JP7368158B2 - Gas replacement method and device for injection molding machine - Google Patents

Description

The present invention relates to a gas replacement method and apparatus for an injection molding machine that replaces gas in a screw cylinder of an injection molding machine.

Injection molding is currently the most popular method for manufacturing plastic resin products. An injection molding machine that performs the injection molding method described above is a device that heats and melts a plastic material inside the device, pressurizes the molten material, injects it into a mold, and then cools and solidifies it to obtain a molded product.

The injection molding machine has a hopper for storing and supplying the resin material, a heater for heating and melting the resin material, a screw/cylinder that supplies the resin material under pressure, and injecting the molten resin material into the mold. It consists of a jet nozzle, etc.

Since the injection molding machine heats and melts the resin material inside the screw cylinder, the resin material is oxidized (burned) by oxygen in the air. This causes problems such as the resin burning inside the molding machine or the burned resin getting mixed into the molded product, resulting in defective products.

In order to suppress the above phenomenon, measures have been taken to replace the internal atmosphere of the screw cylinder by injecting an inert gas (nitrogen, argon, etc.) from the hopper into the screw cylinder as a purge gas.

The applicant is aware of the following Patent Documents 1 and 2 as prior art documents related to such gas replacement technology.

Japanese Patent Application Publication No. 3-248826 Japanese Patent Application Publication No. 9-10910

The above-mentioned Patent Document 1 relates to a "gas replacement device for an injection molding machine" and includes the following description.
[2. Scope of claims]
(1) A gas replacement device for an injection molding machine, characterized in that the resin injection section of the injection molding machine for injection molding a thermoplastic resin is provided with a switching valve for gas suction, jetting, and resin injection.
[Page 2, upper left column, lines 18 to 20]
Reference numeral 1 denotes a nozzle which is a resin injection part of an injection molding machine, and a gas replacement device 3 of the present invention is installed at the tip of this nozzle 1 via a mounting frame 2.
[Page 2, upper right column, lines 7 to 10]
Further, the mounting nozzle body 5 is equipped with a switching valve 9 for gas suction, ejection, and resin injection, which is rotatable via a rotary drive shaft 8 of a motor 7 fixed to the mounting frame 2.
[Bulletin page 2, lower right column, lines 8 to 12]
Thereafter, the gas suction and ejection switching valve 13 is operated to connect the end 12b of the conduit 12 to the conduit 15, and the gas suction and ejection hole 11 is connected to the rotary pump 16. Suction the air inside the mold.
[Page 2, lower right column, line 17 to page 3, upper left column, line 9]
Therefore, after the suction process via the rotary pump 16 is completed, the switching valve 13 is switched in conjunction with the stoppage of the rotary pump 16, the conduit 12 is connected to the inert gas blowing device 14, and the device 14 is activated to perform the process. At this point, the inert gas stored in the device 14 is sucked and ejected into the mold through the ejection hole 11 and the nozzle hole 4 to replace the inside of the cavity with the inert gas.
After stopping the inert gas injection device 14, the motor 7 is operated again to rotate the switching valve 9, and the resin injection hole 10 of the switching valve 9 is again aligned with the nozzle holes 4 and 6, so that both nozzles are After communicating the holes 4 and 6, resin is injected from the nozzle 1.

The above-mentioned Patent Document 2 relates to "injection molding method and injection molding machine for light alloy injection material" and includes the following description.
[0005]
...Even during molding as described above, the inside of the hopper is continuously or intermittently kept in an inert gas atmosphere. By making the inside of the hopper an inert gas atmosphere, the screw supply section under the hopper is also made to have an inert gas atmosphere. ...
[0012]
During the preparation period for starting molding, the inert gas replacement jig 50 is slid by a drive device, for example, a hydraulic piston mechanism (not shown), so that the opening 52 is aligned with the injection nozzle 3 and the shaft, as shown in FIG. in a first position aligned with the direction. Pressure oil is then supplied to the hydraulic chamber 8 on the piston rod side of the piston/cylinder device 5. Then, the injection nozzle 3 touches the opening 52 of the inert gas replacement jig 50. Then, the main valve 42' of the second pressure vessel 41' is opened. Then, the second gas supply conduit 46 supplies the inert gas adjusted to a predetermined pressure by the pressure regulator 48 from the gas passage 51 of the inert gas replacement jig 50 to the opening 52 . As a result, the tip of the injection nozzle 3 is placed in an inert gas atmosphere. Furthermore, the main valve 42 of the first pressure vessel 41 is also opened. Then, the inert gas, which has been adjusted to a predetermined pressure by the pressure regulator 44 and controlled to a predetermined flow rate by the flow regulator 45, is supplied to the hopper 20 from the branch pipes 43' and 43'' through the first gas supply pipe 43. As a result, the inside of the main body 21 of the hopper 20, the vicinity of the supply port 24, and the screw supply section 16 below the hopper 20 are placed in an inert gas atmosphere.

In the technique disclosed in Patent Document 1, the tip of the nozzle 1 is equipped with a gas replacement device 3 having a complicated structure, and after sucking the inside of the cavity of the mold, inert gas is introduced to perform gas replacement. In this way, even if only the inside of the mold cavity is replaced with gas, the resin material from the hopper is supplied to the nozzle 1 together with air. Therefore, when the resin melts within the nozzle 1, it is impossible to prevent the resin from burning which occurs in the melted resin. In other words, it cannot fundamentally solve the problems of resin burning and defective products caused by burning of the resin heated and melted inside the nozzle 1 (screw cylinder).

The technique disclosed in Patent Document 2 supplies inert gas to the main body 21 of the hopper 20 and the vicinity of the supply port 24 . However, this only places the screw supply section 16 below the hopper 20 in an inert gas atmosphere. For this reason, in Patent Document 2, an inert gas replacement jig 50 is also provided at the tip of the injection nozzle 3, and the tip of the injection nozzle 3 is placed in an inert gas atmosphere. In other words, simply supplying inert gas to the main body 21 of the hopper 20 and the vicinity of the supply port 24 cannot sufficiently prevent resin burning that occurs in the melted resin. A gas replacement jig 50 is provided. As described above, there is a problem that the device becomes complicated and its control also becomes complicated.

As described above, in the conventional gas replacement method, inert gas is injected from the hopper section to replace the atmosphere inside the hopper and the cylinder section located below the hopper. However, since the injection molding machine does not have a gas vent in the cylinder section, the purge gas injected from the hopper section cannot pass through the cylinder section. The purge gas passes only through the end of the cylinder part from the injection point, and then exits to the upper part of the hopper in a U-turn. As described above, in the conventional method, purge does not function effectively, and it takes a long time to replace the atmosphere in the cylinder. For this reason, the injection of purge gas is continued even while the injection molding machine is not operating.

The present invention has been made with the following objectives in order to solve the above problems.
To provide a gas replacement method and device for an injection molding machine that can efficiently replace gas in a screw cylinder of the injection molding machine with a simple device and control.

In order to achieve the above object, the gas replacement method for an injection molding machine according to claim 1 employs the following configuration.
In an injection molding machine equipped with a heating melting section that heats and melts the injection material supplied from the supply means, and a screw cylinder that has a screw that extrudes the injection material melted in the heating melting section toward an injection hole at the tip. , a method for replacing gas in the screw cylinder, comprising:
It is further equipped with a jet nozzle that jets inert gas,
The jetting nozzle jets out an inert gas at a side closer to the supplying means than the heating and melting part in the screw cylinder,
The ejection nozzle ejects the inert gas so that the nozzle opening faces toward the injection hole of the screw cylinder , and intermittently switches the ejection flow rate of the inert gas .

The method for replacing gas in an injection molding machine according to claim 2 employs the following configuration in addition to the configuration described in claim 1.
The jet nozzle is configured such that the jet direction of the inert gas jetted from the nozzle opening has an inclination angle with respect to the axis of the screw cylinder.

The gas replacement method for an injection molding machine according to claim 3 employs the following configuration in addition to the configuration described in claim 3.
When the above-mentioned jet nozzle intermittently switches the jetting flow rate of the inert gas, the time when the jetting flow rate of the inert gas is small is set to be equal to or greater than the time when the jetting flow rate of the inert gas is high. .

In order to achieve the above object, a gas replacement device for an injection molding machine according to a fourth aspect of the present invention employs the following configuration.
In an injection molding machine equipped with a heating melting section that heats and melts the injection material supplied from the supply means, and a screw cylinder that has a screw that extrudes the injection material melted in the heating melting section toward an injection hole at the tip. , a device for replacing gas in the screw cylinder,
It is further equipped with a jet nozzle that jets inert gas,
The jetting nozzle jets out an inert gas at a side closer to the supplying means than the heating and melting part in the screw cylinder,
The ejection nozzle is configured such that the nozzle opening ejects the inert gas toward the injection hole side of the screw cylinder and intermittently switches the ejection flow rate of the inert gas .

A gas replacement device for an injection molding machine according to claim 5 employs the following configuration in addition to the configuration described in claim 5.
The jet nozzle is configured such that the jet direction of the inert gas jetted from the nozzle opening has an inclination angle with respect to the axis of the screw cylinder.

The gas replacement method for an injection molding machine according to claim 6 employs the following configuration in addition to the configuration described in claim 4 or 5 .
When the above-mentioned jet nozzle intermittently switches the jetting flow rate of the inert gas, the time when the jetting flow rate of the inert gas is small is set to be equal to or greater than the time when the jetting flow rate of the inert gas is high. .

A method for replacing gas in an injection molding machine according to a first aspect of the present invention is a method for replacing gas in the screw cylinder in an injection molding machine equipped with a screw cylinder. The screw cylinder has a heating melting section and a screw. The heating and melting section heats and melts the injection material supplied from the supply means. The screw pushes out the injection material melted in the heating melting section toward the injection hole at the tip. The method of the present invention further includes an ejection nozzle that ejects inert gas. The ejection nozzle ejects the inert gas closer to the supply means than the heating and melting portion of the screw cylinder. The nozzle opening of the ejection nozzle ejects the inert gas toward the injection hole side of the screw cylinder.
For this reason, the air around the injection material supplied from the supply means and before it is melted is replaced with inert gas, and the injection material in that state is melted, extruded, and injected. Therefore, compared to the conventional method, the inside of the screw cylinder can be efficiently replaced with gas using a simple device and control, and it is possible to fundamentally solve the problem of burning inside the screw cylinder due to burnt resin and the occurrence of defective products. Furthermore, the ejection nozzle intermittently switches the ejection flow rate of the inert gas. By intermittently switching the injection flow rate of the inert gas, the inert gas is fed into the screw cylinder at a large injection flow rate, and the gas in the screw cylinder is discharged while the injection flow rate is small. For example, if the inert gas is ejected and stopped intermittently, the inert gas is sent into the screw cylinder by the inert gas ejection, and the gas in the screw cylinder is exhausted while the ejection is stopped. This allows effective gas replacement.

In the gas replacement method for an injection molding machine according to a second aspect of the present invention, the jetting direction of the inert gas jetted from the nozzle opening of the jetting nozzle has an inclination angle with respect to the axis of the screw cylinder.
When the inert gas is ejected at a predetermined angle with respect to the axis of the screw cylinder, the gas inside the screw cylinder is pushed by the ejected inert gas and discharged. This allows effective gas replacement.

In the gas replacement method for an injection molding machine according to claim 3 , when the jet nozzle intermittently switches the jetting flow rate of the inert gas, the time when the jetting flow rate of the inert gas is low is the time when the jetting flow rate of the inert gas is high. It is set to be equal to or greater than time.
The gas in the screw cylinder is discharged during the time when the ejection flow rate is small, and the inert gas is fed into the screw cylinder during the subsequent time when the ejection flow rate is large. This allows effective gas replacement.

A gas replacement device for an injection molding machine according to a fourth aspect of the present invention is a device for replacing gas in the screw cylinder in an injection molding machine equipped with a screw cylinder. The screw cylinder has a heating melting section and a screw. The heating and melting section heats and melts the injection material supplied from the supply means. The screw pushes out the injection material melted in the heating melting section toward the injection hole at the tip. The device of the present invention further includes an ejection nozzle that ejects inert gas. The ejection nozzle ejects the inert gas closer to the supply means than the heating and melting portion of the screw cylinder. The nozzle opening of the ejection nozzle ejects the inert gas toward the injection hole side of the screw cylinder.
For this reason, the air around the injection material supplied from the supply means and before it is melted is replaced with inert gas, and the injection material in that state is melted, extruded, and injected. Therefore, compared to the conventional method, the inside of the screw cylinder can be efficiently replaced with gas using a simple device and control, and it is possible to fundamentally solve the problem of burning inside the screw cylinder due to burnt resin and the occurrence of defective products. Furthermore, the ejection nozzle intermittently switches the ejection flow rate of the inert gas. By intermittently switching the injection flow rate of the inert gas, the inert gas is fed into the screw cylinder at a large injection flow rate, and the gas in the screw cylinder is discharged while the injection flow rate is small. For example, if the inert gas is ejected and stopped intermittently, the inert gas is sent into the screw cylinder by the inert gas ejection, and the gas in the screw cylinder is exhausted while the ejection is stopped. This allows effective gas replacement.

In the gas replacement device for an injection molding machine according to a fifth aspect of the present invention, the jetting direction of the inert gas jetted from the nozzle opening of the jetting nozzle has an inclination angle with respect to the axis of the screw cylinder.
When the inert gas is ejected at a predetermined angle with respect to the axis of the screw cylinder, the gas inside the screw cylinder is pushed by the ejected inert gas and discharged. This allows effective gas replacement.

In the gas replacement device for an injection molding machine according to claim 6 , when the jetting nozzle intermittently switches the jetting flow rate of the inert gas, the time when the jetting flow rate of the inert gas is small is the time when the jetting flow rate of the inert gas is high. It is set to be equal to or greater than time.
The gas in the screw cylinder is discharged during the time when the ejection flow rate is small, and the inert gas is fed into the screw cylinder during the subsequent time when the ejection flow rate is large. This allows effective gas replacement.

FIG. 1 is a configuration diagram illustrating a gas replacement device for an injection molding machine according to an embodiment of the present invention. It is a diagram explaining the gas replacement method of the injection molding machine of the said embodiment. FIG. 2 is a configuration diagram illustrating a test device for a demonstration test conducted as an example. It is a figure explaining the above-mentioned test device. It is a schematic diagram explaining the ejection flow rate change of the 2nd test.

Next, a mode for carrying out the present invention will be explained.

〔overview〕
FIG. 1 is a configuration diagram illustrating a gas replacement device for an injection molding machine according to an embodiment of the present invention.
This embodiment is an apparatus and method for replacing gas in the screw cylinder 10 in an injection molding machine equipped with the screw cylinder 10.

[Screw cylinder 10]
The screw cylinder 10 has a cylindrical cylinder body 10A having a tapered tip and extending back and forth. An injection hole 12 through which heated and melted injection material is injected is formed at the tip of the cylinder body 10A. The screw cylinder 10 has a heating melting section 20 and a screw 30.

[Heat melting section 20]
The heating and melting section 20 is for heating and melting the injection material (not shown) supplied from the supply means 11. The heating and melting section 20 is configured by providing a plurality of heaters 21 on the outer periphery of the tip side of the cylinder body 10A. The cylinder body 10A is heated by the heater 21, and the injection material filled inside is heated and melted.

[Screw 30]
The screw 30 is for extruding the injection material melted in the heating melting section 20 toward the injection hole 12 at the tip. The screw 30 is inserted into the cylinder body 10A so as to be coaxial with the cylinder body 10A. The tip of the screw 30 is located near the tapered tip of the cylinder body 10A. The rear end of the screw 30 is connected to a motor (not shown). The screw 30 is provided with a flange 31 for preventing the injection material from leaking from the rear end opening of the cylinder body 10. A helical protrusion 32 is formed on the outer periphery of the screw 30 on the distal end side of the flange 31 for feeding the injection material toward the distal end side.

[Supply means 11]
The supply means 11 is for supplying temporarily stored injection material into the screw cylinder 10. In this example, the supply means 11 is formed to include a hopper section 11A and a chute section 11B. The hopper section 11A has an upwardly expanding funnel shape, and receives and stores the injection material. The chute portion 11B is a tubular body that connects the lower end opening 13 of the hopper portion 11A and the supply port 14 formed in the cylinder body 10A.

The supply port 14 of the cylinder body 10A is formed closer to the base than the heating and melting section 20. That is, the supply port 14 is provided closer to the base of the screw cylinder 10 than the heating melting part 20 and closer to the tip than the flange 31 of the screw 30. New injection material is supplied into the screw cylinder 10 from the supply port 14 .

[Injection material]
The injection material may be a resin material such as a thermoplastic resin or a metal material such as a light alloy. The above-mentioned injection material is supplied in the form of pellets to the hopper section 11A of the supply means 11. The injection material passes through the chute section 11B in pellet form and is supplied into the screw cylinder 10. In the screw cylinder 10, the injection material is gradually sent toward the distal end side by the rotation of the screw 30, and when it reaches the heating melting section 20, it is heated and melted. The molten injection material is injected from the injection hole 12 and injected into the cavity of a mold (not shown).

[Blowout nozzle 40]
This embodiment further includes an ejection nozzle 40 that ejects inert gas.
The ejection nozzle 40 ejects the inert gas on the supply means 11 side of the screw cylinder 10 relative to the heating and melting section 20 . The nozzle opening of the ejection nozzle 40 ejects the inert gas toward the injection hole 12 side of the screw cylinder 10 . In this example, the ejection nozzle 40 is configured such that the ejection direction of the inert gas ejected from the nozzle opening 41 has an inclination angle with respect to the axis of the screw cylinder 10.

Inert gas is supplied to the jet nozzle 40 from an inert gas supply source (not shown). As the inert gas, nitrogen gas or argon gas can be used.

In this example, the jet nozzle 40 is arranged within the chute portion 11B of the supply means 11. The ejection nozzle 40 in the illustrated example is arranged to extend vertically within the chute portion 11B, and the lower tip is bent at a predetermined angle of inclination, so that inert gas is ejected from the nozzle opening 41 at the tip. , is ejected in an ejection direction having an inclination angle with respect to the axis of the screw cylinder 10.

The above-mentioned inclination angle can be set to, for example, an angle greater than 0° and less than or equal to about 60°.

Preferably, the ejection nozzle 40 changes the ejection flow rate of the inert gas intermittently. Specifically, this can be achieved by controlling the opening and closing of an on-off valve 42 provided in an introduction path for introducing inert gas into the jet nozzle 40. In the figure, reference numeral 43 indicates a control section 43 that controls the on-off valve 42.

FIG. 2 is a diagram illustrating an example of a gas replacement method for the injection molding machine of the above embodiment. Specifically, a change in the ejection flow rate when inert gas is ejected from the ejection nozzle 40 is shown. The horizontal axis is the elapsed time, and the vertical axis is the flow rate.

In this example, the opening/closing control of the on-off valve 42 is an on/off control in which the valve is opened and closed all at once, rather than gradually opening and closing the valve. Therefore, when the valve is opened, the flow rate suddenly increases at a steep rate of increase and becomes a constant flow rate, and when the valve is closed, the flow rate immediately becomes zero.

When the jet nozzle 40 intermittently switches the inert gas jet flow rate, the time TS during which the inert gas jet flow rate is small is set to be equal to or greater than the time TO when the inert gas jet flow rate is large. It is preferable to do so. For example, the TS can be 1.5 times or more the TO. Further, the TS can be set to 4 to 5 times or less than the TO. Preferably, the above-mentioned TS can be set to 2 times or more and 3 times or less of the above-mentioned TO. If TS is shorter than TO, the gas in the screw cylinder 10 will be difficult to discharge, and there is a possibility that the replacement efficiency will not be improved.

The TO can be set to, for example, 1 to 2 seconds. As described above, the TS can be set to 1.5 times or more and 4 to 5 times or less than the TO.

[Effects of embodiment]

The embodiment described above is a method and apparatus for replacing gas in the screw cylinder 10 in an injection molding machine equipped with the screw cylinder 10. The screw cylinder 10 has a heating melting section 20 and a screw 30. The heating and melting section 20 heats and melts the injection material supplied from the supply means 11. The screw 30 pushes out the injection material melted in the heating melting section 20 toward the injection hole 12 at the tip. This embodiment further includes an ejection nozzle 40 that ejects inert gas. The ejection nozzle 40 ejects the inert gas on the supply means 11 side of the screw cylinder 10 relative to the heating and melting section 20 . The nozzle opening 41 of the ejection nozzle 40 ejects the inert gas toward the injection hole 12 side of the screw cylinder 10 .
For this reason, the air around the injection material supplied from the supply means 11 and before it is melted is replaced with inert gas, and the injection material in that state is melted, extruded, and injected. Therefore, compared to the prior art, the inside of the screw cylinder 10 can be efficiently replaced with gas using a simpler device and control, and the problem of seizure inside the screw cylinder 10 due to burnt resin and the occurrence of defective products can be fundamentally solved.

In the above embodiment, the direction in which the inert gas is ejected from the nozzle opening 41 of the ejection nozzle 40 has an inclination angle with respect to the axis of the screw cylinder 10 .
When the inert gas is ejected at a predetermined angle with respect to the axis of the screw cylinder 10, the gas inside the screw cylinder 10 is pushed by the ejected inert gas and discharged. This allows effective gas replacement.

In the embodiment described above, the ejection nozzle 40 intermittently switches the ejection flow rate of the inert gas.
By intermittently switching the ejection flow rate of the inert gas, the inert gas is fed into the screw cylinder 10 at a large ejection flow rate, and the gas in the screw cylinder 10 is discharged while the ejection flow rate is small. For example, if the injection and stop of the inert gas are repeated intermittently, the inert gas is sent into the screw cylinder 10 by the injection of the inert gas, and the gas in the screw cylinder 10 is exhausted while the injection is stopped. Ru. This allows effective gas replacement.

In the above embodiment, when the jet nozzle 40 intermittently switches the jet flow rate of the inert gas, the time TS of the small jet flow of the inert gas is equal to or equal to the time TO of the high jet flow of the inert gas. It is set to be more than that.
The gas in the screw cylinder 10 is discharged during the time TS when the ejection flow rate is small, and the inert gas is fed into the screw cylinder 10 during the subsequent time TO when the ejection flow rate is large. This allows effective gas replacement.

〔Example〕
▽Testing device FIG. 3 is a configuration diagram illustrating a testing device for a demonstration test conducted as an example.
In this test device, a model cylinder 50 was prepared in which the above-described cylinder body 10A and chute portion 11B were modeled using resin pipe material. The model cylinder 50 has a cylinder model section 50A corresponding to the cylinder body 10A, and a chute model section 50B corresponding to the chute section 11B.

FIG. 4 is a diagram illustrating the above-mentioned test apparatus, showing details of the model cylinder 50. (A) is the first example, and (B) is the second example.

Both the cylinder model section 50A and the chute model section 50B were created using resin pipes cut into predetermined lengths. The chute model section 50B was joined to the root side of the cylinder model section 50A at an angle of 90°. The tip of the cylinder model portion 50A was closed with a tip cap 51, and the root end of the cylinder model portion 50A was also closed with a root cap 52. The upper opening of the chute model section 50B was closed with a plug 53 equipped with an exhaust pipe 55.

The plug 53 was provided with a nozzle pipe corresponding to the jet nozzle 40. The first example in FIG. 4(A) is a first nozzle pipe 54A, and the second example in FIG. 4(B) is a second nozzle pipe 54B.

In the first nozzle pipe 54A of the first example shown in FIG. 4(A), the tip was bent at 45 degrees so that the inert gas jet direction was directed toward the tip of the cylinder model portion 50A.
In the second nozzle pipe 54B of the second example shown in FIG. 4(B), the direction in which the inert gas is ejected is perpendicular to the axis of the cylinder model portion 50A.

Returning to FIG. 3, nitrogen gas is introduced into the nozzle pipe as an inert gas from a nitrogen gas cylinder 61. The nitrogen gas cylinder 61 is replenished with nitrogen gas from the nitrogen gas production device 65. A flow rate controller 63 and an on-off valve 64 were connected in parallel to the nitrogen gas introduction pipe 62. The on-off valve 64 corresponds to the on-off valve 42 in the apparatus shown in FIG. The flow rate controller 63 was used for continuous ejection of nitrogen gas from the nozzle pipe, and the on-off valve 64 was used for intermittent ejection of nitrogen gas from the nozzle pipe.

The cylinder model portion 50A was provided with a tip port 72 near the tip, and an intermediate port 71 in the middle portion between the tip and the base. A sampling pump 73 and an oxygen concentration meter 74 are connected to the intermediate port 71, and a purge line 75 is connected to the sampling pump 73 so as to measure the oxygen concentration of the gas sampled from the cylinder model section 50A. This made it possible to purge the oxygen concentration meter 74 with nitrogen. The oxygen concentration of the gas sampled from the intermediate port 71 was measured with an oxygen concentration meter 74, and gas replacement was evaluated. An air purge line 77 and an air compressor 76 are connected to the tip port 72 to enable purging with air inside the cylinder model portion 50A. Each time one measurement was completed, the inside of the cylinder model section 50A was purged with air to reset the state.

First Test First, after air was introduced into the cylinder model section 50A, nitrogen gas was ejected from the nozzle pipe for a certain period of time, and then the residual oxygen concentration of the gas sampled from the intermediate port 71 was measured. The degree of gas replacement was evaluated by its maximum value. It was evaluated that the smaller this value was, the better the gas replacement inside the cylinder model section 50A was performed by jetting nitrogen gas from the nozzle pipe. The flow rate when blowing out nitrogen gas from the nozzle pipe was all set to 10 L/min. In the continuous ejection, nitrogen gas was continuously ejected at a flow rate of 10 L/min. In the intermittent jetting, the jetting of nitrogen gas was turned ON/OFF so that the average jetting flow rate was 10 L/min. For the same amount of time, the same amount of nitrogen is ejected in both the first and second examples. The results are shown in Table 1 below.

As can be seen from Table 1, the residual oxygen concentration tends to decrease as the ejection time increases. In other words, it can be seen that the longer the ejection time, the more gas replacement inside the cylinder model portion 50A progresses. Furthermore, when comparing continuous ejection and intermittent ejection, it can be seen that the residual oxygen concentration is lower in intermittent ejection, and gas replacement is more advanced. Further, when comparing the ejection directions, the residual oxygen concentration is lower in the first example with the inclined angle than the second example with the downward direction, and gas replacement is more advanced. For example, the result after 120 minutes is that the residual oxygen concentration is 73,000 ppm in the second example of continuous injection and 47,700 ppm in the first example of intermittent injection. Comparing the second example and the first example, the residual oxygen concentration in the first example is about 35% lower.

▽Second Test Next, the purging effect was compared by changing the jetting flow rate when changing the jetting flow rate of nitrogen gas intermittently.

FIG. 5 is a schematic diagram illustrating the change in ejection flow rate in the second test.
FIG. 5(A) is a diagram illustrating the change in ejection flow rate in Experimental Example 1. The intermittent jetting flow rate (area indicated by diagonal lines A in the figure) was 10 L/min, and the continuous jetting flow rate was zero L/min. In other words, it is an intermittent pattern in which the ejection flow rate is temporarily zero.
FIG. 5(B) is a diagram illustrating changes in ejection flow rate in Experimental Examples 2 to 6. The intermittent jetting flow rate (area indicated by diagonal line A in the diagram) was changed to 9 L/min, 8 L/min, 7 L/min, 6 L/min, and 5 L/min, and the continuous jet flow rate (region indicated by diagonal line B in the diagram) was changed to 1 L/min. minutes, 2 L/min, 3 L/min, 4 L/min, and 5 L/min. In other words, this is a pattern in which a constant amount is continuously ejected and then the ejected amount is intermittently increased.
FIG. 5(C) is a diagram illustrating the change in ejection flow rate in Experimental Example 7. The continuous ejection flow rate (the area indicated by the diagonal line B in the figure) was 10 L/min. In other words, it is a pattern in which a fixed amount is continuously ejected.
In either pattern, the average ejection flow rate is 10 L/min, and the same amount of nitrogen gas is ejected for the same amount of time.

Table 2 below shows the measured values of the oxygen concentration in the cylinder model portion 50A after the ejection times were set to 30 minutes, 60 minutes, and 120 minutes in Experimental Examples 1 to 7 above.

As shown in Table 2 above, when the flow rate of nitrogen gas was intermittently switched (Experimental Examples 1 to 6), better results were obtained compared to when nitrogen gas was continuously jetted (Experimental Example 7). ing. The results tend to get worse as the intermittent jetting flow rate decreases. It can be considered that by temporarily and completely stopping the blowout of nitrogen gas, the flow of gas in the cylinder model portion 50A is promoted.

Further, even if the jetting of nitrogen gas is not completely stopped, the results tend to be better by intermittently switching the jetting flow rate. Specifically, if the ratio of the intermittent ejection flow rate is 90% or more (Experimental Example 2), the effect is comparable to that of Experimental Example 1. On the other hand, when the ratio of the intermittent jetting flow rate is 80% or less (Experimental Examples 3 to 6), the effect becomes small.

〔summary〕
By jetting nitrogen gas obliquely upward into the cylinder model part 50A, an action is created to push and move the gas in the cylinder model part 50A in the horizontal direction, and by spouting nitrogen gas intermittently, the gas in the cylinder model part 50A is This is thought to be due to the fact that it was able to flow without being held down.

[Modified example]
Although particularly preferred embodiments of the present invention have been described above, the present invention is not intended to be limited to the illustrated embodiments, but can be modified and implemented in various ways, and the present invention includes various modified examples. The purpose is to

For example, in each of the above experimental examples, when changing the inert gas jet flow rate intermittently, the flow rate when the jet flow rate is small and the flow rate when the jet flow rate is large are fixed respectively, but the flow rate when the jet flow rate is small is fixed. The flow rate when the ejection flow rate is large can also be set in stages.

10: Screw cylinder 10A: Cylinder body 11: Supply means 11A: Hopper section 11B: Chute section 12: Injection hole 13: Lower end opening 14: Supply port 20: Heat melting section 21: Heater 30: Screw 31: Flange 32: Spiral protrusion Article 40: Spray nozzle 41: Nozzle opening 42: Open/close valve 43: Control section 50: Model cylinder 50A: Cylinder model section 50B: Chute model section 51: Tip cap 52: Root cap 53: Plug 54A: First nozzle pipe 54B: Second nozzle pipe 55: Exhaust pipe 61: Nitrogen gas cylinder 62: Inlet pipe 63: Flow rate controller 64: Open/close valve 65: Nitrogen gas production device 71: Intermediate port 72: Tip port 73: Sampling pump 74: Oxygen concentration meter 75: Purge line 76: Air compressor 77: Air purge line

Claims (6)

In an injection molding machine equipped with a heating melting section that heats and melts the injection material supplied from the supply means, and a screw cylinder that has a screw that extrudes the injection material melted in the heating melting section toward an injection hole at the tip. , a method for replacing gas in the screw cylinder, comprising:
It is further equipped with a jet nozzle that jets inert gas,
The jetting nozzle jets out an inert gas at a side closer to the supplying means than the heating and melting part in the screw cylinder,
The ejection nozzle ejects the inert gas so that the nozzle opening faces the injection hole side of the screw cylinder , and intermittently switches the ejection flow rate of the inert gas.
A gas replacement method for an injection molding machine, characterized in that: 2. The gas replacement method for an injection molding machine according to claim 1, wherein the injection nozzle is configured such that the direction of inert gas ejected from the nozzle opening has an inclination angle with respect to the axis of the screw cylinder. When the above-mentioned jet nozzle intermittently switches the jetting flow rate of the inert gas, the time when the jetting flow rate of the inert gas is small is set to be equal to or greater than the time when the jetting flow rate of the inert gas is high. A gas replacement method for an injection molding machine according to claim 1 or 2 . In an injection molding machine equipped with a heating melting section that heats and melts the injection material supplied from the supply means, and a screw cylinder that has a screw that extrudes the injection material melted in the heating melting section toward an injection hole at the tip. , a device for replacing gas in the screw cylinder,
It is further equipped with a jet nozzle that jets inert gas,
The jetting nozzle jets out an inert gas at a side closer to the supplying means than the heating and melting part in the screw cylinder,
The ejection nozzle is configured such that the nozzle opening ejects the inert gas toward the injection hole side of the screw cylinder, and intermittently switches the ejection flow rate of the inert gas .
A gas replacement device for an injection molding machine characterized by the following. 5. The gas replacement device for an injection molding machine according to claim 4 , wherein the injection nozzle has a direction in which the inert gas ejected from the nozzle opening has an inclination angle with respect to the axis of the screw cylinder. When the above-mentioned jet nozzle intermittently switches the jetting flow rate of the inert gas, the time when the jetting flow rate of the inert gas is small is set to be equal to or greater than the time when the jetting flow rate of the inert gas is high. A gas replacement device for an injection molding machine according to claim 4 or 5 .

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