JP7158429B2 - discharge unit - Google Patents

Description

The present invention relates to a discharge unit for an injection molding machine.

2. Description of the Related Art Conventionally, injection molding has been performed in which a molten material is injected into a mold cavity to form a molded product. 2. Description of the Related Art In injection molding, a discharge unit is used to discharge a molten material into a mold cavity.

As one of the above-mentioned injection molding methods, for example, a hot runner discharge unit is known, which maintains the material in the material passage in a molten state by heating the material passage up to the gate (entrance) of the cavity. (For example, Patent Document 1).

According to the hot runner discharge unit described above, only the material in the portion (inside the cavity) that will be the molded product is cured, and the other portions are not cured. Therefore, since no extra portion (also called a runner) remains in the molded product, there is no need to remove the extra portion in the post-molding process. Therefore, injection molding using the hot runner system is said to have the advantage of reducing processing costs and material costs after molding.

Japanese Patent Application Laid-Open No. 2019-64000

By the way, in injection molding, a discharge unit is provided for heating the material passage. The discharge unit is provided downstream of the material passage with a nozzle for discharging the molten material toward the gate of the mold cavity. A valve pin is inserted inside the nozzle, and the ejection port of the nozzle is opened and closed by advancing and retracting the valve pin. In addition, the discharge port of the nozzle is formed to have a small diameter by narrowing the tip so as to force-feed a predetermined amount of molten material into the cavity.

However, since the diameter of the tip of the nozzle is narrowed down as described above, there is a problem that a large frictional resistance is generated when the molten material flows through the nozzle. Therefore, there is a problem that the pressure loss in the nozzle increases and the flow velocity of the molten material cannot be controlled with high accuracy. In addition, the aforementioned frictional resistance reduces the flow velocity of the molten material and accelerates the solidification of the molten material. Therefore, insufficient supply of the molten material into the cavity occurs, which causes variations in the quality of the molded product.

Moreover, due to the frictional resistance described above, frictional heat is generated in the nozzle due to the shearing force, and there is a problem that temperature control of the nozzle varies. Further, the inner wall of the material passage of the discharge unit and the valve pin are finished by a grinder or the like. However, since the machining accuracy is rough, there is a problem that solidified material residue enters and remains in the irregularities of the inner wall of the material passage and the surface of the valve pin. As a result, the remaining material scraps peel off and enter the cavity, causing molding defects. In addition, when the material is changed, the material used in the past becomes a cause of contamination with the new molten material.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a discharge unit capable of stabilizing the discharge amount of molten material by reducing the frictional resistance in the material passage. Another object of the present invention is to provide a discharge unit capable of improving the quality of molded products by stabilizing the discharge amount of molten material.

(1) A discharge unit of the present invention provided to solve the above-described problems is a discharge unit that discharges a molten material used for resin molding, and includes a material passage through which the molten material passes and a material passage that passes through the material passage. and a valve pin that is inserted into the material passage and moves toward and away from the discharge port to open and close the discharge port, wherein the material passage Either one or both of the inner wall of the valve pin and the outer peripheral surface of the valve pin are subjected to dimple processing or oil-repellent processing, or both.

In the discharge unit of the present invention, either one or both of the inner wall of the material passage through which the molten material passes and the outer peripheral surface of the valve pin is subjected to dimple processing or oil-repellent processing, or both. there is Here, when dimple processing is adopted, the contact area between the molten material and the inner wall of the material passage or the outer peripheral surface of the valve pin is reduced by the unevenness of the dimples. resistance is reduced. In addition, when oil-repellent treatment is applied, the contact area between the molten material and the inner wall of the material passage or the outer peripheral surface of the valve pin is reduced due to the oil-repellent effect. Frictional resistance is reduced. In addition, since the inner wall of the material passage and the outer peripheral surface of the valve pin are covered with the oil-repellent treatment, the depth of irregularities on these surfaces is reduced.

Therefore, by applying dimple processing or oil-repellent processing to the inner wall of the material passage and the outer peripheral surface of the valve pin, it is possible to suppress the decrease in the flow velocity of the molten material when it passes through the material passage. Accuracy can be improved. Therefore, the supply of the molten material into the cavity can be stabilized, and the quality of the molded product can be improved.

In addition, as described above, the inner wall of the material passage and the outer peripheral surface of the valve pin are dimpled or oil-repellent to suppress heat generation due to frictional heat generated when the molten material passes through the material passage. can be done. As a result, variations in temperature control at the ejection port can be suppressed. In addition, it is possible to suppress the solidified material pieces from remaining on the inner wall of the material passage and the surface of the valve pin. Therefore, it is possible to prevent the material pieces from entering the cavity and causing molding defects. In addition, when the material is changed, it is possible to prevent the previously used material from being mixed with the new molten material. Therefore, the quality of molded products can be improved.

In addition, when the inner wall of the material passage and the outer peripheral surface of the valve pin are subjected to oil repelling treatment, the inner wall of the material passage and the outer peripheral surface of the valve pin are covered, so the depth of unevenness on these surfaces is reduced. Play. As a result, it is possible to suppress a decrease in the flow velocity of the molten material when it passes through the material passage, and to improve the accuracy of velocity control of the molten material. Therefore, the supply of the molten material into the cavity can be stabilized, and the quality of the molded product can be improved. Furthermore, the oil-repellent action can be expected to suppress the adhesion of the molten material to the inner wall of the material passage or the surface of the valve pin. As a result, it is possible to expect the effect of suppressing the occurrence of molding defects due to contamination of the molded product with residual residue of the molten material. It should be noted that both dimple processing and oil-repellent processing may be applied. As a result, a synergistic effect can be expected from the dimple processing and the oil-repellent processing.

Moreover, dimple processing and oil-repellent processing are preferably applied to both the inner wall of the material passage and the outer peripheral surface of the valve pin. This can be expected to further reduce the frictional resistance when the molten material passes through the material passage. Further, dimple processing and oil-repellent processing are preferably applied to the inner wall of the material passage and the entire outer peripheral surface of the valve pin. As a result, it can be expected that the molten material can be discharged more stably.

(2) In the discharge unit of the present invention, which is provided to solve the above-mentioned problems, the dimple processing is performed by shot blasting, rolling or etching, and the inner wall of the material passage or the outer periphery of the valve pin is formed. It is characterized in that unevenness of 20 to 30 μm is formed on one or both of the surfaces.

According to such a configuration, since the dimple processing is performed by shot blasting, rolling or etching, the dimple processing can be easily performed. In addition, the contact area between the molten material and the material passage is appropriately reduced by setting the unevenness by dimple processing to 20 to 30 μm. Therefore, the molten material does not clog the irregularities on the surface of the material passage, and moreover, it is possible to prevent the molten material from adhering to the inner wall of the material passage and the outer peripheral surface of the valve pin. As a result, it is possible to prevent solidified pieces of material from remaining on the inner wall of the material passage and the surface of the valve pin. Therefore, the quality of molded products can be improved.

(3) The ejection unit of the present invention provided to solve the above-described problems is characterized in that the oil-repellent treatment is fluororesin treatment.

According to this configuration, since the oil-repellent treatment is a fluororesin treatment, it has heat resistance and oil repellency against the molten material. Therefore, it is possible to prevent the oil-repellent treatment from coming off due to heat. In addition, the oil repellency of the fluororesin can prevent the flow rate of the molten material from decreasing and the molten material from remaining in the material passage or on the surface of the valve pin. Therefore, the quality of molded products can be improved.

ADVANTAGE OF THE INVENTION According to this invention, the discharge unit which can stabilize the discharge amount of molten material by reducing the frictional resistance in a material passage can be provided. Further, by stabilizing the amount of molten material discharged, it is possible to provide a discharge unit capable of improving the quality of molded products.

FIG. 4 is a cross-sectional view showing an ejection stop state of the ejection unit according to one embodiment of the present invention; FIG. 2 is a cross-sectional view showing an ejection state of the ejection unit according to the embodiment of FIG. 1; (a) is an explanatory view schematically showing dimple processing in the discharge unit of the present invention, (b) is an enlarged explanatory view showing the surface condition of the material passage before dimple processing, and (c) is dimple processing. (d) is an enlarged explanatory view showing the surface condition of the material passage after the application of oil-repellent treatment; FIG.

One embodiment of the dispensing unit 10 of the present invention will be described in detail below with reference to FIGS. 1 and 2. FIG. In this embodiment, a case in which the discharge unit 10 is applied to a hot runner type injection molding machine will be described as an example.

1 and 2 are cross-sectional views of a discharge unit 10 of the present invention, with FIG. 1 showing the discharge unit 10 in a stopped state and FIG. 2 showing the discharge unit 10 in an injection state.

As shown in FIGS. 1 and 2, the discharge unit 10 includes a material passage 5 through which a molten material M such as a thermoplastic resin used for resin molding passes; a hot runner block 20 having the material passage 5 therein; It has a nozzle portion 30 (also referred to as a hot runner nozzle 30) that has a passage 5 inside and discharges the molten material M, and the like. The ejection unit 10 also includes a valve pin 40 that opens and closes the ejection port 31 formed in the nozzle portion 30, an elevating mechanism 50 that elevates the valve pin 40, and the like.

The hot runner block 20 has a material passage 5a formed therein and is provided so as to extend in the lateral direction in the drawing. A tubular nozzle portion 30 is connected to the hot runner block 20 so as to face downward. The nozzle portion 30 has a material passage 5b formed therein. Further, the material passage 5a on the hot runner block 20 side and the material passage 5b on the nozzle portion 30 side communicate with each other. The hot runner block 20 supplies the molten material M supplied from a supplying portion (not shown) for the molten material M to the material passage 5b on the nozzle portion 30 side through the material passage 5a.

The nozzle part 30 is formed in a cylindrical shape. The nozzle portion 30 has a discharge port 31 formed downstream of the material passage 5b by narrowing the diameter of the tip side of the material passage 5b. The ejection port 31 can eject the molten material M. As shown in FIG. In addition, the number of nozzle parts 30 is not limited to one, and a plurality of nozzle parts 30 may be provided in the hot runner block 20 .

The nozzle portion 30 has a valve pin 40 inserted inside the material passage 5b. A heater 32 for heating the molten material M passing through the material passage 5b is provided on the outer circumference of the nozzle portion 30. As shown in FIG. As a result, the molten material M in the material passage 5b is heated and maintained in a molten state. Here, the heating temperature of the molten material M is, for example, 200 to 240.degree. In addition, the heater 32 is arranged at an appropriate place in the discharge unit 10 and configured so that the molten material M is maintained in a molten state throughout the material passage 5 .

In the nozzle portion 30, the inner wall 5c of the material passage 5b is subjected to a surface treatment 33 such as dimple processing or oil-repellent processing. The surface treatment 33 may be applied to a portion of the material passage 5b or to the entire material passage 5b. Moreover, the surface treatment 33 may be applied not only to the material passage 5b but also to appropriate portions of the material passage 5a and the material passage 5. FIG. Details of the surface treatment 33 will be described later.

A cavity 61 of a mold 60 is connected to the ejection port 31 of the nozzle portion 30 . As shown in FIG. 2 , the molten material M discharged from the discharge port 31 is poured into the cavity 61 to form a molded product within the cavity 61 .

The valve pin 40 passes through the hot runner block 20 and is inserted into the material passage 5b of the nozzle portion 30. As shown in FIG. The upper end side of the valve pin 40 is positioned outside the hot runner block 20 and is connected to an elevating mechanism 50 . The lifting mechanism 50 has a cylinder 51 as a drive source, and a cylinder shaft 52 of the cylinder 51 is connected to the valve pin 40 . As a result, the valve pin 40 advances and retreats (elevates) in the axial direction as the cylinder shaft 52 advances and retreats. Further, the valve pin 40 is subjected to surface treatment 33 in the same manner as the inner wall 5c of the material passage 5b. Details of the surface treatment 33 will be described later.

As shown in FIG. 1, when the cylinder shaft 52 extends in the axial direction, the lower end side of the valve pin 40 can move closer to the discharge port 31 to block the discharge port 31 . As a result, the discharge port 31 is closed, and the flow of the molten material M can be stopped.

FIG. 2 shows a state in which the lower end side of the valve pin 40 is separated from the discharge port 31 by retracting the cylinder shaft 52 and removed. When the valve pin 40 separates from the ejection port 31, the ejection port 31 is opened. Here, the molten material M in the material passage 5 is always pressurized by an injection molding machine (not shown). Therefore, as the discharge port 31 is opened, the molten material M in the material passage 5 is discharged from the discharge port 31 and filled in the cavity 61 .

One embodiment of the discharge unit 10 of the present invention has been described above, and the details of the surface treatment 33 will now be described with reference to FIG. It should be noted that the illustration is different from the actual scale for easy understanding.

As described above, in the discharge unit 10 of the present invention, the inner wall 5c of the material passage 5 and the outer peripheral surface of the valve pin 40 are subjected to the surface treatment 33. As shown in FIG. Here, the surface treatment 33 applied to the ejection unit 10 of the present invention is roughly divided into two kinds of processing methods, dimple processing and oil-repellent processing.

FIG. 3(a) is a schematic view of the case where the inner wall 5c of the material passage 5 is dimpled as the surface treatment 33. FIG. FIG. 3(b) is an enlarged explanatory view of the surface state of the inner wall 5c of the material passage 5 before dimple processing, and FIG. 3(c) is an enlarged view of the inner wall 5c of the material passage 5 after dimple processing. It is explanatory drawing which expanded the surface state.

FIG. 3(b) shows a state before dimple processing is applied to the inner wall 5c of the material passage 5. Conventionally, finishing processing is performed by, for example, a grinder. As a result, the inner wall 5c of the material passage 5 has a large number of protrusions 5d with a height of about 100 μm before dimple processing. Therefore, the molten material M flowing through the material passage 5 receives a large frictional resistance. As a result, there arise problems that the flow velocity of the molten material M flowing through the material passage 5 decreases and the molten material M and the material passage 5 generate heat. As described above, when the flow velocity of the molten material M decreases, the amount of the molten material M discharged into the cavity 61 decreases, resulting in defective molding. Further, when the molten material M and the material passage 5 generate heat, the temperature control of the nozzle portion 30 becomes uneven, which causes a problem of defective molding.

Therefore, in the discharge unit 10 of the present invention, as shown in FIG. 3A, the inner wall 5c of the material passage 5 is dimpled by shot blasting. Shot blasting is performed by injecting an abrasive 7 (eg, alumina, glass beads, silicon carbide, etc.) having a particle size of 200 μm or less from the processing nozzle 6 toward the inner wall 5 c of the material passage 5 .

FIG. 3(c) shows the state after dimple processing, in which the corners of the projections 5d are rounded and the depth D of the unevenness is, for example, 20 to 30 μm. As a result, the frictional resistance in the material passage 5 is reduced, so that the molten material M flows smoothly. In addition, since the ejection amount of the molten material M ejected from the nozzle portion 30 is stabilized, the accuracy of speed control of the molten material M can be improved. Furthermore, since heat generation in the nozzle portion 30 is suppressed, the accuracy of temperature control of the nozzle portion 30 can be improved. These can suppress the occurrence of molding defects.

Note that the dimple processing is not limited to shot blasting, and rolling that flattens the surface by pressing a hard member, etching that flattens the surface by chemically dissolving it, and shot peening can also be used. .

FIG. 3(d) is a schematic diagram showing a state in which the inner wall 5c of the material passage 5 has been subjected to oil-repellent treatment. As shown in the drawing, an oil-repellent treatment is applied so as to cover the projections 5d of the inner wall 5c of the material passage 5. As shown in FIG. Here, for the oil repellent treatment, for example, a material having oil repellency such as fluororesin is used. As a result, the molten material M repels the surface treatment 33 and the frictional resistance with the material passage 5 is reduced. In addition, by forming the oil-repellent treatment with an appropriate thickness (for example, the depth D of the unevenness is 20 to 30 μm), the protrusion 5d of the material passage 5 is covered and the depth D of the unevenness is reduced. , the frictional resistance is further reduced. As a result, the molten material M smoothly flows through the material passage 5, and the discharge amount of the molten material M is stabilized. Moreover, since heat generation in the nozzle portion 30 is suppressed, the accuracy of temperature control of the nozzle portion 30 can be improved. Therefore, the occurrence of molding defects can be suppressed.

The depth D of the unevenness is not limited to the above-described embodiment, and can be appropriately changed according to the material and properties of the molten material M. Here, if the depth D of the irregularities is made smaller than 20 μm to make the surface of the material passage 5 too flat, the molten material M and the surface of the material passage 5 come into surface contact, increasing frictional resistance. Therefore, it is desirable that the depth D of the irregularities is 20 μm or more. Further, if the depth D of the unevenness is greater than 30 μm, the molten material M may enter the unevenness to increase the frictional resistance, or the molten material M may remain on the inner wall 5c of the material passage 5. . Therefore, it is desirable that the depth D of the unevenness due to the surface treatment 33 is 30 μm or less.

It should be noted that it is preferable to use a material having heat resistance equal to or higher than the heating temperature (for example, 240° C.) of the molten material M as the oil-repellent material. By using such a heat-resistant material, it is possible to prevent the oil-repellent surface treatment 33 from being detached or denatured by the heat of heating.

The embodiments of the ejection unit 10 of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and appropriate modifications can be made within the scope of the invention.

In the present embodiment, the case where the discharge unit 10 is used for hot runner injection molding was exemplified, but the discharge unit 10 of the present invention is not limited to this. For example, it can be used for various things. Also, various kinds of melting materials can be used.

Moreover, in this embodiment, the hot runner block 20 and the nozzle section 30 are provided as separate bodies, but the hot runner block 20 and the nozzle section 30 may be formed integrally. Also, the shapes of the hot runner block 20, the nozzle portion 30, the discharge port 31, and the valve pin 40 can be made into various shapes according to the shape of the mold 60 and the like. Also, the shape and diameter of the material passage 5 can be changed as appropriate. Also, the number of hot runner blocks 20 and nozzle portions 30 to be provided is not limited to one, but may be plural. Further, the lifting mechanism 50 may use not only the cylinder 51 but also various driving sources such as a motor.

In this embodiment, dimple processing and oil-repellent processing are applied to the entire interior of the material passage 5 and the entire outer peripheral surface of the valve pin 40, but the surface treatment 33 may be applied only partially. In the above case, it is desirable to apply the surface treatment 33 to the area where the diameter of the material passage 5a is narrowed around the discharge port 31 and the tip portion of the valve pin 40 located in this area. It should be noted that, in order to allow the molten material M to flow smoothly, it is desirable that the change in frictional resistance in the material passage 5 is small. It is desirable to apply it to the outer peripheral surface of the valve pin 40 located.

In the present embodiment, the surface treatment 33 using shot blasting is exemplified as the dimple processing, but suitable irregularities may be provided by rolling, etching, or the like. Further, in the present embodiment, as an example of the oil-repellent treatment, the surface of the material passage 5 is coated with fluorine resin. Various materials can be used. Moreover, the material used for the oil-repellent treatment may be not only one type but also a combination of a plurality of materials. Moreover, the surface treatment 33 may use both dimple processing and oil-repellent processing. As a result, a synergistic effect can be expected from the dimple processing and the oil-repellent processing.

Further, in the present embodiment, dimple processing and oil-repellent processing are performed so that the surface roughness is 20 to 30 μm, but the present invention is not limited to this. The degree of surface roughness can be changed to various types of roughness according to, for example. When the oil-repellent treatment is applied, the frictional force can be expected to be reduced due to the oil-repellent effect, so the influence of surface roughness is reduced. Therefore, when applying oil-repellent treatment, the surface roughness may not be considered.

In the present embodiment, dimple processing is performed by shot blasting, rolling, or etching, but may be processed by various means such as polishing.

In the present embodiment, the oil-repellent treatment is performed by either fluororesin treatment or silicone resin treatment, but various materials may be used as long as they have a low affinity for the molten material M. can. In the above case, it is preferable to use a material having a heat resistance equal to or higher than the melting temperature of the melting material M to be used.

It should be noted that the present invention is not limited to those exemplified in the above-described embodiments and modifications, and those skilled in the art will recognize that other embodiments can be made from the teachings and spirit of the invention without departing from the scope of the claims. easy to understand.

INDUSTRIAL APPLICABILITY The present invention can be used when molding various resin parts by injection molding, and in particular can be suitably used for hot runner injection molding. In addition, the present invention can be suitably used when molding parts that require precision, such as automobile parts, by injection molding.

M: Molten material 5: Material passage 5a: Material passage 5b: Material passage 5c: Inner wall 10: Discharge unit 20: Hot runner block 30: Nozzle part (hot runner nozzle)
31: Discharge port 32: Heater 33: Surface treatment 40: Valve pin 60: Mold 61: Cavity

Claims (1)

A discharge unit for discharging a molten material used for resin molding,
a material passage through which the molten material passes;
a discharge port for discharging the molten material passing through the material passage;
a valve pin that is inserted into the material passage and moves toward and away from the discharge port to open and close the discharge port;
An oil -repellent material having a heat resistance equal to or higher than the heating temperature of the molten material for the purpose of reducing the depth of unevenness formed on either or both of the inner wall of the material passage and the outer peripheral surface of the valve pin. A discharge unit characterized by being applied by.

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