JP2018158503A - Operation method of injection device comprising plasticizing device and plunger type injection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an operation method of an injection device capable of maintaining a quality of a plasticized resin constant.SOLUTION: An operation method is directed to an injection device (1) comprising a plasticizing device (2) and a plunger type injection device (4). A resin pressure sensor (12) is provided in the vicinity of a tip of the plasticizing device (2). In the present invention, when a plunger (16) is retracted and resin from the plasticizing device (2) is weighed for the plunger type injection device (4), a back pressure of the plunger (16) is controlled so that a resin pressure of the plasticizing device (2) reaches a predetermined target value of resin pressure. In particular, in this operating method, the injection device (1) comprises the plasticizing device (2), first and second plunger type injection devices (4, 5), an injection portion (8), and a flow path switching device (7) connecting these components, and it is preferable to target the injection device (1) which alternately weighs and injects into the first and second plunger type injection devices (4, 5).SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for operating an injection device, and more particularly to a method for operating an injection device including a plasticizing device for melting resin and a plunger type injection device for measuring and injecting molten resin.

  The injection device can be roughly divided into an inline screw type injection device provided with a screw and a plunger type injection device provided with a plunger. The in-line screw type injection device is configured such that the resin is plasticized, measured, and injected in the injection device. That is, plasticization and injection are performed in the same apparatus. On the other hand, the plunger type injection device is divided into two types. In other words, the plunger type injection device includes a plunger type injection device in which plasticization and injection of resin are performed in the same device, and plasticization of resin is performed in different devices. There is also a plunger type injection device. In the latter plunger type injection device, plasticization is carried out by a plasticizing device, and the resin plasticized by this plasticizing device is metered into the plunger type injection device and injected. Since the injection device composed of such a plasticizing device and a plunger type injection device is provided with the plasticizing device independently, it is not necessary to interrupt the plasticizing of the resin even in the injection process, and the plasticizing device is continuously plasticized. Can be implemented. That is, there is an excellent feature that the quality of the molten resin can be made constant. There are various injection devices composed of such a plasticizing device and a plunger type injection device. For example, Patent Documents 1 and 2 have proposed.

Japanese Patent No. 3062629 Japanese Patent No. 2786243

  As shown in FIG. 5A, an injection device 51 described in Patent Document 1 includes a plasticizing device 52 that plasticizes or melts a resin, and an accumulator device 53 that temporarily stores the molten resin. The plunger type injection device 54 for injecting molten resin. The plasticizing device 52 includes a heating cylinder 56 and a screw 57, and the resin supplied from the hopper 58 is melted and sent forward. The accumulator device 53 includes a cylinder 60 and a plunger 61 driven by a predetermined driving device, and the resin melted in the plasticizing device 52 is supplied to the cylinder 60. The plunger type injection device 54 includes an injection cylinder 63 and an injection plunger 64 driven by a predetermined driving device, and an injection nozzle 65 is provided at the tip of the injection cylinder 63. A first opening / closing valve 67 is interposed in the flow path connecting the accumulator device 53 and the injection cylinder 63, and a second opening / closing valve 68 is interposed in the flow path connecting the injection cylinder 63 and the injection nozzle 65. . The operation of the injection device 51 is as follows. First, it starts from the state where the first opening / closing valve 67 is closed. When the screw 57 is rotated by the plasticizing device 52 to plasticize the resin, the resin is supplied to the cylinder 60 of the accumulator device 53 and the plunger 61 moves backward. When a predetermined amount of resin is accumulated at the tip of the cylinder 60, the first on-off valve 67 is opened and the second on-off valve 68 is closed. Then, the plunger 61 is driven in the axial direction. Then, resin is supplied to the injection cylinder 63 of the plunger type injection device 54, and the injection plunger 64 moves backward. At this time, since the plasticizing device 52 continues plasticizing, the resin from the plasticizing device 52 is also supplied to the plunger-type injection device 54. Even when the plunger 61 reaches the stop position, the resin from the plasticizing device 52 is continuously supplied to the plunger type injection device 54. When the injection plunger 64 moves backward and the necessary amount of resin is measured in the plunger type injection device 54, the first opening / closing valve 67 is closed. The second opening / closing valve 68 is opened, the injection plunger 64 is driven, and an injection process for injecting resin from the injection nozzle 65 is performed. By the way, immediately after the first opening / closing valve 67 is closed, the resin melted by the plasticizing device 51 is sent to the accumulator device 53 and the accumulation of the resin is started. This resin is used for the next injection. In this manner, the resin can be continuously plasticized in the plasticizer 51. Thereafter, the same operation is performed.

  As shown in FIG. 5A, the injection device 71 described in Patent Document 2 includes a plasticizing device 72 that plasticizes or melts a resin, and first and second plungers that inject the molten resin. Type injection devices 73 and 74. The plasticizer 72 includes a heating cylinder 76 and a screw 77, and melts the resin supplied from the hopper 78. The first and second plunger type injection devices 73 and 74 are composed of injection cylinders 80 and 81 and injection plungers 82 and 83, and measure and inject the resin melted in the plasticizing device 72. Yes. A flow switching valve 85 is provided at the tip of the plasticizing device 72, and the first and second plunger injection devices 73 are branched from the flow switching valve 85 to the first and second resin supply channels 86 and 87. , 74, respectively. Depending on the switching position of the channel switching valve 85, one of the first and second resin supply channels 86, 87 communicates with the plasticizing device 72 and the other is shut off. In this injection device 71, the resin injected from the first and second plunger injection devices 73 and 74 is injected from the injection nozzle 91 via the first and second injection flow paths 89 and 90. However, first and second on-off valves 93 and 94 are interposed in the first and second injection flow paths 89 and 90, respectively. The injection device 71 operates as follows. In a state where the first on-off valve 93 is closed, the flow path switching valve 85 is operated to connect the plasticizing device 72 and the first resin supply flow path 86. Then, the resin plasticized and melted by the plasticizing device 72 is supplied to the first plunger type injection device 73, and the injection plunger 82 moves backward. When the predetermined amount is measured, the flow path switching valve 85 is operated to cause the plasticizer 72 and the second resin supply flow path 87 to communicate with each other. That is, the first resin supply channel 86 is blocked. At this time, the second on-off valve 94 is closed in advance. Then, the resin plasticized by the plasticizing device 52 is supplied to the second injection device 74, and measurement is started in the second plunger type injection device 74. The first on-off valve 93 is opened, and the injection plunger 82 is driven in the first plunger type injection device 73 to perform the injection process. After injection, a pressure holding process is performed for a predetermined time, and the first on-off valve 93 is closed. While the injection process and the pressure holding process are performed in the first plunger type injection device 73, the necessary resin is measured in the second plunger type injection device 74. When the metering is completed, the flow switching valve 85 is operated to connect the plasticizing device 72 and the first resin supply flow path 86. Thereby, the metering in the first plunger type injection device 73 is started. The second on-off valve 94 is opened and the injection plunger 83 of the second plunger type injection device 74 is driven to perform the injection process. After performing the pressure holding process for a predetermined time, the second on-off valve 94 is closed. When the necessary resin is metered in the first plunger type injection device 73, the flow path switching valve 86 is switched. Thereafter, the same operation is performed.

  Both the injection device 51 described in Patent Document 1 and the injection device 71 described in Patent Document 2 can plasticize the resin continuously in the plasticizing devices 52 and 72. That is, since the plasticizing process is not interrupted by the injection process and the pressure holding process, the cycle time of the molding cycle can be shortened. However, there are also problems to be solved. Since these injection devices 51 and 52 can continuously plasticize the resin in the plasticizing devices 52 and 57, the quality of the molten resin should be kept constant. However, strictly speaking, there is a problem that the quality of the resin is not constant. For example, in the injection device 51, the resin plasticized by the plasticizing device 52 is first stored in the accumulator device 53. When the resin is stored, the plunger 61 as shown by reference numeral Z1 in FIG. Retreats. When the retraction amount Z1 is increased, the flow length of the resin is increased correspondingly and the flow resistance is increased, so that the pressure of the resin at the front end portion Y1 of the plasticizing device 52 is increased. In the injection device 51, the resin is metered in the plunger injection device 54 after the resin is accumulated in the accumulator device 53, but the injection plunger 64 moves backward as indicated by reference numeral Z2. When the retraction amount Z2 increases, the flow resistance of the resin increases accordingly, and the pressure of the resin at the front end Y1 of the plasticizing device 52 increases. As described above, the resin pressure at the distal end Y1 of the plasticizing device 52 varies depending on the retraction amounts Z1 and Z2 of the plunger 61 and the injection plunger 64, but the resin density is not constant due to the resin pressure variation. End up. Then, the quality of the resin to be plasticized will not be constant. The same applies to the injection device 71 described in Patent Document 2. When the first and second plunger-type injection devices 73 and 74 are retracted when the resin is weighed, the amount of resin Z depends on the size of the retraction amounts Z3 and Z4. The flow resistance changes, and the pressure of the resin at the tip Y2 of the plasticizer 72 changes accordingly. That is, the quality of the resin to be plasticized is not constant. The problem that the quality of the resin is not constant becomes remarkable particularly in a resin containing reinforcing fibers. This is because the resin containing the reinforcing fibers tends to expand by so-called springback, and therefore the density of the plasticized resin greatly changes when the pressure at the tip portions Y1 and Y2 of the plasticizing devices 52 and 72 changes. The kneading state of the reinforcing fiber and the resin changes due to the change in density. Furthermore, the reinforcing fibers are cut at a predetermined ratio during plasticization, but the length of the reinforcing fibers becomes non-uniform when the pressure at the tips Y1 and Y2 changes and the ratio of the fibers to be cut changes. There is also.

  By the way, in the injection devices 51 and 71 described in Patent Documents 1 and 2, there is a problem that the resin flow path through which the plasticized resin is sent to the plunger-type injection devices 54, 73 and 74 is long. For example, the flow path between the plasticizing device 52 and the plunger type injection device 54 includes the flow path of the accumulator device 53, and the plasticizing device 72 and the first and second plunger type injection devices 73 and 74. Between the first and second resin supply channels 86 and 87, there are provided. Since the resin flow path through which the plasticized resin is sent to the plunger-type injection devices 54, 73, 74 is long, the flow resistance increases accordingly, and the tip end portions of the plunger-type injection devices 54, 73, 74 Resin pressures of Y1 and Y2 are required.

  An object of the present invention is to provide a method of operating an injection device that solves the above-described problems. Specifically, an object of the present invention is to provide an operation method of an injection device that can maintain a constant quality of resin to be plasticized in an injection device composed of a plasticizing device and a plunger type injection device. Especially for injection devices where the resin flow path between the plasticizing device and the plunger type injection device is short, thereby reducing the loss of the flow resistance of the resin, the quality of the resin to be plasticized is within the desired range. It aims at providing the operating method of the injection device which can be maintained constant.

  In order to achieve the above object, the present invention is configured as an operation method for an injection device including a plasticizing device and a plunger type injection device provided with a plunger. The plasticizing device is provided with a resin pressure sensor in the vicinity of its tip so as to detect the resin pressure. In the present invention, when the plunger is moved backward to measure the resin from the plasticizing device to the plunger type injection device, the back pressure of the plunger is controlled so that the resin pressure of the plasticizing device becomes a predetermined resin pressure target value. Drive as you do. In particular, this operating method includes an injection device comprising a plasticizing device, first and second plunger type injection devices, a flow path switching device provided with an injection portion, and a single flow path switching valve connecting them. It is preferable to target an injection device that alternately measures and alternately injects two plunger-type injection devices.

That is, in order to achieve the above object, the invention described in claim 1 comprises a plasticizing device having a resin pressure sensor for detecting a resin pressure in the vicinity of the tip portion, and a plunger type injection device having a plunger. In the injection device, when the plunger is retracted and the resin from the plasticizing device is metered into the plunger type injection device, the plunger pressure is adjusted so that the resin pressure of the plasticizing device becomes a predetermined resin pressure target value. It is configured as an operation method of an injection device characterized by controlling back pressure.
The invention described in claim 2 is a plasticizing device provided with a resin pressure sensor for detecting a resin pressure in the vicinity of the tip portion, first and second plunger type injection devices provided with a plunger, and an injection portion for injecting resin. And a flow path switching device having one flow path switching valve, wherein the plasticizing device, the first and second plunger type injection devices, and the injection portion are connected to the flow path switching device, When the flow path switching valve is switched to the first position, the plasticizing device and the first plunger type injection device communicate with each other, and the second plunger type injection device and the injection unit communicate with each other. When the path switching valve is switched to the second position, the plasticizing device and the second plunger type injection device communicate with each other, and the first plunger type injection device and the injection unit communicate with each other. In the injection device, the flow path An operation of switching the valve to the first position to measure the resin from the plasticizing device to the first plunger type injection device and injecting the resin from the second plunger type injection device, and to the second position The operation of switching and metering the resin from the plasticizer to the second plunger type injection device and alternately injecting from the first plunger type injection device is performed, thereby plasticizing in the plasticizer When the resin is measured by retreating the plunger in each of the first and second plunger type injection devices, the resin pressure of the plasticizer becomes a predetermined resin pressure target value. Thus, it is configured as an operating method of the injection device, characterized by controlling the back pressure of the plunger.
According to a third aspect of the present invention, in the operation method according to the first or second aspect, the resin pressure target value is changed stepwise according to the retracted position of the plunger. Composed.

  As described above, the present invention is directed to an injection device that includes a plasticizing device that includes a resin pressure sensor that detects a resin pressure in the vicinity of the tip portion, and a plunger-type injection device that includes a plunger. That is, except for the point that a plastic pressure sensor is required for the plasticizing device, all general injection devices including the plasticizing device and the plunger type injection device are targeted. The present invention controls the back pressure of the plunger so that the resin pressure of the plasticizer becomes a predetermined resin pressure target value when the plunger is moved backward to measure the resin from the plasticizer to the plunger injection device. Configured as follows. This control guarantees that the resin pressure near the tip of the plasticizer during measurement is a predetermined resin pressure target value, that is, a constant pressure. Therefore, at any timing during measurement, the resin pressure to be plasticized The specific gravity and quality are guaranteed to be constant. Accordingly, it is possible to inject a resin having a constant quality, and it is guaranteed that a molded product having a uniform quality can be obtained. According to another invention, a plasticizing device provided with a resin pressure sensor for detecting a resin pressure in the vicinity of the tip portion, first and second plunger type injection devices provided with a plunger, an injection unit for injecting resin, And a plasticizer, the first and second plunger type injection devices, and the injection unit are connected to the flow switching device, and the flow switching valve is the first flow switching device. When switched to the position, the plasticizing device communicates with the first plunger type injection device and the second plunger type injection device communicates with the injection unit, and when the flow path switching valve is switched to the second position, And the second plunger type injection device communicate with each other, and the first plunger type injection device and the injection unit communicate with each other. Such an injection apparatus is simple because the flow path switching device includes only one flow path switching valve, and has an excellent feature that the flow length of the resin is short. Since the flow length is relatively short, the flow resistance of the resin causing the loss of the resin pressure is small, which is advantageous in plasticizing the resin. The injection device switches the flow path switching valve to the first position, measures the resin from the plasticizing device to the first plunger type injection device, and injects the resin from the second plunger type injection device. And the operation of metering the resin from the plasticizing device to the second plunger type injection device and injecting the resin from the first plunger type injection device are carried out alternately, whereby in the plasticizing device Plasticization is carried out continuously. According to the present invention, when the resin is weighed by retracting the plunger in each of the first and second plunger type injection devices, the plunger pressure is set so that the resin pressure of the plasticizing device becomes a predetermined resin pressure target value. It is configured to control back pressure. In other words, the plasticizing device continuously performs plasticizing without interruption in the middle, and the resin pressure near the tip of the plasticizing device is guaranteed to be a predetermined resin pressure target value. As a result, the resin to be plasticized is always guaranteed to have a certain quality. That is, it is possible to measure and inject a resin having a constant quality. As a result, a molded product of uniform quality can be formed. According to another invention, the resin pressure target value is configured to change stepwise according to the retracted position of the plunger. The injection device is provided with a flow channel switching device, and it is necessary to switch the flow channel when measurement is completed, but it is difficult to switch if the resin pressure in the vicinity of the flow channel switching device is high. Therefore, according to the present invention, for example, when the retracted position of the plunger approaches the measurement completion position during measurement, the resin pressure target value is changed to a small value. Then, the resin pressure in the vicinity of the flow path switching device is temporarily reduced, and the flow path can be easily switched.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows typically the injection apparatus which concerns on embodiment of this invention, The (a), (b) is that the flow-path switching valve of a flow-path switching apparatus is each switched to the 1st, 2nd position. It is sectional drawing which shows an injection device when it is. It is a block diagram explaining the control method of the operating method of the injection device concerning an embodiment of the invention. The (a) is when the conventional injection device operation method is implemented, and (b) is the plasticizer tip when the injection device operation method according to the embodiment of the present invention is implemented. It is a graph which shows the resin pressure of this, the flow resistance of the resin which flows through a flow path at the time of measurement, and the resin pressure of the plunger front-end | tip part of a plunger type injection device. It is sectional drawing which shows typically the plasticizing injection apparatus which concerns on other embodiment of this invention. It is a figure which shows a prior art example, (a), (a) is sectional drawing which shows the plasticizing injection apparatus of patent documents 1, 2, respectively.

  Embodiments of the present invention will be described below. The present invention relates to a method for operating an injection device, but is intended for a predetermined type of injection device. That is, the injection device targeted by the operation method according to the present invention is a plunger-type injection device, which is an injection device provided with a plasticizing device for plasticizing resin separately from the plunger-type injection device. FIG. 1 shows an injection apparatus 1 according to the present embodiment belonging to such a type. The injection device 1 includes a plasticizing device 2 that melts a resin, first and second plunger-type injection devices 4 and 5 that measure and inject the resin, a flow path switching device 7 that switches a resin flow path, It is comprised from the injection part 8 which inject | emits resin. That is, the plasticizing device 2 is provided separately from the plunger type injection devices 4 and 5. Furthermore, the injection device 1 according to the present embodiment is also characterized in that two plunger type injection devices 4 and 5 are provided.

  The plasticizing apparatus 2 includes a heating cylinder 10 and a screw 11 that rotates in the heating cylinder 10. The heating cylinder 10 is not shown in the figure, but a band heater is provided on the outer peripheral surface so as to be heated. It has become. When pellets of material are supplied from the hopper and the screw 11 is rotated, the pellets are melted and sent forward as molten resin. A resin pressure sensor 12 is embedded in the vicinity of the distal end portion of the plasticizing device 2 so that the resin pressure in the vicinity of the distal end portion of the plasticizing device 2 can be detected. In carrying out the driving method according to the present invention, it is an essential element.

  The first and second plunger type injection devices 4 and 5 are composed of injection cylinders 13 and 14 and plungers 16 and 17 driven in the axial direction within the injection cylinders 13 and 14. When measuring the resin supplied from the plasticizing apparatus 2, a predetermined back pressure is applied to the plungers 16 and 17. This control is an important point in the present invention and will be described later. In the first and second plunger-type injection devices 4 and 5, although not shown in the drawing, a pressure sensor is provided at the rear end of the plungers 16 and 17, and the back pressure of the plungers 16 and 17, that is, the plunger 16, The resin pressure at the tip of 17 can be accurately detected. The plungers 16 and 17 can be driven with high precision by a hydraulic mechanism or a servo motor, and can be controlled so that the back pressure of the plungers 16 and 17 detected by the pressure sensor becomes a predetermined back pressure. . When the resin is metered in the first and second plunger type injection devices 4 and 5, the plungers 16 and 17 are retracted. When the plungers 16 and 17 are driven in the axial direction after the completion of measurement, the resin is injected from the injection portion 8. The injection part 8 can be comprised from dies, such as T die, for example, and can also be comprised from an injection nozzle.

  The flow path switching device 7 is a device that connects the plasticizing device 2, the first and second plunger type injection devices 4, 5 and the injection portion 8, and is a flow for switching the resin flow path between these devices. It is a path switching mechanism. The flow path switching device 7 according to the present embodiment is formed in a substantially cubic shape, and a bore 19 is opened vertically from the upper surface of the cube. A valve body 20 to be described next is inserted into the bore 19, and a flow path switching valve 21 is constituted by these. By the way, in the flow path switching device 7, through-holes communicating with the bores 19 from the respective side surfaces are formed on the four side surfaces constituting the cube. That is, a resin flow path is formed. A plasticizing device 2, first and second plunger type injection devices 4, 5 and an injection nozzle 8 are connected to each of these resin flow paths.

  The valve body 20 has a cylindrical shape, and rotates smoothly in the bore 19. Two grooves having a predetermined length in the circumferential direction are formed on the outer peripheral surface of the valve body 20. These grooves are formed on the same height of the cylinder, and one groove is an arc in the range of 0 to 90 degrees when viewed from the central axis, and the other groove is in the range of 180 to 270 degrees. It is formed in the outer peripheral surface of the valve body 20 by predetermined depth so that it may become this circular arc. Such a valve body 20 is inserted into the bore 19, a first in-valve flow path 25 is formed from one groove and the bore 19, and a second in-valve flow path 26 is formed from the other groove and the bore 19. Will be composed. As described above, the valve body 20 can rotate in the bore 19 and can take two rotational positions, that is, first and second positions. Each of the plasticizing device 2, the first and second plunger-type injection devices 4, 5 and the injection nozzle 8 corresponds to the first and second in-valve channels 25 according to the first and second positions taken by the valve body 20. , 26 communicate with each other or are blocked. Specifically, when the valve body 20 is switched to the first position, as shown in FIG. 1A, the plasticizing device 2 and the first plunger injection device 4 are The second plunger type injection device 5 and the injection nozzle 8 communicate with each other. When the valve body 20 is switched to the second position, as shown in FIG. 1A, the plasticizing device 2 and the second plunger type injection device 5 are connected to the first position. The plunger type injection device 4 and the injection nozzle 8 communicate with each other. As described above, since the communication / blocking between the devices 2, 4, 5, and 8 is switched according to the rotational position of the valve body 20, the injection device 1 according to the present embodiment is continuously provided in the plasticizing device 2. While injecting the resin, the first and second plunger-type injection devices 4 and 5 can alternately measure and simultaneously inject from the injection nozzle 8.

  The operating method of the injection apparatus 1 according to the present embodiment is characterized in that the resin plasticized in the plasticizing apparatus 2 is operated so that the quality thereof is constant. Although the kind of resin made into object in this invention is not limited, it is resin containing a reinforced fiber that the effect of this invention appears most notably. Hereinafter, the operation method according to the present embodiment will be described on the assumption that the reinforced fiber-containing resin is plasticized, measured, and injected. Although a controller for controlling the injection device 1 is not shown in the figure, a target value of the resin pressure in the vicinity of the tip portion of the plasticizing device 1 is set in advance in the controller. Based on this resin pressure target value, the controller performs feedback control as shown in FIG. First, in the flow path switching device 7 according to the present embodiment, the flow path switching valve 21 is switched to the first position as shown in FIG. Then, the plasticizing device 2 and the first plunger type injection device 4 communicate with each other. A predetermined axial force is applied to the plunger 16 in advance. When the heating cylinder 10 is heated in the plasticizing device 2 and the screw 11 is rotated, the resin is melted and supplied to the first plunger type injection device 4. The controller calculates the deviation between the resin pressure target value and the resin pressure measurement value detected by the resin pressure sensor 12. The back pressure of the plunger 16 that is the operation amount is calculated by PID control so that this deviation is eliminated. Each element of the PID is such that the back pressure of the plunger 16 is reduced when the resin pressure measurement value is larger than the resin pressure target value, and the back pressure of the plunger 16 is when the resin pressure measurement value is smaller than the resin pressure target value. Is adjusted in advance so as to increase. The plunger 16 is driven by a drive mechanism such as a hydraulic mechanism or a servo motor so that the back pressure of the plunger 16 calculated by the control unit is obtained. Again, the controller calculates the deviation between the resin pressure target value and the resin pressure measurement value detected by the resin pressure sensor 12, and controls it similarly. With this control, the resin pressure near the tip of the plasticizing apparatus 2 is maintained at the resin pressure target value even if the plunger 16 is retracted by measurement. That is, it is kept constant. This is shown in the graph of FIG. As the retracted position of the plunger 16 changes from 0% to 100%, the flow length of the resin in the injection cylinder 13 increases, so the flow resistance of the resin increases monotonously as shown in the graph 28. On the other hand, when the back pressure of the plunger 16 is operated by the PID control described above, the resin pressure in the vicinity of the tip of the plasticizing device 2 is maintained constant as shown in the graph 30. By this control, the back pressure of the plunger 16 decreases as shown in the graph 29 as the plunger 16 moves backward. As a reference, a graph of FIG. 3A shows a conventional example in which the back pressure of the plunger 16 is fixed and plasticized and measured. When the back pressure of the plunger 16 is driven so as to be maintained at a constant value as shown in the graph 30, the metering advances and the plunger 16 moves backward, and as the flow length of the resin in the injection cylinder 13 becomes longer as shown in the graph 31. In addition, the flow resistance of the resin increases. Then, the resin pressure near the tip of the plasticizing apparatus 2 increases as shown in the graph 33. In this conventional example, since the pressure of the resin to be plasticized fluctuates, the kneading state of the reinforcing fiber and the resin becomes unstable. That is, the quality of the resin is not maintained constant. When the operation method according to the present embodiment is carried out, the resin pressure in the vicinity of the tip of the plasticizing device 2 becomes constant as shown in the graph 30, so that the kneaded state of the reinforcing fibers and the resin is stabilized. This ensures that a constant quality resin is metered into the first plunger injection device 4.

  When the metering is completed in the first plunger type injection device 4, the flow path switching valve 21 is switched to the second position as shown in FIG. Then, the plasticizing device 2 and the second plunger type injection device 5 communicate with each other. The plasticizer 2 is continuously operated to melt the resin. When metering to the second plunger type injection device 5, the controller performs the feedback control shown in FIG. 2 in the same manner as described above according to the set resin pressure target value. As a result, the quality of the resin to be plasticized in the plasticizer 2 becomes constant, and this resin is metered to the second plunger type injection device 5. By the way, when the flow path switching valve 21 is in the second position, the first plunger type injection device 4 and the injection nozzle 8 also communicate with each other. When metering is performed in the second plunger type injection device 5, the plunger 16 is driven in the axial direction in the first plunger type injection device 4 and injected. When the metering of the second plunger type injection device 5 is completed, the flow path switching valve 21 is switched to the first position as shown in FIG. Control is performed as described above, and the first plunger type injection device 4 measures. In the second plunger type injection device 5, the plunger 17 is driven in the axial direction for injection. Thereafter, the same operation is performed.

  The operation method of the injection device according to the present embodiment can be variously modified. For example, the injection device 1 to be operated can be modified. FIG. 4 shows an injection device 1 ′ in which only one plunger type injection device 4 is provided. The injection device 1 ′ is different from the injection device 1 according to the previous embodiment in the flow channel switching device 7 ′. However, when the flow channel switching device 7 ′ is switched, the plasticizing device 2 and the plunger type injection device 4 are used. Or the plunger-type injection device 4 and the injection unit 8 communicate with each other. Also in the injection apparatus 1 ′ according to this embodiment, the measured value of the resin pressure in the resin pressure sensor 12 provided at the tip of the plasticizing apparatus 2 can be controlled so as to become the resin pressure target value. The quality of the resin to be made can be made constant. The operating method of the injection device according to the present embodiment is such that, for example, in the conventional injection devices 51 and 72 shown in FIGS. This can be easily implemented by providing a pressure sensor.

  The operation method itself can be modified. The operation method of the injection device according to the present embodiment has been described so as to control the resin pressure in the vicinity of the front end portion of the plasticizing device 2 to be the resin pressure target value. That is, it has been described that the control is performed so as to be a constant value. The resin pressure target value may be changed in a stepwise manner according to the retracted position of the plungers 29 and 30 without being a fixed value. For example, when the back stroke of the plungers 29 and 30 is 0 to 80% in weighing, the resin pressure target value is controlled to 5 MPa, and after 80% when the back stroke approaches the measurement completion position, the resin pressure target value is 2 MPa. To do. If it does so, the resin pressure in the flow-path switching apparatus 7 will fall at the time of completion of measurement. If it falls, the effect that the flow-path switching valve 21 can be operated easily will be acquired.

  In the operation method of the injection device according to the present embodiment, it has been described that the plungers 16 and 17 require a pressure sensor for detecting the back pressure. However, a pressure sensor is not always necessary. This is because the back pressure can be indirectly detected from the driving force of the drive mechanism that drives the plungers 16 and 17, and the back pressure can be manipulated. When the drive mechanism is a hydraulic mechanism, the hydraulic pressure supplied is correlated with the back pressure of the plungers 16 and 17 when the drive mechanism is a servo motor. By detecting the hydraulic pressure and the current value and operating them, the back pressures of the plungers 16 and 17 are substantially operated.

1 Injection device
2 Plasticizing device 4 First plunger type injection device 5 Second plunger type injection device 7 Flow path switching device
8 Injection part 10 Heating cylinder
11 Screw 12 Resin pressure sensor 13, 14 Injection cylinder 16, 17 Plunger 21 Flow path switching valve

Claims (3)

In an injection device comprising a plasticizing device provided with a resin pressure sensor for detecting a resin pressure in the vicinity of the tip portion, and a plunger type injection device provided with a plunger,
When the plunger is retracted and the resin from the plasticizing device is metered into the plunger injection device, the back pressure of the plunger is controlled so that the resin pressure of the plasticizing device becomes a predetermined resin pressure target value. A method for operating an injection device. Plasticizing device provided with resin pressure sensor for detecting resin pressure in the vicinity of the tip, first and second plunger type injection devices provided with plungers, injection unit for injecting resin, and one flow path switching valve The plasticizing device, the first and second plunger type injection devices, and the injection section are connected to the flow switching device, and the flow switching valve is in a first position. The plasticizing device and the first plunger type injection device communicate with each other, the second plunger type injection device and the injection unit communicate with each other, and the flow path switching valve is in the second position. In the injection device in which the plasticizing device and the second plunger type injection device communicate with each other when switched, the first plunger type injection device and the injection unit communicate with each other.
An operation of switching the flow path switching valve to the first position to measure the resin from the plasticizing device to the first plunger type injection device and injecting the resin from the second plunger type injection device; And the operation of alternately metering the resin from the plasticizing device to the second plunger type injection device and injecting the resin from the first plunger type injection device. In an operating method for continuously carrying out plasticization in an apparatus,
In each of the first and second plunger type injection devices, when the resin is weighed by retreating the plunger, the back pressure of the plunger is adjusted so that the resin pressure of the plasticizing device becomes a predetermined resin pressure target value. An operation method of an injection device characterized by controlling.   3. The operation method according to claim 1, wherein the resin pressure target value is changed in a stepwise manner according to a retracted position of the plunger.

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