Injection molding apparatus, control device, method for controlling an injection molding apparatus, and method for manufacturing resin molded products.

Abstract

To effectively suppress formation of poor appearance in a valve gate type injection molding device.SOLUTION: An injection molding device comprises: a metal mold main body with a mold cavity formed by mold-closing a first mold and a second mold; a gate device provided with an injection hole for injecting a molten resin; a valve pin with a tip displaceable from a clogging position for clogging the injection hole and an injection position for opening the injection hole; an actuator for displacing the valve pin; and a control device for controlling the actuator. In the valve pin, a tip face positioned on the mold cavity side is displaceable from the clogging position to an advance position advanced further to the mold cavity side. The control device controls the actuator in a manner that, after displacing the valve pin to the injection position, and at a timing after injecting the molten resin, the valve pin is displaced to the clogging position, then displacement of the valve pin to the advance position is performed.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to an injection molding apparatus that injects molten resin into a cavity of a mold body by closing and opening an injection hole with a valve pin. [Background Art]

[0002] Conventionally, when manufacturing resin molded products, a so-called valve gate type injection molding apparatus has been used, which injects molten resin into a cavity of a mold body by closing and opening an injection hole with a valve pin. The valve gate system is excellent in that the injection hole can be arranged at a relatively freely selected position according to the required quality (such as strength and density) of the product.

[0003] In this type of injection molding apparatus, molten resin is injected from the injection hole by displacing the valve pin between an open position where the injection hole is opened and a closed position where the injection hole is closed (see Patent Document 1). [Prior Art Documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Unexamined Patent Publication No. 11-77760 [Summary of the Invention] [Problem to be Solved by the Invention]

[0005] However, with a configuration that only displaces the valve pin between the open position and the closed position as in the above-described injection molding apparatus, appearance defects such as sink marks are likely to occur on the mold-side surface of the resin molded product across the valve pin, so this configuration is not suitable for molding products in which this surface serves as a design surface.

[0006] To prevent such surface defects, it might be possible to adopt a so-called side-gate injection molding machine. However, the side-gate method imposes significant constraints on the position of the injection hole, which often prevents the product from meeting the required quality standards. Therefore, its adoption is often not practical.

[0007] This invention was made to solve these problems and aims to provide a technology for effectively suppressing the occurrence of surface defects in a valve gate type injection molding apparatus. [Means for solving the problem]

[0008] The injection molding apparatus according to this disclosure comprises a mold body in which a cavity is formed by closing a first mold and a second mold; a gate device provided in the first mold and having an injection hole formed therein for injecting molten resin into the cavity; a valve pin that can be displaced within the gate device to a closed position in which it moves toward the cavity side and its tip closes the injection hole, and an injection position in which it moves toward the opposite side of the cavity and its tip opens the injection hole, thereby injecting the molten resin from the injection hole; an actuator for displacing the valve pin; and a control device for controlling the actuator, wherein the valve pin can also be displaced to an advanced position in which its tip surface located toward the cavity side moves further toward the cavity side from the closed position, and the control device controls the actuator to displace the valve pin to the injection position, then, at a timing after the molten resin has been injected, to displace the valve pin to the closed position, and then to the advanced position. [Effects of the Invention]

[0009] According to this disclosure, by advancing the valve pin toward the cavity side while the molten resin injected into the cavity hardens into a resin molded product, the region of the resin molded product corresponding to the valve pin is pressed. As a result, even if the region of the resin molded product located on the second mold side with respect to the valve pin is in a situation where it could recede toward the valve pin side and cause sink marks, this recede is suppressed by the advancement of the valve pin, thereby suppressing the occurrence of sink marks. Thus, the injection molding apparatus of this disclosure can effectively suppress the occurrence of appearance defects in resin molded products. [Brief explanation of the drawing]

[0010] [Figure 1] A diagram showing the configuration of an injection molding apparatus according to one embodiment of the present disclosure. [Figure 2] This figure shows a cross-sectional view of a key part of an injection molding apparatus according to one embodiment of the present disclosure. [Figure 3] Flowchart showing displacement control processing according to one embodiment of the present disclosure [Figure 4] A diagram showing the operation of an injection molding apparatus according to one embodiment of the present disclosure. [Figure 5] This figure shows a cross-sectional view of a key part of an injection molding apparatus according to one embodiment of the present disclosure. [Modes for carrying out the invention]

[0011] Hereinafter, one embodiment of this disclosure will be described with reference to the drawings. (1) Overall structure As shown in Figures 1 and 2, the injection molding apparatus 1 comprises a mold body 10, a gate device 20, a valve pin 30, an actuator 40, a control device 50, and a surrounding wall 60.

[0012] The mold body 10 forms a cavity 100 by closing the first mold 11 and the second mold 13. The mold body 10 is composed of a first mold 11 and a second mold 13 that are divided in a predetermined direction (up and down in this embodiment), and the second mold 13 is displaceable relative to the first mold 11 along its dividing direction, and the cavity 100 is formed as an internal space sandwiched between the two molds when the second mold 13 is displaced until it is closed with the first mold 11.

[0013] As shown in Figure 2, the gate device 20 is installed in the first mold 11 and has an injection hole 21 formed therein for injecting molten resin material (hereinafter referred to as "molten resin") toward the cavity 100. This gate device 20 is a cylindrical member that is embedded in the first mold 11 and extends until it reaches the cavity 100, with the injection hole 21 formed at the end that reaches the cavity 100 (the lower end in Figure 2).

[0014] The valve pin 30 is housed inside the gate device 20 and extends along the division direction of the mold body 10, and is movably mounted within the gate device 20. The valve pin 30 is displaceable to a closed position where it moves toward the cavity 100 and its tip closes the injection hole 21, an injection position where it moves toward the opposite side of the cavity 100 and its tip opens the injection hole 21, allowing molten resin to be injected from the injection hole 21, and an advanced position where its tip surface extends further toward the cavity 100 from the closed position.

[0015] In this embodiment, the position where the tip surface of the valve pin 30 has advanced a predetermined amount from the injection hole 21 toward the cavity 100 is the "advance position," and the position where the tip surface of the valve pin 30 coincides with the interface between the injection hole 21 and the cavity 100 is the "closed position."

[0016] The actuator 40 consists of a displacement mechanism for displacing the valve pin 30 and a motor that drives this displacement mechanism.

[0017] The control device 50 is a computer that displaces the valve pin 30 by controlling the operation of the actuator 40.

[0018] The surrounding wall 60 is formed at the tip of the gate device 20 on the cavity 100 side in a positional relationship that surrounds the injection hole 21, and is formed to have a height capable of surrounding at least the tip end surface of the valve pin 30 located at the advanced position. In the present embodiment, the surrounding wall 60 having a larger diameter than the injection hole 21 is provided as a part of the gate device 20 at the tip of the gate device 20 on the cavity 100 side.

[0019] Further, in the present embodiment, the surrounding wall 60 is formed such that the inner peripheral portion surrounding the injection hole 21 has the maximum height, and the height of the wall decreases as the distance from the injection hole 21 increases. In addition, the thickness of the surrounding wall 60 as a wall from the inner peripheral portion to the outer peripheral portion is set to a value sufficiently larger than the height of the wall (specifically, the thickness is 50 to 100 times the height of the wall).

[0020] In the injection molding apparatus 1 configured as described above, the valve pin 30 is displaced to an injection position where molten resin is injected by opening the injection hole 21, displaced to a closing position where the injection hole 21 is closed at a timing after the molten resin is injected, and after a predetermined cooling period has elapsed, the valve pin 30 is displaced to an advanced position where the tip end surface further advances toward the cavity 100 side from the closing position, thereby manufacturing a resin molded product.

[0021] (2) Processing procedure by control device The procedure of "displacement control processing" executed by the control device 50 through a program stored in the built-in memory 51 will be described below with reference to FIG. 3. This displacement control processing is started when a start command is received from an unillustrated interface (operating device or communication device).

[0022] When this displacement control process is activated, it is first checked whether it is time to displace the valve pin 30 to the injection position (s110), and the system remains in a waiting state until it is determined that it is time to displace it to the injection position (s110:NO). Here, it is determined that it is time to displace the valve pin 30 to the injection position when the following are detected by sensors (not shown): the valve pin 30 is in the closed position, the mold closing of the first mold 11 and the second mold 13 is complete, and the molten resin is filled into the gate device 20.

[0023] If it is determined that it is time to displace the valve pin 30 to the injection position (s110: YES), the valve pin 30 is displaced to the injection position (s120). Here, a command is given to displace the valve pin 30 to the injection position, and the actuator 40, upon receiving this command, displaces the valve pin 30 to the injection position. As a result, the injection of molten resin 200 from the injection hole 21 into the cavity 100 begins (see Figure 4(a)).

[0024] Next, it is checked whether it is time to displace the valve pin 30 to the closed position (s130), and the system remains in a waiting state until it is determined that it is time to displace it to the closed position (s130: NO). Here, after s130, if the time required for a specified amount of molten resin to be injected from the injection hole 21 has elapsed, it is determined that it is time to displace it to the closed position.

[0025] If it is determined that it is time to displace the valve pin 30 to the closed position (s130: YES), the valve pin 30 is displaced to the closed position (s140). Here, a command is given to displace the valve pin 30 to the closed position, and the actuator 40, upon receiving this command, displaces the valve pin 30 to the closed position. This completes the injection of molten resin 200 from the injection hole 21 into the cavity 100 (see Figure 4(b)).

[0026] Next, it is checked whether it is time to displace the valve pin 30 to the extended position (s150), and the system remains in a waiting state until it is determined that it is time to displace it to the extended position (s150: NO). Here, the time required for the molten resin injected into the cavity 100 to harden (cooling time) is used as a reference, and it is determined that it is "time to displace it to the extended position" when a certain amount of time has elapsed before this reference.

[0027] If it is determined that it is time to displace the valve pin 30 to the extended position (s150: YES), the valve pin 30 is extended (s160). In this extension operation, the valve pin 30 is displaced from the closed position to the extended position, and then displaced from the extended position back to the closed position.

[0028] Specifically, first, a command is issued to displace the valve pin 30 to the extended position, and the actuator 40, upon receiving this command, displaces the valve pin 30 to the extended position (see Figure 4(c)). Here, a command is issued to displace the valve pin 30 in multiple stages until it reaches the extended position, and the actuator 40, upon receiving this command, gradually displaces the valve pin 30 to the extended position in multiple stages. After a predetermined waiting time, a command is issued to displace the valve pin 30 to the closed position, and the actuator 40, upon receiving this command, displaces the valve pin 30 to the closed position (Figure 4(c)⇒(b)).

[0029] (3) Variant Although embodiments of the present disclosure have been described above, the present disclosure is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention. In particular, the various modifications described herein can be combined as needed.

[0030] For example, in this embodiment, a configuration is shown in which the tip surface of the valve pin 30 located on the cavity 100 side coincides with the interface between the injection hole 21 and the cavity 100 as the "closed position". However, the "closed position" only needs to be able to close the injection hole 21, and the tip surface of the valve pin 30 may be at a position a predetermined distance away from the interface between the injection hole 21 and the cavity 100 toward the first mold 11. In this case, the "advance position" may be a position where the tip surface of the valve pin 30 has not advanced from the injection hole 21 toward the cavity 100, as long as the tip surface has advanced further toward the cavity 100 from the closed position.

[0031] Furthermore, in the above embodiment, the displacement control process s160 is configured to perform an "extension operation" only once, in which the valve pin 30 is displaced from the closed position to the extended position, and then displaced from the extended position back to the closed position. However, this "extension operation" may be performed repeatedly multiple times.

[0032] Furthermore, in the above embodiment, a configuration was illustrated in which a surrounding wall 60 with a larger diameter than the injection hole 21 is formed at the tip of the gate device 20. However, the surrounding wall 60 may be formed to surround the injection hole 21 with the same inner diameter as the injection hole 21.

[0033] (4) Effects In the above embodiment, the valve pin 30 is advanced toward the cavity 100 while the molten resin injected into the cavity 100 is curing as a resin molded product, thereby pressing the area of ​​the resin molded product corresponding to the valve pin 30. As a result, as shown in Figure 5, even if the area of ​​the molten resin that becomes the resin molded product that is located on the second mold 13 side with the valve pin 30 in between recedes toward the valve pin 30 side, potentially causing sink marks 210, the receding of this area is suppressed by the advance of the valve pin 30, thereby suppressing the occurrence of sink marks 210. Thus, the injection molding apparatus 1 of the above embodiment can effectively suppress the occurrence of appearance defects in the resin molded product.

[0034] Furthermore, in the above embodiment, the displacement control process controls the displacement of the valve pin 30 in multiple stages until it reaches the extended position, so that the area corresponding to the valve pin 30 in the resin molded product can be gradually pressed.

[0035] Furthermore, in the above embodiment, the valve pin 30 is configured to be displaced to a position where its tip surface is advanced by a predetermined amount from the injection hole 21 towards the cavity 100, and since the tip side is displaced until it penetrates the resin molded product, it is possible to suppress the generation of sink marks 210 corresponding to the volume that penetrates the resin molded product.

[0036] Furthermore, in the above embodiment, since the surrounding wall 60 is formed to surround the injection hole 21, as shown in Figure 5, the pressing force when the valve pin 30 is displaced to the advanced position can be effectively transmitted to the resin molded product. [Explanation of Symbols]

[0037] 1: Injection molding machine, 10: Mold body, 11: First mold, 13: Second mold, 20: Gate device, 21: Injection hole, 30: Valve pin, 40: Actuator, 50: Control device, 51: Built-in memory, 60: Enclosing wall, 100: Cavity, 210: Sink mark.

Claims

1. A mold body in which a cavity is formed by closing the first and second molds, A gate device provided in the first type, having an injection hole formed in the cavity for injecting molten resin, A valve pin that is displaceable within the gate device to a closed position where its tip closes the injection hole, and to an injection position where its tip opens the injection hole, thereby injecting the molten resin from the injection hole, An actuator for displacing the valve pin, The system comprises a control device for controlling the actuator, The valve pin is also displaceable such that its tip surface, located on the cavity side, extends further toward the cavity from the closed position and enters the cavity. The control device displaces the valve pin to the injection position, then displaces the valve pin to the closed position at a timing after the molten resin has been injected, and then displaces the valve pin to the extended position, thereby controlling the actuator. The gate device further comprises a surrounding wall formed to protrude from the tip surface of the gate device so as to surround the injection hole with a diameter larger than the injection hole, The aforementioned extended position of the valve pin is the position where the tip surface of the valve pin has advanced a predetermined amount from the injection hole toward the cavity and entered the cavity. The surrounding wall is formed to protrude towards the cavity at a height higher than the tip surface of the valve pin in the extended position, and to surround the tip surface of the valve pin. Injection molding equipment.

2. A method for manufacturing a resin molded product using the injection molding apparatus described in claim 1.

3. A program for causing a computer to function as the control device described in claim 1.

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