Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2000-01-14
2002-06-04
Moulis, Thomas N. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S457000
Reexamination Certificate
active
06397819
ABSTRACT:
PRIOR ART
The invention is based on a fuel delivery system for supplying fuel for an internal combustion engine.
In the prior art there have been fuel delivery systems in which a first fuel pump supplies fuel from a fuel tank to a second fuel pump by way of a fuel connection. The second fuel pump in turn supplies the fuel to two fuel distribution strips. A number of fuel valves are connected to each of the fuel distribution strips. Usually, the number of fuel valves is equal to the number of cylinders of the engine. The fuel delivery system is constructed so that the fuel valves each inject the fuel directly into a respective combustion chamber of the engine. The operation of this fuel delivery system requires a high pressure at the inlet of the fuel valves and therefore in the fuel distribution strips.
In an internal combustion engine in which there are two rows of cylinders disposed in a V-shape in relation to one another, a fuel distribution strip is provided for each row of cylinders.
Because the fuel valves are connected directly to the fuel distribution strips, it is important that precisely the same pressure prevail in each of the two fuel distribution strips. It is necessary to have the capacity to very precisely and rapidly adapt this pressure to the respective operating condition of the engine. In previously known fuel delivery systems, these problems could not be satisfactorily solved and up to this point, the expense for solving these problems has been considerably high.
The pressure of the fuel in the fuel distribution strips can be controlled by means of pressure control valves. Up to now, the cost for controlling the pressure in the pressure distribution strips has been considerably high and/or quite imprecise and/or it has turned out that the location provided for the pressure control valve has a negative influence on the service life and/or the regulating quality of the pressure control valve. Previously, the prevailing opinion held that a considerably high cost had to be incurred in order to precisely regulate the pressure in the fuel distribution strips or if incurring this high cost was undesirable, a lower quality of pressure control, in particular divergent pressures in the fuel distribution strips, had to be accepted.
In some known fuel delivery systems, an extremely long high-pressure line had to be installed in order to be able to control the pressure in the two fuel distribution strips to a fairly precise degree. This increased the manufacturing cost enormously.
Because a slight relative movement between the two fuel distribution strips cannot be completely prevented, there are fuel delivery systems in which the connection between the two fuel distribution strips takes place by way of high-pressure lines comprised of a flexible, preferably cloth-reinforced, rubber elastic material. Because of the high-pressure and the aggressiveness of the fuel in the high-pressure lines, however, there have not yet been reasonably priced, sufficiently elastic high-pressure lines with which a sufficient flexibility between the two fuel distribution strips could be achieved, which is why a direct high-pressure line as a direct connection between the two fuel distribution strips has not been completely satisfactory in practical application for reasons of tightness, service life, function, and cost.
ADVANTAGES OF THE INVENTION
The fuel delivery system according to the invention, has an advantage that the pressure in the fuel distribution strips can be very precisely adjusted, particularly with a high regulating quality. It achieves the fact that the pressure can be very rapidly and precisely adapted with changing operating conditions of the internal combustion engine. The manufacturing cost as well as the cost for subsequent operation and later maintenance work is advantageously particularly low because the one pressure control valve can also be used to regulate the pressure of the fuel in the second fuel distribution strip and, if necessary, in other fuel distribution strips. Advantageously, only a very few hydraulic and electric lines have to be laid.
Since the pressure control valve is provided in the vicinity of the first fuel distribution strip, and is therefore sufficiently removed from the second fuel pump, the advantage is attained that inevitable pressure pulsations caused by the second fuel pump cannot lead to an impairment of the regulation quality of the pressure control valve and cannot lead to a shortening of the service life or to an impairment of the regulation quality of the pressure control valve over the course of time. Particularly since the pressure control valve is provided immediately in the vicinity of the fuel distribution strip, pressure pulsations are advantageously also smoothed by means of the volume in the fuel distribution strip, which advantageously has a favorable influence on the pressure adjustment quality of the pressure control valve.
In particular, because the pressure control valve in the fuel distribution strip is disposed in the vicinity of the inlet connection of the fuel distribution strip, this results—in a particularly simple manner—in the fact that the pressure in the second fuel distribution strip can also be controlled in a sufficiently precise manner with only the one pressure control valve.
Advantageously, an immediate, direct, short connection between the two fuel distribution strips can be eliminated which would be problematic because of the high-pressures, sharply fluctuating temperatures, and dynamic stresses due to pressure pulsations and relative oscillations between the two fuel distribution strips.
Advantageous improvements and updates of the fuel delivery system are possible by means of the measures taken in the disclosure.
If the fuel line receiving the fuel flowing out from the pressure control valve is laid so that it feeds into the fuel connection, preferably directly at the low-pressure side of the second fuel pump, the advantage is attained that on the whole, very little line length has to be laid.
Providing the inlet connections of the fuel distribution strips at their ends can result in the advantageous fact that only one very short high-pressure line has to be laid between the second fuel pump and the fuel distribution strips.
If the high-pressure line leading from the second fuel pump to the fuel distribution strips is split into two high-pressure line branches, wherein the one branch leads to the one fuel distribution strip and the other branch leads to the other fuel distribution strip, then both fuel distribution strips can be connected in a simple manner wherein the advantage is attained that no direct connection has to be produced between the two fuel distribution strips, which would be problematic because a certain relative mobility between the two fuel distribution strips must be assured due to manufacture tolerances, temperature fluctuations, and oscillations. Another particular advantage is that a tube material can be used for the high-pressure line which is relatively rigid and inexpensive to produce, and despite this fact, the relative mobility between the two fuel distribution strips remains assured. In particular, a flexible hose comprised of cloth and/or rubber and/or plastic does not have to be used.
If both high-pressure line branches are the same length, then the advantage of a particularly favorable adjustability and regulation quality of the pressure in the two fuel distribution strips is achieved, even with the use of only the one pressure control valve in the first fuel distribution strip.
If the high-pressure line splits into the two high-pressure line branches relatively soon after the second fuel pump or even inside the second fuel pump, then the advantage of a particularly sufficient relative mobility between two fuel distribution strips is attained, even with the use of a particularly rigid tube material for the high-pressure line.
REFERENCES:
patent: 5207203 (1993-05-01), Wagner et al.
patent: 5676114 (1997-10-01), Tarr et al.
patent: 6000380 (1999-12-01), Weisbarth
Baessler Albrecht
Buchwald Hermann
Grommes Erwin
Rembold Helmut
Greigg Ronald E.
Moulis Thomas N.
Robert & Bosch GmbH
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