JPH0472989B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an accumulating fuel injection nozzle for a diesel engine.

[Prior Art] A pressure accumulating fuel injection nozzle is described, for example, in "Komatsu Giho Vol. 28 No. 3" published in 1981, pages 25 to
As shown in "Pressure Accumulator Fuel Injection System for Diesel Engines" on page 31, it is possible to increase the injection pressure at low speeds, shorten the fuel injection period, increase the fuel injection rate, and improve the thermal efficiency of the engine. Although it has advantages, on the other hand, due to its characteristics, the injection rate is high immediately after the start of injection, and the combustion pressure rises rapidly, resulting in an increase in fuel noise and an increase in NOx in the exhaust gas.

[Purpose of the invention]

It is an object of the present invention to solve the above-mentioned problems by suppressing the fuel injection rate immediately after the start of fuel injection to a low level to moderate the increase in fuel pressure while making use of the advantages of the pressure accumulation type fuel injection nozzle.

[Summary of the invention]

The present invention has a fuel passageway to a back pressure chamber that holds fuel pressure that acts on a nozzle needle in the valve closing direction, and opens at a predetermined pressure only for the inflow of fuel into the back pressure chamber. The above object is achieved by providing a control valve having a throttle passage that is always in communication with the outflow and slowing down the opening speed of the nozzle needle.

[Action and effect of invention]

In the above configuration, the operation of the nozzle needle is controlled by the pressure balance between the pressure accumulation chamber and the back pressure chamber,
By controlling at least one of the pressures, the nozzle needle is operated in the valve opening direction.

With this valve opening operation, the pressure in the back pressure chamber will flow out to the low pressure side, but the flow of fuel into and out of the back pressure chamber is controlled by the control valve, and the flow of fuel will be prevented. Since it always acts as a throttle, the fuel pressure in the back pressure chamber will gradually decrease. Therefore, the nozzle needle opens slowly, making it possible to keep the fuel injection rate low immediately after the start of injection, resulting in a gradual increase in fuel pressure, which reduces fuel noise and exhaust gas.
Can reduce NOx.

〔Example〕

Next, embodiments of the present invention will be described using the drawings.

1 to 4 relate to the first embodiment of the present invention, in which FIG. 1 is a longitudinal cross-sectional view showing the overall configuration of a pressure accumulating fuel injection nozzle, and FIG. 2 is a view of the tip of the nozzle shown in FIG. An enlarged sectional view, FIG. 3 shows the check valve control valve shown in FIG. 1 (control valve of the present invention).
The enlarged vertical cross-sectional views of No. 11 and FIGS. 4a, b, and c are characteristic diagrams showing the corresponding changes in the lift amount of the check valve, the lift amount of the nozzle needle, and the injection rate with respect to each crankshaft rotation angle.

First, the structure of the first embodiment will be explained.

In FIG. 1, the nozzle holder main body H is assembled into parts 1, 2, and 3 due to assembly. Inside the nozzle holder body H are a nipple 4, a control valve part 24, a nozzle 5, a nozzle needle 13, a check valve 7, a spring 8, a check valve stopper 6, a check valve control valve 11, and a check valve control valve 11 that is closed. Spring 12 that presses with a constant set load in the valve direction
etc. are installed. A substantially cylindrical first pressure accumulating chamber 10 is surrounded by a check valve 7 and a check valve stopper 6, which form a part of the main body H. Also, nozzle 5 and nozzle needle 1
3 and a substantially cylindrical second pressure accumulation chamber 10'.
is formed. The first and second pressure accumulation chambers are in the passage 2.
3, it is constantly communicated with. When fuel is not stored in the pressure storage chambers 10, 10', the check valve 7 is pressed against the end surface of the check valve stopper 6 by the spring 8, and the nozzle needle 13 is pressed downwardly into the nozzle 5, so that the nozzle nozzle is closed. The tip surface 14 of the needle 13 is in close contact with the valve seat 5a.

The check valve control valve 11 is a rotating body as shown in FIG. 3, and a throttle 11a is provided in the center thereof.

The control valve portion 24 also includes a control valve 1 which is slidably and oil-tightly fitted into a valve cylinder 200 having a passage hole 201 on the side surface.
6 is pressed against the side surface of the valve cylinder 200 with a constant set load applied by a spring 17.

Next, the operation will be explained.

A fuel injection pump (not shown) is provided upstream of the nipple 4 via a high-pressure pipe (not shown), and fuel flows into the fuel inlet 18 during the fuel pumping stroke of the pump.

Normally, the control valve 16 has a spring 1
7 is pressed against the end face of the valve cylinder 200, the control valve tip 161 of the control valve 16 protrudes from the other end face of the valve cylinder, and the passage hole 201 bored in the valve cylinder 200 is connected to the second high-pressure fuel passage 20, 21 and is in an open state. The fuel flowing into the fuel inlet 18 first passes through the second high-pressure fuel passage 20 and into the passage hole 2 formed on the side of the valve cylinder 200.
01 and the second high-pressure fuel passage 21, it flows into the pressure storage chambers 10, 10' and is
Boost the voltage within 0'. When the force exerted on the control valve 16 by the fuel pressure overcomes the set load of the spring 17, the control valve 16 compresses the spring 17 and the control valve tip 161 closes the end face of the valve cylinder 200, so that the control valve 16 closes.

Thereafter, the fuel opens the check valve control valve 11 from the first high-pressure fuel passage 19, flows into the check valve chamber 9 through the first high-pressure fuel passage 22, opens the check valve 7, and opens the pressure accumulation chamber. 10,
Further fuel flows into the accumulator 10', and the pressure inside the pressure accumulator chambers 10, 10' is increased. At the same time, the fuel flows into the back pressure chamber 25 through the first high pressure fuel passage 24 and flows into the back pressure chamber 25.
The pressure inside 5 is increased.

When the fuel pressure stroke ends, the check valve 7 closes due to the force of the spring 8 and the pressure of the high pressure fuel in the pressure storage chambers 10, 10', and the back pressure chamber 25 closes.
The fuel in the first high pressure fuel passages 19, 22, 24
As shown in FIG. 2, the nozzle needle 13 is opened by the pressure of the high pressure fuel in the pressure accumulation chambers 10, 10', and the high pressure fuel in the pressure accumulation chambers 10, 10' is injected from the injection hole 15. be done.

After that, when the pressure in the pressure accumulation chamber 10 decreases and the force of the spring 17 of the control valve becomes greater, the control valve 16 opens, and the pressure in the pressure accumulation chamber 10 decreases all at once. The needle 13 quickly closes to end fuel injection.

That is, the control valve 16 plays the role of rapidly stopping fuel injection.

The function of the check valve control valve 11 will be explained using FIG. 4.

In FIGS. 4a, b, and c, the broken lines show the characteristics when the check valve control valve 11 is not provided, and the solid lines show the characteristics of the first embodiment of the present invention in which the check valve control valve 11 is provided.

When the check valve control valve 11 is not provided, the check valve 7 quickly closes from the state 40a to the state 40b when the fuel pumping stroke ends, as shown by the broken line in FIG. 4, and the back pressure is reduced. The fuel in the chamber 25 is transferred to the first high pressure fuel passages 19, 2.
2 and 24, the nozzle needle 13 also changes from the state 41a to 4.
The valve opens quickly to the maximum lift amount to the state 1b, and as a result, the injection rate immediately after the start of injection increases rapidly from the state 42a to the state 42b.

On the other hand, the aperture hole 11a as shown in FIG.
When the check valve control valve 11 is provided, when the fuel pressure feeding stroke is completed, the check valve control valve 11 closes and the fuel in the back pressure chamber 25 gradually escapes from the throttle hole 11a. Accordingly, the check valve 7 changes from the state 40a to 4
The valve closes slowly to the 0c state. Therefore, the nozzle needle 13, which is urged in the valve closing direction by the fuel in the back pressure chamber 25 and the spring 8, opens slowly, and the injection rate immediately after the start of injection changes from the state shown at 42a to the state shown at 42c. Since the state changes to the state shown, the fuel injection rate immediately after the start of fuel injection can be kept small, and as a result, the fuel pressure increases gradually.

Next, a second embodiment of the present invention will be described.

The only difference between the second embodiment and the first embodiment is the structure of the check valve control valve and the part in which it is incorporated.Since the other embodiments are the same, only the differences will be described.

5 to 7 relate to the second embodiment of the present invention, and FIG. 5 is a partially enlarged cross-sectional view of the check valve control valve 11 assembled in the check valve stopper 6 (see FIG. 6). 6 is a sectional view taken along line XX in FIG. 5, and FIG. 7 is a sectional view taken along line Z-Z in FIG. 6.

In the second embodiment, the check valve control valve 1
1 has stopper sliding parts 601 forming a part of the check valve stopper 6 at four places on its side surface.
is slidably supported in the direction of the central axis.
When the check valve control valve 11 is opened, the high pressure fuel passing through the first high pressure fuel passage 19 is released through the notch 5 provided in a part of the check valve stopper 6.
0 into the first high pressure fuel passage 22 .

Since the operation is the same as that of the first embodiment, a description thereof will be omitted.

In the second embodiment, there is no particular functional problem even if the spring 12 is eliminated, so eliminating the spring 12 makes it possible to reduce the number of parts.

Furthermore, although the embodiments have all been shown using hole-type nozzles, it goes without saying that the present invention can also be applied to other types of nozzles, such as pin-type nozzles and throttle-type nozzles.

[Brief explanation of drawings]

1 to 4 relate to the first embodiment of the present invention, in which FIG. 1 is a longitudinal cross-sectional view showing the overall configuration of a pressure accumulating fuel injection nozzle, and FIG. 2 is a view of the tip of the nozzle shown in FIG. FIG. 3 is an enlarged longitudinal sectional view of the check valve control valve 11 shown in FIG. FIG. 3 is a characteristic diagram showing corresponding changes in lift amount and injection rate. Further, FIGS. 5 to 7 relate to the second embodiment of the present invention, and FIGS.
The figure is a partially enlarged sectional view (YY sectional view of FIG. 6) of the check valve control valve assembled in the check valve stopper 6, and FIG. 6 is the X--X of FIG.
The X sectional view and FIG. 7 show the Z-Z sectional view of FIG. 6, respectively. H... Nozzle holder body, 5... Nozzle, 7...
...Check valve, 10,10'...Accumulation chamber, 1
1... Check valve control valve (fuel valve of the present invention),
11a... Throttle hole forming a throttle part, 13... Nozzle needle, 15... Nozzle hole, 16... Control valve, 18... Fuel inlet, 19, 22, 24...
...first high pressure passage, 20, 21...second high pressure passage.

Claims (1)

[Scope of Claims] 1. A nozzle needle that is slidably disposed in a nozzle holder and opens and closes a nozzle hole formed in the nozzle holder; a pressure accumulation chamber that holds fuel pressure to be applied; and a back pressure chamber that is formed in the nozzle holder and holds fuel pressure that acts on the nozzle needle in the valve-closing direction; In the pressure accumulation type fuel injection nozzle, the nozzle needle is opened and fuel is injected by controlling the acting force on the nozzle needle to be higher than the acting force on the nozzle needle due to the pressure in the back pressure chamber, A control valve is provided in the fuel passage to the back pressure chamber, and has a throttle passage that opens at a predetermined pressure only when fuel flows into the back pressure chamber, and is always in communication with the inflow and outflow. A pressure accumulation type fuel injection nozzle characterized by: