EP2003331A1

EP2003331A1 - Valve assembly for an injection valve and injection valve

Info

Publication number: EP2003331A1
Application number: EP07011514A
Authority: EP
Inventors: Antonio Paciolla; Federico Zimmitti
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2007-06-12
Filing date: 2007-06-12
Publication date: 2008-12-17

Abstract

Injection valve (10) and valve assembly (14) for an injection valve (10), comprising a valve body (20) including a central longitudinal axis (L), the valve body (20) comprising a cavity (24) forming an inner wall (42), the cavity (24) comprising a fluid outlet portion (28) with a seat area (44) being part of the inner wall (42), a valve needle (22) axially movable in the cavity (24), the valve needle (22) preventing a fluid flow through the fluid outlet portion (28) in a closing position and releasing the fluid flow in a fluid flow direction (F) through the fluid outlet portion (28) in further positions, the valve needle (22) comprising a needle seat (46), the needle seat (46) and the seat area (44) forming an injection nozzle (29), and a collar (40) being coupled to an outer surface (48) of the valve body (20) and extending in axial direction of the valve body (20) relative to the central longitudinal axis (L), wherein the collar (40) is arranged circumferentially relative to the central longitudinal axis (L) to encircle the injection nozzle (29).

Description

The invention relates to a valve assembly for an injection valve and an injection valve for a combustion chamber of a combustion engine.
Injection valves are in widespread use, in particular for internal combustion engines where they may be arranged in order to dose the fluid into an intake manifold of the internal combustion engine or directly into the combustion chamber of a cylinder of the internal combustion engine.
Injection valves are manufactured in various forms in order to satisfy the various needs for the various combustion engines. Therefore, for example, their length, their diameter and all the various elements of the injection valve being responsible for the way the fluid is dosed may vary in a wide range. In addition to that, injection valves may accommodate an actuator for actuating a needle of the injection valve, which may, for example, be an electromagnetic actuator or piezoelectric actuator.
In order to enhance the combustion process in view of the creation of unwanted emissions, the respective injection valve may be suited to dose fluids under very high pressures. The pressures may be in case of a gasoline engine, for example, in the range of up to 200 bar and in the case of a diesel engine in the range of up to 2000 bar.
The object of the invention is to create a valve assembly for an injection valve and an injection valve which is simply to be manufactured and which facilitates a reliable and precise function.
This object is achieved by the features of the independent claim. Advantageous embodiments of the invention are given in the sub-claims.
According to a first aspect the invention is distinguished by a valve assembly for an injection valve, comprising a valve body including a central longitudinal axis, the valve body comprising a cavity forming an inner wall, the cavity comprising a fluid outlet portion with a seat area being part of the inner wall, a valve needle axially movable in the cavity, the valve needle preventing a fluid flow through the fluid outlet portion in a closing position and releasing the fluid flow in a fluid flow direction through the fluid outlet portion in further positions, the valve needle comprising a needle seat, the needle seat and the seat area forming an injection nozzle, and a collar being coupled to an outer surface of the valve body and extending in axial direction of the valve body relative to the central longitudinal axis, wherein the collar is arranged circumferentially relative to the central longitudinal axis to encircle the injection nozzle.
This has the advantage that a good protection of the injection nozzle against mechanical damage can be obtained. Furthermore, the construction of the collar can be very simple and consequently, it is possible to obtain low costs for the collar.
In an advantageous embodiment of the invention, the collar is circumferentially closed. This has the advantage that a good protection of the injection nozzle against mechanical damage in all directions is possible.
In a further advantageous embodiment of the invention the radial extension of the collar is decreasing in the fluid flow direction. This has the advantage that the shape of the collar is well-fitted in view of the direction of the fluid spray and the fluid spray can leave the injection valve undisturbed and with the desired pattern. Furthermore, the collar can be shaped mechanically robust. Additionally, the collar can be simply manufactured.
In a further advantageous embodiment of this invention, the valve needle has an axial valve needle end and the collar has an axial collar end, and the axial collar end ranges at least to a common plane comprising the axial valve needle end and extending in a radial direction relative to the central longitudinal axis. This has the advantage that a secure protection of the injection nozzle and the axial valve needle end against mechanical damage is possible.
In a further embodiment of the invention, the valve body and the collar are formed as a one-part element. By this a good coupling between the collar and the valve body is possible.
According to a second aspect the invention is distinguished by an injection valve for a combustion chamber of a combustion engine with a valve assembly according to the first aspect of the invention.
Exemplary embodiments of the invention are explained in the following with the aid of schematic drawings. These are as follows:

Figure 1, an injection valve in a longitudinal section view,
Figure 2, a valve assembly of the injection valve partially in a side view, partially in a longitudinal section view, and
Figure 3, a collar and a valve needle of the valve assembly in an enlargement of detail III of figure 2.

Elements of the same design and function that appear in different illustrations are identified by the same reference characters.
An injection valve 10 (figure 1) that is used as a fuel injection valve for an internal combustion engine, comprises a housing 12, a valve assembly 14 and an actuator unit 16.
The housing 12 has a tubular shape. The actuator unit 16 is inserted into the housing 12 and comprises a piezo actuator, which changes its axial length depending on a control signal applied to it. The actuator unit 16 may, however, also comprise another type of actuator, which is known to a person skilled in the art for that purpose. Such an actuator may be, for example, a solenoid.
The valve assembly 14 comprises a valve body 20 with a central longitudinal axis L and a cavity 24 which is axially led through the valve body 20. On one of the free ends of the cavity 24, a fluid outlet portion 28 is formed, which is closed or open depending on the axial position of a valve needle 22. The injection valve 10 further has a fluid inlet portion 26 which is arranged in the housing 12 and which is hydraulically coupled to the cavity 24 and a not shown fuel connector. The fuel connector is designed to be connected to a high pressure fuel chamber of an internal combustion engine, the fuel is stored under high pressure, for example, under the pressure of about 200 bar.
The valve body 20 has a valve body spring rest 32 and the valve needle 22 comprises a valve needle spring rest 34, both spring rests 32, 34 supporting a spring 30 arranged between the valve body 20 and the valve needle 22.
The injection valve 10 is of an outward opening type. In an alternative embodiment the injection valve 10 may be of an inward opening type. Between the valve needle 22 and the valve body 20 a bellow 36 is arranged which is sealingly coupling the valve body 20 with the valve needle 22. By this a fluid flow between the cavity 24 and a chamber 38 is prevented. Furthermore, the bellow 36 is formed and arranged in a way that the valve needle 22 is actuable by the actuator unit 16.
Figure 2 shows a sectional view of the valve assembly 14 with a collar 40. Figure 3 shows the collar 40 and the valve needle 22 in a longitudinal section in an enlarged detailed view.
As can be best seen in figures 2 and 3 the cavity 24 of the valve body 20 forms an inner wall 42. In the area of the fluid outlet portion 28 a seat area 44 which is part of the inner wall 42 of the cavity 24 and a needle seat 46 of the valve needle 22 is forming an injection nozzle 29.
The collar 40 is arranged on an outer surface 48 of the valve body 20. In a first embodiment (figure 1) the collar 40 and the valve body 20 are separate parts. The collar 40 is coupled to the valve body 20 by well-known processes, for example by a press-fitting process.
In a further embodiment of the invention as shown in the Figures 2 and 3 the collar 40 is in one part with the valve body 20. This has the advantage that the collar 40 can be manufactured together with the valve body 20. Furthermore, a good coupling between the valve body 20 and the collar 40 can be obtained.
The collar 40 is extending in a direction of the longitudinal axis L and the collar 40 is surrounding the injection nozzle 29 and parts of the valve needle 22. By this the injection nozzle 29 can be protected against mechanical damage, in particular during the assembly of the injection valve 10 into the internal combustion engine.
Preferably, the collar 40 is circumferentially closed so that the injection nozzle 29 can be protected against mechanical damages in all radial directions, in particular during the assembly of the injection valve 10 into the internal combustion engine. In a further embodiment, the collar 40 can have interruptions in circumferential direction.
The embodiment of the collar 40 of the figures 2 and 3 shows that the radial extension of the collar 40 decreases in a fluid flow direction F. As a fluid spray 54 which can leave the injection valve 10 via the injection nozzle 29 has a direction component in a radial direction R relative to the longitudinal axis L, this shape of the collar 40 makes it possible that the fluid spray 54 remains undisturbed by the collar 40 but enables the protection of the injection nozzle 29 against mechanical damage in a secure manner without changing the maximum of the outer diameter of the valve body 20. Furthermore, this design of the collar 40 results in that the collar 40 is mechanically very robust.
The valve needle 22 has an axial valve needle end 50. The collar 40 has an axial collar end 52. In the embodiment of the Figures 2 and 3 the axial valve needle end 50 and the axial collar 52 are arranged in a common plane P which extends in the radial direction R relative to the central longitudinal axis L. By this the injection nozzle 29 as well as the valve needle 22 can be protected against damage during the process of assembling the injection valve 10 with the internal combustion engine. Alternatively, the collar 40 extends beyond the axial valve needle end 50 in the fluid flow direction F.
In the following, the function of the injection valve 10 will be described:
The fuel is led from the fluid inlet portion 26 in the housing 12 to the cavity 24 of the valve body 20 and then to the fluid outlet portion 28.
The valve needle 22 prevents a fluid flow through the fluid outlet portion 28 in the valve body 20 in a closing position of the valve needle 22. Outside of the closing position of the valve needle 22, the valve needle 22 enables the fluid flow through the fluid outlet portion 28 in the fluid flow direction F.
In the case that the actuator unit 16 has a piezoelectric actuator, the piezoelectric actuator may change its axial length if it gets energized in an expansion duration of some micro-seconds. By changing its length the actuator unit 16 may effect a force on the valve needle 22. By this the valve needle 22 is able to move in axial direction out of the closing position. Outside of the closing position of the valve needle 22 there is a gap between the seat area 44 of the valve body 20 and the needle seat 46 of the valve needle 22 at an axial end of the injection valve 10 facing away from of the actuator unit 16. The gap forms the injection nozzle 29.
The spring 30 can force the valve needle 22 via the valve needle spring rest 34 towards the actuator unit 16. In the case when the actuator unit 16 is de-energized the actuator unit 16 shortens its length. By this the spring 30 can force the valve needle 22 to move in axial direction in its closing position. It is depending on the force balance between the force on the valve needle 22 caused by the actuator unit 16 and the force on the valve needle 22 caused by the spring 30 whether the valve needle 22 is in its closing position or not.
Outside of the closing position of the valve needle 22, the fluid flows through the injection nozzle 29 to form the fluid spray 54. As the radial extension of the collar 40 is decreasing in the fluid flow direction thereby forming a conical-shaped inner wall 56 of the collar 40 the fluid spray 54 can leave the injection nozzle 10 without touching the collar 40. This enables that the collar 40 can protect the injection nozzle 29 against mechanical damages in particular during the process of assembling the injection valve 10 to the internal combustion engine without disturbing the desired pattern of the fluid spray 54.

Claims

Valve assembly (14) for an injection valve (10), comprising
- a valve body (20) including a central longitudinal axis (L), the valve body (20) comprising a cavity (24) forming an inner wall (42), the cavity (24) comprising a fluid outlet portion (28) with a seat area (44) being part of the inner wall (42),

- a valve needle (22) axially movable in the cavity (24), the valve needle (22) preventing a fluid flow through the fluid outlet portion (28) in a closing position and releasing the fluid flow in a fluid flow direction (F) through the fluid outlet portion (28) in further positions, the valve needle (22) comprising a needle seat (46), the needle seat (46) and the seat area (44) forming an injection nozzle (29), and

- a collar (40) being coupled to an outer surface (48) of the valve body (20) and extending in axial direction of the valve body (20) relative to the central longitudinal axis (L), wherein
the collar (40) is arranged circumferentially relative to the central longitudinal axis (L) to encircle the injection nozzle (29).
Valve assembly (14) according to claim 1 with the collar (40) being circumferentially closed.
Valve assembly (14) according to one of the preceding claims with the radial extension of the collar (40) being decreasing in the fluid flow direction (F).
Valve assembly (14) according to one of the preceding claims with the valve needle (22) having an axial valve needle end (50) and the collar (40) having an axial collar end (52), and the axial collar end (52) ranging at least to a common plane (P) comprising the axial valve needle end (50) and extending in a radial direction (R) relative to the central longitudinal axis (L).
Valve assembly (14) according to one of the preceding claims with the valve body (20) and the collar (40) being formed as a one-part element.
Injection valve (10) for a combustion chamber of a combustion engine comprising the valve assembly (14) according to one of the preceding claims.