US-12623387-B2 - Injection molding machine for performing foam molding and method for controlling injection molding machine

Abstract

An injection molding machine includes a heating cylinder provided with a gas inlet, a screw, a gas cylinder, a pressure reducing valve configured to reduce a primary pressure of a gas from the gas cylinder to a secondary pressure, a gas supply portion configured to supply the gas at the secondary pressure to the gas inlet, a secondary pressure detection device configured to detect the secondary pressure, and a controller. The controller is configured to detect an abnormality by comparing a set pressure set in advance in the injection molding machine with the secondary pressure.

Inventors

• Akihiro Naito
• Takuya Yufu

Assignees

• THE JAPAN STEEL WORKS, LTD.

Dates

Publication Date

20260512

Application Date

20211117

Priority Date

20201210

Claims (20)

1. 1 . An injection molding machine comprising: a heating cylinder having a gas inlet; a screw drivable in the heating cylinder; a gas supply device configured to supply a gas to the gas inlet; and a controller, wherein an inside of the heating cylinder is divided into a plurality of sections, and from upstream, the inside of the heating cylinder is divided into a first compression and metering section in which the molten injection material is compressed, a starvation section in which a pressure of the injection material decreases, and a second compression and metering section in which the injection material is compressed again, and wherein the gas inlet is provided in the starvation section, wherein the gas supply device comprises: a gas supply source configured to supply a gas; a pressure adjustment device configured to adjust a primary pressure of a gas from the gas supply source to a secondary pressure; a check valve provided downstream of the pressure adjustment device; and a secondary pressure detection device configured to detect the secondary pressure at a downstream of the check valve, wherein the gas inlet is connected to the heating cylinder downstream of the check valve, and the gas supply device is configured to supply the gas at the secondary pressure to the gas inlet, wherein the controller is configured to detect an abnormality in a case where the secondary pressure becomes out of a normal pressure range, and wherein the normal pressure range, which is a normal pressure range of the secondary pressure, is greater than a value that is obtained by subtracting a second threshold from a set pressure for the gas at the secondary pressure and is less than a value that is obtained by adding a first threshold to the set pressure, the first threshold being a value of 0.1 MPa to 1.5 MPa, and the second threshold being a value of 0.1 MPa to 1.5 MPa.
2. 2 . The injection molding machine according to claim 1 , wherein the controller is configured to determine whether the secondary pressure is greater than the normal pressure range and the secondary pressure is less than a value that is obtained by adding a third threshold, which is greater than the first threshold, to the set pressure, and the controller is configured to issue an alarm indicating a risk of a vent-up at the gas inlet based on the determination.
3. 3 . The injection molding machine according to claim 1 , wherein the controller is configured to determine whether the secondary pressure is equal to or greater than a value that is obtained by adding a third threshold, which is greater than the first threshold, to the set pressure, and the controller is configured to stop a molding cycle after completion of the molding cycle being executed based on the determination.
4. 4 . The injection molding machine according to claim 1 , wherein the gas supply device comprises a gas pipe configured to supply the gas at the secondary pressure to the gas inlet or an on-off device disposed at a gas injection portion, and wherein the controller is configured to determine whether the secondary pressure is equal to or greater than a value that is obtained by adding a third threshold, which is greater than the first threshold, to the set pressure, and the controller is configured to close the on-off device and stops a molding cycle after completion of the molding cycle being executed based on the determination.
5. 5 . The injection molding machine according to claim 1 , wherein the controller comprises a pressure controller configured to control the pressure adjustment device, and wherein the controller is configured to determine whether the secondary pressure is greater than the normal pressure range and the secondary pressure is less than a value that is obtained by adding a third threshold, which is greater than the first threshold, to the set pressure, and the controller is configured to perform pressure decrease control to cause the secondary pressure to fall within the normal pressure range by the pressure controller based on the determination.
6. 6 . The injection molding machine according to claim 5 , wherein the controller is configured to determine whether the secondary pressure continuously exceeds the normal pressure range during a first stabilization time from a start of the pressure decrease control, and the controller is configured to stop a molding cycle after completion of the molding cycle being executed based on the determination.
7. 7 . The injection molding machine according to claim 5 , wherein the gas supply device comprises a gas pipe configured to supply the gas at the secondary pressure to the gas inlet or an on-off device disposed at a gas injection portion, and wherein the controller is configured to determine whether the secondary pressure continuously exceeds the normal pressure range during a first stabilization time from a start of the pressure decrease control, and the controller is configured to close the on-off device and stops a molding cycle after completion of the molding cycle being executed based on the determination.
8. 8 . The injection molding machine according to claim 5 , wherein a feeder configured to adjust a supply amount of an injection material is attached to the heating cylinder, and wherein the controller is configured to determine whether the secondary pressure continuously exceeds the normal pressure range during a first stabilization time from a start of the pressure decrease control, and the controller is configured to perform supply amount reduction control including reducing the supply amount of the injection material by controlling the feeder based on the determination.
9. 9 . The injection molding machine according to claim 1 , wherein a feeder configured to adjust a supply amount of an injection material is attached to the heating cylinder, and wherein the controller is configured to determine whether the secondary pressure is greater than the normal pressure range and the secondary pressure is less than a value that is obtained by adding a third threshold, which is greater than the first threshold, to the set pressure, and the controller is configured to perform supply amount reduction control including reducing the supply amount of the injection material by controlling the feeder based on the determination.
10. 10 . The injection molding machine according to claim 8 , wherein the controller is configured to determine whether the secondary pressure continuously exceeds the normal pressure range during a second stabilization time from a start of the supply amount reduction control, and the controller is configured to stop a molding cycle after completion of the molding cycle being executed based on the determination.
11. 11 . The injection molding machine according to claim 8 , wherein the gas supply device comprises a gas pipe configured to supply the gas at the secondary pressure to the gas inlet or an on-off device disposed at a gas injection portion, and wherein the controller is configured to determine whether the secondary pressure continuously exceeds the normal pressure range during a second stabilization time from a start of the supply amount reduction control, and the controller is configured to close the on-off device and stops a molding cycle after completion of the molding cycle being executed based on the determination.
12. 12 . The injection molding machine according to claim 1 , wherein the controller is configured to determine whether the secondary pressure is less than the normal pressure range and a decrease rate of the secondary pressure is equal to or greater than a fourth threshold, and the controller is configured to stop a molding cycle after completion of the molding cycle being executed based on the determination.
13. 13 . The injection molding machine according to claim 1 , wherein the gas supply device comprises a gas pipe configured to supply the gas at the secondary pressure to the gas inlet or an on-off device disposed at a gas injection portion, and wherein the controller is configured to determine whether the secondary pressure is less than the normal pressure range and a decrease rate of the secondary pressure is equal to or greater than a fourth threshold, and the controller is configured to close the on-off device and stop a molding cycle after completion of the molding cycle being executed based on the determination.
14. 14 . The injection molding machine according to claim 1 , wherein a feeder configured to adjust a supply amount of an injection material is attached to the heating cylinder, and wherein the controller is configured to determine whether the secondary pressure is greater than a value that is obtained by subtracting a fifth threshold, which is greater than the second threshold, from the set pressure, and a decrease rate of the secondary pressure is equal to or greater than a fourth threshold, and the controller is configured to perform supply amount increase control including increasing the supply amount of the injection material by controlling the feeder based on the determination.
15. 15 . The injection molding machine according to claim 14 , wherein the controller is configured to determine whether the decrease rate of the secondary pressure temporarily exceeds the fourth threshold during a predetermined cycle from a start of the supply amount increase control or during a fourth stabilization time from the start of the supply amount increase control, and the controller is configured to stop a molding cycle after completion of the molding cycle being executed based on the determination.
16. 16 . The injection molding machine according to claim 14 , wherein the gas supply device comprises a gas pipe configured to supply the gas at the secondary pressure to the gas inlet or an on-off device disposed at a gas injection portion, and wherein the controller is configured to determine whether the decrease rate of the secondary pressure temporarily exceeds the fourth threshold during a predetermined cycle from a start of the supply amount increase control or during a fourth stabilization time from the start of the supply amount increase control, and the controller is configured to close the on-off device and stop a molding cycle after completion of the molding cycle being executed based on the determination.
17. 17 . The injection molding machine according to claim 1 , wherein the controller is configured to determine whether the secondary pressure is equal to or less than a value that is obtained by subtracting a fifth threshold, which is greater than the second threshold, from the set pressure, and the controller is configured to stop a molding cycle after completion of the molding cycle being executed based on the determination.
18. 18 . The injection molding machine according to claim 1 , wherein the gas supply device comprises a gas pipe configured to supply the gas at the secondary pressure to the gas inlet or an on-off device disposed at a gas injection portion, and wherein the controller is configured to determine whether the secondary pressure is equal to or less than a value that is obtained by subtracting a fifth threshold, which is greater than the second threshold, from the set pressure, and the controller is configured to close the on-off device and stop a molding cycle after completion of the molding cycle being executed based on the determination.
19. 19 . The injection molding machine according to claim 1 , wherein the controller is configured to determine whether the secondary pressure falls below the normal pressure range but is greater than a value that is obtained by subtracting a fifth threshold, which is greater than the second threshold, from the set pressure, and a decrease rate of the secondary pressure is less than a fourth threshold, and the controller is configured to issue an alarm for prompting replacement of the gas supply source based on the determination.
20. 20 . The injection molding machine according to claim 1 , wherein the gas supply device comprises: a plurality of the gas supply sources; and a gas supply source switching device configured to selectively switch one gas supply source to be used from the plurality of gas supply sources, and wherein in a case where the secondary pressure falls below the normal pressure range but is greater than a value that is obtained by subtracting a fifth threshold, which is greater than the second threshold, from the set pressure, and a decrease rate of the secondary pressure is less than a fourth threshold, the controller switches the gas supply source currently being used to another gas supply source by the gas supply source switching device.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This is a National Phase Entry of PCT International Application No. PCT/JP2021/042338 filed on Nov. 17, 2021, which claims priority to Japanese Patent Application No. 2020-204664 filed on Dec. 10, 2020, the contents of all which are incorporated herein by reference in their entirety. BACKGROUND 1. Field The present invention disclosure relates to an injection molding machine for molding a foam molded product by injecting an inert gas into an injection material, and a method for controlling such an injection molding machine. 2. Description of Related Art An injection molding machine for obtaining a foam molded product by using a physical foaming agent, that is, an inert gas is substantially implemented as follows. That is, an injection molding machine for foam molding includes a heating cylinder and a screw. An inside of the heating cylinder is divided into a plurality of sections according to a shape of the screw, and includes, from upstream to downstream, a first compression and metering section, a starvation section, and a second compression and metering section. The heating cylinder is provided with an inert gas injection portion so as to correspond to the starvation section. An inert gas is supplied from a gas supply source such as a gas cylinder. A primary pressure of the gas supplied from the gas supply source is reduced to a secondary pressure by a pressure reducing valve. The inert gas at the secondary pressure is supplied to the injection portion. An injection material is fed from upstream to downstream in the heating cylinder by the screw, is melted, and is kneaded in the first compression and metering section. Then, in the starvation section, a pressure of the injection material decreases, and the inert gas at the secondary pressure is injected. The injection material into which the inert gas is injected is kneaded, compressed, and metered in the second compression and metering section, and is injected into a mold to obtain a foam molded product. In the injection molding machine for foam molding, a so-called vent-up may occur in which the injection material is pushed up in the inert gas injection portion and blocks the injection portion. An injection molding machine for foam molding described in JP2014-200937 is provided with a vent-up detection mechanism on an injection portion, performs mechanical detection when a vent-up occurs, and pushes an injection material back into a heating cylinder. SUMMARY In the injection molding machine for foam molding, various problems other than the vent-up may occur. For example, there may be a backflow of the inert gas or a defective supply of the inert gas. The secondary pressure of the inert gas is appropriately controlled by the pressure reducing valve, and the secondary pressure is confirmed to be a desired pressure by a pressure gauge that allows visual confirmation. The injection material is also controlled to be appropriately supplied. However, such problems may not be completely prevented, and there may be a problem that even if a problem occurs, the problem is not noticed, so that a large number of defective products may be produced. Other problems and novel features will become apparent from the description of the present specification and the accompanying drawings. The present disclosure relates to an injection molding machine having a following configuration. That is, the injection molding machine includes a heating cylinder provided with a gas inlet, a screw, a gas cylinder, pressure adjustment means configured to adjust a primary pressure of a gas from the gas cylinder to a secondary pressure, the gas inlet configured to supply the gas at the secondary pressure to the heating cylinder, secondary pressure detection means configured to detect the secondary pressure, and control means. The control means is configured to detect an abnormality by comparing a set pressure set in advance in the injection molding machine with the secondary pressure. According to the present disclosure, it is possible to quickly catch a sign of occurrence of a vent-up, a backflow of a gas, a defective supply of a gas, and the like, and to prevent occurrence of a defective product. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a front view showing an injection molding machine according to the present embodiment. FIG. 2 is a front sectional view showing an injection device according to the present embodiment. FIG. 3 is a flow chart showing a control method performed in the injection molding machine according to the present embodiment. FIG. 4 is a flow chart showing the control method performed in the injection molding machine according to the present embodiment. FIG. 5 is a flow chart showing the control method performed in the injection molding machine according to the present embodiment. FIG. 6 is a flow chart showing the control method performed in the injection molding machine according to the present embodiment. FIG. 7 is a flow chart s