JP2008290327A - Injection molding machine and injection molding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection molding machine and method that save electric power consumption and attain energy conservation when a resin material is fused in an evacuated heating cylinder and injected into a cavity of a metallic mold. <P>SOLUTION: In an injection method in which a resin material is fused in an evacuated heating cylinder 4 and injected into a cavity of a metallic mold, a plurality of vacuum pumps P1, P2, P3 are arranged as a vacuum unit 19 for sucking air inside the heating cylinder 4. In the injection molding cycle, at least one of the vacuum pumps P1, P2, P3 is stopped or made to have a rated output or less. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to an injection molding apparatus and an injection molding method for injecting a resin material in a molten state into a mold cavity in a vacuum heating cylinder.

As an injection molding apparatus and an injection molding method for injecting a resin material in a molten state into a vacuum in a heating cylinder and injecting it into a mold cavity, those described in Patent Documents 1 to 3 are known. However, all of those described in Patent Document 1 to Patent Document 3 are used to evacuate the heating cylinder with a single vacuum pump. For this reason, the size of the injection molding device may not match the capacity of the vacuum pump. When the capacity of the vacuum pump is larger, power consumption is wasted. In addition, a large vacuum pump has a problem that a large current flows at the start of the motor, which increases the load on the equipment and increases the maintenance cost. Furthermore, when the material storage chamber is evacuated by a single vacuum pump separately from the inside of the heating cylinder, the problem of taking time to evacuate the material storage chamber and the degree of vacuum in the heating cylinder temporarily decrease ( There was a problem that there might be a low vacuum).

JP 2003-236885 A (0034, FIG. 6) Japanese Unexamined Patent Publication No. 3-184822 (page 2, lower right column, FIG. 1) Japanese Patent Laid-Open No. 2003-311801 (0027, FIG. 1)

In the present invention, in view of the above problems, an injection molding apparatus capable of saving power consumption and saving energy when injecting a resin material in a molten state into a mold cavity in a vacuum heating cylinder An object is to provide an injection molding method. It is another object of the present invention to provide an injection molding apparatus and an injection molding method capable of solving various problems caused by using a large vacuum pump. Furthermore, when the material storage chamber or the like is evacuated in addition to the inside of the heating cylinder, there is a problem that it takes a long time to complete the evacuation, and the degree of vacuum in the heating cylinder temporarily decreases (low vacuum). An object of the present invention is to provide an injection molding apparatus and an injection molding method capable of solving the problem.

The injection molding apparatus according to claim 1 of the present invention is a vacuum unit that sucks the gas in the heating cylinder in the injection molding apparatus that injects the resin material into the mold cavity in a molten state in the vacuum heating cylinder. A plurality of vacuum pumps are provided.

The injection molding apparatus according to claim 2 of the present invention is the injection molding apparatus according to claim 1, wherein a partitionable material storage chamber is provided between the heating cylinder and the material supply apparatus, and the heating cylinder and the material storage chamber are provided. It is connected to a plurality of vacuum pumps.

According to a third aspect of the present invention, there is provided an injection molding method as a vacuum unit for sucking a gas in a heating cylinder in an injection method in which a resin material is molten and injected into a mold cavity in a vacuum heating cylinder. A plurality of vacuum pumps are provided, and at least one of the vacuum pumps is stopped or reduced to a rated output or less during an injection molding cycle.

According to a fourth aspect of the present invention, there is provided an injection molding method as a vacuum unit for sucking a gas in a heating cylinder in an injection method in which a resin material is melted and injected into a mold cavity in a vacuum heating cylinder. A plurality of vacuum pumps are provided, and at least one of the vacuum pumps is stopped by an injection molding apparatus to which a vacuum unit is attached or a molded product to be molded.

An injection molding apparatus according to the present invention includes a plurality of vacuum pumps as vacuum units for sucking gas in a heating cylinder in an injection molding apparatus that injects a resin material into a mold cavity in a molten state in a vacuum heating cylinder. Since it is disposed, when the resin material is melted and injected into the mold cavity in the vacuum heating cylinder, power consumption can be saved and energy saving can be achieved.

An injection molding apparatus and an injection molding method provided with a plurality of vacuum pumps according to this embodiment will be described with reference to FIGS. FIG. 1 is a schematic explanatory view of an injection molding apparatus and a vacuum unit of the present embodiment. FIG. 2 is a flowchart showing the control of the vacuum unit until the injection molding cycle starts in the injection molding method of the present embodiment. FIG. 3 is a flowchart showing the control of the vacuum unit during the injection molding cycle in the injection molding method of the present embodiment. FIG. 4 is a graph showing the degree of vacuum during the injection molding cycle and the operating state of the vacuum pump. FIG. 5 is a flowchart showing the control of the vacuum unit when the resin material is supplied to the material storage chamber in the injection molding method of the present embodiment.

The injection molding device 1 includes an injection device 2 and a mold clamping device (not shown), and molds a molded product by injecting molten resin from the injection device 2 into a mold cavity attached to the mold clamping device. The injection device 2 is provided with a screw 5 that is rotationally driven by a metering motor 6 and driven forward and backward by an injection motor (not shown) in a heating cylinder 4 to which a heater 3 is attached. In the present embodiment, a connecting cylinder 7 is attached in the vertical direction from the resin inlet 4a at the rear upper part of the heating cylinder 4, and a feed screw arranging cylinder 8 is attached to the connecting cylinder 7 in a direction parallel to the heating cylinder 4. Yes. A feed screw 10 for controlling the supply amount of the resin material M (resin pellet) and supplying it into the heating cylinder 4 is rotatably arranged by the supply motor 9 in the feed screw arrangement cylinder 8. Has been.

Further, a resin charging port 8a is provided at the upper rear portion of the feed screw arranging cylinder 8, and a supply tube 11 is provided in a vertical direction from the resin charging port 8a. The supply cylinder 11 is a part for temporarily storing a resin material M sent from a material supply apparatus (not shown), and a material storage chamber 12 that can be partitioned between the heating cylinder 4 and the material supply apparatus is provided. It has been. More specifically, the supply cylinder 11 is a glass cylinder, and is arranged in the order of the cylinder portions 11a, 11b, and 11c from the top. An upper shutter 15 that is opened and closed by the air cylinder 13 is disposed between the cylinder part 11a and the cylinder part 11b. A lower shutter 16 that is opened and closed by an air cylinder 14 is disposed between the cylinder part 11b and the cylinder part 11c. Therefore, the material storage chamber 12 is formed in the inside of the cylinder part 11b in the meantime. Reflective photoelectric sensors 17 and 18 for detecting the amount of the resin material M are disposed on the side of the cylinder portion 11a above the upper shutter 15 and on the side of the cylinder portion 11c below the lower shutter 16, respectively. ing. The heating cylinder 4, the connecting cylinder 7, the feed screw arranging cylinder 8, the shutter portions 15 and 16 of the cylinder portions 11a, 11b and 11c of the supply cylinder 11 have a sealing structure so that the internal space is evacuated. ing. Also, the shaft 5 rear portion side of the screw 5 and the feed screw 10 has a seal structure.

The vacuum unit 19 includes three rotary blade type oil rotary pumps (evacuation speed 230 liters (50 Hz) to 280 liters (60 Hz) / min, vacuum pumps P1, P2, and P3 having a motor output of 0.4 kW arranged in parallel. In the present invention, the vacuum pumps P1, P2, and P3 may be other vacuum pumps such as a dry roots pump, and can achieve a desired degree of vacuum in terms of exhaust speed and ultimate degree of vacuum. The main vacuum pump only uses a pump with a high pumping speed, and the others may be a small vacuum pump with a low pumping speed, or a combination of a roughing pump and a high vacuum pump. Also, it is desirable to install the vacuum pumps in parallel, but it does not exclude those that are arranged in series. It may be a vacuum pump.

A check valve 21a for preventing the backflow of gas from the pump side into the heating cylinder 4 when the vacuum pumps P1, P2, P3 are stopped is provided in the pipelines 20a, 20b, 20c from the vacuum pumps P1, P2, P3. , 21b, 21c are arranged. The pipes 20a, 20b, and 20c join the pipe 22 on the heating cylinder 4 side of the check valves 21a, 21b, and 21c. The conduit 22 is provided with an electromagnetic switching valve 24 that doubles as an on-off valve and a leak valve for the conduit 22 and can be switched to a conduit to the filter 23 used when the atmosphere is released. The pipe 22 is branched on the heating cylinder 4 side and communicates with the pipe 25 that communicates with the material storage chamber 12 and the pipe 4 that communicates with the inside of the heating cylinder 4 through the feed screw-arranged cylinder 8 and the connection cylinder 7. Branches to 26. An electromagnetic on-off valve 27 is disposed in the pipe line 25 communicating with the material storage chamber 12, and a vacuum gauge 28 for measuring the degree of vacuum in the heating cylinder 4 is provided in the pipe line 26 communicating with the heating cylinder 4. Is arranged. The control device 29 is a controller that performs various controls of the injection molding device 1, and is also connected to the motors of the vacuum pumps P1, P2, and P3, the vacuum gauge 28, the valves, and the like. Actually, a separate control device is also provided on the vacuum unit 19 side, and a signal is exchanged with the control device of the injection molding device 1.

Next, a control method of the injection molding apparatus 1 provided with the vacuum unit 19 of the present embodiment will be described with reference to FIGS. First, control for determining the number of vacuum pumps P1, P2, P3 used during the injection molding cycle will be described. As shown in FIG. 2, the vacuum pump P1 is turned on and operated by a command signal from the control device 29 (s1), and then the monitoring timer T1 of the control device 29 is started (s2). Until the monitoring timer T1 expires (s4), it is monitored whether the value of the vacuum gauge 28 is equal to or less than a predetermined value and PS-1 is turned on (s3). If the PS-1 is turned on before the monitoring timer T1 expires (s3), the control device 29 uses only the vacuum pump P1, assuming that the required vacuum degree is reached only by the vacuum pump P1. Then, the supply of the resin material M is started (s5) and the process proceeds to the injection molding cycle. In this embodiment, the degree of vacuum at which PS-1 is turned on is -99 kPa in gauge pressure (2.33 kPa in absolute pressure).

If PS-1 is not turned on (s3) and the monitoring timer T1 expires (s4), the control device 29 switches the electromagnetic switching valve 24 to temporarily release the inside of the heating cylinder 4 to the atmosphere (s6). ). Then, the electromagnetic switching valve 24 is switched again, the vacuum pump unit 19 and the inside of the heating cylinder 4 are connected via the conduit 22, the vacuum pump P2 is operated (s7), and the monitoring timer T2 is started (s8). At this time, the vacuum pump P1 continues to operate. Then, until the monitoring timer T2 expires (s10), it is monitored whether the value of the vacuum gauge 28 becomes equal to or less than a predetermined value and PS-1 is turned on (s9). If the PS-1 is turned on before the monitoring timer T2 expires (s9), the controller 29 determines that the required vacuum degree has been reached by the operation of the vacuum pumps P1 and P2, and the vacuum pump P1. , P2 only, and supply of the resin material M is started (s5), and the process proceeds to the injection molding cycle.

If PS-1 is not turned on (s9) and the monitoring timer T2 is up (s10), the electromagnetic switching valve 24 is switched to open the heating cylinder 4 to the atmosphere again (s11). Then, the electromagnetic switching valve 24 is switched again, the vacuum pump unit 19 and the inside of the heating cylinder 4 are connected via the conduit 22, the vacuum pump P3 is operated (s12), and the monitoring timer T3 is started (s13). At this time, the vacuum pumps P1 and P2 continue to operate. Then, until the monitoring timer T3 expires (s15), it is monitored whether the value of the vacuum gauge 28 is equal to or less than a predetermined value and PS-1 is turned on (s14). When the PS-1 is turned on by the time when the monitoring timer T3 expires (s15) (s14), the control device 29 assumes that the required vacuum degree is reached by the vacuum pumps P1, P2, P3. The supply of the resin material M is started using the vacuum pumps P1, P2, P3 (s5), and the process proceeds to the injection molding cycle. Further, when the monitoring timer T3 is timed out before PS-1 is not turned on (s14), the control device 29 indicates that one of the vacuum pumps P1, P2, P3 and the vacuum gauge 28 is malfunctioning, or The vacuum pumps P1, P2, P3 are stopped (s16) because leakage from the seal portion including the heating cylinder 4 is suspected.

Next, the vacuum control in the heating cylinder 4 by the vacuum unit 19 during the injection molding cycle will be described. An example in which two vacuum pumps P1 and P2 are used in the control of the vacuum unit until the start of the injection molding cycle shown in FIG. 2 will be described. As shown in FIGS. 3 and 4, a vacuum gauge 28 that simultaneously operates the vacuum pumps P <b> 1 and P <b> 2 according to a command signal from the control device 29 to increase the degree of vacuum in the heating cylinder 4 and measures the degree of vacuum in the heating cylinder. When the value PS is equal to or higher than SV (-99 kPa (2.33 kPa in absolute pressure)) in this embodiment (s1), the vacuum pump P2 is turned off by a signal from the control device 29. (S2). If the value PS of the vacuum gauge is still smaller than SV, the operation of the vacuum pumps P1 and P2 is continued. Then, after the vacuum pump P2 is turned off, the vacuum gauge 28 has a vacuum lower than SV-α (−97 kPa (4.33 kPa in absolute pressure)) obtained by subtracting a constant hysteresis α (in this embodiment, 2 kPa) to SV. When the time is reached (s3), the vacuum pump P2 is actuated again by a signal from the control device 29 (s4). When the value PS of the vacuum gauge 28 becomes the same as or higher than SV (s1) again, the vacuum pump P2 is turned off (s2) repeatedly. Then, by repeating the control until the injection molding cycle is completed, the vacuum pump P2 can be stopped if the degree of vacuum is a certain level or more, and molding can be performed with minimum power consumption. Note that three or more vacuum pumps may be used in the present invention, and at least one vacuum pump may be stopped. Furthermore, when the degree of vacuum is above a certain level, the voltage value or current value is controlled so that at least one of the vacuum pumps is below the rated output using an inverter, or the idling operation state is set to the rated output below at a predetermined ratio, You may make it reduce power consumption, without stopping a vacuum pump.

Next, vacuum control in the material storage chamber 12 by the vacuum unit 19 will be described. As shown in FIG. 5, when it is detected by the reflective photoelectric sensor 18 that the resin material M sent to the feed screw-arranged cylinder 8 has decreased, the air cylinder 14 is actuated by a signal from the control device 29. The lower shutter 16 is opened, and the resin material M in the material storage chamber 12 is sent into the feed screw supply cylinder 8. The electromagnetic on-off valve 27 is closed (s2) before and after the lower shutter 16 is closed by the air cylinder 14 by the timer (s1). Then, the air cylinder 13 is actuated by a signal from the control device 29, the upper shutter 15 is opened, and a certain amount of resin is stored in the non-vacuum material storage chamber 30 formed in the upper cylindrical portion 11a on the upper shutter 15. The material M is sent into the material storage chamber 12. Actually, before opening the upper shutter 15, the material storage chamber 12 is opened to the atmosphere by opening a leak valve (not shown).

Next, when the upper shutter 15 is closed by the air cylinder 13 by the timer (s3), the electromagnetic on-off valve 27 is opened again (s4), and then the value of the vacuum gauge 28 becomes PS <SV-α. A signal is sent from the control device 29 to activate the vacuum pump P2 (s6). When the degree of vacuum becomes PS ≧ SV (s7), the vacuum pump P2 is turned off (s8), and the material storage chamber 12 is completely evacuated. The above control is repeated during the injection molding cycle. In the case where the volume of the material storage chamber 12 is increased and the resin material M is supplied to the feed screw-arranged cylinder 8 in a fixed amount, an electromagnetic opening / closing valve is also provided in the pipe 26 and the electromagnetic opening / closing valve is closed. The material storage chamber 12 may be evacuated by a plurality of vacuum pumps to prevent the degree of vacuum in the heating cylinder 4 and to speed up the material storage chamber 12 at a high speed.

Then, the resin material M sent to the feed screw-arranged cylinder 8 is controlled by the control device 29 so that the rotation of the motor 9 for supply is controlled. The state of being supplied below a certain level) is supplied. The resin material M sent into the heating cylinder 4 is melted by the heat of the heater 3 and sent forward with the rotational drive and backward movement of the screw 5, but the inside of the heating cylinder 4 is in a vacuum state (in the absolute vacuum as described above, In addition, since the resin material M is in a starved state, the generated gas is well removed. The measured molten resin is injected and filled into the cavity of the mold when the screw 5 is driven forward by an injection motor (not shown), and is cooled and solidified to form a molded product.

The present invention is not enumerated one by one, but is not limited to that of the above-described embodiment, and it goes without saying that those skilled in the art also apply modifications made in accordance with the spirit of the present invention. is there. Since the vacuum unit 19 has a simple structure for removal and installation, it can be used in combination with other injection molding apparatuses. For example, in an injection molding machine with a mold clamping force of 3500KN, three vacuum pumps are operated, and two of them are always operated at the rated output. Can be used in a state where one or two vacuum pumps are completely stopped, leading to power saving. Even with the same injection molding device, the number of vacuum pumps can be changed in the same way as described above, even when the frequency of opening and closing the material storage chamber and the required vacuum level are changed depending on the volume of the molded product and the type of resin. It is also possible to do. Further, even if the same injection molding apparatus is used, even when the degree of vacuum increases due to deterioration of the seal member or the like, it is possible to cope with the problem by increasing the number of operating vacuum pumps. Furthermore, one vacuum unit 19 is attached to two or more injection molding machines, when one of the two injection molding machines starts operation, when a resin material is supplied to the material storage chamber, and a heating cylinder In at least one of the cases where the degree of vacuum has decreased, a vacuum pump that has been operated or stopped at or below the rated output may be operated at the rated output. Since a small or relatively small vacuum pump is used in the present invention, it is possible to solve the problem that a large current flows when the motor is started and the load on the equipment increases and the maintenance cost increases. Furthermore, the present invention is also applied to an injection molding apparatus provided with a pre-plastic injection device that melts a resin material in a plasticizing device having a rotating screw and injects the molten resin into a mold cavity using a plunger. be able to.

It is a schematic explanatory drawing of the injection molding apparatus and vacuum unit of this embodiment. It is a flowchart which shows control of the vacuum unit until the injection molding cycle start in the injection molding method of this embodiment. It is a flowchart which shows control of the vacuum unit in an injection molding cycle in the injection molding method of this embodiment. It is a graph which shows the operating condition of the vacuum degree in an injection molding cycle, and a vacuum pump. It is a flowchart which shows control of the vacuum unit at the time of supplying the resin material to a material storage chamber in the injection molding method of this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Injection molding apparatus 2 Injection apparatus 4 Heating cylinder 5 Screw 11 Supply cylinder 12 Material storage chamber 19 Vacuum unit 28 Vacuum gauge 29 Controller P1, P2, P3 Vacuum pump

Claims (4)

In an injection molding apparatus for injecting a resin material into a mold cavity in a molten state in a vacuum heating cylinder,
An injection molding apparatus comprising a plurality of vacuum pumps as a vacuum unit for sucking the gas in the heating cylinder. 2. A partitionable material storage chamber is provided between the heating cylinder and the material supply device, and the heating cylinder and the material storage chamber are connected to the plurality of vacuum pumps. The injection molding apparatus described in 1. In the injection method of injecting the resin material into the mold cavity in a molten state in a vacuum heating cylinder,
A plurality of vacuum pumps are arranged as a vacuum unit for sucking the gas in the heating cylinder, and at least one of the vacuum pumps is stopped or set to a rated output or less during an injection molding cycle. . In the injection method of injecting the resin material into the mold cavity in a molten state in a vacuum heating cylinder,
A plurality of vacuum pumps are arranged as vacuum units for sucking the gas in the heating cylinder, and at least one of the vacuum pumps is stopped by an injection molding apparatus to which the vacuum unit is attached or a molded product to be molded. An injection molding method.

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