JPH029944A - Fuel injection device - Google Patents

Abstract

PURPOSE:To gradually increase the volume of a control chamber and properly suppress the initial injection rate by integrally moving a control valve body via a projection as a valve body communicating or cutting off the control port and the discharge port of a three-way solenoid valve is opened. CONSTITUTION:When a current is fed to a solenoid coil 49, an armature 39 is attracted by a core 47, an outer valve 36 serving as a valve body is raised, a poppet section 37 is released from the first valve seat 34, thus a control port Y and a discharge port Z are communicated, fuel is injected through a nozzle not shown in the figure. When the outer valve 36 is further raised, the second valve seat 43 is pressed to a poppet section 46, thus a feed port X and the control port Y are cut off. As the outer valve 36 is raised, a control valve body 9 is kept in contact with a projection 38 by the pressure difference between pressures applied to its front and back and the energizing force of a return spring and raised together with the outer valve 36. The volume of a control chamber 8 is gradually increased.

Description

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

(Prior art) First, as a prior art, the diesel engine fuel injection device disclosed in W [1985-165858] was
This will be explained based on the diagram.

In FIG. 5, pump 29 and pressure ri! 4 regulator 26
The fuel pressurized to a constant high pressure passes through the conduit 27 and is supplied to the fuel reservoir chamber 1c formed above the valve seat 1b of the fuel injection nozzle 1 via a buffer device (for example, an accumulator) 28 on the one hand, and on the other hand. It leads to the conduit 11 via a three-way solenoid valve 12 controlled by an electronic control device 15 which receives a signal from a bottom dead center detector 16 indicating the reference position;
Furthermore, it has arrived at a control chamber 8 in which a control valve body 9 and a return spring 7 are housed.

The pressure of the fuel introduced into the control chamber 8 is configured to act on the needle 1a of the fuel injection wave ra1 via the hydraulic piston 6 and the pin 4. Further, an orifice 10 is formed in the control valve body 9, with one end opening into the control chamber 8 and the other end opening into the conduit 11.

When the three-way solenoid valve 12 is not energized, the 17-way pipe 1
The discharge port Z of the three-way solenoid valve 12 connected to the three-way solenoid valve 3 is cut off from the control port ()Y, and the control port ()Y and the supply port ()X are communicated with each other, and the control chamber 8 is filled with high-pressure fuel. The fuel that has arrived at the fuel reservoir IC tries to push up the needle 1a due to its pressure, but the hydraulic piston 6 and the bottle 4
．． 7 Control chamber 8 acting on needle 1a via flange 3
The pressure of the valve and the force of the spring 5 are superior to each other, and as a result, the needle 1a is seated on the valve seat 1b and no fuel is injected. Here, the return spring 7 is used to prevent the control valve body 9 from floating when the hydraulic piston 6 moves up and down, and its force is dependent on the force of the spring 5 and the pressure acting on the hydraulic piston 6. It is set so small that it can be ignored in comparison.

When the three-way solenoid valve 12 is energized, the supply bow () The discharge bow ()Z connected to the conduit 13 and the control bow ()Y are communicated with each other.

The pressure in the conduit 11 therefore decreases, and the pressure in the control chamber 8 also decreases relatively slowly due to the action of the orifice 10 formed in the control valve body 9.

When the difference between the upward force due to the pressure in the fuel reservoir IC and the downward force due to the pressure in the control chamber 8 exceeds the force of the spring 5 even slightly, the needle 1a begins to open. When the needle 1a is raised by a small height, its momentum is accelerated by the pressure exerted on the surface of the seat.

At the end of the preset injection period, the excitation of the three-way solenoid valve 12 is interrupted, the supply bow ()X connected to the conduit 27 is opened and the discharge bow ()Z connected to the leak conduit 13 is closed. As a result, high pressure fuel flows into the control chamber 8 from the conduit 27 . At this time, the control valve body 9 opens downward in the figure against the weak return spring 7, and a suddenly large passage area is secured. Eventually, when the force of the spring 5 exceeds the difference between the pressure in the fuel reservoir IC and the pressure in the control chamber 8, the needle 1a is pushed down and the injection ends.

(Problems to be Solved by the Invention) According to the conventional device described above, when the three-way solenoid valve 12 is energized and the control chamber 8 is brought into communication with the control chamber 8
The pressure gradually decreases due to the action of the first and first fittings 10, and the needle 1a retreats from the valve seat 1b at a substantially constant speed. The characteristic curve representing the amount of stroke of the needle 1a at this time becomes a straight line as shown by the dashed line in FIG. 3d.

By the way, in order to suppress the initial injection rate of the fuel injection nozzle 1, the diameter of the orifice 10 is made small, and
It is possible to reduce the slope of the lift characteristic curve as shown by the α-dashed line, but in that case, the injection rate will change according to the characteristic curve of the 7F amount as shown by the two-dot chain line in Figure 3e. There was a problem in that the ratio of the maximum injection rate period to the injection period became small.

SUMMARY OF THE INVENTION In view of these problems, it is an object of the present invention to provide a fuel injection device that can suppress the initial injection rate without shortening the maximum injection rate period.

(Means for Solving the Problems) The configuration of the present invention in accordance with the above object is that a supply port, a control port, and a discharge port are provided, and communication is selectively interrupted between the supply port and the control port and between the control port and the discharge port. A three-way solenoid valve, a control chamber communicating with a control port of the three-way solenoid via a 17th valve, and a control valve body in which the oriice is formed and movably disposed in the control chamber, In a fuel injection device configured to control the advance and retreat of a needle of a fuel injection nozzle by a pressure drop in a chamber, the three-way solenoid valve is provided with a valve body that is operated to open and close by electromagnetic means to disconnect communication between a control port and a discharge port; forming a protrusion on the valve body that abuts the control valve body;
The gist of the present invention is that during the initial stroke of the opening operation of the valve body, the valve body and the control valve body move together to increase the volume of the control chamber.

(For A) According to the above configuration, during the initial stroke of the opening operation of the valve body that cuts off communication between the control port and the discharge port pipe, the valve body and the control valve body move together to increase the volume of the control chamber. To increase. Therefore, the pressure in the control chamber decreases as the volume increases.

On the other hand, when the initial stroke of the opening operation of the valve body is completed, the movement of the control valve body also stops, so that the control chamber volume no longer increases. Therefore, after the initial stroke, the control chamber pressure decreases at a rate determined by the diameter of the oriice.

As described above, during the opening operation stroke of the valve body, the rate of pressure drop in the control chamber changes in two stages, and accordingly, the retraction speed of the needle also changes in two stages. Therefore, by appropriately setting the initial retraction speed of the needle, the initial injection rate can be suppressed without shortening the maximum injection rate period.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is an enlarged sectional view of a main part of an embodiment to which the present invention is applied. In FIG. 1, the three-way solenoid valve 12 provided in the fuel injection device has a supply port (X), a control port (Y), and a discharge port (X).
The valve body 30 includes a passage 31 with one end opening to the control bow (Y), an oil chamber 32 connected to the other end of the passage 31, and an oil chamber 32. A passage 33 is formed to communicate with the discharge port Y, and the control port Y and the discharge port Z are connected by the passage 31, the oil chamber 32, and the passage 33. Further, a first valve seat 34 is provided in a portion where the passage 31 and the oil chamber 32 are connected, and a first valve seat 34 is provided opposite to the first valve seat 34.
An f & matching hole 35 is bored.

In this first fitting hole 35, an outer valve 36 is slidably formed as a valve body for disconnecting communication between the control bow (Y) and the discharge bow (2). A poppet portion 37 that approaches and separates from the first valve seat 34 and a protrusion 38 that penetrates the passage 31 are formed at the tip of the outer valve 36 .

On the other hand, a control chamber 8 is disposed in connection with the control valve Y, and a control valve body 9 having an orifice 1o is movably disposed in the control chamber 8, and is supported by a return spring 7.
It is biased in the Y direction.

The protruding portion 38 is arranged such that the poppet portion 37 is connected to the first valve seat 3.
4, the control valve body 9 is set so that it slightly protrudes from the control valve body 9 and comes into contact with the control valve body 9. In addition, 6
is a hydraulic piston.

Next, an armature 39 is provided at the rear end of the outer valve 36.
are integrally fixed, and a passage 40 opening at the tip end face of the protrusion 38 and an oil chamber 41 connected to the passage 40 are formed inside. The passage 40, the oil chamber 41, and the passage 42 connect the supply port

Further, a second valve seat 43 is provided in a portion where the passage 40 and the oil chamber 41 are connected, and a second fitting hole 44 is connected to the oil chamber 41 so as to face the second valve seat 43 .

An inner valve 45 is fitted into the second fitting hole 44 to cut off communication between the supply bow (X) and the control bow (Y).
The outer valve 36 and the inner valve 45 are assembled so as to be slidable relative to each other. and inner valve 4
5 has a poppet portion 4 that comes into contact with and separates from the second valve seat 43.
6 is formed, and its rear end abuts against a stopper portion 48 formed as a part of a core 47 attached to the upper part of the valve body 30, thereby preventing upward movement in the figure. This is a solenoid coil for magnetizing the four-piece core 47. These core 47, solenoid coil 49 and the armature 3
Reference numeral 9 constitutes electromagnetic means for attracting the outer valve 36. 50 urges the after valve 39 downward in the figure,
This is a spring for bringing the poppet portion 37 into pressure contact with the first valve seat 34.

Note that the other configurations of this embodiment are the same as those of the conventional fuel injection device described based on FIG. 5, so the explanation will be omitted.

This embodiment has the above-mentioned configuration, and its operation will be explained in the second section.
This will be explained based on FIGS. a-2d.

FIG. 2a shows a state in which no current is applied to the solenoid coil 49, and at this time, the outer valve 36 is pushed down by the spring 50 and hydraulic pressure, and the poppet portion 37 is pressed against the first valve seat 34, causing the control port The connection between Y and the discharge port 2 is cut off.

On the other hand, at this time, the hydraulic pressure of the oil chamber 41 acts upward on the poppet portion 46 of the inner pulp 45, and the stopper portion 48
Since the poppet portion 46 is pushed up until it comes into pressure contact with the second valve seat 43, the supply bow ()X and the control bow ()Y are communicated with each other. Therefore, high-pressure fuel pumped from the pump 29 is introduced into the control chamber 8 via the orifice 10.

As a result, the needle 1a comes into pressure contact with the valve seat 1b, and the nozzle 1
Fuel injection from the

Next, when a current is applied to the twist/id fill 49 from the state shown in FIG. 2a, the armature 3
9 is sucked into the core 47, the outer pulp 36 slides upward, and the poppet portion 37 separates from the first valve seat 34 to control a.
B) Y and the exhaust port Z communicate with each other, and fuel injection from the nozzle 1 is started. When the outer pulp 36 is further sucked upward, the second valve seat 43 formed on the outer pulp 36 comes into pressure contact with the poppet portion 46 of the inner pulp 45 as shown in Figure #2c, so the outer pulp 36 stops and the supply board is closed. )X and control port Y are blocked.

FIG. 3a shows a characteristic curve showing the lift amount of the 7 outer valve 36. When the solenoid coil 49 is excited at time t1, the outer valve 36 starts moving upward, and at time t, the second valve seat 43 comes into contact with the inner pulp 45 and stops.

From the beginning of the opening operation stroke in which the outer pulp 36 is sucked upward, that is, from time t1 shown in FIG.
As shown in the figure, the control valve body 9 moves upward together with the outer pulp 36 while remaining in contact with the protrusion 38 due to the pressure difference acting before and after the control valve body 9 and the biasing force of the return spring 8. Therefore, since the volume of the control chamber 8 gradually increases, the pressure in the control chamber 8 gradually decreases as shown in FIG. 3C. Therefore, as shown in FIG. 3d, from time t to time L2, the needle 1a gradually rises, and the initial injection rate of the fuel injection nozzle 1 is suppressed as shown in FIG. 3e.

After the initial stroke, the control valve body 9 comes into contact with the bottom surface of the valve body 30 forming the control bow (Y) and stops, so the volume of the control chamber 8 no longer increases.

Therefore, from time t2 to time t2, the pressure in the control chamber 8 rapidly decreases at a rate determined by the diameter of the orifice 10, as shown in FIG. 3C. Needle 1a# accordingly
J increases rapidly, and the injection rate of nozzle 1 quickly reaches the maximum injection rate.

Next, when the applied current to the four solenoid coils is cut off, the outer pulp 36 rapidly descends from the poppet section 46 to the second valve seat 43 due to the force of the spring 50 and the pressure of the oil chamber 41.
At the same time as the valve is removed, the bovet part 37 comes into pressure contact with the first valve seat 34. Therefore, the supply bow) It descends and presses against the valve seat 1a, completing fuel injection.

When high-pressure fuel flows into the control chamber 8, the control valve body 9 is also pushed down as shown in FIG. 2d, but when the control chamber 8 is filled with high-pressure fuel, it is pushed up by the force of the return spring 9, as shown in FIG. As shown in FIG. 3, it comes into contact with the tip of the protrusion 38 and stops.

In the above embodiment, the control valve body 9 has a single orifice 10.
However, as shown in Fig. 4, this orifice 10
By forming the orifice 10a with a smaller diameter than the above, the pressure drop in the control chamber 8 can be appropriately reduced! You may adjust it.

(Effects of the Invention) According to the present invention, a protrusion that abuts the control valve body disposed in the control chamber is formed on the valve body that blocks communication between the control port and the discharge port of the three-way solenoid valve. During the initial stroke of the opening operation of the body, the valve body and the control valve body move together to increase the volume of the control chamber, so the retraction speed of the fuel injection nozzle needle is adjusted during the opening stroke. It can be changed from Therefore, by appropriately setting the initial retraction speed of the needle, it is possible to suppress the initial injection rate without shortening the maximum injection rate period of the fuel injection nozzle.

[Brief explanation of the drawing]

FIG. 1 is an enlarged sectional view of the main part of the first embodiment of the present invention, and FIG.
Figures 2d to 2d are explanatory diagrams of the operation of the first embodiment, and Figures 3a-e
4 are characteristic curves showing the outer valve thickness, control valve lift amount, control chamber pressure drop, needle lift amount, and injection nozzle injection rate, respectively, provided in the first embodiment, and FIG. of! 5th enlarged cross-sectional view of main parts of lR2 embodiment
The figure is a schematic configuration diagram showing a conventional fuel injection device. 1... Fuel injection nozzle, 1a... Needle, 8...
- Control chamber, 9... Control valve body, 10 = 10a... Orifice, 12... Three-way solenoid valve, 36... Outer valve (as a valve body), 38... Projection, 39.・・・
Armature, 47... Core, 49... Solenoid coil, X... Supply port, Y... Control port, Z
...Exhaust port. Figure 2a Figure 2b [3 Figure 2C Figure 2t3 Figure 2d Figure 4

Claims (1)

[Claims] A three-way solenoid valve that is provided with a supply port, a control port, and a discharge port and selectively communicates and shuts off communication between the supply port and the control port and between the control port and the discharge port, and an orifice in the control port of the three-way solenoid valve. A control room communicated via
In the fuel injection device, the orifice is formed and a control valve body is movably disposed in a control chamber, and is configured to control the advance and retreat of a needle of a fuel injection nozzle by a pressure drop in the control chamber. The solenoid valve is provided with a valve body that is opened and closed by electromagnetic means to cut off communication between the control port and the discharge port, and the valve body is formed with a protrusion that comes into contact with the control valve body, and the valve body is provided with a protrusion that comes into contact with the control valve body, and the valve body is provided with a valve body that is opened and closed by electromagnetic means to disconnect communication between the control port and the discharge port. A fuel injection device characterized in that during a stroke, the valve body and the control valve body move together to increase the volume of the control chamber.