Shut-off nozzle, and injection molding machine

Abstract

To provide a shut-off nozzle that prevents injection material from leaking.SOLUTION: A shut-off nozzle (5) includes: a nozzle (25); and a needle valve (26) inserted into a slanted hole (33) formed in the nozzle (25). The needle valve (26) has a hemispherical head (38) formed at a tip of a cylindrical shaft part (37). The slanted hole (33) is drilled deep across a nozzle inner channel (31) to form a recess (40) on an inner peripheral surface of the nozzle inner channel (31). The recess (40) is formed from a linear hole (41) and a spherical hole (42) with a constant diameter, so that the shaft part (37) of the needle valve (26) is housed in the linear hole (41) and the head (38) is housed in the spherical hole (42). A length L of the linear hole (41) is made to be 0.25d≤L≤0.7d with respect to a diameter d of the shaft part (37) of the needle valve.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a shut-off nozzle provided in an injection molding machine, and to an injection molding machine provided with a shut-off nozzle. [Background technology]

[0002] The shut-off nozzle provided in the injection device of the injection molding machine is designed to open and close the flow path of the injection nozzle through which the injection material flows, thereby preventing so-called dripping. There are various types of shut-off nozzles, and for example, as described in Patent Document 1, there is a shut-off nozzle consisting of a nozzle and a needle valve provided at an angle to the nozzle. In this type of shut-off nozzle, an oblique hole is opened from the outer circumferential surface of the nozzle to the injection flow path inside the nozzle, and the needle valve is inserted into this hole so as to be freely movable forward and backward. When the needle valve is advanced, the injection flow path is closed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 3-274125 Summary of the Invention [Problem to be solved by the invention]

[0004] The shut-off nozzle described in Patent Document 1 has a needle valve composed of a cylindrical shaft and a hemispherical head formed at the tip of the shaft. This needle valve is designed to close the injection flow path inside the nozzle, but there is a problem in that a small amount of injection material leaks due to machining errors in the hole.

[0005] The present disclosure provides a shut-off nozzle that is less susceptible to leakage of injected material, a method for manufacturing such a shut-off nozzle, and an injection molding machine.

[0006] Other objects and novel features will become apparent from the description of this specification and the accompanying drawings. [Means for solving the problem]

[0007] The present disclosure is directed to a shut-off nozzle that includes a nozzle in which an internal flow passage through which an injection material passes is formed in the injection direction, and a needle valve that is inserted so as to be able to move forward and backward in an oblique hole that reaches the internal flow passage from the outer circumferential surface of the nozzle. The needle valve has a semispherical head formed at the tip of a cylindrical shaft. The oblique hole is opened deeply across the internal flow passage of the nozzle so that a recess is formed on the inner circumferential surface of the internal flow passage of the nozzle. This recess is, By reaming The needle valve is formed from a linear hole formed in a straight line with a constant diameter and a spherical hole formed in a spherical shape next to the linear hole, and when the shaft part of the needle valve is stored in the linear hole and the head part is stored in the spherical hole, an annular mechanical seal part is formed by the linear hole and the shaft part. In the present disclosure, the linear hole has a length L of: 0.25d≦L≦0.7d and the difference between its inside diameter and the diameter of the shaft portion of the needle valve is 0.016 mm or less. Effect of the Invention

[0008] The present disclosure can prevent leakage of ejected material at shut-off nozzles. [Brief description of the drawings]

[0009] [Figure 1] 1 is a front view showing an injection molding machine according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a front cross-sectional view showing a shut-off nozzle and a part of an injection device according to the present embodiment. [Diagram 3] 1 is a front cross-sectional view showing a portion of a shut-off nozzle according to an embodiment of the present invention. [Figure 4] 1 is a front cross-sectional view showing a portion of a shut-off nozzle according to an embodiment of the present invention. [Diagram 5]FIG. 1 is a front cross-sectional view showing a portion of a conventional shut-off nozzle. [Figure 6A] FIG. 13 is a front cross-sectional view illustrating the nozzle during processing, illustrating the method for processing the shut-off nozzle according to the present embodiment. [Figure 6B] FIG. 13 is a front cross-sectional view illustrating the nozzle during processing, illustrating the method for processing the shut-off nozzle according to the present embodiment. [Figure 6C] FIG. 13 is a front cross-sectional view illustrating the nozzle during processing, illustrating the method for processing the shut-off nozzle according to the present embodiment. [Figure 6D] FIG. 13 is a front cross-sectional view illustrating the nozzle after machining has been completed, illustrating the method for machining the shut-off nozzle according to the present embodiment. [Figure 7] 1 is a front cross-sectional view showing a portion of a shut-off nozzle according to an embodiment of the present invention. [Figure 8] 1 is a graph showing the relationship between the ratio of the length of a mechanical seal portion to the diameter of a needle valve in a shut-off nozzle and the amount of leakage from the shut-off nozzle. [Figure 9] 1 is a graph showing the relationship between the difference between the diameter of a mechanical seal portion and the diameter of a needle valve in a shut-off nozzle, and the amount of leakage from the shut-off nozzle. [Figure 10] FIG. 13 is a front cross-sectional view illustrating a part of the shut-off nozzle according to the present embodiment, illustrating an experimental method. [Figure 11] 11 is a front cross-sectional view showing a part of a shut-off nozzle according to a second embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Specific embodiments will be described in detail below with reference to the drawings. However, the present invention is not limited to the following embodiments. In order to clarify the description, the following description and drawings are appropriately simplified. In each drawing, the same elements are given the same reference numerals, and duplicated descriptions are omitted as necessary. In addition, hatching is omitted in some parts to avoid cluttering the drawings.

[0011] The present embodiment will be described. <Injection molding machine> 1, an injection molding machine 1 according to this embodiment includes a toggle-type mold clamping device 2 and an injection device 3. The injection device 3 according to this embodiment is provided with a shut-off nozzle 5 according to this embodiment, which will be described in detail later.

[0012] <Mold clamping device> The mold clamping device 2 includes a fixed platen 7 fixed to a bed B, a movable platen 8 slidably provided on the bed B, and a mold clamping housing 9. The fixed platen 7 and the mold clamping housing 9 are connected by a plurality of tie bars 11, 11, ..., and the movable platen 8 is slidable between the fixed platen 7 and the mold clamping housing 9. A mold clamping mechanism, which is a toggle mechanism 13 in this embodiment, is provided between the mold clamping housing 9 and the movable platen 8. A fixed side mold 15 and a movable side mold 16 are provided on the fixed platen 7 and the movable platen 8, respectively. Therefore, when the toggle mechanism 13 is driven, the molds 15 and 16 are opened and closed.

[0013] <Injection device> The injection device 3 includes a heating cylinder 19, a screw 20 provided in the heating cylinder 19, and a screw drive device 22. The heating cylinder 19 is supported by the screw drive device 22, and the screw 20 is driven in the rotational direction and the axial direction by the screw drive device 22. The heating cylinder 19 is provided with a hopper 23 and a shut-off nozzle 5 according to the present embodiment described below. When the injection material is supplied from the hopper 23 and the heating cylinder 19 is heated and the screw 20 is rotated by the screw drive device 22, the injection material is melted and measured. When the screw 20 is driven in the axial direction by the screw drive device 22, the injection material can be injected into the molds 15, 16.

[0014] <Shut-off nozzle according to this embodiment> 2, the shut-off nozzle 5 according to this embodiment includes a nozzle 25, a needle valve 26, and a drive mechanism 28 that drives the needle valve 26. The nozzle 25 is provided to the heating cylinder 19 via an adapter 30. That is, the heating cylinder 19 is provided with the adapter 30, and the nozzle 25 is provided to this adapter 30.

[0015] The nozzle 25 has a flow path through which the injection material flows, i.e., an internal nozzle flow path 31, provided at the axis of the nozzle 25. This internal nozzle flow path 31 opens at the tip of the nozzle 25. Such a nozzle 25 has an oblique hole 33 that extends from its outer circumferential surface to the internal nozzle flow path 31. This oblique hole 33 has a characteristic shape in this embodiment, which will be described later. A needle valve 26 is inserted in this oblique hole 33.

[0016] The driving mechanism 28 is composed of a piston-cylinder unit. The driving mechanism 28 is fixed to a fixed part 35 fixed to the heating cylinder 19, and drives the needle valve 26 in the axial direction.

[0017] 3 and 4 show enlarged views of the tip portion of the nozzle 25 and the tip portion of the needle valve 26. Fig. 3 shows a state in which the intra-nozzle flow path 31 is closed by the needle valve 26, and Fig. 4 shows a state in which the needle valve 26 is retracted to open the intra-nozzle flow path 31. As shown in Figs. 3 and 4, the needle valve 26 has a cylindrical shaft portion 37 and a hemispherical head portion 38 provided at the tip of the shaft portion 37.

[0018] As described above, the oblique hole 33 is opened so as to reach the inner-nozzle flow passage 31 from the outer circumferential surface of the nozzle 25. However, in this embodiment, the oblique hole 33 is opened deeper across the inner-nozzle flow passage 31 after reaching the inner-nozzle flow passage 31. Therefore, a recess 40 is formed on the opposite side of the inner circumferential surface of the inner-nozzle flow passage 31. In this embodiment, the recess 40 is composed of a linear hole 41 formed in a straight line with a constant diameter, and a spherical hole 42 formed next to the linear hole 41. The needle valve 26 is arranged so that a part of its shaft portion 37 is housed in the linear hole 41, and the head portion 38 is housed in the spherical hole 42.

[0019] However, it is difficult to machine the spherical hole 42 into a perfect hemisphere. Although the gap is exaggerated and drawn larger than it actually is in FIG. 3, even when the head 38 of the needle valve 26 is housed in the spherical hole 42, a small gap 44 is formed. In other words, the injection material in the nozzle inner flow path 31 may leak. In contrast, the linear hole 41 and the shaft portion 37 of the needle valve 26 are sealed over the length L of the linear hole 41, although there is a small gap between them. In other words, the linear hole 41 and the shaft portion 37 inserted into this linear hole 41 form an annular mechanical seal portion 46. This mechanical seal portion 46 can prevent leakage of the injection material. Note that there are preferable conditions for the mechanical seal portion 46 to reliably prevent leakage of the injection material. The conditions will be explained later.

[0020] <Conventional shut-off nozzle> 5 shows a nozzle 101 and a needle valve 102, which are parts of a conventional shut-off nozzle 100. Conventional nozzle 101 also has an oblique hole 105 that extends from its outer circumferential surface to an internal nozzle flow path 104. However, a recess 107 formed on the opposite side of the inner circumferential surface of internal nozzle flow path 104 by oblique hole 105 across internal nozzle flow path 104 is only a substantially hemispherical spherical hole 108.

[0021] The needle valve 102 provided in the conventional shut-off nozzle 100 also has a cylindrical shaft portion 110 and a semispherical head portion 111. Therefore, when the needle valve 102 is advanced, the head portion 111 is accommodated in the spherical hole 108, and the nozzle internal flow passage 104 is closed. However, a small gap 112 is formed between the spherical hole 108 and the head portion 111. Therefore, there is a problem in that a small amount of injected material leaks, as shown by the arrow in FIG. 5.

[0022] <Method of machining nozzle according to this embodiment> A method for machining an oblique hole 33 (see Figs. 3 and 4) in a nozzle 25 according to this embodiment will be described with reference to Figs. 6A to 6D. An intra-nozzle flow path 31 is first opened in the nozzle 25. In such a nozzle 25, an oblique pilot hole 50 as shown in Fig. 6A is opened using a drill or the like. The inner diameter of the pilot hole 50 is made slightly smaller than the inner diameter of the oblique hole 33 (see Figs. 3 and 4) to be formed. As shown in Fig. 6A, a reamer 51 is pressed down on the pilot hole 50 while rotating. That is, the oblique hole 33 is formed by the reamer 51.

[0023] As the cutting of the oblique hole 33 by the reamer 51 progresses, the tip of the reamer 51 comes into contact with the inner circumferential surface of the intra-nozzle flow path 31, as shown in Fig. 6B. In the machining of the nozzle 101 of the conventional shut-off nozzle 100 (see Fig. 5), the machining by the reamer 51 ends at this point. However, in this embodiment, the hole is opened deeper by the reamer 51. That is, as shown in Fig. 6C, the reamer 51 is driven in by the length L. This forms the linear hole 41.

[0024] After the linear hole 41 is formed, the reamer 51 is withdrawn. Then, as shown in Fig. 6D, the spherical hole 42 is machined. Machining of the nozzle 25 is completed.

[0025] <Conditions for mechanical seal> The shut-off nozzle 5 (see FIG. 2) according to this embodiment is provided with a mechanical seal portion 46 (see FIG. 3), which can prevent leakage of the injection material from the nozzle internal flow path 31. The behavior of the injection material at the mechanical seal portion 46 will be considered with reference to FIG. 7.

[0026] In the mechanical seal portion 46, the flow of the injection material between the straight hole 41 and the shaft portion 37 of the needle valve 26 is a laminar flow because the gap h is very small, and can be treated as a so-called Poiseuille flow, which is a flow between parallel plates. In the Poiseuille flow, when a pressure difference ΔP occurs between the nozzle inner flow path 31 and the gap 44, the velocity v of the injection material flowing through the gap h has a parabolic velocity distribution. The flow rate Q of the injection material flowing through the mechanical seal portion 46 is given by the following formula 1 from the diameter d of the shaft portion 37, the inner diameter D of the straight hole 41, the length L of the straight hole 41, and the viscosity coefficient η of the injection material. Note that the gap h is set to 1 / 2 of the difference between the inner diameter D of the straight hole 41 and the diameter d of the shaft portion 37.

[0027]

number

[0028] Based on formula 1, the conditions required for the mechanical seal portion 46 are examined. In examining the conditions, some numerical values ​​are first determined as follows: the diameter d of the shaft portion 37 of the needle valve 26 is 6.88 mm, the difference between the inner diameter D of the linear hole 41 and the diameter d of the shaft portion 37, i.e., the gap h, is 0.015 mm, and the viscosity coefficient η of the injected material is 1.5×10 -6 m 2 / s, the pressure difference ΔP of the injected material is 1N / m 2 These are relatively common values ​​for shut-off nozzles. Using these values, the flow rate Q of the injection material when the length L of the straight hole 41 is changed is calculated by Equation 1, and the results are summarized in the graph of FIG. 8. In this graph, the vertical axis represents the flow rate Q (ml / s), and the horizontal axis represents the ratio of the length L of the straight hole 41 to the diameter d of the shaft portion 37 (i.e., L / d).

[0029] It can be seen that the flow rate Q decreases as the ratio of the length L of the linear hole 41 to the diameter d of the shaft portion 37 increases. In other words, it can be seen that the leakage decreases. Incidentally, it is known that the amount of one drop of injection material is 0.035 to 0.055 ml. Therefore, the condition required for the mechanical seal portion 46 can be set to be that the injection material leaking per minute is less than one drop. However, a stricter condition is set in consideration of the error due to processing. In other words, the leakage per minute is set to be 0.5 drops or less. To satisfy this condition, the flow rate Q must be 0.003 ml / s or less. From this, it can be seen that the length L of the linear hole 41 must satisfy the following condition with respect to the diameter d of the shaft portion 37. 0.25d≦L

[0030] However, if the length L of the linear hole 41 is made too long, the thickness of the tip of the nozzle 25 (see FIGS. 3 and 4) becomes thin. In other words, the length L is limited by the shape of the nozzle 25. Therefore, the present inventors have determined the following condition. L≦0.7d In summary, the length L of the linear hole 41 with respect to the diameter d of the shaft portion 37 must be within the following range. 0.25d≦L≦0.7d

[0031] Next, the condition required for the difference between the inner diameter D of the straight hole 41 and the diameter d of the shaft portion 37, that is, the gap h×2, is considered. Here, assuming that the length L of the straight hole 41 is L=0.3d with respect to the diameter d of the shaft portion 37, the flow rate Q was calculated by changing the difference between the inner diameter D and the diameter d using Equation 1. This is shown in the graph of FIG. 9. In this graph, the vertical axis is the flow rate Q (ml / s), and the horizontal axis is the difference between the diameter D of the straight hole 41 in the mechanical seal portion 46 and the diameter d of the shaft portion 37 of the needle valve 26 (i.e., Dd (mm)). As mentioned above, in order to keep the leakage of the injection material to 0.5 drops or less per minute, the flow rate Q must be 0.003 ml / s or less. Then, it can be seen from the graph that the difference between the inner diameter D of the straight hole 41 and the diameter d of the shaft portion 37 should be 0.016 mm or less.

[0032] <Experiment> Nozzle 25 was prototyped under various conditions and experiments were carried out to check for leakage. "Experimental method" The following three nozzles, A, B, and C, were prototyped. Nozzle A: When forming the oblique hole 33 (see Figs. 3 and 4), the linear hole 41 was not formed in the recess 40, and only the spherical hole 42 was formed. That is, it was formed in the same manner as the conventional nozzle 101 (see Fig. 5). Nozzle B: When forming the oblique hole 33 (see Figs. 3 and 4), the linear hole 41 in the recess 40 was formed so that the length L was 0.2 mm. That is, L = 0.029d. Nozzle C: When forming the oblique hole 33 (see Figs. 3 and 4), the linear hole 41 in the recess 40 was formed so that the length L was 2.0 mm. That is, L = 0.29d. In both nozzles B and C, the difference between the inner diameter D of the linear hole 41 and the diameter d of the shaft portion 37 of the needle valve 26 was set to 0.015 mm.

[0033] As shown in Fig. 10, needle valves 26 were inserted into nozzles A to C, and kerosene was poured into the flow passage 31 in the nozzles while nozzles A to C were held vertically to check whether or not the kerosene leaked. The height 55 of the kerosene liquid surface was set to 13 cm. This height was determined based on the specific gravity of kerosene being 0.8 and the gravitational acceleration being 9.8 m / s 2 The pressure ΔP acting on the kerosene is about 1N / m 2 The reason why kerosene was used is that its viscosity coefficient η is almost equal to the viscosity coefficient of the molten resin.

[0034] In this experiment, leakage was observed at one drop every 0.56 seconds from nozzle A, and one drop every 1.0 second from nozzle B. In contrast, leakage from nozzle C was only one drop every 180 seconds. In other words, leakage of kerosene was only 1 / 3 of a drop per minute. Nozzle C satisfies the conditions required for the mechanical seal portion 46 described above (see Figures 3 and 4). In other words, it was confirmed that if the above conditions for the mechanical seal portion 46 are met, leakage will not occur substantially, or will be unlikely to occur.

[0035] <Shut-off nozzle according to the second embodiment> The shut-off nozzle 5 according to this embodiment has been described with reference to Fig. 3 as having an annular mechanical seal portion 46. However, the length L of this annular ring is not constant around the shaft portion 37. This is because, as shown by an extension line 57 of the intra-nozzle flow path 31 in Fig. 3, a part of the mechanical seal portion 46 is located below the intra-nozzle flow path 31. As a result, the apparent length of the annular ring of the mechanical seal portion 46 is longer at the location indicated by reference numeral 58. This is because the shaft portion 37 of the needle valve 26 is completely housed in the oblique hole 33, and is outside the intra-nozzle flow path 31.

[0036] In contrast, FIG. 11 shows a nozzle 25' of a shut-off nozzle 5' according to a modified second embodiment. In this nozzle 25', the mechanical seal portion 46 is entirely above the extension line 57 of the nozzle inner flow path 31. In this embodiment, the length L of the ring of the mechanical seal portion 46 is constant. In this way, the length L of the ring of the mechanical seal portion 46 may be constant around the shaft portion 37, or may not be constant as in the first embodiment. However, the length L of the ring of the mechanical seal portion 46 around the shaft portion 37 is never shorter than the length L. Therefore, the sealing performance is not impaired.

[0037] Although the invention made by the present inventor has been specifically described above based on the embodiment, it goes without saying that the present invention is not limited to the embodiment already described, and various modifications are possible without departing from the gist of the invention. The above-described examples may be implemented in appropriate combination. [Explanation of symbols]

[0038] 1 Injection molding machine 2 Mold clamping device 3 Injection unit 5 Shut-off nozzle 7 Fixed plate 8 Movable plate 9 Clamping housing 11 Tie bar 13 Toggle mechanism 15 Fixed side mold 16 Movable mold 19 Heating cylinder 20 Screw 22 Screw drive device 23 Hopper 25 Nozzle 26 Needle valve 28 Drive mechanism 30 Adapter 31 Nozzle inner flow passage 33 Oblique hole 37 Shaft 38 Head 40 Recess 41 Straight hole 42 Spherical hole 44 Gap 46 Mechanical seal part 50 Pilot hole 51 Reamer 55 Liquid level

Claims

1. a nozzle having an internal flow passage through which the injection material passes, the internal flow passage being formed in the injection direction; a needle valve inserted in an oblique hole extending from an outer circumferential surface of the nozzle to the nozzle internal flow passage so as to be movable back and forth; The needle valve opens and closes the nozzle internal flow path, The needle valve has a cylindrical shaft portion and a semi-spherical head portion at the tip thereof. the oblique hole is bored deeply across the nozzle inner flow passage so as to form a recess on an inner circumferential surface of the nozzle inner flow passage, the recess is formed of a linear hole formed linearly with a constant diameter by reaming, and a spherical hole formed spherically continuous from the linear hole, and when the shaft portion of the needle valve is accommodated in the linear hole and the head portion is accommodated in the spherical hole, an annular mechanical seal portion is formed by the linear hole and the shaft portion, The linear hole has a length L relative to a diameter d of the shaft portion of the needle valve. 0.25d≦L≦0.7d and the difference between the inner diameter of the shut-off nozzle and the diameter of the shaft portion of the needle valve is 0.016 mm or less.

2. an injection device for injecting an injection material; A mold clamping device that clamps a mold, The injection device is provided with a shut-off nozzle, The shut-off nozzle includes a nozzle having an internal flow path through which the injection material passes in the injection direction; a needle valve inserted in an oblique hole extending from an outer circumferential surface of the nozzle to the nozzle internal flow passage so as to be movable back and forth; The needle valve opens and closes the nozzle internal flow path, The needle valve has a cylindrical shaft portion and a semi-spherical head portion at the tip thereof. the oblique hole is bored deeply across the nozzle inner flow passage so as to form a recess on an inner circumferential surface of the nozzle inner flow passage, the recess is formed of a linear hole formed linearly with a constant diameter by reaming, and a spherical hole formed spherically continuous from the linear hole, and when the shaft portion of the needle valve is accommodated in the linear hole and the head portion is accommodated in the spherical hole, an annular mechanical seal portion is formed by the linear hole and the shaft portion, The linear hole has a length L relative to a diameter d of the shaft portion of the needle valve. 0.25d≦L≦0.7d and the difference between the inner diameter of the needle valve and the diameter of the shaft portion of the needle valve is 0.016 mm or less.

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