Patent Application
20060113406
1. Field of the Invention
The present invention relates to a fuel injection valve for the intermittent injection of fuel into the combustion space of internal combustion engines.
2. Discussion of Background Information
In a fuel injection valve, such as is known, for example, from WO-A-02/086309, it may happen that, because of a failure, the injection valve member remains in the open position for longer than is necessary for a full-load injection operation. The result of this is that the corresponding cylinder combustion space is supplied with an excess of fuel, which may cause damage to the engine.
To avoid such damage, then, it is known, in fuel injection systems in which the individual fuel injection valves are supplied with fuel from a high-pressure fuel store (accumulator or common rail), to arrange, in the supply lines to the fuel injection valves, valves for limiting the throughflow quantity (see, for example, DE-A-43 44 190; DE-A-22 07 643; U.S. Pat. No. 4,589,393). These throughflow-quantity limiting valves shut off the throughflow of fuel in the event of an operating fault in the fuel injection valves.
These known solutions are complicated and costly, since, on the one hand, such a throughflow-quantity limiting valve has to be provided in each supply line to the fuel injection valves, and, on the other hand, the housing parts of these valves and the screw connections belonging to them have to be designed for the very high operating pressure (up to 2000 bar). This means, inter alia, that a high outlay is required in order to make the workpieces outwardly leaktight.
In some of the embodiments of fuel injection valves described in the already mentioned WO-A-02/086309, the valve seat part is designed as a nozzle body which is separate from the valve housing and which is provided with the injection orifices and with the valve seat for the injection valve member. This nozzle body is fastened to the housing by means of a welded joint. Since the nozzle body consists of a different, as a rule more wear-resistant material from that of the housing, problems during welding may arise on account of the different material properties. Moreover, the welded joint is subjected to very high stress, on the one hand, due to the high system pressure prevailing in the fuel injection valve and, on the other hand, owing to the impingement of the injection valve member onto the nozzle body during closing. The quality of the welded joint therefore has to satisfy very stringent requirements.
The injection valve member of the fuel injection valves described in the abovementioned WO-A-02/086309 is likewise exposed to high mechanical stresses at its end facing the valve seat part or nozzle body, specifically for the same reasons as those mentioned above in connection with the valve seat part or the nozzle body. This, above all, when the nozzle body consists of a more wear-resistant material than the injection valve member.
One object of the present invention is to connect a nozzle body of a fuel injection valve to the housing of said fuel injection valve in a simple and reliable way.
This object is achieved by way of a fuel injection valve as recited in the claims.
The valve seat part, provided on its outside with a conical seat surface can be brought to bear from inside the housing against the likewise conical bearing surface on the housing. As a result of the self-locking configuration of the seat surface and the bearing surface, the valve seat part is held firmly and sealingly in the housing.
Another object of the present invention is to allow for a simple and cost-effective manufacturing of a fuel injection valve.
This object is achieved by means of a method for producing a fuel injection valve as recited in the method claims.
Preferred embodiments of the fuel injection valve and the method according to the invention are claimed in the dependent claims.
Other exemplary embodiments and advantages of the present invention may be ascertained by reviewing the present disclosure and the purely diagrammatic accompanying Figures.
The present invention is further described in the detailed description which follows, in reference to the noted plurality of drawings by way of non-limiting examples of embodiments of the present invention, in which like reference numerals represent similar parts throughout the several views of the drawings, and wherein:
The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show structural details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the present invention may be embodied in practice.
The fuel injection valve 1, which is illustrated diagrammatically in
In the valve seat element 2b, a valve seat part 4 is held, which is designed as a nozzle body 4a separate from the valve seat element 2b and which has a valve seat 5 and injection orifices 6. The valve seat part 4 may, under certain circumstances, even be produced in one piece with the valve seat element 2b, as shown, for example, in
Inside the housing 2, that is to say in the bore 7, an injection valve member 9 is arranged, which is designed as a valve needle and is coaxial with respect to the longitudinal axis A of the housing 2 and which, in the closing position shown in
Thus far, and with the exception of the mounting of the valve seat part 4 in the valve seat element 2b, the fuel injection valve 1 illustrated in
In contrast to the abovementioned known fuel injection valves, the fuel injection valve 1 according to
The type of action of the throughflow-quantity limiting valve 14 is similar to the type of action, described in DE-A-43 44 190, of the shut-off valves which are shown there.
In the normal operating state between the injection operations, the valve body 15 assumes its open position. When, during an injection operation, the injection orifices 6 are opened by the injection valve member 9 being lifted off from the valve seat 5, a pressure drop occurs on the injection side, which brings about a movement of the valve body 15, acted upon on its end face 19 by the high operating pressure, out of the open position toward the closing position counter to the force of the spring element 23. In this case, however, the valve body 15 does not move into its closing position. At the end of the injection operation as a result of the closing of the injection orifices 6 by the injection valve member 9, the valve body 15 comes to a standstill in an intermediate position between its open position and its closing position. In this intermediate position, fuel afterflows via the annular gap 18. On account of the pressure rising again on that side of the valve body 15 which faces the valve seat part 4, and under the action of the spring element 23, the valve body 15 moves back into its open position again.
If, however, as a result of a fault, the injection valve member 9 remains in its open position and therefore the pressure drop on the injection side persists, the valve body 15 moves into its closing position, in which it bears with its sealing surface 21 against the seat surface 22. In this closing position, the throughflow of fuel to the valve seat 5 is thus interrupted. This means that only fuel quantity which can flow through the narrow guide between the guide portion 9c of the injection valve member 9 and the valve body 15 (leakage quantity) can afterflow into the combustion space of the corresponding cylinder. This leakage quantity is only very small, however, on account of the configuration of this guide between the valve body 15 and the injection valve member 9 as a close sliding fit. In the event of damage, therefore, at best, combustion under part load can occur in the affected cylinder.
As already mentioned, both the sealing surface 21 on the valve body 15 and the seat surface 22 on the valve seat element 2b are designed as portions of enveloping surfaces of circular cones, the apex angles of which are designed in such a way that a selflocking action occurs when the valve body 15 is in the closing position. For this purpose, these circular cones have an apex half angle of 2°-7°. The result of this selflocking action is that, with the engine stopped, that is to say in the absence of feed pressure, the valve body 15 does not lift off automatically from the seat surface 22. Consequently, in the event of a defective fuel inlet valve 1, even when the engine is restarted, no fuel can pass into the cylinder combustion space (with the exception of the small leakage quantity which can flow through the close sliding fit between the valve body 15 and the injection valve member 9).
The annular part 15b of the valve body 15 has a relatively large wall thickness. If, then, the valve body 15 is in its closing position and the high fuel pressure (for example 2000 bar and above) prevails in the high-pressure space 8, upstream of the seat surface 22, that is to say also in the annular gap 18, then the annular part 15b is compressed in the radial direction. When the feed pressure falls, the annular part 15b expands again, thus resulting in a clamping of the valve body 15 against the conical seat surface 22.
An engine having a fuel injection valve 1 with an integrated throughflow-quantity limiting valve 14 can thus be stopped and restarted, without a defective fuel injection valve 1 leading to engine overload. The engine thus has emergency running properties, even after a stop.
As already mentioned, in the intermediate positions of the valve body 15, the annular gap 18 forms a fuel throughflow connection. Such a connection may also take place in another way, for example by means of at least one longitudinal groove, extending in the direction of the longitudinal axis A of the housing 2, on the outside of the valve body 15 or in the wall 16a of the valve chamber.
The valve body 15 may also have a cross-sectional form other than that shown and, for example, have a T-shaped cross section. In such a cross-sectional form, contrary to what is shown in
As already mentioned, the valve seat part 4 held in the valve seat element 2b is designed as a nozzle body 4a separate from the valve seat element 2b. With reference to
As is known from WO-A-02/086309 already mentioned earlier (see, for example,
The nozzle body 4a has on its outside a conical seat surface 26 which is formed by a portion of the enveloping surface of a straight circular cone, the axis of which coincides with the longitudinal axis A of the housing 2. The nozzle body 4a bears with this seat surface 26 against a likewise conical bearing surface 27 which is formed in the valve seat element 2b. This bearing surface 27 is likewise formed by a portion of the enveloping surface of a straight circular cone, the axis of which coincides with the longitudinal axis A of the housing 2. The apex half angles 28 of the two circular cones forming the seat surface 26 and the bearing surface 27 are selected such that the nozzle body 4a is held selflockingly and sealingly in the valve seat element 2b. These apex half angles 28 amount to 2°-7°.
As may be gathered from
During the production of the nozzle body 4a, both the valve seat 5 and the seat surface 26 are formed in the same chucking of the nozzle body 4a by grinding. A guide surface 2′ for guiding the guide part 9b of the injection valve member 9 and the bearing surface 27 are likewise ground on the valve seat element 2b in the same chucking of the valve seat element 2b. For this purpose, the grinding tool (grinding mandrel) is preferably introduced into the valve seat element 2b from the side of the bearing surface 27.
In a variant, not shown, of the fuel injection valve 1 shown in
In the variant described above, the housing part 2a and the valve seat element 2b may also be produced in one piece and form part of the housing 2. In this case, the tension nut 3, as mentioned, may be dispensed with. In this instance, the machining of the guide surface 2′ and of the bearing surface 27 from the side of the bearing surface 27 is particularly advantageous.
It is also possible for the nozzle body 4a to be designed according to the invention, as described, in the case of fuel injection valves in which the supply of fuel to the valve seat 5 takes place via a supply duct offset laterally with respect to the longitudinal axis A of the housing 2 (instead of via the central high-pressure space 8, as shown).
As explained above, the valve seat part 4 designed as a separate nozzle body 4a is produced from a more wear-resistant (harder) material than the housing 2, thus entailing a prolongation of the useful life of the valve seat part 4. With reference to
In the exemplary embodiments shown in
In the embodiment according to
In the variant shown in
In the embodiment shown in
The spherical insert part 30 has an essentially linear sealing surface 31′, the diameter of which is designated by D2. This diameter D2 is smaller than the diameter D1 of the bearing surface 38 with which the insert part 30 bears against the wall 37a of the recess 37.
The insert part 30 lies loosely in the recess 37, that is to say it is not connected fixedly to the contiguous portion 9′ of the injection valve member 9. When the injection valve member 9 is being lifted off away from the valve seat 5 in order to open the injection orifices 6, the insert part 30 follows the contiguous portion 9′ of the injection valve member 9, specifically for the following reasons: with the injection valve member 9 located in the closing position (as illustrated in
It goes without saying that the tip 9a of the injection valve member 9 may be designed as a separate insert part 30 even when the fuel valve 1 is not designed with a throughflow limiting valve 14, and irrespective of whether the valve seat part 4 is designed as a nozzle body 4a separate from the housing 2 and/or from the valve seat element 2b or is in one piece with the housing 2.
In the embodiment according to
The valve seat part 4, like the nozzle body 4a of the embodiments according to
During mounting, the valve seat part 4 is inserted into the housing 2 from above.
The valve seat part 4 is designed as an elongate component and has an outside diameter which is smaller than the outside diameter of the housing 2. In the embodiment according to
In the embodiment shown in
It is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. While the present invention has been described with reference to an exemplary embodiment, it is understood that the words which have been used herein are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present invention in its aspects. Although the present invention has been described herein with reference to particular means, materials and embodiments, the present invention is not intended to be limited to the particulars disclosed herein; rather, the present invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1248/03 | Jul 2003 | CH | national |
The present application is a continuation application of International Application PCT/CH2004/000451 filed on Jul. 14, 2004, which, in turn, is based on Swiss Patent Application No. 1248/03, filed on Jul. 17, 2003, the disclosures of which are expressly incorporated by reference herein in their entireties.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/CH04/00451 | Jul 2004 | US |
| Child | 11331201 | Jan 2006 | US |
