Injection Nozzle

Abstract

To provide an injection nozzle with a structure in which a tip spherical portion is strongly cooled.SOLUTION: In Fig.6(a), a refrigerant is supplied to a refrigerant supply passage 45 according to an arrow (1). The refrigerant flows through a vertical hole 47 and a horizontal hole 46 in this order, and, as shown by an arrow (2), flows into a refrigerant chamber 56 . As shown in Fig.6(b), the refrigerant passes through inside a pipe 31, jets out from a tip of the pipe 31, and collides with a small diameter hole 28 (arrow (3)). After the collision, the refrigerant reverses and flows through outside the pipe 31 (arrow (4)), and flows into a refrigerant discharge passage 50 as shown in Fig.6(a). By colliding the refrigerant, a tip spherical portion 15 is strongly cooled.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to an injection nozzle for use in injection molding of a thermosetting resin. [Background technology]

[0002] Injection molding is a widely known technique for manufacturing resin products, in which a resin material is injected from an injector into a mold. The resin material includes thermoplastic resin and thermosetting resin.

[0003] In the case of thermoplastic resin, the resin material is plasticized in an injector, injected in a molten state into a mold, and solidified by cooling in the mold. In contrast, in the case of thermosetting resin, the resin material is preheated in an injector, injected in a molten state into a mold, and solidified by being heated in the mold.

[0004] In the case of a thermosetting resin, the temperature of the injection nozzle provided at the tip of the injector is 60 to 85°C, and the temperature of the mold is 160 to 180°C. During injection, the injection nozzle is pressed against the sprue of the mold. This action is called the nozzle touch. During the nozzle touch, the injection nozzle is heated by the mold, and the temperature of the injection nozzle rises.

[0005] When the temperature of the injection nozzle exceeds a certain value, the thermosetting resin material inside the injection nozzle becomes less fluid. When the resin material is filled into the cavity of the mold, poor fluidity causes filling defects. Poor filling results in defective products, such as chipped resin products. The occurrence of defective products must be avoided. Therefore, various techniques for solving the defects have been proposed (for example, see Patent Document 1 (FIG. 1)).

[0006] Patent Document 1 will be explained with reference to the following figure. FIG. 11 is a diagram illustrating the basic configuration of a conventional injection nozzle. An injection nozzle 100 comprises a nozzle body 101 and a nozzle cover 111. The nozzle body 101 has at its base a male thread portion 103 that is screwed into the heater barrel 102, and at its tip a first nozzle land 104 and a second nozzle land 105. The first nozzle land 104 corresponds to the tip spherical portion that is brought into contact with the mold.

[0007] The nozzle cover 111 is attached to the nozzle body 101 to form a coolant passage 112. The second nozzle land 105 is directly cooled by flowing a coolant such as air, water, or oil through the coolant passage 112. The first nozzle land 104 is cooled by heat transfer to the second nozzle land 105. In other words, the first nozzle land 104 is indirectly cooled by the coolant.

[0008] The injection nozzle 100 disclosed in Patent Document 1 has the following drawbacks. Compared to the second nozzle land 105 which is directly cooled by the coolant, the first nozzle land 104 which is indirectly cooled is cooled to a smaller extent. In the mold, the first nozzle land 104 is heated more than the second nozzle land 105 . As a result, the temperature of the first nozzle land 104 rises, and the fluidity of the resin material deteriorates. This deterioration in fluidity hinders injection molding.

[0009] In order to maintain good fluidity, it is desirable that the first nozzle land 104 be cooled more strongly than the second nozzle land 105. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 9-24525 Summary of the Invention [Problem to be solved by the invention]

[0011] An object of the present invention is to provide an injection nozzle having a structure in which the tip spherical portion corresponding to the first nozzle land is strongly cooled. [Means for solving the problem]

[0012] The invention according to claim 1 is an injection nozzle for injecting a thermosetting resin, the injection nozzle having a male threaded portion that is screwed into a heating barrel and a spherical tip portion that is brought into contact with a mold, The injection nozzle is provided with at least one elongated hole extending from the male thread portion to the vicinity of the tip spherical portion, a refrigerant supply passage is provided from the outer surface of the injection nozzle to the elongated hole for supplying refrigerant, and a refrigerant discharge passage is provided from the elongated hole to the outer surface of the injection nozzle for discharging warmed refrigerant, A pipe structure is inserted into the long hole toward the tip spherical portion, and a plug structure is inserted into the male thread portion, The plug structure and the pipe structure are spaced apart by a predetermined distance to form a coolant chamber, and the coolant supply passage is connected to the coolant chamber. The pipe structure includes a pipe having a diameter smaller than the diameter of the long hole, and a pipe support that supports a base of the pipe, has an outer diameter corresponding to the diameter of the long hole, and has a center hole, The refrigerant flows through the refrigerant supply passage, the refrigerant chamber, the central hole, and the pipe in that order, collides with the rear surface of the tip spherical portion, turns around, flows out of the pipe, and is discharged through the refrigerant discharge passage in that order.

[0013] The invention according to claim 2 is the injection nozzle according to claim 1, The injection nozzle is characterized in that it is provided with a spanner engaging portion having a polygonal cross section, and an outlet of the coolant discharge passage is provided at this spanner engaging portion.

[0014] The invention according to claim 3 is the injection nozzle according to claim 2, The injection nozzle is characterized in that an inlet of the coolant supply passage is provided at the spanner engaging portion.

[0015] The invention according to claim 4 is the injection nozzle according to claim 2 or 3, The number of the oblong holes is the same as the number of corners of the polygon. Effect of the Invention

[0016] In the invention according to claim 1, the tip spherical portion is forcibly cooled by causing a coolant to impinge on the rear surface of the tip spherical portion from the pipes of the pipe structure. If the coolant is gently brought into contact with the surface to be cooled, the heat transfer coefficient will be small. In contrast, if the coolant is made to collide with the surface to be cooled, as in the present invention, the heat transfer coefficient will be large. As a result, the spherical tip portion is cooled effectively. Therefore, the present invention provides an injection nozzle having a structure in which the tip spherical portion corresponding to the first nozzle land is strongly cooled.

[0017] In the invention according to claim 2, the outlet of the coolant discharge passage is provided with a spanner engagement portion having a polygonal cross section. If the coolant discharge passage is to be opened with a drill, the drilling can be started by placing the drill at a right angle against one flat surface of the polygon, which makes it less likely for the drill to break and reduces processing costs.

[0018] In the invention according to claim 3, the inlet of the coolant supply passage is also provided with a spanner engaging portion having a polygonal cross section. As in claim 2, the drill is less likely to break, which reduces the processing cost.

[0019] In the invention according to claim 4, the number of the long holes is the same as the number of the corners of the polygon. That is, the injection nozzle can be uniformly cooled by the multiple pipe structure. [Brief description of the drawings]

[0020] [Figure 1] FIG. 2 is a cross-sectional view of an injection nozzle according to the present invention. [Diagram 2] FIG. [Diagram 3] FIG. [Figure 4] 4(a) is a cross-sectional view taken along line 4a-4a in FIG. 3, and (b) and (c) are reference views for explaining breakage of the drill. [Diagram 5] FIG. [Figure 6]1A is a cross-sectional view of a main portion of an injection nozzle, FIG. 1B is an enlarged view of portion b of FIG. 1A, FIG. 1C is a diagram showing a comparative example, and FIG. [Figure 7] 13(a) to 13(d) are diagrams for explaining the number of slots. [Figure 8] FIG. 11 is a perspective view of an injection nozzle according to a modified example. [Figure 9] FIG. 11 is an exploded view of an injection nozzle according to a modified example. [Figure 10] FIG. 11 is a cross-sectional view of an injection nozzle according to a modified example. [Figure 11] FIG. 1 is a diagram illustrating a basic configuration of a conventional injection nozzle. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described with reference to the accompanying drawings. EXAMPLES

[0022] [Mold, heater barrel, injection nozzle] As shown in FIG. 1, injection nozzle 10 is a nozzle that has a male threaded portion 12 on the outer periphery of its base that is screwed into heating barrel 11, a spanner engaging portion 13 in front of this male threaded portion 12, and a spherical tip portion 15 in front of this spanner engaging portion 13 that is brought into contact with mold 14, and is used to inject thermosetting resin into mold 14.

[0023] The screw 16, which is housed in the heating barrel 11 so as to be rotatable and axially movable, has a cone-shaped cone portion 17 at its tip. Since this cone portion 17 enters and exits the injection nozzle 10, the injection nozzle 10 has a multi-stage structure in which the spanner hook portion 13 has a smaller diameter than the base portion including the male thread portion 12, and the tip spherical portion 15 has a smaller diameter than this spanner hook portion 13.

[0024] Taking into consideration the characteristics of the thermosetting resin, the temperature of the injection nozzle 10 is set to 60 to 85°C, and the temperature of the mold 14 is set to 160 to 180°C. Cooling measures are taken to prevent the injection nozzle 10, particularly the tip spherical portion 15, from rising above a predetermined temperature (60 to 85° C.) due to the heat of the mold 14. The cooling structure for this purpose will be described below.

[0025] [Injection nozzle] 2, the spanner hook 13 has a hexagonal shape. A surface of the hexagon described below is one of six surfaces of a hexahedron when the hexagon is interpreted as a hexahedron. An inlet 45a for a coolant supply port is provided on one face 13a of the hexagon, and an outlet 50b for a coolant discharge passage is provided on another face 13a of the hexagon.

[0026] 1, coolant supply port inlet 45a and coolant supply port outlet 50b are provided on the outer surface (hexagonal surface) of spanner engagement portion 13 which corresponds to the outer surface of injection nozzle 10. In other words, coolant supply port inlet 45a and coolant supply port outlet 50b open on the outer surface of injection nozzle 10 at positions that do not interfere with heating barrel 11 and mold 14. The outer surface of the injection nozzle 10 is preferably a hexagonal surface, but is not limited to a hexagonal surface as long as it is a surface between the heater barrel 11 and the mold 14 .

[0027] As shown in FIG. 3, the injection nozzle 10 has a large diameter hole portion 18 whose hole diameter corresponds to the outer diameter of the screw (FIG. 1, reference numeral 16), a conical hole portion 19 corresponding to the cone portion (FIG. 1, reference numeral 17), and a nozzle hole 21 penetrating the tip spherical portion 15, and in the hatched portion in the figure (the so-called solid portion), a long hole 23, a refrigerant supply path 45, and a refrigerant discharge path 50 are provided.

[0028] More specifically, the injection nozzle 10 is provided with at least one elongated hole 23 extending from the male thread portion 12 to the vicinity of the tip spherical portion 15. The elongated hole 23 is provided along the conical hole portion 19.

[0029] [Machining long holes] An example of a method for machining the slot 23 will now be described. First, an end mill is used to countersink a portion of the male thread portion 12. This countersinking creates a seat surface 24 that is perpendicular to the longitudinal axis of the slot 23.

[0030] Next, the drill is set perpendicular to the seat surface 24 to drill large hole 25. The drill is changed and a medium hole 26 smaller in diameter than the large hole 25, a small hole 27 smaller in diameter than the medium hole 26, and a fine hole 28 smaller in diameter than the small hole 27 are successively drilled. Note that setting the drill up means moving the drill forward while rotating (the same applies below). Next, a female thread 29 is cut at the entrance of the large diameter hole 25 with a tap.

[0031] Although the thin hole 28 is not essential, the provision of the thin hole 28 allows the elongated hole 23 to extend to the vicinity of the tip spherical portion 15 . The pipe structure 30 and the plug structure 40 are inserted in this order into the elongated hole 23.

[0032] [Plug structure] In the plug structure 40, a male thread 42 is cut on the large diameter side of the reducing diameter cylinder 41, and a first O-ring 43 is fitted on the small diameter side. When the plug structure 40 is inserted into the large diameter hole 25 while being rotated, the male thread 42 is screwed into the female thread 29. At the same time, the first O-ring 43 exerts a sealing effect, preventing refrigerant leakage from the medium diameter hole 26 to the large diameter hole 25. The structure of the pipe structure 30 will be described in detail later with reference to FIG.

[0033] [Refrigerant supply path] The coolant supply passage 45 consists, for example, of a horizontal hole 46 drilled parallel to the longitudinal axis 10a of the injection nozzle 10 so that its tip reaches the medium-diameter hole 26, and a vertical hole 47 drilled from the hexagonal face 13a so as to reach this horizontal hole 46. The opening of the side hole 46 is closed with a steel plug 48. The steel plug 48 is suitably a threaded plug or a steel ball. As a result, an inlet 45a of the coolant supply passage 45 is provided on the hexagonal surface 13a, and an outlet 45b of the coolant supply passage 45 opens into the medium diameter hole .

[0034] [Refrigerant discharge path] FIG. 4(a) is a cross-sectional view taken along line 4a-4a in FIG. As shown in FIG. 4(a), a drill is drilled perpendicularly to the hexagonal surface 13a to provide a coolant discharge passage 50 from the small diameter hole 27 to the hexagonal surface 13a.

[0035] Regarding the breakage of the drill, a supplementary explanation is given using Figures 4(b) and (c). As shown in FIG. 4(b), when a drill 53 is placed upright on an inclined surface 52, a horizontal component force is applied to the drill 53, and the drill 53 breaks due to this horizontal component force. On the other hand, as shown in FIG. 4(c), if a seat 55 is formed by an end mill 54 and then a drill 53 is set perpendicular to the seat 55, the drill 53 will not break.

[0036] That is, as shown in Fig. 4(a), the vertical hole 47 of the coolant supply passage is perpendicular to the hexagonal surface 13a, and the drill can be drilled without breaking. The coolant discharge passage 50 is also perpendicular to the hexagonal surface 13a, and the drill can be drilled without breaking. The long hole 23 shown in Fig. 3 is also perpendicular to the seat surface 24, and the drill can be drilled without breaking.

[0037] [Pipe structure] As shown in Fig. 5, the pipe structure 30 is composed of a pipe 31 whose outer diameter is smaller than the diameter of the small diameter hole (Fig. 3, reference numeral 27), and a pipe support 32 that supports the base of the pipe 31. The pipe support 32 is a cylinder with a central hole 33, one end into which the pipe 31 is inserted, and the other end has a threaded portion 34 and a second O-ring 35 on the outer periphery.

[0038] The pipe 31 is preferably a copper pipe and is fixed to the pipe support 32 by brazing. The threaded portion 34 is used when removing the pipe structure 30 from the elongated hole (FIG. 3, reference numeral 23). That is, a male screw is cut at the tip of a long, thin rod, and the male screw is screwed into the threaded portion 34. The long, thin rod is pulled to remove the pipe structure 30 from the elongated hole.

[0039] In FIG. 3, when the pipe structure 30 is inserted into the long hole 23 and then the plug structure 40 is screwed in, the configuration shown in FIG. 6(a) is obtained.

[0040] [Refrigerant chamber] As shown in Fig. 6(a), the pipe structure 30 and the plug structure 40 are separated by a predetermined distance D, and this separated region becomes a refrigerant chamber 56. The outlet 45b of the refrigerant supply passage 45 is connected to this refrigerant chamber 56. The predetermined distance D is suitably in the range of 3 to 5 times the hole diameter of the outlet 45b of the refrigerant supply passage 45. Within this range, the outlet 45b will not be blocked by the pipe support 32 or the plug structure 40 even if there is a processing error.

[0041] [Flow of refrigerant] The flow of the refrigerant is indicated by a solid line with an arrow for the outgoing direction and by a dashed line with an arrow for the return direction. A coolant such as air or water is supplied to coolant supply passage 45 as shown by arrow (1). The coolant flows through vertical hole 47 and horizontal hole 46 in that order, and then flows into coolant chamber 56 as shown by arrow (2), where it is reversed.

[0042] As shown in Fig. 6(b), the refrigerant passes through pipe 31, sprays out from the tip of pipe 31, and collides with small diameter hole 28 (arrow (3)). After the collision, the flow reverses and flows outside pipe 31 (arrow (4)), and enters refrigerant discharge passage 50 shown in Fig. 6(a). Then, the refrigerant is discharged to the outside through refrigerant discharge passage 50 as shown in Fig. 4(a) (arrow (5)).

[0043] Fig. 6(c) is a diagram showing a comparative example, in which the refrigerant flows in from one end of the cooling jacket 57 as indicated by the arrow (11), and the refrigerant is discharged from the other end through a discharge path 58 (arrow (12)). As is clear from Fig. 6(a), it is not easy to provide a discharge path 58, and even if it can be provided, it must be provided at a position retreated by W from the tip of the cooling jacket 57.

[0044] As a result, the area W shown in Fig. 6(c) becomes a "liquid pool" and there is no exchange of refrigerant, or even if there is, it is very little. If there is little exchange of refrigerant, the cooling performance decreases and the tip spherical portion 15 shown in Fig. 6(a) is not cooled sufficiently. As a countermeasure, it is necessary to increase the amount of refrigerant supplied.

[0045] In contrast, in the present invention shown in Fig. 6(b), new refrigerant is constantly supplied to the small hole 28 by the collisions indicated by the arrows (3). In addition, the heat transfer coefficient increases due to the collisions. As a result, the tip spherical portion 15 shown in Fig. 6(a) is sufficiently cooled with a small amount of refrigerant. Therefore, the present invention provides an injection nozzle 10 having a structure in which the tip spherical portion 15 is strongly cooled.

[0046] In Fig. 6(a), pressure is applied to the pipe support 32 from the refrigerant chamber 56 side toward the left in the figure, and pressure is applied to the pipe support 32 from the small diameter hole 27 side toward the right in the figure. Pressure loss occurs inside the pipe 31 due to the flow of arrow (3). As a result, the pressure to the left in the figure is higher than the pressure to the right in the figure, so the pipe support 32 does not slip out to the refrigerant chamber 56 side. For this reason, a fitting structure using the second O-ring 35 is adopted.

[0047] However, this fitting structure may be changed to a screw-connecting structure. The screw-connecting structure has the advantage of being able to mechanically prevent the pipe support 32 from moving, but has the disadvantage of needing to form a female thread in the recessed medium-diameter hole 26, which increases the processing cost. In contrast, the fitting structure has the advantage that it is not necessary to form a female thread in the medium diameter hole 26, and therefore the processing costs are not increased. Therefore, it is optional whether the pipe support 32 is fixed by fitting or by screw connection.

[0048] Also, as shown in FIG. 6(d), the tip of the pipe 31 may be inserted into the small diameter hole 28 by slightly increasing the hole diameter of the small diameter hole 28 and / or slightly decreasing the outer diameter of the pipe 31.

[0049] In the embodiment shown in Fig. 6(b), the hole diameter of the small hole 28 can be made smaller than the outer diameter of the pipe 31. As is clear from Fig. 6(a), the smaller the hole diameter of the small hole 28, the thinner the wall can be drilled, and the tip of the small hole 28 can be brought closer to the tip spherical portion 15. Therefore, in the embodiment shown in FIG. 6( b ), the hole diameter of the small hole 28 can be larger than the outer diameter of the pipe 31 , but is preferably smaller than the outer diameter of the pipe 31 .

[0050] In contrast, in the embodiment shown in FIG. 6(d), the hole diameter of the small hole 28 is larger than the outer diameter of the pipe 31, but the tip of the pipe 31 can be inserted into the small hole 28, so that the refrigerant can be sent to the small hole 28 more reliably than in FIG. 6(b). Therefore, it is up to the discretion of the user to decide whether to adopt FIG. 6(b) or FIG. 6(d).

[0051] Number of slots A preferred number of elongated holes 23 to be provided in the injection nozzle will be described with reference to FIG. As shown in FIG. 7(a), two long holes 23 are provided, one on the top and one on the bottom. Alternatively, as shown in FIG. 7(b), a total of three oblong holes 23 are provided at a pitch of 120°.

[0052] Alternatively, as shown in FIG. 7(c), a total of six oblong holes 23 are provided at 60° pitches. Alternatively, as shown in FIG. 7(d), only one slot 23 may be provided. Therefore, it is sufficient to provide at least one long hole 23. However, the structure shown in Fig. 7(c) is ideal, although it increases the processing cost and makes the structure complicated.

[0053] In this embodiment, the spanner hook portion 13 has a hexagonal cross section, but it may have any polygonal cross section such as a square or octagonal cross section, and the number of corners is not specified. In the case of a rectangular cross section, it is recommended that a total of four oblong holes 23 be provided at 90° pitches, and in the case of an octagonal cross section, a total of eight oblong holes 23 be provided at 45° pitches. In other words, it is desirable to provide the same number of slots 23 as the number of corners of the polygon.

[0054] [Example of change] Next, a modified example of the present invention will be described with reference to Figures 8 to 10. However, in this modified example, the same elements as those in Figures 1 to 6 will be designated by the same reference numerals and detailed description thereof will be omitted. As shown in FIG. 8, the injection nozzle 10 according to the modified example has an extension 59 interposed between the male thread portion 12 and the spanner engaging portion 13, and this extension 59 is provided with an inlet 45a of the coolant supply passage.

[0055] As shown in Figure 9, the injection nozzle 10 has at least one long hole 23 extending from the male threaded portion 12 to near the tip spherical portion 15, and the structure remains the same, in which the pipe structure 30 and the plug structure 40 are inserted into this long hole 23 in this order.

[0056] The coolant supply passage 45 provided in the extension 59 consists of only a very short vertical hole 47 . In addition, the refrigerant discharge passage 50 provided in the spanner engaging portion 13 also consists of only a very short vertical hole. That is, the side hole 46 shown in FIG. 3 is not necessary, and the long refrigerant discharge path 50 shown in FIG. 4(a) becomes extremely short.

[0057] Therefore, although the injection nozzle 10 becomes slightly larger in the modified example by providing the extension portion 59, it is possible to reduce the processing costs of the coolant supply path 45 and the coolant discharge path 50. In addition, since the coolant supply path 45 and the coolant discharge path 50 are very short, there is an advantage that they are less likely to become clogged with foreign matter, and even if they do, the foreign matter can be easily removed.

[0058] As shown in FIG. 10, the injection nozzle 10 can be obtained by inserting the pipe structure 30 into the long hole 23 and then screwing in the plug structure 40. The refrigerant passes through the refrigerant supply passage 45, changes direction in the refrigerant chamber 56, passes through the inside of the pipe 31, and collides with the small diameter hole 28. This collision strongly cools the tip spherical portion 15. The warmed refrigerant flows outside the pipe 31 and passes through the refrigerant discharge passage 50 to be discharged to the outside.

[0059] In the present invention, the long hole 23 is a multi-stage hole consisting of a large diameter hole 25, a medium diameter hole 26, a small diameter hole 27, and a thin diameter hole 28, but the number of stages of the multi-stage hole may be changed, provided that the pipe structure 30 can be inserted and the plug structure 40 can be screwed in. [Industrial Applicability]

[0060] The injection nozzle of the present invention is suitable for injecting thermosetting resins. [Explanation of symbols]

[0061] 10...injection nozzle, 10a...longitudinal axis of injection nozzle, 11...heating barrel, 12...male threaded portion, 13...spanner hook portion, 13a...outer surface of injection nozzle (hexagonal surface), 14...mold, 15...tip spherical portion, 23...long hole, 30...pipe structure, 31...pipe, 32...pipe support, 40...plug structure, 45...refrigerant supply path, 45a...inlet of refrigerant supply path, 50...refrigerant discharge path, 50b...outlet of refrigerant discharge path, 56...refrigerant chamber, D...predetermined distance (distance between plug structure and pipe structure).

Claims

1. An injection nozzle for injecting a thermosetting resin, the injection nozzle having a male threaded portion that is screwed into a heating barrel and a spherical tip portion that is brought into contact with a mold, the injection nozzle is provided with at least one elongated hole extending from the male thread portion to the vicinity of the tip spherical portion, a refrigerant supply passage is provided from the outer surface of the injection nozzle to the elongated hole for supplying a refrigerant, and a refrigerant discharge passage is provided from the elongated hole to the outer surface of the injection nozzle for discharging the warmed refrigerant, A pipe structure is inserted into the long hole toward the tip spherical portion, and a plug structure is inserted into the male thread portion, The plug structure and the pipe structure are spaced apart by a predetermined distance to form a coolant chamber, and the coolant supply passage is connected to the coolant chamber. The pipe structure includes a pipe having a diameter smaller than the diameter of the long hole, and a pipe support that supports a base of the pipe, has an outer diameter corresponding to the diameter of the long hole, and has a center hole, the coolant flows through the coolant supply passage, the coolant chamber, the central hole, and the pipe in that order, collides with the rear surface of the tip spherical portion, turns around, flows out of the pipe, and is discharged through the coolant discharge passage in that order.

2. 2. The injection nozzle of claim 1, The injection nozzle is characterized in that it is provided with a spanner engaging portion having a polygonal cross section, and an outlet of the coolant discharge passage is provided at this spanner engaging portion.

3. 3. The injection nozzle according to claim 2, The injection nozzle is characterized in that an inlet of the coolant supply passage is provided at the spanner engaging portion.

4. The injection nozzle according to claim 2 or 3, The injection nozzle is characterized in that the number of the oblong holes is the same as the number of corners of the polygon.

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