Internal-combustion engines – Charge forming device – With fuel pump
Reexamination Certificate
1998-08-25
2001-11-13
Miller, Carl S. (Department: 3747)
Internal-combustion engines
Charge forming device
With fuel pump
C123S456000
Reexamination Certificate
active
06314946
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a fuel injection in a Diesel engine and to a fuel injection system for a Diesel engine, for injecting a fuel into the combustion chamber of the engine by employing a common rail.
BACKGROUND ART
In the Diesel engine, there is adopted as one fuel injection system a common rail system which has an integral construction of an injection pump and a nozzle and which uses a fuel injection nozzle (or unit injector) mounted for each cylinder on a cylinder head so that a fuel under a relatively high pressure is accumulated in a common rail acting as a pressure chamber and is boosted to a higher level by a pressure intensifying piston constituting a fuel injection pump and injected by the fuel injection nozzle.
In this common rail system, as shown in
FIG. 3
, the fuel in a fuel tank
11
is boosted by a fuel feed pump
3
to a pressure level, which is controlled by a pressure control valve
10
controlled by a controller
13
, and is stored in a common rail
4
acting as an accumulator. The fuel in this common rail
4
is injected through fuel pipes
5
and solenoid valves
14
into combustion chambers
15
by fuel injection nozzles
6
. The quantities and timings of the fuel injections are adjusted by turning ON/OFF the solenoid valves
14
by the controller
13
which receives signals from a variety of sensors
12
.
In this case, all the fuel pipes
5
for connecting the discharge ports
7
of the common rail
4
and the fuel injection nozzles
6
have to be given equal lengths so as to prevent dispersion in the pressure responses among the fuel injection nozzles
6
, i.e., to prevent the fuel injection timings from going out order.
In the fuel injection system of the common rail system of the prior art, however, the fuel feed pump and the common rail
4
are arranged not with any overlap but planarly on the upper face of the cylinder body
2
, as seen from top plan views of an engine
1
shown in
FIGS. 4 and 5
.
Since the fuel pipes
5
connecting the common rail
4
and the fuel injection nozzles
6
have to be arranged to bypass the fuel feed pump
3
, therefore, they have long and different lengths.
In order to feed the fuel under a constant pressure to the fuel injection nozzles
6
, on the other hand, each fuel pipe
5
has to be extended to have the longest length so as to make the pressure losses and responses uniform. This necessity elongates the fuel pipes
5
as a whole to complicate the assembling and repairing works. Since the whole lengths of the fuel pipes
5
from the common rail
4
acting as a pressure source to the fuel injection nozzles
6
are increased, moreover, there arises a problem that the responsiveness to the injection pressure is accordingly degraded.
These fuel pipes
5
have to be made of thick and strong metal pipes sufficient for enduring high pressure and vibration so that they are arranged on the vibrating engine
1
to feed the fuel under the high pressure. If the fuel pipes
5
are elongated for that reason, there arises a problem that the fuel pipes
5
provides an unnegligible increase in their total weight.
For these reasons, the fuel pipes
5
between the common rail
4
and the fuel injection nozzles
6
to be used have to be as short as possible for lightening the engine.
In the method for mounting the common rail
4
and the fuel feed pump
3
, moreover, there are individually required the brackets for mounting the fuel feed pump
3
on a cylinder body
2
and the brackets for mounting the common rail
4
on the cylinder body
2
. This necessity also raises a problem that it causes an increase in the engine weight.
The invention has been conceived to solve the above-specified problems with the engine of the prior art, and has an object to provide a fuel injection system for a Diesel engine, which is enabled to have a small space, a reduced number of parts, a light weight and an excellent reparability by arranging such a common rail as eliminates the bracket structures for the common rail and the fuel feed pump and as makes the fuel pipes short as a whole.
DISCLOSURE OF INVENTION
In order to achieve the object, according to the invention, there is provided a fuel injection system for a Diesel engine, constructed such that a common rail is mounted on a cylinder body, and such that a fuel feed pump is mounted to overlie said common rail, so that a fuel to be pumped by said fuel feed pump is injected into the combustion chambers of cylinders after it was accumulated by the common rail.
Moreover, said common rail is arranged at the center in the longitudinal direction of said engine. Then, the longest distance between the individual discharge ports of the common rail and the fuel injection nozzles arranged at the combustion chambers of the individual cylinders can be reduced to shorten the fuel pipes conforming to that longest distance.
When said Diesel engine is a V-type engine, still moreover, the piping can be made symmetric not only in the longitudinal direction but also in the transverse direction so that the symmetric fuel pipes can be increased to reduce the number of parts.
REFERENCES:
patent: 2892453 (1959-06-01), Stoll
patent: 3026928 (1962-03-01), Phillips
patent: 3783842 (1974-01-01), Kuhn
patent: 4570602 (1986-02-01), Atkins
patent: 5022371 (1991-06-01), Daly
patent: 5398658 (1995-03-01), Mesimaki
patent: 5408971 (1995-04-01), Jeager
patent: 5411001 (1995-05-01), Werner
patent: 5482021 (1996-01-01), Roche
patent: 10-37756 (1998-02-01), None
Funakura Kazuki
Nakanishi Shinichi
Isuzu Motors Limited
Miller Carl S.
Staas & Halsey , LLP
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