JP2001207939A - Fuel injection nozzle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection nozzle capable of suppressing oscillating vibration of a retainer and preventing corrosion of the retainer and a spring storing chamber. SOLUTION: This fuel injection nozzle 4 has a nozzle body 12 with an opened nozzle hole 19. On the nozzle body 12, a nozzle needle 24 for opening and closing the nozzle hole 19 is held and the nozzle body 12 is connected with a nozzle holder 10 having the spring storing chamber 50 in which one end of the nozzle needle 24 is situated. In the spring storing chamber 50, excessive fuel is returned through clearance S1 between the nozzle needle 24 and the nozzle body 12. In the spring storing chamber 50, a pressure spring 32 and the retainer 54 for transmitting pressing force of the spring 32 to the nozzle needle 24 are stored. The retainer 54 has a guide part 56 for constraining the attitude of the retainer 54 by being slidably fitted into the spring storing chamber 50.

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 mainly used for a diesel engine, and more particularly to a structure of a retainer for transmitting a pressing force of a pressure spring to a nozzle needle.

[0002]

2. Description of the Related Art In a diesel engine, air sucked into a combustion chamber is compressed at a high compression ratio, thereby injecting fuel into high-temperature, high-pressure air. It is carried out. Therefore, in order to achieve good combustion in diesel engines,
It is effective to inject the fuel pressurized to a pressure higher than the air pressure in the combustion chamber into the combustion chamber so that the fuel is easily ignited by the compression heat.

FIG. 3 shows a conventional fuel injection device 1 for a diesel engine. The fuel injection device 1 includes an in-line fuel injection pump 2 for pressurizing fuel, and a fuel injection nozzle 4 connected to a distribution port 2 a of the fuel injection pump 2 via a fuel injection pipe 3.

[0004] The fuel injection nozzle 4 is mounted on a cylinder head 5 of a diesel engine. The cylinder head 5 constitutes a combustion chamber 7 in cooperation with the head portion of the piston 6, and fuel is directly injected into the combustion chamber 7 via the fuel injection nozzle 4.

As shown in FIG. 3, the fuel injection nozzle 4 is
The nozzle holder 10 includes a nozzle body 12 coaxially fixed to a tip end of the nozzle holder 10 via a retaining nut 11, and a distance piece 13 interposed between the nozzle holder 10 and the nozzle body 12. ing.

A spring accommodating chamber 14 is formed inside the nozzle holder 10. Spring accommodation room 14
Is opened at the mating surface between the nozzle holder 10 and the distance piece 13. An adjusting screw 15 is screwed on the axis of the nozzle holder 10 from the opposite side of the nozzle body 12. The adjusting screw 15 is used for the spring accommodation chamber 1.
4, and a disc-shaped spring seat 15 a is attached to the tip of the adjusting screw 15.

The nozzle body 12 has a small-diameter circular top 16 at the tip. The crown 16 protrudes into the combustion chamber 7. As shown in FIG. 4 which is a partially enlarged view of FIG. 3, a guide hole 18 is formed coaxially inside the nozzle body 12. One end of the guide hole 18 is opened at the mating surface between the nozzle body 12 and the distance piece 13, and the other end of the guide hole 18 is closed inside the circular top 16. A plurality of injection holes 19 are opened at the apex 16 of the nozzle body 12, and these injection holes 19 are connected to the other end of the guide hole 18.

At the other end of the guide hole 18, a large-diameter fuel reservoir 20 is formed. The fuel reservoir 20 is connected to a fuel supply passage 21. The fuel supply passage 21 includes the nozzle holder 10, the distance piece 13 and the nozzle body 1.
2, the upstream end of the fuel supply passage 21 is connected to the fuel injection pipe 3 via an inlet connector 22. A valve seat surface 23 is formed at the other end of the guide hole 18. This valve seat surface 23
Is located between the fuel reservoir 20 and the injection hole 19.

A nozzle needle 24 is fitted in the guide hole 18 of the nozzle body 12 so as to reciprocate in the axial direction. The nozzle needle 24 has a small-diameter journal portion 25 at one end along the axial direction. Journal 25
Extends coaxially with the nozzle needle 24 in the axial direction. Therefore, a shoulder portion 26 is formed at the boundary between one end of the nozzle needle 24 and the journal portion 25 along the radial direction of the nozzle needle 24. The other end of the nozzle needle 24 opposite to the journal 25 faces the fuel reservoir 20, and the other end of the nozzle needle 24 is formed with a seal portion 27 in contact with the valve seat surface 23. .

The nozzle needle 24 has a sealing portion 27
Is in a closed position (shown in FIG. 4B) of the guide hole 18 in contact with the valve seat surface 23 and an open position (shown in FIG. 4A) in which the seal portion 27 is separated from the valve seat surface 23. It is supported by the nozzle body 12 so as to be able to reciprocate over it.

When the nozzle needle 24 is moved to the closed position, communication between the fuel reservoir 20 and the injection hole 19 is interrupted. When the nozzle needle 24 is moved from the closed position to the open position, the fuel reservoir 20 communicates with the injection hole 19,
The fuel supplied to the fuel reservoir 20 is injected into the combustion chamber 7 through the injection holes 19.

The nozzle needle 24 and the guide hole 18
And a clearance (not shown) is formed between them. Excess fuel flowing into this clearance causes
The nozzle needle 24 and the guide hole 18 are lubricated.

As shown in FIG. 4, the distance piece 1
3 is a first end face 2 abutted on the nozzle holder 10
8a, and a second end face 28b abutting against the nozzle body 12. These end faces 28a, 28b
In order to enhance the adhesion between the nozzle holder 10 and the nozzle body 12, the polishing is flatly polished, thereby ensuring the liquid tightness of the abutting portion between the nozzle holder 10 and the nozzle body 12.

The distance piece 13 has a through hole 30. The through-hole 30 includes a small-diameter hole 30a having a smaller diameter than the guide hole 18 and a large-diameter hole 30b coaxially connected to the small-diameter hole 30a. Through hole 30
The small diameter hole 30a is opened at the center of the second end face 28b, and the nozzle needle 2 is inserted into the small diameter hole 30a.
Four journal portions 25 are inserted. The tip of the journal 25 penetrates the small-diameter hole 30a and enters the large-diameter hole 30b. Large-diameter hole portion 30 of through hole 30
“b” is opened at the center of the first end surface 28a, and is connected to the spring accommodating chamber 14.

As shown in FIG. 4A, when the nozzle needle 24 is moved to the open position, the shoulder 26 of the nozzle needle 24 is
Abuts on the second end surface 28b. For this reason, the second end surface 28b of the distance piece 13 and the shoulder portion 26 function as a stopper that determines the lift amount of the nozzle needle 24 in cooperation with each other.

The spring accommodating chamber 14 accommodates a pressure spring 32 for urging the nozzle needle 24 toward the closed position, and a retainer 33 for transmitting the pressing force of the pressure spring 32 to the nozzle needle 24. .

As the pressure spring 32, a compression coil spring is used. Both ends of the pressure spring 32 are cut and polished at right angles to the center axis of the spring.

The retainer 33 has a cylindrical main body 34a,
And a flange-shaped seat portion 34b projecting radially outward from an intermediate portion of the main body 34a. One end of the main body 34a is inserted into the large-diameter hole 30b of the through hole 30 and faces the tip of the journal 25 of the nozzle needle 24. A concave portion 35 is formed on one end surface of the main body 34a, and the tip of the journal portion 25 is fitted into the concave portion 35. The tip of the journal part 25 is
It hits the bottom of 5. For this reason, the retainer 33
Is coaxially connected to the nozzle needle 24 by fitting the journal 25 into the concave portion 35, whereby the posture in the spring accommodating chamber 14 is restricted.

The seat portion 34b projects radially outward from an intermediate portion of the main body 34a. The outer peripheral surface of the seat portion 34b is separated without contacting the inner surface of the spring accommodating chamber 14, and a relatively large gap 37 is formed between the two. The seat portion 34b faces the spring seat 15a of the adjusting screw 15, and the seat portion 34b and the spring seat 15
The pressure spring 32 is interposed in a compressed state between the pressure spring 32 and the pressure spring 32. The cut and polished ends of the pressure spring 32 are pressed against the seat portion 34b and the spring seat 15a, respectively.

Therefore, the pressure spring 32
Always urges the nozzle needle 24 toward the circular top 16 of the nozzle body 12 via the retainer 33, whereby the nozzle needle 24 is held in the closed position.

The fuel flows between the journal portion 25 of the nozzle needle 24 and the small diameter hole 30a of the through hole 30 and between the main body 34a of the retainer 33 and the large diameter hole 30b of the through hole 30. An allowable gap 38 is formed. For this reason, the nozzle needle 24 and the nozzle body 12
The excess fuel lubricated is guided to the spring accommodating chamber 14 through the clearance or gap 38 between the nozzle needle 24 and the guide hole 18, and is returned to the fuel return passage 39 of the nozzle holder 10 along the adjusting screw 15 therefrom. It is supposed to be.

In the fuel injection nozzle 4 having such a configuration, the pressurized fuel sent from the fuel injection pump 2 is
The fuel reaches the fuel reservoir 20 through the fuel supply passage 21, and the pressure of the fuel is applied to the other end of the nozzle needle 24 facing the fuel reservoir 20. As a result, the nozzle needle 24 receives a force in a direction in which the seal portion 27 is detached from the valve seat surface 23. When this force exceeds the pressing force of the pressure spring 32, the nozzle needle 24 moves from the closed position to the open position, and the sealing portion 27 of the nozzle needle 24 is moved.
From the valve seat surface 23. As a result, the injection hole 19 is opened, and fuel is injected into the combustion chamber 7 through the injection hole 19.

When the supply of fuel from the fuel injection pump 2 is completed, the pressure of the fuel applied to the nozzle needle 24 decreases, and this nozzle needle 24
It is returned to the closed position by the pressing force of 2. Therefore, the seal portion 27 of the nozzle needle 24 comes into contact with the valve seat surface 23, the injection hole 19 is closed, and the fuel injection into the combustion chamber 7 ends.

[0024]

According to the conventional fuel injection nozzle 4, the retainer 33 for transmitting the pressing force of the pressure spring 32 to the nozzle needle 24 has a concave portion 35 at one end of the main body 34a. The spring storage chamber 1 is inserted into the
4. Therefore, the retainer 33 is supported in a cantilever state with respect to the nozzle needle 24,
The position of the retainer 33 in the spring accommodating chamber 14 is restricted by the fitting portion between the concave portion 35 and the journal portion 25.

At this time, in the conventional fuel injection nozzle 4, the fitting depth between the journal portion 25 and the concave portion 35 is set to be small so as to allow a slight inclination of the retainer 33. It is difficult to support firmly,
When the nozzle needle 24 reciprocates with the operation of the fuel injection nozzle 4, the retainer 33 may swing like a pendulum with the fitting portion with the journal 25 as a fulcrum.

The swinging vibration of the retainer 24 has a close relationship with the pressure spring 32, and the reason will be described below. That is, the pressure spring 32
Are polished so as to be perpendicular to the center axis of the spring so that a sufficient contact area between the spring seat 15a and the seat portion 34b of the retainer 33 can be secured.

However, it is actually difficult to machine both ends of the pressure spring 32 so as to maintain accurate parallelism.
With the spring seat 15a and the seat portion 3 of the retainer 33.
4b, the pressure spring 3
2 is slightly inclined.

As a result, a bias occurs in the pressing force applied to the retainer 33, so that the retainer 33 swings about the fitting portion with the journal 25 as a fulcrum, and the fuel injection nozzle 4
During the operation, the outer peripheral surface of the seat portion 34b of the retainer 33 repeats the movement of approaching or moving away from the inner surface of the spring accommodating chamber 14.

Then, surplus fuel is returned to the spring accommodating chamber 14 in which the retainer 33 is accommodated.
A phenomenon occurs in which the high-pressure fuel flowing through the gap 37 between the outer peripheral surface of the seat portion 34b and the inner surface of the spring accommodating chamber 14 is rapidly throttled or released by the movement of the seat portion 34b as described above. For this reason, the retainer 33
Causes cavitation on the inner surface of the spring housing chamber 14 and the inner surface of the spring housing chamber 14, which causes erosion due to impact on the surface of the retainer 33 and the inner surface of the spring housing chamber 14.

Thus, the retainer 3 by erosion
When the corrosion of No. 3 progresses, the retainer 33 is always subjected to the large pressing force of the pressure spring 32,
This retainer may be damaged or deformed, which lowers the reliability of the fuel injection nozzle 4.

The present invention has been made in view of the above circumstances, and it is possible to suppress the swinging vibration of a retainer which receives the pressing force of a pressure spring, and to prevent the corrosion of the retainer and the spring accommodating chamber. The purpose is to provide an injection nozzle.

[0032]

In order to achieve the above object, a fuel injection nozzle according to the present invention comprises: a nozzle body having an injection hole connected to a fuel supply passage through which pressurized fuel is supplied; A nozzle needle that is movably held and opens and closes the injection hole; a spring housing that is connected to the nozzle body, one end of the nozzle needle faces, and excess fuel is returned through a clearance between the nozzle needle and the nozzle body. A nozzle holder having a chamber; a pressure spring accommodated in a spring accommodating chamber of the nozzle holder for pressing the nozzle needle in a closing direction; and a pressure spring interposed between one end of the nozzle needle and the pressure spring. While transmitting the pressing force of the spring to the nozzle needle, And a; following the opening and closing of the nozzle needle and the retainer is reciprocated in the spring accommodation chamber. The retainer is characterized in that it has a guide portion that slidably fits in the spring accommodating chamber to restrain the attitude of the retainer.

In order to achieve the above object, a fuel injection nozzle according to the present invention has a nozzle body having an injection hole connected to a fuel supply passage through which pressurized fuel is supplied; A nozzle needle that opens and closes the injection hole; and is connected to the nozzle body,
A nozzle holder having a spring accommodating chamber; interposed between the nozzle holder and the nozzle body, one end of the nozzle needle is inserted, and excess fuel flowing into a clearance between the nozzle needle and the nozzle body is removed from the nozzle holder. A distance piece having a through hole leading to a spring accommodating chamber; a pressure spring accommodated in the spring accommodating chamber of the nozzle holder for pressing the nozzle needle in a closing direction; and one end of the nozzle needle and the pressure spring. A retainer that is interposed therebetween and transmits the pressing force of the pressure spring to the nozzle needle, and reciprocates in the spring accommodating chamber following the opening and closing operation of the nozzle needle. The retainer is characterized in that it has a guide portion that slidably fits into a through hole of the distance piece to restrict the attitude of the retainer.

Further, in order to achieve the above object, a fuel injection nozzle according to the present invention has a nozzle body having an injection hole connected to a fuel supply passage through which pressurized fuel is supplied; A nozzle needle for opening and closing the injection hole; a spring accommodating chamber; and a partition interposed between the spring accommodating chamber and the nozzle body. One end of the nozzle needle is inserted into the partition. A nozzle holder having a through-hole for introducing surplus fuel flowing into a clearance between the nozzle needle and the nozzle body to the spring housing chamber; housed in the spring housing chamber of the nozzle holder, and closing the nozzle needle in a closing direction. A pressure spring for pressing the nozzle needle; one end of the nozzle needle and the pressure spring It is interposed between the ring, the pressing force of the pressure spring with important to the nozzle needle, and a retainer is reciprocated following the opening and closing of the nozzle needle in the spring accommodating chamber; and a. The retainer is characterized in that it has a guide portion that slidably fits into the through hole of the partition portion to restrict the attitude of the retainer.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIG.

In the first embodiment, the basic structure of a fuel injection device including a fuel injection nozzle is shown in FIG.
4 is the same as that of the conventional technology shown in FIG. 4, and only the differences from the conventional technology will be described here. The same components as those of the conventional technology will be denoted by the same reference numerals and the description thereof will be omitted. Omitted.

As shown in FIG. 1, the nozzle holder 10 of the fuel injection nozzle 4 has a spring accommodating chamber 50 for accommodating the pressure spring 32. The spring accommodating chamber 50 has a cylindrical shape coaxial with the nozzle holder 10, and the inner surface of the spring accommodating chamber 50 is smoothly finished. Further, the spring housing chamber 50 is opened at a surface where the spring piece 50 and the distance piece 13 abut.

The distance piece 13 has a through hole 51 at the center thereof. The through hole 51 is provided in the guide hole 18.
A small-diameter hole 52a having a smaller diameter than the small-diameter hole 52;
and a tapered portion 52b connected to a.

The small-diameter hole 52a is provided in the distance piece 1
3, the nozzle body 12 is opened to the second end face 28b.
The journal portion 25 of the nozzle needle 24 is coaxially inserted into the small-diameter hole portion 52a. A gap 53 is formed between the inner surface of the small-diameter hole portion 52a and the outer peripheral surface of the journal portion 25 to allow fuel to flow. The journal 25
Is located at the boundary between the small diameter hole portion 52a and the tapered portion 52b.

The tapered portion 52b is formed by the distance piece 1
3 is open to the first end surface 28 a and is coaxially connected to the spring accommodating chamber 50. This tapered portion 52b is
The diameter gradually increases as it proceeds from the small-diameter hole 52a toward the spring accommodating chamber 50.

The spring accommodating chamber 50 accommodates a retainer 54 for transmitting the pressing force of the pressure spring 32 to the nozzle needle 24. The retainer 54 has a disk-shaped seat portion 55 that receives the other end of the pressure spring 32. The outer peripheral portion of the seat portion 55 is fitted in the cylinder accommodating chamber 50 so as to be slidable in the axial direction.
4 is restrained.

For this reason, in this embodiment, the retainer 5
The outer peripheral portion of the seat portion 55, which is the maximum outer diameter portion of No. 4, functions as a guide portion 56 for restraining the attitude of the retainer 54.

A clearance S1 is formed between the guide portion 56 of the retainer 54 and the inner surface of the spring accommodating chamber 14 to allow the fuel to flow. The clearance S1 is set to a small value of 0.3 mm or less in diameter of the retainer 54 and the spring accommodating chamber 14, so that an appropriate damping force is generated when the fuel passes through the clearance S1. ing.

The retainer 54 has a convex portion 58 at the center of the back surface of the sheet portion 55. The convex portion 58 is provided in the seat portion 5.
5 protrudes coaxially toward the journal portion 25 of the nozzle needle 24, and has a large-diameter hole portion 52 b of the through hole 51.
Is located inside. The tip of the convex portion 58 is a contact surface 58 a curved in a spherical shape, and the top of the contact surface 58 a is in point contact with the tip surface of the journal 25.

The outer peripheral surface of the convex portion 58 is connected to the back surface of the sheet portion 55 with a smooth curvature, and between the outer peripheral surface of the convex portion 58 and the inner surface of the large-diameter hole portion 52b. A space 59 that allows the flow of fuel is formed.

In such a configuration, when the nozzle needle 24 reciprocates with the operation of the fuel injection nozzle 4, the retainer 54 reciprocates in the spring accommodating chamber 50 following the reciprocation. At this time, the retainer 54 is provided on the outer peripheral portion of the seat portion 55 for receiving the pressure spring 32 with the guide portion 5.
The guide portion 56, which is the largest outer diameter portion of the retainer 54, is directly slidably fitted in the spring accommodating chamber 50.

Therefore, the attitude of the retainer 54 is restricted by the inner surface of the spring accommodating chamber 50,
The clearance S1 between the inner surface of the spring accommodating chamber 50 and the retainer 54 can be significantly reduced as compared with the related art. Therefore, even if the pressure spring 32
Even if there is a bias in the pressing force applied to the retainer 54 due to the inclination, the swinging vibration of the retainer 54 can be prevented, and the amplitude of the retainer 54 in the radial direction of the cylinder housing chamber 50 can be reduced.

As a result, the high-pressure fuel flowing through the clearance S1 is not sharply throttled or released by the retainer 54, and cavitation occurs on the surface of the retainer 54 and the inner surface of the cylinder accommodating chamber 50 as compared with the conventional art. It becomes difficult.

In the process of moving the nozzle needle 24 from the closed position to the open position, the retainer 54 is pushed up through the nozzle needle 24, so that the fuel pressure below the retainer 54 decreases. Cavitation may occur. However, according to the above configuration, by setting the clearance S1 to a narrow value of 0.3 mm or less, the fuel pressure attenuates when fuel passes through the clearance S1, so that even if cavitation occurs, the erosion progresses. I will not do it. For this reason, corrosion of the retainer 54 and the spring accommodating chamber 50 and damage caused thereby can be prevented, and the reliability of the fuel injection nozzle 4 can be improved.

On the other hand, as the pressure of the fuel supplied from the fuel injection pump 2 to the fuel injection nozzle 4 increases, the force for detaching the nozzle needle 24 from the valve seat surface 23 increases, and the nozzle needle 24 The speed of moving from the closed position to the open position increases.

At this time, the shoulder portion 26 of the nozzle needle 24 is connected to the second end surface 28 of the distance piece 13.
b, the nozzle needle 24 is held at the open position, and as the moving speed of the nozzle needle 24 increases due to the high pressure of the fuel, the shoulder portion 26 of the nozzle needle 24 increases.
Impact on the second end surface 28b of the distance piece 13 increases.

Then, in the conventional fuel injection nozzle 4 shown in FIG. 4, the journal portion 25 of the nozzle needle 24 is fitted into the concave portion 35 of the retainer 33. It is necessary to extend the body 34a in the direction of the nozzle needle 24.

For this reason, the depth dimension of the large-diameter hole portion 30a of the through hole 30 into which the retainer 33 enters must be set large, and the depth dimension of the small-diameter hole portion 30b is reduced accordingly. As shown in FIG. 4A, the wall pressure T1 from the second end surface 28b of the distance piece 13 to the end of the small-diameter hole 30b is reduced.

As a result, the rigidity of the distance piece 13 around the small diameter hole 30b decreases, and the nozzle needle 2
When the shoulder 26 of the No. 4 abuts against the second end face 28b of the distance piece 13, the impact force may deform the central portion of the second end face 28b where the small-diameter hole 30b is opened. Therefore, distance piece 1
The sealing performance of the abutting portion between the nozzle body 3 and the nozzle body 12 is impaired, which causes fuel leakage.

At the same time, during the operation of the fuel injection nozzle 4, the shoulder 26 of the nozzle needle 24 repeatedly collides with the center of the second end face 28b, so that the rigidity of the center of the second end face 28b is insufficient. In this case, fretting corrosion is likely to occur here, and in severe cases, the central portion of the second end surface 28b may be depressed. As a result, the function of the distance piece 13 as a stopper is impaired, and the lift amount of the nozzle needle 24 fluctuates.

On the other hand, according to the fuel injection nozzle 4 of the present invention disclosed in FIG. 1, the posture of the retainer 54 is restrained by directly fitting the retainer 54 into the spring accommodating chamber 50. The journal portion 25 of the needle 24 need only be abutted, and there is no need to fit the retainer 54 and the journal portion 25 in an uneven manner.

For this reason, the depth dimension of the small diameter hole 52a of the distance piece 13 can be set to be equal to the axial length of the journal 25, and the distance from the second end face 28b of the distance piece 13 to the end of the small diameter hole 52b. , The rigidity of the distance piece 13 around the small-diameter hole 52b can be increased.

As a result, the shoulder 26 of the nozzle needle 24 is moved to the second end face 2 of the distance piece 13.
8b, the second end surface 28b is less likely to be deformed. Therefore, the sealing performance of the abutting portion between the distance piece 13 and the nozzle body 12 is not impaired, and fuel leakage from the abutting portion can be prevented, so that it is possible to cope with an increase in the fuel pressure without difficulty.

Further, according to the fuel injection nozzle 4 shown in FIG. 1, a clearance S1 exists between the guide portion 56 of the retainer 54 and the inner surface of the spring accommodating chamber 50 so as to allow the fuel to flow therethrough. The clearance S1 is set to a small value of 0.3 mm or less so as to generate a damping force on the fuel passing therethrough. For this reason, when the retainer 54 moves following the nozzle needle 24, the clearance S1 becomes a kind of orifice, and the pressure difference of the fuel generated on both sides of the retainer 54 can be gently eliminated. The upper limit of the speed of moving from the closed position to the open position can be limited.

Accordingly, the impact force when the shoulder portion 26 of the nozzle needle 24 collides with the second end surface 28b of the distance piece 13 under the fuel pressure can be reduced, and the fretting corrosion of the second end surface 28b can be reduced. It is possible to prevent the second end face 28b from being depressed or the like. Therefore, the fluctuation of the lift amount of the nozzle needle 24 can be prevented, and the reliability of the operation of the fuel injection nozzle 4 is improved as compared with the related art.

As described above, according to the fuel injection nozzle 4 shown in FIG. 1, even when the fuel pressure supplied from the fuel injection pump 2 is increased, fluctuation of the lift amount of the nozzle needle 24 and fuel leakage are prevented. As a result, sufficient reliability can be ensured, and higher-pressure fuel can be injected into the combustion chamber 7. Therefore, atomization of fuel in the combustion chamber 7 is promoted, and favorable combustion with less irregular combustion can be obtained.

According to the fuel injection nozzle 4 shown in FIG.
The retainer 54 may simply contact the contact surface 58a at the tip of the convex portion 58 against the tip surface of the journal portion 25, and the concave portion 3 into which the journal portion 25 fits as in the related art.
5 need not be formed. At the same time, the through-hole 51 of the distance piece 13 may be formed in a simple funnel shape having a tapered portion 52b. Therefore, the shapes of the retainer 54 and the distance piece 13 can be simplified, and therefore, there is an advantage that complicated processing is not required and the cost of the fuel injection nozzle 4 is reduced.

The present invention is not limited to the first embodiment, and FIG. 2A shows a second embodiment of the present invention.

The second embodiment is different from the first embodiment in the structure for supporting the retainer 60.
The other basic configuration of the fuel injection nozzle 4 is the same as that of the first embodiment.

As shown in FIG. 2A, the distance piece 61 interposed between the nozzle holder 10 and the nozzle body 12 has a thickness T3 greater than the axial length L1 of the journal 25 of the nozzle needle 24. It is set large.
A through hole 62 is formed at the center of the distance piece 61.
The journal portion 25 is formed in the through hole 62.
Is inserted.

A retainer 60 for transmitting the pressing force of the pressure spring 32 to the nozzle needle 24 has a disc-shaped sheet portion 63 for receiving the other end of the pressure spring 32 and a columnar shape projecting from the center of the rear surface of the sheet portion 63. And a guide portion 64.

The seat portion 63 is accommodated in the cylinder accommodating chamber 50, and a gap 65 is formed between the outer peripheral portion of the seat portion 63 and the inner surface of the cylinder accommodating chamber 14 to allow fuel to flow. I have. The guide part 64 is a seat part 63
Are arranged coaxially with respect to. This guide portion 64
The through hole 62 is fitted slidably in the axial direction,
By this fitting, the attitude of the retainer 60 in the spring accommodating chamber 50 is restricted.

The distal end surface of the guide portion 64 is a spherically curved contact surface 64a, and the top of the contact surface 64a is in point contact with the distal end surface of the journal portion 25. For this reason, the guide portion 64 of the retainer 60 and the journal portion 25 of the nozzle needle 24 abut against each other inside the through hole 62.

A clearance is formed between the inner surface of the through hole 62 and the guide portion 64 of the retainer 60 and the journal portion 25 of the nozzle needle 24 to allow the fuel to flow therethrough. It is connected to the room 50.

According to such a configuration, the retainer 60
Since the posture in the spring accommodating chamber 50 is restrained by fitting the guide portion 64 into the through hole 62 of the distance piece 13, the fitting length necessary to support the retainer 60 is sufficiently secured. be able to.

For this reason, the posture of the retainer 60 becomes stable,
Even if the pressure spring 32 is inclined and the retainer 60
Even if the pressing force applied to the
Of the cylinder housing chamber 5 can be prevented.
The amplitude of the retainer 60 in the radial direction of 0 can be reduced.

Accordingly, the high-pressure fuel flowing through the cylinder accommodating chamber 50 is not suddenly throttled or released by the seat portion 63 of the retainer 60, and the same as in the first embodiment, Cylinder storage chamber 5
Cavitation hardly occurs on the inner surface of the zero.

FIG. 2B shows a third embodiment of the present invention.

In the third embodiment, the nozzle holder 7
The configuration of the first embodiment is different from that of the second embodiment, and the other configurations are the same as those of the second embodiment.

As shown in FIG. 2B, the nozzle holder 71 has a body main body 72 and an end piece 73 abutted on the body main body 72. A spring housing chamber 74 is formed inside the body main body 72. The spring housing chamber 74 is open toward the side opposite to the nozzle body 12, and the open end of the spring housing chamber 74 is closed by an end piece 73.

The body main body 72 includes a spring accommodating chamber 74.
And a bottom wall 75 as a partition interposed between the nozzle body 12 and the nozzle body 12. The thickness T4 of the bottom wall 75 is set larger than the axial length L1 of the journal 25 of the nozzle needle 24. The bottom wall 75 is abutted against the nozzle body 12 in a liquid-tight manner, and a through hole 62 is formed in the center of the bottom wall 75. The guide portion 64 of the retainer 60 and the journal portion 25 of the nozzle needle 24 are slidably fitted in the through hole 62 in the axial direction. Butted against each other inside.

According to such a configuration, the retainer 60
By fitting the guide portion 64 into the through hole 62 of the body main body 72, the posture in the spring accommodating chamber 74 is restrained, so that the fitting length necessary to support the retainer 60 can be sufficiently ensured. it can. For this reason, the attitude of the retainer 60 is stabilized, and even if the pressure applied to the retainer 60 is biased due to the inclination of the pressure spring 32, the swing vibration of the retainer 60 can be prevented.

It should be noted that the fuel injection nozzle according to the present invention is not specified for a diesel engine, but can be similarly applied to a gasoline engine.

[0079]

According to the present invention described in detail above, the guide portion, which is the largest outer diameter portion of the retainer, is slidably fitted directly into the spring accommodating chamber. As a result, the clearance between the inner surface of the spring accommodating chamber and the retainer can be significantly reduced as compared with the related art.

Therefore, even if the pressing force applied to the retainer due to the inclination of the spring is biased, the swinging vibration of the retainer can be prevented, and the amplitude of the retainer in the radial direction of the cylinder housing chamber can be reduced. Can be.
As a result, the high-pressure fuel flowing through the clearance is not sharply throttled or released by the retainer, and cavitation hardly occurs on the surface of the retainer or the inner surface of the cylinder housing chamber as compared with the related art.

Further, according to the present invention, since the retainer is restrained in the spring chamber by fitting the guide portion of the retainer into the through hole of the distance piece or the nozzle holder, the fitting required for supporting the retainer is achieved. The joint length can be sufficiently secured. For this reason, the posture of the retainer is stabilized, and even if the pressing force of the spring applied to the retainer is biased, the swinging vibration of the retainer can be prevented, and the amplitude of the retainer in the radial direction of the cylinder housing chamber can be reduced. It can be kept low. Therefore, the high-pressure fuel flowing through the cylinder storage chamber is not rapidly throttled or released by the retainer, and cavitation hardly occurs on the surface of the retainer or the inner surface of the cylinder storage chamber.

Thus, according to the present invention, the corrosion of the retainer and the spring accommodating chamber and the accompanying damage can be reliably prevented, and the reliability of the fuel injection nozzle can be improved.

[Brief description of the drawings]

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

FIG. 2A is a sectional view of a fuel injection nozzle according to a second embodiment of the present invention. (B) is a sectional view of a fuel injection nozzle according to a third embodiment of the present invention.

FIG. 3 is a cross-sectional view of a conventional fuel injection device.

FIG. 4A is a cross-sectional view of a conventional fuel injection nozzle showing a state in which a nozzle needle is open. (B) is a sectional view of the conventional fuel injection nozzle showing a state in which the nozzle needle is closed.

[Explanation of symbols]

 4 Fuel Injection Nozzle 10, 71 Nozzle Holder 12 Nozzle Body 19 Injection Hole 21 Fuel Supply Path 24 Nozzle Needle 32 Spring (Pressure Spring) 50, 74 Spring Reservoir 54, 60 Retainer 56, 64 ... Guide part 62 ... Through hole 75 ... Partition part (bottom wall) S1 ... Clearance

Claims (6)

[Claims] A nozzle body having an injection hole connected to a fuel supply passage through which pressurized fuel is supplied; a nozzle needle held reciprocally by the nozzle body and opening and closing the injection hole; and connected to the nozzle body. A nozzle holder having a spring housing chamber in which one end of the nozzle needle faces and excess fuel is returned through a clearance between the nozzle needle and the nozzle body; housed in the spring housing chamber of the nozzle holder;
A pressure spring for pressing the nozzle needle in the closing direction; interposed between one end of the nozzle needle and the pressure spring, for transmitting the pressing force of the pressure spring to the nozzle needle, and in the spring accommodating chamber. A retainer that reciprocates following the opening and closing operation of the nozzle needle, wherein the retainer has a guide portion that slidably fits in the spring housing chamber to restrain the attitude of the retainer. A fuel injection nozzle. 2. The fuel injection nozzle according to claim 1, wherein a clearance is formed between the guide portion of the retainer and an inner surface of the spring accommodating chamber to allow excess fuel to flow. . 3. The retainer according to claim 1, wherein the retainer has a projection coaxially projecting toward one end of the nozzle needle, and an end face of the projection abuts one end of the nozzle needle. A fuel injection nozzle. 4. The fuel injection nozzle according to claim 3, wherein an end face of the convex portion is spherically curved. 5. A nozzle body having an injection hole connected to a fuel supply passage to which pressurized fuel is supplied; a nozzle needle held reciprocally by the nozzle body to open and close the injection hole; and connected to the nozzle body. A nozzle holder having a spring accommodating chamber; surplus fuel interposed between the nozzle holder and the nozzle body, one end of the nozzle needle being inserted, and flowing into a clearance between the nozzle needle and the nozzle body. A distance piece having a through hole for guiding the nozzle needle to the spring accommodating chamber; a pressure spring accommodated in the spring accommodating chamber of the nozzle holder for pressing the nozzle needle in a closing direction; one end of the nozzle needle and the pressure spring Between the pressure spring A retainer that transmits reciprocating pressure to the nozzle needle and reciprocates following the opening and closing operation of the nozzle needle in the spring accommodating chamber. The retainer is slidable in the through hole of the distance piece. A fuel injection nozzle having a guide portion that fits into the retainer to restrain the attitude of the retainer. 6. A nozzle body having an injection hole connected to a fuel supply passage to which pressurized fuel is supplied; a nozzle needle held reciprocally by the nozzle body to open and close the injection hole; A partition portion interposed between the spring housing chamber and the nozzle body, one end of the nozzle needle is inserted into the partition portion, and excess fuel flowing into a clearance between the nozzle needle and the nozzle body; A nozzle holder having a through hole for guiding the nozzle holder to the spring housing chamber;
A pressure spring accommodated in a spring accommodating chamber of the nozzle holder, for pressing the nozzle needle in a closing direction; and a pressure spring interposed between one end of the nozzle needle and the pressure spring, for controlling the pressing force of the pressure spring. A retainer that transmits to the nozzle needle and reciprocates following the opening and closing operation of the nozzle needle in the spring accommodating chamber; the retainer is slidably fitted in the through hole of the partition portion. A fuel injection pump having a guide portion for restraining the attitude of the retainer.