JPH01117982A - Fuel injector for diesel engine - Google Patents

Abstract

PURPOSE:To control the fuel feed into a plurality of injection nozzles by one unit of pump by supplying the fuel sent under pressure from the pump into a valve through a high pressure pipe and switching a valve by operating the energizing force resisting to the fuel pressure. CONSTITUTION:A plurality of injection nozzles 12a and 2b each of which possesses different injection characteristic and supplies fuel into a same cylinder in a Diesel engine 7 are installed onto a fuel injector 1. Further, a high pressure pipe 3 having a plurality of branched passages 3a and 3b which distribution- supplies the fuel which is sent under pressure from a fuel injection pump 6 into the respective injection nozzles 2a and 2b is installed. A valve 4 which is operated by the fuel pressure and switches the fuel supply into the injection nozzles 2a and 2b is installed into each branched passage 3a, 3b. The operation of the valve 4 is controlled by a control means 5 equipped with an energizing means in the direction resisting to the fuel pressure.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a fuel injection device for a diesel engine.

(Prior Art) Conventionally, a multi-hole nozzle a shown in FIG. 14, a single-hole nozzle b shown in FIG. 15, a throttle nozzle C shown in FIG. 16, etc. have been used as injection nozzles for engines. Multi-hole nozzle a has multiple nozzle holes in multiple directions, so the fuel spray condition can be controlled by selecting the diameter and number of each nozzle hole, making it possible to tune combustion over a range where engine rotation and torque fluctuate. However, the installation location was limited to the center of the combustion chamber.

In addition, single-hole nozzle b can be installed near the wall of the combustion chamber and produces less noise than multi-hole nozzle a, but it has poor fuel diffusion and requires combustion tuning in the range where engine rotation and torque fluctuate. It was difficult to do. Furthermore, the throttle nozzle C is the 17th
As shown in the figure, compared to multi-hole nozzle a and single-hole nozzle b, the variation in hole diameter area with respect to needle valve lift is very small in the initial process, so pre-injection can be performed prior to main injection. However, because the throttle period was short, there was a problem in that the nozzle holes were clogged with carbon, leading to a decrease in output. Therefore, as a means to take advantage of the advantages of each injection nozzle and solve the problems, an invention of a fuel injection device has been disclosed that aims to improve engine performance by controlling two injection nozzles with different hole diameters. (For example, see Japanese Patent Application Laid-open No. 117355/1983).

(Problems to be Solved by the Invention) However, with the above conventional technology, two fuel injection pumps are required to control the two injection nozzles, and another mechanism is required to control the injection timing. This poses a problem in that it increases costs and requires a complicated mechanism.

(Means for Solving the Problems) Means for solving the above problems of the present invention include a plurality of injection nozzles that supply fuel to the same cylinder, each having different injection characteristics, and a fuel injection pump that supplies fuel under pressure from a fuel injection pump. A high-pressure pipe equipped with a branch passage that distributes and supplies fuel to the injection nozzle; and a switch provided in the middle of the branch passage of the high-pressure pipe and operated by fuel pressure from a fuel injection pump to switch the fuel supply to the injection nozzle. A fuel injection device for a diesel engine, comprising: a valve; and a control means for controlling operation of the switching valve by means of an urging means for urging the operation of the switching valve in a direction opposite to the fuel pressure.

(Function) The fuel pumped under pressure from the fuel injection pump is transmitted to the switching valve through a high-pressure pipe, and the switching valve controls the pumped fuel by a control means provided in the switching valve to inject multiple injections with different injection characteristics. Inject from the nozzle into the engine.

(Embodiment) The fuel injection device of the present invention is characterized in that in a diesel engine equipped with two fuel injection nozzles per cylinder, one fuel injection pump controls two fuel injection nozzles. do. Examples will be described below based on the drawings.

As shown in FIG. 1, a fuel injection device 1 according to the present invention includes an injection nozzle 2, a high-pressure pipe 3, a switching valve 4, a control means 5, and a fuel injection pump 6 as main parts. Note that 7 indicates one cylinder of a general medium-swirl direct injection engine.

In order to atomize the fuel and inject it into the combustion chamber, the injection nozzle 2 is provided with a first injection nozzle 2a with a small hole diameter for pre-injection and a second injection nozzle 2b with a large hole diameter for main injection to control the injection amount. ing. Further, the first injection nozzle 2a and the second injection nozzle 2b can be set in opposite phases (see Fig. 4) by setting the mounting positions as shown in Figs. 4 to 7.
The first injection nozzle 2a and the first injection nozzle 2a may be set in the same direction (see Fig. 5), or the first injection nozzle 2a for pre-injection may be set to face inward in consideration of emissions (see Fig. 6). By changing and setting the injection angle of the two injection nozzles 2b (see FIG. 7), it is possible to maintain a spray state that matches the air flow in the combustion chamber of the engine. Note that 9 indicates the direction of the swirl.

In addition, although the one shown above is equipped with the first and second injection nozzles 2a and 2b in two separate injection nozzle bodies, one injection nozzle body has the first and second injection nozzles with different injection characteristics. 2a and 2b may be formed as one body.

The high-pressure pipe 3 is provided with a first branch passage 3a for feeding fuel under pressure to the first injection nozzle 2a and a second branch passage 3b for feeding fuel under pressure to the second injection nozzle 2b.

As shown in FIGS. 1 to 3, the switching valve 4 is provided with pressure receiving pipes 4c of different diameters so as to communicate with the parallel first branch passage 3a and second branch passage 3b.
The first pressure receiving pipe 4a on the side has a small cross-sectional area, the second pressure receiving pipe 4b on the second branch passage 3b side has a large cross-sectional area, and a step is provided at the connecting portion between the two. A fuel return passage of 4 m is provided in the stepped portion. In addition, the pressure receiving pipe 4
The left and right ends of C extend left and right across the first branch passage 3a and the second branch passage 3b, and the first
A pressure receiving surface 4d and a second pressure receiving surface 4e are provided. Inside the pressure receiving tube 4c, a switching piston 4 is provided with a rod portion 4f having a small cross section matching the shape of the first pressure receiving surface 4d and a rod portion 4g having a large cross section matching the shape of the second pressure receiving surface 4e.
h is built-in so that it can be moved left and right within the pressure receiving pipe 4c. Further, near both left and right ends of the switching piston 4h, a pressure receiving surface 4d receives fuel injection pressure from upstream of the branch passages 3a and 3b.
, 4e are provided with fuel passages 41°4k.

The control means 5 is provided on the first pressure receiving surface 4d and the second pressure receiving surface 4e, and the piston 4h is provided on the first pressure receiving surface 4d between the first pressure receiving surface 4d and the switching piston 4h. 4e
A spring 5a is provided as a biasing means for biasing in the direction, and in order to adjust the spring force of the spring 5a, a solenoid valve 5b for advancing and retracting the first pressure receiving surface 4d is provided at the rear of the first pressure receiving surface 4d. There is. On the other hand, the second pressure receiving surface 4e is provided with a concave step to reduce the pressure receiving area.
A pressure receiving surface 5c is provided.

As shown in Fig. 1, the fuel injection pump 6 is connected to a number of high-pressure pipes 3 corresponding to the number of cylinders in the engine 7.Fuel is injected into each high-pressure pipe 3 depending on how the accelerator (not shown) is opened. to pump.

Next, the operation of the fuel injection device 1 will be explained.

First, before the fuel injection pump 6 starts pumping fuel, the switching valve 4 is normally in the state shown in FIG. 2, opening the first branch passage 3a. Then, when the fuel injection pump 6 starts pressure feeding, since the first branch passage 3a is open, the first injection nozzle 2a opens and starts pre-injection of fuel to the engine 7. At this time, in a region where the injection amount is small, as shown in FIG. 8, the increase in the pressure inside the high-pressure pipe 3 is small, so the pre-injection ends with only the first injection nozzle 2a having a small hole diameter. Furthermore, as the injection amount increases, the pressure inside the high-pressure pipe 3 increases because the injection rate is low if only the pre-injection from the first injection nozzle 2a is performed. Then, as shown in Fig. 11, (3rd pressure receiving surface x 2nd pressure receiving surface
When the partial pressure of the branch passage) becomes (first pressure receiving surface x partial pressure of the first branch passage + spring force), the switching piston 4h moves to the right.

The branch passage 3b on the second injection nozzle 2b side is opened, and the ninth
As shown in the figure, main injection of fuel is performed from the second injection nozzle 2b having a large hole diameter. When the injection amount further increases, as shown in FIG.
The pre-injection amount from a is further reduced, most of the fuel is injected from the second injection nozzle 2b with a large hole diameter, and the switching valve 4 is in the state shown in FIG.

Next, control of the fuel injection device 1 will be explained.

The absolute amount of fuel sent to the first injection nozzle 2a and the second injection nozzle 2b is controlled by the fuel injection pump 6. The control means 5 provided in the switching valve 4 controls the injection switching speed and injection switching point 8 from the first injection nozzle 2a to the second injection nozzle 2b according to the fuel pressure of the fuel sent from the fuel injection pump 6. control.

The injection switching speed is determined by the second pressure receiving surface 4e and the third pressure receiving surface 5c.
When the area difference is increased, the pressure receiving area that suddenly applies fuel pressure from the third pressure receiving surface 5c to the second pressure receiving surface 4e becomes larger when the switching piston 4h starts moving. Therefore, the switching piston 4h
The moving speed becomes faster, and the switching speed can be increased.

On the other hand, the injection switching point 8 is as shown in FIG.
It can be controlled by the spring force of the spring 5a provided between the first pressure receiving surface 4d and the switching piston 4h.If the spring force is strengthened, the pre-injection period from the first injection nozzle 2a becomes longer, and the spring force is increased. When weakened, the first
The period of pre-injection from the injection nozzle 2a becomes shorter and the period of main injection from the second injection nozzle 2b becomes longer. moreover,
This injection switching point is determined by electronically or mechanically controlling the solenoid valve 5b to the first point while the engine 7 is running.
By moving the pressure receiving surface 4d back and forth to adjust the spring force of the spring 5a, various operating conditions can be accommodated. For example, in the case of electronic control by a computer, when starting the engine 7, as shown in FIG. 12, in order to increase the starting amount, the spring 5a is released and the injection is made from the second injection nozzle 2b, which has a larger hole diameter than at the time of starting. Starting control can be performed by inputting a starting program that starts control using the spring force after the rotation of the engine 7 has stabilized. Then, as shown in Fig. 13, the engine 7 is started by correcting the spring force according to the water temperature and acceleration operation state, and then inputting a program that controls the spring force according to the engine speed and load. , it is possible to prevent half-misfire of the engine and perform acceleration control.

(Effects) A single fuel injection pump can control fuel supply to multiple injection nozzles, and control the injection rate or injection period.

[Brief explanation of the drawing]

1 to 13 are drawings of a fuel injection device for a diesel engine according to the present invention, in which FIG. 1 is a schematic diagram of the fuel injection device, FIGS. 2 and 3 are sectional views showing a switching valve, and FIG. Figures 4 to 7 are schematic diagrams showing examples of settings for the first injection nozzle and the second injection nozzle, and Figures 8 to 10 show the relationship between the injection amount and crank angle of the first injection nozzle and the second injection nozzle. 11 is a graph showing the relationship between the forces applied to each part of the switching valve as the pressure rises in the high-pressure pipe. FIGS. 12 and 13 are flowcharts showing examples of control by computer control, and FIGS. Figure 16 is a vertical sectional view showing various injection nozzles, the first
FIG. 7 is a graph showing changes in the hole diameter area with respect to the needle valve lift amount of the various injection nozzles shown in FIGS. 14 to 16. 1...Fuel injection device, 2...Injection nozzle, 3...High pressure pipe, 3a...First branch passage, 3b... 2nd branch passage, 4...
Switching valve, 5... Control means, 5a...
...Spring, 6...Fuel injection pump, 7...Engine. Figure 11 Figure 7 Figure 14 Figure 15 Figure 16 Figure 170 Figure 12

Claims (1)

[Claims] (1) A high-pressure pipe equipped with a plurality of injection nozzles each having different injection characteristics for supplying fuel to the same cylinder, and a branch passage for distributing and supplying fuel pumped from a fuel injection pump to the injection nozzles, and the high-pressure pipe A switching valve is provided in the middle of the branch passage and is operated by the fuel pressure from the fuel injection pump to switch the fuel supply to the injection nozzle, and a biasing valve that biases the operation of the switching valve in a direction opposite to the fuel pressure. 1. A fuel injection device for a diesel engine, characterized in that the fuel injection device is provided with a control means for controlling by a power means.