JPS61277868A - Fuel injection device - Google Patents

Abstract

PURPOSE:To prevent the occurrence of surging in a middle and a high rotation range and to decrease the generation of noise during idle running, by providing a switching valve which selectively opens and closes two or more fuel passages different in an inner size. CONSTITUTION:Fuel in a pressure chamber 16 is fed with a pressure to a first injection steel pipe 23, having a small passage 24, through a first distribution passage 21 and a first delivery valve 22 through forward movement of a plunger 14, or is fed with a pressure to a second injection steel pipe 33, having a large passage 34, through a second distribution passage 31 and a second delivery valve 32. The first and second injection steel pipes 23 and 33 join each other and are coupled to an injection nozzle 17. When the number of revolutions of an engine is low, a solenoid is energized, and a switching valve 51 releases the first distributing passage 21 and the first injection steel pipe 23, and blocks the second distribution passage 31 and the second injection steel pipe 33. When the number of revolutions of the engine is high, the solenoid is prevented from energization, and its actuation is reversed to that at a time when the number of revolutions of an engine is low.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates in particular to a fuel injection device for supplying fuel to a diesel engine.

[Conventional technology and problems]

Ideally, the specifications of the fuel injection device, such as the valve opening pressure of the injection nozzle or the injection steel pipe, are determined to satisfy all engine performance from idle operation to full load operation. However, in reality, during idling operation, noise is likely to be generated due to combustion shock called idle knock, and at medium to high speeds, the injection rate decreases once and then increases again, that is, the graph curve of the injection rate becomes 2.
A phenomenon called "piling" may occur, which causes the engine to surge, which worsens the driving sensation.

In order to prevent the above-mentioned idle knock, it is effective to perform so-called pilot injection, in which the graph curve of the injection rate becomes two peaks4, but for this purpose, it is necessary to provide a valve that operates at high speed. , it is difficult to realize pilot injection. On the other hand, the rotational speed at which the double peak phenomenon of the injection rate occurs at medium and high speeds is proportional to the square of the inner diameter of the injection steel pipe, so by reducing this inner diameter, the double peak phenomenon of the injection rate can occur in the idle speed range. be able to.

That is, it becomes possible to perform injection substantially the same as pylon injection during idling operation. However, when the inner diameter of the injection steel pipe is reduced in this way, the pipe resistance increases in the middle and high rotation range, the fuel injection amount decreases, and the injection period becomes longer, resulting in a decrease in engine performance.

In view of the above points, the present invention has been made with the object of preventing surging in the mid-to-high rotation range, improving driving sensation, and reducing noise during idling operation.

[Means for solving problems]

In the fuel injection device according to the present invention, the fuel passage formed between the fuel injection pump and the injection nozzle is composed of two or more passages having different inner diameters, and a switching valve is provided to selectively open and close these passages. This switching valve is equipped with
When the engine speed is below a predetermined value, the small diameter passage is opened, and when the engine rotation speed is greater than the predetermined value, the large diameter passage is opened.

〔Example〕

The present invention will be explained below with reference to illustrated embodiments.

FIG. 1 shows a distribution type fuel injection pump and an injection nozzle, in which a feed pump 11 is rotationally driven by a drive shaft 12.
Liquid fuel flowing from the direction of arrow A is supplied into the fuel chamber 13. The plunger 14 is rotatable around its axis and moves forward and backward in the axial direction, sucking the fuel in the fuel chamber 13 into the pressure chamber 16 through the inlet passage 15. As will be described later, there are two routes from the pressure chamber 16 to the injection nozzle 17, and these routes can be selectively switched. That is, as the plunger 14 moves forward, the fuel in the pressure chamber 16 is forced into the first injection steel pipe 23 via the first distribution passage 21 and the first delivery valve 22, or through the second distribution passage 31 and the second delivery valve 22. It is force-fed to the second injection steel pipe 33 via the delivery valve 32. first and second injection steel pipes 23,
33 merge and are connected to the injection nozzle 17. Therefore, the fuel pumped through the first or second injection steel pipes 23 and 33 is guided to the injection nozzle 17 and
The valve opens depending on the fuel pressure and fuel injection is performed.

The plunger 14 is rotationally driven by the drive shaft 12, and moves forward and backward as a face cam 41 provided at the base engages with a roller 42. In other words, r2. The timing of fuel injection is determined by the engagement between the face cam 41 and the roller 42, and the timing (7) is controlled by displacing the timer piston 43 to change the position of the roller 42.

The timer piston 43 receives the fuel pressure in the fuel chamber 13 at its end face, and is displaced in accordance with this fuel pressure.

In order to prevent the fuel pressure in the fuel chamber 13 from becoming excessive,
A pressure regulating valve 45 is provided in the middle of the discharge passage 44 of the feed pump 11, and an overflow valve 46 is provided above the fuel chamber 13. When the discharge pressure of the fuel increases as the rotational speed of the feed pump 11 increases, the excess fuel opens the pressure regulating valve 45 and flows back to the suction passage 47 side of the feed pump 11, and further flows into the fuel chamber 13. If the fuel pressure is too high, excess fuel will be discharged from this distribution fuel injection pump via the overflow valve 46 and will flow back to the suction side of the feed pump 11 in accordance with the assumption &5AA.

Now, as shown in FIGS. 2 and 3, the annular switching valve 51 is disposed around the plunger 14 and connects one of the distribution passages 21 and 31 to the distribution port 52 of the plunger 14, as will be described later. to enable communication. In other words, the switching valve 51 is rotatably fitted into an outer circumferential groove 55 of a cylinder 54 inserted into a hole in a distribution head 53 of the present fuel injection device, and has notches formed at equal intervals in the circumferential direction of the switching valve 51. 56 constantly communicates with a communication hole 57 bored in the cylinder 54, and also communicates with the first and second distribution passages 21, 31.
It is designed to selectively communicate with one of the two.

The plunger 14 rotates around the axis within the cylinder 54 and reciprocates along the axis, and the communication hole 57 is
As the plunger 14 rotates about its axis, it periodically faces the distribution port 52 and communicates with the pressure chamber 16 via the distribution port 52 .

A lever 58 extending radially from the outer circumferential surface of the switching valve 51 is
It projects to the outside of the dispensing head 53 through an opening 59 formed in the housing 53 . The rod 0 connected to the protruding end of the lever 58 is fitted into a hole in the shaft center of a solenoid 61 attached to the lower surface of the distribution head 53, and is biased by a spring 62 in the direction of protruding from the solenoid 61. When the solenoid 61 is energized, the rod 60 is pulled toward the solenoid 61 against the spring 62 by the electromagnetic force generated in the solenoid 61, and this causes the switching valve 51 to rotate clockwise in the figure and move to the first position. The distribution passage 21 is communicated with the communication hole 57. On the other hand, when the power supply to the solenoid 61 is cut off, the rod 60 is pressed by the spring 62 and protrudes from the solenoid 61, whereby the switching valve 51 is rotated counterclockwise and the second distribution passage 31 is connected to the communication hole. 57.

The first injection steel pipe 23 connected to the first distribution passage 21 has a small diameter passage 24, and the second injection pipe 23 has a small diameter passage 24 connected to the first distribution passage 31.
The injection steel tube 32 has a large diameter passage 34 (FIG. 1). When the engine speed is -low, the solenoid 61 is energized, and the switching valve 51 opens the first distribution passage 21 and the first injection steel pipe 23, and also opens the second distribution passage 31 and the second injection steel pipe 3.
Block 3. When the engine speed is high, the solenoid 61 is not energized and the switching valve 51 is closed to the second distribution passage 31 and the second
The injection steel pipe 33 is opened, and the first distribution passage 21 and the first injection steel pipe 23 are closed.

The device of this embodiment operates as follows.

The fuel in the pressure chamber 16 is pressurized by the advance of the plunger 14, flows from the distribution boat 52 to the communication hole 57, passes through the notch 54 of the switching valve 51, and communicates with the notch 54 of the distribution passages 21 and 31. It flows into the passage of the person who is there. This fuel pushes open the delivery valve 22 or 32 and reaches the injection nozzle 17 via the injection steel pipe 23 or 33. When the pressure inside the injection nozzle 17 becomes equal to or higher than the valve opening pressure, the injection nozzle 17 opens and performs fuel injection.

Now, the selection valve 5 determines which of the first and second injection steel pipes 23 and 33 the fuel is supplied to the injection nozzle 17 through.
1, that is, whether or not the solenoid 61 is energized. This energization is performed depending on the operating conditions of the engine, and is performed only when the engine is idling, for example. That is, at low speeds, fuel is forced to the injection 1:1 nozzle 17 through the injection steel pipe 23 having the small diameter passage 24, and at high speed, fuel is forced to the injection nozzle 17 through the injection steel pipe 33 having the large diameter passage 34. be done.

Here, opening of the injection nozzle 17 will be explained.

The pressure waves of the fuel discharged from the injection pump reach the injection nozzle 17 at the speed of sound. When the diameter of the injection steel pipe is large, the fuel pressure is low at low speeds, the nozzle 17 does not open, and pressure waves are reflected. This reflected pressure wave is pressurized again on the pump side and returns to the nozzle 17 as a higher pressure wave.
Reach the side. Therefore, the pressure in the 17 nozzles increases stepwise, and when this pressure exceeds the valve opening pressure of the nozzle 17,
The nozzle 17 is opened to perform fuel injection. When the engine speed further increases, the first pressure wave that reaches the nozzle 17 first becomes larger, and the valve opens earlier. However, at this time, the plunger 14 is not pumping a sufficient amount of fuel, so the pressure drops significantly when the valve opens, and the injection amount suddenly decreases temporarily, but then the injection amount increases again due to the arrival of the pressure wave of the flame. . In other words, a phenomenon in which the injection rate becomes two peaks is observed. If the engine is operated in such a rotational speed range, control of the fuel injection amount becomes unstable, causing surging and the like.

In this embodiment, during low rotation, fuel is pumped through the north first injection steel pipe 23 having a small-diameter passage 24. Therefore, the phenomenon where the injection rate becomes two peaks appears in the low speed range, and substantially the same injection as the pilot injection is performed, making it possible to reduce combustion noise at low speeds. Pilot injection involves injecting a small amount of fuel before the main injection to create a so-called scallop, which reduces the ignition of the main injection and reduces the noise and vibration at idle, which are problems with diesel engines. However, in this embodiment, as mentioned above, it is possible to perform injection similar to pilot injection by utilizing the characteristics of the pressure increase in the injection steel pipe.In addition, in this embodiment, it is possible to perform injection similar to pilot injection During operation, the second injection steel pipe 33 having the large-diameter passage 34 is opened via the switching valve 51, and fuel is pumped through the second injection steel pipe 33. It is possible to prevent a phenomenon in which the injection rate sometimes becomes two peaks, making it possible to stabilize the control of the fuel injection amount and to sufficiently increase the output.

Here, if the inner diameter of the injection steel pipe is d, and the rotational speed when the injection rate becomes two peaks is N, then the idle rotational speed N
In order to generate the pilot injection in step 2, the inner diameter dz of the injection steel pipe may be set as (Nz/lI/2d), and by determining the diameter of the injection steel pipe in this way, noise during idling operation can be reduced.

In the first embodiment, the switching valve 51 is controlled via the solenoid 61, but instead of this, it may be controlled using a hydraulic actuator, a hydraulic pump, or other hydraulic device. .

FIG. 4 shows a second embodiment. A bore 71 is formed below the plunger 14 of the distribution head 53 and is parallel to the plunger 14 and has one end facing the fuel chamber 13. A spool valve 72, that is, a switching valve is slidably fitted into the bore 71. will be combined. The bore 71 communicates with the distribution boat 52 of the plunger 14 through a communication hole 73, and also communicates with the first and second distribution boats 52 of the plunger 14.
It communicates with the distribution passages 21 and 31. The spool valve 72 is
It has an annular groove 74 on the outer circumferential surface, and this annular groove 74 always faces the communication hole 73 and is connected to the first and second distribution passages 21.
, 31 selectively.

Therefore, when the annular groove 74 faces the first distribution passage 21,
The pressure chamber 16 located at the tip of the plunger 14 is connected to the first
The annular groove 74 can communicate with the distribution passage 21, and the annular groove 74 can communicate with the distribution passage 21.
When facing the distribution passage 31, the pressure chamber 16 is connected to the distribution boat 52.
, a communication hole 73 , and an annular groove 74 .

A spring 75 is provided between the right end wall of the bore 71 and the spool valve 72, and the other end of the spool valve 74 faces into the fuel chamber 13. Therefore, the spool valve 72 is located at a position where the pressure within the fuel chamber 13 and the elastic force of the spring 75 are balanced, and depending on the magnitude of these pressures and elastic forces, the annular groove 74 is connected to the first and second distribution passages. 21, 31. The pressure within the fuel chamber 13, that is, the pump internal pressure, increases in proportion to the pump rotation speed, as shown in FIG.

Therefore, if the elastic force of the spring 75 is set so that the communication relationship between the distribution passages 21, 31 and the annular groove 74 is switched when the pump rotation speed is higher than a predetermined rotation speed, the injection steel pipe can be switched. I can do it.

The other configurations and operations are the same as those in the first embodiment, so their explanations will be omitted.

In the second embodiment, a spool valve 72, that is, a switching valve, is provided for each cylinder, but one switching valve is commonly used for each cylinder, and the pressure in the fuel chamber 13 is used to control all cylinders. The injection steel pipe may be switched at the same time.

FIG. 6 shows a third embodiment. This embodiment differs from the first and second embodiments in that the switching valve is provided outside the distribution head 53. That is, a spool valve 82, which is a switching valve, is slidably provided in a valve housing 81 disposed outside the distribution head 53, and a spring 83 is installed between the top surface of the spool valve 82 and the earthen wall of the housing 81. is provided. The rod 84 is connected to a control section (not shown) and connects the hole 85 of the valve housing 81 to the W! and comes into contact with the lower surface of the spool valve 82. A connecting pipe 86 extending from the distribution head 52 and injection steel pipes 23 and 33 are connected to the valve housing °81, and an annular groove 87 formed on the outer peripheral surface of the spool valve 82 constantly communicates with the connecting pipe 86, and It selectively communicates with one of the second injection steel pipes 23 and 33.

On the other hand, a distribution passage 25 that can communicate with the distribution boat 52 of the plunger 14 is formed in the distribution head 53, and this distribution passage 25 is connected to a connecting pipe 86 via a delivery valve 26. Thus, when the annular groove 87 communicates with the first injection steel pipe 23 , the fuel discharged from the pressure chamber 16 to the distribution passage 25 via the distribution boat 52 due to the advance of the plunger 14 passes through the delivery valve 26 and passes through the connecting pipe 86 . The fuel is then pumped through the annular groove 87 to the first injection steel pipe 23 . Further, when the annular groove 87 communicates with the second outer injection steel pipe 33, the fuel discharged from the pressure chamber 1 (1) is in the annular shape from the second injection steel pipe 33.
is pumped to.

Switching of the plunger 14 is performed by a control section via the rod 84, but this control section may be electrical with a solenoid, or may be one using hydraulic pressure or the like.

Other configurations and operations are similar to those of the first and second embodiments.

FIG. 7 shows the connection structure of the first and second injection steel pipes 23 and 33. a first connected to the dispensing head 53;
and the second injection steel pipes 23 and 33 merge on the downstream side,
A shuttle valve 91 is provided at the merging portion. The shuttle valve 91 consists of a valve bousing 92 and a ball 93.
A pulp chamber 94 that is formed within the valve housing 92 and accommodates the ball 93 is connected to the first and second injection steel pipes 23 ,
33 and to the injection nozzle 17 via a connecting pipe 95.

When the pressure of one of the injection steel pipes 23 and 33 becomes high, the ball 93 is displaced by the pressure and blocks the other injection steel pipe. As a result, the injection steel pipe that is not used is blocked.

〔Effect of the invention〕

As described above, the present invention is configured to forcefully feed fuel to an injection nozzle via an injection steel pipe having an appropriate inner diameter depending on the operating conditions of the engine.

Therefore, it is possible to reduce noise during idling operation, prevent surging in the mid-to-high rotation range, and improve driving sensation.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a first embodiment of the present invention, FIG. 2 is a sectional view showing a switching valve and a solenoid, FIG. 3 is a perspective view showing a plunger, a switching valve, and a distribution passage, and FIG. 4 is a sectional view showing a switching valve and a solenoid. 5 is a graph showing the relationship between the pump rotation speed and internal pressure of the pump. FIG. 6 is a sectional view of the main part showing the third embodiment. FIG. It is a sectional view showing a connection structure of steel pipes. 17... Injection nozzle, 23... First injection steel pipe, 24... Small diameter passage, 33... Second injection steel pipe, 34... Large diameter passage, 51, 72, 82... switching valve. Figure 2

Claims (1)

[Claims] 1. In a fuel injection device, high-pressure fuel discharged from a fuel injection pump is force-fed to an injection nozzle via a fuel passage, and is injected and supplied to a cylinder by opening a valve of this injection nozzle.
The fuel passage is composed of two or more passages with different inner diameters, and is provided with a switching valve that selectively opens and closes these passages, and this switching valve opens the small diameter passage when the engine speed is below a predetermined value. A fuel injection device characterized in that a large diameter passage is opened when the engine speed is higher than a predetermined value.