JP2512427Y2 - Fuel injection nozzle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a fuel injection nozzle used in a diesel engine.

[Prior Art] Some fuel injection nozzles are configured to inject a main fuel and an auxiliary fuel for supporting combustion of the main fuel. For example, when using methanol, which has poor ignitability, as a fuel for a diesel engine, light oil with good ignitability is first pilot injected to ignite, and then methanol is injected to ignite. In this case, a fuel injection nozzle capable of injecting both methanol as a main fuel and light oil as an auxiliary fuel is used.

A conventional fuel injection nozzle of this type is disclosed in JP-A-61-93265.
Japanese Patent Laid-Open No. 2-33463 and the like.

In the fuel injection nozzle disclosed in JP-A-61-93265, a main fuel passage is provided in the nozzle body, and the main fuel passage is opened and closed by a needle valve, and the needle valve is opened at the tip of the needle valve. Then, an auxiliary fuel passage for light oil that is connected to the main fuel passage is provided, and a check valve that prevents the reverse flow of fluid from the main fuel passage to the auxiliary fuel passage is provided. In this fuel injection nozzle, the check valve is pushed open by the pressure of light oil that is the auxiliary fuel to open the auxiliary fuel passage, and light oil is injected from the injection hole provided at the tip of the nozzle body. The main fuel passage is opened by pushing up the needle valve with a certain pressure of methanol, and methanol is injected from the injection hole.

Further, in the fuel injection nozzle disclosed in JP-A-2-33463, a main fuel passage is provided in the nozzle body, the main fuel passage is opened and closed by the first needle valve, and the inside of the first needle valve is provided. An auxiliary fuel passage is provided and a second needle valve that opens and closes the auxiliary fuel passage is arranged. The first needle valve and the second needle valve are pressed and biased toward the seat portion by independent springs. In this fuel injection nozzle, the auxiliary needle passage is opened by pushing up the second needle valve with the pressure of the auxiliary fuel gas oil, and the diesel fuel is injected from the injection hole provided at the tip of the first needle valve protruding from the nozzle body. Is injected and the first needle valve is pushed up by the pressure of methanol as the main fuel to open the main fuel passage, and methanol is injected from another injection hole provided at the tip of the nozzle body.

[Problems to be Solved by the Invention] However, both of the above-mentioned conventional fuel injection nozzles have a drawback that the internal structure becomes very complicated.

In both fuel injection nozzles, the injection timing of methanol, which is the main fuel, and the injection timing of light oil, which is the auxiliary fuel, must be controlled separately, so that the control mechanism becomes very complicated and both injections are performed. However, there is a drawback that it is difficult to set a delicate time difference accurately.

The present invention has been made in view of the above-mentioned problems of the conventional technology, and the purpose thereof is to have a simple structure,
An object of the present invention is to provide a fuel injection nozzle that can easily control the injection timing of the main fuel and the auxiliary fuel.

[Means for Solving the Problems] The present invention has been made in order to achieve the above object, and its gist is to inject a main fuel and an auxiliary fuel for supporting the combustion of the main fuel. In a fuel injection nozzle, a needle valve is slidably inserted in a sliding hole of a nozzle body in an axial direction thereof, and the needle valve includes a main fuel passage formed inside along the axial direction and one end. Has an injection hole that is open to the sliding surface with respect to the nozzle body and the other end is connected to the main fuel passage, while the nozzle body is positioned at the tip end portion radially outside of the opening end of the sliding hole. The seat portion and the auxiliary fuel passage having one end opened at the connecting surface connecting the seat portion and the sliding hole, and the head portion of the needle valve protruding from the sliding hole is seated on the seat portion. The valve is closed by The pressure causes the needle valve to move toward the tip side in the axial direction, and the head portion separates from the seat portion, thereby opening the valve.In this valve open state, the head portion separates from the seat portion and at the same time Auxiliary fuel is injected from between the seat portion, and thereafter, when the head portion moves a predetermined distance from the seat portion, the injection hole is exposed from the opening end of the sliding hole and the main fuel is injected from the injection hole. And in the fuel injection nozzle.

[Operation] The control of the opening / closing operation of the fuel injection nozzle can be performed only by controlling the pressure of the main fuel.

When the head portion of the needle valve is separated from the seat portion of the nozzle body, the auxiliary fuel is injected through the gap. on the other hand,
Even if the head part of the needle valve separates from the seat part of the nozzle body and opens, the main fuel slides on the needle valve until just before the nozzle hole of the needle valve is exposed from the sliding hole of the nozzle body. Only a small amount of main fuel is injected through the extremely narrow gap between the holes, but when the injection hole is exposed from the sliding hole, a large amount of main fuel is injected vigorously from the injection hole. .

The time difference between the start timing of the large amount injection of the main fuel and the injection start timing of the auxiliary fuel is determined by setting a predetermined distance between the opening end of the sliding hole and the injection hole in the needle valve axis direction when the valve is closed. It can be set as desired and accurately.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings from FIG. 1 to FIG. In this example, methanol, which is the main fuel and has poor ignitability, and auxiliary fuel (auxiliary fluid)
Is a mode of a fuel injection nozzle for a diesel engine that injects light oil having good ignitability.

FIG. 1 is a vertical cross-sectional view of the fuel injection nozzle 1, and FIG. 2 is an enlarged vertical cross-sectional view of the tip portion thereof. Fuel injection nozzle 1
Has a nozzle body 2, a nozzle holder 3 and a needle valve 4. An intermediate plate 5 is sandwiched between the nozzle body 2 and the nozzle holder 3, and the nozzle body 2 is connected and fixed to the nozzle holder 3 by a nozzle nut 6. The nozzle body 2 has a sliding hole 7 extending in the axial direction from the base end surface toward the tip.
have. The opening end of the sliding hole 7 on the tip side is connected to a tapered surface (connection surface) 8 provided on the tip of the nozzle body 2 and gradually increasing in diameter as it approaches the tip.
A peripheral portion of the tapered surface 8 on the tip end side is a seat portion 9 for the needle valve 4. Further, the nozzle body 2 is provided with four auxiliary fuel passages 10 arranged at equal intervals in the circumferential direction. Each auxiliary fuel passage 10 has one end opened to the base end surface of the nozzle body 2 and the other end opened to the tapered surface 8.

The needle valve 4 is slidably inserted in the sliding hole 7 of the nozzle body 2 in the axial direction thereof. The needle valve 4 has a rod portion 11
And a head portion 12 formed at the tip of the rod portion 11 and having a diameter larger than that of the rod portion 11, and the head portion 12 is projected outward from the opening end of the sliding hole 7. The head part 12 is
In the valve closed state shown in FIG. 2, the seat portion 9 of the nozzle body 2 is seated. At this time, the head portion is seated.
A wedge-shaped gap is formed between the nozzle 12 and the tapered surface 8 of the nozzle body 2. Needle valve 4 rod part 11
The base end side of the is penetrated through the slide hole 7 and further through the intermediate plate 5, and is inserted into the pressure chamber 13 provided in the nozzle holder 3. The needle valve 4 is formed with a main fuel passage 14 extending in the axial direction from the base end surface of the rod portion 11 toward the tip thereof, and the tip of the main fuel passage 14 reaches the head portion 12. In the portion of the rod portion 11 located in the vicinity of the head portion 12, injection holes 15 having one end opened to the outer peripheral surface of the rod portion 11 and the other end connected to the main fuel passage 14 are provided at equal intervals in the circumferential direction.
Is formed. The above-mentioned one end opening 16 of each injection hole 15 is the second
In the valve-closed state shown in the figure, the sliding hole 7 is positioned at a predetermined dimension (hereinafter, referred to as a throttle length) L from the opening end of the sliding hole 7 toward the base end side in the axial direction. In this embodiment, the injection hole 15 and the front end side opening of the auxiliary fuel passage 10 in the nozzle body 2 are arranged at the same position in the circumferential direction, but the invention is not limited to this.

On the other hand, the needle valve 4 inserted in the pressure chamber 13 of the nozzle holder 3
The rod portion 11 penetrates the maximum lift adjusting shim 17 and the sleeve 18 housed in the pressure chamber 13. Further, a stopper 19 is non-removably fitted on the base end of the rod portion 11. The needle valve 4 is biased in a direction approaching the nozzle holder 3 (upward in FIG. 1) by a nozzle spring 20 interposed between a sleeve 18 and a stopper 19, which normally closes the valve. It is supposed to be maintained. The valve opening pressure of the needle valve 4 is set as desired by interposing a valve opening pressure adjusting shim 21 between the stopper 19 and the nozzle spring 20. The maximum lift of the needle valve 4 is restricted by the stopper 19 hitting the upper end of the sleeve 18.

Further, the nozzle holder 3 is provided with a main fuel passage 22 and an auxiliary fuel passage 23. The main fuel passage 22 extends from the base end surface of the nozzle holder 3 toward the tip and is continuous with the pressure chamber 13. The outer peripheral surface of the base end portion of the nozzle holder 3 has a male screw portion 24.
And the other end of a main fuel supply pipe (neither of which is shown) whose one end is connected to the main fuel injection pump is connected thereto. The auxiliary fuel passage 23 has one end connected to a screw hole 25 provided in the base end portion 7 of the nozzle holder 3 and the other end opened to the tip surface of the nozzle holder 3.
The screw hole 25 is connected to the other end of an auxiliary fuel supply pipe (none of which is shown), one end of which is connected to the auxiliary fuel injection pump. The auxiliary fuel passage 23 of the nozzle holder 3 is connected to each auxiliary fuel passage 10 of the nozzle body 2 via an annular passage 26 formed in the intermediate plate 5.

In this embodiment, the diesel fuel having a substantially constant pressure is constantly pumped to the auxiliary fuel passages 10 and 23, while the methanol is pumped to the main fuel passages 14 and 22 in a predetermined cycle. ing. The pressure of light oil is lower than the pressure of methanol in the main fuel passages 14 and 22 when the valve is closed,
Further, the needle valve 4 can be lifted only by the increase in the pressure of methanol.

Next, the operation of the fuel injection nozzle 1 will be described.

When the pressure of methanol in the pressure chamber 13 is equal to or lower than the valve opening pressure, the head portion 12 of the needle valve 4 is seated on the seat portion 9 of the nozzle body 2 by the urging force of the nozzle spring 20, and the valve closed state is maintained. At this time, a force due to the pressure of light oil acts on the head portion 12, but the force is weak and cannot lift the needle valve 4. Since the pressure of light oil is lower than the pressure of methanol, the light oil passes through the injection hole 15 through the slight gap between the rod portion 11 of the needle valve 4 and the sliding hole 7 and the main fuel passage 10
There is no backflow inside. On the contrary, when there is a risk that methanol will flow back into the auxiliary fuel passages 10 and 23, a check valve is provided in either the auxiliary fuel passage 10 or 23.

Next, when the pressure of methanol in the pressure chamber 13 rises above the valve opening pressure due to the pressure feed of methanol from the main fuel injection pump, the needle valve 4 begins to move downward against the biasing force of the nozzle spring 20, and the head The part 12 is separated from the seat part 9 to open the valve.

At the same time when the head portion 12 separates from the seat portion 9, injection of light oil is started. At this time, the injection shape of light oil spreads like a bowl and forms a film. Light oil has good ignitability, so
When injected into a combustion chamber (not shown), it is quickly ignited and starts burning.

On the other hand, in the case of methanol, from the time when the head portion 12 separates the seat portion 9 to the time when it descends by the throttle length L, that is, as shown in FIG. 3, the lower end of the opening 16 of the injection hole 15 is a sliding hole. Until just before protruding from 7, the opening 16 is closed by the inner peripheral surface of the sliding hole 7, so that the injection hole 15 does not directly inject methanol into the combustion chamber. However, as long as the rod portion 11 of the needle valve 4 is slidable in the sliding hole 7, the outer peripheral surface of the rod portion 11 and the inner peripheral surface of the sliding hole 7 are not completely in close contact with each other. There is a very small gap between them. Therefore, while the needle valve 4 is lowered by the throttle length L, a slight amount of methanol is injected from the opening end of the sliding hole 7 from the injection hole 15 through the above gap, and this is the tapered surface 8 of the nozzle body 2 and the head. The fuel is injected into the combustion chamber from between the parts 12 (hereinafter referred to as the primary injection [I] of methanol). The first injection [I] is
It has the characteristics that the penetrating power is small and the injection rate is low, and the injection shape spreads in a bowl shape to form a film shape as shown in FIG. Methanol, which has poor ignitability, has a low injection rate in the first injection [I] and is injected while the light oil is already burning, so the methanol in the first injection [I] is quickly ignited. Start burning.

Then, as shown in FIG. 3, after the lower end of the opening 16 of the injection hole 15 reaches the opening end of the sliding hole 7 and the needle valve 4 further descends, the opening 16 is gradually exposed and finally As shown in FIG. 4, the opening 16 is completely exposed from the sliding hole 7 and a large amount of methanol is directly injected from the injection hole 15 into the combustion chamber (hereinafter, this will be described below). The second injection of methanol [II]). The drawings in FIGS. 7 to 9 show the growth process of the secondary injection [II] of methanol. The secondary injection [II] is characterized in that it has a larger penetration force and a higher injection rate than the primary injection [I], and the injection shape does not spread like the primary injection [I]. It has a strong convergence. The secondary injection [II] methanol is injected while the light oil and the primary injection [I] methanol are burning, so that the secondary injection [II] methanol is quickly ignited to start combustion.

FIG. 5 compares the injection of light oil with the primary injection [I] and the secondary injection [II] of methanol with the horizontal axis representing the cam angle and the vertical axis representing the penetration force. , Angle α is a cam angle corresponding to the throttle length L. In the figure, the broken line represents light oil, the chain double-dashed line represents the primary injection of methanol, and the solid line represents the secondary injection of methanol. As can be seen from this figure, the penetrating force of light oil is set to be larger than the penetrating force of methanol in the primary injection [I] and smaller than the penetrating force of methanol in the secondary injection [II]. Also, the sixth
The states of injection of methanol shown in FIGS. 9 to 9 correspond to points A, B, C, and D in FIG. 5, respectively.

As described above, in this fuel injection nozzle 1, first, light oil is injected and a small amount of methanol is injected with the injection rate kept low, and the ignition and combustion of methanol is induced by the combustion of light oil with good ignitability. In addition, while these light oil and methanol are burning, the injection rate is increased and a large amount of methanol is injected, and this methanol is ignited and burned. Get burned. As a result, it is possible to increase the output of the engine, improve quietness, and purify exhaust gas.

Further, in the case of this fuel injection nozzle 1, the valve opening / closing operation can be performed only by controlling the pressure of methanol, which is the main fuel, so the control mechanism is greatly simplified. Furthermore,
By changing the throttle length L, the injection rate of the primary injection [I] of methanol can be adjusted appropriately, and there is a slight difference from the start of injection of light oil to the start of the secondary injection of methanol [II]. The time difference can be set accurately.

This invention is not limited to the above embodiment, and various modes can be adopted.

For example, in the embodiment, light oil, which is the auxiliary fuel, is constantly fed to the auxiliary fuel passage at a substantially constant pressure.
The auxiliary fuel may also be pressure-fed in a predetermined cycle like the main fuel.

Further, the number of injection holes and the number of auxiliary fuel passages do not necessarily have to be the same, and the numbers may be different.

Further, the main fuel is not limited to methanol and may be ethanol or the like, and the auxiliary fuel is not limited to light oil and may be A heavy oil or the like.

[Advantages of the Invention] As described above, according to the fuel injection nozzle of the present invention, both the main fuel and the auxiliary fuel can be injected and the main fuel can be satisfactorily burned although the structure is simple. That is an excellent effect.

Further, the opening / closing operation of the fuel injection nozzle can be performed only by controlling the pressure of the main fuel. Furthermore, the delicate time difference between the injection timings of the main fuel and the auxiliary fuel depends on the opening end of the sliding hole and the injection hole when the valve is closed. Since it is possible to set a desired and accurate setting by setting a predetermined distance between the needle valve and the needle valve in the axial direction,
The excellent effect that the control mechanism can be greatly simplified is exhibited.

[Brief description of drawings]

1 to 9 show an embodiment of the present invention. FIG. 1 is a vertical cross-sectional view of a fuel injection nozzle, and FIG. 2 is an enlarged view of the nozzle tip portion showing a valve closed state. Longitudinal section,
3 and 4 are enlarged vertical sectional views corresponding to FIG. 2 showing the valve open state of the nozzle, respectively, and FIG. 5 is a graph in which the horizontal axis represents the cam angle and the vertical axis represents the penetrating force of the injected fuel. FIG. 6 to FIG. 9 are views showing the state of main fuel injection at the time points corresponding to points A to D in FIG. 1 ... Fuel injection nozzle, 2 ... Nozzle body, 4 ... Needle valve, 7 ... Sliding hole, 8 ... Tapered surface (connection surface), 9 ...
Seat, 10 …… Auxiliary fuel passage, 12 …… Head, 14
...... Main fuel passage, 15 …… Injection hole.

Claims (1)

(57) [Scope of utility model registration request] 1. A fuel injection nozzle for injecting main fuel and for injecting auxiliary fuel for supporting combustion of the main fuel, wherein a needle valve is slidable in an axial direction of a sliding hole of a nozzle body. This needle valve has a main fuel passage formed inside along the axial direction, and an injection hole having one end opened to the sliding surface for the nozzle body and the other end connected to the main fuel passage. On the other hand, the nozzle body has a seat portion located radially outside the opening end of the sliding hole at its tip and a connecting surface connecting the seat portion and the opening end of the sliding hole. And the auxiliary fuel passage which is opened, and the head portion of the needle valve protruding from the sliding hole is seated on the seat portion to close the valve, and the main valve pressure causes the needle valve to tip in the axial direction. It is moved to the side and the head part is the seat The valve is opened by being separated from the seat portion.In this valve open state, the head portion is separated from the seat portion, and at the same time, auxiliary fuel is injected from between the head portion and the seat portion, and then the head portion is separated from the seat portion by a predetermined distance. A fuel injection nozzle, wherein the injection hole is exposed from the opening end of the sliding hole and the main fuel is injected from the injection hole when moved.