JPH08261111A - Fuel injection nozzle of diesel engine - Google Patents

Abstract

PURPOSE: To restrain the initial injection rate in a fuel injection nozzle, and reduce the emission of NOx and the combustion noise while preventing the exhaust of black smoke from becoming worse. CONSTITUTION: The fuel injection nozzle of a diesel engine is constituted in such a way that a cylindrical small-diameter part 8 to be fittedly inserted into the inside diameter of a sack part 4 is formed at the end part of the needle valve 2 that has been internally provided in the nozzle body 1 so as to be liftable, and the small-diameter part 8 directly closes the injection holes 3 when the lift of the needle valve is zero, and the effective area of the injection holes 3 is increased as the needle valve 2 is gradually lifted, and that a circumferential groove 5 all around the base part of the small-diameter part 8 and a fuel introducing passage 6 for communicating the circumferential groove 5 with the end inside of the sack part 4 area formed so as to communicate the end inside of the sack part 4 with the fuel passage inside the nozzle body 1. Thereby, the reduction of the fuel injection pressure in the initial stage of injection can be prevented, and grain diameter of the fuel spray particle becomes smaller for accelerating the production of mixture with air, so that the combustion of the engine can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection nozzle for a diesel engine, and more particularly to a technique for suppressing an initial injection rate.

[0002]

2. Description of the Related Art It is known that suppression of a fuel injection rate (initial injection rate) during an ignition delay period is effective as a means for reducing NOx emission and combustion noise of a diesel engine. As a method to realize, for example,
A throttle hole nozzle as shown in FIG. 7 is known. In this nozzle, the initial injection rate is suppressed by the throttle effect of the throttle.

Further, as shown in FIG. 9, there is also a fuel injection nozzle in which a sub injection hole 9 is provided in the fuel injection nozzle to obtain the effect of suppressing the initial injection rate.

[0004]

By the way, as shown in FIG.
In the throttle hole nozzle shown in Fig. 8, at the initial stage of injection, the fuel flow passage area of the throttle (flow passage area throttle) portion is smaller than the effective injection hole area of the nozzle as shown in Fig. 8. ) Is decreased, the inhibition of atomization of the spray and the promotion of mixing with air are deteriorated, and NOx is reduced, but there is a problem that black smoke emission is increased.

Further, in the nozzle shown in FIG. 9 in which the sub injection hole 9 is provided in the fuel injection nozzle, a pressure loss occurs between the main injection hole 3 and the sub injection hole 9, and the fuel pressure in the injection hole on the downstream side is increased. Since the (injection pressure) is reduced, NOx is reduced in the downstream injection hole for the same reason as the throttle hole nozzle, but there is a problem that black smoke emission is increased.
Therefore, in view of the conventional problems as described above, the present invention changes the effective injection hole area of the nozzle in accordance with the lift amount of the needle valve in the multiple injection hole fuel injection nozzle by slightly improving the fuel injection nozzle. In this way, it is an object of the present invention to make it possible to suppress the initial injection rate without using the flow passage area restriction.

[0006]

Therefore, according to the invention as set forth in claim 1, in the multi-hole fuel injection nozzle, the needle valve tip internally provided so as to be liftable on the nozzle body is a sack of the tip of the nozzle body. It is formed in a cylindrical small-diameter portion that is inserted into the inner diameter of the portion, and the small-diameter portion directly closes the injection hole of the peripheral wall of the sack portion when the lift amount of the needle valve is 0, and gradually opens as the lift is made. In addition to increasing the area, in order to connect the inside of the tip of the sack portion with the fuel passage in the nozzle body, a circumferential groove that covers the entire circumference of the base of the small diameter portion, and a fuel introduction passage that connects the circumferential groove and the inside of the tip of the sack portion And a diesel engine fuel injection nozzle provided with.

According to a second aspect of the present invention, there is provided a fuel injection nozzle for a diesel engine according to the first aspect, wherein each of the injection holes provided in the peripheral wall of the sack portion has a different cross-sectional shape in accordance with required nozzle characteristics. did. The invention according to claim 3 is the diesel engine according to claim 1 or 2, wherein the positions of the respective injection holes provided in the peripheral wall of the sack portion are set at positions displaced from each other in the nozzle axial direction according to the required nozzle characteristics. The fuel injection nozzle of the engine.

[0008]

According to the first aspect of the invention, the initial injection rate of fuel can be suppressed, the particle size of fuel spray is reduced, and the generation of air-fuel mixture is promoted. NOx emission and combustion noise can be reduced while preventing the above. According to the invention described in claim 2, in addition to the operation of the invention described in claim 1, the required nozzle characteristics are variously changed, so that the fuel injection nozzle can obtain an initial fuel injection rate more suited to the engine characteristics. You can

According to the invention of claim 3, claim 1
In addition to the operation of the invention described above, the required nozzle characteristics become gentle and stepwise, so that the fuel injection nozzle can obtain an initial fuel injection rate that better matches the engine characteristics.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. FIG. 1A shows the structure of the fuel injection nozzle according to claim 1 of the present invention. The fuel injection nozzle is composed of a nozzle body 1 and a needle valve 2 installed inside the nozzle body 1 so as to be liftable. A plurality of injection nozzles are provided on the peripheral wall of a sack portion 4 at the tip of the nozzle body 1. The hole 3 is formed as shown in a cross section BB shown in FIG. The injection hole 3 is composed of five through holes that penetrate the peripheral wall of the sack portion 4 at equal intervals. The number of injection holes 3 is not limited to five. The tip of the needle valve 2 is formed into a cylindrical small-diameter portion fitted into the inner diameter of the sack portion 4, and the small-diameter portion 8 has a lift amount of the needle valve 2 (hereinafter referred to as a needle lift amount). At 0, injection hole 3
1 (b) so that the effective area of the injection hole 3 is increased as the needle valve is gradually lifted, and the inside of the tip of the sack portion 4 and the fuel passage of the nozzle body 1 are communicated with each other. ) Small diameter part 8 as shown in cross section AA
A peripheral groove 5 is formed over the entire circumference of the base portion, and a fuel introduction passage 6 that communicates the peripheral groove 5 with the inside of the tip of the sack portion 4 is formed.
The fuel introduction passage 6 has a central hole 6a which extends along the central axis of the small-diameter portion 8 from the position corresponding to the position where the circumferential groove 5 is formed to the front end surface and is open, and the circumferential direction of the inner circumferential surface of the circumferential groove 5. And four side holes 6b that extend in the direction perpendicular to the axis and communicate with the central hole 6a from four positions that are equally spaced apart from each other.
The number of side holes 6b is not limited to four.

Next, the operation of the fuel injection nozzle of the present invention will be described. When the needle lift amount is 0, the fuel flow passage is closed by the valve seat portion 7 of the needle valve 2 and the injection hole 3 is closed by the small diameter portion 8. At the beginning of fuel injection, when the needle valve 2 starts to lift, the fuel passage of the valve seat portion 7 opens,
The fuel is injected from the injection hole 3 through the valve seat portion 7 → the peripheral groove 5 → the fuel introduction passage 6 (side hole 6b → the central hole 6a) → the suck portion 4, but the effective area of the injection hole 3 is determined by the small diameter portion 8. It is restricted.

Here, the fuel passage area of the valve seat portion 7 increases in proportion to the needle lift amount as in the nozzle characteristic shown in FIG. 2. The inclination of the proportional coefficient is the valve seat angle and the valve seat. Determined by diameter. By appropriately selecting these values, the relationship between the needle lift amount and the fuel flow passage area of the valve seat portion 7 can be changed as shown in FIG.
Can always be larger than the effective area of.

Therefore, compared with the conventional throttle hole nozzle and the nozzle provided with the auxiliary injection hole, the fuel injection pressure does not decrease and the initial injection rate can be suppressed. 3 and 4 show an embodiment of the invention described in claim 2. FIG.
4 is an example in which the cross-sectional shape of the injection hole 3 is variously changed.
The cross-sectional shape of the injection hole 3 is an ellipse as shown in FIG. 3 (a) (major axis is in the nozzle axis direction), a perfect circle as shown in FIG. 3 (b), and an ellipse as shown in FIG. 3 (c) (major axis is perpendicular to the nozzle axis). Direction), the relationship between the needle lift amount and the effective injection hole area is shown.

Therefore, the relationship between the needle lift amount and the effective area of the injection hole 3 can be changed by changing the cross-sectional shape of the injection hole 3 in accordance with the required nozzle characteristics, which is more suitable for the engine characteristics. The fuel injection nozzle can obtain a high initial injection rate. 5 and 6 show an embodiment of the invention described in claim 3.

FIG. 5 shows an example in which the injection holes of the multi-injection fuel injection nozzle are offset from each other in the nozzle axis direction, and FIG. 6 shows the height of all injection holes as shown in FIG. 5 (a). 5 shows the relationship between the needle lift amount and the effective injection hole area when the heights of the injection holes are shifted as shown in FIG. 5B. Therefore, by shifting the heights of the nozzle holes from each other according to the required nozzle characteristics, the nozzle holes are opened sequentially from the lower nozzle holes according to the needle lift amount, so that all nozzle hole heights are the same. In comparison, the relationship between the needle lift amount and the effective injection hole area becomes gentle and stepwise, and it is possible to obtain a fuel injection nozzle that can obtain an initial injection rate that better matches the engine characteristics.

[0016]

As described above, according to the first aspect of the invention, the effective injection hole area of the nozzle is changed according to the lift amount of the needle valve, so that the initial injection rate of fuel is suppressed. Since the particle size of the fuel spray is reduced and the generation of the air-fuel mixture is promoted, NOx emission and combustion noise can be reduced while preventing deterioration of black smoke emission.

According to the invention described in claim 2, in addition to the effect of the invention described in claim 1, the required nozzle characteristics are variously changed, so that the fuel injection rate that more closely matches the engine characteristics can be obtained. It can be a nozzle. According to the invention of claim 3, in addition to the effect of the invention of claim 1, the required nozzle characteristics become gentle and stepwise, so that an initial fuel injection rate that better matches the engine characteristics can be obtained. It can be a fuel injection nozzle.

Further, according to the inventions of claims 1 to 3, since the above-mentioned respective effects are obtained by a slight improvement of the injection nozzle, the cost is not significantly increased.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a fuel injection nozzle showing an embodiment of the present invention, (a) shows the configuration of the fuel injection nozzle, (b) shows a cross section AA of the above, and (c) shows a cross section BB of the same. Indicates

FIG. 2 is a diagram showing the relationship between the needle lift amount and the effective injection hole area and flow path area in the same as above.

FIG. 3 is a diagram showing an example in which the cross-sectional shape of the injection hole is variously changed as another application example, in which (a) shows the case where the injection hole has an elliptical cross section (major axis is the nozzle axis direction), and (b) shows the injection hole. The case where the cross section is a perfect circle is shown, and (c) shows the case where the injection hole cross section is an ellipse (the major axis is in the direction perpendicular to the nozzle axis).

FIG. 4 is a diagram showing a relationship between a needle lift amount and an effective injection hole area in the same as above.

FIG. 5 is a diagram showing an example in which the heights of the injection holes are shifted as another application example, in which (a) shows the case where all the injection hole heights are the same, and (b) shows the injection hole heights that are shifted. Indicates the case

FIG. 6 is a diagram showing a relationship between a needle lift amount and an effective injection hole area in the same as above.

FIG. 7 is a block diagram of a conventional throttle hole nozzle.

FIG. 8 is a diagram showing a relationship between a needle lift amount and a flow passage area in the same as above.

FIG. 9 is a configuration diagram of a fuel injection nozzle provided with a sub injection hole, which is a conventional technique.

[Explanation of Codes] 1 Nozzle body 2 Needle valve 3 Injection hole 4 Suck part 5 Circumferential groove 6 Fuel introduction passage 8 Small diameter part

Claims (3)

[Claims] 1. In a multi-injection fuel injection nozzle, a needle valve tip internally provided so as to be liftable in a nozzle body is formed in a cylindrical small-diameter portion fitted into an inner diameter of a sack portion of the nozzle body tip. , The small diameter portion directly closes the injection hole of the peripheral wall of the sack portion when the lift amount of the needle valve is 0,
The structure is such that the opening area of the injection hole is gradually increased as it is lifted, and in order to communicate the inside of the tip of the sack portion with the fuel passage in the nozzle body, a circumferential groove around the base of the small diameter portion, and the circumferential groove and the sack. A fuel injection nozzle for a diesel engine, characterized in that a fuel introduction passage communicating with the inside of the tip of the portion is provided. 2. The fuel injection nozzle for a diesel engine according to claim 1, wherein each of the injection holes provided on the peripheral wall of the sack portion has a cross-sectional shape changed according to required nozzle characteristics. 3. The position of each injection hole provided on the peripheral wall of the sack portion is set at a position displaced in the nozzle axial direction from each other according to the required nozzle characteristics. Fuel injection nozzle for diesel engine.