JPH11280596A - Fuel piping device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain proper fuel injection from each unit injector. SOLUTION: In a fuel piping device of an internal combustion engine which is provided with a unit injector 2 pressurizing and injecting fuel for every cylinder and is provided with a fuel introduction path 7 leading fuel from a fuel pump 4 to the arraying direction of a cylinder through the inside of a cylinder head 1, a distribution path 8 distributing fuel of the fuel introduction path 7 to each unit injector 2 and a fuel return path 9 returning surplus fuel from each unit injector 2, a bypass path 11 bypassing a path to the lowermost stream unit injector 2 of the cylinder arraying direction of the fuel introduction path 7 is formed and this bypass path 11 is communicated with the fuel return path 9 via a prescribed restriction 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel piping system for an internal combustion engine having a unit injector.

[0002]

2. Description of the Related Art There is a diesel engine provided with a unit injector for injecting fuel by pressurizing each cylinder to a high pressure.

[0003] Such a unit injector is driven by a cam or the like provided on a cylinder head.
Therefore, fuel to the unit injector is supplied through a fuel passage formed inside the cylinder head (see Japanese Patent Application Laid-Open No. 9-264227).

[0004]

However, when the fuel is supplied by forming the fuel passage inside the cylinder head as described above, it is difficult to supply the fuel to each unit injector at the same supply pressure. Hateful.

In an in-line multi-cylinder engine or the like, fuel is distributed to the unit injectors in the order of arrangement of the cylinders from a fuel passage formed in the arrangement direction of the cylinders. Since the passage diameter cannot be made large, the fuel supply pressure may decrease on the most downstream side of the fuel passage.

Therefore, even when fuel of a predetermined pressure is supplied to the fuel passage from the fuel pump, the required injection cannot be performed due to a decrease in injection pressure in the last row of unit injectors.

An object of the present invention is to solve such a problem.

[0008]

According to a first aspect of the present invention, there is provided a fuel injector having a unit injector for pressurizing and injecting fuel for each cylinder, and for guiding fuel from a fuel pump through the inside of a cylinder head in the direction in which the cylinders are arranged. In a fuel piping device for an internal combustion engine, comprising a passage, a distribution passage that distributes fuel in a fuel introduction passage to each unit injector, and a fuel return passage that returns surplus fuel from each unit injector.
A bypass passage is formed to bypass a passage of the fuel introduction passage to the most downstream unit injector in the cylinder arrangement direction, and the bypass passage communicates with a fuel return passage via a predetermined throttle.

In a second aspect based on the first aspect, the communication portion is located upstream of a regulator valve provided in a fuel return passage.

[0010]

According to the first and second aspects of the present invention, it is possible to prevent the flow of fuel from occurring at the most downstream portion of the fuel introduction passage and to reduce the fuel pressure at the most downstream portion. Fuel is also supplied to the unit injector on the side at a predetermined supply pressure, so that appropriate fuel injection can be performed from each unit injector at a predetermined injection pressure.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a fuel system diagram. 1 is a cylinder head of a diesel engine (in-line multi-cylinder engine), 2 is a unit injector arranged for each cylinder in a cylinder head 1, and pressurizes fuel to a high pressure and injects the fuel. Reference numeral 3 denotes a fuel tank, 4 denotes a fuel pump, and 5 denotes a fuel filter.

Each unit injector 2 is driven by a cam (not shown) on the cylinder head 1 or the like.

The fuel in the fuel tank 3 sucked up by the fuel pump 4 passes through the fuel filter 5 and passes through the fuel pipe 6
Through the fuel introduction passage 7 formed inside the cylinder head 1 and supplied from the fuel introduction passage 7 to each unit injector 2 via each distribution passage 8 also formed inside the cylinder head 1.

The fuel introduction passage 7 is formed from one end of the cylinder head 1 along the direction in which the cylinders are arranged.
Are branched from the fuel introduction passage 7 in the arrangement order of the cylinders, and communicate with the fuel inlets (not shown) of the unit injectors 2.

A fuel return passage 9 for returning excess fuel from each unit injector 2 passes through the inside of the cylinder head 1 and is formed in the direction in which the unit injectors 2 are arranged.

The fuel return passage 9 communicates with a fuel drain port (not shown) of each unit injector 2, and a regulator valve 10 that opens at a predetermined pressure is interposed at an outlet of the cylinder head 1 in the passage 9. The downstream side of the regulator valve 10 is connected to the suction side of the fuel pump 4.

The diameters of the fuel introduction passage 7, the branch passage 8, and the fuel return passage 9 may be substantially the same.

The most downstream portion of the fuel introduction passage 7 in the cylinder arrangement direction, that is, the fuel introduction passage 7 at the branching portion of the distribution passage 8 to the last row of unit injectors 2 is extended. Passage) 11 is a throttle 1 having a predetermined diameter.
2, it is communicated with the fuel return passage 9. in this case,
Immediately upstream of the regulator valve 10, the fuel return passage 9
Is communicated to.

FIGS. 2 to 4 show examples in which the fuel introduction passage 7, the branch passage 8, and the fuel return passage 9 are formed in the cylinder head 1. FIG. FIG. 2 is a top view of the cylinder head 1, FIG. 3 is a cross-sectional view along the line AA, FIG. 4 is a cross-sectional view along the line BB, and the fuel introduction passage 7 is an end portion on the intake port 20 side. The distribution passage 8 is formed along the direction in which the cylinders are arranged.
As described above, the fuel introduction passage 7 branches at a right angle and is formed toward the fuel inlet of the unit injector 2 obliquely upward. The fuel return passage 9 is formed through a groove 22 of a mounting hole 21 connected to the fuel drain port of the unit injector 2, and a mounting hole 23 of the regulator valve 10 is formed at an outlet of the cylinder head 1 in the passage 9. You. The extending portion 11 of the fuel introduction passage 7 communicates with the fuel return passage 9 as shown in FIG. 4, and a throttle 12 provided in the middle thereof is embedded in an insertion hole 24 formed at an end of the cylinder head 1. .

The fuel in the fuel tank 3 is sucked up by the fuel pump 4 through the case of the control unit 13 of the engine, and the control unit 1
3 is performed. Further, the fuel filter 5 is provided with a regulator valve 15 that opens the release pipe 14 when the internal pressure increases, and releases the fuel in the fuel filter 5 to the fuel tank 3.

With such a configuration, the fuel sent from the fuel pump 4 to the fuel introduction passage 7 inside the cylinder head 1 via the fuel filter 5 and the fuel pipe 6 is also supplied from the fuel introduction passage 7 to the cylinder head 1. It is evenly distributed and supplied to each unit injector 2 via each distribution passage 8 formed therein.

That is, since the most downstream portion of the fuel introduction passage 7 is communicated with the fuel return passage 9 through the throttle 12 having a predetermined diameter, the unit injector 2 on the front row drives the fuel return passage 9.
Even when fuel is supplied from the distribution passage 8 on the front row to the corresponding unit injector 2, a flow to the fuel return passage 9 through the throttle 12 is generated in the fuel introduction passage 7 on the most downstream side. Therefore, when the last row unit injector 2 is driven, the fuel introduction passage is not communicated with the fuel return passage through the throttle as in the conventional example, and the fuel introduction passage at the branch portion of the distribution passage on the last row side is not connected. The fuel pressure in the fuel introduction passage 7 is suppressed from lowering as compared with the case where the flow of fuel is stopped, so that the fuel supply passage 7 can be maintained at a predetermined supply pressure without increasing the diameter of the passage such as the fuel introduction passage 7. The fuel is supplied to the unit injector 2.

Accordingly, fuel can be properly injected from each unit injector 2 at a predetermined injection pressure.

Since the fuel introduction passage 7 communicates with the fuel return passage 9 upstream of the regulator valve 10 via the throttle 12, the fuel pressure in the fuel introduction passage 7 can be set by the throttle 12 and the regulator valve 10.

[Brief description of the drawings]

FIG. 1 is a fuel system diagram showing an embodiment.

FIG. 2 is a top view of the cylinder head.

FIG. 3 is a sectional view taken along line AA of FIG. 2;

FIG. 4 is a sectional view taken along line BB of FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder head 2 Unit injector 3 Fuel tank 4 Fuel pump 5 Fuel filter 6 Fuel pipe 7 Fuel introduction passage 8 Distribution passage 9 Fuel return passage 10 Regulator valve 11 Extension part (bypass passage) 12 Restrictor 23 Mounting hole 24 Insertion hole

Claims (2)

[Claims] 1. A fuel injector, comprising: a unit injector for pressurizing and injecting fuel for each cylinder; a fuel introduction passage for guiding fuel from a fuel pump through an inside of a cylinder head in a cylinder arrangement direction; In a fuel piping system for an internal combustion engine having a distribution passage for distributing to unit injectors and a fuel return passage for returning excess fuel from each unit injector, a bypass for a passage to the most downstream unit injector in the cylinder arrangement direction of the fuel introduction passage is provided. A fuel pipe device for an internal combustion engine, wherein a bypass passage is formed, and the bypass passage communicates with a fuel return passage through a predetermined throttle. 2. The fuel piping device for an internal combustion engine according to claim 1, wherein the communication portion is located upstream of a regulator valve provided in a fuel return passage.