JPH0432227B2 - - Google Patents

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 injection nozzle and the pressure oil chamber of the plunger barrel that houses the plunger, and the delivery valve is opened by the rise in fuel pressure caused by sliding of the plunger. A configuration in which fuel is supplied to an injection nozzle and the fuel is injected into a combustion chamber from the injection nozzle is well known. (Refer to page 65 of the technical manual "Diesel Engine" published by Nissan Motor Co., Ltd., June 1978) By the way, for example, fuel for direct injection diesel engines, especially small engines with one cylinder of 3 to 500 c.c. The higher the injection pressure is at 1000 atm or higher, the better the atomization properties of the fuel, the better the mixture of air and fuel, the better the fuel efficiency, the lower smoke, NOx, and HC emissions, and the weaker the swirl. It is known that improved combustion can be expected.

Regarding such an increase in fuel injection pressure, according to the conventional system described above, fuel injection from the injection nozzle begins only when the pressure of the fuel pumped through the delivery valve becomes equal to or higher than the injection nozzle opening pressure. A sufficiently high injection pressure could not be obtained unless the fuel pumping speed was extremely high. In order to solve this problem, it may seem like increasing the valve opening setting load of the valve spring, but in this case, even if the valve opening pressure can be increased, it does not necessarily mean that the injection pressure will increase. It is something that cannot be done. That is, the larger the set load of the spring, the smaller the valve opening lift, in addition to the fact that the fuel pressure after the valve is opened goes around to the back of the delivery valve to act in the closing direction of the delivery valve. For this reason, the pressure loss of the delivery valve increases and the injection pressure also decreases.

In order to prevent this, it is necessary to increase the fuel pumping speed as described above or to increase the plunger speed by devising a cam shape.However, due to the special cam shape, the wear of the cam surface increases, making it impractical. A problem arises in which there is a lack of It is also possible to increase the injection pressure by increasing the opening pressure of the injection nozzle, but in this case it is necessary to significantly increase the spring force of the injection nozzle, and as a result, secondary injection is more likely to occur. There is a problem that the injection nozzle 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.

For this purpose, the present invention specifically provides a fuel injection device in which a 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. A fuel supply pressure regulating device that is installed in a fuel supply passage leading to the fuel supply passage and adjusts the fuel supply pressure, the device moves in response to an increase in the pressure of the fuel pumped from the injection pump, and moves at a predetermined position to adjust the fuel supply pressure on the upstream side. A pressure accumulation chamber is formed between a first valve body that communicates the passage with a fuel supply passage on the downstream side, and a first valve body located downstream of the first valve body;
a second valve that opens and closes communication between the fuel supply passage downstream of the first valve body and the pressure accumulation chamber according to the pressure in the pressure accumulation chamber and the opposing fuel pressure in the fuel supply passage downstream of the first valve body; a valve body;
a communication passage that communicates the pressure accumulation chamber with the downstream fuel supply passage before communicating the upstream fuel supply passage with the downstream fuel supply passage according to an increase in the pressure of the fuel in the valve body; was formed and configured.

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

FIG. 1 shows a piston valve unit corresponding to a conventional delivery valve used in the fuel injection device of the present invention. The piston valve 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 valve guide 6 are disposed within the holder 4. They are arranged in a connected direction. The flange 5a at one end of the cylinder 5 is held between the tip of the holder 4 and a stopper 7 attached to the innermost part of the mounting hole 3, and the valve guide 6 abuts against the step 8 of the holder 4. It is supported and fixed by a spacer 9. A groove is provided in the axial direction of the inner peripheral surface of the holder 4 to form a fuel supply passage 10.
is formed.

A piston valve (first valve body) 11 is slidably disposed within the cylinder 5, and a pressure regulating valve (second valve body) is disposed within the valve guide 6.
12 are slidably disposed. A compression coil spring 13 is interposed between the piston valve 11 and the pressure regulating valve 12, and the pressure accumulation chamber 14
is formed. The piston valve 11 normally comes into contact with the stopper 7 and stops, and the valve body portion 15 provided on the pressure regulating valve 12 is
The end portion of the valve guide 6 is in contact with the valve seat. 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 inlet ports 17 and a plurality of second inlet ports 18 which are spaced apart in the axial direction and project from each other at intervals in the axial direction. Fuel from a fuel supply passage 19 communicating with a pressure chamber of a plunger barrel (not shown) protruding from the bottom of the mounting hole 3 passes through an opening 20 formed in the stopper 7, and the pressure causes the piston valve 11 to move. The fuel is moved to the right in the figure, and is supplied into the fuel supply passage 10 from the first introduction port 17.

Further, the piston valve 11 is formed with an L-shaped communication passage 21 that communicates the pressure accumulation chamber 14 and the second inlet 18, and this communication passage 21 is formed when the piston valve 11 moves to the right in the figure. , the pressure accumulation chamber 14 and the second introduction port 18 are communicated with each other before the fuel supply passage 19 and the first introduction port 17 are communicated with each other. In addition, the piston valve 1 of the communication passage 21
The opening end to the peripheral surface of 1 is formed in an annular groove 21a.

A plurality of third inlet ports 23 are bored in the right end portion of the valve guide 6 to communicate the inside and outside of the valve guide 6 and to connect the fuel supply passage 10 to the fuel supply passage 22 of the holder 4. The supply passage 22 communicates with an injection nozzle (not shown) via an injection pipe (not shown) screwed onto a threaded portion 24 of the holder 4 . Pressure regulating valve 12
An axial fuel passage 25 is formed on the outer circumferential surface of the pressure regulating valve 12, and the fuel supply passage 22 and the pressure regulating chamber 14 are communicated with each other when the pressure regulating valve 12 moves to the left in the figure and opens. There is.

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

FIG. 2 shows a pressure chamber 30 of the plunger barrel 26 that communicates with the fuel supply passage 19, and a plunger 27 is located inside the plunger barrel 26.
are slidably arranged. Further, a suction port 28 is formed on one side of the plunger barrel 26.
The plunger 27 is formed with a communication passage 29 that communicates with the fuel supply passage 19 and the suction port 28 when the plunger 27 moves forward to the maximum extent (to the right in the figure).

FIG. 2a shows the state before the plunger 27 is activated. Since the suction port 28 of the pressure chamber 30 is open, the pressure of the fuel acting on the piston valve 11 is low, and therefore the piston valve 11
Due to the elastic force of the spring 13, it is located at the left end and closes the first introduction port 17. Further, the pressure regulating valve 12 is also positioned at the right end by the spring 13 to close the pressure accumulating chamber 14.

FIG. 2b shows the initial state of operation of the plunger 27. When the plunger 27 moves to the right and closes the intake port 28, the pressure of the fuel in the pressure chamber 30 begins to rise, and the piston valve 11 moves to the right. Start moving to. Then, the pressure of the fuel sealed in the pressure accumulation chamber 14 also increases, which prevents the piston valve 11 from moving rapidly to the right. Therefore, at this stage, the first inlet port 17 is opened. It doesn't reach that point.

In FIG. 2c, the piston valve 11 moves further to the right, so that the communication passage 21 opens into the second
The fuel in the pressure accumulation chamber 14, which is in communication with the inlet 18 and has reached a high pressure, is supplied to the fuel supply passage 10, from which it reaches an injection nozzle (not shown), and fuel injection begins. Here, when the fuel in the pressure accumulator 14 is supplied, the pressure in the pressure accumulator 14 tends to decrease by that amount, and together with the increase in the fuel pressure sent from the pressure chamber 30, the piston valve 11 moves rapidly 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, and the fuel pressure rises well above the valve opening pressure of the injection nozzle.

FIG. 2d shows the state during the pumping stage. When the plunger 27 moves further to the right, the pressure in the pressure accumulation chamber 14 from which some fuel has been discharged tends to decrease, so the piston valve 11 rapidly moves to the right, widening the first inlet 17, and increasing the pressure in the pressure chamber 30. The high-pressure fuel inside the fuel supply passage 1 is supplied without pressure loss.
A large amount of water is supplied from 0 to the injection nozzle. Therefore,
Fuel injection pressure also increases. At this time, the second inlet port 18 closes at the end of the pressure feeding and the pressure in the pressure accumulation chamber 14 rises again, so the movement of the piston valve 11 to the right side is decelerated, and the pressure regulating valve 1 of the piston valve 11 is decelerated.
2 to the stopper 16 is damped.

FIG. 2e shows the state at the end of injection, in which the plunger 27 moves due to the movement of the plunger 27.
The communication passage 29 communicates with the suction port 28, and the pressure chamber 30
The pressure inside drops rapidly. Therefore, the pressure of the fuel acting on the piston valve 11 becomes weaker, and the piston valve 11 begins to return to the left due to the elastic force of the spring 13. At this time, injection from the injection nozzle also ends because the fuel pressure decreases.

FIG.
Since the piston valve 9 and the suction port 28 are in communication, the piston valve 11 returns further to the left.

FIG. 2g shows a state in which the plunger 27 has completed its compression stroke and has begun to return, and as this occurs, the piston valve 11 moves further to the left, so that the communication passage 21 of the piston valve 11 is connected to the second inlet port 18.
The pressure accumulating chamber 14 becomes sealed again, and the pressure within the accumulating chamber 14 becomes lower than the pressure within the fuel supply passage 22 downstream of the piston valve 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 suction action in which fuel flows into the pressure accumulating chamber 14 from the fuel supply passage 22. Then, the pressure accumulation chamber 14 and the fuel supply passage 22
When the pressures become almost equal, the pressure regulating valve 12 closes as shown in FIG. 2h, returning to the same state as in FIG. 2a. In this way, the process described above is repeated.

Although the compression coil spring 13 also acts to set the opening pressure of the piston valve 11, this pressure is mainly determined by the pressure in the pressure accumulation chamber 14, and the compression coil spring 13 is not substantially required. Therefore, the opening pressure of the piston valve 11 is set by considering the pressure inside the pressure accumulation chamber, that is, the amount of movement of the piston valve 11, the bulk modulus of fuel (approximately 1.66×10 ⁴ Kg/cm ² ), and the required pressure. What is necessary is to determine the volume of the pressure accumulation chamber 14. In addition, the return of the piston valve 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 nozzle and the injection nozzle (not shown) will become negative pressure. Therefore, it is necessary to select a return amount of the piston valve 11 that does not cause cavitation.

As described above, according to the present invention, fuel with a pressure higher than a predetermined value is first stored in the pressure accumulation chamber by the pressure of the fuel pumped from the injection pump, and at the same time as the valve is opened, the valve opening area is rapidly increased and the high pressure and A large amount of fuel is supplied to the injection nozzle, and following this, the valve opening area of the injection pump is rapidly increased to supply the injection nozzle, so the first and second valves rapidly increase the valve opening area and pressure is increased. By reducing losses,
Fuel injection pressure can be increased. As a result, 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 drawings]

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. 2 a, b, c, d, e, f, g, and h show the operating state of Fig. 1. FIG. 1... Piston valve unit, 10, 19,
22... Fuel supply passage, 11... Piston valve, 12... Pressure regulating valve, 13... Compression coil spring, 14... Pressure accumulation chamber, 17, 18, 23... Inlet, 21... Communication path, 27 ...Pranja, 30
...Pressure chamber.

Claims (1)

[Claims] 1 In a fuel injection device that opens a valve under the pressure of fuel pumped by a plunger of a fuel injection pump and injects fuel from an injection nozzle, the fuel injection device is installed in a fuel supply passage leading from the injection pump to the injection nozzle to supply fuel. A fuel supply pressure regulating device for regulating pressure, which moves in response to an increase in the pressure of the fuel pumped from the injection pump and communicates the upstream fuel supply passage with the downstream fuel supply passage at a predetermined position. A pressure accumulation chamber is formed between the first valve body and the first valve body located on the downstream side of the first valve body, and the pressure in the pressure accumulation chamber and the first valve are opposed to the pressure in the pressure accumulation chamber. 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 pressure accumulation chamber and the downstream fuel supply passage are communicated with the first valve body before the upstream fuel supply passage and the downstream fuel supply passage are communicated with each other according to an increase in the pressure of the fuel. What is claimed is: 1. A fuel injection device characterized in that the fuel injection device is configured by forming a communication path for causing