Injection molding machine

Abstract

To control a pressure of a resin material injected into a mold without compromising a design freedom of the mold.SOLUTION: An injection molding machine is provided with: an injection device 10 having a heating barrel 11 in which a screw 20 is disposed; a mold 75 for molding a resin material; an encoder 52 for detecting an injection speed S of the screw 20; a load cell 60 for detecting an injection pressure P acting on the screw 20; and a control device 100 for controlling a pressure of the resin material in the mold 75 by controlling a movement of the screw 20. The control device 100 has: a pressure loss calculation unit 111 for obtaining a pressure loss in the injection device 10 on a basis of a pressure loss model M and the injection speed S detected by the encoder 52; a virtual mold internal pressure calculation unit 112 for obtaining a virtual mold internal pressure V by subtracting the pressure loss from the injection pressure P; and a movement control unit 120 for controlling a movement of the screw 20 when injecting the resin material, and for controlling a movement on a basis of the virtual mold internal pressure V obtained by the virtual mold internal pressure calculation unit 112.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to an injection molding machine. [Background technology]

[0002] In an injection molding machine that performs molding by injecting molten resin into a mold, it is important to perform molding while maintaining the resin pressure at an appropriate value in order to perform appropriate molding. For this reason, in conventional injection molding machines, molding is performed while obtaining the value of the pressure of the molten resin by various methods. For example, in an injection pressure inspection device for an injection molding machine described in Patent Document 1, the pressure of the resin in the injection nozzle is calculated based on the pressure of the resin detected when purging is performed and the pressure of the resin detected when normal molding is performed, thereby accurately detecting the pressure of the resin in the cavity without being affected by the pressure loss in the heating cylinder.

[0003] In addition, in the molding condition creation method described in Patent Document 2, a resin pressure curve at the resin inlet or the end of the molding machine nozzle and an injection pressure curve when the nozzle is removed from the mold are obtained, thereby compensating for time delays and pressure losses due to the mechanical elements of the injection molding machine and obtaining molding conditions for mass production molding. In addition, in the resin evaluation method using an injection molding machine described in Patent Document 3, it is described that the injection pressure at a set screw position is detected by performing injection while changing the resin temperature and injection speed, and a function of the interdependence of pressure, speed, and temperature is obtained by the least squares method using N combination data of injection pressure, injection speed, and resin temperature.

[0004] In addition, the pressure control device for an injection molding machine described in Patent Document 4 executes an injection pressure control process for controlling the injection pressure in a pressure holding process, and an internal mold pressure control process for controlling the estimated internal mold pressure to a set internal mold pressure after executing the injection pressure control process, thereby suppressing the variation in the pressure inside the mold between molding cycles and enabling the molding of molded products of stable quality. In addition, by controlling the estimated internal mold pressure to a set internal mold pressure in the pressure holding process, the pressure inside the mold can be controlled with high responsiveness, preventing stress deformation of the molded product. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 11-115023 [Patent Document 2] JP 2000-355033 A [Patent Document 3] JP 2002-331558 A [Patent Document 4] JP 2016-159589 A Summary of the Invention [Problem to be solved by the invention]

[0006] Here, in injection molding using an injection molding machine, the type of resin material may be changed or the mold may be changed depending on the target molded product, but even when the type of resin material or the mold is changed, it is important to appropriately control the pressure of the resin material in the mold. In order to appropriately control the pressure of the resin material in the mold, it is necessary to acquire the pressure of the resin material. The pressure of the resin material can be detected, for example, by arranging a sensor for detecting pressure in the mold to detect the pressure of the resin material injected into the mold. However, when a pressure sensor is arranged in the mold, the design freedom of the mold is lost, so that the shape of the molded product may be restricted, or the layout of the cavity in the mold for molding the molded product may be restricted.

[0007] On the other hand, when injection molding is performed without arranging a pressure sensor in the mold, it becomes difficult to detect the pressure of the resin material injected into the mold with high accuracy and control the pressure. In this case, for example, when some gates in the mold are clogged, it becomes difficult to detect the increase in pressure of the resin material in the mold caused by the clogged gate, and burrs may occur as the pressure of the resin material increases. For these reasons, it has been difficult to control the pressure of the resin material injected into the mold without compromising the design freedom of the mold.

[0008] The present invention has been made in consideration of the above, and aims to provide an injection molding machine that can control the pressure of resin material injected into a mold without compromising the design freedom of the mold. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems and achieve the object, an injection molding machine according to the present invention includes an injection device that melts a resin material in a heated barrel with a screw disposed inside, and injects the resin material from the nozzle by moving the screw towards a side where a nozzle is located that injects the molten resin material, a mold having a cavity into which the resin material injected from the nozzle is filled and molding the resin material in the cavity, an injection speed detection unit that detects an injection speed that is the movement speed of the screw when the resin material is injected, an injection pressure detection unit that detects an injection pressure that is the pressure acting on the screw when the resin material is injected, and an injection device that detects an injection pressure that is the pressure acting on the screw when the resin material is injected, and ... a control device that controls the pressure of the resin material, the control device having a pressure loss calculation unit that calculates the pressure loss in the injection device when injecting the resin material based on a pressure loss model that indicates the pressure loss for each injection speed when the resin material is injected and the injection speed detected by the injection speed detection unit, a virtual mold internal pressure calculation unit that calculates a pressure obtained by subtracting the pressure loss calculated by the pressure loss calculation unit from the injection pressure detected by the injection pressure detection unit, as a virtual mold internal pressure, which is the pressure of the resin material in the mold, and a movement control unit that controls the movement of the screw when the resin material is injected, and performs the movement control based on the virtual mold internal pressure calculated by the virtual mold internal pressure calculation unit. Effect of the Invention

[0010] The injection molding machine according to the present invention has an advantage in that it is possible to control the pressure of a resin material injected into a mold without impairing the degree of freedom in designing the mold. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram showing an example of the configuration of an injection molding machine according to an embodiment. [Diagram 2] FIG. 2 is a detailed view of the injection device shown in FIG. [Diagram 3] FIG. 3 is a detailed view of the heating barrel shown in FIG. [Figure 4] FIG. 4 is a detailed view of the check ring shown in FIG. [Diagram 5] FIG. 5 is an explanatory diagram of the control device shown in FIG. [Figure 6] FIG. 6 is an explanatory diagram showing an example of a pressure loss model. [Figure 7] FIG. 7 is an explanatory diagram showing the relationship between each controller of the movement control section and the injection device. [Figure 8] FIG. 8 is an explanatory diagram showing the changes in injection speed, injection pressure, and virtual internal mold pressure when a non-defective product is molded. [Figure 9] FIG. 9 is an explanatory diagram showing a state in which the injection pressure has reached its upper limit in a case in which the control device does not have a virtual mold internal pressure determining unit and does not determine whether the virtual mold internal pressure has reached its upper limit. [Figure 10] FIG. 10 is an explanatory diagram showing a state in which the control device has a virtual internal pressure determination unit and the virtual internal pressure has reached an upper limit value. [Figure 11] FIG. 11 is an explanatory diagram showing the changes in injection speed, injection pressure, and virtual internal mold pressure when there is variation in the response of the check ring. [Figure 12] FIG. 12 is an explanatory diagram showing a state in which the virtual mold internal pressure reaches the upper limit when there is variation in the response of the check ring. [Figure 13] FIG. 13 is an explanatory diagram showing the injection speed, injection pressure, and virtual internal mold pressure when blow molding is performed without judging whether the virtual internal mold pressure has reached its upper limit. [Figure 14] FIG. 14 is an explanatory diagram showing the injection speed, injection pressure, and virtual internal mold pressure when blow molding is performed while judging whether the virtual internal mold pressure has reached its upper limit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of an injection molding machine according to the present disclosure will be described in detail with reference to the drawings. Note that the present invention is not limited to this embodiment. In addition, the components in the following embodiments include those that are replaceable and easily conceivable by a person skilled in the art, or those that are substantially the same.

[0013] [Embodiment] 1 is a schematic diagram showing a configuration example of an injection molding machine 1 according to an embodiment. In the following description, the up-down direction of the injection molding machine 1 in a normal use state is described as the up-down direction Z of the injection molding machine 1, the upper side of the injection molding machine 1 in a normal use state is described as the upper side of the injection molding machine 1, and the lower side of the injection molding machine 1 in a normal use state is described as the lower side of the injection molding machine 1. In the following description, the longitudinal direction Y of the injection molding machine 1 is also described as the longitudinal direction Y of each part having the injection molding machine 1, and the direction perpendicular to both the up-down direction Z and the longitudinal direction Y of the injection molding machine 1 is described as the width direction X of the injection molding machine 1.

[0014] <Injection molding machine 1> The injection molding machine 1 according to this embodiment has an injection unit 10 and a clamping unit 70, and the injection unit 10 and the clamping unit 70 are mounted on a frame 5 arranged at the lower end of the injection molding machine 1. The injection molding machine 1 melts a resin material into a plasticized material in the injection unit 10, and the plasticized material injected from the injection unit 10 is cooled and solidified by the clamping unit 70, thereby making it possible to manufacture various desired molded products.

[0015] The injection device 10 includes a heating barrel 11, a screw 20, a rotating mechanism 40, a forward / backward mechanism 50, and a propulsion mechanism 30. The heating barrel 11 is capable of heating and melting a resin material therein to form a plasticized material. The heating barrel 11 also includes a nozzle 12 at one end for injecting the plasticized material, and the other end is connected to a hopper 15 for feeding raw material. The screw 20 is disposed inside the heating barrel 11 and is capable of moving in the axial direction inside the heating barrel 11.

[0016] The rotation mechanism 40 is capable of introducing the resin material from the hopper 15 into the heating barrel 11 by rotating the screw 20 inside the heating barrel 11 .

[0017] The forward and backward movement mechanism 50 is capable of moving the screw 20 in the longitudinal direction Y within the heating barrel 11. In addition, the forward and backward movement mechanism 50 can extrude the resin material from the nozzle 12 by moving the screw 20 toward the nozzle 12 while the molten resin material is stored in the end portion of the heating barrel 11 where the nozzle 12 is located. This allows the resin material molten within the heating barrel 11 to be injected from the nozzle 12.

[0018] The mold clamping unit 70 has a fixed platen 71, a movable platen 72, a mold 75, a mold clamping drive mechanism 80, and an ejection mechanism 85. The fixed platen 71 is disposed on a frame 5 and fixed to the frame 5, and the movable platen 72 is disposed on the frame 5 on the opposite side of the fixed platen 71 from the side on which the injection unit 10 is located, and is disposed so as to be freely movable relative to the fixed platen 71.

[0019] The mold 75 has a cavity 75a filled with the resin material injected from the nozzle 12 of the heating barrel 11 of the injection device 10, and the resin material can be molded in the cavity 75a. The mold 75 for molding the resin material in this manner has a fixed mold 76 and a movable mold 77. The fixed mold 76 is attached to the surface of the fixed platen 71 on the side where the movable platen 72 is located, and the movable mold 77 is attached to the surface of the movable platen 72 on the side where the fixed platen 71 is located. The movable mold 77 attached to the movable platen 72 faces the fixed mold 76 attached to the fixed platen 71, and when the movable platen 72 approaches the fixed platen 71, it approaches the fixed mold 76 and is combined with the fixed mold 76.

[0020] The mold clamping drive mechanism 80 is capable of moving the movable platen 72 relative to the fixed platen 71, and by moving the movable platen 72 relative to the fixed platen 71, it is possible to close the movable mold 77 and the fixed mold 76, or to open the movable mold 77 and the fixed mold 76. In this embodiment, the mold clamping drive mechanism 80 includes a so-called toggle mechanism 81, which is capable of moving the movable platen 72 relative to the fixed platen 71.

[0021] The pushing mechanism 85 includes a pushing member 86 that pushes out the molded product that has been attached to the inner surface of the movable die 77 after molding, and enables the molded product to be removed from the movable die 77 after molding.

[0022] <Injection device 10> In the following description, the side on which the mold clamping device 70 is located relative to the injection device 10 in the longitudinal direction Y will be referred to as the front or front side, and the side opposite the side on which the mold clamping device 70 is located relative to the injection device 10 in the longitudinal direction Y will be referred to as the rear or rear side.

[0023] Fig. 2 is a detailed view of the injection device 10 shown in Fig. 1. The injection device 10 is disposed on the frame 5 via a propulsion mechanism 30. The propulsion mechanism 30 has a driving motor 31, and the driving force generated by the driving motor 31 enables the injection device 10 to move in the longitudinal direction Y relative to the frame 5.

[0024] The heating barrel 11 of the injection device 10 extends forward in the longitudinal direction Y, and a nozzle 12 is disposed at the tip, i.e., the front end of the heating barrel 11, in close contact with the mold 75. More specifically, the heating barrel 11 is formed in a substantially cylindrical shape, and is disposed with its axial direction oriented along the longitudinal direction Y, and is provided with a heater 13 such as a band heater. This allows the heating barrel 11 to melt the resin material inside. In other words, the heating barrel 11 can increase the temperature of the heating barrel 11 by the heater 13, and the resin material inside can be heated and melted to become molten resin, which is a plasticized material.

[0025] The screw 20 is disposed inside the heating barrel 11 and has a helical shape whose axial direction is along the axial direction of the heating barrel 11, that is, the screw 20 has a helical groove on the outer circumferential surface. Thus, the screw 20 formed in a helical shape is rotatable around the axial center in the heating barrel 11. Also, the screw 20 is movable in the axial direction of the rotation in the heating barrel 11. In other words, the screw 20 is disposed in the heating barrel 11 so that the central axis of the cylinder, which is the shape of the heating barrel 11, and the rotation axis of the screw 20 are approximately aligned, and the screw 20 is disposed so as to be movable in the axial direction of the heating barrel 11. The screw 20 rotatably disposed in the heating barrel 11 is capable of kneading the molten resin by rotating inside the heating barrel 11, and therefore the heating barrel 11 is a barrel capable of kneading the molten resin inside.

[0026] A hopper 15 is disposed at a position near the rear end of the heating barrel 11. The hopper 15 communicates with the inside of the heating barrel 11 and is capable of supplying pellets (not shown) which are granular resin material to the heating barrel 11.

[0027] The rotation mechanism 40 is disposed behind the heating barrel 11 in the longitudinal direction Y, and is capable of rotating the screw 20 disposed inside the heating barrel 11 about its central axis. The rotation mechanism 40 that rotates the screw 20 has a rotation mechanism main body 41, a driving motor 43, a transmission belt 44, and a pulley 45.

[0028] The driving motor 43 is disposed, for example, on the upper side of the rotating mechanism main body 41. The pulley 45 is disposed in front of the rotating mechanism main body 41 and rotatably disposed relative to the rotating mechanism main body 41 via a bearing 46. The pulley 45 is connected to the driving shaft of the driving motor 43 via a transmission belt 44, and the pulley 45 can be rotated by the driving force of the driving motor 43 transmitted via the transmission belt 44. In this way, the pulley 45, which can be rotated by the driving force transmitted from the driving motor 43, is fixed coaxially and integrally with the screw 20. In other words, the rear end side of the screw 20 in the longitudinal direction Y is connected to the pulley 45. As a result, the screw 20 disposed in the heating barrel 11 can be rotated integrally with the pulley 45 by the driving force transmitted from the driving motor 43 to the pulley 45.

[0029] A forward / backward movement mechanism 50 is disposed behind the rotation mechanism main body 41 in the longitudinal direction Y. The forward / backward movement mechanism 50 is capable of moving the screw 20 disposed in the heating barrel 11 in the axial direction of the screw 20. That is, the screw 20 can be advanced or retreated in the longitudinal direction Y. More specifically, the forward / backward movement mechanism 50 has a driving motor 51, a transmission belt 53, a pulley 54, and a ball screw mechanism 56.

[0030] The driving motor 51 has an encoder 52 that detects the rotational position and rotational speed of the driving motor 51, and the drive shaft of the driving motor 51 is connected to a pulley 54 via a transmission belt 53. The encoder 52 of the driving motor 51 can detect the position in the moving direction of the screw 20 when the resin material is injected from the nozzle 12 of the heating barrel 11 through the rotational position of the driving motor 51. The encoder 52 of the driving motor 51 can also detect the injection speed S, which is the moving speed of the screw 20 when the resin material is injected from the nozzle 12 of the heating barrel 11, by detecting the rotational speed of the driving motor 51. The encoder 52 of the driving motor 51 is also used as an injection speed detection unit that detects the injection speed S of the screw 20 in this way.

[0031] The pulley 54 is integrally connected to a screw portion 57 of a ball screw mechanism 56. The screw portion 57 of the ball screw mechanism 56 is disposed coaxially with the screw 20, and is also disposed coaxially with the pulley 45 of the rotation mechanism main body 41. The nut portion 58 of the ball screw mechanism 56 of the forward / reverse mechanism 50 is formed in a substantially cylindrical shape, and the screw portion 57 of the ball screw mechanism 56 is screwed into the nut portion 58.

[0032] A load cell 60 is disposed between the nut portion 58 of the ball screw mechanism 56 of the forward / rearward movement mechanism 50 and the rotation mechanism main body 41 of the rotation mechanism 40 in the longitudinal direction Y. The load cell 60 is disposed behind the rotation mechanism main body 41 of the rotation mechanism 40 and in front of the nut portion 58 of the ball screw mechanism 56 of the forward / rearward movement mechanism 50.

[0033] The load cell 60 is a load measuring device that measures a load applied in the axial direction, and is composed of a strain body and a strain sensor (both not shown) attached to the strain body. In this embodiment, the load cell 60 is arranged such that the axial direction is the longitudinal direction Y, and is formed in a substantially cylindrical shape that is flat in the longitudinal direction Y, and the inner diameter of the cylinder is larger than the outer diameter of the screw portion 57 of the ball screw mechanism 56 of the forward / reverse mechanism 50. The load cell 60 thus formed has a front surface in the longitudinal direction Y integrally fixed to the rotation mechanism main body 41 of the rotation mechanism 40, and a rear surface in the longitudinal direction Y integrally fixed to the nut portion 58 of the ball screw mechanism 56 of the forward / reverse mechanism 50.

[0034] The load cell 60 disposed between the rotation mechanism main body 41 of the rotation mechanism 40 and the nut portion 58 of the ball screw mechanism 56 of the forward / reverse mechanism 50 is capable of detecting the load acting in the longitudinal direction Y between the rotation mechanism main body 41 and the nut portion 58. The load cell 60 is used as an injection pressure detection portion that detects the injection pressure P, which is the pressure acting on the screw 20 when the resin material is injected from the nozzle 12 of the heating barrel 11, by detecting the load acting between the rotation mechanism main body 41 and the nut portion 58.

[0035] 3 is a detailed view of the heating barrel 11 shown in FIG. 2. As shown in FIG. 3, the heating barrel 11 is formed in a substantially cylindrical shape, and a heater 13 such as a band heater is disposed on the outer circumferential surface. The nozzle 12 disposed at the front end of the heating barrel 11 in the longitudinal direction Y is formed in a substantially cylindrical shape with an inner diameter smaller than the inner diameter of the heating barrel 11, and is disposed to open to the front side in the longitudinal direction Y. The screw 20 disposed in the heating barrel 11 has a flight 21 that protrudes outward in the radial direction of the screw 20 and is formed in a spiral shape centered on the axis of the screw 20. As a result, the screw 20 has a spiral groove-shaped portion between adjacent rotational portions of the flight 21 formed in a spiral shape.

[0036] A check ring 25 is disposed in the screw 20 formed in this manner near the front end in the longitudinal direction Y. The check ring 25 is disposed in a groove 22 formed in the screw 20 near the front end in the longitudinal direction Y. The groove 22 has a groove width direction that is aligned with the axial direction of the screw 20, and is a groove formed around one revolution in the circumferential direction of the screw 20.

[0037] FIG. 4 is a detailed view of the check ring 25 shown in FIG. 3. The check ring 25 is formed in a substantially cylindrical shape and is disposed in the groove portion 22 of the screw 20 with its axis substantially coinciding with the axis of the screw 20. The check ring 25 formed in a substantially cylindrical shape has an outer diameter that is approximately the same as the inner diameter of the heating barrel 11 and is slightly smaller than the inner diameter of the heating barrel 11. The inner diameter of the check ring 25 is larger than the diameter of the groove bottom of the groove portion 22 of the screw 20, and a gap is formed between the inner peripheral surface of the check ring 25 and the groove bottom of the groove portion 22 of the screw 20. The width of the check ring 25 in the axial direction is smaller than the groove width of the groove portion 22 of the screw 20. For this reason, the check ring 25 is capable of moving in the groove width direction within the groove portion 22.

[0038] Further, the screw 20 is formed with a communication portion 24 that communicates between a portion forward of the groove portion 22 in the longitudinal direction Y and the inside of the groove portion 22. The communication portion 24 opens into a groove wall 23 on the front side of the groove portion 22 in the groove width direction.

[0039] <Control device 100> The injection molding machine 1 has a control device 100 that performs various controls of the injection molding machine 1, an input unit 160 through which an operator performs input operations to the injection molding machine 1, and a display unit 170 that displays various information. Both the input unit 160 and the display unit 170 are connected to the control device 100, and the input unit 160 transmits the input information to the control device 100. The display unit 170 displays the information transmitted from the control device 100. The input unit 160 and the display unit 170 may be configured separately, or may be formed integrally by being configured as a so-called touch panel type display.

[0040] The control device 100 is connected to various actuators such as a motor that serves as a power source for the operation of the injection molding machine 1, and various sensors that acquire information during the operation of the injection molding machine 1. This allows the control device 100 to control the injection molding machine 1 by transmitting control signals to the actuators of the injection molding machine 1 while acquiring information during the operation of the injection molding machine 1 using the sensors. The control device 100 is capable of controlling the pressure of the resin material in the mold 75, for example, by controlling the movement of the screw 20 when the molten resin material is injected from the nozzle 12 of the heating barrel 11.

[0041] Fig. 5 is an explanatory diagram of the control device 100 shown in Fig. 1. The control device 100 has a processing unit 110, a storage unit 140, and an input / output unit 150. The processing unit 110 has a CPU (Central Processing Unit) that performs arithmetic processing, and a RAM (Random Access Memory) and a ROM (Read Only Memory) that function as memories for storing various information. All or part of the functions of the processing unit 110 are realized by loading an application program held in the ROM into the RAM and executing it on the CPU, thereby reading and writing data in the RAM and the ROM.

[0042] The memory unit 140 is a storage device that is electrically connected to the processing unit 110 and stores information. When the control device 100 controls the injection molding machine 1, information acquired from the injection molding machine 1 by the processing unit 110 and information calculated by the processing unit 110 are stored in the memory unit 140, and the information stored in the memory unit 140 is called up by the processing unit 110 and used to control the injection molding machine 1.

[0043] Each function realized by the processing unit 110 may be stored in advance as a program in the storage unit 140. In this case, the processing unit 110 executes each function by calling up the program stored in the storage unit 140 and executing operations according to the program in the processing unit 110. The storage unit 140 may be provided integrally with the control device 100, or may be configured to be detachable from the control device 100.

[0044] The input / output unit 150 is a so-called interface that inputs and outputs signals between the control device 100 and external devices. That is, various actuators and various sensors of the injection molding machine 1 connected to the control device 100, the input unit 160, and the display unit 170 are connected to the input / output unit 150. Examples of the actuators and various sensors connected to the input / output unit 150 include the heater 13 of the heating barrel 11 of the injection device 10, the driving motor 31 of the propulsion mechanism 30, the driving motor 43 of the rotation mechanism 40, the driving motor 51 and the encoder 52 of the forward / reverse mechanism 50, and the load cell 60. The processing unit 110 of the control device 100 transmits and receives signals between these external devices via the input / output unit 150.

[0045] The processing unit 110 functionally comprises a pressure loss calculation unit 111 , a virtual mold internal pressure calculation unit 112 , an injection pressure determination unit 113 , a virtual mold internal pressure determination unit 114 , and a movement control unit 120 .

[0046] Among these, the pressure loss calculation unit 111 is capable of calculating the pressure loss in the injection device 10 when the resin material is injected from the nozzle 12 of the heating barrel 11, based on a preset pressure loss model M and the injection speed S of the screw 20 detected by the encoder 52 of the driving motor 51 of the forward / reverse mechanism 50. The pressure loss model M is preset and stored in the storage unit 140. The pressure loss model M will be described later.

[0047] The virtual internal mold pressure calculation unit 112 is capable of calculating a virtual internal mold pressure V, which is the pressure of the resin material in the mold 75 when the molten resin material is injected from the heated barrel 11 into the cavity 75a of the mold 75. The virtual internal mold pressure calculation unit 112 calculates, as the virtual internal mold pressure V of the resin material in the mold 75, a pressure obtained by subtracting the pressure loss calculated by the pressure loss calculation unit 111 from the injection pressure P detected by the load cell 60 when the resin material is injected from the heated barrel 11 by moving the screw 20.

[0048] The injection pressure determination unit 113 is capable of determining whether the injection pressure P detected by the load cell 60 when the resin material is injected from the heating barrel 11 reaches an upper limit value set for the injection pressure P. The upper limit value set for the injection pressure P in this case is set, for example, by selecting from among those preset according to the type of molded product molded by the injection molding machine 1 and the type of resin material used to mold the molded product based on the type of molded product and the type of resin material to be actually molded, or by directly inputting the upper limit value by the operator. The set upper limit value of the injection pressure P is stored in the storage unit 140.

[0049] The virtual internal pressure determination unit 114 is capable of determining whether the virtual internal pressure V calculated by the virtual internal pressure calculation unit 112 has reached an upper limit value set for the virtual internal pressure V. The upper limit value set for the virtual internal pressure V in this case is set, for example, by selecting from among those previously set according to the type of molded product molded by the injection molding machine 1 and the type of resin material used for molding the molded product based on the type of molded product and resin material to be actually molded, or by directly inputting the upper limit value by the operator. The upper limit value of the virtual internal pressure V is set to a value lower than the virtual internal pressure V when the injection pressure P reaches the upper limit value PL. Specifically, the upper limit value of the virtual internal pressure V is set to a value approximately equal to the maximum value of the pressure of the resin material in the mold 75 when a good molded product is molded in the mold 75 with the cavity 75a filled with the resin material. The set upper limit value of the virtual internal pressure V is stored in the storage unit 140.

[0050] The movement control unit 120 is capable of controlling the movement of the screw 20 when the resin material is injected from the heating barrel 11 of the injection device 10. The movement control unit 120 controls the drive motor 51 of the forward / reverse mechanism 50 to operate the forward / reverse mechanism 50 and control the movement of the screw 20.

[0051] Furthermore, when controlling the movement of the screw 20, the movement control unit 120 performs the movement control by including the virtual internal mold pressure V calculated by the virtual internal mold pressure calculation unit 112 in the judgment factors during control. In other words, when controlling the movement of the screw 20, the movement control unit 120 performs the movement control based on the virtual internal mold pressure V calculated by the virtual internal mold pressure calculation unit 112.

[0052] Specifically, when controlling the movement of the screw 20 when injecting a resin material from the heating barrel 11 of the injection device 10, the movement control unit 120 basically controls the movement based on the injection speed S set for the position in the movement direction of the screw 20. Furthermore, when the injection pressure determination unit 113 determines that the injection pressure P has reached the upper limit set for the injection pressure P, or when the virtual internal pressure determination unit 114 determines that the virtual internal pressure V has reached the upper limit set for the virtual internal pressure V, the movement control unit 120 controls the movement of the screw 20 based on the injection pressure P detected by the load cell 60 or the virtual internal pressure V calculated by the virtual internal pressure calculation unit 112.

[0053] FIG. 6 is an explanatory diagram showing an example of the pressure loss model M. The pressure loss model M used when calculating the pressure loss in the pressure loss calculation unit 111 is a model showing the pressure loss for each injection speed S of the screw 20 when the screw 20 is moved in the heating barrel 11 to inject the molten resin material from the nozzle 12. The pressure loss in this case is the pressure lost in the heating barrel 11 when the molten resin material is injected from the heating barrel 11. Specifically, the pressure loss in this case is the pressure lost due to the resistance when the resin material passes through the nozzle 12 and the sliding resistance of the screw 20 against the heating barrel 11 when the screw 20 is moved in the heating barrel 11 to inject the resin material from the heating barrel 11.

[0054] The pressure loss model M is set in advance as a model that associates the injection speed S of the screw 20 when the resin material is injected from the heated barrel 11 with the pressure lost in the heated barrel 11. The pressure loss model M is set for each type of resin material, for example, as shown in FIG. 6. The pressure loss model M shown in FIG. 6 shows pressure loss models M for three types of resin materials, resin A, resin B, and resin C. The pressure loss model M may be set by actually measuring the pressure loss when the resin material is injected from the heated barrel 11 for each injection speed S of the screw 20 in advance, or may be set by calculating the pressure loss through flow analysis of the resin material.

[0055] When actually measuring the pressure loss when the resin material is injected from the heated barrel 11, the nozzle 12 of the heated barrel 11 is separated from the mold 75, and the value detected by the load cell 60 when the molten resin material is injected outside the mold 75 is used as the pressure lost in the heated barrel 11. In other words, when the resin material is injected with the nozzle 12 separated from the mold 75, the pressure of the resin material inside the mold 75 does not act on the screw 20 that pushes out the resin material, and only the pressure based on the resistance when the resin material is injected from the heated barrel 11 acts on it.

[0056] Therefore, when the resin material is injected from the heated barrel 11 to the outside of the mold 75 with the nozzle 12 separated from the mold 75, the value detected by the load cell 60 can be used as the pressure lost in the heated barrel 11 during the injection of the resin material. When setting the pressure loss model M based on the actual measurement of the pressure loss when the resin material is injected from the heated barrel 11, the value of the load cell 60 is measured for each injection speed S of the screw 20, and the model is set by making the injection speed S of the screw 20 correspond to the value of the load cell 60. The pressure loss model M is set in advance as described above and stored in the storage unit 140.

[0057] In addition, the movement control unit 120, which controls the movement of the screw 20 when injecting the resin material, has a position control controller 121, a speed control controller 122, a current control controller 123, a pressure control controller 124, and a virtual mold internal pressure controller 125.

[0058] 7 is an explanatory diagram showing the relationship between each controller of the movement control unit 120 and the injection device 10. The position controller 121 controls the position of the screw 20 in the movement direction when the resin material is injected from the nozzle 12 of the heating barrel 11, based on the position of the screw 20 in the movement direction detected by the encoder 52 of the driving motor 51 of the forward / reverse mechanism 50. That is, the position controller 121 controls the position of the screw 20 while receiving feedback on the position of the screw 20 in the movement direction from the encoder 52 of the driving motor 51. The position controller 121 transmits a speed command corresponding to the position of the screw 20 in the movement direction detected by the encoder 52 to the speed controller 122.

[0059] The speed command transmitted from the position controller 121 to the speed controller 122 is based on the speed command stored in the storage unit 140. For example, the speed command input by an operator via the input unit 160 is stored in the storage unit 140. The speed command stored in the storage unit 140 is the upper limit value of the injection speed S of the screw 20, and the position controller 121 transmits a speed command corresponding to the position in the movement direction of the screw 20 to the speed controller 122 so that the final injection speed S of the screw 20 becomes the upper limit value.

[0060] The speed controller 122 controls the injection speed S of the screw 20 when injecting the resin material from the nozzle 12 of the heating barrel 11, based on the speed command transmitted from the position controller 121 and the injection speed S of the screw 20 detected by the encoder 52 of the driving motor 51 of the forward and backward movement mechanism 50. That is, the speed controller 122 controls the injection speed S of the screw 20 while receiving feedback on the injection speed S of the screw 20 from the encoder 52 of the driving motor 51. The speed controller 122 transmits to the current controller 123 a current value for driving the driving motor 51 of the forward and backward movement mechanism 50, which can move the screw 20 at the injection speed S corresponding to the position in the movement direction of the screw 20.

[0061] The current controller 123 controls the drive of the driving motor 51 of the forward / reverse mechanism 50 based on the current value transmitted from the speed controller 122. The current controller 123 controls the drive of the driving motor 51 of the forward / reverse mechanism 50 while feeding back the current value output from the current controller 123 and comparing it with the current value transmitted from the speed controller 122. The drive control of the driving motor 51 by the current controller 123 is performed via an amplifier 180 that amplifies the power supplied to the driving motor 51.

[0062] When the injection pressure determination unit 113 determines that the injection pressure P has reached the upper limit, the pressure controller 124 controls the movement of the screw 20 based on the injection speed S set as the injection speed S when the injection pressure P has reached the upper limit. The upper limit set for the injection pressure P and the injection speed S set as the injection speed S when the injection pressure P has reached the upper limit are set in advance as pressure commands and stored in the storage unit 140. As the pressure command, for example, a value inputted from the input unit 160 by the operator is stored in the storage unit 140.

[0063] The injection speed S, which is set as the injection speed S when the injection pressure P reaches the upper limit, is set to a speed slower than the injection speed S, which is set as the injection speed S when the injection pressure P does not reach the upper limit. The pressure controller 124 compares the injection pressure P with the upper limit in the injection pressure determination unit 113 while receiving feedback on the injection pressure P from the load cell 60, and controls the movement of the screw 20 in the pressure controller 124 when it is determined that the injection pressure P has reached the upper limit.

[0064] When the virtual internal pressure judgment unit 114 judges that the virtual internal pressure V has reached its upper limit, the virtual internal pressure controller 125 controls the movement of the screw 20 based on the injection speed S which is set as the injection speed S when the virtual internal pressure V has reached its upper limit. The upper limit set for the virtual internal pressure V and the injection speed S which is set as the injection speed S when the virtual internal pressure V has reached its upper limit are set in advance as a virtual internal pressure command and stored in the storage unit 140. As the virtual internal pressure command, for example, a value inputted from the input unit 160 by the operator is stored in the storage unit 140.

[0065] The injection speed S set as the injection speed S when the virtual internal pressure V reaches the upper limit is set to a speed slower than the injection speed S set as the injection speed S when the virtual internal pressure V does not reach the upper limit. The virtual internal pressure controller 125 compares the virtual internal pressure V with the upper limit in the virtual internal pressure determination unit 114 based on feedback of the injection speed S of the screw 20 from the encoder 52 of the driving motor 51 and the pressure loss model M, and when it is determined that the virtual internal pressure V has reached the upper limit, the virtual internal pressure controller 125 controls the movement of the screw 20.

[0066] <Action of injection molding machine 1> The injection molding machine 1 according to this embodiment includes the above-mentioned configuration, and its operation will be described below. The injection molding machine 1 repeats a cycle of injection and molding operations, with one injection and molding operation being one cycle. Each cycle includes a plurality of processes for injecting molding material and molding a product. Each cycle includes, for example, a mold closing process, a filling process, a pressure holding process, a mold opening process, and a removal process.

[0067] The mold closing process is a process in which the movable platen 72 of the mold clamping device 70 is moved in a direction approaching the fixed platen 71, thereby combining the movable mold 77 and the fixed mold 76 and forming a cavity 75a corresponding to the product shape between the movable mold 77 and the fixed mold 76.

[0068] The filling process is a process in which molten resin, which is a resin material melted by the heated barrel 11 of the injection device 10, is injected into a cavity 75a formed by a movable mold 77 and a fixed mold 76 attached to the mold clamping device 70.

[0069] The pressure dwell process is a process of waiting while maintaining the pressure of the molding resin, which is the resin material injected into the cavity 75a formed by the movable mold 77 and the fixed mold 76 attached to the mold clamping device 70, for a certain period of time until the temperature of the molding resin drops and solidifies to form a molded product. Also, in the pressure dwell process, the resin material to be injected in the next cycle is sent to the end side where the nozzle 12 of the heating barrel 11 of the injection device 10 is located, and the resin material to be used in the next cycle is prepared. The resin material is also measured during the pressure dwell process.

[0070] The mold opening process is a process in which the movable platen 72 is moved away from the fixed platen 71 and the movable mold 77 is moved away from the fixed mold 76 in order to remove the molded product formed by the fixed mold 76 and the movable mold 77 attached to the mold clamping device 70.

[0071] The removal process is a process in which, after the movable die 77 is separated from the fixed die 76, the molded product attached to the movable die 77 is pushed out by the push-out member 86 of the push-out mechanism 85, thereby removing the molded product from the die 75.

[0072] When molding a molded product with the injection molding machine 1, these injection and molding operation cycles are repeatedly executed to continuously mold the molded products. Here, when injecting molten resin material into the mold 75 in the filling process, it is necessary to appropriately control the pressure of the resin material in the mold 75. Next, pressure control when injecting the resin material into the mold 75 in the filling process will be described.

[0073] 8 is an explanatory diagram showing the changes in injection speed S, injection pressure P, and virtual mold internal pressure V during molding of a non-defective product. When injecting a resin material from the heated barrel 11 of the injection device 10 into the mold 75 in the filling step, the movement control section 120 of the control device 100 detects the position of the screw 20 that moves during injection using a position controller 121, based on the detection result of the encoder 52 of the driving motor 51 of the forward / reverse mechanism 50, and controls the speed of the screw 20 using a speed controller 122 in accordance with the position of the screw 20.

[0074] When the speed controller 122 controls the speed of the screw 20, the injection speed S of the screw 20 is controlled according to the set value of the injection speed S when the speed control is performed based on the moving position of the screw 20. The set value of the injection speed S is set, for example, by an operator directly inputting the set value of the injection speed S. The set value of the injection speed S may be set by selecting based on the type of molded product and the type of resin material to be actually molded from among those preset according to the type of molded product to be molded by the injection molding machine 1 and the type of resin material to be used for molding the molded product, etc.

[0075] The set value of the injection speed S is stored in the storage unit 140 of the control device 100. When controlling the speed of the screw 20, the set value of the injection speed S stored in the storage unit 140 is used as a target value, and a speed command according to the position of the screw 20 is transmitted to the speed controller 122 by the position controller 121, and the speed controller 122 performs speed control. The speed controller 122 controls the speed of the screw 20 based on the speed command transmitted from the position controller 121 while receiving feedback of the injection speed S from the encoder 52 of the driving motor 51 of the forward / reverse mechanism 50.

[0076] For these reasons, the position controller 121 and the speed controller 122 control the speed so that the injection speed S of the screw 20 becomes a set value, which is a target value of the injection speed S, during the filling process, and when the injection speed S of the screw 20 reaches the set value, the injection speed S is maintained. In this case, the resin material is filled into the mold 75 over time, and the pressure of the resin material increases in the mold 75 over time. For this reason, the pressure of the resin material in the heating barrel 11 also increases, and the injection pressure P acting on the screw 20 when injecting the resin material also increases as the resin material is filled into the mold 75 and the pressure of the resin material in the mold 75 increases.

[0077] Incidentally, the cavity 75a of the mold 75 is filled with the resin material after the runner connected to the cavity 75a is filled with the resin material. Therefore, even after the screw 20 starts moving toward the side where the nozzle 12 is located, the injection pressure P does not rise immediately, but rises after the runner is filled with the resin material. In the filling process, the injection pressure determination unit 113 continuously determines whether the injection pressure P, which rises in this manner, has reached an upper limit value PL set for the injection pressure P.

[0078] Here, when controlling the movement of the screw 20 in the filling process, the pressure loss calculation unit 111 of the control device 100 calculates the pressure loss in the injection device 10 when injecting the resin material based on the injection speed S detected by the encoder 52 of the driving motor 51 of the forward / reverse mechanism 50 and the pressure loss model M stored in the storage unit 140. When the storage unit 140 stores a plurality of pressure loss models M according to the type of resin material, etc., the pressure loss model M that matches the conditions such as the type of resin material in the current injection molding is used.

[0079] After the pressure loss in the injection device 10 is calculated by the pressure loss calculation unit 111, the virtual internal mold pressure calculation unit 112 of the control device 100 calculates a pressure obtained by subtracting the pressure loss calculated by the pressure loss calculation unit 111 from the injection pressure P detected by the load cell 60, as the virtual internal mold pressure V, which is the pressure of the resin material in the mold 75. When controlling the movement of the screw 20 in the filling step, the virtual internal mold pressure V is continuously calculated in this manner by the pressure loss calculation unit 111 and the virtual internal mold pressure calculation unit 112. In the filling step, like the injection pressure P, the virtual internal mold pressure V calculated in this manner also rises as the resin material is filled into the mold 75 and the pressure of the resin material in the mold 75 rises.

[0080] In addition, since the resin material is filled into the cavity 75a of the metal mold 75 after the runner connected to the cavity 75a is filled with the resin material, the virtual internal mold pressure V also rises after the screw 20 starts to move toward the side where the nozzle 12 is located and the runner is filled with the resin material, similar to the injection pressure P. In the filling step, the virtual internal mold pressure V that rises in this way is continuously judged by the virtual internal mold pressure judgment unit 114 as to whether it has reached an upper limit value set for the virtual internal mold pressure V.

[0081] In this manner, the screw 20 is moved within the heating barrel 11 while maintaining the injection speed S of the screw 20 at a set value, and when the position of the screw 20 reaches the switching position H, which is a reference position for switching between the filling process and the pressure holding process, the injection speed S is reduced. By reducing the injection speed S in the pressure holding process, the injection pressure P acting on the screw 20 and the virtual internal mold pressure V in the mold 75 also decrease with the decrease in injection speed S.

[0082] Even after switching to the pressure holding process, the screw 20 slows down the injection speed S and moves to the side where the nozzle 12 is located to slightly feed the resin material into the cavity 75a of the mold 75. This allows the resin material to be fed into the cavity 75a, where the resin material shrinks slightly as it is cooled in the pressure holding process, even during the pressure holding process, so that sink marks in the molded product can be suppressed.

[0083] 9 is an explanatory diagram showing a state in which the injection pressure P reaches the upper limit PL in a case in which the control device 100 does not have the virtual internal pressure judgment unit 114 and does not judge whether the virtual internal pressure V has reached the upper limit. In the filling step, the resin material is filled into the cavity 75a of the mold 75 by moving the screw 20 inside the heating barrel 11 as described above, but partial clogging may occur when the resin material is filled. In this way, if partial clogging occurs when the resin material is filled, the injection pressure P is likely to rise.

[0084] For example, in the case where a plurality of cavities 75a capable of molding a molded product are formed in the mold 75, if a gate connected to some of the cavities 75a becomes clogged, the resin material cannot be filled into the clogged cavity 75a. In this case, the space in the mold 75 that can be filled with the resin material becomes smaller, so that when the resin material is fed from the heating barrel 11 to the mold 75 by moving the screw 20, the injection pressure P acting on the screw 20 tends to increase.

[0085] In the filling process, the injection pressure determination unit 113 continuously determines whether the injection pressure P has reached the upper limit PL set for the injection pressure P, so that when the injection pressure P increases and reaches the upper limit PL, the injection pressure determination unit 113 determines that the injection pressure P has reached the upper limit PL. When the injection pressure determination unit 113 determines that the injection pressure P detected by the load cell 60 has reached the upper limit PL, the movement control unit 120 of the control device 100 controls the movement of the screw 20 based on the injection speed S set as the injection speed S when the injection pressure P has reached the upper limit PL. In other words, when the injection pressure determination unit 113 determines that the injection pressure P has reached the upper limit PL set in advance and stored in the storage unit 140, the movement control unit 120 controls the movement of the screw 20 by the pressure control controller 124.

[0086] When the injection pressure determination unit 113 determines that the injection pressure P has reached the upper limit PL, the pressure controller 124 controls the movement of the screw 20 so that the injection speed S becomes 0. That is, when the injection pressure P has reached the upper limit PL, the pressure controller 124 gradually reduces the injection speed S and stops the movement of the screw 20 toward the side where the nozzle 12 is located. This stops the filling of the resin material from the heating barrel 11 into the mold 75.

[0087] However, in the filling process, after a blockage occurs in a gate connected to some of the cavities 75a, the filling of the resin material from the heating barrel 11 into the mold 75 continues until it is determined that the injection pressure P has reached the upper limit PL. Therefore, the filling of the resin material continues for the cavities 75a other than the cavities 75a connected to the clogged gate. In this state, the fact that the injection pressure P has reached the upper limit PL means that the pressure of the resin material in the cavities 75a being filled with the resin material is also rising.

[0088] For this reason, in the cavity 75a filled with the resin material, burrs may occur in the molded product molded in the cavity 75a due to the pressure of the resin material. Burrs may also occur in the runner connected to the cavity 75a. Since molded products with burrs are deemed defective, if a blockage occurs in a gate connected to some of the cavities 75a, not only the molded product molded in the clogged cavity 75a but also the molded products molded in the other cavities 75a will be disposed of as defective products.

[0089] 10 is an explanatory diagram showing a state in which the control device 100 has a virtual mold internal pressure determination unit 114 and the virtual mold internal pressure V has reached an upper limit value VL. In this embodiment, the control device 100 has a virtual mold internal pressure determination unit 114 that determines whether the virtual mold internal pressure V has reached the upper limit value VL. Therefore, even if a blockage occurs in a gate connected to some of the cavities 75a during the filling process, it is possible to suppress the occurrence of defects in molded products molded in the other cavities 75a.

[0090] In other words, if a clog occurs in a gate connected to some of the cavities 75a during the filling process, the clogged cavities 75a cannot be filled, and the resin material sent from the heated barrel 11 to the mold 75 fills the other cavities 75a. At that time, when there are cavities 75a that cannot be filled with the resin material, the space in the mold 75 that can be filled with the resin material becomes smaller, whereas the amount of resin material sent from the heated barrel 11 remains the same as in normal times, and therefore the pressure of the resin material tends to increase in the cavities 75a that are not clogged.

[0091] In this embodiment, the pressure loss in the injection device 10 is calculated by a pressure loss calculation unit 111 based on the injection speed S detected by the encoder 52 and a pressure loss model M, and the virtual mold internal pressure calculation unit 112 calculates a virtual mold internal pressure V by subtracting the pressure loss calculated by the pressure loss calculation unit 111 from the injection pressure P detected by the load cell 60.

[0092] Furthermore, the virtual internal pressure V calculated by the virtual internal pressure calculation unit 112 is determined by the virtual internal pressure determination unit 114 as to whether or not it has reached an upper limit value VL set for the virtual internal pressure V, and when the virtual internal pressure determination unit 114 determines that the virtual internal pressure V has reached the upper limit value VL, the movement control unit 120 controls the movement of the screw 20 based on the virtual internal pressure V. That is, when the virtual internal pressure determination unit 114 determines that the virtual internal pressure V calculated by the virtual internal pressure calculation unit 112 has reached the upper limit value VL, the movement control unit 120 of the control device 100 controls the movement of the screw 20 based on the injection speed S set as the injection speed S when the virtual internal pressure V has reached the upper limit value VL.

[0093] The upper limit VL of the virtual internal pressure V used for judgment in the virtual internal pressure judgment unit 114 is set to a value lower than the virtual internal pressure V when the injection pressure P reaches the upper limit PL, and is set to a value approximately equal to the maximum pressure of the resin material in the mold 75 when a non-defective product is molded with the mold 75. When the virtual internal pressure judgment unit 114 judges that the virtual internal pressure V calculated by the virtual internal pressure calculation unit 112 has reached the upper limit VL set in advance and stored in the memory unit 140, the movement control unit 120 controls the movement of the screw 20 by the virtual internal pressure controller 125.

[0094] When the virtual internal pressure determination unit 114 determines that the virtual internal pressure V has reached the upper limit VL, the virtual internal pressure controller 125 controls the movement of the screw 20 so that the injection speed S becomes 0. That is, when the virtual internal pressure V has reached the upper limit VL, the virtual internal pressure controller 125 gradually reduces the injection speed S and stops the movement of the screw 20 toward the side where the nozzle 12 is located. This stops the filling of the resin material from the heating barrel 11 to the mold 75. In this case, the virtual internal pressure V calculated by the virtual internal pressure calculation unit 112 is calculated based on the injection pressure P detected by the load cell 60, so that when the injection pressure P increases, the virtual internal pressure V also increases with the increase in the injection pressure P.

[0095] On the other hand, the upper limit VL of the virtual internal mold pressure V is set to a value lower than the virtual internal mold pressure V when the injection pressure P reaches the upper limit PL, and is set to a value approximately equal to the maximum pressure of the resin material in the mold 75 when a non-defective product is molded with the mold 75. For this reason, in a situation in which the injection pressure P increases due to clogging of the gates connected to some cavities 75a, when the filling of the resin material into the mold 75 is stopped due to the virtual internal mold pressure V reaching the upper limit VL, the pressure of the resin material in the mold 75 other than the cavities 75a where the clogging has occurred becomes approximately equal to the pressure of the resin material when a non-defective product is molded.

[0096] As a result, even if a gate connected to some of the cavities 75a is clogged, the pressure of the resin material in the other cavities 75a and runners is the same as that during molding of a good product, so that good products can be molded without generating burrs. Therefore, even if a gate connected to some of the cavities 75a is clogged, good products can be molded in the cavities 75a other than the clogged cavity 75a, so that the generation of defective products can be suppressed.

[0097] <Effects of the embodiment> The injection molding machine 1 according to the above embodiment calculates the virtual mold pressure V from the pressure loss in the injection device 10 calculated based on the pressure loss model M when injecting the resin material and the injection speed S of the screw 20 detected by the encoder 52, and the injection pressure P detected by the load cell 60, and when controlling the movement of the screw 20 when injecting the resin material, the virtual mold pressure V is included in the judgment factors during control, and the movement control is performed based on the virtual mold pressure V. Therefore, even if clogging occurs in a part of the mold 75 during the filling process, by judging the movement of the screw 20 during the filling process by including the virtual mold pressure V in the judgment factors during control, it is possible to suppress the pressure of the resin material in the mold 75 from becoming too high in parts other than the part where clogging occurs. Therefore, the pressure control of the resin material injected into the mold 75 can be appropriately performed.

[0098] In addition, since the pressure loss in the injection device 10 is calculated based on the pressure loss model M and the injection speed S of the screw 20, and the virtual mold internal pressure V is calculated from the calculated pressure loss and the injection pressure P detected by the load cell 60, the pressure of the resin material filled in the mold 75 can be properly calculated without arranging a pressure sensor in the mold 75. This makes it possible to suppress restrictions on the design of the mold 75 due to arranging a pressure sensor in the mold 75. As a result, the pressure of the resin material injected into the mold 75 can be controlled without impairing the design freedom of the mold 75.

[0099] In addition, since the virtual mold pressure V is calculated from the pressure loss corresponding to the injection speed S using the pressure loss model M, even if the molding conditions are changed, the virtual mold pressure V corresponding to the molding conditions can be calculated without recollecting data for calculating the virtual mold pressure V corresponding to the molding conditions. As a result, even if the molding conditions are changed, when clogging occurs in a part of the mold 75 during the filling process, it is possible to detect that the pressure of the resin material in the mold 75 has increased in parts other than the part where the clogging has occurred, and it is possible to prevent the pressure of the resin material from becoming too high in parts other than the part where the clogging has occurred. As a result, even if the molding conditions are changed, the pressure of the resin material injected into the mold 75 can be easily controlled.

[0100] Moreover, the movement control section 120 that controls the movement of the screw 20 controls the movement based on the injection speed S that is set for the position in the movement direction of the screw 20, and when the injection pressure P reaches the upper limit PL or when the virtual internal mold pressure V reaches the upper limit VL, controls the movement of the screw 20 based on the injection pressure P or the virtual internal mold pressure V. Therefore, in the filling process, abnormality determination is performed not only for the injection pressure P but also for the virtual internal mold pressure V, and the movement of the screw 20 is controlled, so that it is possible to more reliably prevent the pressure of the resin material filled in the mold 75 from becoming too high. As a result, the pressure control of the resin material injected into the mold 75 can be more appropriately performed.

[0101] Furthermore, when the virtual internal pressure V reaches the upper limit VL, the movement control section 120 controls the movement of the screw 20 based on the injection speed S that is set as the injection speed S when the virtual internal pressure V reaches the upper limit VL, so that when it can be determined that the pressure of the resin material filled in the mold 75 has become high based on the virtual internal pressure V, the movement control section 120 can control the movement of the screw 20 so that the pressure of the resin material does not increase any more. This makes it possible to more reliably prevent the pressure of the resin material filled in the mold 75 from becoming too high. As a result, the pressure of the resin material injected into the mold 75 can be more appropriately controlled.

[0102] In addition, since the upper limit VL of the virtual mold pressure V is set to a value lower than the virtual mold pressure V when the injection pressure P reaches the upper limit PL, when the pressure of the resin material rises due to clogging in a part of the mold 75, it is possible to prevent the pressure in the cavity 75a of the mold 75 from becoming too high. This makes it possible to prevent the pressure in the parts of the mold 75 other than the part where the clogging occurs from becoming too high, and it is possible to appropriately control the pressure in the parts other than the part where the clogging occurs. Therefore, it is possible to minimize the occurrence of defective products in the molded products molded in the parts of the mold 75 other than the part where the clogging occurs. As a result, it is possible to more appropriately control the pressure of the resin material injected into the mold 75.

[0103] Furthermore, in the injection molding machine 1 according to the embodiment, the virtual mold pressure V is calculated by the virtual mold pressure calculation unit 112, and the movement of the screw 20 is controlled by including the virtual mold pressure V as a judgment factor. Therefore, even if there is response variation in the check ring 25 (see Figure 4), it is possible to prevent the pressure of the resin material filled into the mold 75 during the filling process from becoming too high.

[0104] That is, when the resin material to be injected in the filling process is metered by moving the screw 20 rearward in the heating barrel 11 to send the resin material to the front of the screw 20, the check ring 25 is pushed by the resin material and moves forward in the groove 22 (see FIG. 4) formed in the screw 20, and abuts against the front groove wall 23. In the screw 20, a communication part 24 that communicates with the front part of the screw 20 is formed in the front groove wall 23 of the groove 22, and a gap is formed between the inner circumferential surface of the check ring 25 and the groove bottom of the groove 22. Therefore, when the check ring 25 abuts against the front groove wall 23 of the groove 22, the resin material can move from the rear part of the check ring 25 to the front part of the screw 20 through the gap between the inner circumferential surface of the check ring 25 and the groove bottom of the groove 22 and the communication part 24.

[0105] On the other hand, when the screw 20 is moved forward to inject the resin material in the heating barrel 11 in the filling process, the check ring 25 is pushed by the resin material and moves rearward in the groove 22 formed in the screw 20, coming into contact with the rear groove wall 23. In this case, the gap between the inner peripheral surface of the check ring 25 and the groove bottom of the groove 22 is blocked by the rear groove wall 23 of the groove 22 and the check ring 25, so that the resin material cannot move from the portion in front of the check ring 25 to the portion in the rear of the screw 20.

[0106] The check ring 25 can control the flow of the resin material in one direction by moving forward or backward in the groove 22 in response to moving the screw 20 backward or forward in the heating barrel 11. However, since the check ring 25 moves in the groove 22 due to resistance from the resin material when the screw 20 is moved forward or backward in the heating barrel 11, the movement of the check ring 25 is left to the state of the resin material near the check ring 25. For this reason, when the screw 20 is moved forward in the filling process, the movement of the check ring 25 in the groove 22, i.e., the response of the check ring 25, may vary.

[0107] In the injection molding machine 1 of the embodiment, even if there is variation in the response of the check ring 25 as described above, when controlling the movement of the screw 20 during the filling process, the virtual mold pressure V is also included in the judgment factors and the movement of the screw 20 is controlled, so that the pressure of the resin material filled into the mold 75 during the filling process can be prevented from becoming too high.

[0108] Fig. 11 is an explanatory diagram showing the changes in injection speed S, injection pressure P, and virtual internal mold pressure V when there is variation in the response of the check ring 25. When there is variation in the response of the check ring 25, there may be variation in the resin material sent to the front side of the screw 20 when the resin material is metered, or there may be variation in the restriction of the movement of the resin material to the rear side of the check ring 25 during the filling process, which may result in variation in the injection pressure P as shown in Fig. 11. Furthermore, when variation in the injection pressure P occurs, variation in the virtual internal mold pressure V also occurs as shown in Fig. 11 in accordance with the variation in the injection pressure P.

[0109] In such a case, if the filling process is controlled without judging whether the virtual mold internal pressure V has reached the upper limit value VL, the amount of resin material filled into the mold 75 in the filling process varies, causing flash in the molded product if the amount of resin material filled is large, or causing a short circuit in the molded product if the amount of resin material filled is small. For this reason, if there is variation in the response of the check ring 25, it is considered that defective molded products are more likely to occur.

[0110] In contrast, in the present embodiment, the virtual mold internal pressure V is calculated in the filling process and a determination is made as to whether or not the virtual mold internal pressure V has reached the upper limit value VL, thereby making it possible to suppress molding defects that occur when there is variation in the response of the check ring 25.

[0111] 12 is an explanatory diagram showing a state in which the virtual internal pressure V has reached the upper limit value VL when there is variation in the response of the check ring 25. In this embodiment, the virtual internal pressure V is obtained to determine whether or not the virtual internal pressure V has reached the upper limit value VL. Therefore, even if there is variation in the virtual internal pressure V due to variation in the response of the check ring 25, as shown in FIG. 12, it is possible to determine whether or not the virtual internal pressure V has reached the upper limit value VL regardless of the variation in the virtual internal pressure V.

[0112] As a result, when the varying virtual mold pressure V reaches the upper limit VL, the movement of the screw 20 is controlled based on the injection speed S that is set as the injection speed S when the virtual mold pressure V reaches the upper limit VL, so that an appropriate amount of resin material can be filled into the mold 75 in the filling step. Therefore, even if the injection pressure P in the filling step varies due to variations in the response of the check ring 25, the pressure of the resin material in the mold 75 can be kept constant, so that molding defects in the molded product can be suppressed.

[0113] [Variations] The molding of the molded product may be performed by so-called bubble molding, which is a molding method that suppresses the occurrence of molding defects such as burrs by lowering the upper limit PL of the injection pressure P. In bubble molding, the occurrence of molding defects such as burrs can be more reliably suppressed by the bubble molding, by determining the virtual internal mold pressure V and controlling the movement of the screw 20 based on whether the virtual internal mold pressure V has reached the upper limit VL.

[0114] FIG. 13 is an explanatory diagram showing the injection speed S, injection pressure P, and virtual mold internal pressure V when blow molding is performed without determining whether the virtual mold internal pressure V has reached the upper limit VL. In blow molding, the upper limit PL of the injection pressure P is set low, so that the injection pressure P reaches the upper limit PL at a relatively early stage in the filling process. As a result, the movement control unit 120 controls the movement of the screw 20 based on the injection speed S set as the injection speed S when the injection pressure P reaches the upper limit PL. The injection speed S set as the injection speed S when the injection pressure P reaches the upper limit PL is slower than the injection speed S when the injection pressure P has not reached the upper limit PL, so that when the injection pressure P reaches the upper limit PL, the injection speed S is reduced as shown in FIG. 13.

[0115] When the injection speed S is reduced, the amount of resin material filled into the mold 75 is reduced, so that the increase in pressure of the resin material in the mold 75 is suppressed, and molding defects such as burrs are suppressed. However, if the reduction in injection speed S is insufficient when the injection pressure P reaches the upper limit PL, the increase in pressure of the resin material in the mold 75 may not be effectively suppressed. In this case, even if blow molding is performed, the pressure of the resin material in the mold 75 may become high, and molding defects such as burrs may not be effectively suppressed.

[0116] Fig. 14 is an explanatory diagram showing the injection speed S, injection pressure P, and virtual internal pressure V when blow molding is performed while judging whether the virtual internal pressure V has reached the upper limit VL. Even when blow molding is performed, if the upper limit VL of the virtual internal pressure V is set and blow molding is performed while judging whether the virtual internal pressure V has reached the upper limit VL, the injection speed S is reduced when the virtual internal pressure V reaches the upper limit VL, as shown in Fig. 14. In other words, the injection speed S set as the injection speed S when the virtual internal pressure V has reached the upper limit VL is slower than the injection speed S when the virtual internal pressure V has not reached the upper limit VL, so that the injection speed S is reduced when the virtual internal pressure V has reached the upper limit VL.

[0117] By controlling the movement of the screw 20 based on the injection speed S, which is set as the injection speed S when the virtual internal pressure V reaches the upper limit VL, the virtual internal pressure V can be prevented from exceeding the upper limit VL, and the virtual internal pressure V can be maintained constant at the pressure of the upper limit VL. This makes it possible to maintain the pressure of the resin material in the mold 75 at a pressure that can mold a good molded product. Therefore, when performing blow molding to suppress the occurrence of molding defects, it is possible to more reliably suppress the occurrence of molding defects such as burrs in the molded product.

[0118] Moreover, by obtaining the virtual internal pressure V and controlling the movement of the screw 20 based on whether the virtual internal pressure V has reached the upper limit VL, it is possible to suppress the occurrence of molding defects such as burrs and perform appropriate molding even in so-called low-pressure molding, which is a molding method in which the clamping force of the clamping device 70 is reduced. That is, in low-pressure molding, since the clamping force of the clamping device 70 is reduced, when the resin material is filled into the mold 75, the resin material is likely to overflow from the cavity 75a and generate burrs. In contrast, when the movement of the screw 20 is controlled based on whether the virtual internal pressure V has reached the upper limit VL, the pressure of the resin material in the mold 75 can be accurately managed, so that the occurrence of burrs can be suppressed. As a result, it is possible to suppress molding defects when molding is performed with a reduced clamping force in the clamping device 70, and it is possible to perform low-pressure molding more appropriately. [Explanation of symbols]

[0119] 1...injection molding machine, 5...frame, 10...injection device, 11...heating barrel, 12...nozzle, 13...heater, 15...hopper, 20...screw, 21...flight, 22...groove portion, 23...groove wall, 24...connecting portion, 25...check ring, 30...propulsion mechanism, 31...driving motor, 40...rotation mechanism, 41...rotation mechanism main body, 43...driving motor, 44...transmission belt, 45...pulley, 46...bearing, 50...forward / reverse mechanism, 51...driving motor, 52...encoder, 53...transmission belt, 54...pulley, 56...ball screw mechanism, 57...screw portion, 58...nut portion, 60...load cell, 70...mold clamping device, 71...fixed platen, 72 ...movable platen, 75... mold, 75a... cavity, 76... fixed mold, 77... movable mold, 80... mold clamping drive mechanism, 81... toggle mechanism, 85... ejection mechanism, 86... ejection member, 100... control device, 110... processing unit, 111... pressure loss calculation unit, 112... virtual mold internal pressure calculation unit, 113... injection pressure determination unit, 114... virtual mold internal pressure determination unit, 120... movement control unit, 121... position control controller, 122... speed control controller, 123... current control controller, 124... pressure control controller, 125... virtual mold internal pressure controller, 140... memory unit, 150... input / output unit, 160... input unit, 170... display unit, 180... amplifier

Claims

1. an injection device that melts a resin material in a heating barrel having a screw disposed inside, and injects the resin material from a nozzle by moving the screw toward a side where a nozzle for injecting the molten resin material is located; a mold having a cavity into which the resin material injected from the nozzle is filled, and molding the resin material in the cavity; an injection speed detection unit that detects an injection speed, which is the moving speed of the screw when injecting the resin material; an injection pressure detection unit that detects an injection pressure that acts on the screw when the resin material is injected; a control device that controls the pressure of the resin material in the mold by controlling the movement of the screw; Equipped with The control device includes: a pressure loss calculation unit that calculates a pressure loss in the injection device when the resin material is injected, based on a pressure loss model that indicates a pressure loss for each injection speed when the resin material is injected and the injection speed detected by the injection speed detection unit; a virtual mold internal pressure calculation unit that calculates a pressure obtained by subtracting the pressure loss calculated by the pressure loss calculation unit from the injection pressure detected by the injection pressure detection unit, as a virtual mold internal pressure that is the pressure of the resin material in the mold; and a movement control unit that controls the movement of the screw when injecting the resin material and controls the movement based on the virtual mold internal pressure calculated by the virtual mold internal pressure calculation unit; An injection molding machine comprising:

2. The control device includes: an injection pressure determination unit that determines whether the injection pressure detected by the injection pressure detection unit has reached an upper limit value set for the injection pressure; a virtual internal pressure determination unit that determines whether the virtual internal pressure calculated by the virtual internal pressure calculation unit has reached an upper limit value set for the virtual internal pressure; having The movement control unit is The movement control of the screw is performed based on the injection speed that is set with respect to a position in the movement direction of the screw; 2. The injection molding machine according to claim 1, wherein when the injection pressure determination unit determines that the injection pressure has reached the upper limit value, or when the virtual mold internal pressure determination unit determines that the virtual mold internal pressure has reached the upper limit value, the movement control of the screw is performed based on the injection pressure or the virtual mold internal pressure.

3. The movement control unit is When the injection pressure determination unit determines that the injection pressure has reached the upper limit value, the movement control of the screw is performed based on the injection speed that is set as the injection speed when the injection pressure has reached the upper limit value; 3. The injection molding machine according to claim 2, wherein, when the virtual mold internal pressure determination unit determines that the virtual mold internal pressure has reached the upper limit value, the movement control of the screw is performed based on the injection speed that is set as the injection speed when the virtual mold internal pressure has reached the upper limit value.

4. 4. The injection molding machine according to claim 2, wherein the upper limit of the virtual internal mold pressure is set to a value lower than the virtual internal mold pressure when the injection pressure reaches the upper limit.

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