KR20020029383A - Fuel injection device for fuel internal combustion engines - Google Patents

Abstract

The present invention relates to a fuel injection device for an internal combustion engine, in which the fuel injection valve 9 comprises a push rod 21 operated by the injection valve member 14. The push rod 21 limits the control chamber 25 which can be supplied with high pressure fuel continuously and can be discharged into the discharge chamber 32 through the control valve 43 and the discharge channel 29. The control valve 43 includes valve members 42, 421, 422 operated by the piezo system 45. The valve members 42, 421, 422 together with the sheet edge 40 form a first sealing sheet 41, 411, 522 having a flat sheet.

Description

Fuel injection device for fuel internal combustion engines

The known device comprises a valve member operable by a piezo system, which seals or opens the control chamber to the discharge channel in the fuel injection valve. The sealing is through a conical sheet or spherical sheet formed in the valve member according to the embodiment. Due to this structure, when the valve member is raised from its sheet in the valve housing, the effect is that the hydraulically effective sheet diameter of the valve member becomes larger than its geometric sheet diameter. This results in the increased opening force provided by the piezo system in order for the valve member to be lifted from its sheet. The increased opening force reduces the stroke of the piezo system or limits the range of use of the hydraulic force-distance enhancer connected to the front. In the action of the conical or spherical sheet, the effect of the hydraulically effective sheet diameter of the enlarged valve member relative to the geometric sheet diameter is such that a flow channel having a constant length is formed between the valve member and the valve sheet when the valve member is raised from the sheet. This can be explained by the flow and throttle effects that occur when fuel flows from the control chamber into the discharge channel through the channel. However, if the valve member makes a constant minimum stroke, the effect no longer appears.

Another problem relates to the structural design of the fuel injection valve when the valve member seals the discharge chamber to the discharge tube connected to the discharge chamber and to the control chamber. In this case, the valve member forms an upper and lower sealing sheet together with the valve housing depending on the position, which sealing sheet is formed as spherical sheet or conical sheet respectively in the prior art. Since the valve housing is divided horizontally in two sealing sheet areas for manufacturing reasons and the valve member comprises a closing member assembled on the valve stem, the sealing sheet does not lie in a straight line when replacing from one sealing sheet to another sealing sheet. In order to prevent lateral forces from occurring in the valve member, a very complex and accurate manufacturing is required. This increases noise generation with increasing wear.

The present invention relates to a fuel injection device for an internal combustion engine according to the preamble of claim 1 as known from German Patent Publication No. 196 24 001.

1 is a schematic view of a fuel injection device according to the present invention comprising a high pressure accumulator and a fuel injection valve controlled by a control valve;

2 is an enlarged view of the fuel injection valve according to section A of FIG. 1;

3 and 4 are longitudinal cross-sectional views of a fuel injection valve modified with respect to FIG.

The fuel injection device for an internal combustion engine according to the present invention having the features of claim 1 has a hydraulically effective sheet diameter that is actually slightly larger than the geometric sheet diameter of the valve member when the valve member is raised from the sheet by the planar sheet used. It has the advantage of being large. Thus, the hydraulically effective sheet diameter earlier corresponds to the geometric sheet diameter of the valve member, and the diameter difference between the opening closed by the valve member and the diameter of the valve member in the valve sheet is smaller because the This is because on rise the very short flow distance of the pressure medium is formed in the valve seat, thereby reducing the flow or throttle effect which results in different effective sheet diameters. In addition, the planar sheet can be implemented very simply due to manufacturing techniques, since the tolerance requirements for the guide of the valve member in relation to the valve sheet are relatively small.

The aforementioned manufacturing problem with the divided valve housing and the lateral force acting on the valve member is avoided when forming the valve sheet as a flat sheet, since the closing member only has to be aligned by the valve sheet.

Another preferred embodiment of the fuel injection device for an internal combustion engine according to the invention is presented in the dependent claims.

In one preferred embodiment, the valve member interacts with the enlarged sheet edge in the valve sheet. The sheet edge can be implemented relatively simply by an inclined surface due to manufacturing techniques. In a particularly preferred embodiment, the hydraulically effective sheet diameter of the valve member is about the same as the geometric sheet diameter and is independent of the size or diameter of the valve member, especially at the height of the flat sheet.

It is also particularly desirable for the planar sheet to be formed on the side of the closure member facing the control chamber because the upper sheet is longer and more loaded and the conical sheet is tighter and more wear resistant than the planar sheet.

Hereinafter, with reference to the accompanying drawings an embodiment of the present invention will be described in detail.

A fuel injection device which enables large fluctuations in fuel injection at high injection pressures and low cost, in particular fuel injection with very precisely controllable injection timing and injection amount, is implemented by a so-called common-rail system. This provides a high pressure fuel source in a manner different from that given by conventional high pressure fuel injection pumps. However, the invention can be used not only in so-called common-rail systems, but also in fuel injection pumps. Of course, more preferred for common-rail systems.

1 is provided with a high pressure fuel accumulator 1 as a high pressure fuel source for a common-rail system. Fuel is supplied from the fuel storage tank 4 to the accumulator 1 by the high pressure fuel supply pump 2. The pressure in the high pressure fuel accumulator 1 is controlled via the electric control device 8 by the pressure control valve 5 and the pressure sensor 6. The control device 8 also controls the fuel injection valve 9.

The fuel injection valve 9 has a valve housing 11. The valve housing 11 has an injection hole 12 at one end thereof designed for assembly to an internal combustion engine. Discharge from the inside of the fuel injection valve 9 is controlled by the injection valve member 14. The injection valve member 14 is embodied in the embodiment as an elongated valve needle, the valve needle having a sealing surface 15 at one end thereof, the sealing surface 15 interacting with a valve seat lying therein. The valve needle is disposed in a pressure chamber 16 connected to the high pressure fuel accumulator 1 via a pressure tube 17 inside the valve housing 1. In the larger diameter portion of the pressure chamber 16, a compression spring 16 is arranged, which is axially fixed between the valve disc 20 and the valve housing 11, and the injection valve A force is applied to the member 14 in the closing direction. A push rod 21 is provided coaxially with respect to the compression spring 19. The push rod 21 is close to the valve disc 20 on the one hand and inserted into the guide hole 22 on the other hand, whereby its front face 23, which forms a movable wall, is closed of the guide hole 22. Together with the end forms a control chamber 25. A feed channel 26 extends into the control chamber 25, and a feed throttle 27 is disposed in the feed channel 26. The high pressure fuel from the pressure chamber 16 is fed into the control chamber 25 through the supply throttle 27.

The discharge channel 29 extends from the control chamber 25 from the front side opposite the push rod coaxially to the push rod 21. An outlet throttle 28 is disposed in the outlet channel 29. The discharge channel 29 extends into the discharge chamber 30 inside the valve housing 11. The discharge chamber 30 extends through the discharge tube 31 to the consumer side discharge chamber 32. The discharge chamber 32 may for example be a fuel storage tank 4.

As best seen in FIG. 2, the discharge chamber 30 includes an upper region 33 and a lower region 34 facing the control chamber 25. The discharge tube 31 branches on the side facing the feed channel 26 laterally from the upper region 33 which is smaller in diameter than the lower region 34. A protrusion or strip 35 protrudes into the lower region 34, and the inner wall 36 of the strip 35 is formed as an extension of the hole wall 37 of the upper region 33. Since the strip 35 has an inclined surface 39 on the side opposite the inner wall 36, the strip 35 is formed in a triangle in the longitudinal cross-sectional view shown in FIG.

The front of the strip 35 facing the discharge channel 29 forms a sheet edge 40, which, when interacting with the valve member 42, forms a first sealing sheet 41. The valve member 42 is part of the control valve 43 and the valve member 42 may be in the closed position or the open position by the piezo system 45.

The valve member 42 has a valve stem 46 and a closing member 47 connected to one end of the valve stem 46 and interacting with the seat edge 40. The valve stem 46 is disposed with radial play in the upper region 33 of the discharge chamber 30. The closure member 47 is formed in a hemispherical or spherical segment shape and has a flat sheet surface 48 facing the sheet edge 40. A valve stem 46 is connected to the sheet face 48. Thus, the first sealing sheet 41 is formed of the sheet face 48 and the sheet edge 40 as a planar sheet. The sheet face 48 of the closure member 47 protrudes the sheet edge 40 in diameter.

The convex face 49 of the closure member 47 opposite the sheet face 48, together with the sheet face 51 which engages at least partially positively with the surface 49, causes the discharge channel 29 to be discharged. In the region extending into the lower region 34 of 30, a conical sheet is formed as the second sealing sheet 52.

The clean fuel injection device operates as follows: Fuel is supplied from the fuel storage tank 4 into the high pressure fuel accumulator 1, preferably by a high pressure fuel supply pump 2 which is driven synchronously with the internal combustion engine. The pressure of the accumulator is set at a particularly constant value via the pressure control valve 5 and the pressure sensor 6. The value may vary from case to case. The fuel provided from the high pressure fuel accumulator 1 is supplied to a plurality of fuel injection valves 9 having the above-described structure.

When the valve member 42 of the control valve 43 is in the closed position shown, relatively high pressure is also maintained in the control chamber 25 due to the fuel supplied through the pressure tube 17. The pressure provides a closing force to the injection valve member 14 in addition to the compression spring 19 via the movable wall 23, so that the injection valve member 14 is in the closed position and held in this position. However, when the control valve 43 is open, the control chamber 25 may be discharged to the discharge chamber 32 through the discharge channel 29, the discharge chamber 30 and the discharge tube 31.

Since the first sealing sheet 41 is formed here as a planar sheet, from the sheet edge 40 to the upper region 33 from the lower region 34 of the discharge chamber 30 when the closing member 47 is raised. Only very short flow distances of fuel are formed. Thus, only a very small flow effect of raising the opening force of the piezo system 45 is seen. By specially designing the sheet edge 40 in the raised strip 35, the effect of the diameter difference between the closure member 47 and the upper region 33 in the region of the sheet face 48 is further reduced, This causes an additional positive effect on the required opening force of the piezo system 45.

Due to the weak pressure in the control chamber 25, the closing force of the compression spring 19 is insufficient when the closing member 47 rises from the sheet edge 40, and the injection valve member 14 causes the pressure of the valve member 42 to rise. Since the injection valve member 14 is held in the closed position against the high pressure fuel acting on the surface, the injection valve member 14 is in the open position. This causes the first injection process, so-called pre-injection, in the above-described embodiment in which the valve member 42 forms the second sealing sheet. When the valve member 42 is fully stroked, the face 49 of the closing member 47 forms the second sealing sheet 52 together with the sheet surface 51, so that fuel is discharged to the discharge chamber 32. Since the original high fuel pressure is again formed in the control chamber 25 because it cannot, the preliminary injection is finished.

When the valve member 42 moves again in the direction of the first sealing sheet 41, the second injection process, so-called main injection, is started. The start is made similar to the first injection process by the pressure drop in the control chamber 25 due to the discharge of fuel into the discharge chamber 32. When the sheet surface 48 of the valve member 42 is placed on the sheet edge 40 again while forming the first sealing sheet 41, the main injection ends. At this moment, the closing member 47 blocks the upper region 33 in the discharge chamber 30 with respect to the lower region 34 so that a high fuel pressure is immediately formed in the control chamber 25 again, and the pressure Makes the injection valve member 14 back to the closed position.

The embodiment according to FIG. 3 shows a multi-piece configuration of a valve housing having a lower portion 111 and an upper portion 112, which is actually implemented for manufacturing reasons. The valve stem 461 and the closing member 471 are also formed of separate, interconnected parts. The parts together form a valve member 421. In addition, since the strip 35 is omitted, the support surface for the first sealing sheet 411 is enlarged.

In FIG. 4, the closing member 472 of the valve member 422 is rotated 180 degrees compared to FIG. 3. For this reason, the conical sheet is formed in the upper first sealing sheet 412, and the planar sheet is formed in the lower second sealing sheet 522. Since the upper sealing sheet 412 is loaded longer and more than the lower sealing sheet 522 during operation of the fuel injection valve, the conical sheet provides advantages in terms of wear resistance and leakage loss.

The present invention is not limited to the above-described embodiment, and the members of the individual embodiments can be interchanged with each other.

Claims (10)

A high pressure fuel source (1), from which fuel is supplied to the fuel injection valve (9), the fuel injection valve (9) being an injection valve member for controlling at least one injection port (12) 14 and a control chamber 25, the control chamber 25 being defined by a movable wall 23, which wall is at least indirectly connected to the injection valve member 14, and the control chamber ( 25 is the supply channel 26 from the high pressure source, in particular the high pressure fuel source 1, designed by the first throttle 27, and the discharge channel 29 with a constant maximum discharge cross section for the discharge chamber 30. Fuel discharge from the control chamber 25 to the discharge vessel 32 is blockable by a valve member 42, 421, 422 having a valve seat 41, 411, 522, the valve member Is configured to be part of a control valve 43 operable by the piezo system 45, In the delay tolerance fuel injector, And the valve seat (41, 411, 522) is formed as a planar sheet. The method of claim 1, The planar sheet is opposite the control chamber 25 and the first area 34 of the discharge chamber 30 facing the flat surface 48 of the valve members 42, 421, 422 and the control chamber 25. A fuel injection device, characterized in that it is formed by a wall in the transition region between the second region (33) of the discharge chamber (30) that lies. The method of claim 2, And the wall is formed as a sheet edge (40) protruding into the first region (34) of the discharge chamber (30). The method of claim 3, wherein And the sheet edge (40) is formed in the strip (35). The method of claim 4, wherein Fuel injection device, characterized in that the strip (35) has an inclined surface (39). The method according to any one of claims 1 to 5, And the valve member (42, 421, 422) has a hemispherical or spherical segmented closing member (47, 471, 472). The method of claim 6, Faces 49 of the closure members 47, 471 opposite the valve seats 41, 411 form additional valve sheets 52 in the transition region between the discharge channel 29 and the discharge chamber 30. A fuel injector, characterized in that. The method of claim 1, The valve member 422 has a hemispherical or spherical segmental closing member 472, a valve sheet 522 formed as a planar sheet is disposed in the transition region between the discharge channel 29 and the discharge chamber 30, A face of the closing member 472 opposite the valve seat 522 may cause an additional valve sheet 412 to be added to the transition region from the first region 34 to the second region 33 of the discharge chamber 30. And the discharge chamber (30) is coupled to the discharge vessel (32). The method of claim 8, And the additional valve seat (412) is a conical sheet. The method according to any one of claims 6 to 9, And the valve member (421, 422) comprises a valve stem (461) and a closing member (471, 472) connected to the valve stem (461).