JPH0835467A - Fuel injection nozzle for diesel engine - Google Patents

Abstract

PURPOSE:To provide a nozzle hole structure free from fuel leakage and having high implementability. CONSTITUTION:Inner and outer double needle valves 23 and 22 are lifted pertinently under fuel pressure from the fuel passages 26 and 27 thereof, and nozzle holes 24 and 25 laid at internal and external sides in double state are thereby opened and closed. The third fuel passage 29 for supplying fuel synchronously with the feed of the fuel pressure is connected to an inner fuel sump 28 communicated to the inner nozzle hole 24. Also, a division 32 is provided for separating the sump 28 from a pressurizing chamber 31 faced to the pressure receiving surface 30 of the inner needle valve 23.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a fuel injection nozzle for a diesel engine.

[0002]

2. Description of the Related Art Generally, a fuel injection nozzle which operates at a pressure of fuel supplied by an injection pump is used for injecting fuel into a cylinder of a direct injection diesel engine. At the tip of the fuel injection nozzle, there are about 4 to 6 nozzles with a diameter of 0.2 to 0.4 mm arranged at appropriate intervals. The inner diameter of the injection port is closely related to the performance of the engine (fuel consumption, exhaust black smoke concentration, exhaust gas concentration). For example, in a high-speed diesel engine for automobiles, several hundred to 1,000 r
When operating at a low speed of about pm, it is better to reduce the black smoke concentration by reducing the diameter as much as possible, but at a high speed (2,000-3,000rp
In the vicinity of m), if the caliber is small, there is a problem that the fuel injection period becomes too long, the combustion period increases and the fuel efficiency deteriorates. There is. Therefore, if the size of the bore can be selected according to the operating conditions of the engine, it becomes possible to further improve the engine performance especially in the vicinity of low speed and high speed.

From such a consideration, a fuel injection nozzle having a variable nozzle structure as shown in FIG. 6 has been proposed (Japanese Utility Model Laid-Open No. 61-1660). In this fuel injection nozzle, an inner needle valve 4 and an outer needle valve 5, which are double needle valves, are coaxially provided on a nozzle body 3 having a plurality of nozzles 1 and 2 at its tip. The needle valves 4 and 5 are lifted against the springs 8 and 9 by the pressure of the fuel supplied from the oil passages 6 and 7, respectively, so that the needle valves 4 and 5 are arranged with different inner and outer diameters. The nozzle holes 1 and 2 are opened and closed as appropriate. Further, the nozzle holder 10 is provided with a switching valve 11 so that either one of the oil guide passages 6 and 7 is communicated with the fuel supply passage 12 depending on the engine operating state.

[0004]

However, it has been difficult to put this type of fuel injection nozzle into practical use. One of the reasons is the difficulty of partitioning the fuel (preventing fuel leakage) between the inner oil sump 13 and the outer oil sump 14. That is, the fuel flows into the outer oil sump 14 from the outer oil passage 7 at a pressure of several hundreds of atmospheres, which pushes up the outer needle valve 5 and is injected from the outer injection port 2. The partition member 15 must be sealed with a fuel so as not to leak into the inner oil sump 13. The inner oil sump 13 communicates with the drain through the oil guide passage 6 and is in a substantially atmospheric pressure state.

It is generally said that when a metal material is subjected to precision processing for surface contact sealing, the contact pressure of the sealing surface needs to be about 1.5 times the pressure for sealing. Therefore, the spring 1 required to push the partition member 15
The force P of 6 is 1000 kg of fuel pressure when the outer needle valve 5 is opened.
If f / cm ² , the required contact pressure is 15 kgf / mm ² ,
If the sealing surface area is 15.7 mm ² (partition member inner diameter = 4 mm, outer diameter = 6 mm), P = 15.7 mm ² × 15 kgf / mm ² = 23
It will be 5 kgf. It is virtually impossible to install the spring 16 that generates such a strong urging force in the limited space of the inner oil sump 13, and it can be said that such a structure is difficult to realize.

Further, since the above-mentioned conventional fuel injection nozzle is configured to use only one of the injection ports 1 and 2, its variable range is narrow and it is difficult to obtain the optimum injection port area according to the operating condition. there were.

In view of the above circumstances, the present invention provides a fuel injection nozzle of a diesel engine having a highly variable variable nozzle structure with no possibility of fuel leakage, and a fuel that can obtain a more optimal nozzle area according to operating conditions. It was designed to provide an injection nozzle.

[0008]

SUMMARY OF THE INVENTION The present invention is directed to a diesel engine in which inner and outer double needle valves are appropriately lifted by the fuel pressures supplied in respective fuel passages to open and close the injection ports arranged in the inner and outer double. In the fuel injection nozzle, a third fuel passage for supplying fuel in synchronism with fuel pressure supply is connected to the inner fuel reservoir communicating with the inner injection port, and a pressurizing chamber facing the pressure receiving surface of the inner needle valve is provided. A partition is provided to partition the inner fuel pool. It is preferable that the pressurizing chamber is provided with a surface portion formed on the outer needle valve to press the outer needle valve in the nozzle closing direction. It is preferable that the fuel passage includes flow passage switching means for switching the fuel flow passage to independently open and close the injection port.

[0009]

With the above structure, when fuel is supplied to the pressurizing chamber through the inner fuel passage, the pressure acts on the pressure receiving surface of the inner needle valve to lift the inner needle valve and open the inner injection port. At the same time, the fuel supplied through the third fuel passage is injected from the inner injection port. When the fuel is supplied to the outer fuel reservoir through the outer fuel passage, the pressure lifts the outer needle valve to open the outer injection port, and the fuel is injected from the outer injection port together with the fuel from the third fuel passage. Further, due to the structure in which the pressurizing chamber has the surface portion, when the fuel pressure is supplied to the pressurizing chamber, the outer needle valve is pressed in the injection port closing direction to enhance the fuel sealing force. Further, by the structure provided with the flow path switching means, it is possible to perform the injection by using either one of the injection ports and by using both of the injection ports by simultaneously lifting the needle valves.

[0010]

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

FIG. 1 shows an embodiment of a fuel injection nozzle of a diesel engine according to the present invention. The fuel injection nozzle includes an outer needle valve 22 having a hollow shaft center, and an inner needle valve 23 provided at the shaft center position in a nozzle body 21 supported by a nozzle holder (not shown). The double needle valve consisting of is provided so as to be slidable in the vertical direction. An inner injection port 24 and an outer injection port 25 are doubly arranged at the lower end of the nozzle body 21, and the respective needle valves 23, 22 are lifted by the pressure of the fuel supplied by the inner fuel passage 26 and the outer fuel passage 27. Thus, the injection ports 24 and 25 are opened and closed. The third fuel passage 2 for supplying fuel in synchronism with the fuel pressure supply to the inner fuel reservoir 28 communicating with the inner injection port 24 between the outer needle valve 22 and the inner needle valve 23.
9 is connected, the pressurizing chamber 31 facing the pressure receiving surface 30 of the inner needle valve 23 and the inner fuel reservoir 28 are connected to the outer needle valve 22.
A partitioning part 32 for partitioning and is provided.

The lower end portion of the nozzle body 21 is formed in a conical shape with a downward constriction, the axial center portion 33 is bulged in a dome shape, and a substantially hemispherical small chamber 34 is defined inside thereof. . A plurality of inner injection holes 24 are formed extending obliquely downward and radially from the small chamber 34. These inner nozzles 2
No. 4 is formed with a relatively large diameter that provides good combustion in the high speed rotation range. The inner needle valve 23 is composed of a rod member having a right cylindrical shape having a predetermined outer diameter, and the lower end 3
5 is formed in a conical shape with a downward constriction, and comes into contact with the peripheral edge of the small chamber 34 by line contact. The inner needle valve 23
A piston body 36 having an outer diameter sufficiently larger than the outer diameter of the inner needle valve 23 is attached to the upper end of the rod member 38, and a rod member 38 is fitted to a protrusion 37 formed at the axial center position of the upper surface of the piston body 36 to stand upright. Has been done. An inner spring 39 for urging the inner needle valve 23 downward is provided above the rod member 38, and a stopper 40 is provided inside the spring 39 at a predetermined distance from the head of the rod member 38. Is provided.

The outer injection holes 25 are arranged at a predetermined interval in the circumferential direction on the inclined portion 41 at the lower end of the nozzle body 21, and extend obliquely downward like the inner injection holes 24.
Its diameter is smaller than that of the inner injection port 24 so that good combustion is achieved in the low speed rotation range. The outer needle valve 22 has an outer peripheral surface 42 that slides on the inner wall of the nozzle body 21, and an axial inner wall 43 that is separated from the outer peripheral surface of the inner needle valve 23 by a predetermined distance. The tip of the outer needle valve 22 is formed as a valve end surface 44 having an inclination angle equal to the inclination angle of the seat portion 57 that is the inner surface of the lower end portion of the nozzle body 21, and the outer injection port 25 is closed by making surface contact with the seat portion 57. It has become. A pressure receiving surface 45 facing the seat 57 of the nozzle body 21 substantially in parallel is formed in a step shape on the outer periphery above the tip of the outer needle valve 22. An outer spring 46 that urges the outer needle valve 22 downward is provided on the upper end of the outer needle valve 22, and a ring member 47 that engages with one end of the outer spring 46 is fitted. Further, the upper end portion of the shaft-side inner wall 43 is enlarged in diameter to slidably surround the outer peripheral surface of the piston body 36.

The inner fuel passage 26 has an oil guide passage 48 extending obliquely downward from the upper end of the nozzle body 21 to the axial center side, and an inner port 49 formed in the outer needle valve 22 extending radially from the opening position. And the inner end of the inner port 49 faces the pressure chamber 31 and is open. The pressurizing chamber 31 is defined by the lower surface of the piston body 36, which is the pressure receiving surface 30 of the inner needle valve 23 at the upper side, and laterally by the shaft-side inner wall 43 of the outer needle valve 22 and its enlarged diameter portion 50. , Expanded part 5
A surface portion 5 whose lower end of 0 directly faces the pressure receiving surface 30 of the inner needle valve 23
1 is formed in a step shape. And the partition 32 is
Near the opening of the inner port 49, it projects from the shaft-side inner wall 43 in a trapezoidal cross section, and is formed over a predetermined length in the vertical direction. The protruding end surface is in sliding contact with the outer circumference of the inner needle valve 23. The partition 32 may be formed by partially expanding the inner needle valve 23, or may be projected from both the outer needle valve 22 and the inner needle valve 23.

The third fuel passage 29 is the inner fuel passage 26.
In the same manner as the above, the oil guide path 52 extends obliquely downward from the upper end of the nozzle body 21 toward the axial center, and the common port 53 formed in the outer needle valve 22 extending in the radial direction from the opening position. The inner end of the common port 53 opens to the shaft-side inner wall 43 at a position below the partition 32. The outer fuel passage 27 is formed by an oil guide passage 54 that extends obliquely downward from the upper end of the nozzle body 21, and the pressure receiving surface 4 of the outer needle valve 22.
It communicates with the outer fuel pool 56 defined between the lower outer peripheral surface 55 including 5 and the inner wall of the nozzle body 21.

As shown in FIG. 2, each fuel passage 26, 2
7, 29 are connected to the fuel supply passage 61 from the injection pump. The fuel supply path 61 is branched on the way, one branch path 62 is connected to the third fuel path 29, and the other branch path 63 is further branched into two branch paths 64, 65. , The inner fuel passage 26 and the outer fuel passage 27, respectively. And this branch 6
A switching valve 66 is provided at the branch portions of the valves 4, 65, and the fuel F pressure-fed from the injection pump is made to flow to either one of them in accordance with the operating state of the engine. That is,
During high speed rotation, the fuel flows to the inner fuel passage 26 and the third fuel passage 29 (f ₁ , f ₃ ), and at low speed rotation to the outer fuel passage 27 and the third fuel passage 29 (f ₂ , f ₃ ). Each will flow.

Next, the operation of this embodiment will be described.

At the time of high speed rotation, the switching valve 66 is operated to the communication side of the inner fuel passage 26, and the fuel of the predetermined pressure and quantity is pumped to the third fuel passage 29 and the inner fuel passage 26 by the fuel injection pump. . The fuel f ₁ from the inner fuel passage 26 is supplied to the pressurizing chamber 31 through the inner port 49 as shown in FIG. 3 (a), and the pressure overcomes the biasing force of the inner spring 39 to force the piston body 36 to move. Push up,
The inner needle valve 23 is lifted. As a result, the inner injection port 24 is opened, and the fuel f ₃ supplied from the common port 53 is injected from the inner injection port 24 via the inner fuel reservoir 28. The fuel pressure supplied to the pressurizing chamber 31 is the outer needle valve 2
It also acts on the second surface portion 51 to press the outer needle valve 22 downward to increase the contact pressure at the valve end surface 44.

Further, at the time of low speed rotation, the switching valve 66 is switched to pump the fuel into the outer fuel passage 65. This fuel f
_As shown in FIG. 3 (b), ₂ is supplied to the outer fuel pool 56, and the pressure thereof lifts the outer needle valve 22 and opens the outer injection port 25. Then, it merges with the fuel f ₃ from the common port 53 and is injected from the outer injection port 25. At this time, the fuel also flows into the inner fuel reservoir 28, but the supplied predetermined amount (f ₂ + f ₃ ) is completely injected, and it is separated from the pressurizing chamber 31 by the partition 32. , Does not act in the direction of lifting the inner needle valve 23. Further, the fuel in the pressurizing chamber 31 is drained via the inner port 49.

As described above, the third fuel passage 29 is connected to the inner fuel reservoir 28, and the partition 32 is provided along the inner needle valve 23.
Since the pressurizing chamber 31 and the inner fuel sump 28 are separately formed vertically, the fuel injection nozzle having a double needle valve that does not leak fuel when any of the needle valves 22 and 23 is lifted. Can be achieved, and the engine performance at low speed and high speed operation can be improved by selecting the injection port according to the operating state of the engine. Further, since the surface portion 51 is formed on the outer needle valve 22 to press the outer needle valve 22 downward simultaneously with the lift of the inner needle valve 23, the contact pressure of the outer needle valve 22 can be increased, and the high speed operation can be achieved. It is possible to more completely prevent fuel leakage from occurring.

When the outer needle valve 22 is lifted, the fuel pressure also acts on the lower end 35 of the inner needle valve 23, but there is no risk of affecting the seal. That is, the valve opening set pressure of the inner needle valve 23 is 200 kgf / cm ² , and the outer diameter of the piston body 36 is 6 m.
m, 2.5 mm body outside diameter of the inner needle valve 23, when the 1.0mm inner diameter of chamber 34, the area of the pressure receiving surface 30 is 23.9 mm ^2, the tip cross-sectional area 4.4 mm ² next to the inner needle valve 22, outer fuel The fuel pressure due to the fuel f ₂ from the passage 27 is 1,100 kgf / cm ² (200
kgf / cm ² × 23.9 / 4.4) If the range is up to approx.
3 does not open to cause fuel leakage. In other words, by appropriately selecting the piston body 36 (pressure receiving surface 30), the valve opening set pressure (spring force) can be made large, and the contact pressure at the line contact of the inner needle valve 23 can be made sufficiently large. .

Next, another embodiment of the present invention will be described with reference to FIG. In this embodiment, the fuel supply passage 61 is used as the passage switching means 70 for appropriately supplying the fuel to the fuel passages 26, 27, 29 in the fuel injection nozzle of the embodiment.
Are formed by branching in three directions, of which the inner fuel passage 2
6 and the branch passages 71, 72 connected to the outer fuel passage 27
Further, electromagnetic opening / closing valves 73 and 74 are provided. The branch passage 75 connected to the third fuel passage 29 is in constant communication with the fuel supply passage 61. The electromagnetic on-off valves 73 and 74 are controlled to be opened and closed by a controller (not shown) into which the operating state of the engine is input.

A control map as shown in FIG. 5 is stored in the controller. In this control map, the engine is divided into three zones according to the engine rotation and the load, and it is assumed that the nozzle area is increased as the speed and the load shift. That is, in the low speed region A, the outer fuel passage 2
7, the electromagnetic on-off valve 74 of 7 is opened and the electromagnetic on-off valve 73 of the inner fuel passage 26 is closed, so that fuel injection is performed by the outer injection port 25, and the outer fuel passage 27 is formed in the medium to high speed B region. The electromagnetic opening / closing valve 74 is closed and the electromagnetic opening / closing valve 73 in the inner fuel passage 26 is opened so that the fuel is injected from the inner injection port 24. Then, when the engine operation enters the high speed / high load C region on the control map, both the electromagnetic opening / closing valves 73 and 74 are opened. In this state, the fuel flows through all the fuel passages 26, 27,
29, and both outer needle valve 22 and inner needle valve 23 are lifted. At this time, a force acts to seat the outer needle valve 22 on the seat portion 57 on the pressure receiving surface 51 of the pressurizing chamber 31, but since the pressure receiving surface 45 of the outer needle valve 22 has a larger area, the outer fuel reservoir The ascending force due to the fuel pressure of 56 exceeds,
The outer needle valve 22 is lifted. As a result, fuel is injected from the outer injection port 25 and the inner injection port 24 at the same time.

In this way, the branch passages 71, 7 are provided in the fuel passages 26, 27, 29 for appropriately lifting the needle valves 22, 23.
2, 75 and electromagnetic on-off valves 73, 74 are provided, and the respective fuel outlets 24, 25 are opened and closed independently by appropriately switching the fuel flow paths. It is possible to switch to three stages of the individual 24, the total of the outer nozzle 25 and the inner nozzle 24, and a variable nozzle control with a wide variable width or a finer variable variable nozzle control is achieved. That is, it is possible to make a more optimal injection port area according to the operating state.

Although the outer injection port 25 has a small diameter and the inner injection port 24 has a large diameter in the above embodiment, the outer injection port 25 may have a large diameter and the inner injection port 24 may have a small diameter. Further, the switching valve 66 and the solenoid opening / closing valve 73,
The nozzle 74 may be provided on the nozzle holder or outside the nozzle, and any element may be used as long as it can switch the flow path according to the engine operating state.

[0026]

In summary, according to the present invention, the following excellent effects are exhibited.

(1) According to the configuration of claim 1, it is possible to achieve a fuel injection nozzle having a double needle valve that does not leak fuel when any of the needle valves is lifted. Improvement of engine performance at low speed and high speed operation is realized by selecting the injection port.

(2) According to the second aspect of the invention, the contact pressure of the outer needle valve can be increased, and fuel leakage during lift of the inner needle valve can be more completely prevented.

(3) According to the configuration of the third aspect, it is possible to obtain a more optimum injection port area according to the operating condition.

[Brief description of drawings]

FIG. 1 is a side sectional view showing an embodiment of a fuel injection nozzle of a diesel engine according to the present invention.

FIG. 2 is a configuration diagram showing a fuel supply path of FIG.

FIG. 3 is a diagram for explaining the operation of FIG. 1, (a)
Is a side sectional view of the main part showing a state in which the inner needle valve is lifted,
FIG. 7B is a side sectional view of a main part showing a state in which the outer needle valve is lifted.

FIG. 4 is a configuration diagram of a fuel supply path showing another embodiment of the present invention.

5 is a control map for explaining the operation of FIG. 4. FIG.

FIG. 6 is a side sectional view showing a fuel injection nozzle of a conventional diesel engine.

[Explanation of symbols]

 22 outer needle valve 23 inner needle valve 24 inner nozzle 25 outer nozzle 26 inner fuel passage 27 outer fuel passage 28 inner fuel reservoir 29 third fuel passage 30 pressure receiving surface 31 pressurizing chamber 32 partition 51 surface portion 70 flow path switching means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoichi Hatanaka No. 8 Tsutana, Fujisawa, Kanagawa Prefecture Isuzu Central Research Institute (72) Inventor Shiro Ishida No. 8 Shelf, Fujisawa, Kanagawa Isuzu Central Research Co., Ltd. In-house

Claims (3)

[Claims] 1. A fuel injection nozzle for a diesel engine, wherein an inner and an outer double needle valve are appropriately lifted by fuel pressures supplied in respective fuel passages to open and close an injection port arranged in an inner and outer double. A third fuel passage for supplying fuel in synchronism with the fuel pressure supply is connected to the inner fuel reservoir communicating with the injection port, and the inner fuel reservoir is separated from the pressure chamber facing the pressure receiving surface of the inner needle valve. A fuel injection nozzle for diesel engines, characterized by having a partition. 2. The fuel injection nozzle for a diesel engine according to claim 1, wherein the pressurizing chamber includes a surface portion formed on the outer needle valve to press the outer needle valve in the injection port closing direction. 3. The fuel injection nozzle for a diesel engine according to claim 1, wherein the fuel passage includes flow passage switching means for switching a fuel flow passage so as to independently open and close the injection port.