Injection molding machine

Abstract

An injection molding machine 1 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 the 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 part 120 for controlling the movement of the screw 20 when injecting the resin material, and for controlling the movement on the basis of the virtual mold internal pressure V obtained by the virtual mold internal pressure calculation unit 112, so that the pressure of the resin material injected into the mold 75 can be controlled without impairing the degree of freedom in design of the mold 75.

Description

injection molding machine

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

[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 proper molding. For this reason, conventional injection molding machines perform molding while obtaining the pressure value of the molten resin using various methods. For example, an injection pressure testing device for an injection molding machine described in Patent Document 1 calculates the resin pressure in the injection nozzle based on the resin pressure detected during purging and the resin pressure detected during normal molding, thereby accurately detecting the resin pressure in the cavity without being affected by pressure loss in the heating cylinder.

[0003] In addition, the molding condition creation method described in Patent Document 2 obtains molding conditions for mass production molding by obtaining 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, thereby compensating for time delays and pressure losses due to the mechanical elements of the injection molding machine.In addition, Patent Document 3 describes a resin evaluation method using an injection molding machine, which detects the injection pressure at a set screw position by injecting while changing the resin temperature and injection speed, and then determines an interdependence function of pressure, speed, and temperature by the least squares method using data on N combinations of injection pressure, injection speed, and resin temperature.

[0004] Furthermore, a pressure control device for an injection molding machine described in Patent Document 4 includes an injection pressure control step for controlling the injection pressure during a pressure holding step, and an internal mold pressure control step for controlling the estimated internal mold pressure so that it becomes a set internal mold pressure after the injection pressure control step is executed, thereby suppressing variations in the pressure inside the mold between molding cycles and enabling the molding of molded products of stable quality. Furthermore, by controlling the estimated internal mold pressure during the pressure holding step so that it becomes a set internal mold pressure, the pressure inside the mold can be controlled with high responsiveness, preventing stress deformation of the molded product.

[0005] Japanese Patent Laid-Open No. 11-115023 Japanese Patent Laid-Open No. 2000-355033 Japanese Patent Laid-Open No. 2002-331558 Japanese Patent Laid-Open No. 2016-159589

[0006] In injection molding using an injection molding machine, the type of resin material or the mold may be changed depending on the desired molded product. However, 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. 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 placing a pressure sensor in the mold to detect the pressure of the resin material injected into the mold. However, placing a pressure sensor in the mold reduces the design freedom of the mold, which can limit the shape of the molded product or the layout of the cavity in the mold for molding the molded product.

[0007] On the other hand, when injection molding is performed without a pressure sensor in the mold, it becomes difficult to accurately detect and control the pressure of the resin material injected into the mold. In this case, for example, if a gate in the mold becomes clogged, it becomes difficult to detect the increase in pressure of the resin material inside the mold caused by the clogged gate, which can lead to the formation of flash due to the increased pressure of the resin material. For these reasons, it has been difficult to control the pressure of the resin material injected into the mold without compromising the design flexibility 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.

[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 having a screw disposed inside, and injects the resin material from a nozzle by moving the screw toward a side where a nozzle is located that injects the molten resin material; a mold that has a cavity into which the resin material injected from the nozzle is filled and molds 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 injecting the resin material; an injection pressure detection unit that detects an injection pressure that is the pressure acting on the screw when injecting the resin material; and an injection device that controls the movement of the screw to inject the resin material into the mold. 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 the resin material is injected 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 that 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.

[0010] The injection molding machine according to the present invention has the advantage of being able to control the pressure of the resin material injected into the mold without impairing the degree of freedom in designing the mold.

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

[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. Furthermore, 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] 1 is a schematic diagram showing an example of the configuration 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 normal use will be referred to as the up-down direction Z of the injection molding machine 1, the upper side of the injection molding machine 1 in normal use will be referred to as the upper side of the injection molding machine 1, and the lower side of the injection molding machine 1 in normal use will be referred to as the lower side of the injection molding machine 1. In the following description, the longitudinal direction Y of the injection molding machine 1 will also be referred to as the longitudinal direction Y of each component that includes 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 will be referred to 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 mold clamping unit 70, and the injection unit 10 and the mold clamping unit 70 are mounted on a frame 5 that is located 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 then cools and solidifies the plasticized material injected from the injection unit 10 using the mold 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 rotation mechanism 40, a forward / backward movement 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 introducing raw material. The screw 20 is disposed inside the heating barrel 11 and is movable axially within the heating barrel 11.

[0016] The rotation mechanism 40 rotates the screw 20 inside the heating barrel 11 , thereby making it possible to introduce the resin material from the hopper 15 into the heating barrel 11 .

[0017] The forward / backward movement mechanism 50 is capable of moving the screw 20 in the longitudinal direction Y within the heating barrel 11. Furthermore, the forward / 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 movable relative to the fixed platen 71.

[0019] The mold 75 has a cavity 75a that is filled with the resin material injected from the nozzle 12 of the heated barrel 11 of the injection device 10, and the resin material can be molded in the cavity 75a. The mold 75 that molds 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 is provided with a so-called toggle mechanism 81, which is capable of moving the movable platen 72 relative to the fixed platen 71.

[0021] The ejection mechanism 85 includes an ejection member 86 that pushes out the molded product that has adhered 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 where 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 where 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 drive motor 31, and the drive force generated by the drive 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 its tip, i.e., the front end of the heating barrel 11, so as to be in close contact with the mold 75. Specifically, the heating barrel 11 is formed in a substantially cylindrical shape, is disposed with its axis 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 therein. In other words, the heater 13 can increase the temperature of the heating barrel 11, and the resin material therein can be heated and melted to become a 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 aligned with the axial direction of the heating barrel 11; that is, the screw 20 has a helical groove on its outer circumferential surface. The screw 20, which is formed in this manner to have a helical shape, is rotatable about its axial center within the heating barrel 11. The screw 20 is also movable in the direction of its rotation axis within the heating barrel 11. In other words, the screw 20 is disposed inside the heating barrel 11 such that the central axis of the cylinder that forms the heating barrel 11 and the rotation axis of the screw 20 substantially coincide with each other, and is disposed so as to be movable in the axial direction of the heating barrel 11. The screw 20, which is rotatably disposed inside 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 therein.

[0026] A hopper 15 is disposed near the rear end of the heating barrel 11. The hopper 15 is connected to the interior of the heating barrel 11 and is capable of supplying pellets (not shown) that 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 includes a rotation mechanism main body 41, a driving motor 43, a transmission belt 44, and a pulley 45.

[0028] The drive motor 43 is disposed, for example, above the rotation mechanism main body 41. The pulley 45 is disposed in front of the rotation mechanism main body 41 and is rotatable relative to the rotation mechanism main body 41 via a bearing 46. The pulley 45 is connected to the drive shaft of the drive motor 43 via a transmission belt 44, allowing the pulley 45 to rotate by the driving force of the drive motor 43 transmitted via the transmission belt 44. In this way, the pulley 45, which can rotate by the driving force transmitted from the drive motor 43, is fixed coaxially and integrally to the screw 20. In other words, the rear end 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 rotate integrally with the pulley 45 by the driving force transmitted from the drive 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 inside the heating barrel 11 in the axial direction of the screw 20. In other words, the forward / backward movement mechanism 50 is capable of moving the screw 20 forward and backward in the longitudinal direction Y. More specifically, the forward / backward movement mechanism 50 has a drive motor 51, a transmission belt 53, a pulley 54, and a ball screw mechanism 56.

[0030] The drive motor 51 has an encoder 52 that detects the rotational position and rotational speed of the drive motor 51, and the drive shaft of the drive motor 51 is connected to a pulley 54 via a transmission belt 53. The encoder 52 of the drive motor 51 can detect 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, via the rotational position of the drive motor 51. The encoder 52 of the drive motor 51 can also detect the injection speed S, which is the movement 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 drive motor 51. The encoder 52 of the drive motor 51 is thus also used as an injection speed detection unit that detects the injection speed S of the screw 20.

[0031] The pulley 54 is integrally connected to a threaded portion 57 of the ball screw mechanism 56. The threaded 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 threaded portion 57 of the ball screw mechanism 56 is threadedly engaged with the nut portion 58.

[0032] A load cell 60 is disposed in the longitudinal direction Y between the nut portion 58 of the ball screw mechanism 56 of the forward / reverse movement mechanism 50 and the rotation mechanism main body 41 of the rotation mechanism 40. 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 / reverse 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 element and a strain sensor (both not shown) attached to the strain element. In this embodiment, the load cell 60 is disposed with its axial direction oriented in the longitudinal direction Y, and is formed in a generally cylindrical shape that is flattened in the longitudinal direction Y, with the inner diameter of the cylinder being larger than the outer diameter of the threaded portion 57 of the ball screw mechanism 56 of the forward / reverse movement mechanism 50. The load cell 60 thus formed has its front surface in the longitudinal direction Y integrally fixed to the rotation mechanism main body 41 of the rotation mechanism 40, and its rear surface in the longitudinal direction Y integrally fixed to the nut portion 58 of the ball screw mechanism 56 of the forward / reverse movement mechanism 50.

[0034] The load cell 60, which is 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 unit 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, which is 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 so as to open to the front side in the longitudinal direction Y. The screw 20 disposed within the heating barrel 11 has flights 21 that protrude outward in the radial direction of the screw 20 and are formed in a spiral shape centered on the axis of the screw 20. As a result, the screw 20 has spiral groove-shaped portions between adjacent orbital portions of the spirally formed flights 21.

[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 circumference of the screw 20 in the circumferential direction.

[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 22 of the screw 20 with its axis substantially aligned with the axis of the screw 20. The substantially cylindrical check ring 25 has an outer diameter that is approximately the same as but 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 22 of the screw 20, forming a gap between the inner circumferential surface of the check ring 25 and the groove bottom of the groove 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 22 of the screw 20. This allows the check ring 25 to move in the groove width direction within the groove 22.

[0038] The screw 20 is also formed with a communication portion 24 that connects the portion of the screw 20 that is forward of the groove portion 22 in the longitudinal direction Y with the inside of the groove portion 22. The communication portion 24 opens to the 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 as separate units, or may be formed integrally by being configured as a so-called touch panel display.

[0040] The control device 100 is connected to various actuators such as motors that serve as power sources for the operation of the injection molding machine 1, and various sensors that acquire information during 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 operation of the injection molding machine 1 using the sensors. The control device 100 can control 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] 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 stored in the ROM into the RAM and executing it on the CPU, thereby reading and writing data from and to the RAM and 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 in accordance with 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 to and from devices external to the control device 100. That is, the various actuators and sensors of the injection molding machine 1, the input unit 160, and the display unit 170, which are connected to the control device 100, are connected to the input / output unit 150. Examples of the actuators and sensors connected to the input / output unit 150 include the heater 13 of the heating barrel 11 of the injection device 10, the drive motor 31 of the propulsion mechanism 30, the drive motor 43 of the rotation mechanism 40, the drive motor 51 and 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 to and from these external devices via the input / output unit 150.

[0045] The processing unit 110 functionally includes 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] Of 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 drive motor 51 of the forward / reverse mechanism 50. The pressure loss model M is set in advance 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 inside the mold 75 when the molten resin material is injected from the heating barrel 11 into the cavity 75a of the mold 75. The virtual internal mold pressure calculation unit 112 calculates the virtual internal mold pressure V of the resin material inside the mold 75 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 heating 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 has reached an upper limit value set for the injection pressure P. In this case, the upper limit value set for the injection pressure P is set, for example, by selecting from among pre-set values ​​according to the type of molded product to be 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 resin material to be actually molded, or by the operator directly inputting the upper limit value. The set upper limit value of the injection pressure P is stored in the memory unit 140.

[0049] The virtual mold pressure determination unit 114 is capable of determining whether the virtual mold pressure V calculated by the virtual mold pressure calculation unit 112 has reached an upper limit set for the virtual mold pressure V. In this case, the upper limit set for the virtual mold pressure V is set, for example, by selecting from preset values ​​corresponding to the type of molded product to be 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 resin material to be actually molded, or by directly inputting the upper limit value by the operator. The upper limit 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. Specifically, the upper limit of the virtual mold pressure V is set to a value approximately equal to the maximum pressure of the resin material in the mold 75 when a good molded product is molded using the mold 75 whose cavity 75a is filled with resin material. The set upper limit of the virtual mold pressure V is stored in the memory 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 / backward movement mechanism 50, thereby operating the forward / backward movement mechanism 50 and controlling the movement of the screw 20.

[0051] Furthermore, when controlling the movement of the screw 20, the movement control unit 120 controls the movement by including the virtual mold internal pressure V calculated by the virtual mold internal pressure calculation unit 112 as a determination factor during control. In other words, when controlling the movement of the screw 20, the movement control unit 120 controls the movement based on the virtual mold internal pressure V calculated by the virtual mold internal pressure calculation unit 112.

[0052] Specifically, when controlling the movement of the screw 20 when injecting a resin material from the heated barrel 11 of the injection device 10, the movement control unit 120 basically controls the movement based on the injection speed S that is 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 value set for the injection pressure P, or when the virtual internal mold pressure determination unit 114 determines that the virtual internal mold pressure V has reached the upper limit value set for the virtual internal mold 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 mold pressure V calculated by the virtual internal mold pressure calculation unit 112.

[0053] 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 that shows the pressure loss for each injection speed S of the screw 20 when the screw 20 is moved within the heating barrel 11 and the molten resin material is injected 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 of the resin material when it passes through the nozzle 12 and the sliding resistance of the screw 20 relative to the heating barrel 11 when the screw 20 is moved within the heating barrel 11 and the resin material is injected 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 in advance the pressure loss when the resin material is injected from the heated barrel 11 for each injection speed S of the screw 20, or may be set by calculating the pressure loss through a 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 loss 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 extrudes 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 injection of the resin material. When setting the pressure loss model M based on actual measurements 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 correlating the injection speed S of the screw 20 with 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 drive motor 51 of the forward / backward movement mechanism 50. That is, the position controller 121 controls the position of the screw 20 while receiving feedback about the position of the screw 20 in the movement direction from the encoder 52 of the drive 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 sent from the position controller 121 and the injection speed S of the screw 20 detected by the encoder 52 of the drive motor 51 of the forward / 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 drive motor 51. The speed controller 122 sends to the current controller 123 a current value for driving the drive motor 51 of the forward / 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 drive 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 drive motor 51 of the forward / reverse mechanism 50 by 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 drive motor 51 by the current controller 123 is performed via an amplifier 180 that amplifies the power supplied to the drive motor 51.

[0062] When the injection pressure determination unit 113 determines that the injection pressure P has reached its upper limit, the pressure controller 124 controls the movement of the screw 20 based on the injection speed S that is set as the injection speed S when the injection pressure P has reached its upper limit. The upper limit that is set for the injection pressure P and the injection speed S that is set as the injection speed S when the injection pressure P has reached its upper limit are set in advance as pressure commands and stored in the storage unit 140. As the pressure command, for example, a value input by the operator from the input unit 160 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 receives feedback on the injection pressure P from the load cell 60 and compares the injection pressure P with the upper limit in the injection pressure determination unit 113, and when it is determined that the injection pressure P has reached the upper limit, the pressure controller 124 controls the movement of the screw 20.

[0064] When the virtual mold internal pressure determination unit 114 determines that the virtual mold internal pressure V has reached its upper limit, the virtual mold 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 mold internal pressure V has reached its upper limit. The upper limit set for the virtual mold internal pressure V and the injection speed S, which is set as the injection speed S when the virtual mold internal pressure V has reached its upper limit, are set in advance as a virtual mold internal pressure command and stored in the storage unit 140. As the virtual mold internal pressure command, for example, a value input by the operator from the input unit 160 is stored in the storage unit 140.

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

[0066] <Operation of Injection Molding Machine 1> The injection molding machine 1 according to this embodiment includes the configuration described above, and its operation will be described below. The injection molding machine 1 repeatedly executes a cycle of injection and molding operations, with one injection and molding operation being one cycle. Each cycle includes multiple steps for injecting molding material and molding a product. Each cycle includes, for example, a mold closing step, a filling step, a pressure holding step, a mold opening step, and an ejection step.

[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 dwelling process is a process in which the pressure of the molding resin, which is the resin material injected into the cavity 75a formed by the movable mold 77 and fixed mold 76 attached to the mold clamping device 70, is maintained, and the process waits for a certain period of time until the temperature of the molding resin drops and solidifies, turning the molding resin into a molded product. Also, in the pressure dwelling process, the resin material to be injected in the next cycle is sent to the end side of the heating barrel 11 of the injection device 10 where the nozzle 12 is located, and the resin material to be used in the next cycle is prepared; the resin material is also measured during the pressure dwelling 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 mold 77 is separated from the fixed mold 76, the molded product attached to the movable mold 77 is pushed out by the extrusion member 86 of the extrusion mechanism 85, thereby removing the molded product from the mold 75.

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

[0073] 8 is an explanatory diagram showing changes in injection speed S, injection pressure P, and virtual mold internal pressure V during molding of a non-defective product. When the resin material is injected into the mold 75 from the heated barrel 11 of the injection device 10 in the filling process, the movement control section 120 of the control device 100 uses a position control controller 121 to detect the position of the screw 20 that moves during injection, as detected by the encoder 52 of the drive motor 51 of the forward / backward movement mechanism 50, and uses a speed control controller 122 to control the speed of the screw 20 in accordance with the position of the screw 20.

[0074] When the speed of the screw 20 is controlled by the speed controller 122, the injection speed S of the screw 20 is controlled in accordance with the set value of the injection speed S when the speed control is performed based on the movement 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 from preset values ​​according to the type of molded product to be molded by the injection molding machine 1, the type of resin material used to mold the molded product, etc., based on the type of molded product and resin material to be actually molded, 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 sent by the position controller 121 to the speed controller 122, and speed control is performed by the speed controller 122. The speed controller 122 controls the speed of the screw 20 based on the speed command sent from the position controller 121, while receiving feedback of the injection speed S from the encoder 52 of the drive motor 51 of the forward / reverse mechanism 50.

[0076] For these reasons, the position controller 121 and the speed controller 122 control the injection speed S of the screw 20 during the filling process so that the injection speed S of the screw 20 becomes a set value, which is a target value of the injection speed S, and once 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 over time within the mold 75. Therefore, the pressure of the resin material within the heated 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 within the mold 75 increases.

[0077] Note that the resin material is filled into the cavity 75a of the mold 75 after the runner connected to the cavity 75a is filled with the resin material. Therefore, even after the screw 20 starts to move toward the side where the nozzle 12 is located, the injection pressure P does not increase immediately, but increases after the runner is filled with the resin material. During the filling process, the injection pressure determination unit 113 continuously determines whether the increasing injection pressure P has reached an upper limit value PL set for the injection pressure P.

[0078] 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 drive motor 51 of the forward / reverse mechanism 50 and the pressure loss model M stored in the storage unit 140. If 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 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, and obtains the virtual 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 process, the virtual mold pressure V is continuously calculated in this manner by the pressure loss calculation unit 111 and the virtual mold pressure calculation unit 112. In the filling process, like the injection pressure P, the virtual mold pressure V calculated in this manner also increases as the resin material is filled into the mold 75 and the pressure of the resin material in the mold 75 increases.

[0080] Note that, since the resin material is filled into the cavity 75a of the mold 75 after the resin material has been filled into the runner connected to the cavity 75a, 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 resin material has been filled into the runner, similar to the injection pressure P. During the filling process, the virtual internal mold pressure V, which rises in this way, is continuously judged by the virtual internal mold pressure judging unit 114 as to whether it has reached an upper limit value set for the virtual internal mold pressure V.

[0081] In this way, 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 the 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 mold pressure V in the mold 75 also decrease as the injection speed S decreases.

[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 is cooled and shrinks slightly during the pressure holding process, even during the pressure holding process, thereby suppressing sink marks on the molded product.

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

[0084] For example, if the mold 75 has multiple cavities 75a capable of molding a molded product, and a clog occurs in a gate connected to one of the cavities 75a, the resin material will no longer be able to fill the clogged cavity 75a. In this case, the space in the mold 75 that can be filled with the resin material will become smaller, and therefore, when the screw 20 is moved to feed the resin material from the heated barrel 11 into the mold 75, the injection pressure P acting on the screw 20 will likely increase.

[0085] In the filling process, the injection pressure determination unit 113 continuously determines whether the injection pressure P has reached an upper limit PL set for the injection pressure P, and when the injection pressure P increases to reach 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 memory unit 140, the movement control unit 120 controls the movement of the screw 20 using 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 heated barrel 11 into the mold 75.

[0087] However, in the filling process, after a clog occurs in a gate connected to one 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 into 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 increasing.

[0088] Therefore, in the cavity 75a filled with the resin material, burrs may occur in the molded product molded in that cavity 75a due to the pressure of the resin material. Burrs may also occur in the runners connected to the cavity 75a. Molded products with burrs are deemed defective, so if a blockage occurs in the gate connected to one 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 the upper limit value VL. In this embodiment, the control device 100 has the 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 prevent defects from occurring in the 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 will instead fill the other cavities 75a. In this case, when there are cavities 75a that cannot be filled with resin material, the space in the mold 75 that can be filled with resin material becomes smaller, but the amount of resin material sent from the heated barrel 11 remains the same as usual, so the pressure of the resin material is likely to increase in 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 the pressure loss model M, and the virtual mold internal pressure calculation unit 112 calculates the 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, a virtual mold pressure determination unit 114 determines whether the virtual mold pressure V calculated by the virtual mold pressure calculation unit 112 has reached an upper limit value VL set for the virtual mold pressure V, and if the virtual mold pressure determination unit 114 determines that the virtual mold pressure V has reached the upper limit value VL, a movement control unit 120 controls the movement of the screw 20 based on the virtual mold pressure V. That is, if the virtual mold pressure determination unit 114 determines that the virtual mold pressure V calculated by the virtual mold 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, which is set as the injection speed S when the virtual mold pressure V has reached the upper limit value VL.

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

[0094] When the virtual internal mold pressure determination unit 114 determines that the virtual internal mold pressure V has reached the upper limit VL, the virtual internal mold pressure controller 125 controls the movement of the screw 20 so that the injection speed S becomes 0. That is, when the virtual internal mold pressure V has reached the upper limit VL, the virtual internal mold 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 into the mold 75. In this case, the virtual internal mold pressure V calculated by the virtual internal mold pressure calculation unit 112 is calculated based on the injection pressure P detected by the load cell 60, and therefore, when the injection pressure P increases, the virtual internal mold pressure V also increases in accordance with the increase in injection pressure P.

[0095] On the other hand, 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, and is set to a value approximately equal to the maximum pressure of the resin material inside the mold 75 when a non-defective product is molded using the mold 75. For this reason, in a situation where the injection pressure P increases due to clogging of the gates connected to some of the cavities 75a, when the filling of the resin material into the mold 75 is stopped because the virtual mold pressure V reaches the upper limit VL, the pressure of the resin material inside the mold 75 other than the cavities 75a where the clogging has occurred will be 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 will be about the same as when a good product is molded, so 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 the occurrence of defective products can be reduced.

[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 and the injection speed S of the screw 20 detected by the encoder 52 when injecting the resin material, and the injection pressure P detected by the load cell 60. When controlling the movement of the screw 20 when injecting the resin material, the virtual mold pressure V is included as a determination factor during control, and the movement is controlled based on the virtual mold pressure V. Therefore, even if a blockage occurs in part of the mold 75 during the filling process, by determining the movement of the screw 20 during the filling process using the virtual mold pressure V as a determination factor, it is possible to prevent the pressure of the resin material in the mold 75 from becoming too high in parts other than the part where the blockage occurred. Therefore, the pressure of the resin material injected into the mold 75 can be appropriately controlled.

[0098] Furthermore, 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 appropriately calculated without placing a pressure sensor in the mold 75. This makes it possible to prevent restrictions on the design of the mold 75 that would be caused by placing 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] Furthermore, 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 a blockage 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 blockage occurred, and to prevent the pressure of the resin material from becoming too high in parts other than the part where the blockage 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] Furthermore, the movement control unit 120, which 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 value PL or the virtual mold pressure V reaches the upper limit value VL, controls the movement of the screw 20 based on the injection pressure P or the virtual mold pressure V. Therefore, during the filling process, abnormality determination is performed based on not only the injection pressure P but also the virtual mold pressure V, and the movement of the screw 20 is controlled, so that the pressure of the resin material filled into the mold 75 can be more reliably prevented from becoming too high. As a result, the pressure of the resin material injected into the mold 75 can be more appropriately controlled.

[0101] Furthermore, when the virtual mold internal pressure V reaches the upper limit VL, the movement control unit 120 controls the movement of the screw 20 based on the injection speed S, which is set as the injection speed S when the virtual mold internal pressure V reaches the upper limit VL. Therefore, when it is determined that the pressure of the resin material filled in the mold 75 has increased based on the virtual mold internal pressure V, the movement control unit 120 can control the movement of the screw 20 so that the pressure of the resin material does not increase any further. This more reliably prevents 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] Furthermore, 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 portion of the mold 75, the pressure in the cavity 75a of the mold 75 can be prevented from becoming too high. This prevents the pressure in portions of the mold 75 other than the portion where the clogging has occurred from becoming too high, allowing appropriate pressure control in portions other than the portion where the clogging has occurred. Therefore, it is possible to minimize the occurrence of defective molded products molded in portions of the mold 75 other than the portion where the clogging has occurred. As a result, the pressure of the resin material injected into the mold 75 can be more appropriately controlled.

[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 within the heating barrel 11 to send the resin material to the front side of the screw 20, the check ring 25 is pushed by the resin material and moves forward within a groove 22 (see FIG. 4 ) formed in the screw 20, and comes into contact with a front groove wall 23. A communication portion 24 that communicates with a front portion of the screw 20 is formed in the front groove wall 23 of the groove 22 of the screw 20, 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 is in contact with the front groove wall 23 of the groove 22, the resin material can move from the rear portion of the check ring 25 to the front portion 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 portion 24.

[0105] On the other hand, when the screw 20 is moved forward to inject the resin material in the heated barrel 11 in the filling step, the check ring 25 is pushed by the resin material and moves rearward within 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 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 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 within 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 dependent on 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, variations can occur in the movement of the check ring 25 within the groove 22, i.e., in the response of the check ring 25.

[0107] In the injection molding machine 1 according to the embodiment, even if variations occur in the response of the check ring 25 as described above, the virtual mold internal pressure V is also included in the judgment factors when controlling the movement of the screw 20 during the filling process, 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 changes in injection speed S, injection pressure P, and virtual 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, variation occurs in the resin material sent to the front side of the screw 20 when metering the resin material, or variation occurs in the regulation of the movement of the resin material to the rear side of the check ring 25 during the filling process, which can cause variation in the injection pressure P as shown in Fig. 11. Furthermore, when variation occurs in the injection pressure P, variation in the virtual mold pressure V also occurs as shown in Fig. 11 due to the variation in the injection pressure P.

[0109] In such a case, if the filling process is controlled without determining whether the virtual mold internal pressure V has reached the upper limit value VL, variations will occur in the amount of resin material filled into the mold 75 during the filling process, which can result in flashing in the molded product if the amount of resin material filled is too large, or a short circuit in the molded product if the amount of resin material filled is too small. For this reason, variations in the response of the check ring 25 can be expected to increase the likelihood of defective molded products.

[0110] In contrast, in this embodiment, the virtual mold internal pressure V is calculated during the filling process and a determination is made as to whether the virtual mold internal pressure V has reached the upper limit value VL, thereby suppressing 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 mold 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 mold pressure V is calculated to determine whether or not the virtual internal mold pressure V has reached the upper limit value VL. Therefore, even if there is variation in the virtual internal mold 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 mold pressure V has reached the upper limit value VL regardless of the variation in the virtual internal mold 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, thereby suppressing molding defects in the molded product.

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

[0114] 13 is an explanatory diagram showing the injection speed S, injection pressure P, and virtual mold pressure V when blow molding is performed without determining whether the virtual mold pressure V has reached the upper limit VL. In blow molding, the upper limit PL of the injection pressure P is set low, so 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 has reached the upper limit PL. The injection speed S set as the injection speed S when the injection pressure P has reached the upper limit PL is slower than the injection speed S when the injection pressure P has not reached the upper limit PL. Therefore, when the injection pressure P has reached 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, thereby suppressing the increase in pressure of the resin material inside the mold 75 and suppressing the occurrence of molding defects such as flash. However, if the injection speed S is not reduced sufficiently when the injection pressure P reaches the upper limit value PL, the increase in pressure of the resin material inside the mold 75 may not be effectively suppressed. In this case, even if blow molding is performed, the pressure of the resin material inside the mold 75 may become high, and the occurrence of molding defects such as flash may not be effectively suppressed.

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

[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 mold pressure V reaches the upper limit VL, the virtual mold pressure V can be prevented from exceeding the upper limit VL, and the virtual mold 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 prevent molding defects, it is possible to more reliably prevent molding defects such as burrs from occurring in the molded product.

[0118] Furthermore, by calculating the virtual mold pressure V and controlling the movement of the screw 20 based on whether the virtual mold 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. In other words, in low-pressure molding, the clamping force of the clamping device 70 is reduced, so 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 mold pressure V has reached the upper limit VL, the pressure of the resin material in the mold 75 can be accurately controlled, thereby suppressing the occurrence of burrs. This makes it possible to suppress molding defects that occur when molding is performed with a reduced clamping force in the clamping device 70, and more appropriate low-pressure molding can be performed.

[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... communication portion, 25... check ring, 30... propulsion mechanism, 31... driving motor, 40... rotation mechanism, 41... rotation mechanism main body portion, 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...controller, 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...velocity control controller, 123...current control controller, 124...pressure control controller, 125...virtual mold internal pressure controller, 140...storage 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 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 that has a cavity into which the resin material injected from the nozzle is filled, and molds 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 a control device that controls the pressure of the resin material in the mold by controlling the movement of the screw, wherein the control device comprises: a pressure loss calculation unit that calculates the pressure loss in the injection device when the resin material is injected, 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 internal mold pressure calculation unit that calculates a virtual internal mold pressure, which is the pressure of the resin material in the mold, by subtracting the pressure loss calculated by the pressure loss calculation unit from the injection pressure detected by the injection pressure detection unit; and a movement control unit that controls movement of the screw when injecting the resin material, and performs the movement control based on the virtual internal mold pressure calculated by the virtual internal mold pressure calculation unit.

2. The control device has an injection pressure judgment unit which judges whether the injection pressure detected by the injection pressure detection unit has reached an upper limit value set for the injection pressure, and a virtual internal mold pressure judgment unit which judges whether the virtual internal mold pressure calculated by the virtual internal mold pressure calculation unit has reached an upper limit value set for the virtual internal mold pressure, and the movement control unit performs the movement control of the screw based on the injection speed which is set for a position in the movement direction of the screw, and when the injection pressure judgment unit judges that the injection pressure has reached the upper limit value or when the virtual internal mold pressure judgment unit judges that the virtual internal mold pressure has reached the upper limit value, performs the movement control of the screw based on the injection pressure or the virtual internal mold pressure.

3. The injection molding machine according to claim 2, wherein the movement control unit, when it is determined by the injection pressure determination unit that the injection pressure has reached the upper limit value, performs the movement control of the screw based on the injection speed which is set as the injection speed when the injection pressure has reached the upper limit value, and, when it is determined by the virtual internal mold pressure determination unit that the virtual internal mold pressure has reached the upper limit value, performs the movement control of the screw based on the injection speed which is set as the injection speed when the virtual internal mold pressure has reached the upper limit value.

4. An injection molding machine according to claim 2 or 3, wherein the upper limit value 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 value.

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