EP2216542A1

EP2216542A1 - Valve assembly for an injection valve and injection valve

Info

Publication number: EP2216542A1
Application number: EP09001675A
Authority: EP
Inventors: Luigi Gargiulo; Luca Gestri
Original assignee: Continental Automotive GmbH
Current assignee: Continental Automotive GmbH
Priority date: 2009-02-06
Filing date: 2009-02-06
Publication date: 2010-08-11

Abstract

Valve assembly (14) for an injection valve (22), comprising a valve body (20) including a central longitudinal axis (A), the valve body (20) comprising a cavity (24) with a fluid inlet portion (26) and a fluid outlet portion (28), 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 through the fluid outlet portion (28) in further positions, the valve needle (22) having a guide portion (46) being designed to guide the valve needle (22) in the valve body. A ring element (50) is arranged coaxially between the valve body (20) and the valve needle (22) at an axial end (48) of the needle guide portion (46) facing away from the fluid outlet portion (28). The ring element is fixedly coupled to the valve needle (22). The ring element (50) is designed to cause a given pressure drop for a fluid flow through the fluid outlet portion (28).

Description

The invention relates to a valve assembly for an injection valve and an injection valve.
Injection valves are in wide spread 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 also 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 piezo electric 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 diesel engines in the range of up to 2000 bar.
The object of the invention is to create a valve assembly and an injection valve which are simply to be manufactured and which facilitate a reliable and precise function.
These objects are achieved by the features of the independent claim. Advantageous embodiments of the invention are given in the sub-claims.
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 with a fluid inlet portion and a fluid outlet portion, and a valve needle axially moveable in the cavity, the valve needle preventing a fluid flow through the outlet portion in a closing position and releasing the fluid flow through the fluid outlet portion in further positions. Furthermore, the valve needle has a guide portion being designed to guide the valve needle in the valve body. A ring element is arranged coaxially between the valve body and the valve needle upstream an axial end of the needle guide portion facing away from the fluid outlet portion and is fixedly coupled to the valve needle. The ring element is designed to cause a given pressure drop for a fluid flow through the fluid outlet portion.
The characteristic of the fluid flow releasing through the fluid outlet portion can be strongly influenced by the configuration of the valve assembly, in particular of the valve needle and/or its adjacent parts. The ring element has the advantage that the pressure drop during the fluid flow through the fluid outlet portion can be adjusted. This makes it possible that the fluid flow releasing through the fluid outlet portion which can be a spray can have a desired spray angle and spray atomization. In particular, the distribution of the fluid droplets can be adjusted and an axial-symmetric distribution of the spray can be obtained. Furthermore, an influence on the friction forces between the valve needle and the valve body can be obtained. Consequently, the performance of the movement of the valve needle in particular during the closing process of the injection valve can be influenced. In particular, this means that the closing movement of the valve needle can be dampened.
In an advantageous embodiment an axial distance between the ring element and the needle guide portion is between about 0.2 mm and about 10 mm. This has the advantage that the fluid flow downstream the ring element can be adapted according to the desired configuration of the guide portion.
In a further advantageous embodiment the ring element has a basically circular cylindrical shape. This is a simple shape, which can be produced with low costs.
In a further advantageous embodiment the valve needle and the ring element are forming a one-piece element. This allows a very precise positioning of the ring element relative to the valve needle. Furthermore, this allows a construction of the ring element on the valve needle which can be mechanically very solid.
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 with a valve assembly in a longitudinal section view,
Figure 2, an enlarged view of the detail II of the valve assembly in Figure 1 in a longitudinal section view, and.
Figure 3, an enlarged view of the valve assembly of the injection valve in a cross section view along the line III-III' of Figure 2.

Elements of the same design and function that appear in different illustrations are identified by the same reference character.
An injection valve 10 (Figure 1) that is preferably 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 A and a cavity 24 which is axially led through the valve body 20. A valve needle 22 is arranged in the cavity 24 and is axially movable in the cavity 24. 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 the valve needle 22.
Outside of the closing position of the valve needle 22 there is a gap between the valve body 20 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 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 between the actuator unit 16 and the valve body 20 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.
The valve needle 22 has a guide portion 46 which can reliably guide the valve needle 22 in the valve body 20.
Upstream an axial end 48 of the guide portion 46 facing away from the fluid outlet portion 28 a ring element 50 is arranged in the cavity 24 coaxially between the valve body 20 and the valve needle 22 and protrudes in radial direction away from the valve needle 22 (shown in detailed views in Figures 2 and 3) . If the injection valve 10 is a fuel injection valve for an internal combustion engine, the typical distance between the ring element 50 and the valve body 20 is preferably 0.1 to 0.2 mm. Due to the little distance between the ring element 50 and the valve body 20 the ring element 50 can create a given pressure drop in the case that a fluid flow through the valve nozzle 29 is enabled. If the injection valve 10 is a fuel injection valve for an internal combustion engine, the pressure drop is preferably in the range between 5 and 40 bar. Depending on the outer diameter of the ring element 50 the pressure drop during the fluid flow through the valve nozzle 29 can be adjusted easily. Consequently, a fluid spray outside the fluid outlet portion 28 can obtain a desired spray angle and a desired spray atomization. In particular, the size distribution of the fluid droplets can be regulated easily and an axial-symmetric distribution of the spray can be obtained.
Preferably the ring element 50 has an axial distance D from the needle guide portion 46. The axial distance D between the ring element 50 and the needle guide portion 46 is from about 0.2 mm to about 10 mm. By this the fluid flow can be influenced in a desired manner before the fluid enters the needle guide portion 46.
Preferably the ring element 50 has a basically circular cylindrical shape. This shape can be manufactured easily and allows a low cost solution.
As shown in the figures the valve needle 22 and the ring element 50 are forming preferably a one-piece element. This has the advantage that the position of the ring element 50 relative to the valve needle 22 can be defined very exactly. Furthermore, the stability of the connection between the valve needle 22 and the ring element 50 is very high.
In a further embodiment the ring element 50 is welded to the valve needle 22, for example by spot-laser welding. This makes it possible to achieve a stable connection between the ring element 50 and the valve needle 22. Furthermore, this connection is a low cost solution.
Alternatively, the ring element 50 is press-fitted to the valve needle 22. This allows an exact positioning of the ring element 50 relative to the valve needle 22. Furthermore, this embodiment is a low cost solution.
In the following, the function of the injection valve 10 being described in detail:

The fluid is led from the fluid inlet portion 26 in the housing 12 towards the valve body 20 and then towards 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 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. 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 the gap between the valve body 20 and the valve needle 22 at the axial end of the injection valve 10 facing away from of the actuator unit 16 forms the valve 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. 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. As the distance between the ring element 50 an the valve body 20 has an influence on the friction forces between the valve needle 22 and the valve body 20, the performance of the movement of the valve needle 22 during the closing of the injection valve 10 can be influenced. In particular, due to the ring element 50 arranged between the valve needle 22 and the valve body 20 the closing movement of the valve needle 22 can be dampened reliably.

Claims

Valve assembly (14) for an injection valve (10), comprising
- a valve body (20) including a central longitudinal axis (A), the valve body (20) comprising a cavity (24) with a fluid inlet portion (26) and a fluid outlet portion (28),

- 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 through the fluid outlet portion (28) in further positions, the valve needle (22) having a guide portion (46) being designed to guide the valve needle (22) in the valve body,
wherein a ring element (50) is arranged coaxially between the valve body (20) and the valve needle (22) upstream an axial end (48) of the needle guide portion (46) facing away from the fluid outlet portion (28) and is fixedly coupled to the valve needle (22), the ring element (50) being designed to cause a given pressure drop for a fluid flow through the fluid outlet portion (28).
Valve assembly (14) according to claim 1, characterized in that an axial distance (D) between the ring element (50) and the needle guide portion (46) is between about 0.2 mm and about 10 mm.
Valve assembly (14) according to claim 1 or 2, characterized in that the ring element (50) has a basically circular cylindrical shape.
Valve assembly (14) according to one of the preceding claims, characterized in that the valve needle (22) and the ring element (50) are forming a one-piece element.
Injection valve (22) with an actuator unit (16) and a valve assembly (14) according to one of the preceding claims, with the actuator unit (16) being designed to act on the valve assembly (14).