Valve assembly for an injection valve and injection valve

A valve assembly for an injection valve includes a valve body including a cavity with a fluid inlet portion and a fluid outlet portion, 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 through the fluid outlet portion in a further position, an upper retainer arranged in the cavity and fixed to the valve needle, and an electro-magnetic actuator unit configured to actuate the valve needle, the electro-magnetic actuator unit comprising an armature, arranged in the cavity and axially movable relative to the valve needle, the armature configured to be coupled to the upper retainer when the valve needle is actuated to leave the closing position, and a permanent magnet arranged in the cavity adjacent the position of the armature when the valve needle is in its closing position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Stage Application of International Application No. PCT/EP2011/067033 filed Sep. 29, 2011, which designates the United States of America, and claims priority to EP Application No. 10183713.6 filed Sep. 30, 2010, the contents of which are hereby incorporated by reference in their entirety.

TECHNICAL FIELD

The disclosure relates to a valve assembly for an injection valve and an injection valve.

BACKGROUND

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. Already in the near future, need will arise to operate internal combustion engines at still higher fuel pressure values. On the other hand, it is important to provide the engines with different amounts of fuel at different operating conditions. Especially the minimum amount of fuel necessary for operating an engine at idle running conditions will decrease in the future in order to reduce unwanted emissions.

SUMMARY

One embodiment provides 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, 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 through the fluid outlet portion in at least one further position, an upper retainer being arranged in the cavity and being fixedly coupled to the valve needle, and an electro-magnetic actuator unit being de signed to actuate the valve needle, the electro-magnetic actuator unit comprising an armature, which is arranged in the cavity and which is axially movable relative to the valve needle, the armature being designed to be coupled to the upper retainer when the valve needle is actuated to leave the closing position, wherein a permanent magnet is arranged in the cavity at a position adjacent to the position of the armature, when the valve needle is in its closing position.

In a further embodiment, the permanent magnet is fixedly coupled to the valve body.

In a further embodiment, the permanent magnet is at least partially surrounded by a ring-like non-magnetic element fixedly coupled to the valve body.

In a further embodiment, the ring-like non-magnetic element is of an elastic material.

In a further embodiment, the elastic material is a plastic or a metallic material.

In a further embodiment, the permanent magnet is of a plastic magnetic material.

In a further embodiment, the permanent magnet is overmoulded to the ring-like non-magnetic element.

In a further embodiment, the ring-like non-magnetic element comprises a side-cut in an axial and in a radial direction of the valve needle.

In a further embodiment, the valve body is of a magnetic material.

In a further embodiment, the valve body is of a non-magnetic material.

In a further embodiment, the cavity comprises a step.

In a further embodiment, a washer is arranged between the permanent magnet and the step.

In a further embodiment, a washer is arranged between the permanent magnet and the armature.

In a further embodiment, the washer is fixedly coupled to the valve needle.

Another embodiment provides an injection valve with a valve assembly as disclosed above.

DETAILED DESCRIPTION

Embodiments of the present disclosed a valve assembly for an injection valve and an injection valve which facilitate a reliable and precise function under almost each of a lot of different operating conditions, when being operated in an internal combustion engine.

For example, some embodiments provide 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, 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 through the fluid outlet portion in at least one further position, an upper retainer being arranged in the cavity and being fixedly coupled to the valve needle, and an electro-magnetic actuator unit being designed to actuate the valve needle, the electro-magnetic actuator unit comprising an armature, which is arranged in the cavity and which is axially movable relative to the valve needle, the armature being designed to be coupled to the upper retainer when the valve needle is actuated to leave the closing position, wherein a permanent magnet is arranged in the cavity at a position adjacent to the position of the armature, when the valve needle is in its closing position.

The application of the permanent magnet enhances both, operating the valve needle more precisely and faster when lifting from the closing position and when moving to the closing position, more or less independently from actual operating conditions.

Other embodiments provide an injection valve including a valve assembly as disclosed herein.

An injection valve10that is in particular suitable for dosing fuel to an internal combustion engine is shown inFIG. 1in a longitudinal section view. It comprises in particular a valve assembly11.

The valve assembly11comprises a valve body14with a central longitudinal axis L and a housing16. The housing16is partially arranged around the valve body14. A cavity18is arranged in the valve body14.

The cavity18takes in a valve needle20, an upper retainer23, and an armature21. The upper retainer23is fixedly coupled to the valve needle20. The armature21is axially movable in the cavity18, relative to the valve needle20. The armature21is decoupled from the valve needle20in axial direction. The upper retainer23is formed as a collar around the valve needle20. A main spring24is arranged in a recess26provided in the inlet tube12. The main spring24is mechanically coupled to the upper retainer23. The upper retainer23is fixedly coupled to the valve needle20, and it can guide the valve needle20in axial direction inside the inlet tube12.

A filter element30is arranged in the inlet tube12and forms a further seat for the main spring24. During the manufacturing process of the injection valve10the filter element30can be axially moved in the inlet tube12in order to preload the main spring24in a desired manner. By this the main spring24exerts a force on the valve needle20towards an injection nozzle34of the injection valve10.

In a closing position of the valve needle20it sealingly rests on a seat plate32by this preventing a fluid flow through the at least one injection nozzle34. The injection nozzle34may be, for example, an injection hole. However, it may also be of some other type suitable for dosing fluid.

The valve assembly11is provided with an actuator unit36that may be an electro-magnetic actuator. The electro-magnetic actuator unit36comprises a coil38, which may be arranged inside the housing16. Furthermore, the electro-magnetic actuator unit36comprises the armature21. The housing16, the inlet tube12, the valve body14, and the armature21are forming an electromagnetic circuit.

The armature21is designed to be coupled to the upper retainer23when the valve needle20is actuated to leave the closing position, and it is designed to be decoupled from the upper retainer when the valve needle20is actuated to move to the closing position.

The cavity18comprises a fluid outlet portion40which is arranged near the seat plate32. The fluid outlet portion40communicates with a fluid inlet portion42which is provided in the valve body14.

Below the armature, in the direction towards the fluid outlet portion, there is arranged a permanent magnet22. It is fixedly coupled to the valve body14. Fixing may be achieved, for example, by welding to an inner surface of the valve body14in the area of the fluid inlet portion42or by providing a step44at the fluid inlet portion42and coupling the permanent magnet22to said step44.

FIG. 2shows another embodiment of the injection valve. With this embodiment the valve assembly11is additionally provided with a washer46, which is arranged in the fluid inlet portion42, between the step44and the permanent magnet22.

In order to be able to operate the valve needle20precisely, it is necessary to place the permanent magnet22and the washer46(as far as a washer is provided) at such a position within the fuel inlet portion42, where in a situation, where the valve needle20is in its closing position and where, accordingly, the armature21rests on the permanent magnet22, there is a gap48left between a surface of the armature21facing an end of the inlet tube12and said end of the inlet tube12, the length of which is at least equal to the maximum value of a lift of the valve needle20, when lifted off from its closing position.

In the following, the function of the injection valve10is described in detail, with reference toFIGS. 3 and 4. In these examples it is assumed that the permanent magnet22has a magnetic polarity such that the magnetic plus pole is directed towards the armature21, and that the magnetic minus pole is directed towards the fluid outlet portion40. The permanent existing magnetic poles and the magnetic poles resulting from energizing (or de-energizing) the coil38of the actuator unit are shown inFIGS. 3 and 4by “+” and “−” symbols. Magnetic flux is shown inFIGS. 3 and 4by narrow arrows, whereas the directions of the magnetic forces of the armature21and of the permanent magnet22are shown by bold arrows.

The fluid is led from the fluid inlet portion42towards the fluid outlet portion40. The valve needle20prevents a fluid flow through the fluid outlet portion40in the valve body14in a closing position of the valve needle20. Outside of the closing position of the valve needle20, the valve needle20enables the fluid flow through the fluid outlet portion40.

In the closing position of the valve needle20the actuator unit36is not energized. Due to the magnetic forces exerted by the permanent magnet22the armature21is pulled towards the permanent magnet22. Resulting from the magnetic orientation of the permanent magnet21that surface of the armature21which faces the permanent magnet22is of the minus pole type, whereas the surface of the armature21facing the inlet tube12is of the plus pole type. The spring exerts its force towards the upper retainer23which, in turn, presses the valve needle20towards the closing position.

In the case when the electro-magnetic actuator unit36with the coil38gets energized the actuator unit36will generate (caused by the magnetic flux) magnetic minus poles at that surface of the armature21facing the end of the inlet tube12, and magnetic plus poles at the end of the inlet tube12. Accordingly at that surface of the armature21, which faces the permanent magnet22, plus poles are generated, facing the plus poles of the permanent magnet22. Consequently, the armature21is not only attracted by the electro-magnetic actuator unit36with the coil38and moves in axial direction away from the fluid outlet portion40, but it is also pushed by the permanent magnet22towards the upper retainer23. Accordingly the armature21moves faster than in a traditional case, where there is no permanent magnet22. As a result the valve needle20is pushed off from its closing position faster than without support from the permanent magnet22; it opens faster.

Finally, outside of the closing position of the valve needle20a gap between the valve body14and the valve needle20at the axial end of the injection valve10facing away from of the actuator unit36forms a fluid path and fluid can pass through the injection nozzle34.

In the case when the actuator unit36is de-energized the main spring24forces the upper retainer23, and consequently the valve needle20, as it is fixedly coupled to the upper retainer23, to move in axial direction in the closing position of the valve needle20. Due to de-energizing the actuator unit36and the presence of the permanent magnet22the magnetic orientation of the armature21is reversed and that surface of the armature21, which faces the permanent magnet22, changes into a minus pole orientation. Accordingly the armature21is pulled by and towards the permanent magnet22, as the magnetic orientation of the surface of the permanent magnet22facing the armature21is of the plus pole orientation.

As a result the valve needle20reaches its closing position faster than without the presence of the permanent magnet22, as the forces of the main spring24are supported by the forces exerted by the permanent magnet22.

Accordingly, by providing traditional valve assemblies and injection valves with a permanent magnet as described herein be fore closing of the valve as well as opening the valve is supported, so that opening and closing can be done faster; the valve assembly and the injection valve can be operated more precisely and at a higher speed.

In some embodiments, the valve body14may be of a magnetic material or of a non-magnetic material.

FIG. 5shows another embodiment of the valve assembly and injection valve: Whereas with the valve assembly and injection valve ofFIG. 2the washer46is arranged beyond the permanent magnet22, seen in the direction towards the fuel outlet portion40, with the embodiment ofFIG. 5the washer46is arranged between the armature21and the permanent magnet22. This is shown in more detail inFIG. 6. In yet another embodiment, where the washer46is arranged between the armature21and the permanent magnet22, the washer46may be fixedly coupled to the valve needle20.

FIG. 7shows, partially, another embodiment in which the permanent magnet22is surrounded by a ring-like, non-magnetic element28, looking like a kind of housing. This element28is fixedly coupled to the valve body14. The ring-like, non-magnetic element28may be made of an elastic material like a plastic material or a metallic material. The permanent magnet22may be made of a plastic magnetic material. Further on, the permanent magnet22may be overmoulded to the ring-like, non-magnetic element28.

Such a ring-like, non-magnetic element28may be provided with a side-cut29, running along an axial and a radial direction of the valve needle20. InFIG. 8there is shown the ring-like, non-magnetic element28, provided with said side-cut29.

Assembling the parts of such a valve assembly11may be relatively easier, less complicated, and also production of contamination, resulting from the assembling procedure itself, may be significantly reduced, as compared with conventional designs.

When mounting the ring-like, non-magnetic element28, provided with said side-cut29and with the permanent magnet22, to the valve body14it is possible to press together the sidewall of the ring-like, non-magnetic element28until the outer diameter thereof is smaller than the inner diameter of the fluid inlet portion42of the valve body14at a position, where the permanent magnet22, together with the ring-like, non-magnetic element28, has to be mounted. Then the arrangement of ring-like, non-magnetic element28and the permanent magnet22can be brought into the valve body14to said position, and the pressing can be finished. Accordingly, the diameter of the ring-like, non-magnetic element28increases to its former value, which should have been designed to as to be greater than the value of said inner diameter of the fluid inlet portion42. In this way said arrangement is fixed to the fluid inlet portion42, whereby there is a good interference there between.

The cost may also be reduced. For fixedly coupling the permanent magnet22directly to the fluid inlet portion42it may be necessary to have the magnet made of a material, with which the permanent magnet22can be produced at very exact dimensions with very small tolerances. Such a material, however, is very expensive. In opposition to this, however, when mounting the permanent magnet22together with said ring-like, non-magnetic element28to the fluid inlet portion42, a material may be used for fabricating the permanent magnet22, which results in greater tolerances with the permanent magnet22. And such a material normally is much cheaper than said material resulting in permanent magnets with said very small tolerances.

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