TWI859451B - Nozzle for irregular cross-section glass fiber, and method for producing irregular cross-section glass fiber - Google Patents

Abstract

In order to make it possible to manufacture glass fibers with a high flatness and a special cross section. A nozzle (8) for glass fibers with a special cross section is provided with an inlet (6a) and an outlet (6b) for molten glass (2) and a nozzle hole (6) with a flat cross section. The nozzle hole (6) includes: a pair of short wall portions (12) facing each other in the long diameter direction of the flat cross section of the nozzle hole (6), and a pair of long wall portions (13) facing each other in the short diameter direction of the flat cross section of the nozzle hole (6). 11), the nozzle (8) for irregular cross-section glass fiber is used to manufacture irregular cross-section glass fiber (2f) from molten glass (2) flowing out from a nozzle hole (6), and each of a pair of short wall portions (12) has an end region (T) at the end portion located on the flow outlet (6b) side of the short wall portion (12) and has an inclined portion (12aa) inclined relative to the axis (6x) of the nozzle hole (6).

Description

Nozzle for irregular cross-section glass fiber, and method for producing irregular cross-section glass fiber

The present invention relates to a nozzle for producing a flat irregular cross-section glass fiber from molten glass, and a method for producing the irregular cross-section glass fiber using the nozzle.

As a type of glass fiber, a flat cross-sectional irregular glass fiber is known (see Patent Document 1). When the irregular cross-sectional glass fiber is compounded with a resin, a good reinforcement effect can be achieved. Therefore, it is used as a fiber for fiber reinforced plastic (FRP) and the like and is used in various fields.

When manufacturing a glass fiber with an irregular cross section, for example, molten glass is supplied from a feeder for flowing molten glass to a bushing, and the molten glass is drawn out and cooled from a plurality of nozzles provided on the bushing. The shape of the nozzle hole provided in the nozzle is generally a flat hole (elliptical, oblate, etc.). [Prior art literature] [Patent literature]

[Patent Document 1] International Publication No. 2017/221471

[The problem the invention is trying to solve]

When manufacturing glass fibers with irregular cross sections, there are the following problems to be solved: That is, the molten glass flowing out of the nozzle hole is deformed in a way that the surface area becomes smaller due to the action of surface tension, so it is difficult to form glass fibers with irregular cross sections with a high flatness.

In view of the above, the technical problem that the present invention aims to solve is to make it possible to manufacture irregular cross-section glass fibers with high flatness when manufacturing irregular cross-section glass fibers. [Technical means for solving the problem]

The nozzle for irregular-section glass fiber of the present invention for solving the above-mentioned problem is provided with a nozzle hole having an inlet and an outlet for molten glass and having a flat cross-section. The nozzle hole comprises: a pair of short wall portions which are opposite to each other in the long diameter direction of the flat cross-section of the nozzle hole, and a pair of long wall portions which are opposite to each other in the short diameter direction of the flat cross-section of the nozzle hole. The nozzle for irregular-section glass fiber is used to manufacture irregular-section glass fiber from molten glass flowing out of the nozzle hole. Each of the pair of short wall portions has an inclined portion which is inclined relative to the axis of the nozzle hole at the end region of the end portion located on the outlet side of the short wall portion.

According to the present nozzle, the end region has an inclined portion that is inclined relative to the axis of the nozzle hole, and the contact area between the end region and the molten glass is expanded compared to the conventional case where there is no inclined portion in the end region. As a result, the ability of the end region of the short wall portion to stretch the molten glass (the ability to stretch in the long diameter direction of the flat cross section of the nozzle hole) is improved, and with this, the molten glass can be suppressed from being deformed in a manner that the surface area becomes smaller due to the surface tension. As a result, the manufactured irregular cross-section glass fiber can be formed with a high flatness.

The nozzle for glass fiber with a special cross section of the present invention preferably has an inclined portion having an inclined surface that is inclined so as to be separated from the center side of the flat cross section of the nozzle hole as it moves from the inlet side of the molten glass toward the outlet side.

According to this structure, the ability of the end region of the short wall portion to draw the molten glass is further improved, which becomes more advantageous in forming a glass fiber with a special cross section at a high flatness.

The nozzle for irregular cross-section glass fiber of the present invention is preferably that the short wall portion has a bottom wall surface connected to the inclined portion in the end area, and the long wall portion has a bottom wall surface at the end on the outlet side, and the sum of the length of the inclined portion and the length of the bottom wall surface of the short wall portion in the cross-section perpendicular to the short diameter direction of the flat cross-section of the nozzle hole is longer than the length of the bottom wall surface of the long wall portion in the cross-section perpendicular to the long diameter direction of the flat cross-section of the nozzle hole.

When manufacturing a special-shaped cross-section glass fiber, in addition to the inclined portion of the short wall portion, the bottom wall surface of the short wall portion and the long wall portion is also wetted by molten glass. At this time, the inclined portion and the bottom wall surface stretch the molten glass. Furthermore, in order to improve the flatness of the manufactured special-shaped cross-section glass fiber, it is more advantageous to stretch it along the long diameter direction of the flat cross-section of the nozzle hole than to stretch it along the short diameter direction of the flat cross-section of the nozzle hole. Moreover, according to this structure, the molten glass can be effectively stretched along the long diameter direction of the flat cross-section of the nozzle hole, which is more advantageous in forming the special-shaped cross-section glass fiber with a high flatness.

The nozzle for the irregular-section glass fiber of the present invention is preferably such that the inclined portion is composed of a single inclined surface.

According to this structure, molten glass becomes less likely to stagnate, and devitrification can be suppressed.

Furthermore, the method for manufacturing irregular-section glass fiber of the present invention for solving the above-mentioned problem is a method for manufacturing irregular-section glass fiber from molten glass flowing out of the nozzle hole using a nozzle for irregular-section glass fiber provided with a nozzle hole, wherein the nozzle hole has an inlet and an outlet for the molten glass and has a flat cross-section, and includes: a pair of short wall portions opposite to each other in the long diameter direction of the flat cross-section of the nozzle hole, and a pair of long wall portions opposite to each other in the short diameter direction of the flat cross-section of the nozzle hole, each of the pair of short wall portions having an inclined portion inclined relative to the axis of the nozzle hole at an end region of the end portion located on the outlet side of the short wall portion.

According to this method, the same functions and effects as those described for the nozzle for irregular cross-section glass fiber of the above-mentioned invention can be obtained. [Effects of the invention]

According to the present invention, when manufacturing glass fibers with special cross-sections, it is possible to manufacture fibers with high flatness.

The following is a description of the nozzle for irregular cross-section glass fiber and the method for manufacturing irregular cross-section glass fiber according to the embodiment of the present invention, with reference to the attached drawings. In this specification, the numerical range represented by "～" is the range in which the numerical values recorded before and after "～" are respectively the minimum and maximum values.

As shown in FIG1 , a glass fiber with an irregular cross section is manufactured by a manufacturing device 1. The manufacturing device 1 includes a feeder 3 for flowing molten glass 2 generated by a melting furnace (not shown), a leak plate 4 arranged below the feeder 3, and a pipe 5 for connecting the feeder 3 and the leak plate 4. The molten glass 2 is supplied from the feeder 3 to the leak plate 4 through the pipe 5. Then, the molten glass 2 flows out from the nozzle hole 6 of the leak plate 4. The molten glass 2 is cooled to become a glass fiber 2f with an irregular cross section (hereinafter referred to as "glass fiber 2f").

In the present embodiment, the molten glass 2 is made of E glass. However, the present invention is not limited thereto, and the molten glass 2 may be made of other glass such as D glass, S glass, AR glass, or C glass.

The feeder 3 is connected to a glass melting furnace (not shown). The feeder 3 allows the molten glass 2 continuously generated in the glass melting furnace to flow. A liquid surface 2a of the molten glass 2 is formed inside the feeder 3.

The drain plate 4 has a bottom plate 7 at the bottom. The bottom plate 7 has: a plurality of nozzles 8 for irregular cross-section glass fibers (hereinafter referred to as "nozzles 8"), and a cooling pipe 9 arranged near the nozzles 8. The plurality of nozzles 8 have the same structure as each other. As described in detail later, the nozzle hole 6 provided in each nozzle 8 is formed flat.

The tube 5 is formed into a cylindrical shape with the tube axis extending in the vertical direction. The upper end of the tube 5 is connected to the bottom of the feeder 3, and the lower end of the tube 5 is connected to the upper end of the bushing 4. The tube 5 can be any tube that can connect the feeder 3 and the bushing 4, and its shape and the extending direction of the tube axis may be different from those of the present embodiment.

Each component such as the bushing 4, the tube 5, the nozzle 8 and the cooling tube 9 is partially or entirely made of platinum or a platinum alloy (e.g., a platinum-rhodium alloy). In the present embodiment, the tube 5 among these components is entirely made of platinum or a platinum alloy.

The entire flow path from the connection between the feeder 3 and the tube 5 to the nozzle hole 6 of the bushing 4 is filled with molten glass 2. Thus, the pressure (pressure difference (head pressure)) for the molten glass 2 to flow out from the nozzle hole 6 is determined by the height difference H between the nozzle hole 6 and the liquid level 2a of the molten glass 2 in the feeder 3. Here, the height difference H can be adjusted by, for example, changing the length of the tube 5.

The temperature and viscosity of the molten glass 2 when the glass fiber 2f is formed are set to 1100°C to 1250°C (preferably 1150°C to 1200°C) and 10 _2.6 dPa･s to 10 _3.8 dPa･s (preferably 10 _2.9 dPa･s to 10 _3.3 dPa･s). The "temperature and viscosity of the molten glass 2" referred to herein are the temperature and viscosity of the molten glass 2 at the position where it flows into the nozzle 8. The temperature and viscosity of the molten glass 2 can be adjusted, for example, by heating the bushing 4 and the tube 5 individually by any heating means (for example, an electric heating device). In addition, the temperature and viscosity of the molten glass 2 can be adjusted by heating the molten glass 2 and the feeder 3 in the glass melting furnace by electric heating.

The surface of the glass fiber 2f is coated with a bundling agent by an applicator (not shown). Thus, hundreds to thousands of glass fibers 2f are spun into a strand 2s. The spun strand 2s is wound around a bobbin 10 of a winding device into a fiber bundle 2r. The strand 2s is cut into a length of about 1 mm to 20 mm and used as a chopped strand.

As shown in FIG. 2 and FIG. 3 , the nozzle 8 has a pair of long wall portions 11, 11 and a pair of short wall portions 12, 12. The nozzle hole 6 is surrounded by the long wall portions and the short wall portions and has a flat cross section. The nozzle hole 6 has an inlet 6a for the molten glass 2 to flow in, and an outlet 6b for the molten glass 2 to flow out. A notch portion 13 opening toward the outlet 6b side is provided in the pair of long wall portions 11, 11, respectively. Thereby, the nozzle hole 6 is connected to the external space of the nozzle 8 through the notch portion 13.

The cooling tube 9 allows cooling water 14 to circulate inside to cool the molten glass 2. The outer shape of the cooling tube 9 is formed in a plate shape, and the plate surface is parallel to the long wall portion 11. Here, the cooling tube 9 is provided integrally with the bottom plate 7, but it can also be provided at a position separated from the bottom plate 7. The cooling tube 9 can also be formed in a round tube shape.

The height position of the cooling tube 9 can be adjusted according to the cooling conditions of the molten glass 2. For example, the cooling tube 9 can be arranged above the lower end of the nozzle 8 to avoid its plate surface facing the molten glass 2 pulled out from the nozzle 8. On the other hand, the cooling tube 9 can be arranged across the upper and lower parts of the lower end of the nozzle 8, so that the plate surface of the cooling tube 9 faces both the nozzle 8 and the molten glass 2 pulled out from the nozzle 8. In addition to the cooling tube 9, a heat sink that uses air flow for cooling can also be used for cooling the molten glass 2. The cooling tube 9 is not a necessary structure and can be omitted.

A plurality of nozzle rows P are arranged in parallel at intervals on the bottom plate 7. Each nozzle row P includes a plurality of nozzles 8. The plurality of nozzles 8 belonging to the same nozzle row P are arranged so that the nozzle holes 6 formed therein are located on the same straight line.

The cooling tube 9 is arranged between two adjacent nozzle rows P, P so as to extend parallel to the nozzle row P. Thus, the molten glass 2 in the nozzle hole 6 is cooled through the notch 13 facing the cooling tube 9. Specifically, the molten glass 2 is rapidly cooled from a temperature of more than 1000°C by the cooling tube 9. Here, the cooling tube 9 also has the following function, that is, by cooling the leak plate 4 (bottom plate 7) and the nozzle 8, the degradation of these components caused by heat is suppressed and the durability is improved.

As shown in Fig. 4 (a) and (b), the notch 13 provided in the long wall portion 11 of each nozzle 8 is an isosceles trapezoid whose upper base is shorter than the lower base. Thus, the notch 13 gradually expands its opening width from the inlet 6a side of the nozzle hole 6 toward the outlet 6b side. The depth of the notch 13 (the length in the direction of the axis 6x connecting the inlet 6a and the outlet 6b of the nozzle hole 6) is set to 0.1 mm to 2 mm. This is because, when the depth of the notch 13 exceeds 2 mm, the two ends in the long side direction of the cross section of the manufactured glass fiber 2f become too thin, and the glass fiber 2f becomes easy to be damaged.

The shape of the notch 13 is not limited to a trapezoid, and may be other shapes. For example, it may be a triangle, a semicircle, or a rectangle. However, even if other shapes are adopted, the notch 13 is preferably such that its opening width gradually increases from the inlet 6a side of the nozzle hole 6 toward the outlet 6b side.

As shown in FIG. 4 , in the present embodiment, a single nozzle hole 6 is provided in a nozzle 8. The nozzle hole 6 is formed in a long hole shape. A pair of long wall portions 11, 11 are opposed to each other in the short diameter direction of the flat cross section of the nozzle hole 6, and a pair of short wall portions 12, 12 are opposed to each other in the long diameter direction of the flat cross section of the nozzle hole 6. In the present embodiment, the thickness of the short wall portion 12 (the thickness along the long diameter direction of the flat cross section of the nozzle hole 6) is greater than the thickness of the long wall portion 11 (the thickness along the short diameter direction of the flat cross section of the nozzle hole 6). Here, the aspect ratio (the ratio of the long diameter to the short diameter) of the nozzle hole 6 is set to 2 to 5. The inner circumference of the nozzle hole 6 including the inner wall surface 11a of the long wall portion 11 and the inner wall surface 12a of the short wall portion 12 is made of platinum or a platinum alloy. The inner wall surface 11a of the long wall portion 11 is straight as shown in FIG. 4(c), and the inner wall surfaces 11a facing each other are parallel to each other.

The boundary 15 between the long wall portion 11 and the short wall portion 12 is the point where the slope of the inner wall surface relative to the left and right directions of FIG. 4( c ) changes from 0. The portion where the slope is 0 relative to the left and right directions of FIG. 4( c ) is the long wall portion 11, and the portion other than the slope of 0 is the short wall portion 12.

As shown in FIG. 4( b) and FIG. 5 , each of the pair of short wall portions 12, 12 has an inclined portion 12aa that is inclined relative to the axis 6x of the nozzle hole 6 in the end region T of the end portion located on the outlet 6b side thereof. Specifically, the inclined portion 12aa is inclined from the center side of the flat cross section of the nozzle hole 6 toward the outside (from the inside side of the long diameter direction of the flat cross section of the nozzle hole 6 toward the outside) as it moves from the inlet 6a side toward the outlet 6b side. Thus, the inclined portion 12aa located on one of the pair of short wall portions 12, 12 and the inclined portion 12aa located on the other side are inclined in opposite directions to each other. The two inclined portions 12aa, 12aa are respectively constituted by a single inclined surface (inclined plane). The inclined portion 12aa is formed over the entire length of the short wall portion 12 along the short diameter direction of the flat cross-section of the nozzle hole 6 (in Figure 4 (b) and Figure 5, the direction perpendicular to the paper surface). The angle θ1 at which the inclined portion 12aa is inclined relative to the line orthogonal to the axis 6x is not particularly limited, and is 55° in the present embodiment. The inclined portion 12aa may also be a curved surface as long as it is inclined relative to the axis 6x of the nozzle hole 6. The surface roughness of the inclined portion 12aa may be greater than the surface roughness of the inner wall surface 12a. The angle θ1 at which the inclined portion 12aa is inclined relative to a line perpendicular to the axis 6x is preferably not less than 10° and not more than 80°.

The short wall portion 12 has a bottom wall surface 12b connected to the inclined portion 12aa. In detail, the inclined portion 12aa is connected to the bottom wall surface 12b on the outer side in the major diameter direction of the nozzle hole 6. In the present embodiment, the bottom wall surface 12b is a flat surface orthogonal to the axis 6x. Here, the length of the inclined portion 12aa is set to L1, and the length of the bottom wall surface 12b is set to L2. Moreover, "the length L1 of the inclined portion 12aa and the length L2 of the bottom wall surface 12b" are respectively the lengths on the cross section orthogonal to the minor diameter direction of the flat cross section of the nozzle hole 6.

As a result, the end region T of the present embodiment becomes larger than that of the case without the inclined portion 12aa. Specifically, in the present embodiment, the approximate area of the end region T is the value obtained by multiplying the sum of the length L1 of the inclined portion 12aa and the length L2 of the bottom wall surface 12b by the circumference of the short wall portion 12, while the approximate area of the end region of the conventional case without the inclined portion 12aa is the value obtained by multiplying the sum of the length L2 of the bottom wall surface 12b and the length L3 of the imaginary bottom wall surface by the circumference of the short wall portion 12. The relationship between L1 and L3 is L1=L3/cos55°=1.74×L3. That is, the approximate area of the end region T of the present embodiment is larger than the approximate area of the end region in the conventional case where there is no inclined portion 12aa.

As shown in FIG6 , the long wall portion 11 has a bottom wall surface 11b. The bottom wall surface 11b of the long wall portion 11 where the notch portion 13 is provided is a portion corresponding to the upper base of the isosceles trapezoid, or a portion of the side connecting the upper base and the lower base. In the present embodiment, the bottom wall surface 11b is a flat surface (a flat surface orthogonal to the axis 6x at a portion corresponding to the upper base of the isosceles trapezoid). Here, the length of the bottom wall surface 11b is set to L4. The "length of the bottom wall surface 11b" is the length on the cross section orthogonal to the major diameter direction of the flat cross section of the nozzle hole 6. Moreover, compared to the length L4, the sum of the above-mentioned length L1 and length L2 is longer. Thus, the area of the end region T of the short wall portion 12 is made larger than the area of the bottom wall surface 11b of the long wall portion 11, and the molten glass 2 is more easily stretched along the long diameter direction than the short diameter direction of the flat cross section of the nozzle hole 6.

The main functions and effects of the method for producing a glass fiber with a special cross section using the above-mentioned nozzle 8 will be described below.

According to the nozzle 8, the end region T has the inclined portion 12aa which is inclined relative to the axis 6x of the nozzle hole 6. Compared with the case where the end region T does not have the inclined portion 12aa, the contact area between the end region T and the molten glass 2 is expanded. As a result, the ability of the short wall portion 12 to stretch the molten glass 2 is improved, and with this, the deformation of the molten glass 2 in a manner that the surface area becomes smaller under the action of the surface tension can be suppressed. As a result, it is possible to manufacture a glass fiber 2f with a high flatness as shown in FIG. 7. Here, the cross-sectional shape of the glass fiber 2f is formed into a shape close to an oblate circle.

Here, the nozzle for the irregular cross-section glass fiber and the method for manufacturing the irregular cross-section glass fiber of the present invention are not limited to the configuration and mode described in the above-mentioned embodiment. For example, as shown in FIG8 , the long wall portion 11 may have an inclined portion 11aa. The inclined portion 11aa is inclined at an angle θ2 relative to a line perpendicular to the axis 6x, preferably not less than 10° and not more than 80°. By setting θ1>θ2, the ability of the inner wall surface 11a of the long wall portion 11 to stretch the molten glass 2 does not become too large, and the flatness of the glass fiber can be suppressed from becoming smaller.

Furthermore, when the inclined portion 11aa is provided on the long wall portion 11, the inclined portion 11aa is not provided on the central side of the long wall portion 11, but is provided only on the two end sides of the long wall portion 11, so that the ability of the long wall portion 11 to draw the molten glass 2 does not become too large, and the flatness of the glass fiber can be suppressed from being reduced. For example, as shown in FIG. 9, the inclined portion 11aa is provided on the long wall portion 11 other than the upper bottom of the notch portion 13 of the isosceles trapezoid, and the inclined portion 11aa is not provided on the upper bottom of the notch portion 13, so that the flatness of the glass fiber can be suppressed from being reduced.

In the above embodiment, although the notch 13 is provided in each of the pair of long wall portions 11, 11, it is not necessary to provide the notch 13 and it is also possible to remove it. In addition to the long hole shape, the nozzle hole 6 can also be an ellipse, dumb bell, diamond, rectangle, three connected perfect circles, etc.

2: Molten glass 2f: Irregular cross-section glass fiber 6: Nozzle hole 6a: Inlet 6b: Outlet 6x: Axis 8: Nozzle for irregular cross-section glass fiber 11: Long wall 11b: Bottom wall 12: Short wall 12a: Inner wall 12aa: Inclined part 12b: Bottom wall L1: Length L2: Length L3: Length T: End area

[FIG. 1] is a cross-sectional view schematically showing a manufacturing apparatus for irregular cross-section glass fiber equipped with a nozzle for irregular cross-section glass fiber according to the present embodiment. [FIG. 2] is a cross-sectional view schematically showing the periphery of the nozzle for irregular cross-section glass fiber according to the present embodiment. [FIG. 3] is a bottom view schematically showing the periphery of the nozzle for irregular cross-section glass fiber according to the present embodiment. [Figure 4] shows the nozzle for irregular cross-section glass fiber of the present embodiment, Figure 4(a) is a side view of the nozzle for irregular cross-section glass fiber observed from the long wall side, Figure 4(b) is a 4b-4b cross-sectional view of the nozzle of Figure 3, and Figure 4(c) is a 4c-4c cross-sectional view of Figure 4(a). [Figure 5] is a cross-sectional view showing the enlarged A part of Figure 4(b). [Figure 6] is a cross-sectional view showing the periphery of the bottom wall surface of the long wall portion of the nozzle for irregular cross-section glass fiber of the present embodiment. [Figure 7] is a cross-sectional view showing the irregular cross-section glass fiber. [Figure 8] shows a modified example of a nozzle for irregular cross-section glass fiber. Figure 8(a) is a side view of the nozzle for irregular cross-section glass fiber observed from the short wall side, Figure 8(b) is a 4b-4b cross-sectional view of the nozzle in Figure 3, and Figure 8(c) is a 4d-4d cross-sectional view of Figure 8(a). [Figure 9] is a bottom view of a modified example of a nozzle for irregular cross-section glass fiber.

6: Nozzle hole

6a: Inflow port

6b: Outflow port

6x: axis

8: Nozzle for special-shaped cross-section glass fiber

11: Long wall section

11a: Inner wall surface

11b: Bottom wall

12: Short wall section

12a: Inner wall surface

12aa: inclined part

12b: Bottom wall

13: Notch

15: Boundary

T: End area

Claims (4)

A nozzle for glass fiber with an irregular cross section is provided with a nozzle hole having an inlet and an outlet for molten glass and having a flat cross section, wherein the nozzle hole comprises: a pair of short wall portions facing each other in the long diameter direction of the flat cross section, and a pair of long wall portions facing each other in the short diameter direction of the flat cross section. The nozzle for glass fiber with an irregular cross section is used to manufacture glass fiber with an irregular cross section from molten glass flowing out of the nozzle hole. Among the pair of short wall portions and the pair of long wall portions, only the pair of short wall portions has an end region located before the short wall portion on the side of the flow outlet, which has an inclined portion inclined relative to the axis of the nozzle hole and a bottom wall surface connected to the inclined portion, and the inclined portion has an inclined surface that is inclined away from the center side of the flat cross section of the nozzle hole as it moves from the side of the flow inlet toward the side of the flow outlet. The nozzle for glass fiber with an irregular cross section as described in claim 1, wherein the long wall portion has a bottom wall surface at the end portion on the outlet side, and the sum of the length of the inclined portion and the length of the bottom wall surface of the short wall portion on the cross section perpendicular to the short diameter direction is longer than the length of the bottom wall surface of the long wall portion on the cross section perpendicular to the long diameter direction. A nozzle for irregular cross-section glass fiber as described in claim 1 or 2, wherein the inclined portion is composed of a single inclined surface. A method for manufacturing a glass fiber with an irregular cross section is a method for manufacturing a glass fiber with an irregular cross section from molten glass flowing out of a nozzle hole using a nozzle for glass fiber with an irregular cross section, wherein the nozzle hole has an inlet and an outlet for molten glass and has a flat cross section and includes: a pair of short wall portions facing each other in the long diameter direction of the flat cross section, and a pair of long wall portions facing each other in the short diameter direction of the flat cross section. Among the aforementioned pair of short wall portions and the aforementioned pair of long wall portions, only the aforementioned pair of short wall portions each have an end region at an end portion of the short wall portion located on the aforementioned outflow outlet side, which has an inclined portion inclined relative to the axis of the aforementioned nozzle hole and a bottom wall surface connected to the aforementioned inclined portion, wherein the aforementioned inclined portion has: an inclined surface inclined in a manner of departing from the center side of the flat cross-section of the aforementioned nozzle hole as it moves from the aforementioned inflow inlet side toward the aforementioned outflow outlet side.

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