JP2506068Y2 - Fuel injection nozzle for diesel engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a fuel injection nozzle for a diesel engine, and more particularly to a fuel injection nozzle suitable for use in a direct injection diesel engine having a wide rotation range.

[Prior Art] In a fuel injection nozzle of a conventional diesel engine, a needle valve is slidably provided in a nozzle body, and the needle valve is biased in a closing direction by a nozzle spring. When fuel is supplied from the pump, the needle valve overcomes the force of the nozzle spring and opens the oil injection hole of the nozzle body to inject fuel. The valve opening set pressure of such a fuel injection nozzle is determined by the nozzle spring, and once the spring force is set, it is always constant regardless of the operating state of the engine.

However, in such a fuel injection nozzle with a constant valve opening set pressure, in a direct injection engine with a wide operating rotation range, the state of fuel spray, the pressure, and the size of fuel particles change depending on the rotation speed and load. , It is difficult to control ignition in all ranges, that is, fuel matching is difficult.

The applicant can change the force of the nozzle spring depending on the temperature, reduce the force of the nozzle spring at low temperature to reduce the valve opening set pressure, and inject the required fuel when warming up the engine at low temperature. In this way, a utility model registration application was previously filed for a fuel injection nozzle designed to prevent irregular combustion of the engine during low-temperature operation and to prevent discharge of unburned gas (see Japanese Utility Model Publication No. 57-49566). This technology itself cannot solve the above-mentioned problem of combustion matching in a direct injection type engine.

Further, Japanese Utility Model Laid-Open No. 59-177774 proposes a technique for changing the valve opening period and the valve closing period in high-speed high-load operation and low-speed low-load operation. However, it is not possible to sufficiently miniaturize the fuel particles and improve the ignitability only by controlling the valve opening period.

Further, Japanese Utility Model Publication No. 55-10607 discloses a technique of setting a high valve opening pressure during high speed operation and a low valve opening pressure during low speed rotation. However, if the valve opening pressure is low at low speed rotation, the fuel particles become large and it becomes difficult to ignite.

[Problems to be Solved by the Invention] Therefore, an object of the present invention is to inject fuel into a diesel engine, which has good ignitability in a wide range of rotations in both high-speed rotation range and low-speed rotation range and can perform efficient combustion. In providing the nozzle.

[Means for Solving the Problems] Therefore, according to the present invention, in the nozzle spring, the first spring and the second spring having a smaller spring force than the first spring are arranged in series via the piston. The first chamber provided with the second spring on the side farther from the needle valve is always communicated with the second chamber on the side farther from the needle valve than the first chamber.
The chamber is communicated with the return pipe leading to the fuel tank, and is also communicated with the oil supply pipe leading to the housing of the fuel injection pump through the opening / closing valve provided in the second chamber. When the engine rotates at high speed, the second chamber communicates with the return pipe leading to the fuel tank, and the communication with the oil supply pipe reaching the housing of the fuel injection pump is cut off. When the engine rotates at low speed, the second chamber And a solenoid-operated piston that is switched so as to cut off the communication with the return pipe leading to the fuel tank and to connect the oil supply pipe leading to the housing of the fuel injection pump.

[Advantageous effects of the invention] When the engine rotates at high speed, the first chamber provided with the second spring communicates with the return pipe leading to the fuel tank,
The fuel in the first chamber is free to escape into the return pipe. In this way, the fuel in the first chamber can escape freely, so that the first spring and the second spring expand and contract integrally via the piston. Therefore, when the engine rotates at a high speed, the valve opening pressure becomes smaller than when the engine rotates at a low speed, which will be described later, and a large amount of fuel can be injected.

When the valve opening pressure is low like this, the fuel particles become large,
Since it is easy to ignite when rotating at high speed, efficiency can be improved by injecting a larger amount of fuel than the size of the fuel particles.

When the engine is rotating at a low speed, the communication between the first chamber provided with the second spring and the return pipe is cut off, and 3 to 6 kg / cm ² of fuel is supplied to the ^second from the oil supply pipe reaching the housing of the fuel injection pump. It acts on the on-off valve installed in the chamber. At the time of injection,
The needle valve is pushed up by the pressure of the fuel from the fuel injection pump and the first spring contracts. At this time, the piston remains stationary because the fuel in the first chamber cannot escape to the outside. Therefore, when the engine rotates at a low speed, the valve opening pressure is set by the first spring 6 having a large spring force, the fuel injection amount decreases, and atomization is promoted.

That is, by increasing the valve opening pressure at low speed rotation, the fuel particles can be made finer, and as a result, the ignitability is improved. Even if the fuel injection amount is small, there is no problem at low speed rotation,
Combustion efficiency is improved by improving ignitability.

As described above, according to the present invention, it is possible to improve the ignitability of fuel over the entire rotation range, particularly the wide range of rotations used, and the combustibility of fuel of a direct-injection diesel engine that has excellent ignitability only at a specific rotation speed. Can be improved.

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, a needle valve 2 is provided in the nozzle body 1, and the needle valve 2 is biased in a closing direction by a nozzle spring, which will be described later.
22 from the fuel supply pipe 25 (Fig. 4) to 22 (Fig. 4)
When fuel is supplied through the needle valve 2, the needle valve 2 overcomes the force of the nozzle spring and opens the ejection hole of the nozzle body 1 to inject fuel.

The nozzle spring is configured such that a first spring 6 and a second spring 7 having a weaker spring force than the first spring 6 are arranged in series via a piston 5, and as described above, The valve 2 is biased in the closing direction. The first chamber 8 provided on the side farther from the needle valve 2 and provided with the second spring 7 always communicates with the second chamber 9 farther from the needle valve 2 than the first chamber 8 through the opening 10. are doing. The second chamber 9 is adapted to communicate with a return pipe 27 (see FIG. 4) which leads to a fuel tank 24 (see FIG. 4) via a passage 11, and is provided in the second chamber 9 to provide a spring. An oil supply pipe 26 (fourth cylinder) is connected to a housing of a fuel injection pump 22 (FIG. 4) through a passage 16 through an opening / closing valve composed of a spherical body 14 which is urged to close the opening 15 by the third cylinder.
(See Figure).

A piston 20 operated by a solenoid 19 is provided. The piston 20 communicates with the passage 11 and the return pipe 27 (Fig. 4) and the passage 16 when the solenoid 19 is not excited. When the solenoid 19 is excited, the communication between the passage 11 and the return pipe 27 is cut off and the passage 16 is opened as shown in FIGS. 2 and 3. Therefore passage 11
At the position of the piston 20 shown in FIG. 1 where the return pipe 27 communicates with the return pipe 27, the fuel in the first chamber 8 provided with the second spring 7 passes through the opening 10, the second chamber 9, and the passage 11. Free return tube
Can escape to 27. Further, at the position of the piston 20 shown in FIGS. 2 and 3 where the communication between the passage 11 and the return pipe 27 is cut off, the fuel in the first chamber 8 provided with the second spring 7 escapes to the outside. I can't. And the piston 20 is the passage
When the open position of the fuel injection pump 22 (FIG. 4) is 16 when it is in the position shown in FIG. 2 and FIG. 3, the oil supply pipe 26 leading to the housing (the pressure inside the housing is usually 3 to 6 kg / cm ² ). From FIG. 4, fuel having a pressure of ³ to 6 kg / cm ² acts on the ball 14 of the on-off valve through the passage 16.
The spring force of the spring 13 urging the sphere 14 of the on-off valve is set to such a magnitude that the sphere 14 is opened by the fuel pressure from the oil supply pipe 26.

In addition, in FIG. 1, reference numerals 4, 12, and 17 are connecting pipes, 18 is a passage for returning the fuel oozing out along the needle valve 2 to the fuel tank 24 through the return pipe 27, and 21 is a ground.

FIG. 4 shows the piping relationship between the fuel injection pump and the fuel tank and the fuel injection nozzle. The connection pipe 4 of the fuel injection nozzle 23 is connected to the fuel supply pipe 25 connected to the discharge port of the fuel injection pump 22. Further, the connection pipe 17 is connected to a fuel supply pipe 26 connected to the housing of the fuel injection pump 22, and the connection pipe 12 is connected to a return pipe 27 leading to the fuel tank 24. A solenoid 19 for operating the piston 20 of the fuel injection nozzle 23 is connected to a battery 30 by an electric wire 29 provided with a switch 28.

Next, the mode of operation of the fuel injection nozzle will be described.

FIG. 1 shows the state of the fuel injection nozzle when the engine rotates at a high speed. At this time, the switch 28 is off and the solenoid 19 is de-energized. When the solenoid 19 is not excited, the piston 20 is pushed downward by a spring (not shown) so that the passage 11 communicates with the return pipe 27 and the passage 16 is blocked. Therefore, the fuel in the first chamber 8 provided with the second spring 7 can freely escape to the return pipe 27 via the opening 10, the second chamber 9 and the passage 11. In this way, the fuel in the first chamber 8 can freely escape, so that the first spring 6 and the second spring 7 integrally expand and contract via the piston 5.

Now, assuming that the spring constant of the first spring 6 is k1, the contraction at the time of setting is x1, the spring constant of the second spring 7 is k2, and the contraction at the time of setting is x2, the spring constant at this time is (k1. k2) / (k1 + k2) and the valve opening pressure becomes y1 = {(k1 · k2) (x1 + x2)} / (k1 + k2).

2 and 3 show the state of the fuel injection nozzle when the engine rotates at a low speed. At this time, the switch 28 is turned on and the solenoid 19 is excited, so that the piston 20 moves upward against the spring force of a spring (not shown). Move to. As a result, the communication between the passage 11 and the return pipe 27 is blocked and the passage 16 is opened.

At the time of no injection shown in FIG. ² , fuel having a pressure of ^{3 to} 6 kg / cm ² in the housing of the fuel injection pump 22 flows from the passage 16 through the oil supply pipe 26 to open the opening / closing valve 14 to open the piston 5 to 3
A pressure of 6 kg / cm ² acts.

At the time of the injection shown in FIG. 3, the needle valve 2 is pushed up by the pressure of the fuel from the fuel injection pump 22, and the first spring 6 contracts. At this time, the piston 5 remains stationary because the fuel in the first chamber 8 cannot escape to the outside.

 The valve opening pressure at this time is y2 = k2 x2.

Since the spring force of the first spring 6 is set to be larger than the spring force of the second spring 7, as can be seen from the above equation, the valve opening pressure is higher when the engine rotates at high speed than when it rotates at low speed. Is small (the valve opening pressure is higher during low speed rotation than during high speed rotation), a large amount of fuel is injected during high speed rotation of the engine, and the fuel injection amount decreases during low speed rotation, which promotes atomization. Therefore, even in the case of a direct-injection engine with a wide range of rotation, the fuel ignitability can be improved over the entire rotation range, and efficient combustion can be performed. [Effects of the Invention] As described above, the present invention has the following excellent effects.

(I) Since the valve opening pressure is low during high speed rotation, a large amount of fuel can be injected, which contributes to an increase in output.

(Ii) Since the valve opening pressure is high at low speed rotation, the fuel particles are made finer, and the ignitability of a small amount of fuel can be improved.

(Iii) Therefore, rational fuel injection can be performed over a wide rotation range.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a fuel injection nozzle according to an embodiment of the present invention, showing a state of the fuel injection nozzle when an engine rotates at a high speed. 2 and 3 are longitudinal cross-sectional views of the essential parts showing the state of the fuel injection nozzle when the engine is rotating at a low speed.
The figure shows the case of no injection, and FIG. 3 shows the case of injection. FIG. 4 is a diagram showing a piping state of the fuel injection pump, the fuel tank, and the fuel injection nozzle. 1 ... Nozzle body, 2 ... Needle valve, 3 ... Fuel supply passage, 5 ... Piston, 6 ... First spring, 7 ... Second spring, 8 ... First chamber , 9 ...
… Second chamber, 11 …… Fuel return passage for first chamber, 16 ……
Passage through which fuel flows from the fuel injection pump casing, 19 ... solenoid, 20 ... piston

Claims (1)

(57) [Scope of utility model registration request] 1. A needle valve provided in a nozzle body is biased in a closing direction by a nozzle spring, and when fuel is supplied from a fuel injection pump, the needle valve overcomes the force of the nozzle spring to inject the nozzle body. In a fuel injection nozzle of a diesel engine in which an oil hole is opened to inject fuel, the nozzle spring includes a first spring and a second spring having a smaller spring force than the first spring via a piston. Are arranged in series, and the first chamber on the side farther from the needle valve and provided with the second spring is the second chamber on the side farther from the needle valve than the first chamber. The second chamber is communicated with the return pipe leading to the fuel tank, and the fuel is supplied via the on-off valve provided in the second chamber. The fuel supply pipe is connected to the fuel injection pump housing, and when the engine is rotating at high speed, the second chamber is connected to the return pipe to the fuel tank so that the fuel injection pump housing is connected to the fuel supply pipe. A solenoid-operated piston that is switched to cut off the communication between the second chamber and the return pipe leading to the fuel tank and connect the oil supply pipe leading to the housing of the fuel injection pump when the engine rotates at a low speed. A fuel injection nozzle for a diesel engine, characterized by being equipped with.