JP2007100690A - Fuel injection nozzle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the complication of working of a first needle 6 without deteriorating the concentricity of the first and a second needles 5, 6 in a variable injection hole type fuel injection nozzle. <P>SOLUTION: Inner diameter dimension of the first needle and outer diameter dimension of the second needle 6 are provided in such a manner that the same gradually reduce, and clearance between the needles formed by putting an inner circumference surface of the first needle 5 and an outer circumference surface of the second needle 6 oppositely in a radial direction is formed in such a manner the clearance at a front end part and a rear end part is narrower than that at a center part. Consequently, both of prepared hole drilling and grinding of the first needle 5 can be performed from only the rear end side, and sliding contact part can be formed at the front end part and the rear end part while forming a space 32 between the inner circumference surface of the first needle 5 and the outer circumference surface of the second needle 6 at the center part. Consequently, the complication of working the first needle 5 can be reduced without deteriorating the concentricity of the first and the second needles 5, 6. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel injection nozzle that injects fuel into a combustion chamber of an engine.

[Conventional technology]
Conventionally, variable injection hole type fuel injection that can change the number of injection holes to be opened according to the injection amount in order to promote atomization in the low rotation range and high injection rate in the high rotation range. A nozzle is considered.

  A conventional variable injection hole type fuel injection nozzle 100 (hereinafter simply referred to as a nozzle 100) has first and second injection holes 101, 102 opened in two stages, for example, as shown in FIG. The body 103, the first and second nozzle holes 101, 102 are accommodated on the inner peripheral side of the first needle 104, the first needle 104 that opens and closes the first nozzle hole 101 that is opened first, The second needle 105 that opens and closes the second nozzle hole 102 that opens after the first nozzle hole 101 receives the pressure of the fuel in the control chamber 106 and contacts the first and second needles 104 and 105, A cylindrical first piston 107 that urges the second needles 104 and 105 in the valve closing direction is housed on the inner peripheral side of the first piston 107 and receives the fuel pressure in the control chamber 106 to receive the second needle 105. The second needle 10 Is constituted by a second piston 108 that urges the first piston 107 in the valve closing direction, a spring 109 that is held in the axial direction by the first piston 107 and the body 103, and urges the first piston 107 in the valve closing direction (for example, , See Patent Document 1).

  In the nozzle 100, high-pressure fuel is supplied to the tip of the first needle 104 through the high-pressure channel 115, the fuel reservoir 116 and the guide hole 117, and the control chamber 106 is supplied through the high-pressure channel 118 and the inlet orifice 119. High pressure fuel is supplied. Thereby, the fuel of the control chamber 106 and the spring 109 exert a biasing force in the valve closing direction at the rear end of the first needle 104, and the fuel supplied through the fuel reservoir 116 and the guide hole 117 is in the valve opening direction at the front end. Is exerting a biasing force. Further, on the rear end side of the second needle 105, the fuel in the control chamber 106 and the spring 109 exert a biasing force in the valve closing direction. For this reason, since the urging force acting in the valve closing direction is stronger than the urging force acting in the valve opening direction in both the first and second needles 104, 105, the first and second needles 104, 105 are seat surfaces. The first and second nozzle holes 101 and 102 are closed in contact with 120, respectively.

  Then, when an actuator (not shown) that opens and closes the low pressure flow path 125 is operated to open the low pressure flow path 125, the fuel in the control chamber 106 is discharged through the outlet orifice 127 and the low pressure flow path 125. Here, since the outlet orifice 127 is provided so that the fuel flow rate is larger than that of the inlet orifice 119, the fuel pressure in the control chamber 106 decreases. For this reason, in the first needle 104, the urging force acting in the valve closing direction is weaker than the urging force acting in the valve opening direction, so the first needle 104 rises away from the seat surface 120, and the first needle 104 rises. The nozzle hole 101 is opened. As a result, fuel is injected from the first nozzle hole 101, and high-pressure fuel is also supplied to the tip of the second needle 105 to exert a biasing force in the valve opening direction. Further, when the first needle 104 is raised, the first piston 107 is also raised, so that the first piston 107 is detached from the second needle 105. For this reason, the urging force by the spring 109 does not act on the second needle 105.

  Further, when the fuel is continuously discharged from the control chamber 106 and the fuel pressure in the control chamber 106 decreases, the biasing force acting in the valve closing direction is weaker than the biasing force acting in the valve opening direction even in the second needle 105. Therefore, the second needle 105 moves away from the seat surface 120 and opens the second injection hole 102. As a result, fuel is also injected from the second injection hole 102.

  Eventually, when the actuator stops operating and the low-pressure flow path 125 is closed, the fuel pressure in the control chamber 106 increases, and the first and second needles 104 and 105 are seated in the order of the second needle 105 and the first needle 104. The first and second nozzle holes 101 and 102 are in contact with the surface 120 and are closed in the order of the second nozzle hole 102 and the first nozzle hole 101.

  In the nozzle 100 having such a configuration, by changing the period during which the actuator is operated, only the first nozzle hole 101 is opened, or both the first and second nozzle holes 101 and 102 are opened. As a result, the number of nozzle holes to be opened can be changed as a result.

[Problems with conventional technology]
By the way, as shown in FIG. 5, the inner peripheral surface of the first needle 104 and the outer peripheral surface of the second needle 105 face each other to form a radial clearance (hereinafter, this clearance is referred to as an inter-needle clearance). Call). And in order to maintain the coaxiality of the 1st needle 104 and the 2nd needle 105, the clearance between needles is set up so that it may become small at a tip part and a back end part. That is, the first and second needles 104 and 105 are kept in coaxiality by being in sliding contact with each other at the front end portion and the rear end portion.

  However, in order to reduce the clearance between the needles at both the front end portion and the rear end portion and to bring the first and second needles 104 and 105 into sliding contact, the inner peripheral surface of the first needle 104 and the outer peripheral surface of the second needle 105 are In both cases, the intermediate portion needs to be processed into a concave shape. For this reason, the processing of the first and second needles 104 and 105 becomes complicated. In particular, since the processing of the first needle 104 is performed on the inner peripheral surface, special processing such as electric discharge processing and honing processing is required to simply form the concave shape, increasing complexity.

  Further, since the first and second needles 104 and 105 are brought into sliding contact with both the front end portion and the rear end portion, the inner peripheral surface of the first needle 104 and the outer peripheral surface of the second needle 105 are the front end portion and the rear end portion. Both of them need to be polished. For this reason, in the polishing process of the first needle 104, a polishing tool is inserted and processed from both the front end and the rear end, so that a slight axial deviation occurs between the front end and the rear end.

  The combination of the cylindrical outer needle (corresponding to the first needle 104 in FIGS. 4 and 5) and the inner needle (corresponding to the second needle 105 in FIGS. 4 and 5) accommodated in the inner periphery of the outer needle is: Various other forms are considered.

  For example, the outer and inner needles are slidably contacted at the rear end, and the nozzle hole provided in the body is opened and closed at the tip of the outer needle, and the nozzle hole provided in the outer needle is opened and closed at the tip of the inner needle. (For example, refer to Patent Document 2). However, in this embodiment, since the fuel passage is formed between the outer needle and the inner needle, it is necessary to process the inner peripheral surface of the outer needle into a concave shape, and the complexity of processing cannot be reduced. Further, since only the rear end portion forms a sliding contact portion, it is considered that the coaxiality of the outer and inner needles is inferior to that of the nozzle 100.

  In addition, an intermediate member (described as “divided sleeve”) is interposed between the outer needle and the inner needle at the front end, and the outer and inner needles are slidably contacted at the rear end ( For example, see Patent Document 3). According to this embodiment, the rib protruded to the inner peripheral side of the split sleeve is in contact with the inner needle, and the inner needle can be supported by both the front end portion and the rear end portion. The coaxiality can be improved. However, a new intermediate member is required, leading to an increase in the number of parts and an increase in cost.

  Further, it is considered that the outer and inner needles are slidably contacted at the rear end portion, and the nozzle hole provided in the body or the like is opened and closed at the distal end portion of the outer and inner needles (see, for example, Patent Document 4). However, even in this configuration, only the rear end portion forms a sliding contact portion, and therefore, it is considered that the coaxiality of the outer and inner needles is inferior to that of the nozzle 100.

Further, the outer and inner needles are slidably contacted at the rear end portion, and the nozzle hole provided in the body is opened and closed at the distal end portion of the outer and inner needles, and the intermediate portion between the rear end portion and the distal end portion is also outside, The thing which makes an inner needle slide-contact is considered (for example, refer patent document 5). However, according to this embodiment, since the inner peripheral portion of the outer needle is reduced at the intermediate portion, it is necessary to perform the prepared hole processing from both the front end and the rear end, and the processing becomes complicated. Furthermore, since the inner needle is supported by the rear end portion and the intermediate portion, it is considered that the coaxiality is inferior to the case where the inner needle is supported by the front end portion and the rear end portion as in the nozzle 100.
International Publication No. 03/069511 Pamphlet JP 59-147862 A JP-A-4-232375 JP 2004-183647 A JP-A-8-35467

  The present invention has been made to solve the above problems, and in a variable injection hole type fuel injection nozzle, the complexity of processing the outer needle is reduced without lowering the coaxiality of the outer and inner needles. There is to do.

[Means of Claim 1]
According to a first aspect of the present invention, there is provided a fuel injection nozzle including a body having a plurality of injection holes that are opened at least in two stages, front and rear, at a tip portion thereof, housed inside the body, A cylindrical first needle that opens and closes the first nozzle hole that is opened to the inside, and is accommodated on the inner peripheral side of the first needle, moves in the same direction as the first needle, and opens after the first nozzle hole. And a second needle for opening and closing the second nozzle hole. The inner diameter of the first needle and the outer diameter of the second needle are provided so as to change in one direction toward the tip.

  If the inner diameter of the first needle is provided so as to change in one direction toward the tip (that is, so as to gradually increase or decrease toward the tip), either the prepared hole processing or polishing processing of the first needle is performed. Also, it can be applied only from one direction of the front end and the rear end. Thereby, it is possible to prevent the occurrence of axial misalignment between the sliding contact portion at the front end portion and the sliding contact portion at the rear end portion, and it is possible to reduce the complexity of processing.

  For this reason, the complexity of processing the first needle can be reduced without lowering the coaxiality of the first and second needles. Needless to say, the first needle corresponds to the outer needle and the second needle corresponds to the inner needle.

[Means of claim 2]
According to the fuel injection nozzle of claim 2, the first needle has at least two annular portions in which a hollow cut surface perpendicular to the axial direction has a substantially constant shape in a constant section in the axial direction, which differs in the axial direction. The second needle has at least two columnar portions whose cut surfaces perpendicular to the axial direction have a substantially constant shape in a constant section in the axial direction. One columnar portion of the second needle is slidably supported by one annular portion of the first needle, and another columnar portion different from one columnar portion slides on another annular portion different from one annular portion. It is supported freely.

  Thereby, the second needle is slidably supported by the first needle at at least two different locations in the axial direction. For this reason, the coaxiality of the first needle and the second needle can be reliably maintained. According to the second aspect of the present invention, the portions other than the annular portion and the columnar portion in which the first and second needles are in sliding contact with each other indicate that the inner diameter dimension of the first needle and the outer diameter dimension of the second needle are No conditions other than “change in one direction toward” are not imposed. Therefore, the inner peripheral surface of the first needle at a portion other than the annular portion and the outer peripheral surface of the second needle at a portion other than the columnar portion may be provided in a tapered shape, for example.

[Means of claim 3]
According to the fuel injection nozzle of claim 3, the clearance (interneedle clearance) formed by radially opposing the inner peripheral surface of the first needle and the outer peripheral surface of the second needle is the tip and The rear end portion is formed to be narrower than the intermediate portion.
Thereby, a sliding contact portion can be formed at the front end portion and the rear end portion while forming a space between the inner peripheral surface of the first needle and the outer peripheral surface of the second needle in the intermediate portion. Therefore, the sliding contact portion can be formed at the front end portion and the rear end portion without performing special processing such as electric discharge processing or honing processing.

[Means of claim 4]
According to the fuel injection nozzle of the fourth aspect, the inner diameter dimension of the first needle and the outer diameter dimension of the second needle are provided so as to gradually decrease toward the tip.
If the inner diameter dimension of the first needle and the outer diameter dimension of the second needle are provided so as to gradually decrease toward the tip, the inner diameter portion that accommodates the second needle can be greatly opened on the opposite tip side in the first needle, Further, the inner diameter portion can be sequentially reduced in diameter from the opposite tip side to the tip side. For this reason, the internal diameter part of a 1st needle can be processed easily and accurately.

  Further, the amount of axial deflection generated when the second needle descends is a value obtained by adding the sliding gap between the first needle and the second needle to the sliding gap between the first needle and the body. It corresponds to. For this reason, the second needle having the inner / outer double needle structure has a larger shaft deflection than the single needle having the single needle structure. As a result, the radial deflection caused by the contact between the inner periphery of the first needle and the outer periphery of the second needle also increases.

  On the other hand, according to the means of claim 4, the center of gravity of the second needle is moved to the opposite tip side by gradually decreasing the outer diameter of the second needle toward the tip. For this reason, in the fuel injection nozzle having an inner and outer double needle structure with a large shaft deflection amount, it is possible to suppress the radial deflection weight generated between the first and second needles.

[Means of claim 5]
According to the fuel injection nozzle of the fifth aspect, the inner diameter dimension of the first needle and the outer diameter dimension of the second needle are provided so as to gradually increase toward the tip.
By providing the inner diameter dimension of the first needle and the outer diameter dimension of the second needle so as to gradually increase toward the tip, the inner diameter portion accommodating the second needle can be greatly opened on the tip side in the first needle, The inner diameter portion can be sequentially reduced in diameter from the tip side to the opposite tip side. For this reason, the internal diameter part of a 1st needle can be processed easily and accurately.

  The fuel injection nozzle of the best mode 1 includes a body having a plurality of injection holes opened at least in two stages, front and rear, at the tip, and is housed inside the body, and is first in the plurality of injection holes. A cylindrical first needle that opens and closes the first injection hole to be opened, and is accommodated on the inner peripheral side of the first needle, moves in the same direction as the first needle, and is opened after the first injection hole. And a second needle for opening and closing the second nozzle hole. The inner diameter of the first needle and the outer diameter of the second needle are provided so as to change in one direction toward the tip.

  Further, according to this fuel injection nozzle, the first needle has an annular portion in which a hollow cut surface perpendicular to the axial direction has a substantially constant shape in a constant section in the axial direction at at least two places different in the axial direction. The second needle has columnar portions having substantially constant shapes with a section perpendicular to the axial direction in a constant section in the axial direction, at least at two locations different in the axial direction. One columnar portion of the second needle is slidably supported by one annular portion of the first needle, and another columnar portion different from one columnar portion slides on another annular portion different from one annular portion. It is supported freely.

Further, according to the fuel injection nozzle, the clearance formed by the radially inner surface of the first needle and the outer peripheral surface of the second needle is the intermediate portion at the front end portion and the rear end portion. It is formed to be narrower than that.
According to this fuel injection nozzle, the inner diameter dimension of the first needle and the outer diameter dimension of the second needle are provided so as to gradually decrease toward the tip.

[Configuration of Example 1]
The configuration of the fuel injection nozzle 1 (hereinafter referred to as nozzle 1) of the first embodiment will be described with reference to FIGS. The nozzle 1 forms the tip of an injector that injects and supplies fuel to the combustion chamber of the engine, and receives fuel distribution from, for example, a common rail that accumulates fuel in a high pressure state. In addition, the nozzle 1 is a variable nozzle type that can change the number of nozzle holes to be opened according to the injection amount in order to promote atomization in the low rotation region and high injection rate in the high rotation region. It is.

  As shown in FIG. 1 (a), the nozzle 1 is housed in the body 4 having a plurality of nozzle holes 2 and 3 opened in two stages, front and rear, and inside the body 4. A cylindrical first needle 5 that opens and closes the first nozzle hole 2 that is first opened in the nozzle holes 2 and 3, and is accommodated on the inner peripheral side of the first needle 5, and the first needle 5 A second needle 6 that moves in the coaxial direction and opens and closes the second nozzle hole 3 that is opened after the first nozzle hole 2; a first spring 7 that biases the first needle 5 in the valve closing direction; And a second spring 8 for urging the two needles 6 in the valve closing direction.

  The body 4 houses the first and second needles 5 and 6, the first spring 7, and the like, and the fuel flow for guiding the high-pressure fuel supplied from the high-pressure channel 11 to the first and second injection holes 2 and 3. A path 12 is formed. And the front end side of the fuel flow path 12 is formed in a tapered shape to form a seat surface 13 on which the first and second needles 5 and 6 are seated, and the first and second injection holes 2, 3 opens.

  The body 4 forms a control chamber 15 together with a cylinder member 14 to be described later at the rear end portion, and accommodates the second spring 8. The fuel in the control chamber 15 exerts pressure on the first and second needles 5 and 6 in the valve closing direction. That is, the fuel in the control chamber 15 urges the first and second needles 5 and 6 together with the first and second springs 7 and 8 in the valve closing direction. The control chamber 15 communicates with a supply / discharge chamber 16 through which high-pressure fuel is supplied / discharged, and the fuel pressure in the control chamber 15 increases / decreases as fuel is supplied / discharged in the supply / discharge chamber 16. The fuel supply / discharge in the supply / discharge chamber 16 is performed by an actuator such as a solenoid valve (not shown).

  As shown in FIG. 2, the first needle 5 has sheet portions 19 and 20 that repeat separation and attachment with the sheet surface 13 at the tip. The first nozzle holes 2 are closed when the seat portions 19 and 20 are seated on the seat surface 13, and the first nozzle holes 2 are opened when the seat portions 19 and 20 are separated from the seat surface 13.

  The first needle 5 is slidably supported by the body 4 at the rear end portion and the intermediate portion. That is, the rear end portion of the first needle 5 is formed in a cylindrical shape and is slidably contacted with the inner periphery of the cylinder member 14, and the intermediate portion is provided at three locations between the body 4 as shown in FIG. The fuel flow path 12 is formed and slidably contacts the body 4. Further, the first needle 5 seals the control chamber 15 from the front end side by slidingly contacting the cylinder member 14.

  The 2nd needle 6 has the sheet | seat part 21 which repeats attachment / detachment between the sheet | seat surfaces 13 in the front-end | tip. The second nozzle hole 3 is closed when the seat portion 21 is seated on the seat surface 13, and the second nozzle hole 3 is opened when the seat portion 21 is separated from the seat surface 13. Further, the second needle 6 has a collar portion 23 that moves inside the control chamber 15 at the rear end. Since the flange 23 is provided with a smaller diameter than the inner periphery of the cylinder member 14, the fuel in the control chamber 15 freely flows between the outer periphery of the flange 23 and the inner periphery of the cylinder member 14. Therefore, substantially the same pressure is exerted on the rear ends of the first and second needles 5 and 6 by the fuel in the control chamber 15.

The first spring 7 is held in the axial direction by the cylinder member 14 and the support member 25 disposed at the rear of the intermediate portion, and urges the cylinder member 14 toward the rear end side so as to be in pressure contact with the body 4. The needle 5 is urged toward the tip side (that is, in the valve closing direction).
The second spring 8 is held in the control chamber 15 in the axial direction by the flange 23 and the body 4 and biases the second needle 6 in the valve closing direction.

Next, the operation of the nozzle 1 will be described.
First, the fuel in the control chamber 15 exerts pressure on the first needle 5 in the valve closing direction, and the first spring 7 biases the first needle 5 in the valve closing direction. Further, the fuel supplied to the tip of the first needle 5 through the high-pressure channel 11 and the fuel channel 12 exerts pressure on the first needle 5 in the valve opening direction. Further, the fuel in the control chamber 15 exerts pressure on the second needle 6 in the valve closing direction, and the second spring 8 biases the second needle 6 in the valve closing direction.

  When the fuel discharge in the supply / exhaust chamber 16 starts, the pressure of the fuel in the control chamber 15 decreases. Therefore, the urging force acting in the valve closing direction in the first needle 5 (the urging force by the fuel in the control chamber 15 + The biasing force by the first spring 7) is weaker than the biasing force acting in the valve opening direction (the biasing force by the fuel at the tip of the first needle 5). Accordingly, the seat portions 19 and 20 are separated from the seat surface 13 to open the first injection hole 2, and fuel is also supplied to the tip of the second needle 6. For this reason, fuel is injected from the first injection hole 2, and the fuel supplied to the tip of the second needle 6 exerts pressure on the second needle 6 in the valve opening direction.

  When the fuel pressure in the control chamber 15 further decreases, the urging force acting in the valve closing direction (the urging force due to the fuel in the control chamber 15 + the urging force due to the second spring 8) also opens in the second needle 6. It becomes weaker than the urging force acting in the direction (the urging force by the fuel at the tip of the second needle 6). Thereby, the seat part 21 is separated from the seat surface 13 and the second injection hole 3 is opened. For this reason, fuel is also injected from the second injection hole 3.

  Eventually, when the fuel discharge in the supply / discharge chamber 16 ends, the fuel pressure in the control chamber 15 rises. Therefore, first, in the second needle 6, the biasing force acting in the valve closing direction acts in the valve opening direction. Be stronger than power. Thus, the seat portion 21 is seated on the seat surface 13, the second injection hole 3 is closed, and fuel injection from the second injection hole 3 is completed. When the fuel pressure in the control chamber 15 further increases, the urging force acting in the valve closing direction also becomes stronger in the first needle 5 than the urging force acting in the valve opening direction. As a result, the seat portions 19 and 20 are seated on the seat surface 13, the first injection hole 2 is closed, and the fuel injection from the first injection hole 2 is also terminated.

  Then, by changing the period during which fuel is discharged in the supply / discharge chamber 16, that is, the period during which the actuator is operated, only the first nozzle hole 2 is opened, or both the first and second nozzle holes 2, 3 are opened. As a result, the number of nozzle holes to be opened can be changed according to the injection amount.

[Features of Example 1]
The characteristics of the nozzle 1 of the first embodiment will be described with reference to FIG. In the nozzle 1, the inner diameter of the first needle 5 and the outer diameter of the portion of the second needle 6 on the tip side of the collar 23 are provided so as to gradually decrease toward the tip. And the outer peripheral surface of the second needle 6 are opposed to each other in the radial direction (interneedle clearance) so that the front end portion and the rear end portion are narrower than the intermediate portion. Specifically, in the portion where the first needle 5 and the second needle 6 are opposed to each other in the radial direction, the inner diameter dimension of the first needle 5 and the outer diameter dimension of the second needle 6 are in three steps toward the tip. It is provided to reduce the diameter.

  Here, the tip end portion of the first needle 5 having the smallest inner diameter dimension and the rear end portion of the first needle 5 having the largest inner diameter dimension are each subjected to polishing processing on the inner peripheral surface, and the second needle 6. The first front end and the first rear end guide portions 27 and 28 slidably contact with each other. Similarly, the front end portion of the second needle 6 having the smallest outer diameter size and the rear end portion of the second needle 6 having the largest outer diameter size are each subjected to polishing processing on the outer peripheral surface, and the first tip end. The guide part 27, the 2nd front-end | tip guide part 29 and the 2nd rear-end guide part 30 which are in sliding contact with the 1st rear-end guide part 28 are made.

  Thus, the 1st needle 5 has the annular part in which the hollow cut surface perpendicular | vertical to an axial direction exhibits a substantially constant shape in the fixed area of an axial direction in three places which differ in an axial direction. In addition, the second needle has columnar portions whose cut surfaces perpendicular to the axial direction have a substantially constant shape in a constant section in the axial direction at three different locations in the axial direction. The most advanced columnar portion is slidably supported by the most advanced annular portion, and the rearmost columnar portion is slidably supported by the last annular portion.

  That is, the most advanced annular portion forms the first tip guide portion 27, the rearmost annular portion forms the first rear end guide portion 28, and the most advanced columnar portion forms the second tip guide portion 29. The columnar part at the end forms the second rear end guide part 30.

  That is, the first needle 5 and the second needle 6 are in sliding contact with the first tip guide portion 27 and the second tip guide portion 29 at the tip portion, and with the first rear end guide portion 28 and the second rear tip portion at the rear end portion. The end guide portion 30 is in sliding contact. The first needle 5 and the second needle 6 are in sliding contact with the front end portion and the rear end portion, so that the clearance between the needles is narrower at the front end portion and the rear end portion than the intermediate portion.

  As a result, a sliding contact portion is formed at the front end portion and the rear end portion of the first and second needles 5 and 6, and the inner peripheral surface of the first needle 5 and the outer peripheral surface of the second needle 6 are formed at the intermediate portion. A space 32 is formed between them. Then, the control chamber 15 and the space 32 are interrupted by the sliding contact portion of the rear end portion, and the second needle 6 is slidably supported by the front end portion and the rear end portion. 1. The coaxiality of the second needles 5 and 6 is maintained.

[Effect of Example 1]
According to the nozzle 1 of the first embodiment, the inner diameter of the first needle 5 and the outer diameter of the second needle 6 are provided so as to gradually decrease toward the tip.
Thereby, both processing of the pilot hole processing of the 1st needle 5 and grinding | polishing processing can be performed only from a rear end. As a result, it is possible to prevent the first front end guide portion 27 and the first rear end guide portion 28 from being misaligned and to reduce the complexity of processing. For this reason, the complexity of processing the first needle 5 can be reduced without lowering the coaxiality of the first and second needles 5 and 6.

Further, the second front end guide portion 29 is slidably supported by the first front end guide portion 27 and the second rear end guide portion 30 is slidably supported by the first rear end guide portion 28. The two needles 6 are slidably supported by the first needle 5.
Thereby, the 2nd needle 6 is slidably supported by the 1st needle 5 in two places which differ in an axial direction. For this reason, the coaxiality of the 1st needle 5 and the 2nd needle 6 can be maintained reliably.

The inner diameter dimension of the first needle 5 and the outer diameter dimension of the second needle 6 are provided so as to gradually decrease toward the tip.
When the inner diameter dimension of the first needle 5 and the outer diameter dimension of the second needle 6 are provided so as to gradually decrease toward the tip, a space on the inner peripheral side of the first needle 5 that accommodates the second needle 6 (referred to as an inner diameter portion). Can be greatly opened on the opposite end side. Further, the inner diameter portion can be sequentially reduced in diameter from the opposite tip side to the tip side. For this reason, the internal diameter part of the 1st needle 5 can be processed easily and accurately.

  Further, the amount of axial runout in the radial direction that occurs when the second needle 6 descends is caused by the sliding gap between the first needle 5 and the second needle 6 in the sliding gap between the first needle 5 and the body 4. This corresponds to a value obtained by adding the moving gap (that is, the inter-needle clearance between the first rear end guide portion 28 and the second rear end guide portion 30). For this reason, the second needle 6 having an inner / outer double needle structure has a larger shaft deflection than a single needle having a single needle structure. As a result, the radial load caused by the contact between the inner periphery of the first needle 5 and the outer periphery of the second needle 6 also increases.

  On the other hand, in the nozzle 1, the center of gravity of the second needle 6 is moved to the opposite tip side by gradually decreasing the outer diameter of the second needle 6 toward the tip. For this reason, in the nozzle 1 having an inner / outer double needle structure with a large shaft deflection, it is possible to suppress the radial weighting generated between the first and second needles 5 and 6.

Further, the clearance between the needles is formed such that the front end portion and the rear end portion are narrower than the intermediate portion.
Thereby, a sliding contact portion can be formed at the front end portion and the rear end portion while forming the space 32 between the inner peripheral surface of the first needle 5 and the outer peripheral surface of the second needle 6 at the intermediate portion. Therefore, the sliding contact portion can be formed at the front end portion and the rear end portion without performing special processing such as electric discharge processing or honing processing.

[Modification]
In the nozzle 1 of the present embodiment, the inner diameter dimension of the first needle 5 and the outer diameter dimension of the second needle 6 are provided so as to gradually decrease toward the tip, but gradually increase toward the tip as shown in FIG. May be provided.

  Further, in the nozzle 1 of the present embodiment, an annular portion and a columnar portion are also provided at an intermediate portion between the front end portion and the rear end portion where the first needle 5 and the second needle 6 are in sliding contact with each other. The space 32 is formed by the peripheral surface and the outer peripheral surface of the columnar part facing each other, but the present invention is not limited to such a form. For example, either the inner peripheral surface of the first needle 5 forming the space 32 or the outer peripheral surface of the second needle 6 may be provided in a tapered shape, and the inner periphery of the first needle 5 forming the space 32 may be provided. Both the surface and the outer peripheral surface of the second needle 6 may be provided in a tapered shape.

(A) is a block diagram of a fuel injection nozzle, (b) is AA sectional drawing of (a) (Example). It is explanatory drawing which shows the principal part of a fuel-injection nozzle (Example). It is explanatory drawing which shows the principal part of a fuel-injection nozzle (modification example). It is a block diagram of a fuel injection nozzle (conventional example). It is explanatory drawing which shows the principal part of a fuel-injection nozzle (conventional example).

Explanation of symbols

1 Nozzle (fuel injection nozzle)
2 injection hole, 1st injection hole 3 injection hole, 2nd injection hole 4 body 5 1st needle 6 2nd needle 27 1st tip guide part (annular part)
28 1st rear end guide part (annular part)
29 Second tip guide part (columnar part)
30 Second rear end guide portion (columnar portion)

Claims (5)

A body having a plurality of nozzle holes opened at least in two stages, front and rear, at the tip,
A cylindrical first needle that is accommodated inside the body and opens and closes the first nozzle hole that is first opened in the plurality of nozzle holes;
The second needle is accommodated on the inner peripheral side of the first needle, moves in the same direction as the first needle, and opens and closes the second injection hole opened after the first injection hole. In the fuel injection nozzle,
An inner diameter dimension of the first needle and an outer diameter dimension of the second needle are provided so as to change in one direction toward the tip. The fuel injection nozzle according to claim 1,
The first needle has an annular portion in which a hollow cut surface perpendicular to the axial direction has a substantially constant shape in a constant section in the axial direction at at least two different locations in the axial direction,
The second needle has columnar portions whose cutting planes perpendicular to the axial direction have a substantially constant shape in a constant section in the axial direction at at least two different locations in the axial direction,
One columnar portion of the second needle is slidably supported by one annular portion of the first needle, and another columnar portion different from the one columnar portion is different from the one annular portion. A fuel injection nozzle that is slidably supported by the portion. The fuel injection nozzle according to claim 1 and claim 2,
The clearance formed when the inner peripheral surface of the first needle and the outer peripheral surface of the second needle face each other in the radial direction is formed so that the front end portion and the rear end portion are narrower than the intermediate portion. A fuel injection nozzle. The fuel injection nozzle according to any one of claims 1 to 3,
The fuel injection nozzle according to claim 1, wherein an inner diameter dimension of the first needle and an outer diameter dimension of the second needle are provided so as to gradually decrease toward the tip. The fuel injection nozzle according to any one of claims 1 to 3,
The fuel injection nozzle according to claim 1, wherein an inner diameter dimension of the first needle and an outer diameter dimension of the second needle are provided so as to gradually increase toward the tip.

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