Injection device and injection molding machine

Abstract

To provide an injection device capable of appropriately monitoring temperature of pellets in a hopper.SOLUTION: An injection device includes: a hopper through which granular molding material passes vertically; a hopper block that supports the hopper; a heating cylinder that is supported by the hopper block directly below the hopper and is filled with the molding material that has passed through the hopper; a screw that moves backward inside the heating cylinder to plasticize the granular molding material, and then moves forward inside the heating cylinder to inject the plasticized molding material into a cavity; and a temperature sensor installed in the hopper block.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an injection device and an injection molding machine that inject a molding material into a mold. [Background technology]

[0002] Conventionally, there has been known an injection device that plasticizes granular pellets supplied through a hopper in a heating cylinder and injects the plasticized molten resin into a mold. In such an injection device, it is common to dry the pellets in advance to prevent the injection of molten resin containing moisture.

[0003] In order to solve such problems, there is a technique for drying the pellets in the hopper by heating the pellets in the hopper or blowing air toward the pellets in the hopper (see, for example, Patent Documents 1 to 6). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Utility Model Application Publication No. 60-194510 [Patent Document 2] Japanese Utility Model Application Publication No. 61-158410 [Patent Document 3] Japanese Utility Model Application Publication No. 62-104915 [Patent Document 4] Japanese Utility Model Application Publication No. 62-147510 [Patent Document 5] Japanese Utility Model Application Publication No. 63-056602 [Patent Document 6] Japanese Utility Model Application Publication No. 03-106011 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when a mechanism for drying the pellets in the hopper is installed, the structure of the injection device becomes complicated. Therefore, many production lines supply pellets that have been dried in advance in a separate device to the hopper. In such a case, a new problem arises in that the pellets absorb moisture from the air in the hopper. It is known that the temperature of the pellets that have absorbed moisture in the hopper drops.

[0006] The present invention has been made to solve such problems in the prior art, and its object is to provide an injection device that can properly monitor the temperature of pellets in a hopper. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the present invention provides an injection device that injects molding material into the cavity of a clamped mold, comprising a hopper that passes granular molding material in an upward and downward direction, a hopper block that supports the hopper, a heating cylinder that is supported by the hopper block directly below the hopper and is filled with the molding material that has passed through the hopper, a screw that retreats inside the heating cylinder to plasticize the granular molding material and advances inside the heating cylinder to inject the plasticized molding material into the cavity, and a temperature sensor installed in the hopper block. Effect of the Invention

[0008] According to the present invention, it is possible to obtain an injection device that can appropriately monitor the temperature of pellets in a hopper. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a side view of an injection molding machine according to an embodiment of the present invention. [Diagram 2] FIG. 2 is an exploded perspective view of a hopper block and a hopper sleeve. [Diagram 3] FIG. [Figure 4]1A is a bottom view of the sensor holder, and FIG. 1B is a cross-sectional view of the beam. [Diagram 5] FIG. 2 is a hardware configuration diagram of an injection molding machine. [Figure 6] 13 is a flowchart of a pellet monitoring process. [Figure 7] 1A is a perspective view of a hopper sleeve according to a modified example, FIG. 1B is a perspective view of a beam, and FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] An injection molding machine 10 according to the present invention will be described below with reference to the drawings. The injection molding machine 10 is a device that injects a measured amount of molding material into a mold to form an injection-molded product (hereinafter referred to as "injection molding").

[0011] [Configuration of injection molding machine 10] Fig. 1 is a side view of an injection molding machine 10 according to this embodiment. As shown in Fig. 1, the injection molding machine 10 mainly includes a mold clamping device 20, an injection device 30, and a control device 60 (see Fig. 5).

[0012] The clamping device 20 opens, closes, and clamps the mold 21. Specifically, the clamping device 20 mainly includes a fixed die plate 23 that supports a fixed-side mold 22, and a movable die plate 25 that supports a movable-side mold 24. The fixed-side mold 22 and the movable-side mold 24 are supported so as to face each other in the left-right direction (horizontal direction) of the injection molding machine 10.

[0013] The movable die plate 25 moves left and right along the tie bars 27 by transmitting the driving force of the die opening / closing motor 28 through the toggle link mechanism 26. When the movable die plate 25 moves leftward, the fixed die 22 and the movable die 24 move away from each other. On the other hand, when the movable die plate 25 moves rightward, the fixed die 22 and the movable die 24 come into contact with each other, forming a cavity (internal space) inside the die 21. Then, when pressure is further applied in a direction to move the movable die plate 25 rightward, the fixed die 22 and the movable die 24 are clamped.

[0014] The injection device 30 plasticizes, measures, and injects the molding material. The injection device 30 according to this embodiment is disposed apart from the mold clamping device 20 in the horizontal direction (to the right of the mold clamping device 20). The injection device 30 mainly includes a heating cylinder 31, a screw 32, a hopper 33, and a hopper block 34.

[0015] The heating cylinder 31 is a cylindrical member extending in the left-right direction of the injection molding machine 10. The heating cylinder 31 mainly includes a resin passage 35 and a nozzle 36. In addition, a band heater for heating the heating cylinder 31 is attached to the outer circumferential surface of the heating cylinder 31.

[0016] The resin passage 35 is a cylindrical space extending in the axial direction (longitudinal direction) inside the heating cylinder 31. The resin passage 35 communicates with the outside of the heating cylinder 31 (the cavity of the mold 21) through a nozzle 36 provided at the tip (front end) of the heating cylinder 31. In other words, the resin passage 35 is a space extending from the nozzle 36 along the axial direction.

[0017] The screw 32 is a cylindrical member. A spiral groove is formed on the outer circumferential surface of the screw 32. The screw 32 is accommodated in the internal space of the heating cylinder 31 in a state in which the screw 32 can move in the left-right direction of the injection molding machine 10 (hereinafter, referred to as "advance and retreat") and can rotate. The screw 32 advances and retreats when a driving force of an injection motor 37 is transmitted thereto, and rotates when a driving force of a metering motor 38 is transmitted thereto.

[0018] More specifically, when the injection motor 37 is rotated in the forward direction, the screw 32 moves (forward) toward the tip of the heating cylinder 31 (i.e., the nozzle 36). On the other hand, when the injection motor 37 is rotated in the reverse direction, the screw 32 moves (rearward) toward the base end of the heating cylinder 31 (i.e., the side opposite the nozzle 36). Hereinafter, within the range that the tip position of the screw 32 can reach within the heating cylinder 31, the position closest to the nozzle 36 is referred to as the "forward limit," and the position farthest from the nozzle 36 is referred to as the "rear limit." In addition, the terms "forward rotation" and "reverse rotation" of the injection motor 37 do not specify an absolute direction of rotation, but merely specify a relative relationship (i.e., forward rotation and reverse rotation are rotations in opposite directions).

[0019] The hopper 33 is a funnel-shaped member that passes the granular molding material in the vertical direction. More specifically, the hopper 33 is a truncated cone-shaped member having an upper end opening and a lower end opening. The upper end opening of the hopper 33 has a larger opening area than the lower end opening. The hopper block 34 is a member that supports the heating cylinder 31 and the hopper 33. The hopper block 34 also connects the lower end opening of the hopper 33 to the resin passage 35 of the heating cylinder 31, thereby supplying (filling) the molding material that has passed through the hopper block 34 to the resin passage 35.

[0020] [Configuration of the hopper block 34 and the hopper sleeve 40] Fig. 2 is an exploded perspective view of the hopper block 34 and the hopper sleeve 40. Fig. 3 is a perspective view of the sensor holder 43. Fig. 4 is a bottom view (A) of the sensor holder 43 and a cross-sectional view (B) of the beam 45.

[0021] As shown in FIG. 2, the hopper block 34 has a generally rectangular parallelepiped outer shape. The hopper block 34 is formed with a through passage 34a and a communication passage 34b. The through passage 34a passes through the hopper block 34 in the left-right direction (horizontal direction). The communication passage 34b extends downward from the upper surface of the hopper block 34 and communicates with the through passage 34a. The heating cylinder 31 is inserted through the through passage 34a and extends in the horizontal direction. The hopper 33 is supported by the hopper block 34 via a hopper sleeve 40 so that the lower end opening communicates with the communication passage 34b. That is, the heating cylinder 31 is supported by the hopper block 34 directly below the hopper 33.

[0022] As a result, the hopper 33 communicates with the resin passage 35 at a portion of the heating cylinder 31 closer to the base end than the tip end through the hopper block 34 and the hopper sleeve 40. The molding material stored in the hopper 33 is supplied to the resin passage 35 of the heating cylinder 31 through the lower end opening. In this embodiment, pellets (an example of a granular molding material) are supplied to the hopper 33, and the pellets are plasticized in the heating cylinder 31 to become molten resin (an example of a plasticized molding material). The pellets are dried in advance in a separate device, and are supplied to the hopper 33 at a predetermined temperature (e.g., 80°C).

[0023] The hopper sleeve 40 is a member inserted into the communication passage 34b. The hopper sleeve 40 has an internal space through which the pellets that have passed through the hopper 33 pass. The hopper sleeve 40 also supports a temperature sensor 66 that measures the temperature of the pellets passing through the internal space. The hopper sleeve 40 mainly includes a cylindrical portion 41, a flange portion 42, and a sensor holder 43, for example.

[0024] The cylindrical portion 41 has a cylindrical shape with both ends open in the axial direction. As another example, the cylindrical portion 41 may have a truncated cone shape with a diameter gradually decreasing from the upper end opening to the lower end opening. The cylindrical portion 41 is inserted into the communication passage 34b. The flange portion 42 is a ring-shaped portion that protrudes radially outward from the upper end opening of the cylindrical portion 41 and continues in the circumferential direction. The sensor holder 43 is detachably supported by the flange portion 42. The method of attaching the sensor holder 43 to the flange portion 42 is not particularly limited, and may be, for example, fastened by a bolt. The sensor holder 43 also supports a temperature sensor 66.

[0025] As shown in Figs. 3 and 4, the sensor holder 43 mainly includes, for example, a ring portion 44 and a beam 45. The ring portion 44 has a ring-shaped outer shape having an opening 46 through which the pellets pass. The ring portion 44 may be continuous in the circumferential direction, or may have a portion cut out in the circumferential direction. The ring portion 44 is fixed to the flange portion 42. Furthermore, the lower end of the hopper 33 is placed on the ring portion 44. That is, the opening 46 communicates with the internal space of the hopper 33 (is located directly below the internal space of the hopper 33).

[0026] The beam 45 is a long rod-like member extending linearly. The beam 45 is supported by the ring portion 44 so as to straddle the opening 46. That is, both ends of the beam 45 are fixed to different positions of the ring portion 44. More specifically, the beam 45 according to this embodiment is supported by the ring portion 44 so as to pass through the center C of the opening 46. However, the beam 45 does not necessarily have to pass through the center of the opening 46.

[0027] In the cross section of the beam 45 shown in Fig. 4(B) (cross section BB in Fig. 4(A)), the upper surface of the beam 45 has an upwardly convex arc shape. As a result, the width of the beam 45 in the short side direction becomes wider from the upper end to the lower end. However, the shape of the cross section of the beam 45 is not limited to Fig. 4(B) and may be a triangular shape, a semicircular shape, or the like.

[0028] An upwardly recessed recess 47 is provided on the lower surface of the beam 45. The temperature sensor 66 is housed in the recess 47. More specifically, the temperature sensor 66 is housed in the recess 47 at the position of the center C of the opening 46 (in other words, the position of the center in the longitudinal direction of the beam 45). Furthermore, a harness (not shown) extending from the temperature sensor 66 passes through the recess 47 and the lower surface of the beam 45, and is connected to the control device 60.

[0029] However, the installation position of the temperature sensor 66 is not limited to the above example, so long as it is within the hopper block 34. As one example, the beam 45 may be omitted, and the temperature sensor 66 may be installed at any position within the hopper sleeve 40. As another example, the hopper sleeve 40 may be omitted, and the temperature sensor 66 may be installed on a beam provided within the communication passage 34b (opening) of the hopper block 34. As yet another example, the hopper sleeve 40 and the beam 45 may be omitted, and the temperature sensor 66 may be installed at any position within the hopper block 34.

[0030] As a result, the pellets that have passed through the lower end opening of the hopper 33 pass through the opening 46 of the ring portion 44, the flange portion 42, and the cylindrical portion 41, and are supplied to the resin passage 35 of the heating cylinder 31. The pellets that have climbed onto the upper surface of the beam 45 are guided to the opening 46 along the arc-shaped upper surface of the beam 45. The temperature of the pellets is transmitted to the temperature sensor 66 through the beam 45. For this reason, it is desirable that the beam 45 is made of a metal material with high thermal conductivity (e.g., SUS), but responsiveness must also be taken into consideration. The sensor holder 43 or the hopper sleeve 40 may be integrally molded from a metal material.

[0031] [Configuration of control device 60] Fig. 5 is a hardware configuration diagram of the injection molding machine 10. As shown in Fig. 5, the control device 60 includes a central processing unit (CPU) 61, which is a calculation means, and a memory 62. The memory 62 is, for example, a read only memory (ROM), a random access memory (RAM), a hard disk drive (HDD), or a combination of these. The control device 60 realizes processing described below by the CPU 61 reading and executing program codes stored in the memory 62. The memory 62 is also used as a work area when the CPU 61 executes the programs.

[0032] However, the specific configuration of the control device 60 is not limited to this, and may be realized by hardware such as an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA).

[0033] The control device 60 controls the overall operation of the injection molding machine 10. More specifically, the control device 60 controls the mold opening / closing motor 28, the injection motor 37, and the metering motor 38 based on various signals output from a rotary encoder 64, a load cell 65 (pressure sensor), a temperature sensor 66, and a display / input device 67.

[0034] The rotary encoder 64 is a sensor that detects the speed and tip position of the screw 32. More specifically, the rotary encoder 64 outputs a pulse signal corresponding to the rotation of the injection motor 37 to the control device 60. Then, the control device 60 specifies the speed of the screw 32 based on the number of pulse signals output per unit time. The control device 60 also specifies the tip position of the screw 32 based on the accumulated value of the pulse signals.

[0035] The load cell 65 is a sensor that detects the pressure applied to the screw 32. More specifically, the load cell 65 outputs a pressure signal (voltage value) corresponding to the pressure applied to the screw 32 to the control device 60. Then, the control device 60 identifies the pressure applied to the screw 32 based on the pressure signal output from the load cell 65.

[0036] The temperature sensor 66 detects the surrounding temperature and outputs a temperature signal indicating the detected temperature through the harness to the control device 60. More specifically, the temperature sensor 66 detects the temperature of the pellets passing through the opening 46 of the ring portion 44.

[0037] Furthermore, a display input device 67 is connected to the control device 60. The display input device 67 is a user interface that includes a display (display device, notification device) that displays various information to be notified to the operator, and buttons, switches, dials, etc. (input devices) that accept input operations by the operator. The display input device 67 may also include a touch panel superimposed on the display. The display input device 67 accepts input operations by the operator, and outputs an input signal corresponding to the accepted input operation to the control device 60.

[0038] The control device 60 causes the injection molding machine 10 to execute an injection process. The injection process is a process in which the screw 32 advances and retreats within the heating cylinder 31 to repeatedly inject molten resin into the cavity. More specifically, the injection process is a process in which the following steps are repeatedly executed.

[0039] First, the control device 60 rotates the injection motor 37 in the reverse direction and rotates the metering motor 38. As a result, the screw 32 moves backward while rotating, and the pellets supplied through the hopper 33 are filled (metered) into the resin passage 35 ahead of the screw 32 while being plasticized. The control device 60 also rotates the injection motor 37 in the forward direction. As a result, the screw 32 moves forward, and the plasticized molten resin ahead of the screw 32 is injected into the cavity of the mold 21 through the nozzle 36. Furthermore, the control device 60 drives the mold opening / closing motor 28 to open the mold 21, causes the robot arm (not shown) to take out the injection-molded product in the fixed mold 22, and drives the mold opening / closing motor 28 to clamp the mold 21.

[0040] [Pellet monitoring process] Fig. 6 is a flowchart of the pellet monitoring process. The pellet monitoring process is a process for monitoring the temperature of the pellets passing through the hopper sleeve 40. After the control device 60 is powered on, the control device 60 always executes the pellet monitoring process shown in Fig. 6.

[0041] First, the control device 60 initializes (=0) a variable N stored in the memory 62 (S11). The variable N is a variable for counting the number of times that the temperature T detected by the temperature sensor 66 consecutively becomes less than the first threshold value Tth1.

[0042] Next, the control device 60 compares the temperature T detected by the temperature sensor 66 with a first threshold value Tth1 and a second threshold value Tth2 (S12 & S14). The first threshold value Tth1 is set to a temperature at which it can be evaluated that the pellets have absorbed moisture to an extent that would affect the quality of the injection-molded product. The second threshold value Tth2 is set to a value obtained by subtracting a predetermined value from the temperature of the pellets when they are dried by a separate device, although this is not enough to affect the quality of the injection-molded product. In addition, the second threshold value Tth2 is a value higher than the first threshold value Tth1.

[0043] Next, when the temperature T becomes less than the second threshold value Tth2 (S12: Yes), the control device 60 notifies the operator of the drop in the pellet temperature via the display / input device 67 (S13). Furthermore, when the temperature T becomes less than the first threshold value Tth1 (S14: Yes), the control device 60 adds 1 to the variable N (S15).

[0044] Next, when the variable N is the predetermined number of times Nth (S16: No), the control device 60 returns to the process of step S12 without initializing the variable N. Then, the control device 60 repeatedly executes the processes of steps S12 to S16 until the variable N reaches the predetermined number of times Nth (S16: Yes) or the temperature T becomes equal to or greater than the second threshold value Tth2 or the first threshold value Tth1 (S12: No / S14: No).

[0045] Then, when the variable N reaches a predetermined number of times Nth (S16: Yes), the control device 60 stops the rotation operation of the screw 32 (S17), but continues the pellet monitoring process. That is, the control device 60 stops the injection process when the temperature T repeatedly detected by the temperature sensor 66 is less than the first threshold value Tth1 for a predetermined number of times Nth consecutively. The predetermined number of times Nth is an arbitrary integer equal to or greater than 2.

[0046] On the other hand, when the temperature T is equal to or greater than the second threshold value Tth2 (S12: No) or when the temperature T is equal to or greater than the first threshold value Tth1 (S14: No), the control device 60 returns to the process of step S11 while continuing the operation of the injection molding machine 10. That is, when the temperature T returns to equal to or greater than the first threshold value Tth1 or the second threshold value Tth2, the variable N that has been counted up until now is initialized.

[0047] [Effects of this embodiment] According to the above embodiment, by attaching the temperature sensor 66 to the beam 45 spanning the opening 46, it is possible to appropriately monitor the temperature of the pellets supplied from the hopper 33 to the opening 46. As a result, it is possible to prevent the molten resin containing moisture from being injected into the mold 21, thereby preventing deterioration in the quality of the injection molded product.

[0048] Furthermore, according to the above embodiment, by gradually increasing the width of the beam 45 from the upper end to the lower end, it is possible to prevent the pellets from remaining on the upper surface of the beam 45 and to ensure space to accommodate the temperature sensor 66.

[0049] Furthermore, according to the above embodiment, by arranging beam 45 so as to pass through center C of opening 46, the average temperature of the plurality of pellets that have passed through hopper 33 can be detected by temperature sensor 66. Furthermore, by arranging temperature sensor 66 at the position of center C of opening 46, the above-mentioned action and effect become even more remarkable.

[0050] Furthermore, according to the above embodiment, when the temperature T detected by the temperature sensor 66 falls below the first threshold value Tth1, the injection process is stopped. This makes it possible to prevent pellets whose temperature has decreased by absorbing moisture in the air from being supplied into the heating cylinder 31, thereby preventing deterioration in the quality of the injection molded product.

[0051] The temperature T detected by the temperature sensor 66 drops not only when the temperature of the pellets remaining in the hopper 33 drops, but also when the number of pellets in the hopper 33 decreases. If the screw 32 is rotated and retracted when no pellets are supplied to the resin passage 35, the screw 32 may shake in the heating cylinder 31, causing galling. Thus, by executing the process of step S14: Yes→S17, galling of the screw 32 can be prevented.

[0052] Furthermore, by executing step S17 when the state in which the temperature T is less than the first threshold value Tth1 continues for a predetermined number of times Nth, it is possible to prevent the injection process from being stopped when the temperature T detected by the temperature sensor 66 merely drops momentarily. However, the processes of steps S11 and S15-S16 may be omitted, and the process may proceed directly to step S17 if the determination in step S14 is Yes.

[0053] Furthermore, according to the above embodiment, when the temperature T detected by the temperature sensor 66 falls below the second threshold value Tth2, the drop in pellet temperature is notified through the display / input device 67, so that the operator can be prompted to take action before the injection process is stopped. This makes it possible to reduce the downtime of the injection molding machine 10.

[0054] [Variations] 7A is a perspective view of a hopper sleeve 40A according to a modified example, (B) is a perspective view of a beam 45A, and (C) is a cross-sectional view of the beam 45A. Note that detailed description of commonalities with the above embodiment will be omitted, and differences will be mainly described. First, in the hopper sleeve 40A according to the modified example, the flange portion 42 and the ring portion 44 according to the above embodiment are integrated, and a ring portion 44A is provided at the upper end of the cylindrical portion 41. Also, the upper surface of the beam 45A according to the modified example has both ends in the short direction C-chamfered.

[0055] The above-described embodiments are illustrative examples of the present invention, and are not intended to limit the scope of the present invention to these embodiments. Those skilled in the art can implement the present invention in various other forms without departing from the gist of the present invention. [Explanation of symbols]

[0056] 10... injection molding machine, 20... mold clamping device, 21... mold, 22... fixed side mold, 23... fixed die plate, 24... movable side mold, 25... movable die plate, 26... toggle link mechanism, 27... tie bar, 28... mold opening / closing motor, 30... injection device, 31... heating cylinder, 32... screw, 33... hopper, 34... hopper block, 34a... through passage, 34b... connecting passage, 35... resin passage, 36... nozzle, 37... injection motor, 38... metering motor, 40, 40A... hopper sleeve, 41... cylindrical portion, 42... flange portion, 43... sensor holder, 44, 44A... ring portion, 45, 45A... beam, 46... opening, 47... recess, 60... control device, 61... CPU, 62... ROM, 63... RAM, 64... rotary encoder, 65... load cell, 66... ​​temperature sensor, 67... display input device

Claims

1. In an injection device that injects a molding material into a cavity of a clamped mold, A hopper through which granular molding material passes in a vertical direction; A hopper block supporting the hopper; a heating cylinder supported by the hopper block immediately below the hopper and filled with the molding material that has passed through the hopper; a screw that moves backward inside the heating cylinder to plasticize the granular molding material and moves forward inside the heating cylinder to inject the plasticized molding material into the cavity; and a temperature sensor disposed in the hopper block.

2. The hopper block includes a beam provided so as to span an opening through which the granular molding material that has passed through the hopper passes, 2. The injection device according to claim 1, wherein the temperature sensor is attached to the beam.

3. A hopper sleeve is interposed between the hopper and the hopper block, The hopper sleeve is a ring portion having the opening through which the granular molding material that has passed through the hopper passes; The injection device according to claim 2 , further comprising: the beam supported by the ring portion so as to straddle the opening.

4. 3. The injection device according to claim 2, wherein the temperature sensor is accommodated in a recess provided on a lower surface of the beam.

5. 5. The injection device according to claim 4, wherein the width of the beam in the short side direction becomes wider from the upper end to the lower end.

6. 3. The injection device according to claim 2, wherein the beam is supported by the hopper block so as to pass through a center of the opening.

7. The injection device according to claim 1 ; a control device that executes an injection process in which the screw is advanced and retreated within the heating cylinder to repeatedly inject the plasticized molding material into the cavity, The control device stops the injection process when the temperature detected by the temperature sensor becomes lower than a first threshold value.

8. 8. The injection molding machine according to claim 7, wherein the control device stops the injection process when the temperature repeatedly detected by the temperature sensor is lower than the first threshold value a predetermined number of times in succession.

9. A notification device is provided for notifying information, The injection molding machine according to claim 7, characterized in that the control device notifies the alarm device of a decrease in temperature of the granular molding material when the temperature detected by the temperature sensor becomes lower than a second threshold value that is higher than the first threshold value.

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