JPH0622141Y2 - Fuel injection nozzle for direct injection engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a fuel injection nozzle for a direct injection engine, and more particularly, to an improvement of a needle injection valve which is opened by the pressure of fuel.

(Prior Art) Conventionally, as a fuel supply device for a direct injection engine, a unit injector is configured by integrally connecting an injection nozzle and an injection pump as disclosed in, for example, Japanese Patent Laid-Open No. 62-153559. However, there is known one in which fuel is injected and supplied to the fuel chamber by the unit injector. According to this fuel supply device for a direct injection engine, since high-pressure fuel injection is possible, atomization of fuel is promoted, ignition delay is shortened, knocking is reduced, and utilization of air is promoted. Emissions of are reduced.

(Problems to be solved by the invention) However, this unit injector has a drawback in that it is costly due to its structure.

Therefore, a needle that is provided so as to be movable in the axial direction, moves in a valve closing direction that closes the injection hole by the biasing force of the needle spring, and moves in a valve opening direction that opens the injection hole by the fuel pressure supplied from the high pressure passage. It is considered to perform high-pressure fuel injection by setting a high fuel pressure in the high-pressure passage using a fuel injection nozzle equipped with a valve.

However, in this case, there is an upper limit to the seat surface pressure of the needle valve because it is necessary to ensure the durability of the needle valve and the valve seat,
There is a limit to how high the valve opening pressure can be set. For this reason, it is difficult to inject at a sufficiently high pressure, as indicated by the alternate long and short dash line in FIG.

Therefore, conventionally, a central plunger is provided on the back side of the needle valve, and the fuel pressure from the high-pressure passage is guided to the back side of the central plunger, so that the needle valve is urged by the needle spring and the fuel pressure received by the central plunger. There is a fuel injection nozzle capable of high pressure injection of fuel while opening the seat valve while keeping the seat surface pressure of the needle valve within a permissible range (see, for example, JP-A-57-151058).

However, in this fuel injection nozzle, since the central plunger is arranged on the back side of the needle valve, the length of the high pressure passage to the injection pump is shorter in the central plunger than in the needle valve. Therefore, the fuel pressure acting on the central plunger decreases faster than the fuel pressure acting on the needle valve, and the fuel pressure acting on the needle valve due to the resistance of the high pressure passage between the needle valve and the central plunger. Since it is difficult to lower the fuel consumption, there is a problem that the fuel runs out as shown by the solid line in FIG.

The present invention has been made in view of the above points, and an object of the present invention is to enable high-pressure injection of fuel by adopting a basic configuration that guides fuel pressure to the back surface of the needle valve, and By appropriately controlling the fuel pressure acting on the back surface of the fuel cell, it is possible to secure a good rise of injection and improve fuel shortage.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the solving means devised by the present invention is provided so as to be movable in the axial direction, and in the valve closing direction in which the injection hole is closed by the urging force of the needle spring. Targeting a fuel injection nozzle of a direct injection engine equipped with a needle valve that moves in the valve opening direction that opens the injection hole due to fuel pressure from the high pressure passage while communicating with the high pressure passage on the back side of the needle valve. And a pressure chamber for introducing the fuel pressure supplied to the high-pressure passage to urge the needle valve toward the introduced fuel pressure in the closing direction, and the pressure chamber is movable in the pressure chamber in the axial direction of the needle valve. Is provided in the pressure chamber and transmits the fuel pressure introduced into the pressure chamber to the needle valve side in the pressure chamber, and moves in the needle valve closing direction by the fuel pressure introduced into the pressure chamber. Member and a return spring that is provided in the pressure chamber and biases the orifice member in the needle valve opening direction,
When the orifice member moves a predetermined amount in the needle valve opening direction by the urging force of the return spring, the orifice member is provided with a stopper that prevents the orifice member from moving in the needle valve opening direction.

(Operation) With the above configuration, when the fuel pressure is introduced into the pressure chamber,
The fuel pressure passes through the orifice member, is transmitted to the needle valve side in the pressure chamber, and moves the orifice member in the needle valve closing direction. As a result, immediately before the start of fuel injection, the fuel pressure on the needle valve side in the pressure chamber becomes as high as in the high pressure passage, so the needle valve is urged in the needle valve closing direction by the high fuel pressure. As a result, immediately before the start of fuel injection, the needle valve is urged in the valve closing direction by the needle spring and the high fuel pressure.

When fuel injection is started, the orifice member moves in the needle valve opening direction by a predetermined amount, and thereafter, the stopper prevents the orifice member from moving in the needle valve opening direction.

When the fuel pressure supplied to the high pressure passage decreases, the fuel pressure in the high pressure passage decreases before the fuel pressure in the pressure chamber,
Along with this, the fuel pressure on the needle valve side in the pressure chamber also decreases, but since the fuel pressure on the needle valve side in this pressure chamber gradually decreases, the needle valve is still attached in the closing direction due to the high fuel pressure. It is energized.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a direct injection engine having a fuel injection nozzle according to an embodiment of the present invention. In the figure, 1 is a cylinder block, 2 is a cylinder head disposed on the cylinder block 1, and a cylinder 3 is formed between the cylinder block 1 and the cylinder head 2. A piston 4 is slidably fitted in the cylinder 3 and a combustion chamber 5 is formed by the piston 4 and the cylinder 3. The cylinder head 2 is provided with a needle valve type fuel injection nozzle 10 and a glow plug 6 so as to face the cavity of the piston 4.

Hereinafter, the fuel injection nozzle 10 will be described with reference to FIG. Reference numeral 11 denotes a nozzle body, and a needle valve guide hole 13 is formed on the combustion chamber 5 side of the nozzle body 11, and a needle valve 12 is slidably inserted into the needle valve guide hole 13. There is. Further, an extension pin 22 is arranged on the back side (upper side in FIG. 2) of the needle valve 12 via a connecting member 21, and a needle spring 23 is compressed between the extension pin 22 and the nozzle body 11. The tip of the needle valve 12 is brought into contact with the injection hole seat portion 14 of the nozzle body 11 with a predetermined surface pressure.

A fuel chamber 15 is formed around the needle valve 12. The needle valve 12 in the fuel chamber 15 is formed with a conical pressure receiving portion 12a. A high pressure passage 16 connecting the upper end of the nozzle body 11 and the fuel portion 15 is formed, and the end portion of the high pressure passage 16 on the upper end portion side of the nozzle body is provided with a nozzle tube (not shown). It is connected to the injection pump. Therefore, when fuel pressure is generated in the injection pump, this fuel pressure propagates to the fuel chamber 15 via the high pressure passage 16 and is transmitted to the needle valve 12
Acting on the pressure receiving portion 12a of the needle valve 12 and pushing up the needle valve 12 against the urging force of the needle spring 23.
2 opens. On the other hand, when the fuel pressure of the injection pump drops, the needle valve 12 is closed by the urging force of the needle spring 23.

A pressure chamber 31 is formed on the back side of the needle valve 12, and the pressure chamber 31 is connected to the high pressure passage 16. An orifice member 32 is fitted in the pressure chamber 31, and the orifice member 32 is slidable in the moving direction of the needle valve 12. The orifice member 32 includes a pressure chamber 31 on the high pressure passage 16 side and a pressure chamber 3 on the needle valve 12 side.
A small-diameter communication hole 32a for connecting with 1 is formed.
Further, in the pressure chamber 31 of the orifice member 32 on the needle valve 12 side, a return spring 33 for urging the orifice member 32 in the needle valve opening direction (upward in FIG. 2) is compressed. Further, a stopper 34 for restricting the movement of the orifice member 32 in the needle valve opening direction is provided in the pressure chamber 31 of the orifice member 32 on the high pressure passage 16 side.

The operation of the above embodiment will be described below with reference to the broken line in FIG. 3 and FIGS. 4 (a) to 4 (c).

First, in a normal state, the orifice member 32 is in contact with the stopper 34 by the urging force of the return spring 33 as shown in FIG.

When the fuel pressure generated by the injection pump propagates to the pressure chamber 31 through the high pressure passage 16, the orifice member 32 is pushed down while resisting the biasing force of the return spring 33 as shown in FIG. 4 (b). The fuel pressure in the pressure chamber 31 on the needle valve 12 side of the orifice member 32 is increased to the same level as the high pressure passage 16. Therefore, the needle valve 12 opens while resisting both the urging force of the needle spring 23 and the fuel pressure on the side of the needle valve 12 in the pressure chamber 31 (fuel pressure similar to that of the high-pressure passage 16). It is possible to inject fuel at a high pressure while keeping the seat surface pressure of the valve 12 within an allowable range. Therefore, since atomization of fuel is promoted,
Fuel economy and emission performance can be improved.

Next, when the fuel pressure of the injection pump drops,
The fuel pressure in the pressure chamber 31 on the high pressure passage 16 side of the orifice member 32 also decreases. In this case, since the orifice member 32 abuts on the stopper 34 and its movement in the needle valve opening direction is restricted as shown in FIG. 4C, the pressure chamber 31 is closer to the needle valve 12 side than the orifice member 32. The fuel pressure of is gradually reduced. Therefore, the pressure chamber 3
Since the fuel pressure on the side of the needle valve 12 in No. 1 is still high, the needle valve 12 quickly moves in the valve closing direction, so that the fuel runs out.

(Effect of the Invention) As described above, according to the fuel injection nozzle of the direct injection engine according to the present invention, it is provided in the pressure chamber so as to be movable in the axial direction of the needle valve, and is introduced into the pressure chamber to close the needle valve. In addition to transmitting the fuel pressure urged in the direction to the needle valve side, the fuel pressure introduced into the pressure chamber includes an orifice member that moves in the needle valve closing direction,
When the fuel pressure is introduced into the pressure chamber immediately before the start of fuel injection, the orifice member moves in the needle valve closing direction and increases the fuel pressure on the needle valve side in the pressure chamber to the same level as the high pressure passage. The needle valve is biased in the valve closing direction by the needle spring and the high fuel pressure, which enables high-pressure injection of fuel without increasing the seat surface pressure of the needle valve and promotes atomization of fuel, Fuel economy and emission performance are improved.

Further, when the fuel pressure supplied to the high-pressure passage decreases, the fuel pressure on the needle valve side in the pressure chamber gradually decreases, but the needle valve is still biased by the high fuel pressure in the valve closing direction. The valve is biased in the valve closing direction by the fuel pressure on the needle valve side in the pressure chamber and the needle spring, and the needle valve promptly closes the injection hole, so that the fuel runs out.

[Brief description of drawings]

The drawings illustrate an embodiment of the present invention. FIG. 1 is a vertical sectional side view of an essential part of an engine, FIG. 2 is a vertical sectional side view of a fuel injection nozzle,
FIG. 3 is an explanatory diagram showing the pressure of the fuel injection nozzle pressure chamber, and FIGS. 4 (a) to 4 (c) are explanatory diagrams showing the movement of the orifice member. 10 ... Fuel injection nozzle, 12 ... Needle valve, 16 ... High pressure passage, 31 ... Pressure chamber, 32 ... Orifice member, 33 ... Return spring, 34 ... Stopper.

Claims (1)

[Scope of utility model registration request] 1. An axially movable member, which moves in a valve closing direction to close the injection hole by the urging force of a needle spring, and moves in a valve opening direction to open the injection hole by fuel pressure from a high pressure passage. A fuel injection nozzle of a direct injection engine equipped with a needle valve, which is provided on the back side of the needle valve so as to communicate with the high pressure passage, and introduces the fuel pressure supplied to the high pressure passage. A pressure chamber for urging the needle valve toward the fuel pressure in the valve closing direction, and a pressure chamber that is provided in the pressure chamber so as to be movable in the axial direction of the needle valve, and the fuel pressure introduced into the pressure chamber is adjusted by the needle in the pressure chamber. An orifice member that is transmitted to the valve side and moves in the needle valve closing direction by the fuel pressure introduced into the pressure chamber; and an orifice member that is provided in the pressure chamber and that needs the needle member. When the return spring biasing the valve opening direction and the orifice member move a predetermined amount in the needle valve opening direction by the biasing force of the return spring, the orifice member is moved in the needle valve opening direction. A fuel injection nozzle for a direct injection engine, which is provided with a stopper for blocking.