JPH0373755B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a fuel injection valve for an internal combustion engine.

A conventional fuel injection valve of this type is shown in FIG. In the figure, 01 is the fuel injection valve body, 02 is the oil passage inside the fuel injection valve, 03 is the needle valve, and the fuel injection valve body 01
is slidably inserted within. 04 is a needle valve push rod, 05 is a needle valve spring, and the spring force is applied to the needle valve 03 via the push rod 04 to the valve seat 01 provided inside the nozzle 08.
Pressing to 02. 06 is the valve opening pressure adjustment screw, 0
7 is a spring chamber. The nozzle 08 communicates the oil reservoir 0101 with a combustion chamber (not shown) in the cylinder of the engine. 09 is a discharge port.

The fuel oil is compressed by the fuel injection pump (not shown) and becomes high pressure, while the injection pipe (not shown)
through the oil passage 02 in the fuel injection valve to the oil sump 0.
It reaches 101. The needle valve 03 is pressed against the valve seat 0102 by a spring 05, and is opened so that it does not rise, that is, does not open, unless the fuel oil pressure in the oil reservoir 0101 reaches a certain pressure, that is, the valve opening pressure P ₀ or higher. The initial spring force is set by the valve pressure adjustment screw 06. Therefore, the high pressure wave sent from the fuel injection pump increases the valve opening pressure at the oil sump 0101.
When the pressure reaches P ₀ or more, the needle valve 03 rises, the volume of the oil reservoir 0101 increases, a part of the fuel sent from the fuel injection pump is used for this, and the rest flows into the combustion chamber from the nozzle 08. It ejects, ignites and burns to produce output. When the fuel injection pump finishes discharging, the pressure in the oil sump 0101 decreases, and when this pressure falls below the valve closing pressure, the needle valve 03 is pressed down by the spring 05, and the oil sump 0101 is closed. The volume decreases, a part of which is injected from the nozzle 08, and when the needle valve 03 is seated on the valve seat 0102, the injection ends. Note that leakage from the sliding portion of the needle valve 03 during this period reaches the spring chamber 07 and is discharged through the discharge port 09.

However, the above method has the following drawbacks.

In order to reduce the combustion noise of diesel engines, it is necessary to reduce the amount of fuel during the ignition delay period, and one method to achieve this from the fuel injection side is to reduce the injection rate at the initial stage of injection. It is said that it is effective to suppress the With conventional models, the volume of the oil reservoir increases as the needle valve rises, so part of the fuel delivered from the fuel injection pump is used for this, and the rest is injected from the nozzle, so the injection at the initial stage of injection is reduced. On the other hand, when the needle valve descends due to a decrease in pressure, the volume of the oil reservoir decreases, and some of it is injected from the nozzle, so
Even in the latter half of the injection after the main injection ends, the injection at low pressure and low injection rate continues sluggishly as shown in FIG. 2, which has the disadvantage of worsening smoke exhaust and the like.

The purpose of the present invention is to focus on the above-mentioned points, to suppress the injection rate at the initial stage of injection, that is, to ensure a long period of low injection rate, and to prevent low-pressure, low-injection-rate injection in the latter stage after the end of main injection. The purpose of the present invention is to provide a fuel injection valve that can improve the cutting of fuel, and its feature is that an oil sump into which fuel from a fuel injection pump is introduced communicates with the combustion chamber of a cylinder. A fuel injection valve for an internal combustion engine that has a nozzle that opens and closes the nozzle by attaching and detaching it to a valve seat provided inside the nozzle, and a needle valve that opens and closes the nozzle by attaching to and removing from a valve seat provided inside the nozzle. a suction-return piston housed in a manner that is possible to accommodate the suction-return piston; an oil passage that communicates the head space of the suction-return piston with the oil reservoir; The present invention includes a drive device that drives in a direction to increase the volume of the head side space.

In this case, after the main injection ends, the volume of fuel pushed out by the needle valve is sucked back by the suction piston.
It can prevent spouting from the nozzle.

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

FIG. 3 is a sectional view showing one embodiment of a fuel injection valve according to the present invention.

In the figure, 1 is the fuel injection valve body, 2 is the oil passage,
A needle valve 3 is slidably inserted into the fuel injection valve main body 1. 4 is the needle valve push rod, 5 is the needle valve spring,
The spring force presses the needle valve 3 through the push rod 4 against a valve seat 102 provided inside the spout 8 . 6 is a valve opening pressure adjustment screw, and 7 is a spring chamber. Nozzle 8 is oil sump 1
01 and a combustion chamber (not shown) in the cylinder of the engine. 9 is a discharge port.

Reference numeral 10 denotes a suction piston, which is slidably housed in a space formed inside the fuel injection valve.
11 is a suction and return piston spring, 12 is a suction and return piston driving rod, and 13 is a suction and return piston drive cam.

Reference numeral 14 denotes an oil reservoir for the suction piston 1 in the space in which the suction piston 10 is accommodated.
This is the space on the piston head side of No. 4.

15 is an oil passage for the suction and return piston, and oil sump 10
1 and the space on the head side of the suction/return piston 14 are communicated with each other.

The operation in the case of the above configuration will be described.

The fuel oil is compressed by the fuel injection pump (not shown) and becomes high pressure, while the injection pipe (not shown)
through the oil passage 2 in the fuel injection valve to the oil sump 10.
It reaches 1. The needle valve 3 is pressed against the valve seat 102 by the spring 5, and does not rise unless the fuel oil pressure in the oil reservoir 101 reaches a constant pressure, that is, the valve opening pressure P ₀ or more.
Therefore, when the high-pressure pressure wave sent from the fuel injection pump becomes equal to or higher than the valve opening pressure P ₀ at the oil sump 101, the needle valve 3 rises, the volume of the oil sump 101 increases, and the oil sump 101 is injected from the fuel injection pump. A part of the fuel is used for this purpose, and the rest is injected from the nozzle 8 into the combustion chamber, where it is ignited and combusted to produce output. When the fuel injection pump finishes discharging, the pressure in the oil reservoir 101 decreases, and when this pressure falls below the valve closing pressure, the needle valve 3 is pressed by the spring 5 and begins to descend.

On the other hand, while the needle valve 3 is rising, the suction piston 10 is pushed down via the drive rod 12 by the suction piston drive cam 13 and remains in a fixed position. It is set to start moving upward, that is, in a direction that increases the volume of the piston head side space, almost synchronously with the start of the displacement in the valve closing direction. Therefore, most of the fuel corresponding to the change in volume when the needle valve 3 descends passes through the oil passage 15 and is sucked back by the suction piston 10, and is not injected from the injection port 8. In addition, during the period after the needle valve 3 is seated until the next injection starts, the suction piston 10 is slowly lowered by the drive cam 13,
The amount of fuel sucked back is slowly pushed back and is not related to fuel injection. Note that leakage from the sliding portion of the needle valve 3 during this period reaches the spring chamber 7 and is discharged through the discharge port 9.

The above effects can be summarized with a focus on the fuel injection rate as follows.

(1) At the beginning of injection, the volume increases due to the rise of the needle valve, which is not affected by the action of the suction piston, and as with conventional fuel injection valves, a large amount of the fuel sent from the fuel injection pump is used for this purpose. Since the amount of fuel is large, the injection rate at the initial stage of injection is suppressed to a low level.

(2) In the latter half of injection, most of the fuel that changes in volume due to the drop of the needle valve is sucked back by the suction piston and is not injected from the nozzle. Therefore, it is possible to prevent the low-pressure, low-injection-rate injection from continuing sluggishly after the end of the main injection, and the injection becomes more sharp.

Therefore, the injection rate mode is as shown in FIG.

Note that the above can also be applied to a hall type fuel injection valve.

The above case has the following effects.

(1) The amount of fuel during the ignition delay period can be reduced, and combustion noise can be reduced.

(2) It is possible to prevent low-pressure, low-injection-rate injection from continuing sluggishly, reducing smoke emissions, fuel consumption, etc.

FIG. 5 is a side view showing a main part of a fuel injection valve according to another embodiment of the present invention in cross section.

In the figure, numbers 1 to 9 and 101, 1
02 is the same as that shown in FIG. 3 showing the embodiment described above.

20 is a suction piston, 21 is a suction piston spring, 22 is a fixed iron core, 23 is a coil, 24 is a terminal, 25 is a needle valve lift sensor, and 26 is an oil passage for the suction piston.

Since the operation during the first half of the injection, that is, the period from when the needle valve 3 rises until it starts to descend thereafter, is the same as in the embodiment described above, the second half of the injection will be described.

When the pressure in the oil reservoir 101 decreases and becomes equal to or less than the valve closing pressure, the needle valve 3 is pressed by the spring 5 and descends to be seated. At this time, the movement of the needle valve 3 is detected by the needle valve lift sensor 25, and a signal is generated when the needle valve 3 starts to descend.This signal is input to a control unit (not shown). Ru. The coil 23 is connected to a control unit by a terminal 24, and when the coil 23 is energized by the above-mentioned signal, the suction/return piston 20 is attracted to the fixed iron core 22 and moves upward. That is, the volume of the space on the piston head side increases.

Therefore, most of the fuel corresponding to the volume change when the needle valve 3 descends is sucked back by the suction piston 20 through the oil passage 26, and is not injected from the injection port 8. In addition, after the needle valve 3 is seated, the lift sensor 25 detects a seating signal, and during the period until the next injection starts, the suction piston 20 slowly descends, and the sucked back fuel is slowly released. It is pushed back and is not related to fuel injection.

Therefore, the injection rate mode is similar to that shown in FIG. 4 described above. The effect is the same as in the previous embodiment.

[Brief explanation of drawings]

Figure 1 is a sectional view showing a conventional fuel injection valve, Figure 2 is a sectional view showing a conventional fuel injection valve.
3 is a diagram showing the fuel injection rate of the fuel injection valve of FIG. 1, FIG. 3 is a sectional view showing a fuel injection valve of an embodiment of the present invention, and FIG. A diagram showing the injection rate, and FIG. 5 is a side view showing a main part of a fuel injection valve according to another embodiment of the present invention in cross section. 3... needle valve, 8... nozzle, 101... oil sump,
102... Valve seat, 10, 20... Suction-back piston, 14... Suction-back piston head side space, 15,
26...Oil road.

Claims (1)

[Claims] 1. An oil sump into which fuel is introduced from the fuel injection pump, a nozzle that communicates the oil sump with the combustion chamber of the cylinder, and a needle that opens and closes the nozzle by attaching and detaching it to a valve seat provided inside the nozzle. In a fuel injection valve for an internal combustion engine having a valve, a suction piston is slidably accommodated in a space formed inside the fuel injection valve, and a head side space of the suction piston and the oil reservoir are connected. The invention is characterized by comprising a communicating oil passage and a drive device that drives the suction piston in a direction that increases the volume of the head side space substantially in synchronization with the start of displacement of the needle valve in the valve closing direction. fuel injection valve.