JP2004025291A - Injection molding method and injection molding apparatus for light alloy - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection molding method and an injection molding apparatus for a light alloy in which accurate metering is possible. <P>SOLUTION: The method consists of (a) a feed stage where the molten metal 3 of a light alloy material is fed; (b) a transition stage where the molten metal 3 is cooled while stirring it with an extrusion screw 5, and is transited to half-solidified slurry 8; (c) the primary metering stage where a communication passage 10 is closed, and the half-solidified slurry 8 is stored in a storage part 6 formed by retreating the extrusion screw 5 to the upper side in a prescribed amount; (d) the secondary metering stage where the communication passage 10 is opened, and the half-solidified slurry 8 is extruded inside the cylinder 11 via the communication passage 10 in such a manner that a plunger 12 is retreated while the extrusion screw 5 is advanced so as to apply positive pressure to the half-solidified slurry 8 extruded inside the cylinder 11; and (e) an injection stage where the communication passage 10 is closed, and thereafter, the plunger 12 is advanced to inject the half-solidified slurry 8. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an injection molding method and an injection molding apparatus for molding a light alloy such as magnesium and aluminum.
[0002]
[Prior art]
Recently, a molding method called a thixomold method utilizing a semi-solid state of a metal in combination with an injection molding technique has been put to practical use. As the thixomold method, M.I. C. US Patent No. 3,902,544 to Flemings et al. In addition, a method of using a screw to create a semi-solid state in which a solid phase and a liquid phase are mixed is described in Japanese Patent Publication Nos. 1-354341 and 2-15620. Further, an injection molding method using these methods is described in JP-A-3-504830.
[0003]
An injection molding method of this kind of light alloy is disclosed in Japanese Patent No. 2832625. In this method, unlike the thixomolding method, an ingot raw material is heated to a semi-molten state without using a pellet (chip or granule) material, and then is granulated by a pulverizer and supplied to a cylinder.
[0004]
As another method of injecting in a semi-solid state, there is one described in Japanese Patent No. 2974416. In this type, light alloy material melted in a melting furnace is supplied from a hopper arranged at the top of a vertical cylinder, and the molten metal is cooled by temperature control by a cooling device arranged outside the cylinder, and vertically arranged In this method, the dendrites are brought into a semi-solid state by stirring and crushing by rotating the screw, and the slurry is measured at the tip of the screw and then injected into a mold located below the screw.
[0005]
As described in Japanese Patent Application Laid-Open No. 3-504830, a light alloy injection molding method using a thixomolding method supplies solid pellets (chips) from a hopper to an in-line type injection molding machine. To produce a semi-molten slurry, send it to the barrel tip with a screw, temporarily store it, and then perform injection molding in the same manner as resin injection molding. In this method, solid pellets are converted into semi-molten slurry by the heating action of the heater inside the barrel and the shearing action of the screw rotation without directly treating the molten metal. Both heating by heating works. As for the heat generated by shearing, the change in the state introduced into the screw, that is, the amount introduced into the screw varies due to the variation in the shape of the metal tip, the shear history is sometimes not constant, and the melting state differs for each injection. coming out. On the other hand, in heater heating, the accuracy of temperature control has a great effect. Usually, the barrel is heated by heater heating, and the metal tip is heated by the conduction heat. Differences occur in the contact surfaces that receive the heat of conduction due to variations in the chip shape. In this case, the distribution in the axial direction of the screw naturally varies, and as a result, the control range varies, and the melting state of the metal tip varies from time to time and is not constant. Further, controlling the screw rotation speed affects the heat history due to heater heating. Therefore, in the thixomolding method, it is difficult to control these parameters to create a slurry state having a stable temperature within a limited screw length and residence time, and the melting start point is not stable and the unmelted state is not obtained. In this case, the ratio of (semi-solid solid particles) changes for each shot. Then, as the temperature distribution in the screw axis direction changes for each shot and the slurry state changes, the viscosity changes, so that stable measurement cannot be performed.
[0006]
In addition, in Japanese Patent Application Laid-Open No. 3-504830, when supplying metal pellets (chips) into the barrel of an in-line injection molding machine, a large amount of gas enters the barrel together with the metal pellets. The viscosity of the slurry in the semi-molten state differs depending on the alloy metal, but is lower than the viscosity of the resin, which is about 100 poise or less, and the extrusion pressure to the slurry caused by screw rotation is lower than that of the resin. Since the feeding ability to feed to the material storage section at the tip of the screw is small, it is not possible to expect a generated pressure enough to overcome the back pressure and retreat the screw as in resin molding. For this reason, in the in-line type, the screw is retracted simultaneously with the rotation of the screw at the time of measurement, but in such a measurement method, only the head pressure on the slurry in addition to the self-weight of the semi-solidified slurry is applied, and the mixed gas flows upstream of the barrel. Without discharging to the hopper side (low-pressure hopper side), most of them remain in the molten slurry, the measurement accuracy becomes unstable, and the quality of the molded product after injection increases, and the quality varies. .
[0007]
Also, Japanese Patent No. 2974416 discloses that the state of the solid phase, that is, the stability of the solid phase ratio and the solid phase particle size are determined by cooling the molten metal to produce a semi-solid slurry, as described in JP-A-3-504830. Is supplied in a better condition than the semi-solid slurry. Further, since the molten metal is supplied into the barrel, the mixing of gas is somewhat improved as compared with Japanese Patent Publication No. Hei 3-504830. However, the low viscosity is essentially the same for the semi-solidified slurry. At the time of measurement, only the head pressure of the slurry from the material introduction portion acts on the weight of the material, and as in Japanese Patent Application Laid-Open No. 3-504830. The mixed gas cannot be discharged to the upstream side of the barrel (lower pressure hopper side) using the pressure generated in the barrel due to the rotation of the screw as in resin molding, so that much mixed gas remains. . Further, since the amount of melting in the molten metal introduction section (hopper) acts as a head pressure, a change in the liquid level at the molten metal introduction section affects measurement accuracy. In addition, as the solid fraction increases, the pressure loss increases and the state at the time of measurement differs. If the screw is retracted in a state where the pressure loss is large and the metering is forcibly performed, gas entrainment from behind the screw may occur.
[0008]
Japanese Patent No. 3237017 discloses a technique for improving the injection molding method of these light alloys. This method describes that the method has a first chamber and a second chamber, and is attracted to the second chamber by a suction force when moving from the first chamber to the second chamber. According to this method, a suction force is generated in the second chamber, and the molten metal is moved to the second chamber by the negative pressure, so that the gas from the gap of the ram (plunger) in the second chamber and the tip of the nozzle is generated. Inevitably occurs. Therefore, a method has been proposed in which the ram in the first chamber pushes the remaining material into the second chamber, thereby pushing out the entrapped gas (air) from the second chamber. It is difficult to sufficiently remove the gas mixed with the molten metal from the second chamber. In addition, the measurement accuracy becomes unstable due to the remaining gas. Further, there is no detailed description of the state of the molten metal, and the molten metal exceeding the liquidus line is introduced into the first chamber, but it is not clear whether the semi-solid slurry is actively generated here. is there. Even if the semi-solidified slurry is produced by cooling in the first chamber, if the solid phase ratio of the semi-solidified slurry increases, it is difficult to attract the semi-solidified slurry to the second chamber by the suction force, and the pressure loss (resistance) increases. The measurement accuracy in the semi-solidified slurry state is deteriorated.
[0009]
Japanese Patent No. 3258617 discloses a similar technique for dividing an extrusion section and an injection section. The solid metal is melted in an extrusion cylinder device, supplied to a pouring cylinder device, and injected into a mold. At this time, a closure provided between the extrusion cylinder and the cylinder gap serves to prevent backflow from the pouring cylinder device to the extrusion cylinder device by moving the screw from the first position to the second position. It is. In this case, since the backflow is not prevented by the pressure generated in the screw by the hydraulic cylinder, there is an advantage that the backflow can be prevented by sealing by the pressure generated in the injection section, and a large hydraulic cylinder is not required. However, since a large amount of gas is mixed into the extrusion cylinder device together with the supply of the solid metal, and since the metering is determined by the extrusion amount and the extrusion force by the screw rotation, in the case of a light alloy having a low viscosity when molten, It is difficult to achieve high weighing accuracy.
[0010]
Therefore, there is a light alloy injection molding apparatus described in Japanese Patent Application Laid-Open No. 2001-1122, in which gas is hardly mixed into an extrusion cylinder and measurement can be performed with high accuracy. In this method, a molten metal is cooled in a substantially vertically oriented chamber while being sheared by an extrusion screw to be transformed into a semi-solidified slurry, and then the semi-solidified slurry discharged from a lower outlet of the chamber is formed into a molding metal. The mold clamping device is configured to open and close the movable mold in the horizontal direction with respect to the fixed mold, and at the lower end discharge port of the chamber, a first vertical flow path, A connecting member extending in the horizontal direction from the lower end of the flow path and having a second flow path therein communicating with the fixed mold is connected. In this case, the semi-solidified slurry discharged from the lower end discharge port of the chamber changes its direction once in the horizontal direction, and is injected into the molding die that opens and closes in the same horizontal direction as the injection direction. Even if the stroke amount is increased, it is not necessary to arrange the screw extruder higher than necessary. In addition, in the apparatus of the present invention, the molten metal is cooled while being sheared by an extrusion screw in a vertical chamber and transitioned to a semi-solidified slurry, so that the solid raw material is heated and semi-solidified similarly to the conventional rheomolding method. Various inconveniences caused by the slurry can be solved, and a high-quality light metal molded product with less bubbles and shrinkage can be injection-molded. On the other hand, as shown in FIG. 3 of the publication, the screw extruder may be provided with an extrusion screw that does not move in the axial direction, and an injection plunger that moves in the horizontal direction may be provided in the second flow path of the injection flow path. In this case, if a check valve for preventing the semi-solidified slurry in the second flow path from flowing back to the screw extruder is provided in the first flow path, measurement of one shot during injection molding can be performed extremely accurately. It becomes something. However, although the measurement accuracy is very high as compared with the above-mentioned conventional one, compared to the general resin injection molding, the measurement is performed by the extrusion force of the extrusion screw. It has instability and requires further improvement to improve the weighing accuracy.
[0011]
[Problems to be solved by the invention]
The present invention is capable of producing a high-quality semi-solid slurry having a uniform solid-phase particle size and accurate measurement thereof, and is capable of obtaining a high-precision light-alloy injection-molded product with less burrs and shrinkage cavities. An object of the present invention is to provide an injection molding method and an injection molding apparatus for an alloy.
[0012]
[Means for Solving the Problems]
The light alloy injection molding method of the present invention for solving the above-mentioned problem is characterized in that the barrel is provided with an extrusion screw therein and is installed in a substantially vertical orientation, and the inside communicates with the barrel via a communication channel. A method for injection molding a light alloy having a cylinder with a plunger, comprising: (a) a supply step of supplying a molten metal of a light alloy material into a barrel from a supply port; and (b) the metal in the barrel. (C) a transition step in which the molten metal is cooled while being stirred by the extrusion screw to transition to a semi-solidified slurry, and (c) the communication channel is closed, and the extrusion screw is retracted upward by a predetermined amount. A primary measuring step of storing the semi-solidified slurry, and (d) opening the communication flow path and forming a measuring section inside the cylinder by retreating at least the plunger to a predetermined position. During extruding the semi-solidified slurry into the cylinder through the communication flow path, the extrusion screw is advanced while applying a positive pressure to the semi-solidified slurry extruded into the cylinder. A secondary measuring step of retracting the plunger; and (e) an injection step of injecting the semi-solidified slurry by moving the plunger forward after closing the communication channel.
[0013]
According to this configuration, since the molten metal of the light alloy is supplied to the barrel, the mixing of gas in the initial stage is small. Further, since the supplied molten metal is cooled while stirring inside the barrel to produce a semi-solidified slurry, there is no variation in heat history such as shearing history as in the thixomolding method, and the molten state (semi-solidified state). The state of the slurry) becomes stable. In addition, a reservoir is formed at the lower part of the screw extruder arranged substantially vertically, and the semi-solidified slurry is moved there by utilizing the head pressure from the supply port and its own weight. The semi-solidified slurry can be temporarily stored without being involved. When pressurizing the stored semi-solidified slurry from the storage section into a measuring section having a predetermined volume, the semi-solidified slurry is measured while applying a positive pressure. As a result of the above pressure, the fluctuation of the head pressure on the supply port side does not affect the measurement, and the residual gas can be discharged to the low pressure supply port side, so that stable and highly accurate measurement can be performed.
[0014]
Further, the injection molding method for a light alloy according to the present invention is characterized in that, in the above invention, the communication channel is opened and closed by a valve means provided in the channel.
According to this configuration, since the communication flow path can be intentionally opened and closed, the primary measurement in the storage unit can be performed with high accuracy and reliability, and the communication flow path is opened after the measurement and the secondary measurement is performed. Move to process. For this reason, variation in measurement for each injection is reduced.
[0015]
Further, in the injection molding method for a light alloy according to the present invention, in the above-described invention, the closing of the communication flow path in the first measuring step is performed by moving the plunger to a position where the communication flow path is closed. The step of closing the communication channel in the step is performed by moving the extrusion screw to a position that closes the communication channel.
According to this configuration, the communication channel can be closed using the respective components of the plunger and the extrusion screw included in the injection molding device, so that the number of components of the injection molding device can be reduced. In addition, the opening and closing control of the communication flow path is performed in series with the control of the plunger and the extrusion screw, thereby simplifying the operation.
[0016]
Further, in the injection molding method of a light alloy according to the present invention, in the above-mentioned invention, in the secondary weighing step, a hydraulic pressure when applying a forward force to a screw hydraulic cylinder for moving the extrusion screw forward and backward, and the plunger moves forward and backward. It is characterized in that at least one of the pressures of the respective hydraulic lines is controlled so that the differential pressure from the hydraulic pressure when the retraction force is applied to the plunger hydraulic cylinder to be made is substantially constant.
According to this configuration, since the extrusion screw and the plunger are advanced and retracted by the hydraulic pressure of each hydraulic cylinder, it is possible to accurately control the storage unit and the measuring unit formed by the advance and retreat of the extrusion screw and the plunger so that the volumes are constant. Weighing with high accuracy. Further, the sizes of the storage section and the measuring section can be controlled in accordance with the size of the molded article. Further, since the pressure acting on the semi-solid slurry extruded into the cylinder can be made substantially constant, the secondary measurement for each injection is further stabilized.
[0017]
Further, in the injection molding method of a light alloy according to the present invention, the molten metal of the light alloy is supplied from the outside to a hopper provided in the supply port, and the temperature of the molten metal is made uniform. It is characterized in that it is supplied inside the barrel.
According to this configuration, since the temperature of the molten metal is made uniform and then supplied to the inside of the barrel, the molten metal having a constant temperature can be cooled in the barrel using the molten metal as a starting material, and the solid phase particle size can be uniform. And a high quality semi-solid slurry can be produced.
[0018]
Further, in the injection molding method of a light alloy according to the present invention, in the transition step, the molten metal is cooled in the barrel such that a solid fraction of the semi-solidified slurry is 5 to 40%. Things.
By cooling the semi-solidified slurry in the barrel so that the solid phase ratio of the semi-solidified slurry is 5 to 40%, it is possible to obtain an appropriate viscosity for introducing the semi-solidified slurry in the barrel into a cylinder equipped with a plunger by an extrusion screw. . Here, when the solid phase ratio is less than 5%, there is almost no change from the liquid phase state. On the other hand, if the solid phase ratio exceeds 40%, the fluidity becomes poor, and the yield of the molded product becomes poor.
[0019]
Further, in the injection molding method for a light alloy according to the present invention, in the above-mentioned invention, the cooling of the molten metal is performed by cooling means provided on the barrel and the extrusion screw.
According to this configuration, the molten metal can be cooled from the inner surface of the barrel and the surface of the extrusion screw, and dendrites can be generated throughout the groove formed by the barrel and the screw. Can be generated.
[0020]
Further, the light alloy injection molding apparatus of the present invention has a supply port at the top of the barrel through which the molten metal is supplied, and has an extrusion screw rotatable inside the barrel and movable back and forth in the barrel axis direction, A substantially vertically arranged screw extruder in which a reservoir is formed in the lower part of the barrel by the retreat of the extrusion screw, and the molten metal supplied into the barrel from the supply port is a semi-solidified slurry. Cooling means for cooling so as to have a plunger movable in the axial direction of the cylinder inside a cylinder connected through a communication flow path provided at a lower end of the barrel, and the plunger is retracted. A plunger injection machine for injecting the semi-solidified slurry when the plunger is advanced by forming a measuring portion in front of the cylinder. A light alloy injection molding apparatus, wherein the extrusion screw has a backflow preventing means at a tip end thereof, and temporarily stores the semi-solidified slurry, and then pressurizes the semi-solidified slurry while applying a positive pressure to the measuring section. It is configured to move forward and backward.
[0021]
According to this configuration, since the molten metal of the light alloy is supplied to the barrel, the mixing of gas in the initial stage is small. Further, since the supplied molten metal is cooled while stirring inside the barrel to produce a semi-solidified slurry, there is no variation in heat history such as shearing history as in the thixomolding method, and the molten state (semi-solidified state). The state of the slurry) becomes stable. In addition, a reservoir is formed at the lower part of the screw extruder arranged substantially vertically, and the semi-solidified slurry is moved there by utilizing the head pressure from the supply port and its own weight. The semi-solidified slurry can be temporarily stored without being involved. When pressurizing the stored semi-solidified slurry from the storage section into the measuring section having a predetermined volume, the semi-solidified slurry is measured while applying a positive pressure to the semi-solidified slurry. Pressure, the fluctuation of the head pressure on the supply port side does not affect the measurement, and the residual gas can be discharged to the low pressure supply port side, so that stable and highly accurate measurement can be performed. In addition, since the backflow prevention means is provided at the tip of the extrusion screw, the communication flow path can be reliably closed, and the backflow to the semi-solidified slurry screw extruder side during the injection process is reliably prevented. Thus, the entire semi-solidified slurry measured by the measuring section can be reliably injected.
[0022]
Further, in the light alloy injection molding apparatus according to the present invention, in the above-mentioned invention, a valve means for opening and closing the communication flow path is provided in the communication flow path.
According to this configuration, since the communication flow path can be intentionally opened and closed, the primary measurement in the storage unit can be performed with high accuracy and reliability, and the communication flow path is opened after the measurement and the secondary measurement is performed. Move to process. For this reason, variation in measurement for each injection is reduced.
[0023]
Further, in the light alloy injection molding apparatus according to the present invention, in the above-described invention, the extrusion screw has a stroke sufficient to move from a position where the storage section is formed to a position where the communication flow path can be closed. A hydraulic cylinder is provided.
According to this configuration, it is possible to form a storage section having an appropriate capacity in the screw extruder according to the molded product. Further, since the communication flow path can be reliably closed, backflow from the plunger injection machine into the screw extruder can be prevented, and measurement can be performed with high accuracy in the secondary measurement process.
[0024]
In the injection molding apparatus for a light alloy according to the present invention, in the above-described invention, the plunger has a hydraulic pressure having a stroke sufficient to move from a position forming the measuring section to a position at which the communication flow path can be closed. It is characterized by having a cylinder.
According to this configuration, it is possible to form a measuring section having an appropriate capacity in the plunger injection machine in accordance with the molded product. In addition, since the communication flow path can be reliably closed, the measurement can be performed with high accuracy in the primary measurement step in the screw extruder.
[0025]
Further, in the light alloy injection molding apparatus according to the present invention, in the above-mentioned invention, the plunger is advanced from a position where the measuring section is formed, and closes the communication channel when injection is completed. It is characterized by the following.
According to this configuration, the communication channel can be closed immediately after the end of the injection step, and the new semi-solidified slurry can be continuously measured in the storage section in the screw extruder.
[0026]
In the injection molding apparatus for a light alloy according to the present invention, in the above-mentioned invention, the cooling means is provided in the barrel and the extrusion screw.
According to this configuration, the molten metal can be cooled from the inner surface of the barrel and the surface of the extrusion screw, and the resinous crystals can be purified over the entire groove formed by the barrel and the screw. Can be generated.
[0027]
Further, the light alloy injection molding apparatus of the present invention, in the above invention, the screw hydraulic cylinder for moving the extrusion screw forward and backward, the plunger hydraulic cylinder for moving the plunger forward and backward, and the semi-solidified slurry from the storage unit. When extruding to the measuring section, hydraulic pressure when the screw hydraulic cylinder is advanced so that a substantially constant positive pressure can act on the semi-solid slurry extruded to the measuring section, and when the plunger is retracted. It is characterized by comprising a hydraulic control means for controlling at least one of the hydraulic pressures of the plunger hydraulic cylinder.
According to this configuration, since the extrusion screw and the plunger are advanced and retracted by the hydraulic pressure of each hydraulic cylinder, it is possible to accurately control the storage unit and the measuring unit formed by the advance and retreat of the extrusion screw and the plunger so that the volumes are constant. Weighing with high accuracy. Further, the sizes of the storage section and the measuring section can be controlled in accordance with the size of the molded article. Further, since the pressure acting on the semi-solidified slurry extruded to the measuring section can be made substantially constant, the measuring for each injection in the measuring section is further stabilized.
[0028]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an example of an embodiment of the present invention. The light alloy injection molding apparatus 1 according to this embodiment has a supply port 4 at the upper part of a barrel 2 through which a molten metal 3 is supplied, and is rotatable inside the barrel 2 and movable forward and backward in the axial direction of the barrel 2. A screw extruder 7 which has a screw 5, and which is formed in the barrel 2 at a lower portion inside the barrel 2 by retreating the extrusion screw 5; A cooling means 9 for cooling the supplied molten metal 3 into a semi-solidified slurry 8, and a cylinder 11 connected to a shaft of the cylinder 11 connected through a communication flow path 10 provided at a lower end of the barrel 2. The plunger 12 is movable forward and backward. The plunger 12 retreats to form a weighing portion 13 inside the cylinder 11 forward. And a plunger injection machine 14 which emits over 7. Further, a hydraulic control device U for controlling the advance and retreat of the extrusion screw 5 and the plunger 12 is provided.
[0029]
Further, the injection molding apparatus 1 includes a hopper 15 for storing the molten metal 3, and a mold clamping device 17 through a nozzle portion 16 provided at the tip of a plunger injection machine 14 to which a semi-solid slurry 8 is injected. , And is in contact with a mold 24 that opens and closes sideways. Among the components of the injection molding apparatus 1, a hopper 15 receives the molten metal 3 melted in a melting furnace (not shown) and stores it in a molten state. It is connected to the upper end. The hopper 15 is provided with a temperature control means such as a heater.
[0030]
The hopper 15 is filled with an inert gas such as argon so that the surface of the molten metal 3 is sealed with the inert gas. A drive motor 18 is directly connected to an upper end of the barrel 2, and a drive shaft of the drive motor 18 is connected to an upper end of an extrusion screw 5 rotatably inserted into the inside of the barrel 2. , Are arranged in a cantilever manner such that their lower ends are free ends in the barrel 2.
[0031]
A screw hydraulic cylinder 19 having a cylinder rod that moves up and down is connected to the upper part of the drive motor 18, and the drive motor 18 is directly connected to a cylinder rod 20 of the screw hydraulic cylinder 19. For this reason, in the screw extruder 7 of the present embodiment, the extrusion screw 5 is moved downward in the axial direction via the drive motor 18 by projecting the cylinder rod 20 of the hydraulic cylinder 19 for screw downward, whereby the barrel The semi-solidified slurry 8 stored at the lower end of the inside 2 can be pushed out. The screw hydraulic cylinder 19 is configured such that when it moves upward in the axial direction, the storage portion 6 having a volume at least larger than the volume of the molded product can be formed in the lower portion of the inside of the barrel 2. Further, it has a stroke sufficient to move from the position where the storage section 6 is formed to a position where the communication flow path 10 can be closed.
[0032]
The outer peripheral surface of the barrel 2 is covered with cooling means 9. The cooling means 9 is composed of a plurality of temperature control jackets 21 vertically separated. By flowing a heat medium such as oil lower than the temperature of the molten metal 3 through the jacket 21, the temperature of the molten metal 3 in the barrel 2 is lower than the liquidus temperature and higher than the solidus temperature. It can be cooled down. In order to control the temperature of the molten metal 3 in the barrel 2 with high accuracy, each temperature control jacket 21 of the cooling means 9 also has a heating function.
[0033]
A plunger injection machine 14 is connected via a communication channel 10 formed at the lower end of the barrel 2. The plunger injector 14 includes a cylinder 11 having a nozzle portion 16 provided with a valve means 22 in the front, and a plunger 12 which can move forward and backward within the cylinder 11. The plunger 12 is driven by the hydraulic pressure of the plunger hydraulic cylinder 23. A measuring portion 13 is formed at the front of the cylinder 11 when the plunger 12 is retracted. The volume of the measuring section 13 can be appropriately set by the retreat amount of the plunger 12 so as to be a volume necessary for obtaining a molded product. Further, the plunger hydraulic cylinder 23 is sufficient to move to a position where the communication flow path 10 connected near the distal end of the cylinder 11 can be closed by the plunger 12 moving forward from the position where the measuring section 13 is formed. It has a great stroke. The plunger 12 is provided so as to close the communication channel 10 when the injection is completed. As a result, the metal melt 3 for the next injection molding can be supplied into the screw extruder 7 immediately after the injection. Further, the valve means 22 of the nozzle section 16 is in a closed state except during injection. The valve means 22 is a means for closing a nozzle by forming a metal solid plug at the tip of the nozzle by a temperature control means such as a temperature control jacket 21 provided on the outer peripheral portion of the cylinder 11, or a mechanical or A nozzle that is closed by a spring-type shut-off valve can be used. However, the latter type of nozzle using a shut-off valve in that a portion having a high solid phase ratio does not occur near the nozzle tip when forming a metal solid plug and there is no possibility that the solid plug is mixed into the product. Is preferred.
[0034]
The mold clamping device 17 includes a link housing 26 erected on a base 25, a fixed plate 28 fixed to the housing 26 via a horizontal tie bar 27, and a fixed metal fixed to the fixed plate 28. A mold 24b, a movable plate 29 slidably supported by the tie bar 27, and a movable mold 24a fixed to the movable plate 29 so as to be freely opened and closed in a horizontal direction with respect to the fixed mold 24b. It has. A mold clamping cylinder 30 is fixed to the center of the outer surface of the link housing 26, and the tip of a cylinder rod 31 of the mold clamping cylinder 30 is connected to the center of the movable platen 29. The link housing 26 and the movable board 29 are connected by a plurality of links 32 which are folded when they approach and separated from each other and are substantially aligned in a horizontal direction when they are separated.
[0035]
An extruding cylinder 33 is provided on a side surface of the movable platen 29 on the side of the link housing 26, and an extruding rod 34 of the extruding cylinder 33 penetrates the movable platen 29 and is connected to a product projecting mechanism of the movable mold 24a. Therefore, in the mold clamping device 17, the cylinder rod 31 of the mold clamping cylinder 30 is protruded to make the link 32 extend in a straight line, and the link 32 is put in a stretched state, so that the movable mold 24a is fixed to the fixed mold. It can be strongly pressed against the mold 24b. The release of the product is performed by operating the product projection mechanism by projecting the pushing rod 34 of the pushing cylinder 33.
[0036]
Next, an operation of the injection molding apparatus 1 and a method of injection molding a light alloy by the operation will be described.
[0037]
First, the molten metal 3 put into the hopper 15 is sent from a melting furnace (not shown) by a mechanical or electromagnetic pump or the like. The melting furnace is not particularly limited, and may be a high-frequency induction furnace or an electromagnetic induction heating furnace. The molten metal 3 in the hopper 15 is maintained at a uniform temperature by temperature control means such as a heater provided in the hopper 15. If necessary, a stirring means for stirring the molten metal in the hopper may be provided to provide a stirring action. The molten metal 3 is supplied to the upper part of the barrel 2 of the screw extruder 7 in a gas-sealed state, and cooled to a temperature below the liquidus temperature and above the solidus temperature by each temperature control jacket 21 to grow into dendrites. . The dendrites are agitated and crushed by the shearing action of the rotating extrusion screw 5 to produce uniform, fine crystal grains, and transition to the semi-solidified slurry 8.
[0038]
At this time, the plunger 12 of the plunger injection machine 14 has advanced to the position where the communication flow path 10 is closed as shown in FIG. Then, when the extrusion screw 5 of the screw extruder 7 retreats, a storage section 6 is formed between the extrusion screw 5 and the communication flow path 10, and the semi-solidified slurry 8 is stored in the storage section 6. The extrusion screw 5 may be one that stops rotating and retreats, or one that retreats while rotating. At this time, it is preferable to provide a backflow prevention means such as a check ring at the tip of the extrusion screw 5, and by providing the backflow prevention means, when the retreating is performed, the semi-solidified slurry 8 is formed while smoothly flowing downward. The primary weighing is performed in the storage section 6 having a larger volume than the product volume.
[0039]
Next, the communication passage 10 is opened to retreat the plunger 12 of the plunger injection machine 14 as shown in FIG. 3, and at the same time, the extrusion screw 5 is advanced. Then, while the plunger 12 retreats to a predetermined position set in accordance with the volume of the molded product, the semi-solidified slurry 8 is applied to the measuring unit 13 formed in front of the cylinder 11 while applying the pressing force of the extrusion screw 5. The secondary weighing is performed by press-fitting while applying a positive pressure to
[0040]
When the weighing by press-fitting is completed, as shown in FIG. 4, the communication flow path 10 is closed by the extrusion screw 5, and the backflow of the semi-solidified slurry 8 from the weighing unit 13 is prevented. At the time of measurement, the nozzle portion 16 at the tip of the cylinder 11 of the plunger injection machine 14 is closed by the valve means 22.
[0041]
After the secondary weighing is completed, the semi-solid slurry 8 is injected into the mold 24 (see FIG. 1) by opening the valve means 22 of the nozzle portion 16 and advancing the plunger 12, thereby forming a molded article having a predetermined shape. Is performed.
[0042]
As described above, in this embodiment, since the molten metal 3 of the light alloy is supplied to the barrel 2, the mixing of gas in the initial stage is small. Further, since the supplied molten metal 3 is cooled while stirring inside the barrel 2 to generate the semi-solidified slurry 8, there is no variation in heat history such as shearing history as in the thixomolding method, and the molten state (State of semi-solidified slurry) is stabilized. In addition, the storage section 6 is formed at the lower portion of the screw extruder 7 arranged substantially vertically, and the semi-solidified slurry 8 is moved there by utilizing the head pressure from the supply port and its own weight. The semi-solidified slurry 8 can be temporarily stored without involving gas. The pressure is applied to the stored semi-solidified slurry 8 from the storage section 6 while applying a pressing force to the measuring section 13 having a predetermined volume. Pressure, the fluctuation of the head pressure on the supply port side does not affect the measurement, and the residual gas can be discharged to the low pressure supply port side, so that stable and highly accurate measurement can be performed. Further, since the starting material is the molten metal 3 which is conveyed downward while being cooled to the semi-solidified slurry 8, wear and breakage of the upstream portion of the extrusion screw 5 can be reduced, and the load torque of the screw extruder 5 can be reduced. In addition, it is not necessary to take a large stirring path and the size of the apparatus can be reduced.
[0043]
As described above, in the injection molding apparatus according to the present embodiment, the extruder screw 5 and the plunger 12 are linked in a series of operations, so that the measurement can be performed with high accuracy and the injection molding can be performed. The advance and retreat of the extrusion screw 5 and the plunger 12 are controlled by a hydraulic control device U shown in FIG.
[0044]
The operation of the hydraulic control device U during weighing will be described with reference to FIG. First, when the solenoid valve 40 connected to the screw hydraulic cylinder 19 enters, the pushing screw 5 is advanced. On the other hand, the solenoid valve 41 connected to the plunger hydraulic cylinder 23 also enters at the same time, causing the plunger 12 to retract. At this time, while the hydraulic pressures of both the extrusion screw 5 and the plunger 12 are measured by the sensors P1 and P2, respectively, the calculation is performed by the measuring pressure controller 45. Then, at least one of the electromagnetic pressure proportional valves 46 and 47 is controlled so that the relationship between the screw 5 side pressure and the plunger 12 side pressure is: screw 5 side pressure> plunger 12 side pressure and a constant positive pressure is always maintained. . At this time, the control parameter P1 of the hydraulic pressure on the screw 5 side and the hydraulic pressure on the plunger 12 side are set in advance so as to be able to cancel the frictional force of each hydraulic cylinder of the screw hydraulic cylinder 19 and the plunger hydraulic cylinder 23 and cancel them. It is preferable to set an initial value of the control parameter P2. By the operation of the hydraulic control device U, the semi-solidified slurry 8 in the barrel 2 moves toward the measuring section 13 and is pressed into the measuring section 13 in the cylinder while applying a constant positive pressure. Thus, the degassed and accurately measured semi-solid slurry is filled in the measuring section 13.
[0045]
In the present embodiment, the opening and closing of the communication channel 10 is performed by moving the extrusion screw 5 or the plunger 12 to a position where the communication channel 10 is closed. However, the injection molding apparatus according to the present invention is not limited thereto. However, the present invention is not limited to this. For example, a valve means may be provided in the communication channel 10 to intentionally open and close the communication channel. Also, a check valve can be used instead of the valve means. However, in this case, it is necessary to adopt a method in which the check valve is operated when the plunger 12 is ejected, and the plunger 12 is moved to a position that closes the communication flow path during the primary measurement.
[0046]
Further, the cooling means 9 is for cooling from the outer periphery of the barrel 2, but a cooling means inside the extrusion screw 5 can be further added. As a result, dendrites are generated not only near the inner wall of the barrel 2 but also near the extrusion screw 5, and when this is sheared and crushed by the extrusion screw 5, the homogeneity of the semi-solid slurry 8 is further improved. In addition, it is preferable that the temperature of the generated semi-solidified slurry is adjusted by a cooling unit so that the solid fraction is adjusted to be in a range of 5 to 40%. If the solid phase ratio is less than 5%, the state is almost the same as that of the liquid phase, and the merit of the semi-solid injection molded article is lost. If it exceeds 40%, the fluidity is deteriorated and the yield of the molded article is deteriorated.
[0047]
【The invention's effect】
As described above, according to the present invention, it is possible to injection-mold a high-quality light metal molded product with less air bubbles and shrinkage, so that a high-quality molded product by injection molding can be obtained at low cost.
[Brief description of the drawings]
FIG. 1 is an overall explanatory view showing an example of an embodiment of a light alloy injection molding apparatus according to the present invention.
FIG. 2 is a view showing a main part of an example of an embodiment of a light alloy injection molding apparatus according to the present invention, and is a view for explaining a molding step.
FIG. 3 is a view showing a main part of an example of an embodiment of a light alloy injection molding apparatus according to the present invention, and is a view for explaining a molding step.
FIG. 4 is a view showing a main part of an example of an embodiment of a light alloy injection molding apparatus according to the present invention, and is a view for explaining a molding step.
[Explanation of symbols]
U hydraulic control device
1 Injection molding equipment
2 barrels
3 Metal melt
4 Supply port
5 Extrusion screw
6 storage department
7 Screw extruder
8 Semi-solidified slurry
9 Cooling means
10 Communication channel
11 cylinder
12 plunger
13 Weighing section
14 Plunger injection machine
16 Nozzle part
17 Mold clamping device
19 Hydraulic cylinder for screw
20 Cylinder rod
21 Temperature control jacket
22 Valve means
23 Hydraulic cylinder for plunger

Claims (14)

A method for injection molding a light alloy having a substantially vertically installed barrel with an extrusion screw therein and a cylinder with a plunger inside communicating with the barrel via a communication flow path,
(A) a supply step of supplying a molten metal of a light alloy material from the supply port into the barrel;
(B) a transition step of cooling the molten metal into a semi-solidified slurry while stirring the molten metal with the extrusion screw in the barrel;
(C) a primary measuring step of closing the communication flow path and storing the semi-solidified slurry in a storage section formed by retracting the extrusion screw upward by a predetermined amount;
(D) opening the communication channel, and transferring the semi-solidified slurry into the cylinder via the communication channel until at least the plunger is retracted to a predetermined position to form a measuring section inside the cylinder. Upon extrusion, a secondary measuring step of retracting the plunger while advancing the extrusion screw so that a positive pressure is applied to the semi-solid slurry extruded into the cylinder,
(E) an injection step of injecting the semi-solidified slurry by advancing the plunger after closing the communication flow path;
Injection molding method of light alloy composed of The injection molding method for a light alloy according to claim 1, wherein the opening and closing of the communication channel are performed by a valve means provided in the channel. The closing of the communication channel in the primary measurement step is performed by moving the plunger to a position where the communication channel is closed, and the extrusion screw closes the communication channel in the injection step. The injection molding method for a light alloy according to claim 1, wherein the method is performed by moving to a closing position. In the secondary weighing step, the differential pressure between the hydraulic pressure when applying a forward force to the hydraulic cylinder for the screw that advances and retracts the extrusion screw and the hydraulic pressure when applying the retracting force to the hydraulic cylinder for the plunger that advances and retracts the plunger. The injection molding method for a light alloy according to any one of claims 1 to 3, wherein at least one of the pressures of the respective hydraulic lines is controlled so that is substantially constant. The molten metal of a light alloy is supplied from the outside to a hopper provided at the supply port, and after the temperature of the molten metal is made uniform, the molten metal is supplied to the inside of the barrel. 3. The injection molding method for a light alloy according to item 1. The light alloy according to any one of claims 1 to 5, wherein, in the transition step, the molten metal is cooled in the barrel such that a solid fraction of the semi-solid slurry is 5 to 40%. Injection molding method. 7. The injection molding method of a light alloy according to claim 6, wherein cooling of the molten metal is performed by cooling means provided on the barrel and the extrusion screw. A supply port through which the molten metal is supplied is provided at an upper portion of the barrel, and an extrusion screw rotatable inside the barrel and movable back and forth in the barrel axis direction is stored in the lower portion of the barrel by retreating the extrusion screw. A substantially vertically arranged screw extruder in which the part is formed;
Cooling means for cooling the molten metal supplied from the supply port into the barrel so as to be a semi-solid slurry,
A cylinder connected via a communication flow path provided at the lower end of the barrel has a plunger that can move forward and backward in the axial direction of the cylinder, and the plunger is retracted, so that a measuring unit is located forward in the cylinder. A light alloy injection molding device, comprising: a plunger injection machine formed and injecting the semi-solid slurry by advancing the plunger,
The light screw is configured such that the extrusion screw has a backflow preventing means at a tip portion, and is configured to temporarily store the semi-solidified slurry, and then advance and retreat by hydraulic pressure so as to press-in while applying a positive pressure to the measuring section. Injection molding equipment. 9. The injection molding apparatus for light alloy according to claim 8, wherein a valve means for opening and closing the communication flow path is provided in the communication flow path. The light extruder according to claim 8, wherein the extrusion screw includes a hydraulic cylinder having a stroke sufficient to move from a position forming the storage section to a position at which the communication flow path can be closed. Alloy injection molding equipment. The light alloy according to claim 8, wherein the plunger includes a hydraulic cylinder having a stroke sufficient to move from a position forming the measuring section to a position at which the communication flow path can be closed. Injection molding equipment. 9. The light alloy injection molding apparatus according to claim 8, wherein the plunger advances from a position where the measuring section is formed, and closes the communication channel when the injection is completed. The injection molding apparatus for a light alloy according to claim 8, wherein the cooling means is provided on the barrel and the extrusion screw. A screw hydraulic cylinder for moving the extrusion screw forward and backward, a plunger hydraulic cylinder for moving the plunger forward and backward, and when the semi-solid slurry is extruded from the storage section to the measuring section, the semi-solid extruded to the measuring section. Hydraulic pressure control means for controlling at least one of a hydraulic pressure when the hydraulic cylinder for screw is advanced so that a substantially constant positive pressure can act on the slurry, and a hydraulic pressure for the hydraulic cylinder for plunger when the plunger is retracted. The injection molding apparatus for a light alloy according to claim 8, wherein:

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