JP2008031909A - Fuel injection nozzle and fuel injection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection nozzle resistant to damage to an injection hole while reducing a pressure loss accompanying fuel injection, and a fuel injection device equipped with the fuel injection nozzle. <P>SOLUTION: A fuel injection nozzle 100 is made of ceramic and provided with an injection hole 101. The injection hole 101 has a small diameter part 104 in itself where the hole diameter is smaller than hole diameters of both ends (an outside opening end 102 and inside opening end 103e). The small diameter part 104 has a corner part 104c protruded to the center shaft BX side of the injection hole 101. An angle α formed by the corner part 104c of the small diameter part 104 is an obtuse angle in the longitudinal section of the injection hole 101. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel injection nozzle having an injection hole for injecting fuel, and a fuel injection device including such a fuel injection nozzle, and more particularly, to a fuel injection nozzle made of ceramic and such a fuel injection nozzle. The present invention relates to a fuel injection device.

  Conventionally, a fuel injection nozzle made of ceramic and having an injection hole for injecting fuel is known. As the shape of the injection hole, a straight shape in which the hole diameter is constant from one opening end to the other opening end is common. However, such a straight injection hole has a long narrow passage, and therefore the pressure loss associated with fuel injection increases. In order to solve such a problem, Patent Document 1 and Patent Document 2 improve the shape of the injection hole. Specifically, the shape of the injection hole is a shape in which the hole diameter decreases toward the tip side of the nozzle. By adopting such a shape, it is possible to widen the flow path while reducing the opening on the nozzle tip side. Therefore, the pressure loss related to fuel injection can be reduced.

Japanese Patent No. 3114334 Japanese Patent No. 3118878

  However, when the hole diameter of the opening on the nozzle tip side is reduced as in Patent Documents 1 and 2, the angle formed by the corner becomes an acute angle. For this reason, when fuel is injected at a high pressure during use, a large stress is applied around sharp corners, and there is a risk that the injection hole may be damaged, such as a lack of an opening.

  The present invention has been made in view of the present situation, and is capable of reducing pressure loss related to fuel injection and is highly reliable in that the injection hole is not easily damaged, and such fuel injection nozzle. It aims at providing a fuel-injection apparatus provided with.

  The solution is a fuel injection nozzle made of ceramic and provided with an injection hole, wherein the injection hole has a small-diameter portion having a hole diameter smaller than the hole diameters at both ends, and the injection hole includes: In the longitudinal cross section of the injection hole, the narrow diameter portion has one or a plurality of corners protruding toward the central axis of the spray hole, and the angles formed by the corners of the narrow diameter portion are all obtuse angles. This is a fuel injection nozzle.

  According to the present invention, the injection hole has a small-diameter portion having a corner portion protruding toward the central axis side in the hole itself. Such an injection hole can make the flow path on both ends wider than that while narrowing the narrow diameter portion. Therefore, the pressure loss related to fuel injection can be reduced. In addition, since the fuel injection nozzle is made of ceramic, the strength of the injection hole is high. In addition, since the small-diameter portion of the injection hole has an obtuse angle when viewed from the longitudinal section of the injection hole, the corner portion is strong even when high stress is applied to the corner during use. Therefore, it is difficult to break the injection hole as compared with the injection hole according to the above-described prior art (an injection hole having a corner formed by an acute angle). Therefore, it is possible to reduce the pressure loss related to fuel injection, and it is possible to provide a highly reliable fuel injection nozzle that is less likely to be damaged in the injection hole.

In addition, the “fuel injection nozzle” in the present invention only needs to satisfy the above requirements, and the shape and the like can be changed as appropriate.
The “injection holes” only need to satisfy the above requirements, and the number and formation position thereof may be appropriately changed in consideration of the spray amount, the spray direction, and the like.
Moreover, the hole diameter of both ends and the hole diameter of the small diameter part can be appropriately changed in consideration of the spray amount, the size of the droplets formed by spraying, and the like. It should be noted that the hole diameters at both ends may be different sizes at one end and the other end. In that case, the narrow-diameter portion is a portion having a smaller hole diameter than either end. In addition, the angle formed by the corners of the small diameter portion can be changed as appropriate within the range of an obtuse angle in consideration of droplet refinement during spraying, strength against spray pressure, and the like.

  Furthermore, the fuel injection nozzle may be a fuel injection nozzle having a minimum hole diameter of 100 μm or less.

When the fuel injection nozzle is made of metal, it is difficult to set the hole diameter to 100 μm or less when forming the injection hole by a technique such as laser processing, electric discharge processing, or LIGA process.
On the other hand, in the present invention, the fuel injection nozzle is made of ceramic. Since ceramic shrinks when fired, the diameter of the fired injection holes is smaller than that of the through holes formed when fired. Therefore, since it is sufficient to drill a relatively large through hole when not fired, an injection hole having a hole diameter of 100 μm or less can be formed. And if the injection hole with such a small hole diameter is formed in this way, it is possible to make the droplets finer during spraying, so that PM discharge can be greatly reduced.

  Another solution is a fuel injection device including any one of the fuel injection nozzles described above.

  Such a fuel injection device includes the above-described fuel injection nozzle that can reduce the pressure loss associated with fuel injection and that has high reliability and the like such that the injection hole is less likely to be damaged. The pressure loss can be reduced, and the operation and effect can be achieved such that the injection hole is hardly damaged and the reliability can be increased.

(Embodiment 1)
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view of a fuel injection device 110 according to the first embodiment. 2 shows a longitudinal sectional view of the fuel injection nozzle 100 according to the first embodiment, and FIG. 3 shows a partially enlarged sectional view of the vicinity of the injection hole 101 among them. In FIG. 1, the lower side is the distal end side, and the upper side is the proximal side, while FIGS. 2 and 3 are the distal side and the lower side is the proximal side.

  The fuel injection device 110 is a device for injecting high-pressure fuel into a combustion chamber of an internal combustion engine (not shown). This fuel injection device 110 has a laminated piezoelectric element (molded unit laminated body) 111 inside, and is driven by this. The molded unit laminated body 111 includes three laminated piezoelectric units 113, 113, 113 and spacers 115, 115 arranged around the boundary between adjacent laminated piezoelectric units 113, 113, 113.

  The fuel injection device 110 includes a cylindrical main body member 120 that extends along the axis AX. The main body member 120 holds the nozzle member 130 at the nozzle holding portion 120n located on the tip side (downward in FIG. 1). In addition, the molded unit laminate 111 is inserted and held in the cylindrical piezoelectric element surrounding portion 120p of the main body member 120. More specifically, in the piezoelectric element surrounding portion 120p, the tip portion (downward in FIG. 1) has a piston 141 including a large diameter base portion 141b and a small diameter rod portion 141r, and a rod portion 141r. A cylinder spring 120c is formed on the tip side (downward in FIG. 1) of the base portion 141b.

  The front end surface 111t1 of the molded unit laminate 111 is in contact with the piston 141. On the other hand, the base end surface 111t2 of the molded unit laminate 111 is in contact with a sealing plate 145 welded and fixed to the base end portion (upward in FIG. 1) of the piezoelectric element surrounding portion 120p. For this reason, the molded unit laminated body 111 is always urged by the elastic force of the disc spring 143 so that a compressive stress is applied. Further, a seal groove 141m is recessed around the base portion 141b of the piston 141, and an O-ring 147 is fitted therein to seal the cylinder chamber 120c.

  The nozzle member 130 includes a fuel injection nozzle 100 that forms a distal end portion, and a nozzle base end member 131 that is located on the base end side thereof. The fuel injection nozzle 100 is made of ceramic (specifically alumina). The fuel injection nozzle 100 has a hemispherical outer surface 100a and a hemispherical inner surface 100b, and has a dome shape with a thickness of 1 mm (see also FIGS. 2 and 3).

  The fuel injection nozzle 100 is provided with a plurality of injection holes 101, 101,... Penetrating between the outer surface 100a and the inner surface 100b. 2 and 3 are longitudinal sectional views of the injection hole 101. FIG. Each injection hole 101 has an outer opening end 102 located at the end on the outer surface 100a side, an inner straight portion 103 including an inner opening end 103e located on the inner surface 100b side, an outer opening end 102 and an inner straight portion 103. And a small-diameter portion 104 having a smaller hole diameter than these.

The outer opening end 102 has a hole diameter of 100 μm.
The inner opening 103 including the inner opening 103e has a straight shape (cylindrical shape) having a uniform hole diameter of 100 μm and a length (length in the central axis BX direction) of 900 μm.
The narrow diameter portion 104 has an outer tapered portion 104f that gradually decreases in hole diameter from the outer opening end 102 toward the inner surface 100b, and an inner tapered portion 104g that gradually decreases in hole diameter from the inner opening 103 toward the outer surface 100a. In these boundary portions (in the center of the center in the direction of the central axis BX), the shape having the smallest hole diameter is formed. The hole diameter (minimum hole diameter) of the central portion having the smallest hole diameter among the thin diameter portions 104, that is, the corner portion 104c described below is 100 μm or less (75 μm in this example). The small-diameter portion 104 has one corner 104c that protrudes toward the central axis BX at the center of the small-diameter portion 104 in the central axis BX direction. The corner portion 104c has an obtuse angle (150 degrees in this example) in the longitudinal section of the injection hole 101.

  As described above, the injection hole 101 according to the first embodiment includes the small-diameter portion 104 having a corner portion 104c that protrudes toward the central axis BX. The injection hole 101 narrows the narrow-diameter portion 104. Specifically, the small-diameter portion 104 has a small diameter in the corner portion 104c while narrowing the flow path on both ends (the outer surface 100a side and the inner surface 100b side). It is wider than the part 104. Therefore, the pressure loss related to fuel injection can be reduced. In addition, since the fuel injection nozzle 100 is made of ceramic, the strength of the injection hole 101 is high. Moreover, since the angle α formed by the corner portion 104c of the small-diameter portion 104 of the injection hole 101 is an obtuse angle, even when a high stress is applied to the corner portion 104c during use, the corner portion 104c is strong and difficult to break. The injection hole 101 is not easily damaged. Therefore, the pressure loss related to fuel injection can be reduced, and the fuel injection nozzle 100 can be made highly reliable with less damage to the injection hole 101.

  Further, as will be described later, since ceramic shrinks during firing, the diameter of the fired injection hole 101 is smaller than that of the through-hole formed when unfired. Therefore, since it is sufficient to drill a relatively large through hole when not fired, the injection hole 101 having a hole diameter of 100 μm or less can also be formed. And if the injection hole 101 with such a small hole diameter is formed in this way, it is possible to achieve finer droplets during spraying, so that PM discharge can be greatly reduced.

  Returning to FIG. 1, a needle 149 is slidably accommodated inside the nozzle member 130. The injection holes 101, 101,... Of the fuel injection nozzle 110 can be opened and closed by the tip 149s of the needle 149. In addition, an annular chamber 130p is formed at the base end portion of the nozzle member 130 (upward in FIG. 1). In the annular chamber 130p, the piston portion 149p of the needle 149 is disposed with an orifice 151 formed between the periphery thereof and the wall surface of the annular chamber 130p. A spring holding hole 149 pn is formed in the piston portion 149 p of the needle 149. A coil spring 153 is inserted and held in the spring holding hole 149pn, and is in contact with a partition wall portion 120w that partitions the nozzle holding portion 120n of the main body member 120 and the piezoelectric element surrounding portion 120p. It is energized (downward in FIG. 1).

  The main body member 120 and the nozzle member 130 are formed with fuel supply ports 120f and 130f that connect the outside and the annular chamber 130p, and fuel pressurized to a high pressure through the fuel supply ports 120f and 130f, It is supplied to the annular chamber 130p. Furthermore, a communication hole 120 t that connects the spring holding hole 149 pn and the piezoelectric element surrounding portion 120 p is formed in the partition wall portion 120 w of the main body member 120. Accordingly, the fuel supplied to the annular chamber 130p is also filled into the spring holding hole 149pn, the communication hole 120t, and the cylinder chamber 120c of the piezoelectric element surrounding portion 120p through the orifice 151.

  The plurality of external lead wires 117 of the molded unit laminate 111 are taken out through the lead insertion holes 120 m of the main body member 120. When a voltage is applied to these external lead wires 117, the molded unit laminate 111 extends in the direction of the axis AX, and the pressure in the cylinder chamber 120c increases. Then, the needle 149 moves to the tip side and closes (the injection holes 101, 101,... Are closed). On the other hand, when the applied voltage of the molded unit stacked body 111 is decreased and contracted, the pressure in the cylinder chamber 120c decreases, and the piston portion 149p of the needle 149 is moved by the pressure of the fuel supplied from the fuel supply ports 120f and 130f. It moves while compressing the coil spring 153 toward the base end side. Then, the valve is opened and fuel is injected from the injection holes 101, 101,.

Next, a method for manufacturing the fuel injection nozzle 100 according to the first embodiment will be described.
First, a slurry made of an unfired ceramic is prepared by a known method.
Next, as shown in FIGS. 4 and 5, a forming jig GG having an upper die UG and a lower die SG is prepared. The upper mold UG is formed with a hemispherical recess UGK for forming an unfired body 210 described later. The upper mold UG is formed with an inlet UGT for injecting the slurry SR into the recess UGK from the upper side to the lower side. On the other hand, the tip portion SGB of the lower mold SG is formed in a hemispherical shape corresponding to the concave portion UGK. Thereby, a cavity KB having a shape corresponding to an unfired body 210 described later is formed between the recess UGK of the upper mold UG and the tip SGB of the lower mold SG. Further, a discharge path HST for discharging the injected excess slurry SR from the cavity KB to the outside is formed between the upper mold UG and the lower mold SG.

  Further, the forming jig GG includes a plurality of upper pins PG1 and lower pins PG2 for forming through holes 211, 211,... Corresponding to injection holes 101, 101,. Prepare. The upper pin PG1 and the lower pin PG2 are arranged so as to be able to advance and retreat in their own axial directions. Each upper pin PG1 has a columnar part PG1D having a columnar shape and a truncated cone part PG1E having a truncated cone shape located at the tip thereof. Similarly, the lower pin PG2 also has a columnar part PG2D that forms a columnar shape, and a truncated cone part PG2E that is located at the tip of the columnar part PG2E and forms a truncated cone shape. At the time of molding the unfired body 210 described later, only the truncated cone part PG1E of the upper pin PG1 protrudes into the cavity KB, and the truncated pin part PG2E of the lower pin PG2 and a part of the tip side of the cylindrical part PG2D Project into the cavity KB. At this time, the upper pin PG1 and the lower pin PG2 are brought into contact with each other at the tips.

  Using such a forming jig GG, an unfired body 210 having a form corresponding to the fuel injection nozzle 100 is formed. Specifically, the unfired ceramic slurry SR is injected from the injection port UGT of the forming jig GG as indicated by an arrow in FIG. Then, the slurry SR is filled in the cavity KB. Excess slurry SR is discharged to the outside through the discharge path HST as indicated by an arrow in FIG. Then, after passing through a drying process or the like, the upper pin PG1 and the lower pin PG2 are retracted. As a result, as shown in FIG. 6, an unfired body 210 having a dome shape having a hemispherical outer surface 210 a and a hemispherical inner surface 210 b and having a through hole 211 corresponding to the injection hole 101 is obtained.

Next, the green body 210 is fired by a known method. Thereby, the injection hole 101 is formed from the through-hole 211, and the fuel injection nozzle 100 shown in FIG.2 and FIG.3 is completed.
The fuel injection device 110 can be formed by a known method using the fuel injection nozzle 110.

(Embodiment 2)
Next, a second embodiment will be described. Note that the description of the same parts as those in the first embodiment is omitted or simplified. The fuel injection device 310 of the second embodiment is the same as the fuel injection device 100 of the first embodiment except for the fuel injection nozzle 300 (see FIG. 1). In the second embodiment, the shape of the injection hole 301 of the fuel injection nozzle 300 is different from the shape of the injection hole 101 of the fuel injection nozzle 100 of the first embodiment. FIG. 7 shows a partially enlarged sectional view of the vicinity of the injection hole 301 according to the second embodiment. FIG. 7 is a drawing corresponding to FIG. 3 of the first embodiment, and shows a longitudinal sectional view of the injection hole 301.

  The fuel injection nozzle 300 according to the second embodiment also has a dome shape having a semispherical outer surface 300a and a semispherical inner surface 300b, and a plurality of injection holes 301, 301,. In the second embodiment, each injection hole 301 has an outer opening end 302 positioned at the end on the outer surface 300a side, an inner opening end 303 positioned at an end on the inner surface 300b side, an outer opening end 302, and an inner opening end 303. And a small diameter part 304 having a smaller hole diameter than these.

Both the outer opening end 302 and the inner opening end 303 have a hole diameter of 100 μm.
The small-diameter portion 304 includes an outer tapered portion 304f that gradually decreases in hole diameter from the outer opening end 302 toward the inner surface 300b, and an inner tapered portion 304g that decreases in diameter gradually from the inner opening end 303 toward the outer surface 300a. And a straight portion 304h which forms a central portion of itself in the direction of the central axis BX and has a constant hole diameter.

  The hole diameter (minimum hole diameter) of the straight part 304h having the smallest hole diameter among the small diameter parts 304 is 100 μm or less (75 μm in this example). The small diameter portion 304 has two corner portions (an outer corner portion 304c1 and an inner corner portion 304c2) that protrude toward the central axis BX at both ends of the straight portion 304h. The outer corner portion 304c1 has an obtuse angle (150 degrees in this example) in the longitudinal section of the injection hole 301. Similarly, in the inner corner portion 304c2, the angle β formed in the longitudinal section of the injection hole 301 is an obtuse angle (in this example, 150 degrees as with the angle α).

As described above, the injection hole 301 according to the second embodiment includes the small-diameter portion 304 having two corner portions (the outer corner portion 304c1 and the inner corner portion 304c2) that protrude toward the central axis BX. The injection hole 301 narrows the narrow diameter portion 304. Specifically, the diameter of the flow path on both ends (the outer surface 300a side and the inner surface 300b side) is narrow while the hole diameter of the straight portion 304h of the small diameter portion 304 is reduced. It is wider than the part 304. Therefore, the pressure loss related to fuel injection can be reduced. In addition, since the fuel injection nozzle 300 is also made of ceramic, the strength of the injection hole 301 is high. In addition, since the small diameter portion 304 of the injection hole 301 has the obtuse angles α and β formed by the outer corner portion 304c1 and the inner corner portion 304c2, high stress is exerted on the outer corner portion 304c1 and the inner corner portion 304c2 during use. Even if it is applied, the outer corner portion 304c1 and the inner corner portion 304c2 are strong and hardly damaged, and the injection hole 301 is hardly damaged. Therefore, the pressure loss associated with fuel injection can be reduced, and the fuel injection nozzle 300 can be made highly reliable with less damage to the injection holes 301.
In addition, the same parts as those of the first embodiment have the same operations and effects as those of the first embodiment.

(Embodiment 3)
Next, a third embodiment will be described. Note that description of the same parts as those in the first or second embodiment is omitted or simplified. The fuel injection device 410 of the third embodiment is the same as the fuel injection devices 100 and 300 of the first and second embodiments except for the fuel injection nozzle 400 (see FIG. 1). In the third embodiment, the shape of the injection hole 401 of the fuel injection nozzle 400 is different from the shape of the injection holes 101 and 301 of the fuel injection nozzles 100 and 300 of the first and second embodiments. FIG. 8 shows a partially enlarged sectional view of the vicinity of the injection hole 401 according to the third embodiment. FIG. 8 is a drawing corresponding to FIGS. 3 and 7 of the first and second embodiments, and shows a longitudinal sectional view of the injection hole 401.

  The fuel injection nozzle 400 of the third embodiment also has a dome shape having a hemispherical outer surface 400a and a hemispherical inner surface 400b, and a plurality of injection holes 401, 401,. Each injection hole 401 is located between the outer opening end 402 positioned at the end on the outer surface 400a side, the inner opening end 403 positioned at the end on the inner surface 400b side, and the outer opening end 402 and the inner opening end 403. And it is comprised from the narrow diameter part 404 whose hole diameter is smaller than these.

Both the outer opening end 302 and the inner opening end 303 have a hole diameter of 100 μm.
The narrow-diameter portion 404 has an outer tapered portion 404f that gradually decreases in hole diameter from the outer opening end 402 toward the inner surface 400b, and an inner tapered portion 404g that decreases in diameter gradually from the inner opening 403 toward the outer surface 400a. And has a shape with the smallest hole diameter at these boundary portions.

  In the third embodiment, unlike the second embodiment, the length of the outer tapered portion 404f (the length in the central axis BX direction) is longer than the length of the inner tapered portion 404g (the length in the central axis BX direction). It has been shortened. Of the small diameter portion 404, the portion having the smallest hole diameter, that is, the hole diameter (minimum hole diameter) of the corner portion 404c described below is 100 μm or less (75 μm in this example). The small-diameter portion 404 has one corner portion 404c that protrudes toward the central axis BX at the boundary portion between the outer tapered portion 404f and the inner tapered portion 404g. The corner portion 404c has an obtuse angle (150 degrees in this example) in the longitudinal section of the injection hole 401.

As described above, the injection hole 401 according to the third embodiment also includes the small-diameter portion 404 having the corner portion 404c protruding toward the central axis BX. The injection hole 401 narrows the narrow-diameter portion 404. Specifically, the small-diameter portion 404 has a small diameter in the corner portion 404c, while the small-diameter portion 404 has a small diameter in the flow path on both ends (outer surface 400a side and inner surface 400b side). It is wider than the part 404. Therefore, the pressure loss related to fuel injection can be reduced. In addition, since the fuel injection nozzle 400 is made of ceramic, the strength of the injection hole 401 is high. Moreover, since the angle α formed by the corner portion 404c of the narrow diameter portion 404 of the injection hole 401 is an obtuse angle, even when a high stress is applied to the corner portion 404c during use, the corner portion 404c is strong and hardly damaged. The injection hole 401 is hardly damaged. Therefore, the pressure loss related to fuel injection can be reduced, and the fuel injection nozzle 400 can be made highly reliable with less damage to the injection hole 401.
In addition, the same parts as those in the first or second embodiment have the same functions and effects as those in the first or second embodiment.

(Embodiment 4)
Next, a fourth embodiment will be described. In addition, description of the part similar to either of the said Embodiments 1-3 is abbreviate | omitted or simplified. The fuel injection device 510 of the fourth embodiment is the same as the fuel injection devices 100, 300, 400, 500 of the first to third embodiments except for the fuel injection nozzle 500 (see FIG. 1). In the fourth embodiment, the shape of the injection hole 501 of the fuel injection nozzle 500 is different from the shape of the injection holes 101, 301, 401 of the fuel injection nozzles 100, 300, 400 of the first to third embodiments. FIG. 9 shows a partially enlarged sectional view of the vicinity of the injection hole 501 according to the fourth embodiment. 9 is a drawing corresponding to FIGS. 3, 7, and 8 of the first to third embodiments, and shows a longitudinal sectional view of the injection hole 501. FIG.

  The fuel injection nozzle 500 of the fourth embodiment also has a dome shape having a hemispherical outer surface 500a and a hemispherical inner surface 500b, and a plurality of injection holes 501, 501,. In the fourth embodiment, each injection hole 501 includes an outer opening end 502 positioned at the end on the outer surface 500a side, an inner opening portion 503 including an inner opening end 503e positioned at the end on the inner surface 500b side, and an outer opening end. It is comprised between 502 and the inner side opening part 503, and the small diameter part 504 whose hole diameter is smaller than these.

The hole diameter of the outer opening end 502 is 100 μm as in the third embodiment.
On the other hand, unlike the third embodiment, the hole diameter of the inner opening end 503e is larger than the hole diameter of the outer opening end 502 and is 200 μm. The inner opening 503 including the inner opening end 503e has a tapered shape in which the hole diameter gradually decreases from the inner opening end 503 toward the outer surface 500a. The minimum hole diameter of the inner opening 503 is 100 μm, similar to the hole diameter of the outer opening end 502.

  The small diameter portion 504 has an outer tapered portion 504f that gradually decreases in hole diameter from the outer opening end 502 toward the inner surface 500b side, and an inner tapered portion 504g that gradually decreases in hole diameter from the inner tapered portion 503 toward the outer surface 500a side. In these boundary portions (in the center of the center in the direction of the central axis BX), the shape having the smallest hole diameter is formed. The hole diameter (minimum hole diameter) of the central portion having the smallest hole diameter among the small diameter portions 504, that is, the corner portion 504c described below is 100 μm or less (75 μm in this example). The small-diameter portion 504 has one corner portion 504c protruding toward the central axis BX at the center of the small-diameter portion 504 in the central axis BX direction. The corner portion 504c has an obtuse angle (150 degrees in this example) in the longitudinal section of the injection hole 501.

As described above, the injection hole 501 according to the fourth embodiment also includes the small-diameter portion 504 having the corner portion 504c protruding toward the central axis BX. The injection hole 501 narrows the narrow diameter portion 504. Specifically, the narrow diameter portion 504 reduces the diameter of the corner portion 504c, while narrowing the flow path on both ends (outer surface 500a side and inner surface 500b side). It is wider than the part 504. Therefore, the pressure loss related to fuel injection can be reduced. In addition, since the fuel injection nozzle 500 is made of ceramic, the strength of the injection hole 501 is high. Moreover, since the angle α formed by the corner portion 504c of the small diameter portion 504 of the injection hole 501 is an obtuse angle, the corner portion 504c is strong and difficult to break even when high stress is applied to the corner portion 504c during use. The injection hole 501 is not easily damaged. Therefore, the pressure loss related to fuel injection can be reduced, and the fuel injection nozzle 500 can be made highly reliable with less damage to the injection hole 501.
In addition, the same part as any one of the first to third embodiments has the same actions and effects as the first to third embodiments.

In the above, the present invention has been described with reference to the embodiments. However, the present invention is not limited to the above-described first to fourth embodiments, and can be appropriately modified and applied without departing from the gist thereof. Not too long.
For example, in Embodiments 1 to 4 described above, the fuel injection nozzle 100 or the like is made of alumina, but the fuel injection nozzle 100 or the like may be formed using silicon nitride, zirconia, or the like.

1 is a longitudinal sectional view of a fuel injection device according to Embodiment 1. FIG. It is a longitudinal cross-sectional view of the fuel injection nozzle which concerns on Embodiment 1. FIG. It is a partial expanded sectional view of an injection hole vicinity among the fuel injection nozzles concerning Embodiment 1. FIG. It is explanatory drawing which shows a mode that a non-baking body is formed by injection molding regarding the manufacturing method of the fuel injection nozzle which concerns on Embodiment 1. FIG. FIG. 5 is an explanatory view showing, in an enlarged manner, the vicinity of the injection hole in FIG. 4 with respect to the method for manufacturing the fuel injection nozzle according to the first embodiment. It is explanatory drawing which shows the unbaking body before baking regarding the manufacturing method of the fuel injection nozzle which concerns on Embodiment 1. FIG. It is a partial expanded sectional view of an injection hole vicinity among the fuel injection nozzles concerning Embodiment 2. FIG. It is a partial expanded sectional view of an injection hole vicinity among the fuel injection nozzles concerning Embodiment 3. FIG. It is a partial expanded sectional view near an injection hole among fuel injection nozzles concerning Embodiment 4.

Explanation of symbols

100, 300, 400, 500 Fuel injection nozzles 100a, 300a, 400a, 500a Outer surfaces 100b, 300b, 400b, 500b Inner surfaces 101, 301, 401, 501 Injection holes 102, 302, 402, 502 Outer opening ends 103e, 303, 403 , 503e Inner opening end 103, 503 Inner opening 104, 304, 404, 504 Small diameter part 104f, 304f, 404f, 504f Outer taper part 104g, 304g, 404g, 504g Inner taper part 304h Straight part 104c, 404c, 504c Angle Part 304c1 outside corner (corner)
304c2 Inner corner (corner)
110, 310, 410, 510 Fuel injector 111 Multilayer piezoelectric element (molded unit laminate)
120 Main body member 130 Nozzle member 131 Nozzle base end member BX Central axis α angle β angle

Claims (3)

A fuel injection nozzle made of ceramic and provided with injection holes,
The injection hole has a small-diameter portion having a hole diameter smaller than the hole diameters at both ends inside itself,
The injection hole has, in the longitudinal section of the injection hole, one or a plurality of corners protruding toward the central axis of the injection hole in the small diameter portion.
A fuel injection nozzle in which the angles formed by the corners of the narrow diameter part are all obtuse. The fuel injection nozzle according to claim 1,
A fuel injection nozzle having a minimum hole diameter of 100 μm or less in the small diameter portion. A fuel injection device comprising the fuel injection nozzle according to claim 1.

Images