Patent Application
20050087624
The present invention relates to an injector for injecting fuel into a combustion chamber of an internal combustion engine.
Different types of fuel injectors are known e.g. for common rail systems. An injector of conventional construction comprises a nozzle needle which is connected indirectly via a plunger, or directly, to a control chamber to which pressure is applied. If the nozzle and control chamber are at equal pressure, a resulting force is generated by the geometrically defined ratio of the surfaces on which the pressure is acting. If, for example, the surface area at the nozzle is smaller than the area at the plunger, a resulting force is generated which presses the nozzle needle into its seat, thereby closing the nozzle.
The control chamber is connected via a so-called fill port to a region of high pressure from an accumulator (rail) which is simultaneously also routed to the nozzle. The control chamber is further connected to a limiting valve via a so-called spill port. As the spill port has a larger flow cross section than the fill port, the opening of the limiting valve causes the pressure in the control chamber to drop. This pressure drop in the control chamber causes the resulting force at the nozzle needle to change so that the nozzle needle lifts from its seat and fuel can flow out through the injection bores into a combustion chamber of the internal combustion engine. In prior art injectors, it has been the practice to incorporate the control chamber and the fill port or spill port in the injector housing in each case, with the result that the injector body is of relatively complicated construction and is relatively complicated to manufacture in production engineering terms, as a large number of operations must be performed on the injector body.
An object of the present invention is, therefore, to provide an injector for injecting fuel that can be used particularly in a common rail system, is of simple construction and can be inexpensively manufactured.
This and other objects can be achieved by an injector for injecting fuel into a combustion chamber of an internal combustion engine, comprising an injector body, a nozzle needle, a control device in order to control a pressure in a control chamber for actuating the nozzle needle, a fill port and a spill port both of which are fluidically connected to the control chamber, wherein the fill port and the spill port are disposed in a porting module implemented as a separate component.
In the porting module a resetting element can be disposed for resetting the control device. In the porting module a recess can be formed which provides at least a sub-region of the control chamber. The fill port can be disposed in the radial direction of the injector. Between the injector body and the porting module an annular gap can be implemented via which fuel is supplied to the fill port. The annular gap can be sealed in the axial direction of the injector. The seal can be achieved by means of cutting edges. The porting module can be disposed in a stepped bore having at least two steps of the injector body, wherein the annular gap being sealed in the axial direction at the steps of the stepped bore. The annular gap can be sealed in the radial direction of the injector. The sealing can be performed by an elastic seal and/or a press fit between the porting module and the injector body.
The injector according to the invention is designed in such a way that a fill port and a spill port are provided in a porting module implemented as a separate component. Disposing the two ports in a separate component enables manufacturing advantages to be achieved, as the ports which must be manufactured with a particularly high degree of accuracy can be inserted in the separate component in a readily accessible manner. The porting module is then mounted in the injector.
It is further preferred to dispose in the separate porting module a resetting element, e.g. a helical spring, for resetting the control device of the injector, thereby enabling the injector according to the invention to be of more compact design.
More advantageously there is formed, in the separate porting module, a recess which provides at a sub-region of the injector control chamber, thereby enabling the injector according to the invention to be implemented even more compactly in the axial direction. In order to provide an even more compact injector, the fill port is preferably disposed in the radial direction relative to the injector axis, it being particularly preferred that the fill port be supplied with pressurized fuel via an annular gap disposed between the injector body and the separate porting module.
In order to achieve tight sealing of the annular gap between the injector body and the separate porting module, the annular gap is preferably sealed in the axial direction, it being particularly preferred that the sealing be achieved using cutting edges which, during assembly, undergo plastic deformation or cause plastic deformation in the other component so as to provide a tight seal.
It is particularly preferred that the porting module be disposed in a stepped bore of the injector body with at least two steps, the annular gap being sealed at the steps of the stepped bore in the axial direction. In the case of sealing by means of cutting edges, said cutting edges can be implemented either in the porting module or at the steps in the injector body.
Another possible means of sealing the annular gap between the injector body and the porting module is to provide sealing in the radial direction of the injector, said radial sealing being provided e.g. by means of an elastic ring seal or a press fit.
It should be noted, moreover, that it is obviously also possible to provide a seal between the injector body and the separate porting module both in the axial direction and in the radial direction.
The invention will now be described with reference to a preferred embodiment in conjunction with the accompanying drawing.
The single FIGURE shows a schematic sectional view of a region of an injector incorporating the porting module according to the invention.
As
As can be further seen from
As
As the porting module 5 is implemented as a separate component, a seal must be implemented between the porting module 5 and the injector body 2. As shown in
When the porting module 5 is mounted in the injector body 2, plastic deformation of the cutting edges 9 and 10 takes place at the steps 11 and 12 of the stepped bore, causing the surfaces of the two components 2 and 5 to mate in an ideal manner, thereby providing a very good seal. This seal remains tight even at the very high pressures obtaining e.g. in common rail injection systems. In addition, by providing the plastically deforming cutting edges 9 and 10, the manufacturing-induced length differences between the spacings of the steps 11, 12 of the stepped bore and/or the spacings of the shoulders formed on the porting module 5 between the cutting edges 9 and 10 can be compensated. This makes it possible for the manufacturing tolerances to be less tightly selected, thereby enabling the injector to be manufactured more cheaply. Moreover, by providing the porting module 5 as a separate individual component, the bores for the fill port 6 and the spill port 7 can be implemented quickly, easily and with a high degree of accuracy. Likewise the cutting edges 9, 10 provided on the porting module 5 can be produced very inexpensively, e.g. by turning.
The injector 1 according to the invention operates as follows. When fuel is to be injected, the valve 15 is operated via an actuator (not shown) and moved in the direction of the nozzle needle 3 so that the valve 15 lifts from its valve seat 18, thereby opening a connection between the control chamber 4 via the drain port 7 and the open valve 15 to the return the flow line 16. This causes the pressure in the control chamber 4 to fall so that the nozzle needle 3 moves into the control chamber 4 in the axial direction X-X of the injector, causing the nozzle needle 3 to lift from its seat so that at least one nozzle is uncovered and fuel is injected by the nozzle into a combustion chamber of an internal combustion engine, the injection lasting as long as the valve 15 remains in its open state. The opening of the valve 15 takes place against the spring force of the spring 14.
When injection is to be terminated, the valve 15 is again operated via an actuator so that it returns to its starting position, in which the valve seat 18 is closed, by resetting of the spring 14, thereby again interrupting the connection between the control chamber 4 and the return flow line 16 so that the original pressure can build up in the control chamber 4, as pressurized fuel is supplied via the fill port 6. This causes the nozzle needle 3 to return to its starting position and close the injector nozzle, thereby terminating fuel injection.
During actuation of the control valve 15 and of the nozzle needle 3, continuously tight sealing of the annular gap 17 between the injector module 2 and the porting module 5 can be ensured at the steps 11 and 12 respectively of the injector body 2. It should be noted that the cutting edges 9, 10 are obviously not only provided in the porting module 5 but that cutting edges can also be provided in the same way at the steps 11, 12 of the injector body which become plastically deformed when the porting module 5 is mounted, thereby producing a seal between the injector body 2 and the porting module 5.
The present invention therefore relates to an injector for injecting fuel into a combustion chamber of an internal combustion engine. The injector comprises an injector body 2, a nozzle needle 3 and a control device 13 in order to control a pressure in a control chamber 4 for actuating the nozzle needle 3. The injector 1 additionally comprises a fill port 6 and a spill port 7 which are fluidically connected to the control chamber 4, said fill port 6 and said spill port 7 being disposed in a porting module 5 implemented as a separate component.
The above description of the exemplary embodiment according to the present invention is used for illustrative purposes only and is not to be taken in a limiting sense. Within the scope of the invention, various changes and modifications are possible without departing from the scope of the invention and its equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10220931.6 | May 2002 | DE | national |
This application is a continuation of copending International Application No. PCT/DE03/01448 filed May 6, 2003 which designates the United States, and claims priority to German application no. 102 20 931.6 filed May 10, 2002.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/DE03/01448 | May 2003 | US |
| Child | 10984060 | Nov 2004 | US |
