JPS6213771A - Fuel injection equipment of diesel engine - Google Patents

Abstract

PURPOSE:To obtain a high injection rate at a low load and to reduce noise by reducing the injection rate at a small load, by providing a fuel trap volume portion capable of communicating with a high pressure fuel passage and controlling the communication by a switching valve. CONSTITUTION:When an electromagnetic coil 28 is not excited, a spool valve 25 is moved toward the left by a spring 26 for closing communicating passages 21, 22 so that a high pressure fuel passage 9 does not communicate with a fuel trap area portion 20 to obtain a high injection rate at a large load. On the other hand, when the electromagnetic coil 28 is excited at a small load such as at idling or the like, the spool valve 25 is moved toward the right against the spring 26 by attraction of a movable piece 27 for opening the passages 21, 22 so that the high pressure fuel passage 9 communicates with a fuel trap volume portion 20. As a result, a substantial volume of the fuel trap of high pressure fuel passages 9-11 are enlarged, whereby an increase in fuel pressure is kept at a low level to reduce an injection ratio for effecting quiet combusting operation.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an improvement of a fuel injection device for a diesel engine.
In particular, it relates to improvements to reduce noise at low loads such as when idling.

(Prior Art) As a conventional fuel injection device, there is, for example, one shown in FIG. 4. This is a detailed diagram of the fuel injection nozzle of the fuel injection device, and it will be explained as follows.
A needle valve 2 is slidably housed within the nozzle tip 1, and is biased by a spring 3 via a retainer 4 in a direction to close the nozzle hole 5 at the tip of the nozzle tip 1. High-pressure fuel from the fuel injection pump 18 enters the fuel introduction lower of the spring holder 6 through a high-pressure fuel passage 19 formed by a fuel tube, and passes through the spring holder 6, the regulation plate 8 that defines the maximum lift +1 of the needle valve 2, and the nozzle tip. The fuel is led to a fuel reservoir 12 in the nozzle tip 1 through high-pressure fuel passages 9, 10[deg.] 11 formed in series in the nozzle tip 1. Then, when the pressure in the fuel reservoir 12 rises and the force applied to the pressure stage 13 provided on the needle valve 2 overcomes the biasing force of the spring 3, the needle valve 2 moves upward in the figure and the nozzle hole 5 opens. It is opened and fuel is injected into a combustion chamber (not shown). Further, leaked fuel from the sliding portion between the needle valve 2 and the nozzle tip 1 is returned to the fuel tank from the return port 15 via the return passage 14. In addition, nozzle tip 1. The regulating plate 8 and the spring holder 6 are integrated by a holder 16. 17 is a shim for adjusting the spring force (Utility Model No. 58-9847)
(See Publication No. 0).

<Problems to be Solved by the Invention> However, in such a conventional fuel injection device, the high pressure fuel passage 19. Since the fuel trap volume in 9.10.11 was fixed and could not be changed, in order to ensure a high level of injection pressure in the high load range, the influence of the high pressure level on the trap volume was It is necessary to reduce the trap volume of the nozzle part, which is larger than that of the other parts, and for this reason, in the low load range where a low injection rate is required, especially at idle, the injection rate is too high and the ignition delay period There is a problem in that the amount of injected fuel increases, resulting in an increase in noise, which is important in terms of product performance.

The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a fuel injection device for a diesel engine that can change the fuel trap volume of a high-pressure fuel passage depending on operating conditions. shall be.

Means for Solving the Problems〉 In order to achieve the above objects, the present invention is directed to high pressure twisting)
A fuel trap volume portion communicating with the fuel passage through a communication passage is provided, and an on-off valve for controlling opening and closing of the communication passage is provided.

In the above configuration, by opening and closing the communication passage using the on-off valve, when the communication passage is opened, the fuel trap volume is added to substantially increase the fuel trap volume of the high-pressure fuel passage, thereby making it possible to lower the injection rate. When closed, a high injection rate can be achieved by reducing the fuel trap volume of the high pressure fuel passage.

<Example> An example of the present invention will be described below with reference to FIGS. 1 and 2. However, in this embodiment, the same elements as those in the conventional example (FIG. 4) are given the same reference numerals and explanations are omitted, and different elements will be explained.

A fuel trap volume 20 is provided within the spring holder 6 and communicates with the high pressure fuel passage 9 within the spring holder 6 by a communication passage 21,22. Note that this fuel trap volume portion 20 has a shoulder portion 23.
The air is sealed by a blind plug 24, which is sealed by a plug 24, and air is vented by loosening the blind plug 24.

A spool valve 25 as an on-off valve is provided between the communication passages 21 and 22, and the spool valve 25 is biased to a position where the communication passages 21 and 22 are blocked by a spring 26 acting on one end. A tapered movable piece 27 is connected to the other end of the spool valve 25, and this movable piece 27 is surrounded by a tapered electromagnetic coil 28.

29 is a lead wire to the electromagnetic coil 28, and 30.31 is a communication path that communicates the space at both ends of the spool valve 25 with the fuel trap volume 20. Here, by supplying current to the electromagnetic coil 28, the electromagnetic coil 28 causes the movable piece 2 to
7 is suctioned to displace the spool valve 25 to the right in the figure against the spring 26, thereby allowing the communication passages 21 and 22 to communicate with each other.

Note that 32 is a connector for connecting a high-pressure fuel conduit attached to the fuel introduction lower, and 33 is a connector for connecting a return conduit attached to the return port 15.

Next, the effect will be explained.

When no current is supplied to the electromagnetic coil 28, the spool valve 25 is moved by the spring 26 as shown (to the left), and the communication passages 21, 22 are cut off, i.e., the communication between the high-pressure fuel passage 9 and the fuel trap volume 20 is closed. As a result, the fuel trap volume in the high-pressure fuel passage 9, 10, and 11 is kept small as before, resulting in a high injection rate. The characteristic is A. Therefore, by stopping the supply of current to the electromagnetic coil 28 during high loads, the output during high loads can be ensured.

Furthermore, when current is supplied to the electromagnetic coil 28, the movable piece 27 is attracted by the tm coil 28, and the spool valve 25 moves to the right in the figure against the spring 26. is opened, placing high pressure fuel passage 9 and fuel trap volume 20 in communication.

For this reason, the effective fuel trap volume of the high-pressure fuel passage 9.10.11 becomes large, and the increase in fuel pressure is suppressed, thereby reducing the injection rate and suppressing the amount of fuel injected during the ignition delay period. As a result, the rise in cylinder pressure becomes gradual, and quiet combustion operation can be achieved. That is, FIG. 3 (() l (U).

(c) becomes the characteristic of B. Therefore, by supplying current to the electromagnetic coil 28 during low load times such as when idling, noise can be reduced.

As a means for detecting the load, it is preferable to provide a sensor consisting of a potentiometer on the control lever of the fuel injection pump, and supply current to the electromagnetic coil when the load is below a predetermined value.

Further, it is preferable that the communication passage and the fuel trap volume are provided as close as possible to the injection hole of the fuel injection nozzle.

Because the peak pressure of the fuel pressure in the high-pressure fuel passage is
Due to the reflection of pressure waves at the seat of the needle valve provided near the nozzle hole of the fuel injection nozzle, the pressure wave becomes higher near the nozzle hole. Therefore, by providing the fuel trap volume at a location where this peak pressure is high, pressure energy, particularly pressure energy at the initial stage of injection, can be effectively reduced. If the pressure energy at the beginning of injection is low, the initial injection rate can be reduced.

<Effects of the Invention> As explained above, according to the present invention, a fuel trap volume portion that can communicate with the high-pressure fuel passage is provided, and the communication is controlled by an on-off valve, so that the fuel trap volume of the high-pressure fuel passage can be reduced. It can be made variable, and at high loads that require a high injection rate, the communication is cut off to obtain a high injection rate with the same small fuel trap volume as before, and conversely, at low loads, especially when idling, it is opened and the fuel is The effect is that it becomes possible to increase the trap volume and reduce the injection rate to reduce noise.

[Brief explanation of drawings]

1 is a sectional view of a fuel injection device showing an embodiment of the present invention, FIG.
) and (c) are characteristic diagrams of high-pressure fuel passage internal pressure, injection rate, and cylinder pressure with respect to crank angle, and FIG. 4 is a sectional view of a conventional fuel injection device. 2... Needle valve 5... Nozzle hole 9.10.11.1
9... High pressure fuel passage 12... Fuel reservoir 2
0...Fuel trap volume part 21.22...Communication path 25...Spool valve 27...Movable piece
28...Electromagnetic coil patent applicant Nissan Motor Co., Ltd. agent Patent attorney Fujio SasashimaFigure 3 Crank angleCrank angle

Claims (1)

[Claims] 1. A fuel injection device for a diesel engine, comprising: a fuel trap volume communicating with a high-pressure fuel passage via a communication passage; and an on-off valve for controlling opening/closing of the communication passage.