Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
1999-02-26
2001-01-23
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
Reexamination Certificate
active
06176221
ABSTRACT:
PRIOR ART
The invention relates to a fuel delivery system for a fuel injection nozzle, inserted into a cylinder head of an internal combustion engine, having a tubular neck penetrating a passage in the cylinder head, the neck being tightly joined on the inlet side to the connection piece of an inlet tube and being pressed on the outlet side axially with a sealing face against a conical seat face, disposed on the nozzle holder of the fuel injection nozzle, by means of a union screw screwed into the passage of the cylinder head. One such fuel delivery system is disclosed for instance in European Patent Disclosure EP 0 569 727 A1. In such a fuel delivery system, it is especially advantageous that it enables easy assembly; any slight misalignment of the nozzle holder of the injection nozzle in the cylinder head can be compensated for.
In such fuel delivery systems, however, it can happen that the line pressure after an injection event decreases so rapidly that while the nozzle needle is still open a pressure is established in the fuel injection nozzle that is below the combustion chamber pressure. The result is an expulsion or “blowback” of the combustion gases into the fuel injection nozzle. As a result of this blowback of combustion gases, coke is introduced into the nozzle chamber of the fuel injection nozzle, which is deleterious to the surface life of the fuel injection nozzle.
It is therefore the object of the invention to refine a fuel delivery system of the generic type defined above in such a way as to avert any blowback of the combustion chamber gases into the nozzle chamber.
ADVANTAGES OF THE INVENTION
In a fuel delivery system of the type defined at the outset, this object is attained according to the invention in that a check valve is disposed downstream of the conical seat face in the inlet conduit of the injection nozzle, which check valve permits a delivery of fuel solely in the direction of the combustion chamber of the engine.
By means of this check valve disposed downstream of the conical seat face in the inlet conduit, a blowback of combustion gases into the nozzle chamber is averted in an especially advantageous way, because it is simple to accomplish. Specifically, as soon as a pressure oriented from the combustion chamber into the nozzle chamber is applied to the check valve, this valve closes and thus prevents the combustion gases from entering the nozzle chamber.
Purely in principle, the most various embodiments of the check valve are conceivable. One advantageous embodiment provides that the check valve includes a sealing sleeve, disposed in an opening, and on one end of which conical sealing faces are disposed, and on whose other end a sealing element is provided, which upon imposition of a pressure oriented in the direction of the engine combustion chamber opens the sealing sleeve, and upon a pressure oriented in the reverse direction tightly closes the sealing sleeve. Such a sealing sleeve can be manufactured and installed in a simple way. Another advantage here is that the conical sealing face is disposed on the sealing sleeve itself, so that not only is unproblematic coupling of the inlet tube directly to the sealing sleeve possible, but also the sealing sleeve is secured thereby.
With regard to the sealing element, once again the most various embodiments are conceivable. One advantageous embodiment provides that the sealing element is a throttle plate, which is partly passable and is disposed axially in an opening downstream of the sealing sleeve between it and a bearing face, which throttle plate upon imposition of a pressure oriented toward the combustion chamber is pressed by the sealing sleeve toward the bearing face, the db thereby being opened, and which upon imposition of a pressure oriented away from the combustion chamber is pressed by the bearing face away onto a plane surface on the underside of the sealing sleeve, thereby closing the sealing sleeve. Such a throttle plate can in particular be manufactured and installed simply.
The bearing face on the nozzle holder can be embodied in the most various ways.
One embodiment provides that the bearing face, embodied on the nozzle holder, is an annularly encompassing shoulder in the nozzle holder.
In another, highly advantageous embodiment, it is provided that the bearing face is embodied frustoconically. The conical embodiment of the bearing face and thus also of the region of the throttle plate oriented toward the bearing face has the major advantage in particular that upon imposition of very high pressures, which can occur in an internal combustion engine and are on the order of magnitude of about 1800 bar, the bearing face is practically undamaged, because an abrupt transition, which should be avoided if at all possible, is not created.
On the one hand in order to assure good sealing off of the sealing sleeve by the throttle plate and on the other to present the least possible hindrance to the fuel flowing through the fuel injection nozzle into the combustion chamber, it is provided in an advantageous embodiment that the throttle plate has a centrally disposed sealing face, whose diameter is greater than that of the opening in the sealing sleeve toward the combustion chamber, and that outside the sealing face it has passable openings, whose total cross section is greater than or equal to that of the inlet tube.
To assure that if a very high pressure is imposed the throttle plate will not be destroyed, and on the other hand to enable simple manufacture of the throttle plate and especially of the bearing face, it is provided in an advantageous embodiment that a slotted sleeve provided with a transverse groove is disposed, downstream of the throttle plate, in an opening whose diameter is less than that of the sealing sleeve.
This slotted sleeve acts in a sense as a resilient bearing face for the throttle plate, so that a hard impact of the throttle plate on this bearing face is averted, thus increases the service life of the throttle plate, which can be embodied as a simple platelike element. Furthermore, because of the sealing sleeve, it is also unnecessary to embody a bearing face in the fuel delivery line, this making its manufacture simpler as well.
In another, highly advantageous embodiment, it is provided that a stop bush is press-fitted into the inlet conduit downstream of the throttle plate and has a central opening, which at least partly overlaps the opening or openings in the throttle plate and whose outer diameter is greater than or equal to that of the throttle plate.
This stop bush is easy to manufacture, because only a central opening, which can for instance be a bore, needs to be made. Because its outer diameter is greater than or equal to that of the throttle plate, it furthermore forms a very good seat for the throttle plate in the open state of the check valve. By press-fitting into the inlet conduit, it is assured that an impact of the throttle plate on the stop bush will not cause any shifting of, damage to, or other impairment of the stop bush and of the fuel delivery line.
In another embodiment, it is provided that the check valve is a partly split bolt with a retaining collar, which is disposed in an opening, formed complementary to it, of the fuel delivery line and has spring arms, on its side toward the combustion chamber, that upon imposition of a pressure in the direction of the combustion chamber are pressed toward the axis of the bolt and thereby open an annular passage in the opening, and that upon a pressure reduction yield radially outward away from the axis in the direction of the opening and close the opening.
An especially advantageous aspect of this embodiment is that the check valve is on one piece and therefore is not only simple to manufacture but also simple to install.
In an embodiment of such a check valve, it is preferably provided that the bolt, on its side toward the engine combustion chamber, has a blind opening disposed centrally between the spring arms, into which opening returning fuel flows and is deflected and thereby exerts an additional forc
Castro Arnold
Greigg Edwin E.
Greigg Ronald E.
Robert & Bosch GmbH
Yuen Henry C.
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