JPH08254169A - Fuel injection valve for internal combustion engine - Google Patents

Abstract

PURPOSE: To increase or decrease the injection opening area of a fuel injection nozzle according to the number of revolutions of an engine and the change of a load and to generate a proper injection pressure at the whole area of the operation range of an engine. CONSTITUTION: The fuel injection valve of an internal combustion engine is an automatic valve type fuel injection valve wherein a needle valve 2 is moved in the direction of the tip of the injection valve and fuel is injected directly in a cylinder. A space between the outer periphery of the tip part of the needle valve and the inner periphery of the tip part of a nozzle body 1 is formed as a fitting-in slide part S capable of holding high pressure oiltightness and slidably fitted in the fitting-in slide part in the nozzle body 1. Nozzle hole groups 2a and 2b at least in two stages are formed in the needle valve 2 and on the tip side of the fitting-in slide part in such a manner to be close to each other. Further, a fuel communication passage 2c to interconnect the nozzle hole groups 2a and 2b and a fuel oil passage 5 at the upper part of the needle valve 2 is formed at the interior.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection valve for an internal combustion engine.

[0002]

2. Description of the Related Art FIG. 4 shows an example of the structure of a conventional fuel injection valve. In the figure, 01 is a nozzle body, 02 is a needle valve, 0
Reference numeral 3 is a nozzle holder, 04 is a needle valve stopper, 05 is a fuel oil passage, 06 is an injection port, 07 is a spring, and 08 is a thrust rod. Normally, the fuel injection valve is arranged in the cylinder head of the engine, and when the fuel is not injected, the needle valve 02 is pressed against the seat portion of the nozzle body 01 by the spring 07 via the thrust rod 08, and the closed state (Fig. 4). State).

When a fuel injection pump (not shown) starts discharging fuel in conjunction with the rotation of the crankshaft of the engine, the pressure wave passes through the fuel injection pipe (not shown), and further the nozzle holder 03. From the needle valve 0 in the closed state through the fuel oil passage 05 communicating with the nozzle body 01 from the
2, the needle valve 02 is acted upon by a hydraulic force to push it upward. When this force exceeds the urging force of the spring 07 that presses the needle valve 02 against the lower seat portion,
The needle valve 02 starts to move upward and enters the open state.

The fuel is ejected from the injection port 06 into the combustion chamber by a high pressure, and atomization and evaporation proceed due to the interaction between the movement of the spray itself and the high temperature and high pressure air in the combustion chamber to form a combustible mixture. Normally, a plurality of the injection holes 06 are provided radially so that the fuel is evenly dispersed in the cylinder to facilitate the formation of an efficient air-fuel mixture. Self-ignition and poor ignitability are given to the fuel having good ignitability. The fuel is ignited by an auxiliary ignition source (not shown), and combustion proceeds.

[0005]

The above-mentioned conventional example has the following problems. The illustrated fuel injection valve is a so-called automatic valve whose valve is opened and closed by the hydraulic pressure of fuel oil. The pressure source is a fuel injection pump (not shown). In a normal jerk type fuel injection pump, the rotation speed of the drive shaft of the fuel injection pump and the rotation speed of the engine (two cycles) are the same. When the engine speed is high, the plunger speed is high, and when the engine speed is low, the plunger speed is low. Therefore, the fuel discharge speed is high in the high speed rotation range and low in the low speed rotation range, so that the fuel discharge speed changes depending on the engine speed.

On the other hand, since the injection port 06 of the nozzle body, which is the injection port of the fuel oil into the combustion chamber, has a geometrically constant area, the fuel from the injection port 06 is discharged in relation to the discharge speed of the fuel injection pump. The injection pressure is high in the high speed rotation range and low in the low speed rotation range. The total area of the injection port 06 is set from the mechanical pressure resistance condition of the fuel injection system components and the fuel injection period that determines the combustion performance, and is generally determined so as to correspond to the maximum output point of the engine. There is. Therefore, in the low speed rotation range of the engine, the opening area of the injection port is relatively large with respect to the discharge speed of the fuel injection pump, and the injection pressure tends to decrease.

In order to obtain good combustion in the combustion chamber, it is necessary to mix fuel and air quickly and completely, and for this purpose, a high injection pressure is required to increase the mixing energy. However, in the low-speed engine range, the fuel injection pressure decreases as described above, and combustion may deteriorate especially under high load conditions. This problem becomes more remarkable when the ratio (so-called turndown ratio) is large or when the output is further increased.

An object of the present invention is to solve the above-mentioned problems, control the opening area of the nozzle injection port at the time of fuel injection in response to changes in the engine speed, reduce the area in the low speed rotation range, and increase the high speed rotation. By increasing it in the high speed range, the injection pressure does not rise excessively, and in the low speed range, the drop of the injection pressure is suppressed to maintain an appropriate injection pressure, and the load is similarly handled. Even so, it is an object of the present invention to provide a fuel injection valve for an internal combustion engine which can reduce or increase the opening area of the nozzle injection port and can obtain an appropriate injection pressure over the entire operating range of the engine.

[0009]

A fuel injection valve for an internal combustion engine according to the present invention is an automatic valve fuel injection valve in which a needle valve 2 moves toward the tip of the fuel injection valve by fuel oil pressure to inject fuel directly into a cylinder. Between the outer circumference of the tip of the needle valve and the inner circumference of the tip of the nozzle body 1 is formed as a fitting sliding portion S capable of maintaining high pressure oil tightness, and the needle valve is fitted in the nozzle body. The needle valve is slidably fitted in the sliding portion, and at least two stages of injection port groups 2a, 2b are formed in the needle valve in close proximity to the tip end side of the fitting sliding part, and the injection port group is internally provided. A fuel communication passage 2c is formed to connect the fuel oil passage 5 above the needle valve.

[0010]

In the present invention, by virtue of the above-mentioned constitution, it operates as follows. The needle valve 2 moves toward the tip of the injection valve due to the pressure of the fuel oil pumped from the fuel injection pump, but the lift of the needle valve 2 determines the balance between the pressure of the fuel oil and the urging force of the spring 7. When the force due to the pressure of the fuel oil exceeds the biasing force of the spring 7, the needle valve 2 is pushed downward and the needle valve 2
When the tip of the nozzle protrudes from the nozzle body 1, the nozzle group 2a, 2b
Is opened and fuel is injected. When the fuel injection pressure (hereinafter, abbreviated as injection pressure) is high, the lift of the needle valve 2 is large, and the needle valve 2 is in a state of largely protruding from the nozzle body 1, but when the injection pressure is low, the needle valve 2 The lift of No. 2 is small, and the protrusion of the needle valve 2 from the nozzle body 1 is small. In addition, between the outer circumference of the tip of the needle valve 2 and the inner circumference of the tip of the nozzle body 1, a fitting sliding portion S capable of maintaining high pressure oil tightness is formed to seal the leakage of fuel oil and to prevent the fuel inside the needle valve 2 from leaking. A plurality of stages of injection port groups 2a and 2b communicating with the fuel oil passage 5 above the needle valve 2 via the communication passage 2c are opened by the lift of the needle valve 2 to inject fuel.

At this time, depending on the level of the injection pressure, the needle valve 2
The amount of lift of the needle valve 2 is determined and a plurality of injection port groups 2a and 2b are formed in the movement direction of the needle valve 2. Therefore, when the injection pressure is low, the needle valve lift amount is small and only the injection port 2a at the tip end is opened. When the injection pressure is high, on the contrary, when the injection pressure is high, the needle valve lift amount is large, and the number of opening injection port groups is increased and the opening injection port area is increased. In this way, the opening nozzle area of the needle valve tip can be changed according to the injection pressure.

[0012]

Embodiment FIG. 1 shows the structure of the main part of a fuel injection valve according to an embodiment of the present invention. In the figure, 1 is a nozzle body, 2
Is a needle valve, 2a and 2b are nozzle groups, 2c is a fuel communication passage, 3 is a nozzle holder, 4 is a needle valve stopper, 5 is a fuel oil passage, 7 is a spring, 9 is an upper nozzle body, and S is a needle valve. 2 shows a fitting sliding portion between the outer circumference of the tip portion of No. 2 and the inner circumference of the tip portion of the nozzle body, that is, a seal portion capable of maintaining high pressure oil tightness. FIG. 2 is an explanatory view showing the detailed structure of the tip portion of the needle valve 2. In the present invention, a plurality of stages of jet nozzle groups are formed close to the tip of the needle valve 2, but in the embodiment, the two stages of jet nozzle groups 2a, 2b.
The case of is shown.

The structure and operation of the embodiment will be described with reference to FIGS. When the fuel oil pressure is not acting on the needle valve 2, the needle valve 2 is pushed up by the urging force of the spring 7 toward the upper nozzle body 9 side, and the two-stage injection port group 2a at the tip of the needle valve 2 Both 2b are hidden inside the tip of the nozzle body 1 and sealed by a fitting sliding portion S so that fuel does not leak out. (See FIG. 2 (a)). Fuel oil passage 5
When a pressure wave of fuel oil from a fuel injection pump (not shown) arrives at, the hydraulic pressure acts on the upper surface of the needle valve 2 and a downward force is applied. When this downward force exceeds the upward biasing force of the spring 7, the needle valve 2 starts moving downward, and the needle valve 2 moves to a position where the fuel oil pressure and the biasing force of the spring 7 are balanced.
By adjusting the spring constant and the initial setting force of the spring 7, the lift of the needle valve 2 with respect to the fuel oil pressure can be controlled. Therefore, only the injection port group 2a below the needle valve opens up to a predetermined pressure, and the pressure is When exceeding this level, the function of the injection valve is set such that the upper injection port group 2b is opened.

When the injection pressure is within a predetermined pressure level, the lift of the needle valve 2 is small, so that the needle valve 2 is less likely to protrude from the nozzle body 1 and only the injection port group 2a below the needle valve is open ( As shown in FIG. 2B, the fuel that has reached the injection port portion from the fuel oil passage 5 above the needle valve via the fuel communication passage 2c is injected only from the injection port group 2a. When the injection pressure exceeds a predetermined pressure level, the lift of the needle valve 2 increases, so that the needle valve 2 largely protrudes from the nozzle body 1 and the two injection port groups 2a and 2b at the tip of the needle valve 2 are both open. Then (see FIG. 2C), fuel is injected from all the injection port groups.

With the above-mentioned structure, it is possible to change the opening nozzle area of the fuel injection nozzle according to the rotation speed of the engine and the corresponding fuel discharge speed of the fuel injection pump. FIG. 3 is an explanatory view of the injection pressure control action by the fuel injection valve of the embodiment. As shown in the figure, in the region where the fuel discharge speed is low in the low speed rotation range, by making the relative area of the opening nozzle small, it is possible to prevent the injection pressure from decreasing and obtain an appropriate level of injection pressure. At the same time, in the region where the fuel discharge speed is high in the high-speed rotation region, the relative opening nozzle area is increased to prevent excessive increase of the injection pressure.

It is possible to change the area of the opening nozzle even with respect to the fuel injection amount, that is, the load, and the combustion situation is unstable due to the drop in the injection pressure in the past including the operation at low speed and high load. Combustion performance can be significantly improved even under the operating conditions that had become.

Although the embodiment described here is the fuel injection valve in which the two-stage injection port groups 2a and 2b are formed close to each other, the injection port group can be formed in a plurality of stages of three or more stages. In this case, the area of the injection port can be adjusted more finely than in the case of two stages, and the fuel injection pressure in the low speed rotation range can be increased more finely.

[0018]

According to the fuel injection valve of the internal combustion engine of the present invention, the opening nozzle area of the fuel injection nozzle can be accurately set according to the engine speed and load, that is, the fuel discharge speed and the fuel injection amount of the fuel injection pump. It can be changed. As a result, it is possible to inject fuel into the cylinder at an appropriate pressure over the entire operating range of the engine, and the combustion performance is remarkably improved even under operating conditions where the combustion situation was unstable due to the decrease in injection pressure. Can be improved.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a fuel injection valve of an internal combustion engine according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a detailed structure of a needle valve tip portion of the fuel injection valve shown in FIG.

FIG. 3 is an explanatory view of an injection pressure control action of the fuel injection valve shown in FIG.

FIG. 4 is a vertical cross-sectional view of a fuel injection valve of an internal combustion engine according to a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Nozzle main body, 2 ... Needle valve, 2a, 2b ... Injection port group, 2c
... Fuel communication passage, 3 ... Nozzle holder, 4 ... Needle valve stopper,
5 ... Fuel oil passage, 7 ... Spring, 9 ... Upper nozzle body, S ... Fitting sliding portion.

Claims (1)

[Claims] 1. An automatic valve type fuel injection valve in which a needle valve (2) moves toward the tip of a fuel injection valve by fuel hydraulic pressure to inject fuel directly into a cylinder, the needle valve outer periphery and a nozzle. Between the inner circumference of the tip portion of the main body (1) is formed as a fitting sliding portion (S) capable of maintaining high pressure oil tightness, and the needle valve is slidably fitted to the fitting sliding portion in the nozzle body. The needle valve is provided with at least two stages of injection port groups (2a) and (2b) in close proximity to the tip side of the fitting sliding portion, and the injection port group and the upper part of the needle valve are provided inside. A fuel injection valve for an internal combustion engine, characterized in that a fuel communication passage (2c) connecting to the fuel oil passage (5) is formed.