Injection molding machine for foam molding and control method of injection molding machine

Abstract

An injection molding machine (1) includes a heating cylinder (17) provided with a gas injection port (26), a screw (18), a gas cylinder (30), a pressure reducing valve (34) that reduces a primary pressure of gas from the gas cylinder (30) to a secondary pressure, a gas supply portion (43) that supplies the gas at the secondary pressure to the gas injection port (26), an injection material pressure detecting mechanism that detects an injection material pressure in the vicinity of the gas injection port (26), and a control mechanism. The control mechanism detects an abnormality by comparing the injection material pressure with the secondary pressure.

Description

Technical Field

[0001] This invention relates to an injection molding machine for injecting inactive gas into injection material to form foamed articles, and a control method for such injection molding machine. Background Technology

[0002] An injection molding machine that uses a physical foaming agent, i.e., an inert gas, to produce foamed molded articles generally has the following structure: The injection molding machine for foaming consists of a heating cylinder and a screw. The heating cylinder is divided into multiple sections corresponding to the shape of the screw, including a first compression / metering section, a starvation section, and a second compression / metering section from upstream to downstream. An inert gas injection section is provided in the heating cylinder corresponding to the starvation section. The inert gas is supplied from a gas supply source such as a gas cylinder. The primary pressure of the gas supplied from the gas supply source is reduced to a secondary pressure by a pressure reducing valve. This secondary pressure inert gas is then supplied to the injection section.

[0003] The injection material is melted in a heated cylinder by a screw, fed from upstream to downstream, and mixed in the first compression / metering zone. Next, in the starvation zone, the pressure of the injection material is reduced and a secondary pressurized inert gas is injected. The injection material injected with the inert gas is mixed / compressed, metered, and injected into a mold in the second compression / metering zone to obtain a foamed molded product.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2014-200937 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] In injection molding machines used for foaming, there is a phenomenon called venting, where the injected material is pushed up in the inactive gas injection section, causing blockage of the injection section. Patent Document 1 describes an injection molding machine for foaming that is equipped with a venting detection mechanism in the injection section. If venting occurs, it is mechanically detected, and the injected material is pushed back into the heating cylinder.

[0009] In injection molding machines used for foam molding, various problems can occur besides material overflow. These include backflow of inert gases or poor supply of inert gases caused by abnormal injection material supply. The secondary pressure of the inert gases is appropriately controlled by a pressure reducing valve, and the pressure is visually confirmed to be at the desired level using a pressure gauge. Furthermore, the injection material is controlled to be supplied appropriately to the heating cylinder. However, it is impossible to completely prevent these problems, and there is a risk that problems may go unnoticed, resulting in a large number of defective products.

[0010] Other topics and new features can be found in the description and figures in this specification.

[0011] Methods for solving problems

[0012] This disclosure relates to an injection molding machine having the following configuration: The injection molding machine includes a heating cylinder with a gas injection port, a screw, a gas supply device, an injection material pressure sensor disposed near the gas injection port of the heating cylinder, and a control mechanism. The gas supply device includes a gas supply source and a pressure regulating mechanism that adjusts the primary pressure of the gas from the gas supply source to a secondary pressure, and supplies the secondary pressure gas from the gas injection port. Furthermore, the control mechanism detects abnormalities by comparing the injection material pressure detected by the injection material pressure detection mechanism with the secondary pressure.

[0013] Invention Effects

[0014] According to this disclosure, it is possible to quickly detect signs of material leakage or abnormal supply of injected materials and prevent the production of defective products. Attached Figure Description

[0015] Figure 1 This is a front view showing the injection molding machine of this embodiment.

[0016] Figure 2 This is a front cross-sectional view showing the injection device of this embodiment.

[0017] Figure 3 This is a flowchart illustrating the control method implemented in the injection molding machine according to this embodiment.

[0018] Figure 4 This is a flowchart illustrating the control method implemented in the injection molding machine according to this embodiment.

[0019] Figure 5 This is a flowchart illustrating the control method implemented in the injection molding machine according to this embodiment.

[0020] Figure 6 This is a diagram illustrating the control method of the injection molding machine according to this embodiment, implemented in accordance with the injection material pressure. Detailed Implementation

[0021] The specific embodiments will now be described in detail with reference to the accompanying drawings. It should be noted that the description is not limited to the following embodiments. To clarify the explanation, the following description and drawings have been appropriately simplified. In the drawings, the same reference numerals are used to label the same elements, and repeated descriptions are omitted as needed. Additionally, some sections have been omitted to avoid cluttering the drawings.

[0022] This implementation method will be described.

[0023] <Injection Molding Machine>

[0024] The injection molding machine 1 in this embodiment is as follows: Figure 1 As shown, the device generally consists of a mold clamping device 2 and an injection device 3 mounted on a base B, and is controlled by a controller 4, which serves as the control mechanism. The mold clamping device 2 can also be a direct-pressure type, but in this embodiment it is a toggle type. That is, the mold clamping device 2 consists of a fixed plate 7, a movable plate 8, a mold clamping housing 9, connecting rods 10, 10, ..., and a toggle mechanism 11 connecting the mold clamping housing 9 to the fixed plate 7. The mold clamping device 2 mounts molds 13 and 14 on the fixed plate 7 and the movable plate 8. When the toggle mechanism 11 is driven, molds 13 and 14 close.

[0025] <Injection Device>

[0026] The injection device 3 in this embodiment is as follows: Figure 2 The diagram shows an injection molding apparatus for foam molding using a physical foaming agent, i.e., gas. The injection apparatus 3 consists of a heating cylinder 17 and a screw 18 housed within the heating cylinder 17. The screw 18's thread depth varies from upstream to downstream, dividing the heating cylinder 17 into multiple zones. Specifically, the heating cylinder 17 is divided from the upstream side into a supply zone 20 for supplying and melting the injection material, a first compression / metering zone 21 for compressing the molten injection material, a starvation zone 22 for reducing the pressure of the injection material, and a second compression / metering zone 23. The heating cylinder 17 has a gas injection port 26 in the starvation zone 22 to inject gas into the injection material. In the second compression / metering zone 23, the injection material and gas are mixed.

[0027] <Gas Supply Device>

[0028] A gas supply device 28 according to this embodiment is connected to the gas injection port 26. The gas supply device 28 is configured to include two gas cylinders 30, 30, which serve as gas supply sources; gas cylinder opening and closing valves 31, 31; a primary gas pipe 33 that supplies gas from the gas cylinders 30, 30 via the gas cylinder opening and closing valves 31, 31; a pressure reducing valve 34 (pressure regulating mechanism) that adjusts the gas pressure in the primary gas pipe 33 to a secondary pressure; a secondary gas pipe 36 that supplies gas that has been reduced to a secondary pressure by the pressure reducing valve 34; a check valve 38 provided on the secondary gas pipe 36; and an opening and closing valve 39 (opening and closing mechanism) similarly provided on the secondary gas pipe 36. A primary pressure gauge 41 (primary pressure detection mechanism) for detecting the primary pressure is provided on the primary gas pipe 33, and a secondary pressure gauge 42 (secondary pressure detection mechanism) for detecting the secondary pressure is provided on the secondary gas pipe 36. The front end of the secondary gas pipe 36 becomes the gas supply section 43 and is connected to the gas injection port 26.

[0029] The primary pressure gauge 41 and secondary pressure gauge 42 of the devices constituting the gas supply device 28 are connected to the controller 4, and the primary and secondary pressures are input to the controller 4. In addition, the gas cylinder opening and closing valves 31, 31, pressure reducing valve 34, and opening and closing valve 39 are connected to the controller 4, and the gas cylinder opening and closing valves 31, 31, pressure reducing valve 34, and opening and closing valve 39 are controlled by the controller 4.

[0030] The gas supply device 28 of this embodiment is configured as described above, but the present invention can be implemented with one or more gas storage cylinders 30 as the gas supply source. The gas supply device 28 may also be configured with, for example, gas storage cylinders 30 and a pressurizing device, or a nitrogen generating device and a pressurizing device. Furthermore, the on / off valve 39 may be located midway in the gas pipe supplying secondary pressurized gas to the gas injection port, or an on / off mechanism such as a needle valve operating via compressed air may be provided at the gas injection section. In one embodiment, the gas storage cylinder on / off valves 31 and 31 are gas supply source switching mechanisms that select which of the gas storage cylinders 30 and 30 is the gas supply source to be used. By opening or closing the gas storage cylinder on / off valves 31 and 31, the gas storage cylinder 30 or 30 to be used can be switched.

[0031] It should be noted that the supplied gas is usually nitrogen, carbon dioxide, etc., which are inactive gases, but there are no restrictions on the type of gas, such as air, hydrocarbon gas, argon, helium, hydrogen, etc., which are dissolved in the resin.

[0032] In this embodiment, a gas cylinder opening / closing valve 31, a primary pressure gauge 41, a check valve 38, and an opening / closing valve 39 are provided, but these components are not essential. However, if these components are provided, various measures can be taken in case of an abnormality. Furthermore, in this embodiment, almost all the devices constituting the gas supply device 28 are connected to the controller 4, but this connection is not necessary. That is, the secondary pressure gauge 42 is not necessarily connected to the controller 4. However, if the secondary pressure gauge 42 is connected to the controller 4, a measured value of the secondary pressure can be obtained. Therefore, by comparing the injection material pressure described below with this measured value, it is possible to determine whether an abnormality has occurred.

[0033] <Injection Material Pressure Testing Organization>

[0034] The injection molding machine 1 of this embodiment is characterized in that an injection material pressure detection mechanism, namely an injection material pressure sensor 40, is provided near the gas injection port 26 of the heating cylinder 17. This injection material pressure sensor 40 is also connected to the controller 4, measures the injection material pressure near the gas injection port 26, i.e., the starvation zone 22, and inputs it to the controller 4. The controller 4 compares this injection material pressure with the secondary pressure to determine whether it is normal or abnormal.

[0035] In this embodiment, the injection molding machine 1 controls the amount of gas dissolved in the injection material by the pressure of the gas supplied to the heating cylinder 17. Because the screw 18, located in the starvation zone 22, has deep thread grooves and a large volume between the threads, the pressure detected by the injection material pressure sensor 40 is approximately zero when no gas is supplied. On the other hand, when gas is supplied, the pressure detected by the injection material pressure sensor 40 is approximately equal to the pressure of the supplied gas, i.e., the secondary pressure.

[0036] <Feeder>

[0037] In this embodiment, the heating cylinder 17 of the injection apparatus 3 is equipped with a feeder 44. The feeder 44 is also connected to and controlled by a controller 4, which controls the amount of injection material supplied from the hopper 45 to the heating cylinder 17. The feeder 44 is equipped with an injection material detection sensor 46, which is also connected to the controller 4. The controller 4 can use the signal from the injection material detection sensor 46 to determine whether injection material is being supplied appropriately from the feeder 44. It should be noted that the injection material detection sensor 46 can be installed on the feeder 44, or on the injection material supply port of the heating cylinder 17, or on the hopper 45. Alternatively, it can be installed in a material handling device or the like that automatically supplies injection material to the feeder 44 or the hopper 45. When the injection material detection sensor 46 is installed on the hopper 45, the material handling device, or the like, it can detect whether there is any residual injection material supplied to the feeder 44.

[0038] The injection molding machine 1 of this embodiment controls the amount of gas dissolved in the injection material by the pressure of the gas supplied to the heating cylinder 17. Because the screw 18, located in the starvation zone 22, has deep thread grooves and a large volume between the threads, the resin flowing in from the upstream first compression / metering zone 21 is depressurized, and the injection material pressure becomes approximately zero. Therefore, even lower-pressure gases that can be supplied from gas cylinders or the like can be stably supplied. The gas supplied to the heating cylinder 17 fills the starvation zone 22 of the heating cylinder 17. Since the gas acts isotropically as fluid pressure, the injection material pressure in the starvation zone 22 is approximately the same as the secondary pressure. The gas contacts the molten resin in the starvation zone 22, dissolving an amount corresponding to the gas pressure. That is, the amount of gas dissolved in the molten resin increases proportionally to the secondary pressure.

[0039] On the other hand, if the resin in the starvation zone 22 increases for some reason, causing the injection material pressure to rise, resin may overflow into the gas injection port 26, potentially preventing gas from being supplied to the heating cylinder 17. Therefore, poor gas supply caused by overflow can be detected by detecting the increase in injection material pressure.

[0040] Furthermore, if the primary pressure of the gas supplied from the gas supply source is not sufficiently high relative to the secondary pressure, the pressure of the gas in the starved zone 22 within the heating cylinder 17 will decrease due to the reduced secondary pressure and the reduced amount of gas supplied to the heating cylinder 17, resulting in a decrease in the amount of gas dissolved in the molten resin. In this case, by detecting the decrease in the injection material pressure or the primary pressure in the starved zone 22, defects caused by insufficient gas supply from the gas supply source can be detected.

[0041] On the other hand, in this embodiment, the feeder 44 is used to reduce the amount of resin material supplied. Normally, the gas supplied to the heating cylinder 17 is liquid-tightly sealed between the starvation zone 22 and the first compression / metering zone 21 by the molten resin. However, in cases where the amount of resin supplied from the feeder 44 is too low, or where there is no material (e.g., the feeder 44 is not used), there is a possibility that the seal may be temporarily or continuously broken, causing gas to flow back to the primary side. In this case, the injection material pressure indirectly decreases due to gas leakage from the starvation zone 22, and this backflow of gas can be detected.

[0042] If issues such as material overflow, reduced gas pressure, or gas backflow occur, poor molding will frequently occur. Therefore, in the injection molding machine 1 of this embodiment, the management of secondary pressure and the detection of abnormalities become important.

[0043] <Controller>

[0044] As detailed below, the injection molding machine 1 of this embodiment can detect various anomalies by comparing the injection material pressure with the secondary pressure of the gas in the controller 4. Furthermore, when an anomaly is detected, the controller 4 takes various measures corresponding to the nature of the anomaly. To detect anomalies and take measures against them, the controller 4 is equipped with various setpoints and programs. The setpoints include a secondary pressure setpoint (as a secondary pressure setpoint), first to fourth thresholds (as setpoints for judging anomalies in the injection material pressure), and first and second stabilization times. The programs include procedures for implementing alarm output, supply quantity increase control, and supply quantity decrease control; these programs are set in the controller 4.

[0045] <Control method of injection molding machine according to this embodiment>

[0046] The control method of the injection molding machine according to this embodiment will be described below. In the control method of the injection molding machine according to this embodiment, the injection material pressure detected by the injection material pressure sensor 40 is input to the controller 4. The controller 4 compares it with the secondary pressure of the gas to determine whether it is normal or abnormal and takes the necessary measures.

[0047] It should be noted that the secondary pressure compared to the injection material pressure can be either a preset secondary pressure setpoint in controller 4 or a measured secondary pressure value detected by secondary pressure gauge 42. This is because the secondary pressure setpoint and the measured secondary pressure should essentially be equal. Furthermore, the secondary pressure of the gas can also be controlled by the controller 4 as the secondary pressure setpoint. When the secondary pressure gauge 42 is not connected to the controller 4, the secondary pressure compared to the injection material pressure naturally becomes the secondary pressure setpoint. Additionally, when the secondary pressure compared to the injection material pressure is set as the secondary pressure setpoint, in... Figure 2 In the configuration of the injection device 3 shown, the secondary pressure gauge 42 is not necessary.

[0048] The controller 4 compares the injection material pressure with the secondary pressure to determine normal / abnormal conditions, using the 1st to 4th thresholds as its benchmark or as a benchmark for deciding on the measures to be taken. Figure 6 The summary shows the secondary pressure, the normal / abnormal range based on thresholds 1 to 4, and the corresponding measures taken for each state when the injection material pressure changes. The processing of controller 4 will be explained below with reference to this summary.

[0049] <Controller Processing>

[0050] like Figure 3 As shown, controller 4 transitions from the start to step S1, determining whether the injection material pressure is greater than the value obtained by adding the second threshold to the second pressure. If the injection material pressure is lower than the value obtained by adding the first threshold to the second pressure, controller 4 transitions to step S2. In step S2, controller 4 determines whether the injection material pressure is less than the value obtained by subtracting the second threshold from the second pressure. Controller 4 considers the injection material pressure to be normal if it is greater than the value obtained by subtracting the second threshold from the second pressure. That is, based on the second pressure, the range greater than the lower second threshold and less than the upper first threshold is defined as the normal pressure range for the injection material. If the injection material pressure is within the normal pressure range, controller 4 determines it to be normal and returns to the start.

[0051] In step S1, if it is determined that the injection material pressure is greater than the secondary pressure and the difference is greater than the first threshold, then controller 4 proceeds to step S3. In step S3, controller 4 checks whether the injection material pressure is greater than the secondary pressure and whether the difference is less than the third threshold. If it is greater than the third threshold, the possibility of material overflow is high. At this time, controller 4 implements stop processing SS.

[0052] In stopping SS processing, such as Figure 5As shown, in step S31, controller 4 confirms whether the opening and closing mechanism, i.e., the opening and closing valve 39, is controllable. If the opening and closing valve 39 is present, controller 4 executes step S32 to close the opening and closing valve 39, stopping the gas supply. Next, regardless of whether the opening and closing valve 39 is present, controller 4 executes step S33, waiting for the currently executing molding cycle to complete before stopping the molding cycle. It should be noted that the stop procedure SS can be executed immediately based on its cause, urgency, and whether the operation is manned or unmanned, or it can be executed after a certain delay or cycle. In addition, controller 4 can also execute the alarm procedure SB (described later) simultaneously with or before the stop procedure SS to notify the operator of the abnormality.

[0053] exist Figure 3 In step S3 of the flowchart, the controller 4 implements alarm processing SA when it determines that the difference between the injection material pressure and the secondary pressure is lower than a third threshold. In alarm processing SA, the controller 4 outputs an alarm indicating a risk of material leakage at the gas injection port 26. The alarm can be displayed on a monitor attached to the controller 4, or an alarm sound can be output from a speaker. Alternatively, it can notify the manager via email or other means.

[0054] If alarm processing SA is implemented, controller 4 proceeds to step S4. In step S4, it checks whether the feeder 44 is present and whether it is operable, i.e., whether there is a feeder control mechanism. If there is no feeder control mechanism, controller 4 implements stop processing SS. That is, controller 4 operates the on / off valve 39 to close it, stops the gas supply, and waits for the currently executing molding cycle to complete before stopping the molding cycle. If there is a feeder control mechanism, controller 4 proceeds to step S5.

[0055] In step S5, controller 4 implements a supply reduction control. The supply reduction control decreases the drive speed of feeder 44 to reduce the amount of injection material supplied to heating cylinder 17. By reducing the supply, the pressure of the injection material in the starvation zone 22 decreases. Consequently, the injection material pressure returns to the normal pressure range.

[0056] If a supply reduction control is implemented, controller 4 observes the process through step S6. That is, controller 4 monitors the injection material pressure and checks whether the injection material pressure returns to the normal pressure range within the first stabilization time. If it returns to the normal pressure range within the first stabilization time, controller 4 determines it is normal. That is, controller 4 returns the process to the beginning. However, if the injection material pressure does not return to the normal pressure range within the first stabilization time, controller 4 implements the described stop process SS.

[0057] However, regarding step S2, only the handling when the injection material pressure is determined to be within the normal pressure range is explained. The situation where the pressure exceeds the normal pressure range is explained. In step S2, if the injection material pressure is detected to be below the value obtained by subtracting the second threshold from the secondary pressure, it is determined that the injection material pressure is below the normal pressure range, and the controller 4 proceeds to step S7.

[0058] In step S7, controller 4 checks whether the injection material pressure is greater than the value obtained by subtracting the fourth threshold from the secondary pressure. If the injection material pressure is below the value obtained by subtracting the fourth threshold from the secondary pressure, the described stop procedure SS is executed. Controller 4 executes alarm procedure SB when the injection material pressure is greater than the value obtained by subtracting the fourth threshold from the secondary pressure. In alarm procedure SB, controller 4 outputs an alarm indicating a risk of gas leakage due to decreased injection material pressure or a decrease in the gas cylinder pressure. The alarm can be displayed on a monitor attached to controller 4, or an alarm sound can be output from a speaker. Alternatively, it can be sent to the administrator via email, etc.

[0059] If alarm processing SB is implemented, controller 4 proceeds to step S8. In step S8, controller 4 checks whether feeder 44 is present and whether it is operable, i.e., whether there is a feeder control mechanism. If there is no feeder control mechanism, controller 4 implements the described stop processing SS. If there is a feeder control mechanism, controller 4 proceeds to step S9.

[0060] In step S9, controller 4 implements supply increase control. Supply increase control is to increase the drive speed of feeder 44 to increase the amount of injection material supplied to heating cylinder 17. By increasing the supply of injection material, the pressure of injection material in the starvation zone 22 increases. As a result, the injection material pressure returns to the normal pressure range.

[0061] If supply increase control is implemented, controller 4 observes the process through step S10. That is, controller 4 monitors the injection material pressure and checks whether the injection material pressure returns to the normal pressure range within the second stabilization time. If it returns to the normal pressure range within the second stabilization time, controller 4 determines it is normal. That is, controller 4 returns the process to the start. However, if the injection material pressure does not return to the normal pressure range within the second stabilization time, or if the injection material pressure is below the value obtained by subtracting the second threshold from the secondary pressure, controller 4 implements the described stop process SS.

[0062] In the injection molding machine 1 of this embodiment, the supply of injection material is also checked to ensure it is normal. That is, as... Figure 4As shown, controller 4 performs step S21. Controller 4 uses injection material detection sensor 46, which serves as an injection material detection mechanism, to check at predetermined intervals whether the injection material has fallen into the heating cylinder 17. If the supply of injection material is abnormal, controller 4 performs the described stop procedure SS.

[0063] The above describes the control method for the injection molding machine according to this embodiment, explaining the use of first and second threshold values ​​for secondary pressure in order to determine whether the injection material pressure is normal or abnormal. Preferably, the first and second threshold values ​​are set to 0.1 to 1.5 MPa, and more preferably, they are set to a range of 0.2 to 1.0 MPa. Regarding the third and fourth threshold values, they can be set to values ​​that are slightly larger than the first and second threshold values.

[0064] Regarding the first and second thresholds, proportions can be used instead of specific pressure values. For example, the normal range for injection material pressure can be 95% to 110% of the secondary pressure. Using proportions for judgment in this way is essentially the same as using the first and second thresholds. That is, this is because it is equivalent to setting the first threshold to 10% of the secondary pressure and the second threshold to 5% of the secondary pressure.

[0065] Alternatively, the upper and lower limits of the normal range can be used. For example, if the secondary pressure is set to 10 MPa, the normal range can be set from 10.5 MPa to 9.5 MPa. In this case, the same results can be obtained as when using the first and second thresholds or proportions for judgment.

[0066] Furthermore, the control method for the injection molding machine of this embodiment can also be applied to situations where multiple secondary pressure setpoints are used and the pressure is varied in segments. In this case, the first and second thresholds can be set in a manner that includes the maximum and minimum values ​​of the multiple secondary pressure setpoints, or a setpoint equivalent to the first and second thresholds can be set for each secondary pressure setpoint.

[0067] As mentioned earlier, in this embodiment, the secondary pressure, which is compared with the injection material pressure, can be either a secondary pressure setpoint in the control mechanism or a measured value of the secondary pressure detected by the secondary pressure gauge 42. This is because if the starvation zone 22 of the supplied gas becomes a stable state, there is almost no difference between the two.

[0068] It should be noted that in S7 of this embodiment, the first, second, and fourth thresholds are used as the judgment criteria for alarm processing SB, i.e., the danger of gas leakage or reduced gas cylinder pressure. However, the danger of reduced gas cylinder pressure can also be judged more directly by the difference between the secondary pressure and the primary pressure. In this case, the fifth threshold is used as the judgment criteria for the difference between the primary pressure and the secondary pressure. If the difference between the primary pressure and the secondary pressure is lower than the fifth threshold, the danger of reduced gas cylinder pressure can also be alarmed. The fifth threshold can be appropriately determined according to the amount of gas used, for example, 1 MPa can be used as a reference. At this time, if the controller 4 has a gas supply source switching function, i.e., in this embodiment, the function of operating the gas cylinder opening and closing valves 31, 31 to switch the currently used gas cylinder 30 to another gas cylinder 30, then automatic gas supply source switching control can also be implemented.

[0069] The invention proposed by the inventors of this application has been specifically described above based on the embodiments. However, the invention is not limited to the described embodiments, and various modifications can be made without departing from its spirit. Furthermore, the measures can be changed depending on whether the machine is manned or unmanned. For example, when the machine is manned, the feed rate increase control and feed rate decrease control of the feeder 44 can be replaced by a policy that guides changes in molding conditions. In cases of low urgency, the stop procedure SS can be omitted, and the alarm procedure can be left for the operator to handle. The various examples described above can also be appropriately combined and implemented.

[0070] Here, the features of the embodiments of the injection molding machine and the control method of the injection molding machine for foaming of the present invention are briefly summarized and listed below [1] to

[17] .

[0071] [1] An injection molding machine (1), comprising:

[0072] Heating cylinder (17) is provided with a gas injection port (26);

[0073] The screw (18) is configured to be driven within the heating cylinder (17);

[0074] A gas supply device (28) supplies gas to the gas injection port (26);

[0075] An injection material pressure detection mechanism is located near the gas injection port (26) of the heating cylinder (17); and

[0076] Control mechanism,

[0077] In the injection molding machine (1),

[0078] The gas supply device (28) includes:

[0079] Gas supply source, which supplies gas; and

[0080] A pressure regulating mechanism that adjusts the primary pressure of the gas from the gas supply source to a secondary pressure.

[0081] The secondary pressure gas is supplied to the gas injection port (26).

[0082] The control mechanism detects abnormalities by comparing the injection material pressure detected by the injection material pressure detection mechanism with the secondary pressure.

[0083] [2] According to the injection molding machine (1) described in [1], wherein,

[0084] The normal pressure range of the injection material pressure is greater than the value obtained by subtracting the second threshold from the secondary pressure and less than the value obtained by adding the secondary pressure and the first threshold. The control mechanism detects abnormalities in the injection material pressure based on the normal pressure range.

[0085] [3] According to the injection molding machine (1) described in [2], wherein,

[0086] When the pressure of the injected material is greater than the normal pressure range and the pressure of the injected material is less than the value obtained by adding the secondary pressure and the third threshold, the control mechanism issues a danger alarm for material leakage from the gas injection port (26).

[0087] [4] According to the injection molding machine (1) described in [2], wherein,

[0088] The heating cylinder (17) is equipped with a feeder (44) for adjusting the supply of injection material.

[0089] When the pressure of the injection material is greater than the normal pressure range and the pressure of the injection material is less than the value obtained by adding the secondary pressure and the third threshold, the control mechanism controls the feeder (44) to implement a supply reduction control that reduces the supply amount of the injection material.

[0090] [5] According to the injection molding machine (1) described in [4], wherein,

[0091] During the first stabilization period following the start of the supply reduction control, if the injection material pressure continues to exceed the normal pressure range, the control mechanism performs a stop procedure for the molding cycle.

[0092] [6] According to the injection molding machine (1) described in [2], wherein,

[0093] When the injection material pressure is above the value obtained by adding the secondary pressure and the third threshold, the control mechanism performs a stop process for the molding cycle.

[0094] [7] According to the injection molding machine (1) described in [2], wherein,

[0095] When the pressure of the injection material is less than the normal pressure range and the pressure of the injection material is greater than the value obtained by subtracting the fourth threshold from the secondary pressure, the control mechanism issues a danger alarm for gas leakage or reduced supply gas pressure at the gas injection port (26).

[0096] [8] According to the injection molding machine (1) described in [2], wherein,

[0097] The heating cylinder (17) is equipped with a feeder (44) for adjusting the supply of injection material.

[0098] When the pressure of the injection material is less than the normal pressure range and the pressure of the injection material is greater than the value obtained by subtracting the fourth threshold from the secondary pressure, the control mechanism controls the feeder (44) to implement a supply increase control that increases the supply amount of the injection material.

[0099] [9] According to the injection molding machine (1) described in [8], wherein,

[0100] During the second stabilization period following the start of the supply increase control, if the injection material pressure is temporarily and continuously below the normal pressure range, the control mechanism performs a stop procedure for the molding cycle.

[0101]

[10] According to the injection molding machine (1) described in [2], wherein,

[0102] When the injection material pressure is below the value obtained by subtracting the fourth threshold from the secondary pressure, the control mechanism performs a stop process for the molding cycle.

[0103]

[11] The injection molding machine (1) according to any one of [1] to

[10] , wherein,

[0104] The secondary pressure compared with the injection material pressure is a secondary pressure setting value set in the control mechanism.

[0105]

[12] The injection molding machine (1) according to any one of [1] to

[10] , wherein,

[0106] The gas supply device (28) is equipped with a secondary pressure detection mechanism for detecting the secondary pressure.

[0107] The secondary pressure compared with the injection material pressure is the secondary pressure measurement value detected by the secondary pressure detection mechanism.

[0108]

[13] The injection molding machine (1) according to any one of [1] to

[12] , wherein,

[0109] The injection molding machine (1) is equipped with an injection material detection mechanism to confirm the supply of injection material to the heating cylinder (17).

[0110] When the injection material is interrupted and the injection material is detected to be exhausted, the control mechanism performs a stop process for the molding cycle.

[0111]

[14] An injection molding machine (1) according to any one of [5], [6], [9],

[10] , and

[13] , wherein,

[0112] The stopping process of the molding cycle is a process that stops the molding cycle while waiting for the ongoing molding cycle to complete.

[0113]

[15] An injection molding machine (1) according to any one of [5], [6], [9],

[10] , and

[13] , wherein,

[0114] The gas supply device (28) is equipped with an on / off valve (31).

[0115] The process of stopping the molding cycle is to close the on / off valve (31) and wait for the ongoing molding cycle to complete, thereby stopping the molding cycle.

[0116]

[16] The injection molding machine (1) according to any one of [1] to

[15] , wherein,

[0117] The gas supply device (28) is equipped with a primary pressure detection mechanism for detecting the primary pressure of the gas from the gas supply source.

[0118] The control mechanism compares the difference between the primary pressure and the secondary pressure, and detects a decrease in the pressure of the gas supply source.

[0119] If a decrease in pressure is detected in the gas supply source, an alarm is issued urging the replacement of the gas supply source.

[0120]

[17] A control method for an injection molding machine, wherein the injection molding machine comprises:

[0121] Heating cylinder (17) is provided with a gas injection port (26);

[0122] The screw (18) is configured to be driven within the heating cylinder (17);

[0123] Gas supply device (28), which supplies gas to the gas injection port (26); and

[0124] The injection material pressure detection mechanism is located near the gas injection port (26) of the heating cylinder (17).

[0125] The gas supply device (28) includes:

[0126] Gas supply source; and

[0127] A pressure regulating mechanism that adjusts the primary pressure of the gas from the gas supply source to a secondary pressure.

[0128] In the control methods of injection molding machines

[0129] The pressure of the injection material is detected by the injection material pressure detection mechanism, and the secondary pressure is compared with the injection material pressure to detect abnormalities.

[0130] The present invention has been described in detail with reference to specific embodiments, but it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention.

[0131] This application is based on Japanese Patent Application No. 2020-204670, filed on December 10, 2020, the contents of which are incorporated herein by reference.

[0132] Industrial availability

[0133] According to the present invention, it is possible to quickly detect early signs of material overflow, abnormal supply of injection material, etc., and prevent the production of defective products. This invention, having this effect, is useful for injection molding machines used in foam molding and for control methods of injection molding machines.

[0134] Explanation of reference numerals in the attached figures

[0135] 1 Injection molding machine 2 Mold clamping device

[0136] 3. Injection device 4. Controller

[0137] 17 Heating cylinder 18 Screw

[0138] 20 Supply Range 21 First Compression Range

[0139] 22 Hunger Zone 23 Second Compression Zone

[0140] 26 Gas injection port 28 Gas supply device

[0141] 30 Gas cylinder 31 Gas cylinder opening / closing valve

[0142] 33 Primary gas line 34 Pressure reducing valve

[0143] 36 Secondary gas pipe; 38 Check valve

[0144] 39 On / off valve 40 Injection material pressure sensor

[0145] 41 Primary pressure gauge 42 Secondary pressure gauge

[0146] 44 Feeder 45 Hopper

[0147] 46 Injection Material Detection Sensor

Claims

1. An injection molding machine, characterized in that, include: A heating cylinder, which is equipped with a gas injection port; A screw, configured to be driven within the heating cylinder; A gas supply device that supplies gas to the gas injection port; An injection material pressure detection mechanism is located near the gas injection port of the heating cylinder; as well as Control mechanism, In the injection molding machine, the heating cylinder is divided based on the shape of the screw into a first compression / metering zone on the upstream side where the injection material is melted and compressed, a starvation zone on the downstream side where the pressure of the molten injection material decreases, and a second compression / metering zone on the downstream side. The gas injection port and the injection material pressure detection mechanism are located in the starvation zone. The starvation zone is a space filled with gas supplied from the gas inlet. The gas supply device includes: A gas supply source that supplies gas; A pressure regulating mechanism that reduces the primary pressure of the gas from the gas supply source to a secondary pressure; The check valve is located downstream of the pressure regulating mechanism. The gas supply device supplies the secondary pressurized gas to the gas injection port. The control mechanism has a first threshold in the range of 0.1 to 1.5 MPa and a second threshold in the same range of 0.1 to 1.5 MPa. The pressure range that is greater than the value obtained by subtracting the second threshold from the secondary pressure and less than the value obtained by adding the secondary pressure and the first threshold is defined as the normal pressure range. The abnormality of the injection material pressure is detected based on whether the injection material pressure detected by the injection material pressure detection mechanism falls within the normal pressure range.

2. The injection molding machine according to claim 1, characterized in that, When the pressure of the injected material is greater than the normal pressure range and less than the value obtained by adding the secondary pressure and the third threshold which is greater than the first threshold, the control mechanism issues a danger alarm for material leakage at the gas injection port.

3. The injection molding machine according to claim 2, characterized in that, The heating cylinder is equipped with a feeder that adjusts the supply of injection material. When the injection material pressure is greater than the normal pressure range and less than the value obtained by adding the secondary pressure and the third threshold, the control mechanism implements a supply reduction control to control the feeder to reduce the supply of injection material.

4. The injection molding machine according to claim 3, characterized in that, During the first stabilization period following the start of the supply reduction control, if the injection material pressure continues to exceed the normal pressure range, the control mechanism performs a stop procedure for the molding cycle.

5. The injection molding machine according to claim 2, characterized in that, When the injection material pressure is above the value obtained by adding the secondary pressure and the third threshold, the control mechanism performs a stop process for the molding cycle.

6. The injection molding machine according to claim 1, characterized in that, The control mechanism has a fourth threshold greater than the second threshold. When the injection material pressure is less than the normal pressure range and the injection material pressure is greater than the value obtained by subtracting the fourth threshold from the secondary pressure, the control mechanism issues a danger alarm for gas leakage or reduced supply gas pressure at the gas injection port.

7. The injection molding machine according to claim 1, characterized in that, The heating cylinder is equipped with a feeder that adjusts the supply of injection material. The control mechanism has a fourth threshold greater than the second threshold. When the injection material pressure is less than the normal pressure range and the injection material pressure is greater than the value obtained by subtracting the fourth threshold from the secondary pressure, the control mechanism implements a supply increase control to control the feeder to increase the supply of injection material.

8. The injection molding machine according to claim 7, characterized in that, During the second stabilization period, which is a predetermined time from the start of the supply increase control, if the injection material pressure is temporarily and continuously lower than the normal pressure range, the control mechanism performs a stop process for the molding cycle.

9. The injection molding machine according to claim 1, characterized in that, The control mechanism has a fourth threshold greater than the second threshold, and when the injection material pressure is below the value obtained by subtracting the fourth threshold from the secondary pressure, the control mechanism performs a stop process for the molding cycle.

10. The injection molding machine according to any one of claims 1 to 9, characterized in that, The secondary pressure compared with the injection material pressure is a secondary pressure setting value set in the control mechanism.

11. The injection molding machine according to any one of claims 1 to 9, characterized in that, The gas supply device includes a secondary pressure detection mechanism for detecting the secondary pressure. The secondary pressure compared with the injection material pressure is the secondary pressure measurement value detected by the secondary pressure detection mechanism.

12. The injection molding machine according to any one of claims 1 to 9, characterized in that, The injection molding machine is equipped with an injection material detection mechanism to confirm the supply of injection material to the heating cylinder. When the injection material is interrupted and the injection material is detected to be exhausted, the control mechanism performs a stop process for the molding cycle.

13. The injection molding machine according to any one of claims 4, 5, 8, and 9, characterized in that, The stopping process of the molding cycle is a process that stops the molding cycle while waiting for the ongoing molding cycle to complete.

14. The injection molding machine according to any one of claims 4, 5, 8, and 9, characterized in that, The gas supply device is equipped with an on / off valve. The process of stopping the molding cycle is to close the on / off valve and wait for the ongoing molding cycle to complete, thereby stopping the molding cycle.

15. The injection molding machine according to any one of claims 1 to 9, characterized in that, The gas supply device includes a primary pressure detection mechanism for detecting the primary pressure of the gas from the gas supply source. The control mechanism compares the difference between the primary pressure and the secondary pressure, and detects a decrease in the pressure of the gas supply source. If a decrease in pressure is detected in the gas supply source, an alarm is issued urging the replacement of the gas supply source.

16. A control method for an injection molding machine, characterized in that, The injection molding machine includes: A heating cylinder, which is equipped with a gas injection port; A screw, configured to be driven within the heating cylinder; A gas supply device that supplies gas to the gas injection port; and An injection material pressure detection mechanism is located near the gas injection port of the heating cylinder. In the injection molding machine, the heating cylinder is divided based on the shape of the screw into a first compression / metering zone on the upstream side where the injection material is melted and compressed, a starvation zone on the downstream side where the pressure of the molten injection material decreases, and a second compression / metering zone on the downstream side. The gas injection port and the injection material pressure detection mechanism are located in the starvation zone. The gas supply device includes: Gas supply source; A pressure regulating mechanism that reduces the primary pressure of the gas from the gas supply source to a secondary pressure; and The check valve is located downstream of the pressure regulating mechanism. The control method sets a first threshold in the range of 0.1 to 1.5 MPa and a second threshold in the same range. The pressure range that is greater than the value obtained by subtracting the second threshold from the secondary pressure and less than the value obtained by adding the secondary pressure and the first threshold is defined as the normal pressure range. In the starvation interval, when the heating cylinder is filled with gas supplied from the gas injection port, the injection material pressure detection mechanism is used to detect the injection material pressure. The abnormality of the injection material pressure is detected based on whether the injection material pressure falls within the normal pressure range.

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