EP2003327A1

EP2003327A1 - Actuator unit for an injection valve and injection valve

Info

Publication number: EP2003327A1
Application number: EP07011598A
Authority: EP
Inventors: Valerio Polidori
Original assignee: Continental Automotive GmbH
Current assignee: Continental Automotive GmbH
Priority date: 2007-06-13
Filing date: 2007-06-13
Publication date: 2008-12-17

Abstract

Actuator unit (14) for an injection valve (10), comprising a piezo actuator (16) with a longitudinal axis (A), the piezo actuator (16) having an electric pin (44) being electrically coupable to a power supply, a top cap (42) being a part of a piezo actuator housing (17), the piezo actuator (16) being arrangeable in the piezo actuator housing (17), and an adapter (47) with a supporting element (48) and terminal elements (49) being rigidly coupled to the supporting element (48), at least one of the terminal elements (49) being electrically coupled to the electric pin (44) of the piezo actuator (16) and at least one of the terminal elements (49) being electrically coupable to the power supply, wherein the adapter (47) is rigidly coupled to the top cap (42).

Description

The invention relates to an actuator unit 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 for an internal combustion engine comprise actuator units. In order to inject fuel, the actuator unit is energized so that a fluid flow through the fluid outlet portion of the injection valve is enabled.
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 the range of up to 200 bar or in the case of diesel engines in the range of up to 2,000 bar. The injection of fluids under such high pressures has to be carried out very precisely.
During the injection process very fast changes of the pressure may occur. The fast changes of the pressure may cause pressure waves in the fluid which leads to pressure waves in different parts of the injector, in particular in the actuator unit.
The object of the invention is to create an actuator unit that is simply to be manufactured and which facilitates a reliable and precise actuation of the injection valve.
These objects are achieved by the features of the independent claims. Advantageous embodiments of the invention are given in the sub-claims.
According to a first aspect the invention is distinguished by an actuator unit for an injection valve, comprising a piezo actuator with a longitudinal axis, the piezo actuator having an electric pin being electrically coupable to a power supply, a top cap being a part of a piezo actuator housing, the piezo actuator being arrangeable in the piezo actuator housing, and an adapter with a supporting element and terminal elements being rigidly coupled to the supporting element, at least one of the terminal elements being electrically coupled to the electric pin of the piezo actuator and at least one of the terminal elements being electrically coupable to the power supply, wherein the adapter is rigidly coupled to the top cap.
This has the advantage that a direct transmission of forces between the adapter with the supporting element and the terminal elements and the top cap of the piezo actuator housing is possible. Furthermore, a relative movement of the adapter relative to the top cap of the piezo actuator housing, in particular a relative axial movement, can be prevented. Consequently, the electric connection between the electric pin of the piezo actuator and the terminal elements of the adapter can be carried out in a mechanical robust manner.
In an advantageous embodiment of the invention the supporting element is formed as an injection moulded part. By this, the adapter can be simply manufactured.
In a further advantageous embodiment of the invention the adapter and the top cap of the piezo actuator housing are forming a positive-fit coupling. This has the advantage that a good force transmission between the adapter and the top cap of the piezo actuator housing is possible.
In a further advantageous embodiment of the invention the top cap of the piezo actuator housing comprises a channel, the channel extending perpendicular to the longitudinal axis and being designed as a going-through channel. This has the advantage that the channel as a simple element allows a robust coupling between the top cap of the piezo actuator housing and the adapter with the supporting element and the terminal elements, in particular in case of injection moulding of the coupling between top cap and adapter.
According to a second aspect the invention is distinguished by an injection valve comprising the actuator unit of the first aspect of the invention, with the actuator unit being designed for acting on the valve assembly.
Exemplary embodiments of the invention are explained in the following with the help of schematic drawings. These are as follows:

Figure 1,: an injection valve in a longitudinal section view,
Figure 2,: an actuator unit for the injection valve according to figure 1 in a longitudinal section view,
Figure 3a,: parts of the actuator unit for the injection valve in a perspective view, and
Figure 3b,: parts of the actuator unit for the injection valve in a perspective 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 valve assembly 60, an actuator unit 14 and a connector 56.
The injection valve 10 has a housing 12 with a tubular shape which has a central longitudinal axis A. The housing 12 of the injection valve 10 comprises a cavity 24 which is axially led through the housing 12. The actuator unit 14 is inserted into the cavity 24 of the housing 12 and comprises a piezo actuator 16, which changes its axial length depending on a control signal applied to it. A piezo actuator housing 17 encloses the piezo actuator 16 so that the piezo actuator 16 is stored in a mechanical robust manner.
The valve assembly 60 comprises a valve body 20 and a part of the 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. Furthermore, the injection valve 10 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 above 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 of the injection valve 10 it 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 14.
Figure 2 shows a detailed view of the actuator unit 14. The piezo actuator housing 17 enclosing the piezo actuator 16 comprises a top cap 42. The top cap 42 of the piezo actuator housing 17 is arranged at an end of the piezo actuator 16 facing away from the valve assembly 60. The actuator unit 14 further comprises a piston 46. A thermal compensator unit 40 is arranged in the cavity 24 of the housing 12 and is mechanically coupled to the piston 46 of the piezo actuator 16. The thermal compensation unit 40 enables to set an axial preload force on the actuator unit 14 via the piston 46 to compensate changes of the fluid flow through the fluid outlet portion 44 in the case of temperature changes of the injection valve 10.
The piezo actuator 16 further comprises an electric pin 44 to supply the piezo actuator 16 with electric energy. The piezo actuator 16 changes its length in axial direction depending on electric energy supplied to it. By changing its length the piezo actuator 16 can exert a force to the valve needle 22. The force from the piezo actuator 16 being exerted to the valve needle 22 in an axial direction allows or prevents a fluid flow through the fluid outlet portion 28.
The injection valve 10 further comprises the connector 56 with a non-conductive connector body 57 in which an electric conductor 58 is arranged. Electric energy can be supplied to the electric conductor 58 of the connector 56.
The actuator unit 40 comprises an adapter 47 consisting of a supporting element 48 and terminal elements 49 which are rigidly coupled to the supporting element 48. Preferably, the supporting element 48 consists of plastic or another non-conductive material. The electric conductor 58 of the connector 56 is electrically coupled to one of the terminal elements 49 of the adapter 47 which is electrically coupled to another of the terminal elements 49 which on its part is electrically coupled to the electric pin 44 of the piezo actuator 60. Consequently, electric energy can be simply supplied to the piezo actuator 16 via the connector 56.
Figure 3a shows the top cap 42 of the piezo actuator housing 17 with grooves 62 perpendicular to the longitudinal axis A. Furthermore, the top cap 42 of the piezo actuator housing 17 comprises a channel 43 arranged perpendicular to the longitudinal axis A and perpendicular to the grooves 62. The channel 43 is designed as a going-through channel.
Figure 3b shows the top cap 42 of the piezo actuator housing 17 and the adapter 47 wherein the adapter 47 is rigidly coupled to the top cap 42 of the piezo actuator housing 17. The adapter 47 is coupled to the top cap 42 of the piezo actuator housing 17 by a molding process. The channel 43 which is designed as a going-through channel supports a homogenous distribution of material during the molding process, in particular in the case of an injection molding process. One of the grooves 62 of the top cap 42 of the piezo actuator housing 17 and one of tongues 64 of the molded part are forming a positive-fit coupling which allows a rigid coupling between the adapter 47 to the top cap 42. Thus, a good force transmission between the supporting element 48 of the adapter 47 and the top cap 42 of the piezo injector housing 17 is enabled.
In the following, the function of the injection valve 10 will be described in detail:
The fluid is led from the fluid inlet portion 26 through the housing 12 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.
The piezo actuator 16 may change its axial length if it is energized. By changing its length the piezo actuator 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. Outside 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 the piezo actuator 16. The spring 30 can force the valve needle 22 via the valve needle spring rest 34 towards the piezo actuator 16. In the case the piezo actuator 16 is de-energized the piezo actuator 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 piezo actuator 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.
If the piezo actuator 16 is energized vibrations can occur at the top cap 42 of the piezo actuator housing 17. By rigidly coupling the adapter 47 to the top cap 42 of the piezo actuator housing 17 the forces caused by the vibrations can be transmitted directly from the top cap 42 of the piezo actuator housing 17 to the adapter 47. Consequently, it is possible to avoid a transfer of mechanical forces between the terminal elements 49 of the adapter 47 and the electric pins 44 of the piezo actuator 16. Thus, a damage or a destruction of one of the terminal elements 49 of the adapter 47 or one of the electric pins 44 of the piezo actuator 16 due to high mechanical forces can be prevented.
This allows to obtain a long life time of the actuator unit 14 by a mechanical robust rigid coupling between the adapter 47 and the top cap 42.

Claims

Actuator unit (14) for an injection valve (10), comprising
- a piezo actuator (16) with a longitudinal axis (A), the piezo actuator (16) having an electric pin (44) being electrically coupable to a power supply,

- a top cap (42) being a part of a piezo actuator housing (17), the piezo actuator (16) being arrangeable in the piezo actuator housing (17), and

- an adapter (47) with a supporting element (48) and terminal elements (49) being rigidly coupled to the supporting element (48), at least one of the terminal elements (49) being electrically coupled to the electric pin (44) of the piezo actuator (16) and at least one of the terminal elements (49) being electrically coupable to the power supply, wherein the adapter (47) is rigidly coupled to the top cap (42).
Actuator unit (14) according to claim 1, wherein the supporting element (48) is formed as an injection moulded part.
Actuator unit (14) according to claim 1 or 2, wherein the adapter (47) and the top cap (42) are forming a positive-fit coupling.
Actuator unit (14) according to one of the preceding claims, with the top cap (42) comprising a channel (43), the channel (43) extending perpendicular to the longitudinal axis (A) and being designed as a going-through channel.
Injection valve (10) with a valve assembly (60) and an actuator unit (14) according to one of the preceding claims, with the actuator unit (14) being designed for acting on the valve assembly (60).