Mold clamping device and mold opening force monitoring method

Abstract

To provide a mold clamping device capable of securing more appropriate operation.SOLUTION: A mold clamping device 1 includes: a toggle link mechanism (50) equipped with a crosshead (62) that opens, closes, and clamps a fixed mold (13) and a movable mold (23) via a fixed platen (10) and a movable platen (20); a servomotor (74) that is a driving source of the toggle link mechanism; and a controller (80) that controls an operation of the servomotor (74). The controller (80) compares an actual mold opening force (Fr) actually generated during a mold opening operation to a preset first allowable mold opening force (F1) in a mold opening operation to separate the movable mold (23) from the fixed mold (13).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a mold clamping device equipped with a toggle link mechanism. [Background technology]

[0002] A clamping device equipped with a toggle link mechanism generates a clamping force on a pair of dies in an injection molding machine, a die casting machine, etc. For example, in an injection molding machine, a molded product of a predetermined shape can be obtained by injecting molten resin at high pressure into the cavities of a pair of dies to which a clamping force is applied. The clamping force is set on the premise that the high-pressure molten resin does not leak out of the dies.

[0003] In a mold clamping device equipped with a toggle link mechanism, a servo motor is used as a drive source for the toggle link mechanism, as disclosed in Patent Documents 1 and 2. This servo motor clamps a pair of molds and opens them. Patent Document 1 proposes monitoring the output torque (actual torque) of the servo motor for opening and closing the mold when the mold is opened, and issuing a warning when that value exceeds a preset upper limit. Patent Document 2 proposes stopping the molding operation when the output torque of the servo motor for opening and closing the mold reaches an upper torque limit. In this way, Patent Document 1 and Patent Document 2 aim to ensure proper operation of the mold clamping device by monitoring and evaluating the output torque of the servo motor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2002-326265 A [Patent Document 2] Patent Publication No. 2021-024185 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the torque generated in the servo motor that drives the toggle link mechanism is not proportional to the actual mold opening force generated in the pair of molds, so there is a risk that proper operation of the mold clamping unit cannot be ensured by merely monitoring the actual torque and comparing it with the set torque.

[0006] In view of the above, an object of the present invention is to provide a mold clamping device and a mold opening force monitoring method that can ensure more appropriate operation. [Means for solving the problem]

[0007] The clamping device of the present invention comprises a toggle link mechanism with a crosshead that opens / closes and clamps a movable mold and a fixed mold via a movable platen and a fixed platen, a servo motor that is the driving source of the toggle link mechanism, and a controller that controls the operation of the servo motor. In the process of a mold opening operation for separating the movable mold from the fixed mold, the controller compares an actual mold opening force that is actually generated during the mold opening operation with a first allowable mold opening force that is set in advance.

[0008] The actual mold opening force in the present invention is preferably determined based on the actual torque generated in the servo motor and the current position of the crosshead.

[0009] The first allowable mold opening force in the present invention is preferably set based on the strength of an attachment means for attaching the fixed mold to the fixed platen and an attachment means for attaching the movable mold to the movable platen.

[0010] The controller in the present invention preferably stops the operation of the servo motor or issues a warning based on the result of the comparison between the actual mold opening force and the first allowable mold opening force. In the present invention, both the operation of the servo motor and the warning may be stopped.

[0011] The controller of the present invention preferably switches the object to be compared with the actual mold opening force to a second allowable mold opening force which is smaller than the first allowable mold opening force after a predetermined timing when the position of the crosshead moves rearward from the mold touch position.

[0012] The controller in the present invention preferably stops the operation of the servo motor or issues a warning based on the result of the comparison between the actual mold opening force and the second allowable mold opening force. In the present invention, both the operation of the servo motor and the warning may be stopped.

[0013] The mold opening force monitoring method of the present invention includes a mold opening operation in which a crosshead of a toggle link mechanism is moved by the driving force of a servo motor to separate a movable mold from a fixed mold, the mold opening force monitoring method comprising: a mold opening force calculation process for calculating an actual mold opening force based on an actual torque generated in the servo motor and a current position of the crosshead; and a mold opening force comparison process for comparing the actual mold opening force calculated in the mold opening force calculation process with a predetermined first allowable mold opening force. Effect of the Invention

[0014] According to the present invention, a mold clamping device and a method for monitoring a mold opening force that can ensure more appropriate operation are provided. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a side view showing a schematic configuration of a mold clamping device according to a first embodiment. [Diagram 2] FIG. 2 is a rear view showing a schematic configuration of the mold clamping device of FIG. [Diagram 3] FIG. 2 is a diagram showing a configuration of a controller of the mold clamping device of the first embodiment. [Figure 4] 4A to 4C are diagrams illustrating a mold clamping operation in the mold clamping device of the first embodiment. [Diagram 5] 6A to 6C are diagrams illustrating a control procedure in a mold opening operation in the first embodiment. [Figure 6] 1 is a diagram showing an example of a relationship between a mold clamping position and a mold opening force in a mold clamping device. FIG. [Figure 7] 13A to 13C are diagrams illustrating a control procedure in a mold opening operation in the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of a mold clamping device according to the present invention will be described with reference to the drawings. An example of a mold clamping device 1 equipped with a toggle link mechanism to which the mold opening force monitoring method according to this embodiment is applied will be described first, and then the mold opening force monitoring method according to this embodiment will be mentioned. The mold opening force monitoring method according to this embodiment is widely applicable to devices that clamp a pair of molds, such as injection molding machines and die casting machines.

[0017] [First embodiment] [Configuration of the mold clamping unit 1: Figure 1] As shown in Figs. 1 and 2, the mold clamping device 1 according to the first embodiment mainly includes a fixed platen 10 and a movable platen 20 that are arranged in parallel with each other at a distance in the mold opening / closing direction x. The mold clamping device 1 also includes a toggle link mechanism 50 that generates a mold clamping force on the fixed platen 10 and the movable platen 20, and a link housing 30 that supports the toggle link mechanism 50 together with the movable platen 20. The fixed platen 10, the movable platen 20, and the link housing 30 are placed on a machine base 2 that is installed on the floor surface with tie bars 3 penetrating each of the four corners. Each component will be described below in order. In the mold clamping device 1, the mold opening / closing direction x and the height direction y are specified as shown in Fig. 1.

[0018] [Fixed platen 10, movable platen 20, link housing 30: Figure 1] 1, the facing surfaces of the fixed platen 10 and the movable platen 20 constitute mold mounting surfaces 11, 21. A fixed mold 13 is supported on the mold mounting surface 11 of the fixed platen 10, and a movable mold 23 is supported on the mold mounting surface 21 of the movable platen 20. The fixed mold 13 and the movable mold 23 are supported by the fixed platen 10 and the movable platen 20, respectively, with fasteners such as bolts (not shown). The fixed platen 10 is fixed in position relative to the machine base 2, while the movable platen 20 is installed on the machine base 2 so as to be movable back and forth on the machine base 2 in the mold opening / closing direction x relative to the fixed platen 10. For example, the movable platen 20 is slidably mounted on a support means such as a guide shoe, a slide rail, or a linear guide provided on the machine base 2. The link housing 30 is slidably mounted on the machine base 2. When the mold thickness driving unit 35 is driven, the link housing 30 is guided by the tie bars 3 and can move integrally with the movable platen 20 and a toggle link mechanism 50 (described later) on the machine base 2 in the mold opening / closing direction x.

[0019] A through hole is formed in the center of the stationary platen 10 on the side opposite to the surface on which the stationary mold 13 is supported, into which an injection nozzle or injection sleeve of an injection device (not shown) can be inserted. The movable platen 20 and the link housing 30 are connected by a toggle link mechanism 50. When the toggle link mechanism 50 expands and contracts, the movable platen 20 approaches or moves away from the fixed platen 10 in the mold opening and closing direction x.

[0020] [Toggle link mechanism 50: Figures 1 and 2] 1, the toggle link mechanism 50 includes a pair of upper and lower link members 51, 51 bridged between the movable platen 20 and the link housing 30, and a crosshead 62 that moves in the mold opening / closing direction x to expand and contract each of the pair of upper and lower link members 51, 51. The toggle link mechanism 50 also includes a crosshead driver 70 that moves the crosshead 62 in the mold opening / closing direction x.

[0021] Each link member 51 has a toggle link 54, one end of which is swingably connected to a platen-side link support member 52 of the movable platen 20 by a link pin 55. Also, each link member 51 has a mid link 58, one end of which is swingably connected to a housing-side link support member 56 of the link housing 30 by a link pin 59. The other end of the toggle link 54 and the other end of the mid link 58 are swingably connected to each other by a link pin 61.

[0022] The crosshead 62 is provided between a pair of upper and lower mid links 58, 58. One end of a crosshead link 63 is swingably connected to both ends of the crosshead 62 by a link pin 64, and the other end of the crosshead link 63 is swingably connected to the mid links 58, 58 by a link pin 65. In the first embodiment, the crosshead link 63 as described above is connected to the mid link 58 by the link pin 65, but the present invention is not limited to this, and for example, the crosshead link 63 may be connected to the mid link 58 and the link pin 61 of the toggle link 54. In this manner, the connection position of the crosshead link 63 is appropriately selected at the design stage of the toggle link mechanism 50 based on the toggle magnification, the mold opening / closing stroke, etc. The link member 51 is configured such that the toggle link 54 and the mid link 58 swing about the link pins 55, 59, respectively, and the crosshead 62 moves in the mold opening / closing direction x, thereby expanding or bending.

[0023] As shown in Figs. 1 and 2, the crosshead driving device 70 includes a ball screw nut 71 embedded in the crosshead 62, and a ball screw shaft 72 rotatably provided penetrating the link housing 30 and screwed with the ball screw nut 71. The crosshead driving device 70 also includes a chain pulley 73 attached to the base end of the ball screw shaft 72, and a mold clamping motor 74 attached to the surface of the link housing 30 opposite to the mounting surface of the toggle link mechanism 50. The crosshead driving device 70 also includes a motor pulley 75 attached to the rotating shaft of the mold clamping motor 74, and a chain belt 76 stretched between the chain pulley 73 and the motor pulley 75. The rotational force of the mold clamping motor 74 is transmitted to the ball screw shaft 72 via the chain belt 76. The mold clamping motor 74, which is composed of a servo motor as a driving source, includes an encoder built in, and is configured to detect the moving direction of the crosshead 62, the amount of movement in the mold opening and closing direction x, and the moving speed, etc., by this encoder. In the first embodiment, an example is shown in which the rotational force of the mold clamping motor 74 is transmitted to the ball screw shaft 72 using the chain belt 76 as described above, but the present invention is not limited to this. For example, a rotational force transmission mechanism such as a timing belt or a transmission gear may be used as the rotational force transmission mechanism, or the rotational force transmission mechanism may be omitted and the mold clamping motor 74 and the ball screw shaft 72 may be directly connected using a coupling.

[0024] [Tie bar 3: Figure 1, Figure 2] As shown in Figures 1 and 2, multiple tie bars 3, typically four, are arranged to penetrate the four corners of the fixed platen 10, the movable platen 20, and the link housing 30, and their elastic force generates a clamping force on the fixed mold 13 and the movable mold 23 via the fixed platen 10 and the movable platen 20. Fixed nuts 15 are provided at the four corners of the surface of the fixed platen 10 opposite to the mold mounting surface 11, and fitted with one end of each tie bar 3. The fixed nuts 15 regulate the relative movement of each tie bar 3 in the mold opening / closing direction x and the rotational movement of each tie bar 3 around the central axis along the longitudinal direction. Drive nuts 31 are provided at the four corners of the back surface of the link housing 30, and engage with threaded portions (not shown) formed on the other end of each tie bar 3. The drive nuts 31 are rotatably supported by the link housing 30, and are configured to rotate by the mold thickness drive portion 35 and screw into the threaded portions of each tie bar 3. As a result, the link housing 30 and the toggle link mechanism 50 and movable platen 20 connected thereto are configured to reciprocate in the mold opening / closing direction x.

[0025] [Mold thickness drive unit 35: Fig. 1, Fig. 2] As shown in Figs. 1 and 2, the die thickness driving unit 35 includes, for example, a die height motor 36 attached to the upper surface of the link housing 30 and a motor pulley 38 attached to the rotation shaft of the die height motor 36. The die thickness driving unit 35 also includes a chain pulley 40 attached to the periphery of each of the four drive nuts 31, and a transmission gear 42 rotatably attached to the surface of the link housing 30 opposite to the mounting surface of the toggle link mechanism 50. The die thickness driving unit 35 also includes a chain belt 44 stretched between the motor pulley 38 and the transmission gear 42, and a chain belt 46 stretched between the four chain pulleys 40 and the transmission gear 42. The die thickness driving unit 35 transmits the rotational force of the die height motor 36 to each drive nut 31 via the chain belts 44 and 46. In the first embodiment, in addition to the chain type die thickness driving unit as described above, a gear type die thickness driving unit that transmits the rotational force of the die height motor 36 to each drive nut can be used.

[0026] [Controller 80: Figure 3] The controller 80 controls the movement of the movable platen 20 supporting the movable mold 23, the toggle link mechanism 50, and the link housing 30 in the mold opening / closing direction x through control of the drive of the mold thickness drive unit 35. In addition, the controller 80 controls the mold closing, mold clamping, and mold opening operations of the movable mold 23 supported by the movable platen 20 relative to the fixed mold 13 supported by the fixed platen 10 through control of the drive of the crosshead drive device 70.

[0027] [Controller 80 configuration] As shown in Fig. 3, the controller 80 includes a display unit 81 for displaying necessary information, and an input unit 83 that is operated by an operator and receives input of, for example, mold thickness information, mold clamping force information, etc. The controller 80 also includes a storage unit 85 for storing various information, an instruction unit 87 for instructing each operation of the mold clamping device 1, and a processing unit 89 for performing processing according to the first embodiment. The processing according to the first embodiment includes a calculation for determining the actual mold opening force Fr, and a comparison between the determined actual mold opening force Fr and a first allowable mold opening force F1 that is determined in advance. This series of processing will be described in more detail later with reference to Fig. 5. In this example, the instruction unit 87 and the processing unit 89 are independent in order to clarify the presence of the processing unit 89, but the instruction unit 87 may also have the functions of the processing unit 89. The controller 80 is composed of a computer device, the input unit 83 is composed of soft keys or hard keys, and the display unit 81 is composed of, for example, an LCD (Liquid Crystal Display). Furthermore, although not shown, a speaker that emits sound may also be provided. A warning, which will be described later, can be issued from either or both of the display unit 81 and the speaker.

[0028] [Storage section 85] The storage unit 85 stores at least the following arithmetic formula (1) for calculating the first allowable mold opening force F1 and the actual mold opening force Fr. The storage unit 85 can store the following information and other information. The first allowable mold opening force F1 is selected from the range of allowable mold opening forces and compared with the actual mold opening force Fr. The first allowable mold opening force F1 is set in advance and stored in the memory unit 85. The first allowable mold opening force F1 is set based on the strength of the mounting means for mounting the fixed mold 13 to the fixed platen 10 and the mounting means for mounting the movable mold 23 to the movable platen 20. If the actual mold opening force Fr exceeds the strength R of these mounting means, the mounting means will be damaged. Therefore, the first allowable mold opening force F1 needs to be at least a value smaller than the strength R, and for example, the first allowable mold opening force F1 is preferably set to 90% of the strength R, more preferably 80% of the strength R.

[0029] In addition, the mold clamping device 1 using the toggle link mechanism 50 requires the largest torque from the mold clamping motor 74 when releasing the mold clamping state in which the link member 51 is straight and making the link member 51 bent. Therefore, if the first allowable mold opening force F1 is set too small in order to prioritize safety, normal mold opening operation becomes difficult. Conversely, if the first allowable mold opening force F1 is set too large in order to prioritize releasing the mold clamped state, there is a high possibility that the strength of the mold mounting means will be exceeded.

[0030] When bolts, which have a simple structure, are used as the attachment means, the strength R is determined by the product of the breaking strength of the bolts used and the number of bolts. If the attachment means is a hydraulic clamp or magnetic clamp, the strength R is determined by the allowable load (allowable strength) listed in the specifications for each clamp.

[0031] Formula for calculating actual mold opening force Fr: This is a formula for calculating the actual mold opening force Fr based on the torque generated in the mold clamping motor 74 when the mold is opened, that is, the actual torque Tr, and for example, the following formula (1) is given. The mold touch position (mold opening position) in formula (1) corresponds to the current position of the crosshead 62. Fr=Tr / (1 / 2π)·ε·L·(1 / fz)…Equation (1) Tr: Actual torque, ε: Reduction ratio of belt pulley, L: Lead of ball screw shaft 72 for crosshead 62, fz: Toggle ratio at the mold touch position (mold opening position) when the set mold clamping force is Z (kN) Reduction ratio of belt pulley: Reduction ratio between the clamping motor 74 and the chain pulley 73 via the chain belt 76 Toggle magnification: the magnification between the force driving the crosshead 62 and the force with which the movable platen 20 operates, multiplied by the toggle link mechanism 50

[0032] Here, the mold touch position (mold opening position) in formula (1) corresponds to the current position of the crosshead 62. Therefore, formula (1) shows that the actual mold opening force Fr is calculated based on the actual torque Tr generated in the mold clamping motor 74, which is a servo motor, and the current position of the crosshead 62.

[0033] [Instruction section 87] The instruction unit 87 reads out various information stored in the memory unit 85 in accordance with instructions and selections from the operator, generates operation command information, and transmits the generated operation command information to each drive unit, such as the die-height motor 36 of the die thickness drive unit 35 and the mold clamping motor 74 of the crosshead drive device 70. Moreover, as operational command information specific to the first embodiment, in response to a judgment result in a processing unit 89 described next, instruction information for displaying a warning is sent to the display unit 81, and instruction information for stopping the mold opening operation is also sent to the mold clamping motor 74. The instruction unit 87 also issues various instruction information for the operation of the mold clamping device 1, which will be described below.

[0034] [Processing section 89] When injection molding is completed and the mold opening operation starts, the processing unit 89 receives data on the actual torque Tr and calculates the actual mold opening force Fr based on the formula (1) read out from the storage unit 85. The processing unit 89 also compares the first allowable mold opening force F1 read out from the storage unit 85 with the calculated actual mold opening force Fr and sends the comparison result to the instruction unit 87. The processing unit 89 can also perform various other processes in the operation of the mold clamping apparatus 1, which will be described below.

[0035] [Outline of operation of the mold clamping unit 1: Figure 4] Next, a series of operations for adjusting the mold clamping force in the mold clamping device 1 will be described with reference to Fig. 4. Fig. 4 shows the process from the mold open state (Fig. 4(a)) through the mold touch state (Fig. 4(b)) to the mold clamping state (Fig. 4(c)).

[0036] After the molds (fixed mold 13 and movable mold 23) are attached to the mold clamping device 1, they are in an open state (Figure 4(a)), and the mold clamping motor 74 of the crosshead drive device 70 is driven to advance the movable mold 23 until it approaches a predetermined distance from the fixed mold 13 (not shown). Here, the forward movement refers to the movement of the movable die 23 in the direction approaching the fixed die 13, and the backward movement refers to the movement of the movable die 23 in the direction moving away from the fixed die 13.

[0037] Next, the die-height motor 36 is driven to move the movable platen 20 supporting the movable mold 23, the toggle link mechanism 50, and the link housing 30 together forward and backward relative to the fixed platen 10, thereby adjusting the length of the tie bars 3 between the fixed platen 10 and the link housing 30. This length adjustment means adjustment of the amount of extension of the tie bars 3 corresponding to the set mold clamping force, which will be described later.

[0038] Next, when the die-height motor 36 is driven to advance the movable platen 20 supporting the movable die 23, the toggle link mechanism 50, and the link housing 30 as a unit toward the fixed die 13, the movable die 23 comes into contact with the fixed die 13 as shown in Fig. 4(b). This is the die touch state. For example, when the current flowing through the die-height motor 36 reaches a predetermined value, it is assumed that the movable die 23 has come into close contact with the fixed die 13, and the advancement of the movable die 23 by the die-height motor 36 is stopped. At this time, the link member 51 of the toggle link mechanism 50 is maintained in a bent state, and the position of the crosshead 62 at this time is referred to as the die touch position.

[0039] When the mold touch is reached, the crosshead 62 is advanced by driving the mold clamping motor 74, and the link member 51 is stretched in a straight line between the movable platen 20 and the link housing 30 as shown in Fig. 4(c). As a result, the tie bar 3 engaged between the link housing 30 and the fixed platen 10 is stretched by a predetermined amount λ. The stretched tie bar 3 attempts to return to its original state, and an elastic recovery force corresponding to the amount of stretch λ of the tie bar 3 acts as a mold clamping force between the movable platen 20 and the fixed platen 10 via the toggle link mechanism 50, generating an actual mold clamping force f on the fixed mold 13 and the movable mold 23. This actual clamping force f is compared with a preset clamping force Z, and adjustment of the position of the link housing 30 and adjustment of the bent state of the link member 51 are repeated until the actual clamping force f matches the preset clamping force Z.

[0040] In the mold clamping state of Fig. 4(c), the mold opening operation is performed after the molten resin to be molded, etc., is filled inside the molding cavity formed between the fixed mold 13 and the movable mold 23. The mold opening operation is the opposite of the mold closing and mold clamping operations described above, and is performed in the order of Fig. 4(c), Fig. 4(b) and Fig. 4(a).

[0041] In the toggle link mechanism 50, when the link member 51 passes the dead point immediately before it becomes straight, the force required to move the crosshead 62 forward becomes maximum. On the other hand, the link member 51 in the straight state functions as a tension rod, and a driving force to maintain the current position of the crosshead 62 is no longer required, so there is no need to supply power to maintain the mold clamping state.

[0042] The toggle link mechanism 50 extends the tie bar 3 by straightening the bent link member 51, and causes an elastic force corresponding to this extension to act as a clamping force between the fixed mold 13 and the movable mold 23. When the link member 51 is in a straight state, that is, when the mold clamping is completed, the forward limit position, which is the mold clamping completion position of the crosshead 62, becomes 0 (zero). Therefore, in adjusting the mold clamping force, the set mold clamping force Z (for example, equivalent to the extension amount of the tie bar 3) is determined by the position (high pressure switching position) of the crosshead 62 when the link member 51 is bent.

[0043] Then, when the crosshead 62 with the link member 51 bent is at the high pressure switching position, the toggle link mechanism 50, and the toggle link mechanism 50 and the link housing 30 move together, causing the movable die 23 fixed to the movable platen 20 to contact the fixed die 13 fixed to the fixed platen 10. This is the state called die touch or die touch. As a result, the link member 51 is adjusted so that the movable mold 23 touches the fixed mold 13 at a position that matches the mold thickness of the fixed mold 13 and the movable mold 23, with the link member 51 in a bent state corresponding to the high pressure switching position.Therefore, by advancing the crosshead 62 to the mold clamping completion position (= current forward position) and setting the link member 51 to a straight state, a set mold clamping force can be generated for the fixed mold 13 and movable mold 23 to be used. In addition, in the above-described mold clamping force adjustment, the high pressure switching position of the mold touch recognized for control purposes is the mold release start position from the viewpoint of the mold opening operation.

[0044] In other words, during the mold opening operation, while the crosshead 62 is retreated from the mold clamping completion position to the mold touch position, which is the high pressure switching position, the compression amount of the fixed mold 13 and the movable mold 23 in the mold clamping direction simply returns to near the original mold thickness, but the movable mold 23 does not move away from the fixed mold 13. Therefore, during the mold opening operation, while the crosshead 62 is retreated from the mold clamping completion position to the high pressure switching position (mold touch position), even if a high mold opening force is generated in accordance with the actual torque Tr generated in the mold clamping motor 74 made of a servo motor, the movable mold 23 does not substantially separate from the fixed mold 13. Such a high mold opening force does not directly act on the mounting means of the fixed mold 13 and the movable mold 23 to the mold mounting surfaces 11, 21.

[0045] [Control procedure for mold opening operation: Figure 5] In the mold clamping device 1, the actual mold opening force Fr is monitored during the mold opening operation. A procedure for controlling the mold opening operation, including this monitoring, will be described with reference to Fig. 5. This procedure is realized by the controller 80. After mold opening has started, it is determined whether mold opening has ended based on the current position Ph of the crosshead 62 (FIG. 5, S103). For this purpose, the current position Ph of the crosshead 62 is detected and compared with a predetermined mold opening end position Pe. If the position has not reached the end position Pe, the mold opening operation continues (FIG. 5, S103, N), and if the current position Ph has reached the end position Pe, mold opening ends (FIG. 5, S103, Y, S115).

[0046] As the mold opening operation continues, the actual torque Tr generated in the mold clamping motor 74 is detected (FIG. 5, S105), and the detected actual torque Tr is acquired by the controller 80. The controller 80, which has acquired the actual torque Tr, calculates the actual mold opening force Fr using the above-mentioned formula (1) (FIG. 5, S107, mold opening force calculation step). This detection of the actual torque Tr and calculation of the actual mold opening force Fr are continued until the crosshead 62 reaches a predetermined mold opening end position Pe. The detection of the actual torque Tr and the calculation of the actual die opening force Fr based on the actual torque Tr can be performed continuously in time or at predetermined time intervals.

[0047] The controller 80 judges whether the calculated actual mold opening force Fr is larger than the first allowable mold opening force F1 (FIG. 5, S109, mold opening force comparison step). Specifically, the controller 80 monitors whether the actual mold opening force Fr exceeds the first allowable mold opening force F1. If the actual mold opening force Fr≦the first allowable mold opening force F1 (FIG. 5, S109, N), the controller 80 continues to determine the end of mold opening (FIG. 5, S103), detect the actual torque Tr (FIG. 5, S105), and calculate the actual mold opening force Fr (FIG. 5, S107).

[0048] On the other hand, if the actual mold opening force Fr>the first allowable mold opening force F1 (FIG. 5, S109, Y), the controller 80 instructs the mold clamping motor 74 to stop driving (FIG. 5, S111) and issues a warning (FIG. 5, S113). One example of the warning is to display text information such as "The mold clamping motor 74 has been stopped because the actual mold opening force Fr has increased" on the display unit 81. If the controller 80 is equipped with a speaker, the warning can be issued by audio information. The operator who recognizes the warning can perform an operation to stop driving the mold clamping motor 74, or can continue the mold opening operation as is.

[0049] Here, two types of responses, namely, stopping the drive of the mold clamping motor 74 and issuing a warning, are shown, but the first embodiment is not limited to this and only one of the responses may be used. In other words, the controller 80 can instruct the mold clamping motor 74 to stop without issuing a warning, and can also instruct a warning without stopping the mold clamping motor 74.

[0050] [Reason for comparing actual mold opening force Fr and first allowable mold opening force F1] It is also possible to set an allowable torque T1 in advance with respect to the actual torque Tr, and determine which is larger between the actual torque Tr and the allowable torque T1. However, as will be described below with reference to Fig. 6, when the toggle link mechanism 50 is used, the torque and the mold opening force acting on the mold are not in a proportional relationship. Therefore, even if the relationship between the actual torque Tr and the allowable torque T1 is determined, the initial objective cannot be achieved.

[0051] 6 shows a graph in which the actual mold opening force Fr generated when the mold opening operation is actually performed is calculated using a predetermined formula based on the actual torque Tr generated in the mold clamping motor 74 and the current position of the crosshead 62, with the upper limit (torque limit) of the motor torque of the mold clamping motor 74 consisting of a servo motor being set to 50% of the rated torque. The vertical axis represents the calculated actual mold opening force Fr, and the horizontal axis represents the mold clamping position. This mold clamping position is synonymous with the position of the crosshead.

[0052] 6, the origin 0.00 is the position of the crosshead 62 when mold clamping is completed, and the greater the value on the horizontal axis, the more the crosshead 62 retreats. This retreat refers to a state in which the crosshead 62 moves toward the link housing 30 and the link member 51 is bent. As described above, when the link member 51 passes the dead point immediately before it becomes straight, the maximum force is required to advance the crosshead 62. In other words, in the mold opening operation, when the link member 51 passes the dead point when it is bent from the straight state, the actual torque generated in the mold clamping motor 74 becomes maximum. Therefore, in response to the high mold opening force near the origin 0.00 shown in FIG. 6, the actual torque Tr generated in the servo motor also becomes maximum during the mold opening operation.

[0053] On the other hand, if the mold opening operation is normal, the actual mold opening force Fr decreases as the operation progresses. In accordance with the decrease in the actual mold opening force Fr during this period, the actual torque Tr generated in the servo motor also decreases from the actual torque generated at the dead point.

[0054] Here, when a small mold clamping force is set, the actual mold opening force is larger than when a larger mold clamping force is set. This will be described with reference to FIG. For example, in FIG. 6, the clamping force is set at the point where the clamping position (crosshead position) is 2.00 mm, which is the mold touch position (high pressure switching position / mold release start position), and this is set as the first clamping force setting. The mold clamping force at this time corresponds to the extension amount of the tie bar 3 when the crosshead position is advanced from 2.00 mm to the forward limit of 0.00 mm. Under these settings, when the mold opening operation is performed from the mold clamped state and the crosshead 62 is retreated from the mold clamping completion position to the high pressure switching position (mold touch position), the movable mold 23 is substantially separated from the fixed mold 13 after the high pressure switching position (mold touch position). As explained above, the actual mold opening force Fr acts on the mounting means of both molds to the mold mounting surfaces 11, 21 after the crosshead 62 reaches the high pressure switching position (mold touch position), and the actual mold opening force Fr at this time is about 500 kN from FIG. 6.

[0055] On the other hand, in Figure 6, the point where the mold clamping position (crosshead position) is 0.50 mm is set as the mold touch position (high pressure switching position) described above, and this is set as the second mold clamping force setting. Even with this setting, the mold clamping force is based on the extension amount of the tie-bars 3 when the crosshead position is advanced from 0.50 mm to the forward limit of 0.00 mm. Therefore, the mold clamping force set in this second mold clamping force setting is smaller than the mold clamping force set in the first mold clamping force setting. The actual mold opening force at this time is about 1000 kN, as shown in Figure 6, which is almost twice as much as the first mold clamping force setting.

[0056] In this way, in the mold clamping unit 1 using the toggle link mechanism 50, the actual mold opening force generated is not proportional to the actual torque generated in the servo motor due to the toggle characteristics and mold clamping force setting. Therefore, when monitoring the actual torque Tr generated in the mold clamping motor 74 consisting of a servo motor, or by comparing the actual torque Tr with a set allowable upper limit torque, it is difficult to appropriately set the allowable upper limit torque in association with the strength of the attachment means to the mold attachment surfaces 11, 21 of both molds.

[0057] [Effects of the first embodiment] According to the mold clamping device 1, when the actual mold opening force Fr exceeds the first allowable mold opening force F1, a warning is issued and the driving of the mold clamping motor 74 is stopped. Therefore, it is possible to prevent a mold opening force exceeding the strength of the mold mounting means of the fixed mold 13 attached to the fixed platen 10 and the movable mold 23 attached to the movable platen 20 from being applied to the mold mounting means. This makes it possible to prevent the mold mounting means from being damaged and the fixed mold 13 and the movable mold 23 from falling off the fixed platen 10 and the movable platen 20, respectively, due to damage to the mold mounting means.

[0058] Second Embodiment Next, a mold clamping system according to a second embodiment will be described with reference to Fig. 7. In the following, the second embodiment will be described focusing on a control procedure in a mold opening operation that is different from that of the mold clamping system 1 of the first embodiment, and a description of parts common to the mold clamping system 1 of the first embodiment will be omitted.

[0059] In the control procedure of the mold opening operation in the second embodiment, as shown in FIG. 7, either the first allowable mold opening force F1 or the second allowable mold opening force F2 is compared with the actual mold opening force Fr depending on the current position Ph of the crosshead 62. The first allowable mold opening force F1 and the second allowable mold opening force F2 have a relationship of F1>F2. Then, during the initial period after the mold opening is started, the first allowable mold opening force F1 is compared with the actual mold opening force Fr, and during the period from the initial period until the end of the mold opening, the second allowable mold opening force F2 is compared with the actual mold opening force Fr (FIG. 7 S109, S110). In this way, the comparison target of the actual mold opening force Fr is two-staged because an excessive actual mold opening force Fr occurs immediately after the mold opening is started, and in order to deal with this excessive actual mold opening force Fr, the relatively large first allowable mold opening force F1 is selected initially, and the relatively small second allowable mold opening force F2 is selected after a certain timing thereafter.

[0060] In the second embodiment, the current position Ph of the crosshead 62 is detected, and it is determined whether the detected current position Ph exceeds the switching position Pc (FIG. 7, S108). The switching position Pc is set at a position a predetermined distance away from the die touch point. If the current position Ph of the crosshead 62 has not reached the switching position Pc (FIG. 7, S108, N), the controller 80 judges the magnitude relationship between the actual mold opening force Fr and the first allowable mold opening force F1 (FIG. 7, S109). If the current position Ph of the crosshead 62 has reached the switching position Pc (FIG. 7, S108, Y), the controller 80 judges the magnitude relationship between the actual mold opening force Fr and the second allowable mold opening force F2 (FIG. 7, S110). If the actual mold opening force Fr exceeds the first allowable mold opening force F1 or exceeds the second allowable mold opening force F2 (FIG. 7, S109, Y, FIG. 7, S110, Y), the mold clamping motor 74 is stopped (FIG. 7, S111) and a warning is issued (FIG. 7, S113).

[0061] In a mold incorporating an angular pin or a slide core, the second allowable mold opening force F2 is set to, for example, 80% or 50% of the first allowable mold opening force F1. In a mold without an angular pin, a slide core, or other sliding parts within the mold, the second allowable mold opening force F2 may be set so that preventive maintenance can be performed by detecting poor lubrication of the sliding parts of the movable platen 20, or an increase in sliding resistance due to wear or poor lubrication of the link bush of the link member 51. Furthermore, as shown in FIG. 6, the actual mold opening force that occurs during normal, trouble-free mold opening operation when actual molding is performed is recorded as data corresponding to the current position Ph of the crosshead 62 (normal mold opening force data acquisition process), and the mold opening force obtained by adding an allowable value to this data is set as the second allowable mold opening force F2 (second allowable mold opening force setting process). In this case, the mold opening force obtained by increasing the graph of the actual mold opening force Fr generated in accordance with the current position Ph of the crosshead 62 at a uniform rate may be used as the second allowable mold opening force F2 corresponding to the current position Ph of the crosshead 62. Furthermore, during normal mold opening operation, the actual mold opening force Fr generated gradually decreases, so a fixed value may be adopted as the subsequent second allowable mold opening force F2, which is the mold opening force obtained by adding a predetermined allowable value to the actual mold opening force Fr generated at the time of switching to the second allowable mold opening force F2.

[0062] [Effects of the second embodiment] In the second embodiment, as in the first embodiment, while determining the magnitude relationship between the actual mold opening force Fr and the first allowable mold opening force F1, it is possible to prevent the mold mounting means from being damaged and the fixed mold 13 and the movable mold 23 from falling from the fixed platen 10 and the movable platen 20, respectively, due to damage to the mold mounting means. In addition, while judging the magnitude relationship between the actual mold opening force Fr and the second allowable mold opening force F2, malfunctions in the mold opening process can be detected and preventive maintenance can be performed accordingly. In other words, factors that cause the actual mold opening force Fr to increase after the switching position Pc include poor lubrication of the mold sliding parts and the movable platen 20, and wear and poor lubrication of the bushings of the link member 51. Therefore, preventive maintenance can be performed after the switching position Pc by comparing the second allowable mold opening force F2, which corresponds to an increase in sliding resistance, with the actual mold opening force Fr.

[0063] In addition to the above, the configurations given in the above embodiments can be selected or appropriately changed to other configurations without departing from the spirit of the present invention.

[0064] For example, the present invention can also be applied to a mold that employs a mechanism for driving a block within the mold using the force of mold opening, such as an angular pin or a slide core. In the case of this die, if the slide core cannot be driven normally due to poor lubrication of the sliding parts such as the angular pin and the slide core or the intrusion of foreign matter into these sliding parts, the actual die opening force Fr will increase excessively anywhere in the up and down sliding stroke range of the slide core, which may result in damage to the angular pin or the slide core.

[0065] In the above, the actual mold opening force Fr is calculated based on the actual torque Tr using formula (1). However, in addition to this, the present invention can also directly detect the actual stress using a stress detection means, such as a load cell, provided on the pressure-receiving member of the toggle link mechanism 50, such as the tie bar 3, or calculate the actual mold opening force based on the detected actual stress. [Explanation of symbols]

[0066] 1,5 Mold clamping device 2 Machine Base 3 Tie bar 10 Fixed plate 11,21 Mold mounting surface 13 Fixed mold 15 Fixing nut 20 Movable plate 23 Movable mold 30 Link housing 31 Drive nut 35-inch thick drive unit 36 Die height motor 38 Motor pulley 40 Chain pulley 42 Transmission Gear 44,46 Chain belt 50 Toggle link mechanism 51 Link member 52 Platen side link support member 54 Toggle Link 55 Link pin 56 Housing side link support member 58 Midlink 59 Link pin 61,64,65 Link pin 62 Crosshead 63 Crosshead link 70 Crosshead drive unit 71 Ball screw nut 72 Ball screw shaft 73 Chain Pulley 74 Clamping motor 75 Motor pulley 76 Chain Belt 80 Controller 81 Display section 83 Input section 85 Storage section 87 Instruction section 89 Processing section x Mold opening / closing direction y Height direction

Claims

1. a toggle link mechanism having a crosshead for opening / closing and clamping the fixed mold and the movable mold via the fixed platen and the movable platen; A servo motor that is a drive source of the toggle link mechanism; A controller for controlling the operation of the servo motor, The controller: In a mold opening operation in which the movable mold is separated from the fixed mold, comparing an actual mold opening force that is actually generated during the mold opening operation with a first allowable mold opening force that is set in advance; The mold clamping device according to claim 1, wherein the actual mold opening force is calculated based on an actual torque generated in the servo motor and a current position of the crosshead.

2. The first allowable mold opening force is is set based on the strength of the mounting means for mounting the fixed mold to the fixed platen and the mounting means for mounting the movable mold to the movable platen. The mold clamping device according to claim 1 .

3. The controller: Stopping the operation of the servo motor or issuing a warning based on a comparison result between the actual mold opening force and the first allowable mold opening force. The mold clamping device according to claim 1 or 2.

4. The controller: After a predetermined timing when the current position of the crosshead moves rearward from the die touch position, switching an object to be compared with the actual mold opening force to a second allowable mold opening force which is smaller than the first allowable mold opening force; The mold clamping device according to any one of claims 1 to 3.

5. The controller: stopping the operation of the servo motor or issuing a warning based on a comparison result between the actual mold opening force and the second allowable mold opening force; The mold clamping device according to claim 4.

6. In the mold opening operation, the crosshead of the toggle link mechanism is moved by the driving force of the servo motor to separate the movable mold from the fixed mold. a mold opening force calculation step of calculating an actual mold opening force based on an actual torque generated in the servo motor and a current position of the crosshead; a mold opening force comparison step of comparing the actual mold opening force calculated in the mold opening force calculation step with a first allowable mold opening force set in advance; A mold opening force monitoring method comprising:

7. a toggle link mechanism having a crosshead for opening / closing and clamping the fixed mold and the movable mold via the fixed platen and the movable platen; A servo motor that is a drive source of the toggle link mechanism; A controller for controlling the operation of the servo motor, The controller: In a mold opening operation in which the movable mold is separated from the fixed mold, comparing an actual mold opening force that is actually generated during the mold opening operation with a first allowable mold opening force that is set in advance; The controller: After a predetermined timing when the current position of the crosshead moves rearward from the die touch position, A mold clamping device, comprising: a mold clamping force detecting unit for detecting a mold opening force that is compared with the actual mold opening force, the mold opening force being switched to a second allowable mold opening force that is smaller than the first allowable mold opening force.

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