JPS593164A - Fuel injection device - Google Patents

Abstract

PURPOSE:To increase the velocity of fuel feed under pressure, by accumulating fuel pressure fed to an injection nozzle during the pressure feed of fuel by a plunger, and by supplying the pressure-fed fuel by the plunger in a large amount to the injection nozzle after the accumulated fuel is supplied to the injection nozzle at once. CONSTITUTION:A delivery valve is arranged such that a cylinder 5 and a valve guide 6 are successively disposed in the holder 4 of a piston valve unit 1 in the axial direction thereof. Further, a piston value 11 is slidably disposed in the cylinder and a pressure adjusting valve 12 is slidably disposed in the valve guide 6. Both valves 11, 12 define therebetween an accumulating chamber 14 in which a compression spring 13 is disposed. Further, the piston valve is displaced in accordance with balance pressure acting on the left and right pressure receiving areas thereof so that the piston valve 11 may open and close fuel supply passage 10, 19 and an introduction port 17. Further more, the pressure adjusting valve 12 is arranged to open and close the communication between the fuel supply passage 10 and the accumulating chamber 14 in accordance with fuel pressure in the passage 10 downstream of the above-mentioned valve 11.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection device for a fuel-injected internal combustion engine.

As a conventional example of this type of fuel injection device, a delivery valve is disposed between the pressure oil chamber of the plunger barrel housing the plunger and the injection nozzle. A configuration is well known in which the valve is opened to supply fuel to an injection nozzle, and the fuel is injected from the injection nozzle into a combustion chamber. (Hakuryo Jidosha Co., Ltd.)
For example, the fuel injection pressure of a direct injection diesel engine, especially a small engine with one cylinder of 3 to 5 oocc, is 10.
00 atmospheres or higher, the atomization properties of the fuel improve, resulting in better mixing of air and fuel, improving fuel efficiency, reducing smoke, NOx, and HC emissions, and even with weak swirl, combustion is possible. It is known that improvement is expected.

Regarding such an increase in fuel injection pressure, according to the above-mentioned conventional method, fuel injection from the injection nozzle starts only when the pressure of the fuel pumped through the delivery pulp exceeds the injection nozzle opening pressure. A sufficiently high injection pressure could not be obtained unless the fuel pumping speed was set to a very high speed.In order to solve this problem, it seems that the valve opening setting load of the pulp spring should be increased, but in this case Even if it is possible to increase the valve opening pressure, it is not necessarily possible to increase the injection pressure.In other words, the fuel pressure after opening the valve is applied to the back of the valve so that it acts on the delivery pulp in the valve closing direction. In addition to the rotation, the larger the set load of the spring, the smaller the valve opening lift.For this reason, the pressure loss of the delivery pulp increases and the injection pressure also decreases.

To prevent this, increase the fuel pumping speed as described above.
Alternatively, the cam shape must be devised to increase the plunger speed, but due to the special cam shape, wear on the cam surface increases, causing a problem of lack of practicality. Also,
It is possible to increase the injection pressure by increasing the opening pressure of the injection nozzle, but in this case it is necessary to significantly strengthen the spring force of the injection nozzle, and as a result, secondary injection is more likely to occur, and the injection nozzle There is a problem in that it becomes large.

The present invention has been made by focusing on such conventional problems, and the fuel pressure to be supplied to the injection nozzle is accumulated in the plunger pressure feeding process, and the accumulated pressure is supplied to the injection nozzle at once, and then the plunger The purpose is to increase the fuel pumping speed and fuel injection pressure by supplying a large amount of pumped fuel to the injection nozzle.

In order to achieve such an object, the present invention specifically provides a pressure accumulator chamber that communicates with a fuel supply passage from an injection pump to an injection nozzle via an inlet, and a pressure receiving surface on one side of the pressure accumulator chamber and a side opposite to the pressure receiving surface. a first valve body, each having a pressure receiving surface facing the fuel supply passage and opening and closing the fuel supply passage and the inlet by displacing according to the pressure balance acting on both pressure receiving surfaces; a second valve body that opens and closes communication between the fuel supply passage downstream of the first valve body and the pressure accumulation chamber according to the fuel pressure in the fuel supply passage downstream of the first valve body;
The first valve body is configured to open the inlet port before the fuel supply passage is opened in response to an increase in the pressure of the fuel pumped from the injection pump.

The present invention will be explained below with reference to embodiments shown in the drawings.

FIG. 1 shows a piston nozzle unit corresponding to the conventional delivery pulp used in the fuel injection device of the present invention. The piston pulp unit 1 is attached to an injection pump body 2 and has a holder 4 screwed into a mounting hole 3 of the injection pump body 2. A cylinder 5 and a cylindrical pulp guide 6 are disposed inside the holder 4. are arranged in conjunction with each other in the axial direction. The cylinder 5 has a flange 5a at one end held between the tip of the holder 4 and a stopper 7 installed at the innermost part of the mounting hole 30, and the pulp guide 6 has a spacer 9 that abuts against the step 8 of the holder 40. is supported and fixed. A fuel supply passage 10 is formed by providing a groove in the axial direction on the inner peripheral surface of the holder 4.

Inside the cylinder 5 is a piston pulp (first valve body) 11.
is slidably disposed within the pulp guide 6, and a pressure regulating valve (second valve body) 12 is slidably disposed within the pulp guide 6. A compression coil spring 13 is interposed between the piston valve 11 and the pressure regulating pulp 12, and a pressure accumulation chamber 14 is formed. The piston valve 11 normally comes into contact with the stopper 7 and stops.

A valve body portion 15 provided on the pressure regulating pulp 12 is in contact with an end valve seat of the pulp guide 6. Furthermore, the movement distance of the piston valve 11 to the right is limited by a stopper 16 that projects from the pressure regulating valve.

The cylinder 5 has a plurality of first introduction ports 17 and a plurality of second introduction ports 18 which are spaced apart from each other in the axial direction and project from each other at intervals in the axial direction.
A fuel supply passage 19 communicating with a pressure chamber of a plunger barrel (not shown) protruding from the bottom surface of the mounting hole 3 of the injection pump body 2 is supplied with fuel through an opening 20 formed in the stopper T.
The pressure causes the piston pulp 11 to move rightward in the figure, so that the first inlet 1T is also supplied into the fuel supply passage 10.

In addition, the piston pulp 11 includes a pressure accumulation chamber 14 and a second
An L-shaped communication path 21 is formed that communicates the inlet 18 with the piston pulp 11.
moves to the right in the figure, the fuel supply passage 19 and the first inlet 11
The pressure accumulation chamber 14 and the second inlet port 18 are communicated with each other before the pressure accumulation chamber 14 and the second inlet port 18 are communicated with each other. The opening end of the communication path 21 toward the surface of the piston pulp 110 is formed in an annular groove 21a.

A plurality of third inlet ports 23 are bored at the right end of the pulp guide 6 to communicate the inside and outside of the pulp guide 6 and to connect the fuel supply passage 10 to the fuel supply passage 22 of the holder 4. The supply passage 22 is connected to the threaded portion 2 of the holder 4.
4 is connected to an injection nozzle (not shown) via an injection pipe (not shown) screwed onto the pipe. An axial fuel passage 25 is formed on the outer peripheral surface of the pressure regulating pulp 12, and when the pressure regulating pulp 12 moves to the left in the figure and opens the valve, the fuel supply passage 22 and the pressure regulating chamber 14 are brought into communication. It looks like this.

Next, the operation of the above-described embodiment will be explained with reference to FIGS. 2(a) to 2(h), which are simplified versions of FIG. 1.

FIG. 2 shows a pressure chamber 30 of the plunger barrel 26 communicating with the fuel supply passage 19, and a plunger 27 is slidably disposed within the plunger barrel 26. Further, a suction port 28 is formed on one side of the plunger barrel 26.

The plunger 27 has a fuel supply passage 19 and an intake port 2 when the plunger 2T moves forward to the maximum (rightward in the figure).
A communication path 29 is formed that communicates the two.

FIG. 2(a) shows the state before the plunger 27 is activated. Since the inlet 28 of the pressure chamber 3o is open, the pressure of the fuel acting on the piston pulp 11 is low. , the piston pulp 11 is positioned at the left end due to the elastic force of the spring 130 and closes the first introduction port 17. Also,
The pressure regulating pulp 12 is also located at the right end by the spring 13 and closes the pressure accumulating chamber 14.

FIG. 2(b) shows the initial state of operation of the plunger 27, in which the plunger 27 moves to the right and closes the suction port 2.
8 starts to increase the pressure of the fuel in the pressure chamber 30, and the piston pulp 11 starts moving to the right. Then, the pressure of the fuel sealed in the pressure accumulator 14 also rises, which prevents the piston pulp 11 from moving rapidly to the right. is not enough.

In FIG. 2(C), as the piston pulp 11 moves further to the right, the communication passage 21 is connected to the second introduction port 18.
The high-pressure fuel in the pressure accumulation chamber 14 is supplied to the fuel supply passage 10, from where it reaches an injection nozzle (not shown), and fuel injection begins.

Here, when the fuel in the pressure accumulation chamber 14 is supplied, the pressure in the pressure accumulation chamber 14 tends to drop by that amount, and the pressure of the fuel sent to the pressure chamber 30 also increases, causing the piston pulp 11 to rapidly move to the right. Then, the second introduction port 18 is opened significantly. As a result, a large amount of fuel in the pressure accumulator chamber 14 is pumped without pressure loss.

To improve the rise of fuel pressure that exceeds the valve opening pressure of an injection nozzle.

FIG. 2(d) shows the state during the pumping period. When the plunger 27 moves further to the right, the pressure in the pressure accumulation chamber 14 from which some fuel has been discharged is about to decrease, so the piston pulp 11 rapidly moves to the right and the first inlet 1
1 is wide open, and a large amount of high-pressure fuel in the pressure chamber 30 is supplied to the fuel supply passage 10 and the injection nozzle without pressure loss. Therefore, the fuel injection pressure also increases. At this time, at the end of the pressure feeding, the second inlet 18 closes and the pressure inside the pressure storage chamber 14 rises, so the movement of the piston pulp 11 to the right side is decelerated, and the stopper 1 of the pressure regulating pulp 12 of the piston pulp 11
6 is buffered.

FIG. 2(e) shows the state at the end of injection, in which the movement of the plunger 27 causes the communication passage 29 of the plunger 21 to open.
communicates with the suction port 28, and the pressure within the pressure chamber 30 drops rapidly. Therefore, the pressure of the fuel acting on the piston pulp 11 becomes weaker, and the piston valve 11 begins to return to the left due to the elastic force of the spring 130. At this time, injection from the injection nozzle also ends because the fuel pressure decreases.

FIG. 2(f) shows the state in which the plunger 27 is moved most to the right. Even in this state, the communication passage 29 and the suction port 28 are in communication, so the piston pulp 11 returns further to the left.

FIG. 2(g) shows a state in which the plunger 2T has finished its compression stroke and has begun to return, and as the piston pulp 11 moves further to the left, the piston pulp 11
The communication passage 21 is removed from the second introduction port 1B, and the pressure accumulation chamber 14 becomes sealed again, and the pressure within this pressure accumulation chamber 14 becomes lower than the pressure within the fuel supply passage 22 downstream of the piston pulp 11. Therefore, the pressure regulating valve 12 moves to the left against the elastic force of the spring 13 to open, thereby performing a fuel sucking back action in which fuel flows into the pressure accumulating chamber 14 from the fuel supply passage 22. When the pressures in the pressure storage chamber 14 and the fuel supply passage 22 become approximately equal, the pressure regulating pulp 12 closes as shown in FIG. 2(h), returning to the same state as in FIG. 2(a). In this way, the process described above is repeated.

Note that the compression coil spring 13 also acts to set the valve opening pressure of the piston pulp 11, but this pressure is mainly determined by the pressure in the "C" pressure accumulation chamber 14, and in reality, the compression coil spring 13 is Therefore, the valve opening pressure setting of the piston pulp 11 is based on the pressure inside the pressure accumulation chamber, that is, the piston pulp 11.
displacement, the bulk modulus of fuel (1,66X 10 Kl
The volume of the pressure accumulating chamber 14 may be determined by taking into account the required pressure. In addition, the return of the piston pulp 11 has the effect of sucking back fuel and preventing secondary injection, but if the amount of sucking back is too large, the pressure inside the injection tube and injection nozzle (not shown) will become negative. Since cavitation sometimes occurs, it is necessary to select a return amount of the piston pulp 11 that does not cause cavitation.

As described above, according to the present invention, fuel is first stored in the pressure accumulation chamber at a pressure higher than a predetermined value due to the pressure of the fuel pumped from the injection pump, and at the same time as the valve is opened, the valve opening area increases rapidly, and the high pressure and pressure are released from the pressure accumulation chamber. □Since a large amount of fuel is supplied to the injection nozzle and the valve opening area of the injection pump is rapidly increased to supply fuel to the injection nozzle, the valve opening area is rapidly increased by the first and second pulps. By reducing pressure loss, fuel injection pressure can be increased. Therefore, the atomization characteristics of the fuel injected from the injection nozzle are improved, combustion is improved, fuel efficiency is improved, and exhaust properties such as smoke and unburned component emissions can be improved.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view of a piston valve unit showing an embodiment of the fuel injection device according to the present invention, and FIG.
b), (c), (d), (e), (f
), (g), and (h) are explanatory diagrams showing one operating state of FIG. 1. 1...Piston Pulp Units) 10,19,2
2... Fuel supply passage 11... Piston knob 12... Pressure regulating pulp 13... Compression coil spring 1
4...Pressure accumulation chamber 17,18.23...Inlet 21
...Communication path 21...Plunger 30...
Pressure chamber patent applicant Nissan Motor Co., Ltd. Agent Patent attorney Fujio Sasashima Figure 1 Figure 2 (a) Figure 2 (C)

Claims (1)

[Claims] In a fuel injection device whose valve is opened by the pressure of fuel pumped by a plunger of a fuel injection pump and fuel is injected from an injection nozzle, the fuel injection passage communicates with the fuel supply passage from the injection pump to the injection nozzle via an inlet. a pressure accumulating chamber; the pressure accumulating chamber has a pressure receiving surface on one side and a pressure receiving surface facing the fuel supply passage on the opposite side, and is displaced according to the pressure balance acting on both pressure receiving surfaces so that the fuel supply passage and A first valve element that opens and closes the inlet, and a temperature of the fuel downstream of the first valve element depending on the pressure in the pressure accumulator chamber and the opposing fuel pressure in the fuel supply passage downstream of the first valve element. a second valve body that opens and closes communication between the supply passage and the pressure accumulation chamber;
A fuel injection device, wherein the first valve body is configured to open the mlJ inlet in response to an increase in the pressure of the fuel pumped from the injection pump before opening the fuel supply passage.