Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2000-03-29
2002-01-15
Moulis, Thomas N. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S468000, C123S469000
Reexamination Certificate
active
06338334
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a fuel piping structure for a diesel engine.
BACKGROUND ART
The following structures are each known as a fuel circuit for supplying fuel to a fuel injection nozzle located in each cylinder of a diesel engine and for returning excess fuel into a fuel tank.
(1) An Engine of a Separate Cylinder Head Structure
A fuel manifold is attached on side faces of separated cylinder heads, and fuel is supplied from the fuel manifold to each fuel injection nozzle while excess fuel is returned.
FIG. 7
schematically shows an example of a fuel circuit in a six-cylinder in-line diesel engine of a separate cylinder head structure, in which fuel injection nozzles
22
are respectively placed in six cylinder heads
21
each independently provided for each cylinder. A front side fuel manifold
23
is fastened to side faces of No. 1 to No. 3 cylinder heads
21
, and a rear side fuel manifold
24
is fastened to side faces of No. 4 to No. 6 cylinder heads
21
, out of the aforesaid cylinder heads
21
. In
FIG. 7
, the front side fuel manifold
23
and the rear side fuel manifold
24
are shown by the diagonally shaded areas.
A fuel supply bore
23
a
, fuel supply bores
23
b
branching from the fuel supply bore
23
a
toward the respective injection nozzles
22
, a fuel return bore
23
c
, and fuel return bores
23
d
branching form the fuel return bore
23
c
toward the respective injection nozzles
22
are provided inside the front side fuel manifold
23
. The fuel supply bore
23
b
and the fuel return bore
23
d
are respectively connected to a fuel supply bore
21
a
and a fuel return bore
21
b
provided in each of the cylinder head
21
. On the contact faces of each cylinder head
21
and the front side fuel manifold
23
, O-rings not shown are respectively attached between the contact portions of the fuel supply bore
23
b
and the fuel supply bore
21
a
, and between the contact portions of the fuel return bore
21
b
and the fuel return bore
23
d
. Further, the relationships between the fuel circuit provided inside the rear side fuel manifold
24
and the cylinder heads
21
are identical to the case of the front side fuel manifold
23
, thus omitting the explanation thereof.
An intake manifold
25
is also fastened to the side face of each cylinder head
21
. As a result, a fuel supply line
29
, which runs from a fuel tank
26
by way of a fuel filter
27
and a fuel pump
28
, branches in the longitudinal direction of the paper face of
FIG. 7
, and goes around a front end and a rear end of the intake manifold
25
to be connected to a front end of the front side fuel manifold
23
and a rear end of the rear side fuel manifold
24
respectively. Fuel return lines, which are connected to the front end of the front side fuel manifold
23
and the rear end of the rear side fuel manifold
24
respectively, are combined into one fuel return line
30
, and thereafter it is connected to the fuel tank
26
via a fuel cooler
31
.
(2) An Engine with an Integral-type of Cylinder Head Structure
In this case, a fuel manifold as in the above item (
1
) is adopted, or common-supply-and-return-fuel-lines which run through each cylinder are provided inside a cylinder head, thereby directly connecting external lines to the fuel manifold or the common fuel lines.
(3) In a fluid circuit for an engine cylinder head, which is proposed by the present inventor and disclosed in Japanese Patent Application Laid-open No. 6-207565, an engine with a separate cylinder head structure is used. However, the fuel manifold is not used, and a fuel circuit is formed by connecting fuel supply lines each provided inside a rocker housing of each cylinder, and fuel return lines, with pipes respectively.
However, the above prior arts have the following disadvantages.
(1) The Disadvantage Common to the Respective Kinds of Engine Explained in the Prior Art.
Since the fuel circuit is not cooled by the fluid (for example, air, water, and the like) inside the engine, the temperature of fuel (specifically, excess fuel) cannot be reduced. Accordingly, in order to cool the fuel, a fuel cooler of large capacity has to be additionally placed.
(2) The Disadvantage Regarding the Fuel Manifold
A fuel manifold is generally manufactured by extrusion molding of aluminum material (plastic processing), and an O-ring is incorporated in order to prevent fuel leak at the contact portions of the fuel manifold and the cylinder head. However, since the fuel manifold is long, it is difficult to secure flatness on the surface scaled by the O-ring, and the O-ring is easy to come off during assembly. Consequently, there is the disadvantage of fuel seal being less reliable.
(3) The Disadvantage Regarding the Common Fuel Line Provided Inside the Cylinder Head
This is used in an engine with an integral-type of cylinder head structure, but if this is used in a large-sized engine with a separate cylinder head structure which is generally adopted, it is extremely difficult to provide a common fuel line, which runs through each cylinder, inside the cylinder head.
(4) The Disadvantage Regarding Japanese Patent Application Laid-open No. 6-207565
The art disclosed in Japanese Patent Application Laid-open No. 6-207565 is one of the means for overcoming the above disadvantages. However, since a fuel cooling function is not included in the art, it is necessary to additionally provide a fuel cooler of large capacity in order to cool fuel.
SUMMARY OF THE INVENTION
In view of the above disadvantage of the above prior art, the present invention is made, and its object is to provide a fuel piping structure for a diesel engine capable of cooling fuel (including excess fuel) flowing through a fuel circuit of a fuel injection system, and capable of making the fuel circuit compact in size.
A fuel piping structure for a diesel engine according to the present invention is a fuel piping structure for a diesel engine in which a fuel circuit is provided between a fuel lank and fuel injection nozzles each for each cylinder head, and is characterized in that
a part of the fuel circuit is formed inside an intake manifold.
According to the above configuration, since a part of the fuel circuit is formed inside the intake manifold, that is, the intake manifold is used for a dual purpose, the fuel manifold conventionally used becomes unnecessary. As a result, a component configuration and piping structure on the side of the cylinder head, to which the intake manifold is mounted, are simplified, and thus the engine can be made compact in size.
Further, in the fuel piping, structure, the part of the fuel circuit may be a part of a fuel return circuit running from the fuel injection nozzles to the fuel tank.
According to the above structure, since a part of the fuel return circuit running from the fuel injection nozzles to the fuel tank is formed inside the intake manifold, excess fuel is cooled by air flowing through the intake manifold. The cooling effect becomes especially large when an engine with a system in which air compressed by a supercharger is cooled by means of an after-cooler. Since excess amount of fuel (specifically, excess fuel) which is pressurized to he heated to a high temperature is efficiently cooled inside the intake manifold when returning to the tank, the fuel cooler, which is conventionally indispensable, can be withdrawn from service or downsized. Further, the temperature of the fuel tank decreases with falling temperature of the excess fuel, thus improving, safety.
Furthermore, in the fuel piping structure for the diesel engine, the part of the fuel circuit may be a part of a fuel supply circuit running from the fuel tank to the fuel injection nozzles.
According to the above configuration, since a part of the fuel supply circuit is formed inside the intake manifold, the fuel manifold conventionally used becomes unnecessary. As a result, the component configuration on the side of the cylinder head, to which the intake manifold is mounted, can be simplified. Further, since the fuel supply piping structure is simpli
Komatsu Ltd.
Moulis Thomas N.
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