FUEL INJECTION VALVE FOR DIESEL ENGINE

Abstract

 The present invention relates to a fuel injection nozzle of a direct-injection diesel engine. Said valve comprises a first serration formed on the opening edge of a nozzle body and a second serration formed to the top end portion of a needle valve, which incline against the axial direction, and a third serration and a fourth serration formed to the outer wall of the end portion of said needle valve and to the inner wall of a rotary valve inserted to said end portion, which incline to the opposite direction to the first and second serrations with respect to the axial direction. When the needle valve is lifted, the needle valve axially rotates, and the rotary valve rotates relative to said needle valve in the same rotating direction. As the rotation amount increases, the overlapped area of first nozzle holes formed to the nozzle body and second nozzle holes formed to the rotary valve increases. During idle state or in low-load region, the overlapped area is small, and during high load, the area increases corresponding to the fuel injection pressure. Thus, the spray penetration of the fuel is maintained constantly high, and the fuel effectively collides with squished air, realizing good mixture. Thereby, it is possible to effectively minimize ignition delay, while improving combustion performance, quietness, and exhaust emissions performance.

Description

Field of the Invention

[0001] The present invention relates to a fuel injection nozzle of a diesel engine.

Description of the Related Art

[0002] A fuel injection nozzle of a diesel engine, especially a direct-injection type engine, is generally constructed so that a needle valve is inserted, so as to be lifted freely in the axial direction, to a nozzle body having a plurality of nozzle holes. When fuel is introduced from a fuel inlet passage formed within the nozzle body, the needle valve is lifted by the fuel pressure so that the fuel passes through a gap formed between the surrounding wall of the needle valve and the inner wall of the nozzle body, to be injected through the plurality of nozzle holes into a combustion chamber (piston cavity).

[0003] According to the conventional fuel injection nozzle of a diesel engine as mentioned in the above, the opening area of each nozzle hole is fixed. Therefore, during a high-load state where the fuel pressure is high, sufficiently high spray penetration can be attained. However, during a low-load state where the fuel pressure is low, since the spray penetration is reduced, the fuel will not be sufficiently atomized. Therefore, the fuel will be combusted before being sufficiently mixed with air. This causes longer ignition delay, increases combustion noise, and deteriorates exhaust emissions performance (especially smoke).

[0004] According to another method, there has been provided a rotary valve in which a fuel passage is formed, so that by the rotation of rotary valve, the throttling between the nozzle holes of the nozzle body changes. The rotary valve is made to rotate by means of a pulse motor and the like, so that, during the low-load state, the nozzle hole area is throttled, and spray penetration of the fuel is increased.

[0005] However, provision of such a pulse motor and the like will result in that the size of the fuel injector assembly is increased, and the manufacturing cost is also increased. Further, the structure of the injector assembly becomes complex, decreasing the reliability of the injector.

[0006] The present invention aims at solving the above-mentioned problems of the conventional fuel injection nozzle. The object of the invention is to realize good combustion performance and good exhaust emissions performance by mixing rapidly and sufficiently the atomized fuel with the air within the combustion chamber, in the whole range of load from the low-load region to the high-load region, especially, to contribute greatly to improve the performance during the idle state or the low-load region of the engine.

[0007] Moreover, the further object of the present invention is to realize performance mentioned above by a fuel injection nozzle having a simple structure without increasing the size of the injector body, only by forming an automatic and mechanical rotary structure driven by the fuel pressure without mounting a separate driving device such as a pulse motor.

[0008] The still further object of the present invention is to promote reduction of height of the piston cavity, to thereby reduce the engine height as a whole by effectively utilizing the spray penetration and the squish to mix the fuel with the air.

Summary of the Invention

[0009] In order to realize the above objects, the present invention provides a fuel injection nozzle of a diesel engine, in which a needle valve inserted within a nozzle body is lifted in the axial direction by fuel pressure when fuel is introduced through a fuel inlet passage formed in the nozzle body and a nozzle holder, and the fuel passes through a gap formed between the needle valve and the nozzle body, so as to be injected into a combustion chamber through nozzle holes formed to the nozzle body, the fuel injection nozzle being characterized in that:

a first serration is formed on the opening edge at the end surface of the nozzle body engaged with the nozzle holder, the serration inclining against the axial direction;

a second serration is formed to the outer peripheral surface at the top end portion of the needle valve, which is engaged with the first serration, and allows the needle valve to axially rotate corresponding to the movement of the needle valve in the axial direction;

a tip portion on the nozzle hole side of the needle valve is formed so as to have a gap between the inner surface of a tip portion on the nozzle hole side of the nozzle body, to dispose in the gap a bag-shaped rotary valve for fitting to the tip potion of the needle valve;

a third serration and a fourth serration formed to the outer peripheral surface at the tip portion of the needle valve and to the inner peripheral surface of the rotary valve, respectively, which are engaged with each other with a gap therebetween, and incline in the opposite direction to the first and second serrations with respect to the axial direction; and

a plurality of second nozzle holes are formed in the rotary valve, of which area overlapping with a plurality of first nozzle holes formed to the nozzle body increases, depending on the rotation amount of the rotary valve which increases as the lifting amount of the needle valve in the axial direction increases.

[0010] According to this construction, the needle valve inserted within the nozzle body is lifted in the axial direction by the fuel pressure, when fuel is introduced through the fuel inlet passage formed within the nozzle holder and the nozzle body. Due to the engagement of the first serration and the second serration, the needle valve axially rotates in one direction. Simultaneously, due to the engagement of the third serration and the fourth serration, the rotary valve the lifting amount of which is limited by the fuel pressure axially rotates relative to the needle valve in the same rotating direction as the needle valve.

[0011] In other words, the rotary valve axially rotates by the total amount obtained by adding the rotation amount caused by the engagement of the first serration and second serration, and the rotation amount caused by the engagement of the third serration and fourth serration. Further, the rotation amount of the rotary valve is small in the low-load region where the fuel injection quantity is low, since fuel pressure is low and the lifting amount of the needle valve is also small. On the other hand, the rotation amount of the rotary valve increases, as the fuel pressure increases and the lifting amount of the needle valve increases with the increase of the load.

[0012] Then, in response to the increase of the rotation amount of the rotary valve, the overlapped area of the first nozzle holes and the second nozzle holes increases.

[0013] After passing through the gap between the needle valve and the nozzle body, the fuel travels through the gap between the third serration and the fourth serration, and reaches the interior of the rotary valve. Then, the fuel is injected into the combustion chamber through the overlapped area of the second nozzle holes formed to the rotary valve and the first nozzle holes formed to the nozzle body.

[0014] Here, in the low-load region where the fuel pressure is low, by making the overlapped area of the nozzle holes small, the spray penetration of the fuel increases so that the atomization of fuel is promoted, and the amount of air with which the atomized fuel contacts is increased. Therefore, the fuel may rapidly and sufficiently mix with air. Thereby, it is possible to minimize the ignition delay, to obtain good the combustion performance and to improve the quietness and the exhaust emission (especially smoke) performance.

[0015] Further, as the load increases and the fuel injection quantity and pressure increases, the overlapped area of the nozzle holes increases continuously. Therefore, the fuel injection zone is enlarged while the spray penetration of the fuel is maintained, and the fuel contacts and mixes with air of the amount corresponding to the fuel injection quantity. Accordingly, the best fuel atomization is obtained throughout the whole region with fuel and air mixed well, which brings good combustion performance and improved exhaust emissions performance.

[0016] Further, the above-mentioned improvement of the performances can be realized by a fuel injector having a simple structure without increasing the size of the valve body, only by forming an automatic and mechanical rotary structure driven by the fuel pressure without mounting a separate driving device such as pulse motor.

[0017] Moreover, even when the maximum lifting amount of the needle valve is limited to be relatively small, the rotary valve may be made to rotate by a large rotation amount obtained by adding the rotation amount caused by the engagement of the first and second serrations, and the rotation amount caused by the engagement of the third and fourth serrations. Accordingly, the dynamic range of the overlapped area of the nozzle holes may be made to be sufficiently large, to obtain the optimum overlapped area depending on the load.

[0018] Further, each of the second nozzle holes may open in a shape of elongated ellipse in the rotating direction of the rotary valve, and each of the first nozzle holes may open in a round shape having a larger diameter than the narrower width of the second nozzle holes.

[0019] According to this construction, the sprayed fuel through the first nozzle holes diffuses in flat in the circumferential direction, to collide efficiently with the squish generated within the combustion chamber during the compression stroke, so that the fuel may be effectively mixed with the air. This enables to improve the combustion performance, the quietness and the exhaust emissions performance.

[0020] Moreover, since the amount of fuel atomized to diffuse toward the circumferential direction increases corresponding to the increase of fuel injection quantity, the fuel may be made to contact well with squished air of the amount corresponding to the fuel injection quantity, so that a good mixture condition can be obtained throughout the whole operating region.

[0021] Even further, the present invention is the system for mainly utilizing the strong spray penetration and the squish to enhance the mixing of fuel and air. Therefore, the height of the cavity may be reduced, and also, the piston height and the engine height may also be reduced.

[0022] Further, the first serration may be formed to the inner peripheral surface of a guide ring that is prohibited the axial rotation to be fit to a groove formed on the opening edge of the nozzle body.

[0023] Although the first serration can be worked directly to the opening edge of the nozzle body, the working accuracy is hard to be improved, and the manufacturing cost is increased. Contrary to this, according to the above construction, the guide ring with the first serration formed to the inner peripheral surface thereof, which may be manufactured at low cost, is simply fit to the groove formed by a simple working on the opening edge of the nozzle body, so that the fuel injection nozzle according to the invention having such simple structure may be formed at low cost, and the required level of working accuracy may also be achieved easily.

[0024] Moreover, the construction may be such that the first serration is formed to the inner peripheral surface of a guide ring that is fit to a groove formed on the opening edge of the nozzle body and rotates freely in a predetermined angle in the axial direction;

a guide ring spring is disposed for biasing the guide ring toward a direction opposite to the rotating direction of the needle valve when the needle valve is lifted in the axial direction; and

one or more slits are formed to the peripheral wall of the needle valve, which increase in depth toward the rotating direction of the needle valve when the needle valve is lifted in the axial direction, and operate rotary force to the needle valve in the rotating direction by the received fuel pressure.

[0025] According to this construction, the rotary force acting on the needle valve in the rotating direction when the needle valve is lifted in the axial direction increases in response to the increase of fuel pressure received by the slits formed to the peripheral wall of the needle valve, so that the guide ring rotates in the same direction as the rotating direction of the needle valve against the bias force of the guide ring spring, to allow the needle valve to rotate integrally in the same direction with the guide ring.

[0026] Even if there is not much space for the needle valve to be lifted, the rotation amount may be ensured greatly in proportion to the fuel pressure. Simultaneously, the guide ring, the needle valve and the rotary valve can securely rotate and be maintained at closed-valve position by the operation of the guide ring spring, when the fuel injection nozzle is closed where the fuel pressure is low.

[0027] Further, corn-tapered surfaces may be each formed to the needle valve in the area closer to the base end portion than the third serration portion, and to the inner peripheral surface of the nozzle body in the area closer to the base end portion than the rotary valve, wherein the corn-tapered surfaces contact each other when the needle valve is not lifted.

[0028] According to construction, when the fuel injection nozzle is closed, the corn-tapered surfaces formed to the needle valve and the nozzle body contact with each other, thereby preventing the fuel from being communicated to the nozzle holes, to completely shut off the valve.

Brief Description of the Drawings

[0029] 

FIG. 1 is a vertical cross-sectional view of a main part showing the closed state of a fuel injection nozzle of a diesel engine according to one embodiment of the present invention;

FIG. 2 shows the state where the fuel injection nozzle of FIG. 1 is opened, wherein (A) is a vertical cross-sectional view showing the main part of the valve, and (B) is a partial top view;

FIG. 3 shows an AA cross-sectional view and a B arrow view of FIG. 1 or FIG. 2, and the sprayed state of fuel in a combustion chamber according to each operating position of the fuel injection nozzle, wherein (A) shows the closed valve state, (B) shows the low-load (idle) state where the nozzle hole is slightly opened, (C) shows the mid-load state where the nozzle hole is half opened, and (D) shows the full-load state where the nozzle hole is fully opened;

FIG. 4 shows the fuel injection nozzle of the diesel engine according to a second embodiment of the present invention, wherein (A) is a vertical cross-sectional view showing the main part, (B) is a partial top view, and (C) is a partial transverse cross-sectional view; and

FIG. 5 is a partial top view of the fuel injection nozzle of the diesel engine according to a modification of the second embodiment.

Detailed Description of the Preferred Embodiment

[0030] Preferred embodiments of the present invention will now be explained with reference to the drawings.

[0031] In FIG. 1 (valve closed) and FIG. 2 (valve opened) showing a structure of the tip portion of a fuel injection nozzle of diesel engine according to the present invention, a nozzle body 1 is turned in the axial direction to be engaged with a nozzle holder (not shown in the figures), and the nozzle body is firmly connected to the nozzle holder by means of a bolt and a nut disposed to the exterior.

[0032] A fuel inlet passage 11 communicated to a fuel passage formed to the interior of the nozzle holder is formed to the interior of the nozzle body 1, the downstream end of which reaches a fuel pool 12 formed to the inner peripheral surface in the middle area of the nozzle body 1. Further, a plurality of nozzle holes (first nozzle holes) 13 are formed on the tip portion of the nozzle body 1 with intervals in the peripheral direction.

[0033] A groove 14 is formed on the opening edge on the top end portion side of the nozzle body 1 that is formed in a manner similar to the prior art. Further, a guide ring 15 which includes a first serration 15a formed on the inner peripheral surface of the ring 15 and inclining against the axial direction, is prohibited the axial rotation to be fit to the groove 14 by turning, as shown in the figures.

[0034] On the other hand, a needle valve 2 is inserted and fixed to the interior of the nozzle body 1. A second serration 21 is formed to the outer peripheral surface at the top end portion of the needle valve 2. The second serration 21 is engaged with the first serration 15a of the guide ring 15, and allows the needle valve 2 to axially rotate corresponding to the movement of the needle valve 2 in the axial direction.

[0035] The tip portion of the needle valve 2 on the nozzle hole side is formed to have a gap between the inner surface on the nozzle hole side of the tip portion of the nozzle body 1. A bag-shaped rotary valve 3, which fits to the tip portion of the needle valve 2, is disposed in the gap.

[0036] Further, a third serration 22 and a fourth serration 31 are formed to the outer peripheral surface at the tip portion of the needle valve 2 and to the inner peripheral surface of the rotary valve 3, respectively, which are engaged with each other with a gap therebetween and incline in the opposite direction to the first serration 15a and the second serration 21 with respect to the axial direction. The gap between the third serration 22 and the fourth serration 31 is formed only in the area between the peak of the protrusion and the trough of the groove along the longitudinal direction of the serration, so that fuel may pass through the gap. Since hardly any gap is formed in the circumferential direction of the valve, the valve is prevented from rattling during rotation.

[0037] Further, a plurality of nozzle holes 32 (second nozzle holes) are formed to the rotary valve 3, in the area closer to the nozzle holes 13 than the fourth serration 31, of which area overlapping the plurality of nozzle holes 13 (first nozzle holes) formed to the nozzle body 1 increases depending on the rotation amount of the rotary valve 3 which increases, as the lifting amount of the needle valve 2 in the axial direction increases.

[0038] Each of the nozzle holes 32 (second nozzle holes) formed to the rotary valve 3 opens in the shape of an elongated ellipse (with both ends formed in a round shape), in the rotating direction of the rotary valve 3. Each of the nozzle holes 13 (first nozzle holes) of the nozzle body 1 opens in a round shape, having a larger diameter than the narrow side width of the nozzle holes 32 (second nozzle holes).

[0039] Further, cone-tapered surfaces 23, 16 are each formed to the needle valve 2 in the area closer to the base end portion than the third serration 22, and to the inner peripheral surface of the nozzle body 1 in the area closer to the base end portion than the area disposing the rotary valve 3 therein, respectively. The two surfaces 23, 16 contact each other when the needle valve is not lifted.

[0040] The operation of the present fuel injection nozzle formed as above will now be explained.

[0041] When the fuel injection nozzle is closed, in other words, when a fuel supply pressure applied to the fuel inlet passage 11 is low so that no fuel injection is performed, a return spring (not shown in the figures) biases the needle valve 2 toward the nozzle hole side. The corn-tapered surface 23 of the needle valve 2 and the corn-tapered surface 16 of the nozzle body 1 will be pressurized to contact each other, and the communication between the fuel inlet passage 11 and the nozzle hole side is completely shut off.

[0042] Further, when the nozzle is closed, as shown in FIG. 3 (A), the rotary valve 3 is set in a rotating position so that the nozzle holes 13 (first nozzle holes) and the nozzle holes 32 (second nozzle holes) are not overlapped at all. This structure of the valve enables to maintain a reliably closed state, preventing problems such as subsequent dripping and the like.

[0043] When fuel is supplied to the fuel inlet passage 11 under a pressure equal to or over a predetermined value, the fuel pressure is received by a stepped pressure receiving surface at the fuel pool 12 of the needle valve 2. Thereby, the needle valve 2 is lifted in the axial direction, against the bias force of the return spring (not shown in the figures).

[0044] When the needle valve 2 is lifted, the needle valve 2 axially rotates in one direction, since the first serration 15a and the second serration 21 are engaged with each other. Further, the rotary valve 3, the lifting of which is limited by the fuel pressure (as explained in detail later) axially rotates relative to the needle valve 2 in the same direction as the rotating direction of the needle valve 2, due to the engagement of the third serration 22 and the forth serration 31. In other words, the rotary valve axially rotates by the total amount of rotation obtained by adding the rotation amount caused by the engagement of the first serration and second serration, and that caused by the engagement of the third serration and fourth serration.

[0045] By the axial rotation of the rotary valve 3 explained above, the nozzle holes 32 and the nozzle holes 13 overlap. The overlapped area increases as the lifting amount of the needle valve 2 increases, due to the increase of fuel pressure. In other words, during the idle state or in the low-load region where the fuel pressure is low, the overlapped area is controlled to be small. As the fuel pressure increases with the increase of load, the overlapped area is controlled to increase as well.

[0046] Further, when the needle valve 2 is lifted, the cone-tapered surfaces 23, 16 separate from each other, and the fuel is introduced through the gap formed between the needle valve 2 and the nozzle body 1 to the nozzle hole side. The fuel further passes through the gap formed between the third serration 22 and the fourth serration 31, and reaches the inner space of the rotary valve 3, where it is sprayed through the overlapped portion of the nozzle holes 32 and the nozzle holes 13 into a combustion chamber.

[0047] During the idle state or in the low-load region where the fuel pressure is low, the overlapped area of the nozzles is controlled to be small, as shown in FIG. 3 (B), to increase spray penetration of the fuel, so that atomization of the fuel is promoted. Since the amount of air with which the atomized fuel contacts increases as well, the fuel will mix with air rapidly and sufficiently before being combusted. Particularly, according to the present embodiment, each of the inner nozzle holes 32 opens in a shape of elongated ellipse in the rotating direction of the rotary valve 3, and each of the outer nozzle holes 13 opens in a round shape having a larger diameter than the narrower width of the nozzle holes 32. This enables the sprayed fuel to diffuse in flat in the circumferential direction. Therefore, the fuel efficiently collides with the squish generated within the combustion chamber during the compression stroke, so that the fuel may be effectively mixed with air.

[0048] According to this construction, it is possible to minimize ignition delay, to obtain good combustion performance, and to improve quietness and exhaust emissions performance (especially, smoke).

[0049] Further, as the load increases and the fuel injection quantity increases, the overlapped area of the nozzle holes increases continuously. Therefore, the injection zone is enlarged while the spray penetration of the fuel is maintained, and the fuel contacts and mixes with air of the amount corresponding to the fuel injection quantity. Accordingly, the best fuel atomization is obtained throughout the whole area with fuel and air mixed well, which brings the good combustion performance and good exhaust emissions performance. FIG. 3 (C) shows the state where the overlap between the nozzle holes is approximately 50 %, and FIG. 3 (D) shows the full-load state where the nozzle holes are 100 % overlapped.

[0050] According to the present embodiment, only a design modification is made by adding to the conventional type fuel injection nozzle structure, four types of serrations, a groove 14, and disposing a guide ring 15, a guide ring spring 33, and a rotary valve 3, to provide the fuel injector without increasing the size of the injector at low cost with high reliability, since there is no need to add a separate driving device such as a pulse motor and the like to the valve structure.

[0051] Even further, the present embodiment is the system for mainly utilizing squish to enhance the mixing of fuel and air and to extend the fuel spray travel. Therefore, by applying an intake port which ensures intake air quantity to the utmost without considering the induction swirl, the cavity may be designed to be shallower, and also, the piston height or the engine height can be reduced. Further, by maintaining even more air within the combustion chamber, the fuel injection quantity can be increased and the specific power can be increased.

[0052] Next, a second embodiment of the present invention will be explained with reference to FIG. 4. In FIG. 4, the same reference numbers are denoted to the same components as those of FIG. 1.

[0053] According to the present embodiment, a groove 41 for engaging the guide ring 15 is formed on the opening edge on the top end portion side of the nozzle body 1 to have an area, with which a protrusion 15b of the guide ring 15 is engaged, larger in the circumferential direction than the width of the protrusion 15b of the guide ring 15 in the circumferential direction, so that the guide ring 15 axially rotates in a predetermined angle. The groove 41 further has a large depth in the axial direction so as to accommodate a guide ring spring 16, to be explained later.

[0054] A guide ring spring 42 comprising a torsion coil spring is mounted within the groove 41 below the guide ring 15. The spring 42 has one end engaged with the guide ring 15 and the other end positioned and fit within the groove 41, so as to bias the guide ring 15 to a direction (clockwise in the upper view) opposite to the rotating direction of the needle valve 2 when the valve 2 is lifted in the axial direction.

[0055] Moreover, a plurality of slits 43 are formed with even intervals in the circumferential direction of the side wall of the needle valve 2. The cross-sectional shape of each of the slits 43 is formed in a windmill-shape, with each slit formed to increase in depth toward the rotating direction of the needle valve 2 when the valve 2 is lifted in the axial direction. The windmill-shape slits 43 operate rotary force to the needle valve 2 in the rotating direction (counterclockwise in the upper view), by the pressure of the fuel received through the fuel pool 12. The other structures of the valve are the same as those of embodiment 1.

[0056] According to this construction, as the fuel pressure received by the slits 43 of the needle valve 2 via the fuel pool 12 increases, the rotary force acting on the needle valve 2 in the rotating direction when the needle valve 2 is lifted in the axial direction increases, so that the guide ring 15 rotates in the same direction as the rotating direction against the bias force of the guide ring spring 42, to allow the needle valve 2 to rotate integrally in the same direction with the guide ring 15.

[0057] Even if there is not much space for the needle valve 2 to be lifted, the rotation amount may be ensured greatly in proportion to the fuel pressure. Simultaneously, the guide ring 15, the needle valve 2 and the rotary valve 3 can securely rotates and be maintained at the closed valve position by the operation of the guide ring spring 42, when the fuel injection nozzle is closed where the fuel pressure is low.

[0058] FIG. 5 shows a modification of the second embodiment. A groove 51 for engaging the guide ring 15 is formed on the opening edge of the nozzle body 1, to have an area, with which the protrusion 15b of the guide ring 15 is engaged, larger in the circumferential direction than the width of the protrusion 15b of the guide ring 15 in the circumferential direction, so that the guide ring 15 axially rotates in a predetermined angle. A guide ring spring 52, which biases the guide ring 15 to a direction opposite to the rotating direction of the needle valve 2 when the valve 2 is lifted, is mounted to the area to which the protrusion 15b of the guide ring 15 is fit. The guide ring spring 52 may be formed of a plate spring and the like.

Industrial Applicability

[0059] As explained, the present invention may be applied to a fuel injection nozzle of a direct-injection-type diesel engine of a vehicle and the like. The present invention may be applied to a fuel injector equipped to a pipeline fuel injection device or a common-rail fuel injection device or a unit type fuel injector.

Claims

1. A fuel injection nozzle of a diesel engine, in which a needle valve inserted within a nozzle body is lifted in the axial direction by fuel pressure when fuel is introduced through a fuel inlet passage formed in the nozzle body and a nozzle holder, and the fuel passes through a gap formed between said needle valve and said nozzle body, so as to be injected into a combustion chamber through nozzle holes formed to the nozzle body, the fuel injection nozzle being characterized in that:

a first serration is formed on the opening edge at the end surface of the nozzle body engaged with the nozzle holder, the serration inclining against the axial direction;

a second serration is formed to the outer peripheral surface at the top end portion of said needle valve, which is engaged with said first serration, and allows the needle valve to axially rotate corresponding to the movement of said needle valve in the axial direction;

a tip portion on the nozzle hole side of said needle valve is formed so as to have a gap between the inner surface of a tip portion on the nozzle hole side of the nozzle body, to dispose in the gap a bag-shaped rotary valve for fitting to said tip potion of the needle valve;

a third serration and a fourth serration formed to the outer peripheral surface at the tip portion of said needle valve and to the inner peripheral surface of said rotary valve, respectively, which are engaged with each other with a gap therebetween, and incline in the opposite direction to said first and second serrations with respect to the axial direction; and

a plurality of second nozzle holes are formed, of which area overlapping with a plurality of first nozzle holes formed to the nozzle body increases, depending on the rotation amount of the rotary valve which increases as the lifting amount of said needle valve in the axial direction increases.

2. A fuel injection nozzle of a diesel engine according to claim 1, wherein each of said second nozzle holes may open in a shape of elongated ellipse in the rotating direction of the rotary valve, and each of said first nozzle holes may open in a round shape having a larger diameter than the narrower width of the second nozzle holes.

3. A fuel injection nozzle of a diesel engine according to claim 1 or claim 2, wherein said first serration may be formed to the inner peripheral surface of a guide ring that is prohibited the axial rotation to be fit to a groove formed on the opening edge of the nozzle body.

4. A fuel injection nozzle of a diesel engine according to claim 1 or claim 2, wherein said first serration is formed to the inner peripheral surface of a guide ring that is fit to a groove formed on the opening edge of the nozzle body and rotates freely in a predetermined angle in the axial direction;

a guide ring spring is disposed for biasing said guide ring toward a direction opposite to the rotating direction of the needle valve when the needle valve is lifted in the axial direction; and

one or more slits are formed to the peripheral wall of the needle valve, which increase in depth toward the rotating direction of said needle valve when the needle valve is lifted in the axial direction, and operate rotary force to the needle valve in said rotating direction by the received fuel pressure.

5. A fuel injection nozzle of a diesel engine according to any one of claims 1 to 4, wherein corn-tapered surfaces are each formed to the needle valve in the area closer to the base end portion than the third serration portion, and to the inner peripheral surface of the nozzle body in the area closer to the base end portion than the rotary valve mounting portion, the corn-tapered surfaces contacting with each other when the needle valve is not lifted.

Drawing