Fuel injection valve

ABSTRACT

A fuel injector () for fuel injection systems of internal combustion engines has a solenoid (), a valve needle () pressed in the closing direction by a return spring () to activate a valve closing member (), which together with a valve seat surface () forms a sealing seat, and an armature () in friction-locking connection with a valve needle (). A first guide sleeve () and a second guide sleeve () are connected to the valve needle (). The armature () has radial play with respect to the valve needle () as a result of the central opening (), the diameter of which is greater than the diameter of the valve needle ().

INFORMATION

DETAILED DESCRIPTION OF THE INVENTION

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

A fuel injector is constructed in the form of a fuel injector for fuel injection systems on spark-ignition internal combustion engines, in which the fuel-air mixture is compressed. Fuel injector is particularly suitable for direct injection of fuel into a combustion chamber, not shown, of an internal combustion engine.

Fuel injector is composed of a nozzle body into which a valve needle is guided. Valve needle acts upon a valve closing member , which acts together with a valve seat surface situated on a valve seat body to compose a sealing seat. In fuel injector in the exemplary embodiment the opening action is inwards, and fuel injector has a spray orifice .

Valve needle is rotatably mounted in the sealing seat in order to permit simple guidance of the needle. This has no impact on the imparting of swirl by fuel injector , since valve needle is symmetrical around its axis of rotation.

Nozzle body is sealed against external pole of a solenoid by a seal . Solenoid is encapsulated in a solenoid housing and wound around a bobbin , which is touching internal pole of solenoid . Internal pole and external pole are separated from one another by a gap and supported on a connecting member . Solenoid is excited through a wire by an electrical current which may be supplied via an electrical plug contact . Plug contact is surrounded by a plastic sheath which may be sprayed onto internal pole .

Valve needle is guided in a valve needle guide , which is disk-shaped. A matched setting disk is used to adjust the stroke setting. An armature is located on the other side of setting disk . The armature is in friction-locking connection with valve needle , through first guide sleeve , and valve needle in turn is connected by a weld seam to first guide sleeve . Supported on first guide sleeve is a return spring , which in the present design of fuel injector is pre-tensioned by a sleeve . A second guide sleeve , which is connected to valve needle by way of a weld seam , acts as the lower armature stop.

Armature has a central opening , through which valve needle protrudes. The radial diameter of central opening is larger than the diameter of valve needle , with the result that armature has radial play relative to valve needle . This measure, in conjunction with guide sleeves and , ensures that valve needle cannot become tilted or stuck.

A detailed description of the area identified as II in FIG. 1 between guide sleeves and is explained more fully in the description covering FIGS. 2 and 3.

Fuel ducts to run in valve needle guide , in armature and on valve seat body , bringing the fuel, which is supplied via a central fuel feed and is filtered through a filter element , to spray orifice . Fuel injector is sealed off by a seal with respect to a cylinder head not further shown or with respect to a fuel distribution line.

In the idle state of fuel injector , valve needle is pressed by return spring via first guide sleeve against the stroke direction such that valve closing member is held in sealing contact at valve seat . When solenoid is excited, it creates a magnetic field that first pulls armature , which is freely movable between guide sleeves and , towards first guide sleeve and then moves armature with valve needle and first guide sleeve in the stroke direction against the spring force of return spring . In this operation, valve needle takes second guide sleeve with it, guide sleeve being welded to valve needle , also in the stroke direction. Valve closing member , which is acted on by valve needle , lifts off valve seat surface and fuel is sprayed out through spray orifice .

When the solenoid current is switched off, after sufficient decay of the magnetic field armature drops away from internal pole in reaction to the pressure of return spring , as a result of which the unit composed of valve needle , stop sleeves and and armature moves against the stroke direction. As a result, valve closing member settles onto valve seat surface and fuel injector is closed.

FIG. 2 shows the area identified as II in FIG. 1, in a partial and highly schematized representation.

Armature is situated between first guide sleeve , upon which return spring is supported, and second guide sleeve . By central opening in armature , the diameter of which is selected to be slightly greater than the diameter of valve needle protruding through armature , radial play for armature is ensured. Since between first face of armature and first guide sleeve there is a first gap , and between second face of armature and second guide sleeve there is a second gap , slight axial play is also present. Armature is accurately and precisely guided only by external pole of fuel injector , external pole in the present first exemplary embodiment being sleeve-shaped. The sleeve-shaped component identified by may also be a non-magnetic thin-walled sleeve which is a part of the injector housing.

Guide sleeves and , for their part, are guided in internal pole and in nozzle body of fuel injector , in each case with slight play. Guide sleeves and are rigidly connected to valve needle , preferably by welding. This ensures on the one hand that the rotational symmetry of valve needle is maintained and also ensures problem-free guidance of valve needle and/or armature even in the event of serious center offset or major manufacturing errors in the components used.

Once the current exciting solenoid is switched on, after sufficient creation of the magnetic field, armature is attracted to internal pole . In this operation, armature brings valve needle with it, via first guide sleeve , against the force of return spring , and in consequence fuel injector is opened. Since first gap is between first guide sleeve and armature , armature is initially pre-accelerated by the magnetic field, before the magnetic field has to exert stroke force in drawing armature , against the force of return spring . In consequence, in addition to guaranteeing that armature will move freely or that valve needle will operate without tilting, the opening times of fuel injector can also be improved.

Similarly, after the solenoid current is switched off, armature is initially pressed away from internal pole by return spring and pre-accelerated via the stroke of second gap , before armature takes valve needle with it by second guide sleeve and fuel injector is closed. As a result, in addition to guaranteeing that armature will move freely or that valve needle will operate without tilting, the closing times of fuel injector can also be improved. Overall, these measures also improve the accuracy of the fuel metering.

FIG. 3 shows a second exemplary embodiment of fuel injector according to the invention, from the same view as in FIG. .

For further improvement of the guidance of free armature , in the present second exemplary embodiment surfaces and of guide sleeves and facing faces and of armature are formed in a wedge or cone shape. Elevations and act as the corresponding abutment surfaces for wedge-shaped surfaces and of guide sleeves and , elevations and being formed in rotational symmetry with faces and of armature and, for example, they can be formed as a truncated cone, a crown or a spherical cap.

Elevations and formed in this way are keyed together with wedge-shaped surfaces and and thus ensure more precise guidance of valve needle in guide sleeves and , without restricting the free movement of armature or the rotational symmetry of valve needle .

Since the total axial extent of gap , is smaller than the height of the keyed connections, armature cannot escape from the hollows in wedge-shaped surfaces and of guide sleeves and . In consequence, valve needle cannot tilt or stick.

The invention is not restricted to the exemplary embodiments represented and can also be used for a large number of other fuel injectors, and in particular also for fuel injectors in which the opening action is outwards.

DRAWING

Exemplary embodiments of the invention are shown in simplified form in the drawing, and explained in greater detail in the following description.

FIG. 1 shows a schematic cross-section through a first exemplary embodiment of a fuel injector according to the present invention,

FIG. 2 shows an enlarged schematic cross-section through the fuel injector according to the invention shown in FIG. 1 in the area marked as II in FIG. 1, and

FIG. 3 shows an enlarged schematic cross-section through a second exemplary embodiment of a fuel injector according to the invention shown in the area marked as II in FIG. .

CLAIMS

1. A fuel injector for fuel injection systems of internal combustion engines, comprising: a solenoid; a valve closing member; a valve needle adapted to be acted upon in a closing direction by a return spring to actuate the valve closing member, which, together with a valve seat surface, forms a sealing seat; an armature connected to the valve needle in a non-friction-locked manner; a first guide sleeve connected to the valve needle; and a second guide sleeve, wherein the valve needle is connected to the second guide sleeve in a friction-locked manner; wherein the armature is situated between the first guide sleeve and the second guide sleeve such that it can move freely in an axial direction; wherein the armature has a central opening whose diameter is greater than the diameter of the valve needle; and wherein the armature has radial play with respect to the valve needle.

2. The fuel injector according to claim 1, wherein the first guide sleeve is situated on a supply-side face of the armature, and the second guide sleeve is situated on a discharge-side face of the armature.

3. The fuel injector according to claim 1, wherein the valve needle protrudes through the armature via the central opening.

4. A fuel injector for fuel injection systems of internal combustion engines, comprising: a solenoid; a valve closing member; a valve needle adapted to be acted upon in a closing direction by a return spring to actuate the valve closing member, which, together with a valve seat surface, forms a sealing seat; an armature connected to the valve needle in a non-friction-locked manner; a first guide sleeve connected to the valve needle; and a second guide sleeve; wherein the valve needle is connected to the second guide sleeve in a friction-locked manner; wherein the armature is situated between the first guide sleeve and the second guide sleeve such that it can move freely in an axial direction; wherein the armature has a central opening whose diameter is greater than the diameter of the valve needle; wherein the armature has radial play with respect to the valve needle; and wherein the first guide sleeve and the second guide sleeve are welded to the valve needle.

5. A fuel injector a for fuel injection systems of internal combustion engines, comprising: a solenoid; a valve closing member; a valve needle adapted to be acted upon in a closing direction by a return spring to actuate the valve closing member, which, together with a valve seat surface, forms a sealing seat; an armature connected to the valve needle in a non-friction-locked manner; a first guide sleeve connected to the valve needle; and a second guide sleeve; wherein the valve needle is connected to the second guide sleeve in a friction-locked manner; wherein the armature is situated between the first guide sleeve and the second guide sleeve such that it can move freely in an axial direction; wherein the armature has a central opening whose diameter is greater than the diameter of the valve needle; wherein the armature has radial play with respect to the valve needle; and wherein the return spring is supported on the first guide sleeve.

6. A fuel injector for fuel injection systems of internal combustion engines, comprising: a solenoid; a valve closing member; a valve needle adapted to be acted upon in a closing direction by a return spring to actuate the valve closing member, which, together with a valve seat surface, forms a sealing seat; an armature connected to the valve needle in a non-friction-locked manner; a first guide sleeve connected to the valve needle; and a second guide sleeve; wherein the valve needle is connected to the second guide sleeve in a friction-locked manner; wherein the armature is situated between the first guide sleeve and the second guide sleeve such that it can move freely in an axial direction; wherein the armature has a central opening whose diameter is greater than the diameter of the valve needle; wherein the armature has radial play with respect to the valve needle; and wherein the valve needle is rotationally mounted in the sealing seat.

7. The fuel injector according to claim 6, wherein the valve needle is axially symmetric.

8. A fuel injector for fuel injection systems of internal combustion engines, comprising: a solenoid; a valve closing member; a valve needle adapted to be acted upon in a closing direction by a return spring to actuate the valve closing member, which, together with a valve seat surface, forms a sealing seat; an armature connected to the valve needle in a non-friction-locked manner; a first guide sleeve connected to the valve needle; and a second guide sleeve; wherein the valve needle is connected to the second guide sleeve in a friction-locked manner; wherein the armature is situated between the first guide sleeve and the second guide sleeve such that it can move freely in an axial direction; wherein the armature has a central opening whose diameter is greater than the diameter of the valve needle; wherein the armature has radial play with respect to the valve needle; wherein the first guide sleeve is situated on a supply-side face of the armature, and the second guide sleeve is situated on a discharge-side face of the armature; and wherein a first gap exists between the supply-side face of the armature and the first guide sleeve.

9. The fuel injector according to claim 8, wherein a second gap exists between the discharge-side face of the armature and the second guide sleeve.

10. A fuel injector for fuel injection systems of internal combustion engines, comprising: a solenoid; a valve closing member; a valve needle adapted to be acted upon in a closing direction by a return spring to actuate the valve closing member, which, together with a valve seat surface, forms a sealing seat; an armature connected to the valve needle in a non-friction-locked manner; a first guide sleeve connected to the valve needle; and a second guide sleeve; wherein the valve needle is connected to the second guide sleeve in a friction-locked manner; wherein the armature is situated between the first guide sleeve and the second guide sleeve such that it can move freely in an axial direction; wherein the armature has a central opening whose diameter is greater than the diameter of the valve needle; wherein the armature has radial play with respect to the valve needle; and wherein the guide sleeves each have a wedge-shaped surface.

11. The fuel injector according to claim 10, wherein the wedge-shaped surfaces face the armature.

12. The fuel injector according to claim 11, wherein a first wedge-shaped elevation on the supply-side face of the armature matches the wedge-shaped surface of the first guide sleeve.

13. The fuel injector according to claim 11, wherein a second wedge-shaped elevation on the discharge-side face of the armature matches the wedge-shaped surface of the second guide sleeve.

14. The fuel injector according to claim 11, wherein the armature has elevations which are one of a crown and a spherical cap.

15. A fuel injector for fuel injection systems of internal combustion engines, comprising: a solenoid; a valve closing member; a valve needle adapted to be acted upon in a closing direction by a return spring to actuate the valve closing member, which, together with a valve seat surface, forms a sealing seat; an armature connected to the valve needle in a non-friction-locked manner; a first guide sleeve connected to the valve needle; and a second guide sleeve for the armature, wherein the valve needle is connected to the second guide sleeve in a friction-locked manner; wherein the armature situated between the first guide sleeve and the second guide sleeve such that it can move freely in an axial direction as limited by the first guide sleeve and the second guide sleeve; wherein the armature has a central opening whose diameter is greater than the diameter of the valve needle; and wherein the armature has radial play with respect to the valve needle.

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