JP2000161185A - Fuel injection nozzle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce soot, NOX and the like in exhaust gas and to reduce fuel consumption and manufacturing costs by enhancing fuel atomization characteristic during the low lift of a valve needle. SOLUTION: A needle pin part 56 has first and second reduced diameter parts 561, 562 and a plurality of channeled parts 563. Under a low-speed, low- load condition wherein lift is small, fuel is injected from some of nozzle holes 17 communicated with the channeled parts 563, whereby the throttling of openings in a valve seat part 13 and an abutting part 47 is reduced and the fuel injected can be maintained at high pressure. Under a high-speed, high-load condition, the first reduced diameter part 561 is communicated with all the nozzle holes 17 and the fuel is injected from all the nozzle holes 17. Therefore, fuel atomization characteristic in all lift areas is enhanced by means of a simple structure and NOX, soot and the like in exhaust gas can be decreased whereby fuel consumption can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine (hereinafter referred to as "internal combustion engine").
The present invention relates to a fuel injection nozzle for an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, a fuel injection nozzle for injecting high-pressure fuel pressurized and fed by a high-pressure pump into an internal combustion engine has been known.
It is known as disclosed in EP 0 735 658. European Patent Office 0735658
In a fuel injection nozzle as disclosed in
A tapered pressure receiving surface is formed on the tip side of the valve needle slidably housed in the nozzle body, and the valve needle is opened and closed by applying fuel pressure to the pressure receiving surface, and is disposed at the tip of the nozzle body. The fuel was injected from the fuel injection holes. However, in the fuel injection nozzle having the above configuration, particularly when the valve needle is at a low lift, the area of the opening between the contact portion of the valve needle through which fuel passes and the valve seat of the nozzle body is increased by the fuel injection hole (injection hole). Since the area of the opening is smaller than the total opening area of the hole, the pressure is reduced before the fuel reaches the injection hole, and the opening area of the injection hole is increased, so that the injection pressure of the fuel is also reduced. Therefore, when the low-lift of the valve needle, the fuel for the injection pressure not smaller sufficiently atomized, soot contained in exhaust gases, such as NO _x increases,
There is a problem that fuel consumption increases.

In order to solve the above-mentioned problem, the fuel injection nozzle disclosed in Japanese Patent Application Laid-Open No. 9-280134 employs a variable injection hole type fuel injection nozzle so that the fuel injection at the time of low lift of the valve needle is improved. Has improved atomization characteristics. In such a variable injection hole type fuel injection nozzle, a hole is provided at the tip of the fuel injection nozzle,
A plurality of injection holes are formed on the peripheral wall of the hole at intervals, and a rotary valve is rotatably mounted in the hole so that the injection hole area is variable depending on the rotation position of the rotary valve. With such a configuration,
When the valve needle is at a low lift, the total opening area of the injection hole can be reduced, and the injected fuel can be maintained at a high pressure, so that the atomization characteristics of the fuel at the time of the valve needle at a low lift are improved. Soot in exhaust gas, N
_{Ox and the} like could be reduced, and the fuel consumption could be reduced.

[0004]

However, a variable injection hole type fuel injection nozzle as disclosed in Japanese Patent Application Laid-Open No. 9-280134 discloses a small rotary valve inside a hole and a motor for driving the rotary valve. Has to be mounted with high accuracy, and the structure is complicated. In addition, there is a problem that a dedicated power supply and a control device are required to drive the rotary valve, so that the manufacturing cost is increased.

[0005] It is an object of the present invention is to improve the atomization characteristics of the fuel at the time of low lift of the valve needle with a simple structure, soot in the exhaust gas, it is possible to reduce such NO _x, fuel consumption The amount can be reduced,
Another object of the present invention is to provide a fuel injection nozzle capable of reducing manufacturing costs.

Another object of the present invention is to provide a fuel injection nozzle capable of improving fuel injection characteristics in the entire lift range of a valve needle.

[0007]

According to the fuel injection nozzle of the first aspect of the present invention, the projection at the tip of the valve needle has a first reduced diameter portion and a plurality of grooves. When the lift amount of the valve needle is smaller than the predetermined lift amount, that is, when the lift amount is low, the groove communicates with a part of the plurality of injection holes, and fuel is injected only from some of the injection holes through the groove.
Therefore, the total opening area of the injection hole when the valve needle lift is small and at low speed and low load is smaller than the opening area at the valve seat portion and the valve needle contact portion of the nozzle body. As a result, the fuel throttle phenomenon at the valve seat portion and the contact portion is reduced, and the pressure of the fuel at the upstream of the injection hole can be maintained high. soot, it is possible to reduce such NO _x, it is possible to reduce the consumption of fuel. Further, for example, since a driving member such as a rotary valve is not required in the vicinity of the injection hole unlike the conventional fuel injection valve, the structure of the fuel injection nozzle is simple, and the processing and manufacturing are easy. It is possible to reduce.

According to the fuel injection nozzle of the present invention, when the lift amount of the valve needle is larger than the predetermined lift amount, that is, when the lift amount is high, the first reduced diameter portion and all of the injection holes communicate. Then, the fuel is injected from all the injection holes. Therefore, when the valve needle lift is large and the high speed and high load, the total opening area of the injection hole is sufficiently secured, and the fuel required for combustion can be sufficiently injected. Until time, the injection characteristics can be improved in the entire lift range.

According to the fuel injection nozzle of the third aspect of the present invention, since the projecting portion has the second reduced diameter portion near the contact portion, the fuel flow area downstream of the contact portion increases, The flow resistance of the fuel passing between the valve seat portion and the contact portion can be reduced. Therefore, it is possible to prevent the pressure of the injected fuel from decreasing.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention; (First Embodiment) FIGS. 1 to 5 show a first embodiment in which the present invention is applied to a fuel injection valve for a diesel engine. The fuel injection valve 1 is a fuel injection valve that injects fuel stepwise into a combustion chamber of a diesel engine (not shown), and includes a nozzle holder 20, a retaining nut 30, and a distance piece 4.
0, an outer shell forming member including the fuel injection nozzle 10 is provided. In the fuel injection valve 1, the nozzle holder 20, the distance piece 40, and the fuel injection nozzle 10 are fixed by a retaining nut 30.

The nozzle holder 20 has a fuel inlet 21
And a first spring accommodating chamber 22 and a second spring accommodating chamber 23 penetrating in the axial direction are formed. The fuel inlet 21 is connected to a fuel pipe (not shown) from a high-pressure pump (not shown), and supplies high-pressure fuel into the fuel injection nozzle 10 from the high-pressure pump. A fuel passage 24 is formed inside the fuel inlet 21.

A first spring 221, a spacer 222, and a flange 61 of a pressure pin 60 which will be described later are accommodated in the first spring accommodating chamber 22. First
The spring 221 has a pressure pin 60 at one end.
Of the spacer 22 and the other end of the spacer
It is in contact with 2. The first spring 221 urges the valve needle 50 through the pressure pin 60 in a downward direction shown in FIG.

A second spring 231, a spacer 232, a spring cap 233, and a spring seat 234 are accommodated in the second spring accommodating chamber 23. One end of the second spring 231 has a spring seat 23.
4 and the other end thereof is in contact with the spacer 232. The spacer 232 is in contact with the spring cap 233, and the spring cap 233 is in contact with the step 235 formed on the inner wall of the second spring accommodating chamber 23, so that the second spring 231 presses the spring seat 234 against the distance piece 40. Biased in the direction.

The distance piece 40 has a reduced diameter portion 41, and a spacer 4 is provided in the distance piece 40.
2 are provided. The maximum lift of the valve needle 50 is regulated by the distance between the spacer 42 and the reduced diameter portion 41. Further, the initial lift amount is regulated by the distance between the spacer 42 and the spring seat 234.

A fuel injection nozzle 10 is provided on the injection hole 17 side of the fuel injection valve 1, and the fuel injection nozzle 10 is housed in the nozzle body 11 so as to be reciprocally slidable in the axial direction inside the nozzle body 11. And a valve needle 50. The nozzle body 11 has a hollow, substantially cylindrical shape, and has a guide hole 12, a valve seat 13, a fuel passage hole 1 therein.
4, a fuel reservoir 15, a fuel supply hole 16, and a through hole 18 are formed. A plurality of injection holes 17 are formed in the circumferential direction near the tip of the through hole 18.

The guide hole 12 extends axially inside the nozzle body 11, and has one end connected to the open end 19 of the nozzle body 11 and the other end connected to the fuel reservoir 1.
5 is connected. The inner wall of the guide hole 12 has substantially the same inner diameter from the opening end 19 of the nozzle body 11 to the vicinity of the fuel reservoir 15.

As shown in FIG. 1, the valve seat 13 has a truncated conical surface, one end on the large diameter side is continuous with the fuel passage hole 14, and the other end on the small diameter side is connected to the through hole 18. . A contact portion 57 of the valve needle 50 described below can contact the valve seat portion 13. The through hole 18 is formed in the vicinity of the tip of the nozzle body 11 in the axial direction.
And the other end penetrates toward the combustion chamber.
The inner wall of the through hole 18 is formed to have substantially the same diameter from the connection with the valve seat 13 to the end on the combustion chamber side.

A plurality of injection holes 17 are formed in the circumferential direction of the through hole 18 so as to communicate inside and outside of the through hole 18 at the tip of the nozzle body 11. The inlet of the injection hole 17 is opened on the inner wall surface of the through hole 18. As shown in FIG. 2, the fuel passage hole 14 extends in the axial direction inside the nozzle body, one end of which is connected to the valve seat 13, and the other end of which is connected to the fuel reservoir 15. are doing. The fuel reservoir 15 is formed in an annular shape on an inner wall connecting the guide hole 12 and the fuel passage hole 14. A fuel supply hole 16 for supplying fuel from the outside is connected to the fuel reservoir 15. The fuel supply hole 16 is
The nozzle body 11 is formed to be inclined in the axial direction.

The valve needle 50 has a solid cylindrical shape, and includes a neck portion 51, a sliding portion 52, a column portion 53, and a truncated cone portion 5.
4, a seat portion 55 and a needle pin portion 56 as a protruding portion. One end of the neck portion 51 of the valve needle 50 is connected to the pressure pin 60, and the other end is connected to the sliding portion 52. The outer diameter of the neck portion 51 is slightly smaller than the inner diameter of the spacer 42.

The sliding portion 52 has the same outer diameter, is loosely fitted into the guide hole 12 via a clearance, and can reciprocate in the axial direction. One end of the sliding portion 52 has a neck portion 51.
, And the other end is connected to the truncated cone 54. In the truncated cone 54, one end on the large diameter side is connected to the sliding portion 52, and the other end on the small diameter side is connected to the column 53. The column portion 53 has the same outer diameter and can reciprocate in the axial direction. The pillar 53 has one end connected to the truncated cone 54 and the other end connected to the seat 55. The seat portion 55 has one end on the large diameter side connected to the column portion 53 and the other end on the small diameter side connected to the valve needle 50.
It is connected to the needle pin 56 at the tip. Seat part 5
The connection portion between the 5 and the column portion 53 is circular, and this circular portion is a contact portion 57 that contacts the valve seat portion 13 when the valve is closed. When the valve is closed, the fuel injection from the injection hole 17 is shut off by the contact portion 57 sitting on the valve seat portion 13.

The needle pin 56 is formed such that the outer diameter of the sliding surface 564 is substantially the same as the inner diameter of the through hole 18.
The sliding surface 564 can slide on the inner wall of the through hole 18. As shown in FIGS. 1 and 3, a first reduced diameter portion 561, a second reduced diameter portion 562, and a plurality of grooves 563 are formed on the outer wall surface of the needle pin portion 56. In FIG. 3, for easy understanding of the configuration, the injection hole 17 is shown as a vertical state that is not inclined with respect to the axial direction of the through hole 18.

The first reduced diameter portion 561 is formed near the tip of the needle pin portion 56, and the outer diameter of the first reduced diameter portion 561 is formed to be smaller than the outer diameter of the sliding surface 564. . The second reduced diameter portion 562 is formed on the fuel downstream side of the seat portion 55, and the outer diameter of the second reduced diameter portion 562 is formed to be the same as the outer diameter of the first reduced diameter portion 561. The groove portion 563 is formed on the outer wall surface of the needle pin portion 56 so as to communicate the first reduced diameter portion 561 and the second reduced diameter portion 562.

The first reduced diameter portion 561 and the second reduced diameter portion 562 are
As shown in FIG. 1, when the valve needle 50 is not lifted, that is, when the lift amount of the valve needle 50 is zero, the injection hole 17 is formed at a position to vertically sandwich the injection hole 17. Outer diameters of the first reduced diameter portion 561 and the second reduced diameter portion 562,
By changing the length in the axial direction and the interval between the two reduced diameter portions, the opening area of the injection hole at a predetermined lift amount of the valve needle 50 can be arbitrarily set.

As shown in FIG. 3, the groove 563 is formed in the through hole 1.
8, which is always in communication with a part of the plurality of injection holes 17 opened on the inner wall of the valve needle 8, and as shown in FIG. Is passed through the groove 563 and is injected from the injection hole 17.

On the other hand, as shown in FIG.
At the time of a high lift of 0, the first reduced diameter portion 561 communicates with all of the plurality of injection holes 17 opened on the inner wall of the through hole 18 and passes through the opening between the valve seat portion 13 and the contact portion 57. The fuel that was removed
It is guided to the first reduced diameter portion 561 via 63 and is injected from the injection hole 17.

The second reduced diameter portion 562 is provided on the fuel downstream side of the contact portion, and when the valve needle 50 is lifted, the valve seat 1
When the fuel passes through the opening between the third member 3 and the contact portion 57 and also after the passage, the flow resistance of the fuel is reduced.

Next, the operation of the fuel injection valve 1 configured as described above will be described. A predetermined amount of fuel is pumped at a predetermined time from a high-pressure pump, and the high-pressure fuel is supplied to a fuel inlet 21 through a fuel pipe.
Supplied to The high-pressure fuel is stored in the fuel passage hole 14 via the fuel passage 24, the fuel supply hole 16, and the fuel reservoir 15. The fuel pressure in the fuel passage hole 14 increases, and the force acting on the valve needle 50 due to the fuel pressure increases to the first level.
When the force becomes larger than the urging force of the spring 221, the valve needle 50 is lifted upward in FIG. 2, and the contact portion 57 is separated from the valve seat 13 to open.

At low speed and low load, the lift amount of the valve needle 50 is relatively small, so that the fuel that has passed through the opening between the valve seat 13 and the abutment portion 57 is one as shown by an arrow in FIG. The portion is injected from the injection hole 17 through a path of the second reduced diameter portion 562 to the groove portion 563, and the remaining part is injected by a path of the second reduced diameter portion 562, the groove portion 563, the first reduced diameter portion 561, and the groove portion 563. Injected from 17. At this time, as shown in FIG. 3, the fuel is in communication with the groove 563 because the groove 563 communicates only with a part of the injection hole 17 and the other injection holes 17 are sealed with the sliding surface 564. It is injected only from some injection holes 17. Therefore, the total opening area of the injection hole 17 is reduced, and the pressure of the fuel injected from the injection hole 17 is sufficiently maintained at the pressure required for atomizing the fuel.

When the fuel pressure in the fuel passage hole 14 increases, the lift amount of the valve needle 50 increases, and the spacer 42 comes into contact with the spring seat 234. This state is the initial lift state of the valve needle 50. When the force acting on the valve needle 50 due to the fuel pressure in the fuel passage hole 14 becomes larger than the sum of the urging force of the first spring 221 and the urging force of the second spring 231, the spacer 42 compresses the distance piece 40. The valve needle 50 comes into contact with the diameter portion 41 and reaches the full lift state.

At the time of high speed and high load, the lift amount of the valve needle 50 is relatively large, so that the fuel that has passed through the opening between the valve seat 13 and the abutting portion 57 is discharged as shown by an arrow in FIG. 2 Reduced diameter portion 562, groove portion 563, first reduced diameter portion 5
It is injected from the injection hole 17 along the path 61. At this time,
The first reduced diameter portion 561 communicates with all the injection holes 17 and the fuel is injected from all the injection holes 17 at the same time.
7 has a larger total opening area, and the required amount of fuel is sufficiently injected.

When the high-pressure pump nears the end of fuel pumping, the fuel pressure in the fuel passage hole 14 decreases, and the force acting on the valve needle 50 due to the fuel pressure in the fuel passage hole 14 is increased by the first spring 221 and the second spring. 231
Is smaller than the sum of the urging forces of
Moves downward in FIG. 2, and the abutment portion 57 is seated on the valve seat portion 13 to terminate the fuel injection.

In the first embodiment, the valve needle 5
The opening area of the injection hole 17 changes according to the lift amount of 0,
An optimal fuel injection amount can be secured according to the load state of the engine. That is, when the lift amount of the valve needle 50 is small and the load is low and the load is low, the fuel is injected only from a part of the injection holes 17 communicating with the groove 563, and the valve seat 1
Since the opening area of the injection hole 17 can be reduced as compared with the area of the opening between the valve seat 3 and the contact portion 57, the throttle phenomenon at the opening between the valve seat portion 13 and the contact portion 57 is reduced. The injected fuel can be maintained at a high pressure. Also,
When the valve needle 50 is lifted at a high speed and at a high load, the first reduced diameter portion 561 communicates with all the injection holes 17 and the fuel is injected from all the injection holes 17. Can be secured. Thus, improved atomization characteristics of the fuel in the total lift range of the valve needle 50 with a simple structure, soot in the exhaust gas, thereby reducing such NO _x, it is possible to reduce the consumption of fuel.
Further, since the structure is simple, the processing is easy and the manufacturing cost can be reduced.

In the first embodiment, the needle pin 56 at the tip of the valve needle 50 is
Slidable with the inner wall of the valve needle 50, the eccentricity of the valve needle 50 can be reduced. Therefore, damage caused by eccentricity of the valve needle 50 or abnormal wear can be prevented.

Further, in the first embodiment, since the tip of the needle pin portion 56 is exposed through the through hole 18 into the combustion chamber of the engine, when the valve needle 50 is opened, the combustion pressure of the fuel in the combustion chamber changes. The force acting on the valve needle 50 urges the valve needle 50 in the opening direction. Therefore, the valve opening speed of the valve needle 50 can be increased, and the balance of the oil pressure acting on the valve needle 50 when the pressure of the fuel supplied to the fuel injection valve 1 is high can be easily maintained.

(Second Embodiment) FIG. 6 shows a second embodiment in which the present invention is applied to a fuel injection valve for a diesel engine. Components substantially the same as those in the first embodiment are denoted by the same reference numerals. In the second embodiment, the inside of the combustion chamber of the through hole 18 of the nozzle body 11 is not penetrated, and the shape of the sliding surface 564 of the needle pin 56 at the tip of the valve needle 50 is changed. Also, the sliding surface 564 on the tip side is omitted.

In the second embodiment, as in the first embodiment, the opening area of the injection hole 17 can be changed according to the lift amount of the valve needle 50. For example, as shown in FIG. 6, when the valve needle 50 has a small lift amount at a low speed and a low load, the fuel that has passed through the opening between the valve seat portion 13 and the abutment portion 57 partially passes from the second reduced diameter portion 562 to the groove portion. 563 from the injection hole 17 and the remaining part is the second reduced diameter portion 56.
2. Injection is performed from the injection hole 17 along a path of the groove 563, the first reduced diameter portion 561, and the groove 563.

When the valve needle 50 is lifted at a high speed and under a high load, the fuel that has passed through the opening between the valve seat portion 13 and the contact portion 57 flows through the second reduced diameter portion 562, the groove portion 563, the first
It is injected from the injection hole 17 along the path of the reduced diameter portion 561.

Also in the second embodiment, the valve needle 5
The opening area of the injection hole 17 changes according to the lift amount of 0,
An optimal fuel injection amount can be secured according to the load state of the engine. Therefore, the atomization characteristics of the fuel in the entire lift region of the valve needle 50 can be improved with a simple structure, and the fuel consumption can be reduced. Further, since the structure is simple, the processing is easy and the manufacturing cost can be reduced.

In the embodiments described above, the first reduced diameter portion 561 and the second reduced diameter portion 5
Although the two reduced diameter portions 62 are formed, the same effect as in the present embodiment can be obtained by omitting the second reduced diameter portion 562 and forming only the first reduced diameter portion 561 as shown in FIGS. Obtainable.

In a plurality of embodiments of the present invention, the fuel injection nozzle of the present invention is applied to a fuel injection valve for a diesel engine. However, the present invention may be applied to a fuel injection valve for a gasoline engine.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of a main part of a fuel injection nozzle according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a fuel injection valve to which the fuel injection nozzle according to the first embodiment of the present invention is applied.

FIG. 3 is a cross-sectional view illustrating a state where the fuel injection nozzle according to the first embodiment of the present invention is cut along a line AA in FIG. 1;

FIG. 4 is an explanatory diagram showing a fuel flow at the time of a low lift of the fuel injection nozzle according to the first embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a fuel flow at the time of a high lift of a fuel injection nozzle according to the first embodiment of the present invention.

FIG. 6 is a sectional view showing a fuel injection nozzle according to a second embodiment of the present invention.

FIG. 7 is a cross-sectional view illustrating an example in which a second reduced diameter portion of the fuel injection nozzle according to the first embodiment of the present invention is omitted.

FIG. 8 is a sectional view showing an example in which a second reduced diameter portion of a fuel injection nozzle according to a second embodiment of the present invention is omitted.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fuel injection valve 10 Fuel injection nozzle 11 Nozzle body 13 Valve seat 17 Injection hole 18 Through hole 50 Valve needle 56 Needle pin part (projection part) 57 Contact part 561 First reduced diameter part 562 Second reduced diameter part 563 Groove part 564 sliding surface

Claims (3)

[Claims] 1. A through-hole penetrating in the axial direction so as to communicate inside and outside, a plurality of injection holes having one end communicating with the through-hole and the other end communicating with the outside, and a valve seat at a fuel upstream side of the through-hole. A nozzle body having a portion, a contact portion which is supported by the nozzle body so as to be reciprocally slidable, and which can be seated on the valve seat portion, and a protruding portion which can slide on an inner wall surface of the through hole; A valve needle that abuts and separates from the valve seat and seats on the valve seat to flow and shut off fuel, and the protrusion that slides on the inner wall surface of the through hole is at least A first reduced diameter portion formed at one location near the tip of the protruding portion, and a plurality of grooves on an outer wall surface that axially communicate the fuel downstream side of the contact portion and the reduced diameter portion, The lift amount of the valve needle is smaller than a predetermined lift amount When the groove is a fuel injection nozzle, characterized in that communicating with a portion of the injection hole. 2. The fuel injection nozzle according to claim 1, wherein when the lift amount of the valve needle is larger than a predetermined lift amount, the first reduced diameter portion communicates with all of the injection holes. 3. The projection according to claim 1, wherein the projection has a second reduced diameter portion formed near the contact portion.
Or the fuel injection nozzle according to 2.