JP2000205081A - Accumulated fuel injection system for diesel internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection characteristic having good responsiveness, improve an output of a diesel engine, improve fuel consumption, and reduce harmful component of exhaust gas by arranging an accumulating chamber on a downstream side from a common rail for accumulating pressure of fuel supplied to a nozzle holder for fuel injection arranged per cylinder. SOLUTION: High pressure fuel is supplied from a high pressure supplying pump 3 to a common rail 1 for accumulating pressure of fuel supplied to a nozzle holder 2 for fuel injection arranged per cylinder of a diesel internal combustion engine. In this case, an auxiliary accumulator 6-1 is arranged between a fuel distribution pipe 4 arranged downstream of the common rail 1 and the nozzle holder 2. The auxiliary accumulator 6-1 is formed so as to have an auxiliary accumulating chamber having a capacity of 3 to 20 times of the maximum injection rate of one time in the inside of the auxiliary accumulator 6-1. It is thus possible to improve fuel injection responsiveness without lengthening the common rail 1 and the nozzle holder 2 and enlarging an inner diameter, it is also possible to provide a correct injection characteristic so as to improve fuel consumption and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an accumulator type fuel injection system used for a diesel engine.

[0002]

2. Description of the Related Art A pressure accumulating fuel injection system for a diesel engine is an electromagnetically controlled fuel injection system in which high pressure fuel is accumulated in a common rail by a high pressure supply pump and high pressure fuel accumulated in the common rail is injected for each cylinder. The configuration includes a fuel injection nozzle holder provided for each cylinder of a diesel internal combustion engine, a common rail for accumulating the pressure of fuel supplied to the nozzle holder, a high pressure supply pump for supplying high pressure fuel to the common rail, and the common rail. The fuel supply pipe includes a fuel distribution pipe that communicates with the nozzle holder, and a fuel supply pipe that communicates with the common rail and the high-pressure supply pump.

[0003]

In the above-mentioned pressure-accumulation type fuel injection system, in order to obtain injection characteristics with good responsiveness, it is necessary to increase the pressure accumulation capacity of the fuel accumulated in the common rail or to increase the fuel accumulation pressure. Needs to be further enhanced. First, in order to secure the internal pressure accumulation volume in the common rail, the inner diameter of the common rail must be increased or the length of the common rail must be increased. But,
If the inner diameter of the common rail is increased, the thickness of the common rail must be increased to make it thicker and thicker, which inevitably increases the size of the common rail, including the bracket. If the inner diameter is further increased, the rigidity of the inner peripheral surface is reduced and the defect sensitivity of the inner peripheral surface is increased. Therefore, the number of defects is reduced as much as possible (preferably 10 μm or less). )Must. On the other hand, if the length of the common rail is increased, the common rail is designed to be longer than necessary, and unnecessary bending is performed on the fuel distribution pipe between the common rail and the nozzle holder to secure the substantial length. The need arises,
This also goes against the demands for weight reduction and miniaturization. Furthermore, in order to further increase the pressure of the fuel stored in the common rail or the like, the thickness must be further increased in order to maintain the pressure resistance, and the above-described defect on the inner peripheral surface must be reduced as much as possible. In addition, increasing the wall thickness not only increases the weight but also increases the risk of rupture due to internal pressure fatigue. In order to reduce the defect of the inner peripheral surface to preferably 10 μm or less, an expensive process is required, and the manufacturing cost is high. Therefore, none of the measures described above for obtaining the injection characteristics with good responsiveness is not preferable.

The present invention has been made to solve such problems of the prior art. By providing a sub-accumulation chamber in a pressure-accumulation type fuel injection system, an injection characteristic with good responsiveness can be obtained and a diesel engine can be obtained. It is an object of the present invention to propose a pressure-accumulation type fuel injection system for a diesel internal combustion engine, which can improve the output and fuel efficiency of the engine and reduce harmful components of exhaust gas.

[0005]

An accumulator type fuel injection system according to the present invention comprises a fuel injection nozzle holder provided for each cylinder of a diesel internal combustion engine, a common rail for accumulating the pressure of fuel supplied to the nozzle holder, A high-pressure supply pump for supplying high-pressure fuel to the common rail, a fuel distribution pipe for communicating the common rail with the nozzle holder, and a pressure accumulation for a diesel internal combustion engine including a fuel supply pipe for communicating the common rail and the high-pressure supply pump. In the fuel injection system, the first embodiment is characterized in that a sub-accumulation chamber is provided downstream of the common rail, and the second embodiment is characterized in that a fuel distribution pipe downstream of the common rail is connected to the nozzle holder. A third embodiment is characterized in that a sub-accumulation chamber is provided between the nozzle holder and the nozzle holder itself. In that a sub accumulation chamber characterized,
The fourth embodiment is characterized in that the volume of the sub-accumulation chamber is set to be 3 to 20 times the maximum injection amount at one time.

That is, the present invention provides a sub-accumulation chamber downstream of the common rail to secure the internal volumes of the common rail and the nozzle holder as means for obtaining injection characteristics with good responsiveness in the pressure accumulation type fuel injection system of the diesel internal combustion engine. In this way, the internal volume of the common rail and the nozzle holder can be secured by twisting such means, so that the fuel injection responsiveness (vehicle CPU) can be increased without increasing the length of the common rail and the nozzle holder or increasing the inner diameter. This makes it possible to further improve the response and to achieve accurate injection characteristics.

When the sub-accumulation chamber is provided between the fuel distribution pipe downstream of the common rail and the nozzle holder as a means for installing the sub-accumulation chamber, a dedicated sub-accumulator is separately manufactured and the fuel accumulation section is separately provided. This sub-accumulator may be connected between the end of the pipe and the fuel inlet of the nozzle holder. Therefore, in this case, the high-pressure fuel supplied from the common rail main pipe through the fuel distribution pipe is introduced into the fuel inlet of the nozzle holder through the sub-accumulator. When the sub-accumulation chamber is provided in the nozzle holder itself, a method of forming the sub-accumulation chamber at the fuel inlet of the nozzle holder can be used. In this case, the high-pressure fuel supplied from the common rail main pipe via the fuel distribution pipe is introduced into the nozzle holder through the sub-accumulation chamber provided at the fuel inlet of the nozzle holder.

Further, the volume of the sub-accumulation chamber or the sub-accumulator in the present invention is set to be 3 to 20 times the maximum injection amount per injection. If the volume is less than 3 times, the effect of improving the responsiveness is poor. On the other hand, when the ratio exceeds 20 times, the above-mentioned effect is large, but the size of the sub-accumulator or the sub-accumulator becomes large, making it difficult to secure the pressure resistance and increasing the manufacturing cost.

[0009]

FIG. 1 is a schematic view showing a pressure accumulating fuel injection system for a diesel internal combustion engine according to an embodiment of the present invention, and FIG. 2 is an enlarged view of a sub-accumulator in the fuel injection system shown in FIG. FIG. 3 is a schematic view showing a pressure-accumulating fuel injection system for a diesel internal combustion engine in another embodiment, and FIG. 4 is an enlarged view showing a main part of a nozzle holder in the fuel injection system shown in FIG. Yes,
1 is a common rail, 2 is a fuel injection nozzle holder, 3
Is a high-pressure supply pump, 4 is a fuel distribution pipe, 5 is a fuel supply pipe,
6-1 is a sub-accumulator, 6-2 is a sub-accumulator, 7-1 and 7-2
Is a fastening cap nut, and 8 is a washer.

That is, the present invention provides a fuel injection nozzle holder 2 provided for each cylinder of a diesel internal combustion engine, a common rail 1 for accumulating the pressure of fuel supplied to the nozzle holder, and a high pressure for supplying high pressure fuel to the common rail 1. A pressure-accumulating fuel for a diesel internal combustion engine comprising a supply pump 3, a fuel distribution pipe 4 for communicating the common rail 1 with the nozzle holder 2, and a fuel supply pipe 5 for communicating the common rail 1 with the high-pressure supply pump 3. In the injection system, the fuel injection system shown in FIG. 1 is configured by providing a sub-accumulator 6-1 between the fuel distribution pipe 4 downstream of the common rail 1 and the nozzle holder 2. As shown in the enlarged view of FIG. 2, the sub-accumulator 6-1 is connected to a boss 6-13 provided on the fuel distribution pipe 4 side of a container body having an accumulator chamber 6-12 therein, and to the accumulator chamber 6-12. A through hole 6 having a pressure receiving seat surface 6-14 communicating therewith and opening outward.
15, a boss 6-16 provided on the nozzle holder 2 side has a pressing seat surface 6-18 and a pressure accumulating chamber 6-1.
A through hole 6-19 leading to 2 is formed, and a threaded portion 6-17 is provided on the outer peripheral surface. A washer 8 is screwed into the threaded portion 6-17.

The connection with the fuel distribution pipe 4 is made by a pressing seat surface 4-4 formed by a connection head 4-1 provided at the end of the fuel distribution pipe 4.
2 is brought into contact with the pressure receiving seat surface 6-14 on the sub-accumulator 6-1 side, and the fastening cap nut 7-1 previously assembled on the fuel distribution pipe 4 side is screwed into the boss portion 6-13. By doing so, a connection is made by tightening with the pressing at the connection head 4-1.
On the other hand, the connection with the nozzle holder 2 is made by the boss 6-1 on this side.
6 through a washer 8 screwed to a screw portion 6-17 provided on the outer peripheral surface of the holder 6, so that the pressing seat surface 6-18 communicates with the fuel inlet portion 2-1 of the holder through the fuel flow path 2-2. Pressure receiving seat surface 2 which is provided at the opening of through hole 2-4 formed in
-3, and the fastening cap nut 7-2 previously assembled on the boss 6-16 side is screwed into the fuel inlet port 2-1 of the nozzle holder, whereby the pressing seat surface 6- 18
The connection is made by tightening in accordance with the pressing in the step.

[0012] In the pressure accumulation type fuel injection system having the above configuration,
The fuel pressurized to a high pressure by the high-pressure supply pump 3 and supplied to the common rail 1 flows into the nozzle holder 2 from the fuel inlet 2-1 through the sub-accumulator 6-1 via each fuel distribution pipe 4. Therefore, it is not necessary to increase the inner volume of the common rail by the operation of the sub-accumulator 6-1 provided in each fuel distribution pipe 4, and it is possible to obtain injection characteristics with good response without further increasing the fuel injection pressure. be able to.

Next, the fuel injection system shown in FIG. 3 is configured by providing a sub-accumulation chamber in the nozzle holder itself, and the nozzle holder 2 is enlarged as shown in FIG.
A sub-accumulation chamber 6-2 is provided in the middle of a through-hole 2-4 provided in the fuel inlet portion 2-1 so as to communicate with the fuel flow path 2-2 via the sub-accumulation chamber 6-2. The connection of the fuel distribution pipe 4 is performed by connecting the pressing seat surface 4-2 formed by the connection head 4-1 provided at the end of the fuel distribution pipe 4 to the fuel inlet section 2-1 of the nozzle holder 2. A pressure receiving seat surface 2-3 that opens outwardly provided at an opening of a through hole 2-4 that is formed so as to communicate with 2-2.
To the fuel inlet port 2 of the nozzle holder.
By screwing the connection head -1, the connection is made by tightening with the pressing at the connection head 4-1.

In the case of the pressure-accumulation fuel injection system having the above-described structure, the fuel pressurized to a high pressure by the high-pressure supply pump 3 and supplied to the common rail 1 flows into the nozzle holder 2 through each fuel distribution pipe 4. By the operation of the sub-accumulation chamber 6-2 provided in the fuel inlet section 2-1, the internal volume of the common rail does not need to be increased, and the fuel injection pressure does not increase as in the system of FIG. Good jet characteristics can be obtained.

The volumes of the sub-accumulator 6-1 and the sub-accumulation chamber 6-2 in the accumulator type fuel injection system shown in FIGS. 1 and 3 are each 3 to 20 times as large as the maximum injection amount for each injection. Needless to say,

[0016]

As described above, in the accumulator type fuel injection system for a diesel internal combustion engine according to the present invention, the sub-accumulator is provided downstream of the common rail to secure the accumulator volume at a position close to the injection nozzle. No need to lengthen the common rail or increase the inner diameter, and increase the fuel injection pressure to obtain highly responsive injection characteristics, improve diesel engine output, improve fuel efficiency, and reduce harmful components in exhaust gas. This has a great effect of reducing the amount of light.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a pressure accumulating fuel injection system for a diesel internal combustion engine according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing a sub-accumulator in the fuel injection system shown in FIG.

FIG. 3 is a schematic diagram showing a pressure accumulating fuel injection system for a diesel internal combustion engine according to another embodiment of the present invention.

FIG. 4 is an enlarged view showing a main part of the nozzle holder in the fuel injection system shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Common rail 2 Fuel injection nozzle holder 2-1 Fuel inlet 2-2 Fuel flow channel 2-3 Pressure receiving seat surface 2-4 Through hole 3 High pressure supply pump 4 Fuel distribution pipe 4-1 Connection head 4-2 Pressing Seat surface 5 Fuel supply pipe 6-1 Sub-accumulator 6-2, 6-12 Sub-accumulator chamber 6-13, 6-16 Boss 6-14 Pressure receiving seat surface 6-15, 6-19 Through hole 6-17 Screw Part 6-18 Press seat surface 7-1, 7-2 Tightening cap nut 8 Washer

Claims (4)

[Claims] 1. A fuel injection nozzle holder provided for each cylinder of a diesel internal combustion engine, a common rail for accumulating pressure of fuel supplied to the nozzle holder, a high pressure supply pump for supplying high pressure fuel to the common rail, and a common rail. In a pressure accumulating type fuel injection system for a diesel internal combustion engine including a fuel distribution pipe communicating with the nozzle holder, and a fuel supply pipe communicating the common rail and the high-pressure supply pump, a sub-accumulation chamber is provided downstream of the common rail. A pressure accumulating fuel injection system for a diesel internal combustion engine, comprising: 2. A fuel injection nozzle holder provided for each cylinder of a diesel internal combustion engine, a common rail for accumulating the pressure of fuel supplied to the nozzle holder, a high pressure supply pump for supplying high pressure fuel to the common rail, and a common rail. In a pressure-accumulating fuel injection system for a diesel internal combustion engine including a fuel distribution pipe communicating with the nozzle holder and a fuel supply pipe communicating the common rail and the high-pressure supply pump, a fuel distribution pipe downstream of the common rail is provided. An accumulator type fuel injection system for a diesel internal combustion engine, wherein a sub-accumulator is provided between the fuel injector and the nozzle holder. 3. A fuel injection nozzle holder provided for each cylinder of a diesel internal combustion engine, a common rail for accumulating the pressure of fuel supplied to the nozzle holder, a high pressure supply pump for supplying high pressure fuel to the common rail, and a common rail. In a pressure-accumulation type fuel injection system for a diesel internal combustion engine including a fuel distribution pipe communicating with the nozzle holder, and a fuel supply pipe communicating the common rail and the high-pressure supply pump, a sub-accumulation chamber is provided in the nozzle holder itself. A pressure accumulating fuel injection system for a diesel internal combustion engine, comprising: 4. The diesel internal combustion engine according to claim 1, wherein the volume of the sub-accumulation chamber is 3 to 20 times the maximum injection amount at one time. Accumulation type fuel injection system.