation of the fuel high-pressure accumulator 26 also in the fuel injector 10. The distance between High-pressure fuel storage 26 and the fuel outlet channels 18 is correspondingly short, whereby pressure oscillations are damped. It can also be seen from FIG. 1 that the fuel injector 10 shown has no "mass accumulation" at its upper end in FIG. 1, which leads to a lower oscillation stress of the fuel injector 10 during its operation.

Claims

claims A fuel injector (10) for an internal combustion engine, comprising a nozzle needle (16) defining a control space (60) with a control surface (64) and a control valve (32) defining the control space (60) with a low pressure area (52). can connect, characterized in that the control valve (32) is completely integrated in the fuel injector (10). 2. Fuel injector (10) according to claim 1, characterized in that a high-pressure fuel accumulator (26), which is connected to the control chamber (60), in the fuel injector (10) is integrated. 3. Fuel injector (10) according to any one of claims 1 or 2, characterized in that the control valve (32) has a multi-part main body, which is a valve needle (40) partially receiving valve body (36) and a sealing element (34) having a sealing seat (50) for the valve needle (40). 4. fuel injector (10) according to claim 3, characterized in that the valve body (36) and the sealing element (34) are made of a one-piece blank (74) by cutting. 5. Fuel injector (10) according to claim 4, characterized in that the sealing element (34) has at least one positioning portion (70) produced during the separation for positioning the sealing element (34) relative to the valve body (36). 6. Fuel injector (10) according to any one of claims 3 to 5, characterized in that the control valve (32) as a sealing seat (50) for the valve needle (40) has a flat seat or a Having spherical shell seat. 7. A method for producing a control valve (32) for a fuel injector (10) according to any one of the preceding claims, characterized in that a valve body (36) and a sealing element (34) of the control valve (32) are produced by a. a blank (74) is pretreated, b. the blank (74) is separated into a valve body (36) and a sealing element (34), c. on the sealing element (34) a sealing seat (50) and in the valve body (36) a valve needle guide (38 a) is incorporated, d. Valve body (36) and sealing element (34) are reassembled at the separation point. 8. The method according to claim 7, characterized in that in step b, the blank (74) is separated by breaking or wire EDM.