EP1995447A1

EP1995447A1 - Valve assembly for an injection valve and injection valve

Info

Publication number: EP1995447A1
Application number: EP07010384A
Authority: EP
Inventors: Enio Biasci; Federico Zimmitti
Original assignee: Continental Automotive Technologies GmbH
Current assignee: Aumovio Germany GmbH
Priority date: 2007-05-24
Filing date: 2007-05-24
Publication date: 2008-11-26
Anticipated expiration: 2027-05-24
Also published as: DE602007004084D1; EP1995447B1

Abstract

Valve assembly (14) of an injection valve (10) and injection valve (10), the valve assembly (14) comprising a first valve body (20) including a central longitudinal axis (A) and comprising a first cavity (24), a second valve body (21) being rigidly coupled to the first valve body (20) and comprising a second cavity (25) with a fluid outlet portion (28), and - a valve needle (22) axially movable in the first cavity (24) and the second cavity (25), the valve needle (22) preventing a fluid flow through the fluid outlet portion (28) of the second cavity (25) in a closing position and releasing the fluid flow through the fluid outlet portion (28) in further positions, the second valve body (21) comprising a passage (40) being arranged between the first cavity (24) and the second cavity (25) directly upstream the second cavity (25) and being designed to enable a fluid flow from the first cavity (24) to the second cavity (25). A filter (42) is arranged directly upstream or inside the passage (40) and is designed to filter fluid flowing from the first cavity (24) to the second cavity (25).

Description

The invention relates to a valve assembly for an injection valve and an injection valve.
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 of an injection valve, the valve assembly comprising a first valve body including a central longitudinal axis and comprising a first cavity, a second valve body being rigidly coupled to the first valve body and comprising a second cavity with a fluid outlet portion, and a valve needle axially movable in the first cavity and the second cavity, the valve needle preventing a fluid flow through the fluid outlet portion of the second cavity in a closing position and releasing the fluid flow through the fluid outlet portion in further positions, the second valve body comprising a passage being arranged between the first cavity and the second cavity directly upstream the second cavity and being designed to enable a fluid flow from the first cavity to the second cavity. A filter is arranged directly upstream or inside the passage and is designed to filter fluid flowing from the first cavity to the second cavity.
This has the advantage that a flow of particles from the first cavity to the fluid outlet portion can be avoided. Consequently, a damage of the valve body and/or the valve needle near the fluid outlet portion due to particles can be avoided. Furthermore, a process for press-fitting the first valve body to the second valve body does not need a further control in view of particles being produced during the press-fitting process. Additionally, an elimination of further filters in the flow line is possible.
In an advantageous embodiment of the invention, a spring is arranged and designed to exert a force on the valve needle in axial direction, and is arranged in a part of the first cavity extending away from the filter in direction of the central longitudinal axis. This has the advantage that a space for the arrangement of the filter is available in the first cavity. The spring can be designed in a small size. Consequently, a low-cost solution for the small spring is possible.
According to a second aspect the invention is distinguished by an injection valve comprising the valve assembly of one of the foregoing embodiments.
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, and
Figure 2, a part of a valve assembly of the injection valve in a longitudinal section view.

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 a chamber 38 of 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 is inserted into the housing 12 and comprises a first valve body 20 with a central longitudinal axis A and a first cavity 24 which is axially led through the first valve body 20. Furthermore, the valve assembly 14 comprises a second valve body 21 with a second cavity 25 which is axially led through the second valve body 21. The first valve body 20 and the second valve body 21 are rigidly coupled with each other.
In the first cavity 24 and in the second cavity 25 a valve needle 22 is arranged which is movable in the direction of the central longitudinal axis A.
On one of the free ends of the second cavity 25 of the second valve body 21 a fluid outlet portion 28 is formed which is closed or open depending on the axial position of the valve needle 22. Outside of the closing position of the valve needle 22 there is a gap between the second valve body 21 and the valve needle 22 at an axial end of the injection valve 10 facing away from of the actuator unit 16. The gap forms a valve nozzle 29.
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.
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 first 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.
A passage 40 is arranged in the second valve body 21 between the first cavity 24 and the second cavity 25. The passage 40 is arranged directly upstream the second cavity 25 and allows a fluid flow from the first cavity 24 to the second cavity 25.
In the first cavity 24 directly upstream the passage 40 a filter 42 is arranged. The filter 42 enables to filter the fluid from particles, when the fluid is flowing from the first cavity 24 to the second cavity 25 with the fluid outlet portion 28. Consequently, the valve nozzle 29 can be protected from particles which can cause damages of the second valve body 21 or the valve needle 22 in the area of the valve nozzle 29. Due to its ability to filter particles very near to the valve nozzle 29 it is possible to realize the flow line without the use of further filters. In particular, no filter is needed in the flow line between the fluid inlet portion 26 and the first cavity 24. This allows a simple shape of the first valve body 20 in an area where the fluid enters the first cavity 24. The filter 42 can also be arranged inside the passage 40. This has the advantage that no space for the filter 42 will be needed inside the first cavity 24.
The second valve body 21 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 second valve body 21 and the valve needle 22. The spring 30 is arranged in a part of the first cavity 24 upstream the filter 42. By this only a small space inside the first cavity 24 is needed for the spring 30. Furthermore, the small size of the spring 30 allows a low-cost solution for the injection valve 10. The spring 30 can be designed to exert only a small force on the valve needle 22. Therefore, the valve needle spring rest 34 can be of a small size as well. This allows a low-cost solution of the valve needle spring rest 34.
Between the valve needle 22 and the first valve body 20 a bellow 36 is arranged which is sealingly coupling the first valve body 20 with the valve needle 22. By this a fluid flow between the first cavity 24 and the chamber 38 with the actuator unit 16 is prevented. Furthermore, the bellow 36 is formed and arranged in a way that the actuator unit 16 can cause an axial movement of the valve needle 22.
Figure 2 shows a sectional view of the valve assembly 14 with the filter 42. The filter 42 is of a frustro-conical shape and has an inner cavity. The filter 42 is arranged coaxially to the second valve body 21. The filter 42 can also be of a hollow cylindrical shape. The inner cavity of the filter 42 forms an inner surface 46, which is in tight contact with an outer surface 48 of the second valve body 21.
In the following, the function of the injection valve 10 will be described in detail:

The fuel is led from the fluid inlet portion 26 in the housing 12 to the first cavity 24 of the first valve body 20 and then through the passage 40 to the second cavity 25 of the second valve body 21 with the fluid outlet portion 28. The filter 42 which is arranged in the first cavity 24 of the first valve body 20 directly upstream the passage 40 can prevent an intrusion of particles into the second cavity 25 of the second valve body 21. Consequently, it can be prevented that particles can reach the fluid outlet portion 28 and the valve nozzle 29. Therefore, a damage of the valve nozzle 29 due to particles can be prevented.

The fluid flow from the fluid outlet portion 28 to the chamber 38 with the actuator unit 16 is prevented by the bellow 36.
The valve needle 22 prevents a fluid flow through the fluid outlet portion 28 in the second valve body 21 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 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 exert a force on the valve needle 22. The valve needle 22 is able to move in axial direction out of the closing position.
The spring 30 can exert a force on 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. 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.
In the following, the process of manufacturing the valve assembly 14 will be described:

In a first step, the first valve body 20 and the second valve body 21 are provided and the parts which have to be arranged between the first valve body 20 and the second valve body 21, as the valve needle 22, the spring 30, the bellow 36 and the filter 42 are inserted between the first valve body 20 and the second valve body 21.

In a further step, after the preassembly of these parts the second valve body 21 and the first valve body 20 are rigidly coupled, in particular by a press-fitting process.
In the case that during the press-fitting process particles are produced in a transition area between the first valve body 20 and the second valve body 21, these particles can be trapped in the first cavity 24 of the first valve body 20. The fluid flows from the first cavity 24 to the second cavity 25 through the passage 40 and the particles produced during the press-fitting process can be filtered by the filter 42 being arranged upstream the passage 40. Consequently, it is possible to prevent that particles reach the valve nozzle 29. Thus, the risk of a damage of the valve nozzle 29 can be kept small.

Claims

Valve assembly (14) of an injection valve (10), the valve assembly (14) comprising
- a first valve body (20) including a central longitudinal axis (A) and comprising a first cavity (24),

- a second valve body (21) being rigidly coupled to the first valve body (20) and comprising a second cavity (25) with a fluid outlet portion (28), and

- a valve needle (22) axially movable in the first cavity (24) and the second cavity (25), the valve needle (22) preventing a fluid flow through the fluid outlet portion (28) of the second cavity (25) in a closing position and releasing the fluid flow through the fluid outlet portion (28) in further positions,
the second valve body (21) comprising a passage (40) being arranged between the first cavity (24) and the second cavity (25) directly upstream the second cavity (25) and being designed to enable a fluid flow from the first cavity (24) to the second cavity (25), wherein
a filter (42) is arranged directly upstream or inside the passage (40) and is designed to filter fluid flowing from the first cavity (24) to the second cavity (25).
Valve assembly (14) in accordance with claim 1 with a spring (30) being arranged and designed to exert a force on the valve needle (22) in axial direction, and being arranged in a part of the first cavity (24) extending away from the filter (42) in direction of the central longitudinal axis (A).
Injection valve (10) comprising the valve assembly (14) in accordance with one of the preceding claims.