JPS61167157A - Distribution type fuel injection pump of diesel engine - Google Patents

Abstract

PURPOSE:To maintain the stable fuel injection performance by installing a unidirectional valve which permits only the flow in the direction from a compression chamber to a cut-off port, into a communication passage formed along the shaft center of a plunger. CONSTITUTION:A fuel injection pump is equipped with a plunger 7 which revolves integrally with a drive shaft and a cam disc. Along the shaft center of the plunger 7, a communication passage 11 for the communication between a compression chamber 15, cut-off port 12, and a distribution port 13 is formed. A unidirectional valve 31 having a prescribed valve opening pressure for permitting only the flow in the direction from the compression chamber 15 to a cut-off port 12 is installed into the communication passage 11. Thus, the stable fuel injection performance can be maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a distributed fuel injection pump for a diesel engine, and more particularly to an improvement in a distributed fuel injection bonder suitable for injecting air-mixed fuel.

2. Description of the Related Art There are various types of fuel injection pumps for diesel engines, one of which is known as a so-called VE type distribution fuel injection pump as shown in FIG. In detail,
1 is a pump nozzle, 2 is a drive shaft driven by the engine output, 3 is a feed pump driven by this drive shaft 2 and pumps fuel into the pump chamber 4, and 5 is a regulating valve. Note that, for convenience of explanation, the feed pump 6' is also shown with its direction changed by 90 degrees. 6 is a cam disk that rotates integrally with the drive shaft 2 in the pump chamber 4; 7 is a plunger fixed to the cam disk 6;
9 is a plunger barrel in which the plunger 7 is slidably and closely fitted; 9 is a roller holder equipped with rows 210 that slide in contact with the cam surface of the cam disc 6; For example, in a four-cylinder engine, four cam protrusions are formed every 90 degrees, and roller 1
0, the plunger 7 reciprocates in the axial direction every 2090 degrees of the drive shaft. In this granger 7, a communication passage 11, a cut-off port 12, and a distribution boat 16 are formed in communication with each other along the shaft center, and four suction grooves 14, which are equal to the number of cylinders, are formed at the tip. On the other hand, the plunger barrel 8 has a suction boat 16 that supplies fuel to the compression chamber 15 at the tip of the plunger 7 through the suction groove 14, and a cylinder that is opened so as to fit into the distribution boat 13. Four discharge boats 17 are formed. That is,
As the plunger 7 moves forward and backward, the fuel in the pump chamber 4 is sent to the compression chamber 15, where it is compressed, and is then pressure-fed from the distribution boat 13 to the delivery valve 18 via the discharge boat 17. Then, this operation is performed at 90 as described above.
This is done every 30 degrees, and fuel is distributed sequentially to the four cylinders.

In addition, 19 is a control sleeve for controlling the opening timing of the cut-off port 12 to variably adjust the injection amount, 20U is a governor mechanism that controls the position of this control sleeve 19, and 21 is a governor mechanism that controls the rotation of the roller holder 9. This is a timer mechanism (in the figure, the direction is changed by 90 degrees) that advances the injection timing.

(For example, refer to "Diesel Engine Technical Manual" published by Nippon Jidosha ■, August 1981.) In recent years, in order to reduce exhaust black smoke and improve fuel efficiency in diesel engines, air is added to the injected fuel in advance. It has been proposed to use an air-mixed fuel that is completely mixed. This involves blowing pressurized air from a compressor into the fuel path from the fuel tank to the fuel injection pump to create a state in which the fuel contains fine air bubbles, which are then injected through the fuel injection nozzle by the fuel injection pump. The air bubbles in the fuel are pressurized by a fuel injection pump and are completely dissolved in the fuel before being sent to the injection nozzle. The moment it comes out, it rapidly expands and contributes to improving combustion (Japan Society of Mechanical Engineers Lecture Proceedings Black 837-2
(See October 1, 1983 lecture).

Problems to be Solved by the Invention However, in the above-mentioned conventional distribution type fuel injection pump,
Since the volumes of the communication passage 11 of the plunger 7, the cut-off port 12, and the passage from the discharge boat 17 to the delivery valve 18 all become the trap volume of the high-pressure system, the delivery pulp is placed directly at the fuel outlet of the compression chamber. The trap volume is very large compared to the standard fuel injection bong. Therefore, when using the above-mentioned air-mixed fuel containing fine air bubbles, the volume of air bubbles that separate from the liquid or expand within the trap volume during the fuel intake stroke becomes considerably large, and the fuel When the air mixing rate inside the tank was increased, fuel injection became difficult or the desired amount of fuel 1 could not be secured.

Even if the configuration is such that normal liquid fuel is injected as is, if air gets mixed into the fuel for some reason,
Similar problems are likely to occur.

Next Means for Solving the Problems In order to solve all of the above problems, the present invention provides a connection formed along the axial center of the plunger so as to communicate the compression chamber, the cut-off port, and the distribution boat. A one-way valve with a predetermined opening pressure that only allows flow from the compression chamber toward the cut-off port is interposed in the passage, thereby reducing the effective trap volume in which air bubbles are generated. be.

The one-way valve is provided between the compression chamber and the distribution boat, or between the distribution boat and the capt-off boat, or both.

Effect: The one-way valve described above divides the trap volume from the compression chamber into two or three parts, and the effect of the pressure drop during the plunger's suction stroke or when the cut-off port is opened is applied to a part of the trap volume. It will only reach you. Therefore, the air bubbles generated and expanded due to the pressure drop are limited to a limited portion of the total trap volume, and when the plunger moves to the compression stroke, the air bubbles present in the entire trap volume are greatly reduced. It is possible.

Embodiment FIG. 1 is a sectional view of the essential parts of a fuel injection pump showing a first embodiment of the present invention, and the same parts as those of the conventional pump described above are given the same reference numerals. In this first embodiment, the compression chamber 15 of the communication passage 11 is formed along the axial center of the plunger 7.
At the end of the side, as a one-way valve, a spherical valve body 31a,
/(A check valve 31 consisting of a Tsukua knob spring 61b and a spring seat 31C is provided.The check valve 61 allows fuel to flow from the compression chamber 15 into the communication path 11, The valve opening pressure is set to be relatively small, and the valve opening pressure is set to be relatively small.

In addition, when using air-mixed fuel, the pressure in the pump chamber 4 (see Figure 4) needs to be maintained at a higher value than when injecting normal liquid fuel, for example, about 10 kg/(,,!). .

This first embodiment mainly prevents the generation of air bubbles (separation from the fuel liquid and expansion of undissolved gas) within the trap volume during the suction stroke of the plunger 7 to a part of the trap volume, that is, the compression chamber 15. The amount of bubbles generated is suppressed by limiting the amount of air bubbles. In other words, when the plunger 7 moves to the left in the figure during the suction stroke, the pressure inside the compression chamber 15 decreases below the pressure inside the pump chamber 4, making it easy for bubbles to generate and expand inside the compression chamber 15. At this time, due to the existence of the check valve 61, the trap volume from the communication passage 11 to the delivery valve 18 is not affected by the pressure drop. Therefore, in this portion, separation of air bubbles dissolved in the fuel and expansion of undissolved gas are reliably prevented. Further, when the plunger 7 moves to the compression stroke, the check valve 61 opens without resistance, so that fuel injection is not inhibited in any way.

Next, in the second embodiment shown in FIG. 2, a pressure regulating valve 62 is installed as a one-way valve at the end of the communication passage 11 on the cut-off port 12 side, and is composed of a spherical valve body 32a, a backup spring 32b, and a spring seat 32C. is installed.

The pressure regulating valve 62 is connected from the communication path 11 to the cut-off port 1.
The valve is oriented in such a way as to allow the fuel to flow in the direction 2 and to prevent the flow in the opposite direction, and the opening pressure in this case is set to prevent the separation of air bubbles from the fuel liquid. The pressure is set high enough to stop it.

In addition to the same effect as the first embodiment, this second embodiment mainly prevents the generation of air bubbles in the trap volume when the cutoff port 12 is opened at the end of injection.
By limiting it to only two parts, bubble generation fl' is suppressed. That is, when the cut-off port 12 is opened by sliding relative to the control sleeve 19, the pressure inside the trap volume decreases rapidly and bubbles are likely to be generated. The pressure of the above pressure regulating valve 6
When the pressure decreases to the set pressure of No. 2, the pressure regulating valve 62 closes and the area from the compression chamber 15 to the delivery valve 18 is maintained at a relatively high pressure, so that bubble generation in this area can be reliably prevented.

Therefore, in this second embodiment, in addition to the effects of the first embodiment, it is possible to lower the pressure inside the pump chamber 4 to approximately the same level as the pressure level when using normal liquid fuel. Also, in the suction stroke, the check valve 6 of the first embodiment
The same effect as in 1 can prevent a pressure drop in the area from the valve body 52a to the cut-off port 12.

Next, in a third embodiment shown in FIG. 3, both the above-mentioned check valve 61 and pressure regulating valve 62 are arranged in the communication passage 11. According to this embodiment, the generation of bubbles in the trap volume extending from the compression chamber 15 to the delivery valve 18 can be more reliably prevented.

Effects of the Invention As is clear from the above explanation, the distribution type fuel injection pump for a diesel engine according to the present invention enables reliable fuel injection even when using air-mixed fuel, and prevents air from being mixed in the fuel. rate can be increased sufficiently. Friend, even in a system that does not use air-mixed fuel, it has the effect of maintaining stable fuel injection performance in the unlikely event that air is mixed in.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the essential parts of a fuel injection pump showing a first embodiment of the present invention, and FIGS.
FIG. 4 is a cross-sectional view of the entire conventional fuel injection pump. 7...7' 9 Force, 8... Plunger barrel, 11... Communication path, 12... Cut-off port, 1
6... Distribution boat, 14... Suction groove, 15... Compression chamber, 16... Suction boat, 17... Discharge boat,
19... Control sleeve, 61... Check valve,
32...Pressure regulating valve.

Claims (1)

[Claims] (1) Distribution of a diesel engine that has a plunger and a cam disk that rotate integrally with the drive shaft, and the plunger rotates and reciprocates due to the cam action of the cam disk, compressing fuel and distributing it to each cylinder. In the type fuel injection pump, only flow from the compression chamber to the cutoff port is formed in a communication passage formed along the axial center of the plunger to communicate the compression chamber, the cutoff port, and the distribution port. 1. A distribution type fuel injection pump for a diesel engine, characterized in that it is equipped with a one-way valve having a predetermined opening pressure that allows for.