Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
1998-10-29
2001-08-21
Miller, Carl S. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S468000
Reexamination Certificate
active
06276336
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a pressure reservoir for a fuel supply system. The pressure reservoir is formed of an elongated hollow body with an inlet connection for communicating with a high-pressure pump and at least two outlet connections for communicating with injection valves.
Such pressure reservoirs are used above all in injection systems known by the name “common rail”, which makes it possible to keep the injection pressure and the injection quantity independent of the engine speed, and moreover to increase the injection pressure to above 1500 bar. In the common rail injection systems, fuel is pumped by a high-pressure pump out of a tank into the pressure reservoir, by way of which the fuel is present at injection valves that are each disposed in the cylinder heads of an engine. The pressure reservoir is generally tubular in shape and oriented parallel to the cylinder heads. The outlet connections for the injection valves disposed in the cylinder heads are generally disposed along the tubular body in a spacing equivalent to the spacings between individual injection valves.
The injection events into the cylinders are tripped by supplying current to the appropriate injection valves. The injection volume depends on the pressure prevailing at the injection valves and on the duration of the supply of electrical current. The injection events performed by the injection valves cause pressure fluctuations in the pressure reservoir. However, because of the position of the outlet connections that are distributed over the length of the tubular body, a variable effect on the individual injection valves and on the injection events performed by these injection valves can occur, and in particular can lead to variations in the respective injection volume.
To prevent such disadvantageous pressure fluctuations in the pressure reservoir that are tripped by the injection events, it is known from Published, Non-Prosecuted German Patent Application DE 195 32 599 A1 to divide the pressure reservoir into two individual reservoirs. In the application, each reservoir communicates with the common high-pressure pump via a respective distributor element. The individual reservoirs are then loaded in accordance with the ignition sequence of the engine, thus assuring that for the successive injection events, an unloaded individual reservoir will be available, and thus the pressure fluctuations tripped by one injection event cannot affect the next injection event. However, the embodiment involves increased production and installation expense, because both two pressure reservoirs and an additional distributor element have to be manufactured and installed in the engine compartment.
Furthermore, as in the conventional tubular pressure reservoirs, the outlet connections assigned to the various injection valves in the individual reservoirs used in Published, Non-Prosecuted German Patent Application DE 195 32 599 A1 are disposed along the tubular body. However, since in the region of the outlet connections the material load resulting from the internal pressure in the pressure reservoir is multiplied, the wall thickness and material strength in the region of the outlet connections must be oversized considerably compared with the other regions. This leads to both a high weight of the pressure reservoir and high costs for materials. Moreover, autofrettage is as a rule necessary as well.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a pressure reservoir for fuel supply systems, which overcomes the above-mentioned disadvantages of the prior art devices of this general type, which is favorable in terms of production costs and reliably prevents changes in the outflow volume to the individual injection valve connections that might be tripped by pressure fluctuations resulting from the injection events.
With the foregoing and other objects in view there is provided, in accordance with the invention, a pressure reservoir for a fuel supply system, including: an elongated hollow body having ends and an inlet connection for communicating with a high-pressure pump; and at least one end piece having at least two outlet connections for communicating with injection valves and disposed on at least one of the ends of the elongated hollow body, the at least two outlet connections disposed symmetrically about the elongated hollow body.
In the pressure reservoir of the invention, the outlet connections to the injection valves are disposed on the ends of the elongated hollow body that forms the pressure reservoir. In this manner, all of the outlet connections to the injection valves are subject to the same conditions with regard to possible pressure fluctuations in the pressure reservoir, and different outflow volumes are thus avoided. Moreover, by disposing the outlet connections in the region of the end portions of the pressure reservoir, a reduction in material costs can be achieved, since increased material loads occur not in the region of the circumferential wall of the hollow body but rather only in the region of outlet connections.
In accordance with an added feature of the invention, each of the at least two outlet connections have an axis and the elongated hollow body has an axis, the axis through each of the at least two outlet connections is inclined relative to the axis of the elongated hollow body.
In accordance with an additional feature of the invention, each of the at least two outlet connections have an axis and the elongated hollow body has an axis, the axis through each of the at least two outlet connections is laterally offset relative to the axis of the elongated hollow body.
In accordance with another feature of the invention, the at least one end piece has a tapered shape with a jacket face, and the at least two outlet connections are embodied on the jacket face.
In accordance with a further added feature of the invention, the at least one end piece includes a first end piece and a second end piece disposed respectively on the ends of the elongated hollow body, the first end piece and the second end piece each have at least one of the at least two outlet connections disposed thereon, and the at least two outlet connections disposed on the first end piece and the second end piece are recessed in mirror symmetry to one another.
In accordance with a further additional feature of the invention, there is a pressure sensor, and the elongated hollow body has a middle part and the pressure sensor and the inlet connection are embodied on the middle part.
In accordance with yet another feature of the invention, the injection valves have lines each with a diameter to be connected to the at least two outlet connections, and the at least two outlet connections each have a diameter larger than the diameter of the lines.
In accordance with yet another added feature of the invention, one of the ends of the elongated hollow body has an inside cone and the at least one end piece has an outside cone, a sealing point is created between the inside cone and the outside cone if the outside cone of the at least one end piece is screwed into the inside cone of the elongated hollow body.
In accordance with yet another additional features of the invention, the one end of the elongated hollow body and the at least one end piece each have male threads embodied in a same direction each with a thread pitch, and including a nut receiving the male threads for bracing the elongated hollow body against the at least one end piece, and the thread pitch of the at least one end piece is greater than the thread pitch of the one end of the elongated hollow body.
In accordance with a concomitant feature of the invention, there is a sealing element having two outside cones, one of the ends of the elongated hollow body and the at least one end piece each have an inside cone for receiving one of the two outside cones, the sealing element disposed between the one of the ends of the elongated hollow body and the at least one end piece forming sealing points between each of
Birkner Christian
Klesse Christoph
Kruger Hinrich
Rübling Klaus
Werner Martin
Greenberg Laurence A.
Lerner Herbert L.
Miller Carl S.
Siemens Aktiengesellschaft
Stemer Werner H.
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