Patent Grant
10967426
This application claims the priority benefit of Japan application serial No. 2018-189978, filed on Oct. 5, 2018. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.
The disclosure relates to an injection device of light metal injection molding machine in which a melt of a light metal material in a supply unit is supplied to an injection unit through a communication passage and then the melt in the injection unit is injected into a mold device through an injection nozzle, and relates to an injection control method thereof.
The injection device of light metal injection molding machine supplies the melt of the light metal material in the supply unit into the injection unit and injects the melt in the injection unit to the mold. The melt is supplied to the supply unit from outside. The supply unit also includes a melting unit which melts an unmelted light metal material supplied from outside into a melt and supplies the melt into the injection unit.
An injection molding machine in patent literature 1 has a melting device equivalent to the above-described melting unit and an injection portion equivalent to the above-described injection unit. The melting device has a melting cylinder and an inert gas supplying device which supplies an inert gas into the melting cylinder. The injection portion has an injection cylinder, a plunger which advances and retracts in the injection cylinder, and an injection nozzle in a front end of the injection cylinder. The melting device and the injection portion are coupled by a coupling member. The interior of the melting cylinder and the interior of the injection cylinder are communicated by a communication passage included in the coupling member. The communication passage is opened and closed by a backflow prevention device. The melting cylinder, the injection cylinder, the coupling member and the injection nozzle are heated by winding a heater around the outer periphery.
The melting cylinder melts a light metal material supplied from outside into a molten material equivalent to the above-described melt and supplies the molten material to the injection cylinder through the communication passage. At this time, the backflow prevention device opens the communication passage. The inert gas supplying device supplies the inert gas above the molten material in the melting cylinder. The molten material in the melting cylinder is covered above a liquid level by the inert gas supplied from the inert gas supplying device.
The injection cylinder makes the plunger retract to measure the molten material supplied from the melting cylinder. The backflow prevention device closes the communication passage when the measurement ends. The injection cylinder makes the plunger advance to inject the molten material to a cavity space inside a mold through the injection nozzle. The molten material is cooled in the mold device and solidifies into desirable molded articles.
The backflow prevention device has a valve rod and a valve rod driving device which drives the valve rod. The valve rod passes through the melting cylinder and is seated on a valve seat inside the melting cylinder. The valve seat is formed around an opening on a melting cylinder side of the communication passage which opens on an inner peripheral surface of a cylinder hole of the melting cylinder.
A backflow prevention device of an injection device of light metal injection molding machine of patent literature 2 has a valve rod, a valve rod driving device which drives the valve rod, and a double pipe for flowing a cooling fluid in the valve rod. A seal seat equivalent to the above-described valve seat is formed around an opening on an injection cylinder side of a communication passage which opens on an inner-hole surface of an injection cylinder. The valve rod passes through the injection cylinder and is seated on the seal seat inside the injection cylinder.
The double pipe inside the valve rod is covered by a heat-insulating material in parts expect a front end of the valve rod in order to cool only the front end of the valve rod. A semisolid resulting from semi-solidification of a molten material is attached to the valve rod around the cooled front end. The semisolid fills a gap following the space between the valve rod and the seal material when the valve rod is seated on the seal seat to more effectively prevent backflow of the molten material. The semisolid is heated and melted by the molten material around if the cooling medium does not flow.
Patent Literature 1: US2018117671
Patent Literature 2: Japanese Laid-Open No. 2005-199335
The gas slightly remained inside the injection cylinder is discharges out of the mold device from an air vent included in the mold device when injected into the mold device together with the melt. However, a small amount of gas which is not discharged causes formation of cavities in the molded articles. Therefore, desirably, the gas remains in the injection cylinder as little as possible.
In a case that the gap between the valve seat and the valve rod seated on the valve seat is filled by the semisolid of the melt when the communication passage is closed, when the communication passage is opened, even if the valve rod is separated from the valve seat, the semisolid is not melted at once and the semisolid blocks the opening of the communication passage for a while, causing the flow of the melt inside the communication passage to be slowed down. Therefore, desirably, the semisolid which is attached to and remains in the valve seat is removed as much as possible immediately after the valve rod is separated from the valve seat.
The disclosure provides an injection device of light metal injection molding machine and an injection control method thereof, the injection device of light metal injection molding machine being capable of discharging the gas slightly remained inside the injection cylinder into the melting cylinder to prevent generation of cavities inside the molded articles and further supplying the melt from the melting cylinder to the injection cylinder quickly with a sufficient flow rate immediately after the communication passage is opened. Additional objects and advantages of the disclosure will be set forth in the description that follows.
The injection control method of the injection device of light metal injection molding machine of the disclosure is an injection control method of an injection device of light metal injection molding machine 1 in which a melt of a light metal material in a supply unit 2 is supplied into an injection unit 3 through a communication passage 40, a plunger 32 included in the injection unit is retracted and the melt of a predetermined volume in the injection unit is measured, the communication passage is closed and the plunger is advanced to inject the melt in the injection unit into a mold device 8 through an injection nozzle 35 included in the injection unit. In the injection control method, after the melt is injected and before the melt is measured, the plunger is advanced at a pressure at which the melt in the injection unit does not come out from the injection nozzle and at least part of the melt in the injection unit is flowed back into the supply unit through the opened communication passage.
The injection device of light metal injection molding machine of the disclosure includes: a supply unit 2 which supplies a melt of a light metal material; an injection unit 3 in which a plunger 32 advancing and retracting is disposed and to which an injection nozzle 35 is connected; a coupling member 4 which couples the supply unit and the injection unit, and in which a communication passage 40 communicating the interior of the supply unit and the interior of the injection unit is formed; a backflow prevention device 5 which opens and closes the communication passage; and an injection control unit 70 which controls the supply unit, the injection unit and the backflow prevention device, carries out a series of control that the melt in the supply unit is supplied into the injection unit through the communication passage, the plunger is retracted to measure the melt of a predetermined volume in the injection unit, the communication passage is closed, and the plunger is advanced to inject the melt in the injection unit into a mold device 8 through the injection nozzle, and carries out a series of control that after the melt is injected and before the melt is measured, the plunger is advanced at a pressure at which the melt in the injection unit does not come out from the injection nozzle, and at least part of the melt in the injection unit is flowed back into the supply unit through the opened communication passage.
The injection device of light metal injection molding machine of the disclosure and the injection control method thereof can prevent the generation of cavities formed in the molded articles, and quickly supply the melt to the injection unit.
A basic configuration of an injection device of light metal injection molding machine 1 of the disclosure is shown in
The light metal injection molding machine has the injection device 1, a mold clamping device, and a control device 7 which controls the injection device 1 and the mold clamping device. The injection device 1 and the control device 7 are shown in
In the light metal injection molding machine, the mold device 8 is closed by the mold clamping device, the mold is further tightened, the melt of a light metal material is injected toward a cavity space inside the mold device 8 by the injection device 1 to fill the cavity space, and after the melt is cooled and solidified in the mold device 8, the mold device 8 is opened by the mold clamping device and the molded article 9 is taken out.
The light metal injection molding machine has a structure suitable for an injection molding machine in which a molding material is a light metal material. The light metal material in the disclosure refers to a metal having a specific gravity of 4 or less. In practical use, aluminum and magnesium are particularly effective as the mold material. When the mold material is aluminum, in order not to be melted away, a site in contact with the molding material is basically coated with a cermet-based material.
The injection device 1 shown in
The melting unit 2 shown in
The cylinder hole of the melting cylinder 20 is formed in a manner that an inner diameter is smaller at a rear end than at other portions and is larger than an outer diameter of the billet 22. The melting cylinder 20 has a reduced-diameter portion 21 in the rear end. An inner diameter of the reduced-diameter portion 21 is formed smaller than the inner diameter of the cylinder hole of the melting cylinder 20 and larger than the outer diameter of the billet 22. The melting cylinder 20 and the reduced-diameter portion 21 may be integrally formed.
In the melting cylinder 20, the temperature of the heater in the rear end is controlled to generate a seal member being a solid which is in a state of being softened to an extent that the melt exists between the reduced-diameter portion 21 and the billet 22 and which is solidified to an extent that backflow of the melt is prevented. The seal member seals the space between the rear end of the melting cylinder 20 and the billet 22 to prevent leakage of the melt. The seal member reduces the friction between the melting cylinder 20 and the billet 22 to allow smooth movement of the billet 22. By being caught in an annular groove formed on an inner peripheral surface of the reduced-diameter portion 21 or a step between the cylinder hole of the melting cylinder 20 and the reduced-diameter portion 21, the seal member does not come off from the rear end of the melting cylinder 20 even under a pressure of the melt.
In addition, the melting cylinder 20 shown in
The inert gas storage portion 60 gathers various gas such as the inert gas or air or the like which intrudes into the melting cylinder 20, the injection cylinder 30, and the communication passage 40. In the inert gas storage portion 60, the atmosphere of the inert gas is maintained at the predetermined pressure, the inert gas is constantly or timely supplied, and the gas such as air or the like is discharged to the outside. The inert gas is, for example, preferably argon gas (Ar). Argon gas has a higher specific gravity than air. Height of a liquid level of the melt inside the inert gas storage portion 60 may be detected by a liquid level sensor 25. The inert gas storage portion 60 is designed to be capable of containing a required volume from a volume less than one shot to a volume for a plurality of shots as long as the excessive melt inside the melting cylinder 20 can be contained.
The injection unit 3 shown in
The cylinder hole of the injection cylinder 30 is formed in a manner that an inner diameter is smaller at a rear end than at other portions and is larger than an outer diameter of the plunger 32. The injection cylinder 30 has a reduced-diameter portion 31 at the rear end. An inner diameter of the reduced-diameter portion 31 is formed smaller than the inner diameter of the cylinder hole of the injection cylinder 30 and larger than the outer diameter of the plunger 32. The injection cylinder 30 and the reduced-diameter portion 31 may be integrally formed.
In the injection cylinder 30, the temperature of the heater in the rear end is controlled to generate a seal member being a solid which is in a state of being softened to an extent that the melt exists between the reduced-diameter portion 31 and the plunger 32 and which is solidified to an extent that backflow of the melt is prevented. The seal member seals the space between the rear end of the injection cylinder 30 and the plunger 32 to prevent the leakage of the melt. The seal member reduces the friction between the injection cylinder 30 and the plunger 32 to allow smooth movement of the plunger 32. By being caught in an annular groove formed on an inner peripheral surface of the reduced-diameter portion 31 or a step between the cylinder hole of the injection cylinder 30 and the reduced-diameter portion 31, the seal member does not come off from the rear end of the injection cylinder 30 even under a pressure of the melt.
The backflow prevention device 5 shown in
The injection device 1 of the embodiment shown in
The injection control unit 70 shown in
Next, the control for the molding cycle is carried out. One molding cycle is as below. As shown in
The cold plug 35a is a solid which is generated in a manner that the melt inside the injection nozzle 35 is cooled and solidifies at the front end of the injection nozzle 35. The injection nozzle 35 is heated by the heater. The temperature of the front end of the injection nozzle 35 can rise and drop at a predetermined timing by temperature control of the heater. In addition, the front end of the injection nozzle 35 is deprived of heat by the mold device 8 when abutting against the mold device 8 and the temperature drops. The cold plug 35a comes off from the injection nozzle 35 under the great injection pressure when the melt is injected to the mold device 8 and the cold plug 35a is injected into the mold device 8 together with the melt. As shown in
Then, the configuration unique to the disclosure is described. The injection control unit 70 shown in
After the melt is injected, a small amount of the melt remains inside the injection cylinder 30, and the plunger 32 stops, for example, in front of the injection cylinder side opening 40b of the communication passage 40 inside the injection cylinder 30. The amount of the melt remaining inside the injection cylinder 30 after the melt is injected is called a cushion amount. The communication passage 40 is opened, the plunger 32 is further advanced for a shorter distance, and the melt inside the injection cylinder 30 flows back into the melting cylinder 20 through the communication passage 40. In the embodiment shown in
The removed semisolid is heated by the flowing-back melt and the melt around the destination to which the semisolid moves and is melted into melt again. The removed semisolid is quickly melted into melt again and does not disturb the movement of the melt which flows to the injection cylinder 30 from the melting cylinder 20 through the communication passage 40. A distance by which the valve rod 50 is separated from the valve seat 41 is set smaller than the distance at the time of the measurement, and thereby the flowing-back melt can spout vigorously between the valve seat 41 and the valve rod 50 to more effectively remove the semisolid of the melt. The distance by which the valve rod 50 is separated from the valve seat 41 may be a distance equal to or less than 20% of an inner diameter of the communication passage 40, preferably a distance equal to or less than 10% of the inner diameter of the communication passage 40. For example, when the inner diameter of the communication passage 40 is 10 mm, the distance by which the valve rod 50 is separated from the valve seat 41 may be equal to or less than 2 mm, preferably equal to or less than 1 mm. The flow of the melt from the melting cylinder 20 into the injection cylinder 30 through the communication passage 40 becomes smooth. Particularly, even if the melt moves through the communication passage 40 into the injection cylinder 30 under its own weight or a low pressure, the melt can also start moving quickly. Moreover, the semisolid is generated anew after the previous semisolid and an oxidized solid are forcibly removed, and thereby the softened state can be kept constant. The situation in which part of the semisolid is solidified and a gap is formed between the valve seat 41 and the valve rod 50 which are in a backflow prevention state can be prevented.
Part of the various gases accumulated in the vicinity of the injection cylinder side opening 40b of the communication passage 40 in the injection cylinder 30 rises through the communication passage 40 being opened and is discharged into the melting cylinder 20. However, a small amount of the various gases remains inside the injection cylinder 30. For example, the various gases which are accumulated when separated from the injection cylinder side opening 40b of the communication passage 40 in the injection cylinder 30 cannot move by opening the communication passage 40 only. In addition, for example, when the measurement starts immediately after the communication passage 40 is opened, due to the melt which flows into the injection cylinder 30, the various gases are moved to a position separated from the communication passage 40 in the injection cylinder 30. The flowing-back melt forcibly moves the various gases existing inside the injection cylinder 30 into the melting cylinder 20. The various gases inside the injection cylinder 30 are removed. The melt is measure inside the injection cylinder 30 after the various gases are removed. The melt injected into the mold device 8 does not include the various gases. Therefore, generation of cavities in the molded article 9 can be prevented. In addition, because there is no gas inside the injection cylinder 30, accuracy of measuring the melt is improved. The melt which is measured has no variation in volume for each measurement.
After the melt is injected and before the melt flows back, as shown in
After the melt is injected, the melt may not be replenished into the injection cylinder 30, and a small amount of melt may be replenished into the injection cylinder 30 after flowing back into the melting cylinder 20, and again the melt flows back into the melting cylinder 20. The backflow of the melt may be carried out repeatedly after the melt is replenished. By repeating the backflow of the melt for a plurality of times, the flow of the melt passing through the communication passage 40 becomes smoother, and the various gases remaining inside the injection cylinder 30 can be reliably removed. The various gases can also rise through the communication passage 40 to move into the melting cylinder 20 by opening the communication passage 40. The various gases are forcibly moved into the melting cylinder 20 by the melt which flows back from the injection cylinder 30 to the melting cylinder 20. The various gases are easily moved into the melting cylinder 20 by replacing the melt inside the communication passage 40 with the melt which flows back from the injection cylinder 30.
The melt which is measured after the melt flows back may be, for example, as shown in
In addition, as shown in
The backflow prevention device 5 shown in
The melting unit 2 is not limited to the embodiment shown in
The injection device 1 is not limited to the above-described embodiment. For example, the control device 7 may detect, using the position detector which is included in the injection unit 3 and detects the position to which the plunger 32 is advanced or retracted, the measurement position of the plunger 32 in a state when the communication passage 40 is closed after the melt is measured after the melt flows back, and the control device 7 may detect an advance position of the plunger 32 in a state when the melt inside the injection cylinder 30 is compressed from the measurement position by the predetermined pressure. The various gases are compressed more easily compared with the melt. The control device 7 may calculate a difference between the measurement position and the advance position, then determine, if the difference is greater than a reference value set in advance, that the various gases are not appropriately discharged from the injection cylinder 30 and the various gases remains inside the injection cylinder 30, and stop the injection device. In addition, the control device 7 may store necessary data among the measurement position, the advance position, or a determination result for each molding cycle, and display on a display device in various formats such as numerical values, graphs or lists. The various gases included in the melt are compressed more easily compared with the melt. The amount of the various gases included in the melt is measured according to the advance position of the plunger which is advanced under the predetermined pressure. The various gases included in the melt cause generation of cavities in the molded articles and result in varied weights of the molded articles. The determination method more easily measures and manages data showing the amount of the various gases included in each molded article than measuring the weight of each molded article.
The disclosure can also be applied to, for example, the mold device 8 in which an air vent is connected in the cavity space, and the mold device 8 in which a vacuuming device is connected in the cavity space. In addition, the disclosure can also be applied to the injection device 1 which has the injection nozzle 35, and the injection device 1 in which a front end of the injection cylinder 30 is directly connected to the mold device 8. Particularly, the disclosure can, by using the mold device 8 to which the vacuuming device is connected and the injection device 1 which injects the melt from the injection nozzle 35, easily discharge the various gases in the cavity space of the mold device 8 using the vacuuming device by closing the injection nozzle 35, and further, an effect of suppressing the generation of the cavities inside the molded article 9 can be improved because the various gases inside the injection unit 3 of the injection device 1 can be easily discharged.
The embodiment was chosen in order to explain the principles of the disclosure and its practical application. Many modifications and variations are possible in light of the above teachings. It is intended that the scope of the disclosure be defined by the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| JP2018-189978 | Oct 2018 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 20160200022 | Takei et al. | Jul 2016 | A1 |
| 20180117671 | Fujikawa | May 2018 | A1 |
| Number | Date | Country |
|---|---|---|
| 2005199335 | Jul 2005 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20200108439 A1 | Apr 2020 | US |
