WO1998009069A1

WO1998009069A1 - Fuel injection valve for internal combustion engine

Info

Publication number: WO1998009069A1
Application number: PCT/DE1997/001187
Authority: WO
Inventors: Friedrich Boecking
Original assignee: Robert Bosch Gmbh
Priority date: 1996-08-29
Filing date: 1997-06-12
Publication date: 1998-03-05
Also published as: DE19634933B4; DE19634933A1

Abstract

The invention pertains to a fuel injection valve for internal combustion engine, of which the valve element (5) is mounted axially displaceable inside a bore within the valve body, includes at its end next to the combustion chamber a valve sealing surface with which it cooperates through the valve tapered fitting surface (9) at the bore closed end of the valve body, located next to the combustion chamber. The valve tapered fitting surface of said valve element (5) is parted into two areas of different cone angles, defines a valve sealing edge (19) on the partition line and has in its area at least one injection opening (23) connected downstream to the sealing edge (19). For a more precise manufacture of the sealing fitting part, the valve element (5) is provided with a shoulder (15) between the sealing surface areas (11, 13) of different cone angles.

Description

Fuel injection valve for internal combustion engines

State of the art

The invention is based on a fuel injection valve for internal combustion engines according to the preamble of claim 1. In such a fuel injection valve known from US Pat. No. 5,351,398, a piston-shaped valve member is guided axially displaceably in a bore in a valve body. The valve member has a conical valve sealing surface at its combustion chamber end, with which it interacts with a conical valve seat surface on the valve body, which is formed at the inwardly projecting end of the closed valve bore. The valve sealing surface on the valve member is divided into two areas with different cone angles, a circumferential sealing edge being formed on the transition edge between the two valve sealing surface areas, which sealingly abuts the valve seat surface and thus seals an upstream pressure chamber when the injection valve is closed. Downstream of this sealing edge is at least one injection opening which opens into the combustion chamber of the internal combustion engine to be supplied provided in the wall of the valve body which leads away from the valve seat surface.

The known fuel injection valve of the “perforated nozzle type” has the disadvantage, due to the manufacturing process, that the sealing edge often has tolerance deviations and

Has positional deviations, which in addition to inaccurate closing also form differently sized pressure application surfaces on the valve sealing surface, so that the individual injection valves open at different stroke speeds.

These relatively large tolerance deviations on the sealing edge have a particularly strong effect in injection systems working with a common high-pressure accumulation chamber (common rail), since the

There, the seat diameter tolerance is fully included in the tolerance chain of the injection quantity.

Advantages of the invention

The fuel injection valve according to the invention for internal combustion engines with the characterizing features of claim 1 has the advantage that the sealing edge on the valve member can be manufactured very precisely and is therefore only affected by a very small tolerance, which has an advantageous effect on the metering accuracy of the injection quantity. This is achieved in a structurally simple manner by providing a shoulder, by means of which the two valve sealing surface areas are separated from one another with different angles of inclination.

This shoulder can alternatively be cylindrical, curved or a combination of both. The axial extent of the paragraph is designed so that the through the paragraph and the subsequent damping cone damping space formed is retained despite the minimal tolerance on the seat diameter.

The sealing edge can be provided on the lower, combustion chamber side or at the upper end of the paragraph. The manufacture of a valve member designed in this way is advantageously carried out by subsequently grinding the valve sealing surface to the corresponding dimension, in which part of the axial shoulder is also removed.

The reduction in the seat diameter tolerance has a particularly advantageous effect when using the injection valve on common rail injection systems, the accuracy of which can be improved as a result. This is particularly necessary on injectors in which the closing force is transmitted to the valve member via a push rod, which limits a hydraulic working chamber on its end facing away from the valve member, which can be connected via a control valve to the high-pressure storage chamber of the common rail or to a relief chamber, to which in The common rail high pressure is constantly present at the opening of the pressure chambers acting on the valve member.

Since a quasi-static balance between the in

The contact surfaces of the valve element acting in the opening direction and the end face of the push rod acting in the closing direction are fully included in the force balance of the system in the force balance of the system on the seating surfaces on the valve element which take effect after the opening has started and can significantly influence the course of the opening stroke. Such a negative influence can be prevented by the precise manufacture of the sealing edge on the valve member which is possible according to the invention. Further advantages and advantageous embodiments of the subject matter of the invention can be found in the description, the drawing and the patent claims.

drawing

Six embodiments of the fuel injection valve according to the invention for internal combustion engines are shown in the drawing and explained in more detail in the following description.

1 shows a first exemplary embodiment of the fuel injection valve in a longitudinal section, in which the valve sealing surface areas are separated from one another by a cylindrical web, FIG. 2 shows an enlarged section of the valve seat area of FIG. 1, and FIG. 3 shows a simplified illustration of a second exemplary embodiment, in which the transition area between the valve sealing surface sections is chamfered and cylindrical, FIG. 4 shows a third embodiment shown in simplified form, in which the transition takes place via a ring shoulder and a cylindrical part, FIG. 5 shows a fourth embodiment in simplified representation, in which the transition takes place with a large radius 6 is a fifth

Embodiment in which the transition surface is designed as a combination of curvature and cylinder, Figure 7 shows a sixth embodiment in which the sealing edge cooperating with the seat surface is arranged at the upper end of the transition shoulder and Figure 8 shows the manufacture of the valve member according to the figures 1 and 2.

Description of the embodiments The fuel injection valve for internal combustion engines shown in FIG. 1 has a cylindrical valve body 1, which projects with its free lower end into a combustion chamber (not shown in more detail) of the internal combustion engine to be supplied. An axial blind bore 3 is provided in the valve body 1, in which a piston-shaped valve member 5 is guided so as to be axially displaceable. The valve member 5 has at its lower end near the combustion chamber a conical valve sealing surface 7, with which it cooperates to control an injection cross section with a conical valve seat surface 9 at the combustion chamber end of the valve body 1, which is formed at the inwardly projecting closed end of the bore 3.

Like FIG. 2, this is an enlarged view

1, the valve sealing surface 7 divided into an upper region 11 and a lower region 13, which have different cone angles and which are separated from one another by a shoulder 15, which in the first exemplary embodiment of FIGS. 1 and 2 is designed as a cylindrical web 17 is. In this case, a circumferential sealing edge 19 is formed at the transition between the shoulder 15 designed as a cylindrical web 17 and the lower region 13 of the valve sealing surface 7, which cooperates with the valve seat surface 9 and a pressure chamber 21 formed in the flow direction above the sealing edge 19 between the valve member 5 and the bore 3 seals. In the flow direction of the fuel below the sealing edge 19, at least one injection opening 23 is provided in the valve body 1, which opens from the valve seat surface 9 into the combustion chamber of the internal combustion engine. Between the sealing edge 19 and the upper end of the upper region 11 of the valve sealing surface 7, a space is formed between the valve member 5 and the valve seat surface 9, which during the closing movement of the valve member 5 as Damping chamber 24 acts, the axial length of paragraph 15 being designed so that the damping effect is retained despite the smallest possible axial extension. For the best possible damping effect, the upper boundary edge of the upper region 11 or the

Damping room 24 on the smallest possible distance from the wall of the valve seat surface 9.

The damping effect, which results in a lowering of the needle closing force, is achieved by building up a pressure cushion in the space 24, which builds up there at the high closing stroke speed of the valve member 5 (valve needle), the narrow gap between the valve member 5 and the valve seat surface 9 as a throttle point works.

At its end facing away from the valve seat 9, the valve member 5 projects via a pressure piece 25 into a spring chamber 27, into which a valve spring 29 is applied, which acts on the valve member 5 in the closing direction towards the valve seat 9, which acts on the valve member 5 via the pressure piece 25 and on the other hand is supported in a manner not shown on a stop fixed to the housing. This valve spring 29 assumes the closing function of the valve member 5 when the system is depressurized.

The high-pressure fuel supply to the valve seat 9 takes place via a pressure line 31 which penetrates the injection valve axially, which opens into the pressure chamber 21 and to which an injection line 33 is connected, which leads away from a high-pressure collecting space (common rail) 35 common to a plurality of injection valves, the opening direction on the valve member 5 acting pressure chamber 21 is constantly acted upon by the common rail high pressure. The high-pressure accumulator 35 is continuously filled with high-pressure fuel from a storage tank 43 by means of a high-pressure pump 39 via a delivery line 41.

To transmit the closing force to the valve member 5, the latter is axially coupled at its end facing away from the valve seat 9 to a push rod 51 which penetrates the spring chamber 27 and which projects with its end face 53 facing away from the valve member into a hydraulic working chamber 55. This working space 55 is connected via a control line 57 to the injection line 33, the

High-pressure fuel supply into the working space 55 can be controlled via a control valve 37 inserted into the control line 57, preferably a solenoid valve. The

Pressure relief of the working space 55 to initiate the valve member opening stroke movement takes place via a throttle point (not shown) into a relief space, but can alternatively also be effected via a control valve 37 designed as a 3/2 way valve. The precise design of the pressure application surfaces acting on the valve member 5 in the opening direction and the end face 53 on the push rod 51 are of great importance, since these have a significant influence on the opening time and the course of the opening of the valve member 5.

The exemplary embodiments 2 to 6 shown in simplified form in FIGS. 3 to 7 differ from the first exemplary embodiment shown in FIG. 2 only by the design of the shoulder 15 and the arrangement of the sealing edge 19, so that their description is limited to these details.

Paragraph 15 in the second exemplary embodiment shown in FIG. 3 is at the bottom cylindrical web 17 and an upper bevel 45 divided, which merges into the upper sealing surface area 11 to form an edge delimiting the damping space 24. The sealing edge 19 is formed at the lower end of the shoulder 15 or the web area 17 on the combustion chamber side.

In the third exemplary embodiment of the fuel injection valve according to the invention shown in FIG. 4, the transition from the cylindrical annular web 17 forming the shoulder 15 to the upper region 11 of the valve sealing surface 7 is designed as an annular shoulder 47, as a result of which the damping space 24 can be enlarged. The sealing edge 19 is again provided at the lower end of the web 17, at its transition to the lower region 13 of the valve sealing surface 7.

FIG. 5 shows a fourth exemplary embodiment, in which the shoulder 15 between the upper region 11 and the lower region 13 of the valve sealing surface 7 of the valve member 5 is curved inwards with a large radius 49 in the direction of the valve member axis. The sealing edge 19 is arranged at the lower end of the curved shoulder 49, at the transition to the lower sealing surface area 13.

The fifth exemplary embodiment shown in FIG. 6 is a combination of FIGS. 2 and 5, the shoulder 15 now being formed in its upper region by a curved surface 49 starting from the upper sealing surface region 11, which merges into a cylindrical section 17 in the lower region, which extends to the lower sealing surface area 13 near the combustion chamber. The sealing edge 19 is arranged at the lower end of the shoulder 15, at the transition between the cylindrical web 17 and the sealing surface area 13. The sixth shown in Figure 7

Exemplary embodiment, paragraph 15 is designed analogous to Figure 5 as a curved surface 49 with a large radius. However, the sealing edge 19 is now arranged at the upper end of the shoulder 15, at the transition between the curved surface 49 and the upper sealing surface region 11. However, the angle difference between the valve seat surface 9 and the sealing surface area 11 on the valve member 5 is still sufficiently large to form an effective damping space 24.

FIG. 8 shows a production possibility of the first exemplary embodiment of the fuel injection valve shown in FIG. 2. The valve member 5 is first preformed with a relatively long cylindrical web 17 and an oversize at the lower sealing surface area 13. Then the lower sealing surface 13 is ground to the finished size, at the same time the cylindrical webs 17 are shortened, so that the sealing edge 19 that is produced can be manufactured very precisely.

With the fuel injection valve for internal combustion engines according to the invention, it is thus possible in a structurally simple manner to manufacture the sealing seat on the valve to an accuracy of approximately 3 μm without having to do without the damping space, which considerably improves the metering accuracy on the injection valve. The formation according to the invention of a shoulder between two sealing surface areas on the valve member on injection valves of the blind hole and seat hole type is possible.

Claims

Expectations

1.Fuel injection valve for internal combustion engines with a valve member (5) which is axially displaceable in a bore (3) of a valve body (1) and which has at its end facing the combustion chamber of the internal combustion engine a conical valve sealing surface (7) with which it is connected to a conical valve seat surface ( 9) interacts at the closed end of the bore (3) of the valve body (1) on the combustion chamber, the conical valve sealing surface (7) on the valve member (5) being divided into two areas having different cone angles, at the transition of which a valve sealing edge (19) is formed, and with at least one injection opening (23) in the region of the valve seat surface (9) which adjoins the sealing edge (19) downstream, characterized in that between the valve sealing surface regions (11, 13) each having a different cone angle, a shoulder (15) on the valve member (5) is provided.

2. Fuel injection valve according to claim 1, characterized in that the shoulder (15) is designed as a cylindrical ring web (17). (Fig. 3,4,6)

3. Fuel injection valve according to claim 1, characterized in that the shoulder (15) is designed as an inwardly curved surface (49). (Fig.7)

4. Fuel injection valve according to claim 1, characterized in that the shoulder (15) is initially designed as a curved surface (49) and then continues in the flow direction following over a cylindrical portion (17). (Fig. 6)

5. Fuel injection valve according to claim 1, characterized in that the sealing edge (19) is arranged downstream at the lower end of the shoulder (15) at its transition to the lower valve sealing surface area (13).

6. Fuel injection valve according to claim 1, characterized in that the sealing edge (19) is arranged upstream at the upper end of the shoulder (15) at its transition to the upper valve sealing surface area (11).

7. Fuel injection valve according to claim 1, characterized in that the valve member (5) with its outer surface between the sealing edge (19) and an upper sealing surface region (11) delimiting transition edge to the cylindrical stem of the valve member (5), one

Damping space (24) in the valve seat cone (9) of the valve body (1) limited.

8. Fuel injection valve according to claim 1, characterized in that the injection valve via a

Injection line (33) is connected to a high-pressure collection chamber (35), from which all the injection lines (33) of the individual injection valves lead away and which is filled with high-pressure fuel by a high-pressure pump (39).

9. Fuel injection valve according to claim 8, characterized in that the valve member (5) is acted upon in the closing direction by a push rod (51) whose end face remote from the valve member (53) protrudes into a working space (55) via a controllable control line (57 ) can be connected to the high-pressure collecting space (35).

10. A method of manufacturing a Kraf fuel injection valve according to claim 1, characterized in that the valve member (5) is initially made with an oversize at the lower valve sealing surface area (13) and with an axially long shoulder (15) and that the oversize at the lower valve sealing surface area (13) is abraded and reduced to paragraph (15) to the desired size. (Fig. 8)