Coupling device

The coupling device has a fuel injector cup, a first and second flange, a shell and fixing element. The fuel injector cup has a central longitudinal axis and can be hydraulically coupled to the fuel rail and engages a fuel inlet portion. The first flange is fixedly coupled to the cup and the second flange to the injector. The shell has first and second projections between which the flanges are axially arranged, and the flanges are in mechanical cooperation with the shell element to retain the injector in the cup in central longitudinal axis direction. The fixing element is arranged on a circumferential outer surface of the shell and prevents a radial movement of it relative to the flanges. The fixing element has a radially spring-loaded element which engages with a recess in the shell element to prevent an axial movement of the fixing element relative to the shell.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to EP Patent Application No. 09009637 filed Jul. 24, 2009, the contents of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The invention relates to a coupling device for hydraulically and mechanically coupling a fuel injector to a fuel rail of a combustion engine.

BACKGROUND

Coupling devices for hydraulically and mechanically coupling a fuel injector to a fuel rail are in widespread use, in particular for internal combustion engines. Fuel can be supplied to an internal combustion engine by the fuel rail assembly through the fuel injector. The fuel injectors can be coupled to the fuel injector cups in different manners.

In order to keep pressure fluctuations during the operation of the internal combustion engine at a very low level, internal combustion engines are supplied with a fuel accumulator to which the fuel injectors are connected and which has a relatively large volume. Such a fuel accumulator is often referred to as a common rail.

Known fuel rails comprise a hollow body with recesses in form of fuel injector cups, wherein the fuel injectors are arranged. The connection of the fuel injectors to the fuel injector cups that supply the fuel from a fuel tank via a low or high-pressure fuel pump needs to be very precise to get a correct injection angle and a sealing of the fuel.

SUMMARY

According to various embodiments, a coupling device for hydraulically and mechanically coupling a fuel injector to a fuel rail can be created which is simply to be manufactured and which facilitates a reliable and precise connection between the fuel injector and the fuel injector cup without a resting of the fuel injector on the cylinder head.

According to an embodiment, a coupling device for hydraulically and mechanically coupling a fuel injector to a fuel rail of a combustion engine, may comprise: a fuel injector cup having a central longitudinal axis and being designed to be hydraulically coupled to the fuel rail and to engage a fuel inlet portion of the fuel injector, a first flange being fixedly coupled to the fuel injector cup and a second flange being fixedly coupled to the fuel injector, at least one shell element, the shell element comprising a first projection and a second projection, the flanges being axially arranged between the first projection and the second projection, and the shell element being designed and arranged in a way that the flanges are in mechanical cooperation with the shell element to retain the fuel injector in the fuel injector cup in direction of the central longitudinal axis, and a fixing element being arranged on a circumferential outer surface of the shell element and being designed to prevent a radial movement of the shell element relative to the flanges, wherein the fixing element comprises at least one radially spring-loaded element which is arranged and designed in a manner that the spring-loaded element is in engagement with a recess in the shell element to prevent an axial movement of the fixing element relative to the shell element.

According to a further embodiment of the above coupling device, the spring-loaded element can be shaped as a sphere.

According to another embodiment, a coupling device for hydraulically and mechanically coupling a fuel injector to a fuel rail of a combustion engine, may comprise: a fuel injector cup having a central longitudinal axis and being designed to be hydraulically coupled to the fuel rail and to engage a fuel inlet portion of the fuel injector, a first flange being fixedly coupled to the fuel injector cup and a second flange being fixedly coupled to the fuel injector, at least one shell element, the shell element comprising a first projection and a second projection, the flanges being axially arranged between the first projection and the second projection, and the shell element being designed and arranged in a way that the flanges are in mechanical cooperation with the shell element to retain the fuel injector in the fuel injector cup in direction of the central longitudinal axis, and a fixing element being arranged on a circumferential outer surface of the shell element and being designed to prevent a radial movement of the shell element relative to the flanges, wherein a ring element is arranged in axial direction adjacent to the fixing element, the ring element being in mechanical cooperation with the fuel injector cup and/or the shell element and being designed to prevent an axial movement of the fixing element relative to the shell element.

According to a further embodiment of this coupling device, the ring element can be designed to enable an elastic expansion of the ring element in radial direction.

According to a further embodiment of any of the above coupling devices, the coupling device may comprise at least two shell elements. According to a further embodiment of any of the above coupling devices, the projection may form a shoulder being in mechanical cooperation with the fixing element to prevent a movement of the fixing element relative to the shell element at least in one axial direction. According to a further embodiment of any of the above coupling devices, the fixing element may have a tubular shape. According to a further embodiment of any of the above coupling devices, the fuel injector cup may comprise a groove, a first snap ring being arranged in the groove, with the groove and the first snap ring being arranged and designed to form a positive fitting coupling between the first flange and the fuel injector cup which is designed to prevent a movement of the first flange relative to the fuel injector cup at least in a first direction of the central longitudinal axis. According to a further embodiment of any of the above coupling devices, the first flange may be in one part with the fuel injector cup. According to a further embodiment of any of the above coupling devices, the fuel injector may comprise a groove, a second snap ring being arranged in the groove of the fuel injector, with the groove of the fuel injector and the second snap ring being arranged and designed to form a positive fitting coupling between the second flange and the fuel injector which is designed to prevent a movement of the second flange relative to the fuel injector at least in a second direction of the central longitudinal axis contrary to the first direction of the central longitudinal axis. According to a further embodiment of any of the above coupling devices, the second flange may be in one part with the fuel injector.

DETAILED DESCRIPTION

According to a first aspect various embodiments are distinguished by a coupling device for hydraulically and mechanically coupling a fuel injector to a fuel rail of a combustion engine. The coupling device comprises a fuel injector cup having a central longitudinal axis and being designed to be hydraulically coupled to the fuel rail and to engage a fuel inlet portion of the fuel injector. The coupling device comprises a first flange being fixedly coupled to the fuel injector cup and a second flange being fixedly coupled to the fuel injector. The coupling device further comprises at least one shell element. The shell element comprises a first projection and a second projection. The flanges are axially arranged between the first projection and the second projection. The shell element is designed and arranged in a way that the flanges are in mechanical cooperation with the shell element to retain the fuel injector in the fuel injector cup in direction of the central longitudinal axis. The coupling device further comprises a fixing element which is arranged on a circumferential outer surface of the shell element and is designed to prevent a radial movement of the shell element relative to the flanges. The fixing element comprises at least one radially spring-loaded element which is arranged and designed in a manner that the spring-loaded element is in engagement with a recess in the shell element to prevent an axial movement of the fixing element relative to the shell element. This has the advantage that a fast and secure coupling of the fuel injector in the fuel injector cup is possible. The coupling device can resist the high fuel pressures in the fuel injector and the fuel injector cup. Furthermore, the coupling of the fuel injector with the fuel rail by the flanges of the fuel injector and the fuel injector cup allows an assembly of the fuel injector and the fuel rail without a further metallic contact between the fuel injector and further parts of the combustion engine. Consequently, a noise transmission between the fuel injector and further parts of the combustion engine can be kept small. The fixing element can ensure a secure coupling between the flanges and the shell elements. The spring-loaded element enables a secure arrangement of the fixing element in the recess to prevent a decoupling of the fixing element from the shell element. Furthermore, no particular adjustment is required to obtain a proper alignment between the fuel rail and the fuel injector.

In an embodiment the spring-loaded element is shaped as a sphere. This has the advantage that the spring-loaded sphere may hold the fixing element in its position relative to the shell element in a very exact manner. Therefore, a proper performance of the fuel injector/fuel rail assembly can be obtained.

According to a second aspect, various embodiments are distinguished by a coupling device for hydraulically and mechanically coupling a fuel injector to a fuel rail of a combustion engine. The coupling device comprises a fuel injector cup having a central longitudinal axis and being designed to be hydraulically coupled to the fuel rail and to engage a fuel inlet portion of the fuel injector. The coupling device comprises a first flange being fixedly coupled to the fuel injector cup and a second flange being fixedly coupled to the fuel injector. The coupling device further comprises at least one shell element. The shell element comprises a first projection and a second projection. The flanges are axially arranged between the first projection and the second projection. The shell element is designed and arranged in a way that the flanges are in mechanical cooperation with the shell element to retain the fuel injector in the fuel injector cup in direction of the central longitudinal axis. The coupling device further comprises a fixing element which is arranged on a circumferential outer surface of the shell element and is designed to prevent a radial movement of the shell element relative to the flanges. A ring element is arranged in axial direction adjacent to the fixing element. The ring element is in mechanical cooperation with the fuel injector cup and/or the shell element and is designed to prevent an axial movement of the fixing element relative to the shell element. This has the advantage that a fast and secure coupling of the fuel injector in the fuel injector cup is possible. The coupling device can resist the high fuel pressures in the fuel injector and the fuel injector cup. Furthermore, the coupling of the fuel injector with the fuel rail by the flanges of the fuel injector and the fuel injector cup allows an assembly of the fuel injector and the fuel rail without a further metallic contact between the fuel injector and further parts of the combustion engine. Consequently, a noise transmission between the fuel injector and further parts of the combustion engine can be kept small. The fixing element can ensure a secure coupling between the flanges and the shell elements. The ring element enables a secure arrangement of the fixing element relative to the shell element to prevent a decoupling of the fixing element from the shell element. Furthermore, no particular adjustment is required to obtain a proper alignment between the fuel rail and the fuel injector.

According to an embodiment according to the second aspect, the ring element is designed to enable an elastic expansion of the ring element in radial direction. This has the advantage that the ring element can be easily removed from the fuel injector cup for a simple mounting and demounting of the fuel injector to or from the fuel injector cup.

In a further embodiment according to the first and the second aspect, the coupling device comprises at least two shell elements. By this, a simple mounting and demounting of the shell elements to or from the flanges is possible. Consequently, a simple mounting and demounting of the fuel injector to or from the fuel injector cup can be carried out. Furthermore, an axial symmetric arrangement of the shell elements is possible. Consequently, an axially symmetrical distribution of forces in the coupling device is possible.

In a further embodiment according to the first and the second aspect, the projection forms a shoulder being in mechanical cooperation with the fixing element to prevent a movement of the fixing element relative to the shell element at least in one axial direction.

In a further embodiment according to the first and the second aspect, the fixing element has a tubular shape. By this, the fixing element can be easily arranged on the surface of the shell element. Furthermore, the fixing element can enable a secure coupling between the flanges and the shell elements.

In a further embodiment according to the first and the second aspect, the fuel injector cup comprises a groove, and a first snap ring is arranged in the groove and is designed to fixedly couple the first flange to the fuel injector cup. The groove and the first snap ring are arranged and designed to form a positive fitting coupling between the first flange and the fuel injector cup which is designed to prevent a movement of the first flange relative to the fuel injector cup at least in a first direction of the central longitudinal axis. This may allow a simple construction of the coupling device which enables to carry out a fast and secure but reversible coupling of the first flange to the fuel injector cup.

In a further embodiment according to the first and the second aspect, the first flange is in one part with the fuel injector cup. This has the advantage that a very secure coupling of the fuel injector to the fuel injector cup is possible. Furthermore, a simple machining of the first flange together with the fuel injector cup is possible.

In a further embodiment according to the first and the second aspect, the fuel injector comprises a groove, a second snap ring is arranged in the groove of the fuel injector and is designed to fixedly couple the second flange to the fuel injector. The groove of the fuel injector and the second snap ring are arranged and designed to form a positive fitting coupling between the second flange and the fuel injector which is designed to prevent a movement of the second flange relative to the fuel injector at least in a second direction of the central longitudinal axis contrary to the first direction of the central longitudinal. This may allow a simple construction of the coupling device which enables to carry out a fast and secure but reversible coupling of the second flange to the fuel injector.

In a further embodiment according to the first and the second aspect, the second flange is in one part with the fuel injector. This has the advantage that a very secure coupling of the fuel injector to the fuel injector cup is possible. Furthermore, a simple machining of the second flange together with the fuel injector is possible.

Elements of the same design and function that occur in different illustrations are identified by the same reference character.

A fuel feed device10is assigned to an internal combustion engine22(FIG. 1) which can be a diesel engine or a gasoline engine. It includes a fuel tank12that is connected via a first fuel line to a fuel pump14. The output of the fuel pump14is connected to a fuel inlet16of a fuel rail18. In the fuel rail18, the fuel is stored for example under a pressure of about 200 bar in the case of a gasoline engine or of about 2,000 bar in the case of a diesel engine. Fuel injectors20are connected to the fuel rail18by fuel injector cups30and the fuel is fed to the fuel injectors20via the fuel rail18.

FIG. 2shows the fuel injector20which has a fuel injector body21and is suitable for injecting fuel into a combustion chamber of the internal combustion engine22. The fuel injector20has a fuel inlet portion24and a fuel outlet portion25. The fuel injector cup30has a central longitudinal axis L.

Furthermore, the fuel injector20comprises a valve needle26taken in a cavity29of the fuel injector body21. On a free end of the fuel injector20an injection nozzle28is formed which is closed or opened by an axial movement of the valve needle26. In a closing position a fuel flow through the injection nozzle28is prevented. In an opening position fuel can flow through the injection nozzle28into the combustion chamber of the internal combustion engine22.

The fuel injector20has a groove27and the fuel injector cup30has a groove32. A first snap ring40is arranged in the groove32of the fuel injector cup30and a second snap ring42which is arranged in the groove27of the fuel injector20. A first flange36is in engagement with the first snap ring40and a second flange38is in engagement with the second snap ring42.

The first snap ring40enables a positive fitting coupling between the first flange36and the fuel injector cup30to prevent a movement of the first flange36relative to the fuel injector cup30in a first direction D1. Therefore, the first flange36is fixedly coupled to the fuel injector cup30. The second snap ring42enables a positive fitting coupling between the second flange38and the fuel injector20to prevent a movement of the second flange38relative to the fuel injector20in a second direction D2. Therefore, the second flange38is fixedly coupled to the fuel injector20. The first direction D1and the second direction D2are opposite directions of the central longitudinal axis L.

FIGS. 2 to 5show different embodiments of a coupling device50which is coupled to the fuel rail18of the internal combustion engine22.

The coupling device50comprises the fuel injector cup30, the first flange36, the second flange38, two shell elements44,45and a fixing element54. In further embodiments the number of shell elements can be one or greater than two.

The fuel injector cup30comprises an inner surface34and an outer surface35and is hydraulically coupled to the fuel rail18. Furthermore, the fuel injector cup30is in engagement with the fuel inlet portion24of the fuel injector20. The fuel inlet portion24of the fuel injector20comprises a sealing ring48with an outer surface49.

As shown in the embodiments ofFIGS. 3 and 5, the first flange36may be preferably in one part with the fuel injector cup30and the second ring38may be preferably in one part with the fuel injector20. By this a very rigid and very secure coupling between the fuel injector cup30and the fuel injector20is possible.

The shell elements44,45have substantially the form of half hollow cylinders. They are arranged in a way that together they are forming basically a cylinder (FIG. 4). At a first axial end the shell element44has a first projection44a.At a second axial end the shell element44has a second projection44b.The shell element45has respective projections45a,45bat opposing axial ends. The projections44a,44b,45a,45bhave planar surfaces which are facing the flanges36,38. The shell elements44,45have circumferential outer surfaces52.

The first flange36and the second flange38are axially arranged between the first projections44a,45aand the second projections44b,45b.Consequently, the first flange36and the second flange38are in engagement with the shell elements44,45to prevent a movement of the flanges36,38in direction of the central longitudinal axis L. By this, the fuel injector20is fixedly coupled to the fuel injector cup30in direction of the central longitudinal axis L.

Preferably, the fixing element54may have a tubular shape and is arranged on the circumferential outer surfaces52of the shell elements44,45.

As shown inFIG. 3, the fixing element54has at least one radially spring-loaded element46with a spring46a.Preferably, the spring46acan be a compression spring. Preferably, the spring-loaded element46may have a spherical shape and is in engagement with a recess47in the shell element44,45. By this an axial movement of the fixing element54relative to the shell element44,45may be prevented. Preferably, the fixing element54may comprise a plurality of spring-loaded elements46. This may prevent an axial movement of the fixing element54relative to the shell element44,45in a very secure manner. Preferably, the spring-loaded elements46can be distributed regularly at an inner surface of the fixing element54, i.e. the spring-loaded elements46are distributed with equal angle distances to each other. This may prevent an axial movement of the fixing element54relative to the shell element44,45in a very secure manner.

The fixing element54can couple the shell elements44,45fixedly to the flanges36,38. Thereby a movement of the shell elements44,45relative to the flanges36,38in a radial direction can be prevented.

As the first flange36is fixedly coupled to the fuel injector cup30, the second flange38is fixedly coupled to the fuel injector20and the first flange36is fixedly coupled to the second flange38by the shell elements44,45and the fixing element54, the fuel injector20is retained in the fuel injector cup30in direction of the central longitudinal axis L.

In the following, the assembly and disassembly of the fuel injector20and the fuel injector cup30according to the embodiment ofFIGS. 3 and 4will be described:

For assembling, the fuel inlet portion24of the fuel injector20is shifted into the fuel injector cup30in a way that the flanges36,38are in engagement with each other. Then, the shell elements44,45are shifted over the flanges36,38in radial direction towards the central longitudinal axis L and the fixing element54is shifted over the shell elements44,45in radial direction until the spring-loaded element46is in engagement with the recess47. Now, a state as shown inFIG. 3is obtained and the shell elements44,45are fixed against a movement in radial direction relative to the flanges36,38. As can be seen inFIG. 3, the inner surface34of the fuel injector cup30is in sealing engagement with the outer surface49of the sealing ring48. After the assembly process fuel can flow through the fuel injector cup30into the fuel inlet portion24of the fuel injector20without fuel leakage.

To disassemble the fuel injector20from the fuel injector cup30, the fixing element54is removed from the shell elements44,45and the shell elements44,45are removed from the flanges36,38. Then, the fuel injector20can be shifted away from the fuel injector cup30in axial direction and the fuel injector cup30and the fuel injector20can be separated from each other.

As shown inFIG. 5, the coupling device50comprises a ring element56which is arranged in axial direction relative and adjacent to the fixing element54. The ring element56is in mechanical cooperation with the fuel injector cup30and may prevent an axial movement of the fixing element54relative to the shell elements44,45. Preferably, the ring element56may be of a rubber or a plastic or may comprise a rubber or a plastic. The ring element56is elastically expandable in radial direction. Therefore, the ring element56can be easily disassembled from or assembled to the fuel injector cup30and the shell elements44,45during the assembly and disassembly of the fuel injector20and the fuel injector cup30.

The coupling of the fuel injector20with the fuel rail18by the flanges36,38and the shell elements44,45allows an assembly of the fuel injector20and the fuel injector cup30without a further metallic contact between the fuel injector20and the further parts of the combustion engine22. A sealing between the fuel injector body21and a combustion chamber of the combustion engine22can be carried out by a plastic element, in particular by a PTFE element. Consequently, noise transmission between the fuel injector20and further parts of the internal combustion engine can be kept small. Furthermore, a proper alignment between the fuel rail18and the fuel injector20is possible without any particular adjustment.