Molding device

Abstract

To enable an operator of molding machines assembled with a die clamping apparatus to detect wear degree of a seal member.SOLUTION: A controller 100 of a die clamping apparatus 1 of the present invention determines wear degree of a seal member provided for a piston 16 after elevating a pressure of a working fluid to a set die clamping force and in a die clamping block state of retaining the set die clamping force, based on a decrease level of the pressure of the working fluid in a die clamping side oil chamber 181. The die clamping apparatus 1 can issue an alarm indicating that wear of the seal member such as a piston sealing 21 is noticeable based on the determination.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a mold clamping device. [Background technology]

[0002] A mold clamping device generates a mold clamping force between a pair of molds in an injection molding machine, a die casting machine, etc. As a drive source for the mold clamping device, a hydraulic piston-cylinder mechanism is typically used.

[0003] Patent Document 1 proposes detecting hydraulic oil leakage inside the hydraulic cylinder of this piston-cylinder mechanism. Patent Document 1 detects the hydraulic pressure P1 in the head side chamber and the hydraulic pressure P2 in the rod side chamber of the hydraulic cylinder, and when the difference between the hydraulic pressure P1 and the hydraulic pressure P2 falls below a predetermined set value, it determines that oil leakage has occurred and displays this on a display unit. According to Patent Document 1, the display of this oil leakage makes it possible to recognize that an abnormality, such as damage or wear, has occurred in the piston packing provided on the piston of the hydraulic cylinder. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 61-055405 Summary of the Invention [Problem to be solved by the invention]

[0005] However, for example, it is difficult for an operator who operates an injection molding machine to evaluate the condition of a piston packing from a result of judging that an oil leak has occurred. In other words, since a general operator does not have specialized knowledge of hydraulic actuators, even if an oil leak has occurred in a hydraulic cylinder, he or she cannot judge whether the oil leak is due to normal wear of the packing or whether the wear is so severe that the piston packing needs to be replaced.

[0006] In view of the above, an object of the present invention is to provide a mold clamping device that allows, for example, an operator of a molding machine equipped with the mold clamping device to recognize the degree of wear of a piston packing. [Means for solving the problem]

[0007] The clamping device of the present invention comprises a plurality of tie bars that apply a clamping force between a fixed mold and a movable mold via a fixed platen and a movable platen, a hydraulic actuator provided between the tie bars and the fixed platen, a hydraulic pump that supplies hydraulic oil to the hydraulic actuator, and a control unit that controls the operation of the hydraulic pump. The hydraulic actuator of the present invention includes a mold clamping-side oil chamber to which hydraulic oil is supplied when a mold clamping force is applied, a mold release-side oil chamber to which hydraulic oil is supplied when the mold clamping force is released for mold release, and a piston that separates the mold clamping-side oil chamber from the mold release-side oil chamber. The control unit in the present invention increases the pressure of the hydraulic oil to the set clamping force, and then, in a clamping block state in which the set clamping force is maintained, determines the degree of wear of the sealing member provided on the piston based on the degree of decrease in the pressure of the hydraulic oil in the clamping side oil chamber.

[0008] The degree of pressure drop of the hydraulic oil in the present invention is preferably determined by at least one of the time of pressure drop, the rate of pressure drop, and the frequency of pressure drop. The hydraulic fluid pressure drop time is preferably determined by comparing an actual elapsed time until the detected hydraulic fluid pressure drops to a predetermined reference pressure with the predetermined reference elapsed time. The rate of decrease in the hydraulic oil pressure is preferably determined by comparing an actual rate of decrease in the detected hydraulic oil pressure with a predetermined reference rate of decrease. In addition, the frequency of hydraulic oil pressure drops is preferably determined by comparing the number of actual pressure drops at which the detected hydraulic oil pressure drops to a predetermined reference pressure with the predetermined reference pressure drop number.

[0009] The control unit in the present invention preferably issues an alarm when it determines that the degree of wear has reached a predetermined wear standard.

[0010] In the mold clamping block state of the mold clamping device 1 of the present invention, preferably, when the control unit detects a reduction in the volume of the mold clamping side oil chamber, it can supply hydraulic oil from the hydraulic pump to the mold clamping side oil chamber, and when the detected pump pressure of the hydraulic oil from the hydraulic pump rises to a predetermined set pump pressure, it can stop the supply of hydraulic oil from the hydraulic pump to the mold clamping side oil chamber.

[0011] The control unit is preferably capable of detecting a reduction in the volume of the mold clamping-side oil chamber based on the pressure of the hydraulic oil in the mold clamping-side oil chamber. Further, the control unit can preferably detect the reduction in volume of the mold clamping-side oil chamber based on the amount of movement of at least one of the tie bars and the movable platen toward the retreating side. Effect of the Invention

[0012] According to the mold clamping device of the present invention, wear is judged. Therefore, if an alarm is issued based on this judgment, the operator who receives this alarm can recognize that wear has occurred in the seal member of the mold clamping device that he operates, such as a piston packing, which should be replaced. If the operator replaces the seal member at an appropriate time, such as after a series of injection operations, it is possible to prevent future problems with the mold clamping device caused by wear of the seal member until the alarm is issued. [Brief description of the drawings]

[0013] [Figure 1] 1 is a diagram showing a schematic configuration of a mold clamping device of an injection molding machine according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a block diagram showing a configuration of a hydraulic supply system of the mold clamping device of the present embodiment. [Diagram 3] FIG. 2 is a block diagram showing the configuration of a controller of the mold clamping device of the present embodiment. [Figure 4]1 is a diagram showing a supply form of hydraulic oil by the hydraulic supply system of the present embodiment when a pressure increasing operation for mold clamping is being performed. FIG. [Diagram 5] 11 is a diagram showing a supply form of hydraulic oil by the hydraulic supply system of the present embodiment in the case of a mold clamping block. FIG. [Figure 6] 1 is a flow diagram showing a procedure from a mold clamping block to release of the mold clamping block in the mold clamping device of the present embodiment. FIG. [Figure 7] FIG. 7 is a flow chart showing a specific procedure for determining damage and issuing a warning in FIG. 6. [Figure 8] 7 is a flowchart showing another specific procedure for determining damage and issuing a warning in FIG. 6. [Figure 9] 7 is a flowchart showing another specific procedure for determining damage and issuing a warning in FIG. 6. [Figure 10] 1A and 1B are diagrams showing the hydraulic pressure supply system of this embodiment when an abnormality occurs in which the hydraulic pressure in the mold clamping side oil chamber drops during mold clamping block, in which (a) shows the state before the abnormality occurs, and (b) shows the state after measures have been taken after the abnormality occurs. [Figure 11] 11 is a flow chart showing a specific procedure for performing the operation of the mold clamping device in FIG. [Figure 12] 1A and 1B are diagrams showing the hydraulic pressure supply system of this embodiment when an abnormality occurs in which the hydraulic pressure in the mold clamping side oil chamber rises during mold clamping block, in which (a) shows the state before the abnormality occurs, and (b) shows the state after measures have been taken after the abnormality occurs. [Figure 13] 13 is a flow chart showing a specific procedure for performing the operation of the mold clamping device of FIG. 12. [Figure 14] 1A and 1B are diagrams showing the hydraulic supply system of this embodiment when an abnormality occurs in which the mold clamping side oil chamber shrinks during mold clamping block, in which (a) shows the state before the abnormality occurs, and (b) shows the state after measures have been taken after the abnormality occurs. [Figure 15] FIG. 15 is a flow chart showing a specific procedure for performing the operation of the mold clamping device of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described with reference to the accompanying drawings, taking a mold clamping device 1 of an injection molding machine as an example. The mold clamping device 1 of this embodiment has the following first and second functions. Primary function: Detects wear and tear and issues an alarm. Second function: Determines the reduction in the oil chamber on the mold clamping side and takes appropriate action.

[0015] [Configuration of the mold clamping unit 1: Figure 1] As shown in FIG. 1, the mold clamping device 1 of this embodiment includes a pair of fixed mold 14 and movable mold 15 for obtaining a molded product of a desired shape, an injection barrel 19 that injects molten resin, which is an injection material, into a cavity formed between the fixed mold 14 and the movable mold 15, a mold clamping cylinder 18 that generates a driving force for mold clamping, a hydraulic supply system 30 that supplies hydraulic oil to the mold clamping cylinder 18, and a controller 100 that controls various components.

[0016] As shown in FIG. 1, the mold clamping device 1 has a fixed platen 12 that holds a fixed mold 14 fixed to the upper surface of one end of a base frame 11. A movable platen 13 holding a movable mold 15 is provided on the upper surface of the other end of the base frame 11 so as to be movable forward and backward, facing the fixed platen 12. A guide rail 26 is laid on the base frame 11, and a linear bearing 27 guided by this guide rail 26 supports the movable platen 13 via a slide base 28. Note that a sliding plate may be used instead of the linear bearing 27 to support the movable platen 13 via the slide base 28.

[0017] The fixed platen 12 is provided with clamping cylinders 18, which are one element of a hydraulic actuator with a small stroke and a large cross-sectional area, at its four corners. The clamping cylinders 18 can also be provided on the movable platen 13. The pistons 16 that slide inside the clamping cylinders 18 have one end of tie bars 17 connected to one side of each piston, and when the opposing movable platen 13 approaches to close the mold, these tie bars 17 pass through four insertion holes opened in the four corners of the movable platen 13. The pistons 16 are the other element of the hydraulic actuator. A piston packing 21 is wound around the outer circumferential surface of the pistons 16. A downstream oil supply pipe 55 , which will be described later, is connected to the mold clamping cylinder 18 , and this downstream oil supply pipe 55 supplies hydraulic oil to a mold clamping side oil chamber 181 of the mold clamping cylinder 18 .

[0018] The moving means of the movable platen 13 is constituted by a ball screw shaft 25 installed parallel to the moving direction of the movable platen 13. The ball screw shaft 25 is supported rotatably and axially constrained by a ball screw nut portion 20 held by the movable platen 13 and a bearing housing 23 held by the base frame 11, and is driven by a servo motor 22 via power transmission gears 24A and 24B. The number of rotations and the rotation speed of the ball screw shaft 25 are controlled by a controller 100 via the servo motor 22. Note that the other bearing housing 23 of the ball screw shaft 25 rotatably held by the movable platen 13 with one ball screw nut portion 20 may be held by the fixed platen 12 instead of the base frame 11. In this case, the ball screw nut portion 20 may be held by the fixed platen 12, and the bearing housing 23 may be held by the movable platen 13. A plurality of ring-shaped parallel grooves (or helical screw grooves) with equal pitch are formed on the other end of each tie bar 17. Half nuts 29 that mesh with the ring-shaped parallel grooves of each tie bar 17 are provided on the back surface of the movable platen 13.

[0019] In the above-described mold clamping device 1, the movable platen 13 moves by the rotation of the ball screw shaft 25 driven by the servo motor 22 from a state in which the fixed mold 14 and the movable mold 15 (not shown) are open to a state in which the fixed mold 14 and the movable mold 15 are closed as shown in Fig. 1. The movable platen 13 stops when the opposing surfaces of the fixed mold 14 and the movable mold 15 come into contact with each other.

[0020] When the movable platen 13 stops at this position, the half nuts 29 operate and the inner ring-shaped parallel groove of the half nuts 29 engages with the ring-shaped parallel groove at the tip of the tie bar 17, connecting the tie bar 17 and the half nuts 29. Then, hydraulic oil is supplied to the clamping-side oil chamber 181 of the clamping cylinder 18 to increase the pressure and clamp the mold. After clamping in this manner, molten resin is injected from the injection barrel 19 into the cavity formed by the fixed mold 14 and the movable mold 15 to produce a molded product.

[0021] [Hydraulic supply system 30: Figures 1 and 2] 1 and 2, the hydraulic supply system 30 includes a hydraulic source 40 that discharges hydraulic oil toward the clamping cylinders 18, and a hydraulic oil circuit 50 that is connected to the hydraulic source 40 and delivers the hydraulic oil discharged from the hydraulic source 40 to the clamping cylinders 18. In the hydraulic supply system 30 of this embodiment, as an example, the hydraulic oil circuits 50 are provided corresponding to the respective clamping cylinders 18, and only one hydraulic source 40 is provided common to the multiple hydraulic oil circuits 50. Note that one hydraulic oil circuit 50 may be shared by four clamping cylinders 18. Also, an independent hydraulic source 40 may be provided for each of the four clamping cylinders 18. The operation of the hydraulic source 40 and the hydraulic fluid circuit 50 in the hydraulic supply system 30 is controlled by a controller 100 .

[0022] [Hydraulic source 40: Fig. 1, Fig. 2] The hydraulic power source 40 includes a servo motor 43 and a hydraulic pump 41 that is operated by the rotational drive of the servo motor 43 to discharge hydraulic oil. Although not shown, an encoder that detects the rotational speed and rotational direction is provided in association with the servo motor 43.

[0023] The rotation angle of the servo motor 43 is detected by an encoder, and the detected rotation angle is output to the controller 100. The controller 100 generates a pulse signal corresponding to a command value for the rotation speed of the servo motor 43 and outputs it to the servo motor 43 to rotate the servo motor 43 according to the command value. The rotation angle detected by the encoder of the servo motor 43 is continuously input to the controller 100, and the controller 100 controls the servo motor 43 so as to obtain a rotation speed based on the command value while performing feedback correction based on the rotation angle.

[0024] Here, the servo motor 43 may be of any type as long as it is a motor that can be used to control the position, speed, etc. in a servo mechanism. For example, an AC servo motor, a DC servo motor, a stepping motor, etc. can be applied. As for the structure, for example, the stator structure may be either a distributed winding type or a concentrated winding type, and the rotor structure may be either a surface mounted magnet (SPM) motor or an internally embedded magnet (IPM) motor. As an example, a fixed displacement pump is applied to the hydraulic pump 41.

[0025] [Hydraulic oil circuit 50: Fig. 1, Fig. 2] The hydraulic oil circuit 50 is responsible for the oil supply operation of supplying hydraulic oil discharged from the hydraulic source 40 to the clamping cylinder 18. This operation includes the operation during clamping pressure increase, the clamping block before the injection stroke, and the clamping block during the injection stroke. The hydraulic oil circuit 50 has the following configuration in order to realize the above three mold clamping related times. Since the two hydraulic oil circuits 50 shown in FIG. 1 have the same configuration, the following basically describes only one of the hydraulic oil circuits 50.

[0026] [Upstream oil supply pipe 51, upstream oil drain pipe 53: Figure 1] 1, the hydraulic oil circuit 50 includes an upstream oil supply pipe 51 through which hydraulic oil discharged from the hydraulic pump 41 flows toward the clamping cylinder 18, and an upstream oil drain pipe 53 through which hydraulic oil returned from the clamping cylinder 18 flows toward the tank 49. The upstream oil supply pipe 51 includes an upstream oil supply pipe 51A connecting the hydraulic pump 41 and one of the third switching valves 90, and an upstream oil supply pipe 51B connecting the hydraulic pump 41 and the other of the third switching valves 90. The upstream oil drain pipe 53 includes an upstream oil drain pipe 53A connecting the one of the third switching valves 90 and the tank 49, and an upstream oil drain pipe 53B connecting the other of the third switching valves 90 and the tank 49. In the hydraulic oil circuit 50, the upstream and downstream are based on the direction in which the hydraulic oil flows when the hydraulic pump 41 is rotated forward, with the hydraulic pump 41 being located most upstream.

[0027] [Downstream oil supply pipe 55, downstream oil drain pipe 57: Diagram 1] 1, the hydraulic oil circuit 50 includes a downstream oil supply pipe 55 through which the hydraulic oil flows toward the mold clamping side oil chamber 181, and a downstream oil drain pipe 57 through which the hydraulic oil discharged from the mold release side oil chamber 182 flows. The hydraulic oil circuit 50 includes a pressure sensor 56A that detects the pressure of the hydraulic oil flowing through the downstream oil supply pipe 55. Four types of valves are provided between the upstream oil supply pipe 51 and the upstream oil drain pipe 53 and the downstream oil supply pipe 55 and the downstream oil drain pipe 57. The four types of valves are a logic valve 60, a first switching valve 70, a second switching valve 80, and a third switching valve 90.

[0028] [Logic valve 60: Figure 2, Figure 1] The logic valve 60 allows the hydraulic oil discharged from the hydraulic pump 41 to flow toward the mold clamping-side oil chamber 181 during mold clamping pressure increase, which will be described later. In addition, the logic valve 60 stops the supply of hydraulic oil to the mold clamping-side oil chamber 181 and the discharge of oil from the mold release-side oil chamber 182 during mold clamping block, which will be described later.

[0029] 2, the logic valve 60 includes a valve box 61, a valve element 63 provided inside the valve box 61, and an elastic body 65 that applies an elastic force to the valve element 63 in the upward direction in the figure. The valve box 61 includes, across the valve element 63, a first valve chamber 67 and a second valve chamber 68 that is provided on the opposite side to the first valve chamber 67 and has a pilot port (P port) for driving the valve element 63. The logic valve 60 includes a connecting pipe 69 that communicates with the first switching valve 70.

[0030] The logic valve 60 is constantly subjected to an upward external force by the elastic body 65, and is in a closed state in which no hydraulic oil flows when the valve body 63 is in a position to close the branch pipe 58 as shown in Figure 2. This logic valve 60 is a so-called normally closed type logic valve. On the other hand, in the logic valve 60, when hydraulic pressure is applied to the first valve chamber 67 and an external force in the downward direction in the figure is applied to the elastic body 65 and exceeds the elastic force of the elastic body 65, the valve body 63 moves downward as shown in FIG. 4, and the downstream oil supply pipe 55, branch pipe 58, and upstream oil supply pipe 51A are connected to each other, thereby entering an open state in which hydraulic oil can flow.

[0031] [First switching valve 70: Fig. 2, Fig. 1] The first switching valve 70 switches the flow path of the hydraulic oil required for the operation of the logic valve 60 to the second valve chamber 68 . As shown in Fig. 2, the first switching valve 70 includes a valve body 71 and an electromagnetic solenoid 76 that moves the valve body 71. The first switching valve 70 in Fig. 2 is in a position during mold clamping pressure increase.

[0032] The valve body 71 includes two valve bodies: a first valve body 73 and a second valve body 75 . The second valve body 75 has a flow path through which hydraulic oil flows from the second valve chamber 68 of the logic valve 60. In addition, the first valve body 73 stops the flow of hydraulic oil from the second valve chamber 68 of the logic valve 60. During mold clamping pressure increase, which will be described later, the first valve body 73 is selected (FIG. 4), and during mold clamping block, the second valve body 75 is selected (FIG. 5).

[0033] 2 and 4, when the valve body 71 is in an off state in which the electromagnetic solenoid 76 is not energized, the first valve body 73 is connected to the connecting pipe 69. As a result, the second valve chamber 68 is connected to the upstream oil drain pipe 53A via the first valve body 73 and the connecting pipe 52, and the hydraulic oil inside the second valve chamber 68 is drained to the tank 49 side. In addition, when the valve body 71 is in an on state, for example, with the electromagnetic solenoid 76 energized, as shown in FIG. 5 , the second valve body 75 is connected to the connecting pipe 69, so that the pressure of the mold clamping side oil chamber 181 acts on the second valve chamber 68 and an upward force acts on the valve body 63, closing the branch pipe 58, thereby stopping the discharge of hydraulic oil from the mold clamping side oil chamber 181.

[0034] In response to instructions from the controller 100, the electromagnetic solenoid 76 selectively moves the valve body 71 between a discharge position (FIG. 4) where the hydraulic oil is discharged and a stop position (FIG. 5) where the discharge of the hydraulic oil is stopped.

[0035] [Second switching valve 80: Fig. 2, Fig. 1] Next, the second switching valve 80 switches between a flow path that allows the hydraulic oil from the hydraulic pump 41 to flow toward the logic valve 60 and a flow path that stops the flow. As shown in Fig. 2, the second switching valve 80 includes a valve body 81 and an electromagnetic solenoid 87 that moves the valve body 81. Note that the second switching valve 80 in Fig. 2 is in a position during mold clamping pressure increase.

[0036] The valve body 81 includes two valve bodies: a first valve body 83 and a second valve body 85 . The first valve body 83 has a flow path through which the hydraulic oil from the hydraulic pump 41 flows toward the logic valve 60, and a flow path that stops the flow of the hydraulic oil from the logic valve 60. The second valve body 85 has a flow path that stops the hydraulic oil from the hydraulic pump 41. The first valve body 83 is selected both during mold clamping pressure increase and mold clamping block, which will be described later (FIGS. 3 to 5). Between the first valve body 83 and the electromagnetic solenoid 87, a pilot line PL is laid, which is in communication with the upstream oil supply pipe 51A and the upstream oil drain pipe 53A, respectively.

[0037] [Third switching valve 90: Fig. 2, Fig. 1] Next, the third switching valve 90 switches between a flow path that allows hydraulic oil from the hydraulic pump 41 to flow toward the second switching valve 80 and a flow path that closes communication with the hydraulic source 40. As shown in Fig. 2, the third switching valve 90 includes a valve body 91, and electromagnetic solenoids 96, 97 that move the valve body 91. The third switching valve 90 in Fig. 2 is in a position for mold clamping block.

[0038] The valve body 91 includes three valve bodies: a first valve body 93, a second valve body 94, and a third valve body 95. The first valve body 93 has a flow path through which the hydraulic oil from the hydraulic pump 41 flows toward the second switching valve 80, and a flow path through which the hydraulic oil from the logic valve 60 flows toward the tank 49. The second valve body 94 stops the flow of hydraulic oil from both upstream and downstream. The first valve body 93 is used during mold clamping pressure increase, which will be described later, and the second valve body 94 is selected during mold clamping block (FIGS. 3 to 5).

[0039] [Pipe connection state of the first switching valve 70 to the third switching valve 90: FIG. 1, FIG. 2] 1, the upstream oil supply pipes 51A, 51B are connected to the logic valve 60 via a third switching valve 90 and a second switching valve 80. In addition, the upstream oil drain pipes 53A, 53B are connected to the second switching valve 80 via the third switching valve 90. The downstream oil supply pipe 55 is connected to the first switching valve 70, and is also connected to the logic valve 60 via a branch pipe 58. In addition, the downstream oil drain pipe 57 can be connected to the upstream oil drain pipes 53A, 53B between the second switching valve 80 and the third switching valve 90. A connecting pipe 52 is provided between the first switching valve 70 and the upstream oil drain pipes 53A, 53B.

[0040] [Controller 100: Figure 3] Next, the controller 100 will be described with reference to FIG. The controller 100 comprises an input unit 101 for inputting control setting values, a control unit 103 for generating control commands for the servo motor 43, the logic valve 60, the first switching valve 70, etc., a command output unit 105 for outputting the control commands generated by the control unit 103, and a memory unit 107 in which various data required for generating the control commands is stored.

[0041] The control unit 103 generates a command for forward or reverse rotation of the servo motor 43 and a command for the rotation speed in the forward or reverse rotation. The control unit 103 continuously acquires the detected pressures of the pressure sensors 56A and 56B. The control unit 103 also generates an operation command for the first switching valve 70. That is, the control unit 103 selectively generates an OFF state command for not energizing the electromagnetic solenoid 76 or an ON state command for energizing the electromagnetic solenoid. The control unit 103 also generates similar operation commands for the second switching valve 80 and the third switching valve 90. The above control commands are sent from command output unit 105 to each device.

[0042] The storage unit 107 stores reference information required for determining the degree of wear of a sealing member, for example, the piston packing 21, such as a reference hydraulic oil pressure, a reference pressure drop time, and a reference pressure drop rate. The control unit 103 continuously performs operations such as comparing the pressures detected by the pressure sensors 56A and 56B with the reference pressure values.

[0043] [Operation of hydraulic supply system 30: Figures 4 and 5] Next, the operation of the hydraulic supply system 30 will be described with reference to Figures 4 to 9. In Figures 4 and 5, the pipes indicated by thick lines indicate that hydraulic oil is acting, one arrow indicates the direction of hydraulic oil flow, and both arrows indicate that the pipes are sealed. In Figures 4 and 5, the solenoids that are selected (ON) are filled in black. The same applies to Figures 10, 12, and 14, which will be described later.

[0044] [When clamping and increasing pressure: Figure 4] During mold clamping pressure increase, the hydraulic supply system 30 discharges hydraulic oil by driving the hydraulic pump 41, as shown in Fig. 4. At this time, the first valve body 73 of the first switching valve 70 is selected. As a result, the hydraulic oil that has been retained in the second valve chamber 68 of the logic valve 60 flows to the tank 49 through the first valve body 73 of the first switching valve 70, the connecting pipe 52, and the upstream oil drain pipe 53A (53), so that the hydraulic pressure in the second valve chamber 68 decreases and the force pressing the valve body 63 upward is only the elastic force of the elastic body 65. Since the pressure of the hydraulic oil discharged from the hydraulic pump 41 during mold clamping pressure increase greatly exceeds the elastic force of the elastic body 65, the valve body 63 is pressed downward. As a result, the branch pipe 58 opens, and the hydraulic oil discharged from the hydraulic pump 41 is supplied to the mold clamping-side oil chamber 181 through the first valve body 93 of the third switching valve 90, the first valve body 83 of the second switching valve 80, the first valve chamber 67 of the logic valve 60, and the downstream oil supply pipe 55. The supply of hydraulic oil to the mold clamping-side oil chamber 181 drives the tie bar 17 to the right in the figure. As a result, the movable platen 13 engaged with the tie bar 17 is drawn toward the fixed platen 12, and the fixed mold 14 and the movable mold 15 are pressurized by being clamped via the tie bar 17, and are clamped.

[0045] On the other hand, the hydraulic oil that has accumulated in the mold-release-side oil chamber 182 flows to the tank 49 through the downstream oil drain pipe 57, the first valve body 93 of the third switching valve 90, and the upstream oil drain pipe 53A (53).

[0046] [When clamping: Fig. 5] When the pressure is increased to a predetermined pressure for clamping the mold, the pressure increase is stopped and the mold is placed in a clamping block state. 5, to perform mold clamping block, the hydraulic pump 41 is stopped, and the first switching valve 70 connected to the logic valve 60 via a connecting pipe 69 is switched to the second valve body 75. In addition, the third switching valve 90 connected to the upstream oil supply pipe 51A and the upstream oil drain pipe 53A is switched to the second valve body 94.

[0047] When the hydraulic pump 41 is stopped to stop the supply of hydraulic oil to the mold clamping side oil chamber 181, the downward load acting on the valve body 63 of the logic valve 60 during mold clamping pressure increase is released, and at this time, the first switching valve 70 is switched to the second valve body 75. Therefore, the high-pressure hydraulic oil in the mold clamping side oil chamber 181 flows into the second valve chamber 68 through the second valve body 75, so the valve body 63 moves to the raised position shown in FIG. 5 and the branch pipe 58 is closed. In addition, the downstream oil drain pipe 57 and the upstream oil drain pipe 53A connected to the mold release side oil chamber 182 are blocked by the second valve body 94. This results in a mold clamping block state in which the mold clamping between the fixed mold 14 and the movable mold 15 is maintained. The mold clamping block is released when the molten resin injected into the cavity cools and solidifies, and the mold is opened to remove the molded product, reducing the mold clamping pressure.

[0048] [Overall control procedure: Figure 6] While the mold clamping block is maintained, the mold clamping device 1 of this embodiment realizes the first function and the second function described above. These two functions are performed between the mold clamping block (S1) and the release of the mold clamping block (S7) as shown in FIG. 6. That is, the first function is performed in the step (S3) of determining the damage and issuing an alarm, and the second function is performed in the step (S5) of determining the reduction of the mold clamping oil chamber and taking action. In FIG. 6, the step (first function) of determining the damage and issuing an alarm and the step (second function) of determining the reduction of the mold clamping oil chamber and taking action are performed in parallel, but the first function and the second function may be performed separately one after the other, or each may be performed independently.

[0049] [Control procedure for damage judgment and warning (first function): Figures 7, 8, and 9] Next, referring to FIG. 7 to FIG. 9, a specific example of the step (S3) of damage judgment and warning shown in FIG. 6 will be described. There are three specific examples. In the first example, the damage is judged based on the pressure drop time, in the second example, the damage is judged based on the pressure drop speed, and in the third example, the damage is judged based on the frequency of hydraulic pressure drop in the clamping side oil chamber 181. The first and second procedures are executed by the instruction of the controller 100 during the period from the completion of the clamping block (S1) shown in FIG. 6 to the release of the clamping block (S7). In the third procedure, the number of hydraulic pressure drops counted during the period from the completion of the clamping block (S1) shown in FIG. 6 to the release of the clamping block (S7) is accumulated, and the number of pressure drops during the clamping block relative to a predetermined number of molding cycles or operating time is evaluated to judge the frequency of hydraulic pressure drops. Below, the three procedures will be described in order, and at least one of the means is adopted in the clamping device 1.

[0050] [Damage determination and warning based on pressure drop time: Figure 7] The procedure for damage determination and warning based on pressure drop time (hereinafter, sometimes referred to as the first determination mode) will be described with reference to FIG. In the first determination mode, the procedure begins by starting to measure the elapsed time since the completion of the mold clamping block (FIG. 7, S101). At the same time as the start of the measurement of the elapsed time, detection of the pressure Pr of the hydraulic oil in the mold clamping side oil chamber 181 begins (FIG. 7, S103).

[0051] The controller 100 acquires information regarding the measured time and the detected hydraulic oil pressure (detected hydraulic oil pressure Pr). The controller 100 has a reference hydraulic oil pressure Pc, and compares the acquired detected hydraulic oil pressure Pr with the reference hydraulic oil pressure Pc, specifically, determines whether the detected hydraulic oil pressure Pr drops to the reference hydraulic oil pressure Pc (FIG. 7, S105).

[0052] If the detected hydraulic oil pressure Pr falls to the reference hydraulic oil pressure Pc (FIG. 7, S105, Y), the controller 100 identifies the time from when the measurement of time starts until the detected hydraulic oil pressure Pr falls to the reference hydraulic oil pressure Pc, that is, the actual elapsed time Tr (FIG. 7, S107). If the detected hydraulic oil pressure Pr does not fall to the reference hydraulic oil pressure Pc, the controller 100 continues to detect the detected hydraulic oil pressure Pr and determines whether the detected hydraulic oil pressure Pr falls to the reference hydraulic oil pressure Pc (FIG. 7, S105, N). After identifying the actual elapsed time Tr to be measured, the controller 100 compares the actual elapsed time Tr with the reference elapsed time Tc, specifically, determines whether the actual elapsed time Tr is smaller than the reference elapsed time Tc (FIG. 7, S109).

[0053] If the actual elapsed time Tr is smaller than the reference elapsed time Tc, the controller 100 determines that the wear criterion has been reached (FIG. 7, S111, Y), and then issues an alarm based on the result of the determination (FIG. 7, S113). If the actual elapsed time Tr is not smaller than the reference elapsed time Tc, the wear criterion has not been reached, and the controller 100 determines that the wear criterion is normal and ends the process (FIG. 7, S109, N).

[0054] If the degree of wear of the seal member of the mold clamping cylinder 18, for example the piston packing 21, is large, the time for the pressure of the hydraulic oil to drop due to oil leakage will be shorter. Therefore, if the actual elapsed time Tr is shorter than the reference elapsed time Tc, the controller 100 determines that the wear standard has been reached. The alarm can be displayed as characters via an image display device provided in the mold clamping unit 1, or as sound via a sound generating device provided in the mold clamping unit 1. Since the operator can recognize the alarm before it impedes operation, the operator can systematically replace the piston packing 21 as a sealing member based on the production plan at that time.

[0055] [Damage judgment and warning based on pressure drop rate: Figure 8] Next, the procedure for damage judgment and warning based on the rate of pressure drop (hereinafter, sometimes referred to as the second judgment form) will be described with reference to Fig. 8. Note that in the second judgment form, the procedures common to the first judgment form described with reference to Fig. 7 will be numbered with the same step (S) numbers in Fig. 8 as in Fig. 7, and their explanation may be omitted. The same applies to damage judgment and warning based on the frequency of hydraulic pressure drop, which will be described next to the second judgment form.

[0056] The controller 100 calculates the actual pressure drop rate Vd based on the actual elapsed time Tr (S101) and the detected hydraulic pressure Pr (S103) (FIG. 8, S205). The actual pressure drop rate Vd can be calculated, for example, by the following differential equation (A) of the detected hydraulic pressure Pr and the actual elapsed time Tr. If the wear of the seal member is severe, the actual pressure drop rate Vd can be said to be fast. Vd=dPr / dTr … (A)

[0057] After determining the actual pressure decrease rate Vd, the controller 100 compares the actual pressure decrease rate Vd with a predetermined reference pressure decrease rate Vc, specifically, determines whether the actual pressure decrease rate Vd exceeds the reference pressure decrease rate Vc (FIG. 8, S207). When the controller 100 determines that the actual pressure decrease rate Vd exceeds the reference pressure decrease rate Vc (FIG. 8, S207, Y), it determines that the wear criterion has been reached and issues an alarm based on the result of the determination (FIG. 8, S113). If the actual pressure drop rate Vd does not exceed the reference pressure drop rate Vc (FIG. 8, S207, N), the comparison of the actual pressure drop rate Vd with the reference pressure drop rate Vc is continued (FIG. 8, S101 to S207).

[0058] [Damage judgment and warning based on frequency of hydraulic pressure drop: Figure 9] Next, a procedure for damage judgment and warning based on the frequency of decrease in hydraulic pressure (hereinafter, sometimes referred to as a third judgment mode) will be described with reference to FIG.

[0059] The controller 100 judges whether the detected hydraulic oil pressure Pr has fallen to the reference hydraulic oil pressure Pc or less (FIG. 9, S305). If the controller 100 judges that the detected hydraulic oil pressure Pr has fallen to the reference hydraulic oil pressure Pc or less (FIG. 9, S305, Y), it stores the fact that the pressure has fallen (FIG. 9, S307). This storage is integrated.

[0060] The controller 100 determines whether or not the actual elapsed time Tr has reached the observation time Td (FIG. 9, S311). If the actual elapsed time Tr has reached the observation time Td, the controller 100 then determines whether or not the actual pressure drop count Nr, which is the cumulative number of times that the detected hydraulic oil pressure Pr has dropped to the reference hydraulic oil pressure Pc or less, has reached the reference pressure drop count Nd (FIG. 9, S311). On the other hand, if the actual elapsed time Tr has not reached the observation time Td, the controller 100 continues the procedures of measuring the actual elapsed time Tr (FIG. 9, S101), detecting the detected hydraulic oil pressure Pr (FIG. 9, S103), and determining whether or not the detected hydraulic oil pressure Pr has dropped to the reference hydraulic oil pressure Pc or less (FIG. 9, S305).

[0061] If the accumulated number of actual pressure drops Nr, at which the detected hydraulic oil pressure Pr has dropped to or below the reference hydraulic oil pressure Pc, has reached the reference number of pressure drops Nd (FIG. 9, S311, Y), the controller 100 determines that the wear criterion has been reached (FIG. 7, S111, Y), and then issues an alarm based on the result of the determination (FIG. 7, S113). If the actual pressure drop count Nr has not reached the reference pressure drop count Nd (FIG. 9, S311, N), the controller 100 determines that the wear criterion has not been reached in the observation time Td (FIG. 9, S313). Then, the controller 100 cancels the accumulated actual pressure drop count Nr to zero (FIG. 9, S315), and then continues the procedure of measuring the actual elapsed time Tr again (FIG. 9, S101), detecting the detected hydraulic oil pressure Pr (FIG. 9, S103), and determining whether the detected hydraulic oil pressure Pr has dropped to or below the reference hydraulic oil pressure Pc (FIG. 9, S305). The reference pressure drop count Nd is preferably a predetermined reference frequency (for example, a predetermined number of molding cycles, a predetermined operating time, or a number of occurrences within a predetermined period such as a predetermined year and month). This allows management according to the operating conditions and operating status of the molding machine, such as its operating frequency and operating time, and therefore allows rational management according to the actual conditions on site, such as production plans and maintenance plans.

[0062] Here, the first and third determination modes will be compared. When the first determination form is simply applied, an alarm is issued if the time required for pressure reduction is shorter than the predetermined time even once. However, the pressure of the hydraulic oil may be reduced by some kind of one-off disturbance that is not repetitive and does not actually cause the seal member to wear out and cause an oil leak. For example, this may occur when noise is mixed into the pressure signal. Even in this case, an alarm is issued according to the first determination form. In other words, the first determination form has the advantage of being able to recognize the wear of the seal member sensitively and quickly, but there is a risk of impeding productivity. In contrast, the third determination form eliminates the risk of impeding productivity. Therefore, it is preferable to adopt either the first determination form or the third determination form depending on the factor to be emphasized. This relationship also applies to the relationship between the second determination form and the third determination form.

[0063] [Detection and response to hydraulic oil pressure abnormalities (2nd function): Figure 10, Figure 11, Figure 12, Figure 13, Figure 14, Figure 15] Next, a specific example of a method for detecting and dealing with an abnormality in the pressure of the hydraulic oil in the mold clamping side oil chamber 181 (FIG. 6, S5) performed simultaneously with the step of determining wear and warning (FIG. 6, S3) will be described. There are three specific examples. The first is a method for detecting a decrease in the pressure of the hydraulic oil in the mold clamping side oil chamber 181, the second is a method for detecting an increase in the pressure of the hydraulic oil in the mold clamping side oil chamber 181, and the third is a method for detecting that the position of the tie bar 17 has retreated. All of these methods have in common that the volume of the mold clamping side oil chamber 181 is reduced. These methods are controlled by the controller 100 during the period from the completion of the mold clamping block (S1) shown in FIG. 6 to the release of the mold clamping block (S7). Below, the three methods will be described in order, and at least one of the means is adopted in the mold clamping device 1.

[0064] [Detection of decrease in hydraulic oil pressure: Figure 10, Figure 11] A specific example of a case where a decrease in pressure of hydraulic oil is detected is a leakage of hydraulic oil due to wear of a seal member provided in the mold clamping side oil chamber 181. This occurs during the mold clamping block, and the controller 100 monitors the fluctuation of the pressure of the hydraulic oil. When a decrease in pressure is detected, the controller 100 controls the operation of the hydraulic supply system 30 to correspond to the decrease in pressure. FIG. 10 shows the progress of the hydraulic supply system 30 during this operation, where (a) shows the state of the mold clamping block, and (b) shows the circuit configuration corresponding to the decrease in pressure. In order to shift the circuit configuration from FIG. 10(a) to FIG. 10(b), the control procedure shown in FIG. 11 is performed. In FIG. 10(a), the hydraulic oil from the hydraulic pump 41 is stopped by the third switching valve 90 in which the second valve body 94 is selected. The same applies to FIG. 12 and FIG. 14 described later.

[0065] During the mold clamping block, the pressure Pb of the mold clamping block (hereinafter, the detection block pressure Pb) is continuously detected by the pressure sensor 56A attached to the downstream oil supply pipe 55 of the hydraulic supply system 30 (FIG. 11, S401). This detection block pressure Pb is sent to the controller 100. The controller 100 determines whether the detected block pressure Pb has decreased to the lower limit reference block pressure PB1 (FIG. 11, S403).

[0066] When the controller 100 judges that the detected block pressure Pb has dropped to the lower limit reference block pressure PB1 (FIG. 11, S403, Y), it drives the hydraulic pump 41 (FIG. 11, S405) to discharge hydraulic oil toward the mold clamping side oil chamber 181. The pressure sensor 56B attached to the upstream oil supply pipe 51A detects the pressure (detected pump pressure) Ps of the hydraulic oil supplied by the hydraulic pump 41 (FIG. 11, S407). Information about this detected pump pressure Ps is sent to the controller 100. When the controller 100 acquires the detected pump pressure Ps, it compares it with the set pump pressure PS stored in advance. Specifically, it judges whether the detected pump pressure Ps rises to the set pump pressure PS or not (FIG. 11, S409). This set pump pressure PS corresponds to the pressure of hydraulic oil in the mold clamping side oil chamber 181 required for the mold clamping block. When the controller 100 determines that the detected pump pressure Ps has risen to the set pump pressure PS (FIG. 11, S409, Y), the first valve body 93 is selected in the third switching valve 90, and the first valve body 83 is selected in the second switching valve 80, as shown in FIG. 10(b) when the pressure discharged from the hydraulic pump 41 is increased to the set pump pressure PS (FIG. 11, S411). Therefore, the hydraulic oil discharged from the hydraulic pump 41 flows through the upstream oil supply pipe 51A, the first valve body 93 of the third switching valve 90 provided on the upstream oil supply pipe 51A, and the second valve body 85 of the second switching valve 80 to the first valve chamber 67 of the logic valve 60, as shown in FIG. 10(b). Furthermore, this hydraulic oil passes through the logic valve 60 and is supplied to the mold clamping side oil chamber 181 through the downstream oil supply pipe 55. By increasing the pressure of the hydraulic oil discharged from the hydraulic pump 41 to the set pump pressure PS before driving the second switching valve 80 and the third switching valve 90, it is possible to prevent a momentary drop in hydraulic pressure in the clamping side oil chamber 181 and a shock caused by a sudden pressure change that occurs when the second switching valve 80 and the third switching valve 90 are driven and the clamping side oil chamber 181 is connected to the hydraulic pump 41.

[0067] After that, the controller 100 judges whether or not the internal hydraulic oil pressure Pt of the mold clamping side oil chamber 181 measured by the pressure sensor 56A reaches the set mold clamping pressure PT (FIG. 11, S413). Then, when the internal hydraulic oil pressure Pt reaches the set mold clamping pressure PT (FIG. 11, S413, Y), the state is returned to that of FIG. 10(a), that is, the state in which the first switching valve 70 selects the second valve body 75 and the third switching valve 90 selects the second valve body 94 (FIG. 11, S415), and the operation of the hydraulic pump 41 is stopped again (FIG. 11, S417).

[0068] [Detects increase in hydraulic oil pressure: Figures 12 and 13] Next, a specific example of detecting an increase in hydraulic pressure of the hydraulic oil is when the mold clamping side oil chamber 181 is forcibly compressed during the injection stroke. In this example, the controller 100 also monitors the fluctuation of the hydraulic pressure of the hydraulic oil, and when it detects an increase in pressure, it controls the operation of the hydraulic supply system 30 to respond to the increase in pressure. Figure 12 shows the progress of the hydraulic supply system 30 during this operation, where (a) shows the state of the mold clamping block, and (b) shows the circuit configuration corresponding to the increase in hydraulic pressure. In order to transition the circuit configuration from Figure 12(a) to Figure 12(b), the control procedure shown in Figure 13 is performed. In Figure 12(a), the hydraulic pump 41 is stopped.

[0069] During the injection stroke, the movable platen 13 is pushed back by the injection force, that is, the movable platen 13 moves backward in a direction away from the fixed platen 12. During this backward movement, a tensile force acts on the tie bar 17, so the piston head of the tie bar 17 moves leftward in the figure, and the volume of the mold clamping side oil chamber 181 decreases. However, because the entrance of the mold clamping side oil chamber 181 is closed, the hydraulic oil inside the mold clamping side oil chamber 181 is compressed and the pressure increases. 12 and 13 correspond to Fig. 10 and Fig. 11, respectively, and the same elements as those in Fig. 10 and Fig. 11 are denoted by the same reference numerals in Fig. 12 and Fig. 13. The same applies to Fig. 14 and Fig. 15, which will be described later.

[0070] In the mold clamping block, a detection block pressure Pb is continuously detected by a pressure sensor 56A (FIG. 13, S501). The detection block pressure Pb is sent to the controller 100. Note that, as shown in FIG. 12(a), an injection force IP is generated in the tie bar 17. The controller 100 determines whether the detected block pressure Pb has increased to the upper limit reference block pressure PB2 (FIG. 13, S503).

[0071] When the controller 100 judges that the detected block pressure Pb has risen to the upper limit reference block pressure PB2 (FIG. 13, S503, Y), it drives the hydraulic pump 41 (FIG. 13, S505) to discharge hydraulic oil toward the mold clamping side oil chamber 181. The pressure sensor 56B attached to the upstream oil supply pipe 51A detects the pressure (detected pump pressure) Ps of the hydraulic oil supplied by the hydraulic pump 41 (FIG. 13, S507). Information about this detected pump pressure Ps is sent to the controller 100. When the controller 100 acquires the detected pump pressure Ps, it compares it with the set pump pressure PS stored in advance. Specifically, it judges whether the detected pump pressure Ps rises to the set pump pressure PS or not (FIG. 13, S509). This set pump pressure PS corresponds to the pressure of hydraulic oil in the mold clamping side oil chamber 181 required for the mold clamping block. When the controller 100 determines that the detected pump pressure Ps has risen to the set pump pressure PS (FIG. 13, S509, Y), the first valve body 93 of the third switching valve 90 is selected, and the first valve body 83 of the second switching valve 80 is selected (FIG. 11, S511), as shown in FIG. 11(b) when the pressure discharged from the hydraulic pump 41 has risen to the set pump pressure PS. Therefore, the hydraulic oil discharged from the hydraulic pump 41 attempts to flow through the upstream oil supply pipe 51A, the first valve body 93 of the third switching valve 90 provided on the upstream oil supply pipe 51A, and the second valve body 85 of the second switching valve 80 to the first valve chamber 67 of the logic valve 60, as shown in FIG. 10(b). Furthermore, this hydraulic oil passes through the logic valve 60 and attempts to be supplied to the mold clamping side oil chamber 181 through the downstream oil supply pipe 55. However, because the pressure of the hydraulic oil in the mold clamping-side oil chamber 181 is higher than the pressure of the hydraulic oil discharged from the hydraulic pump 41, the hydraulic oil in the mold clamping-side oil chamber 181 flows back toward the hydraulic pump 41. Therefore, as shown in Fig. 12(b), the hydraulic oil flows in the opposite direction to that in Fig. 10(b), so the hydraulic pump 41 sucks the hydraulic oil from the mold clamping-side oil chamber 181. Therefore, the hydraulic pump 41 is rotated in the opposite direction to when the hydraulic oil is supplied to the mold clamping-side oil chamber 181.By increasing the pressure discharged from the hydraulic pump 41 to the set pump pressure PS before driving the second switching valve 80 and the third switching valve 90, it is possible to prevent a momentary drop in hydraulic pressure in the clamping side oil chamber 181 and a shock caused by a sudden pressure change that occurs when the second switching valve 80 and the third switching valve 90 are driven and the clamping side oil chamber 181 is connected to the hydraulic pump 41.

[0072] After that, the controller 100 judges whether or not the internal hydraulic oil pressure Pt of the mold clamping side oil chamber 181 measured by the pressure sensor 56A reaches the set mold clamping pressure PT (FIG. 13, S513). When the internal hydraulic oil pressure Pt reaches the set mold clamping pressure PT (FIG. 13, S513, Y), the state is returned to that of FIG. 12(a), that is, the state in which the first switching valve 70 selects the second valve body 75 and the third switching valve 90 selects the second valve body 94 (FIG. 13, S515), and the operation of the hydraulic pump 41 is stopped again (FIG. 13, S517).

[0073] In the actual machine, in order to increase the force with which the tie bars are held in position, not only the mold clamping side oil chamber but also the mold release side oil chamber 182 is blocked (sealed). However, in order to avoid the following risks, the line of the mold release side oil chamber 182 may be connected to the tank 49. If the mold release side oil chamber 182 is sealed, the volume of the mold release side oil chamber 182 will expand when the tie bar retracts due to a pressure drop in the hydraulic oil in the mold clamping side oil chamber 181 and when the tie bar retracts due to the injection force. However, because the mold release side oil chamber 182 is sealed, the hydraulic oil cannot be sucked in as the volume expands. In this case, the pressure in the mold release side oil chamber 182 drops from the tank pressure (normal pressure) at the time of pressurization, and there is a risk of air bubbles being generated in the hydraulic oil. Air bubbles generated by decompression may shrink and become invisible to the naked eye even if they are repressurized, but may remain. The risk of these air bubbles remaining is particularly high when performing repeated operations such as injection molding.

[0074] [Detection of retraction of the tie bar position: Figures 14 and 15] Next, a specific example of detecting the retreat of the position of the tie bars 17 will be described. When oil leakage occurs in the mold clamping side oil chamber 181, the hydraulic pressure of the hydraulic oil inside the mold clamping side oil chamber 181 drops, and as a result, the movable platen 13, which was pulled in (moved forward) by the set mold clamping force, moves back because the clamping force decreases due to the drop in the hydraulic oil pressure. As a result, the tie bar 17 connected to the movable platen 13 also moves back, and the volume of the mold clamping side oil chamber 181 decreases. This volume reduction occurs during the mold clamping block, and the controller 100 monitors the positional fluctuation of the tie bar 17, and when it detects that the position of the tie bar 17 has moved back beyond a predetermined position set in advance, it controls the operation of the hydraulic supply system 30 so as to correspond to the reduction in the volume of the mold clamping side oil chamber 181. FIG. 14 shows the progress of the hydraulic supply system 30 during this operation, where (a) shows the state of the mold clamping block, and (b) shows the circuit configuration corresponding to the retreat of the tie bar 17, that is, the reduction in the volume of the mold clamping side oil chamber 181. In order to transition the circuit configuration from Fig. 14(a) to Fig. 14(b), the control procedure shown in Fig. 15 is performed. In order to execute this procedure, a position sensor 31 that detects the position of the tie bar 17 is provided, as shown in Fig. 14(a).

[0075] During the mold clamping block, the position sensor 31 continuously detects the position of the tie bar 17 (FIG. 15, S601). This detected position (hereinafter, referred to as the detected tie bar position Sr) is sent to the controller 100. The controller 100 determines whether the detected tie bar position Sr has retreated to a predetermined reference tie bar position Sc (FIG. 15, S603).

[0076] When the controller 100 judges that the detection tie bar position Sr has retreated to the reference block pressure PB (FIG. 15, S603, Y), it drives the hydraulic pump 41 (FIG. 15, S505) to discharge hydraulic oil toward the mold clamping side oil chamber 181. The pressure sensor 56B attached to the upstream oil supply pipe 51A detects the pressure (detected pump pressure) Ps of the hydraulic oil supplied by the hydraulic pump 41 (FIG. 15, S607). Information about this detected pump pressure Ps is sent to the controller 100. When the controller 100 acquires the detected pump pressure Ps, it compares it with the set pump pressure PS stored in advance. Specifically, it judges whether the detected pump pressure Ps rises to the set pump pressure PS or not (FIG. 15, S609). This set pump pressure PS corresponds to the pressure of hydraulic oil in the mold clamping side oil chamber 181 required for the mold clamping block. When the controller 100 determines that the detected pump pressure Ps has risen to the set pump pressure PS (FIG. 15, S609, Y), the first valve body 93 of the third switching valve 90 is selected, and the second valve body 85 of the second switching valve 80 is selected (FIG. 15, S613), as shown in FIG. 14(b). Therefore, the hydraulic oil discharged from the hydraulic pump 41 flows through the upstream oil supply pipe 51 (51A), the first valve body 93 of the third switching valve 90 provided on the upstream oil supply pipe 51 (51A), and the first valve body 83 of the second switching valve 80 to the first valve chamber 67 of the logic valve 60, as shown in FIG. 14(b). Furthermore, this hydraulic oil passes through the logic valve 60 and is supplied to the mold clamping side oil chamber 181 through the downstream oil supply pipe 55.

[0077] When the tie bar retreats during the injection stroke, the pressure of the hydraulic oil in the mold clamping side oil chamber 181 may rise excessively as described above. In this case, the hydraulic oil discharged from the hydraulic pump 41 does not flow to the mold clamping side oil chamber 181 side, but flows back from the mold clamping side oil chamber 181 side to the hydraulic pump 41 side. By increasing the pressure of the hydraulic oil discharged from the hydraulic pump 41 to the set pump pressure PS before driving the second switching valve 80 and the third switching valve 90, it is possible to prevent a momentary drop in hydraulic pressure in the mold clamping side oil chamber 181 and a shock caused by a sudden pressure change caused by connecting the mold clamping side oil chamber 181 to the hydraulic pump 41 by driving the second switching valve 80 and the third switching valve 90.

[0078] Thereafter, when the hydraulic pressure in the mold clamping side oil chamber 181 reaches the set pump pressure PS as detected by the pressure sensor 56A, the state is returned to that of FIG. 14(a) and the operation of the hydraulic pump 41 is stopped again (FIG. 15, S511). After that, the controller 100 judges whether or not the internal hydraulic oil pressure Pt of the mold clamping side oil chamber 181 measured by the pressure sensor 56A reaches the set mold clamping pressure PT (FIG. 15, S613). When the internal hydraulic oil pressure Pt reaches the set mold clamping pressure PT (FIG. 15, S613, Y), the state is returned to that of FIG. 14(a), that is, the state in which the first switching valve 70 selects the second valve body 75 and the third switching valve 90 selects the second valve body 94 (FIG. 15, S615), and the operation of the hydraulic pump 41 is stopped again (FIG. 15, S617).

[0079] [effect] The effects of the first function and the second function of this embodiment will be described below. [Effects of the first function] The mold clamping unit 1 judges the wear and issues an alarm. Therefore, an operator who receives this alarm can recognize that the seal member of the mold clamping unit 1 that he or she operates, for example, the piston packing 21, has worn out and should be replaced. If the operator replaces the seal member at an appropriate timing, such as after a series of injection operations, it is possible to prevent future troubles in the mold clamping unit 1 due to wear of the seal member until the alarm is issued.

[0080] [Effects of the second function] The mold clamping device 1, in the mold clamping block state, judges the reduction of the mold clamping side oil chamber 181 and executes a corresponding measure. Therefore, by executing this measure, even if an abnormality in the pressure of the hydraulic oil occurs in the mold clamping side oil chamber 181, the abnormality is eliminated and the subsequent injection molding operation can be continued.

[0081] The above describes a preferred embodiment of the present invention. However, in addition to the above, it is possible to select and / or change the configurations described in the above embodiment to other configurations as appropriate without departing from the spirit of the present invention.

[0082] In the above embodiment, when a predetermined wear standard is reached, an alarm is issued to prompt maintenance inspection or replacement of the sealing member of the mold clamping cylinder. However, in addition to issuing an alarm, the present invention can also perform the following processing (1) or (2). (1): Issues an "insufficient clamping force" alarm to prompt the operator to increase the clamping force or change the injection conditions to reduce the pressure in the cavity. (2): In addition to (1), a recommended mold clamping force is calculated based on the detected movement amount of the tie bars 17 and displayed on the display panel of the controller 100. Alternatively, the set mold clamping force is automatically changed to the recommended mold clamping force.

[0083] Furthermore, in the present invention, when a plurality of mold clamping cylinders 18 are provided, if at least one of the mold clamping cylinders 18 reaches the wear criterion, the hydraulic valves blocking the mold clamping-side oil chambers 181 of all the plurality of mold clamping cylinders 18 can be opened to communicate the mold clamping-side oil chambers 181 of all the mold clamping cylinders 18. This makes it possible to equalize the pressure of the hydraulic oil in all the plurality of mold clamping-side oil chambers 181 and return them to the set mold clamping pressure.

[0084] In the above case, the clamping hydraulic pressures of the multiple clamping cylinders 18 can be controlled independently with different pressures. As a result, even if biased clamping forces are set to the multiple clamping cylinders 18 with different hydraulic pressures to accommodate cavities of biased sizes, the effects of the first function and the second function can be obtained in each of the multiple clamping cylinders 18.

[0085] In the mold clamping device 1, the tie bar 17 moves only a small distance relative to the piston packing 21 during mold clamping pressure increase, so the lubricating oil at the sliding portion between the piston packing 21 and the tie bar 17 becomes insufficient, and the piston packing 21 becomes susceptible to wear. Therefore, in order to prevent wear, it is preferable to move the tie bar 17 by a large stroke before starting or after the operation of the mold clamping device 1 is finished, so that the surface area of ​​the tie bar 17 that was in contact with the lubricating oil passes through the sliding portion, and a lubricating oil film is formed at the sliding portion. [Explanation of symbols]

[0086] 1 Mold clamping device 11 Base frame 12 Fixed plate 13 Movable plate 14 Fixed mold 15 Movable mold 16 Piston 17 Tie bar 18 Clamping cylinder 19 Ejection Barrel 20 Ball screw nut 21 Piston packing 22 Servo motor 23 Bearing box 24A, 24B Power transmission gear 25 Ball screw shaft 26 Guide rail 27 Linear Bearing 28 Slide stand 29 Half Nut 30 Hydraulic Supply System 31 Position Sensor 40 Hydraulic source 41 Hydraulic pump 43 Servo motor 49 Tank 50 Hydraulic oil circuit 51, 51A, 51B Upstream oil supply pipe 52 Connecting pipe 53,53A,53B Upstream oil drain pipe 55 Downstream fuel supply pipe 56A, 56B Pressure Sensor 57 Downstream oil drain pipe 58 Branch Pipe 59 Tank 60 Logic Valve 61 Valve box 63 Valve body 65 Elastic Body 67 1st valve chamber 68 2nd valve chamber 69 Connecting Pipe 70 First switching valve 71 Valve body 73 First valve body 75 Second valve body 76 Electromagnetic Solenoid 80 Second switching valve 81 Valve body 83 First valve body 85 Second valve body 87 Electromagnetic Solenoid 90 Third switching valve 91 Valve body 93 First valve body 94 Second valve body 95 Third valve body 96 Electromagnetic Solenoid 100 Controller 101 Input section 103 Control section 105 Command output section 107 Storage section 181 Clamping side oil chamber 182 Oil chamber on mold release side Nd Number of reference pressure drops Nr Actual pressure drop count Pb detection block pressure PB1 Lower reference block pressure PB2 Upper reference block pressure Ps Detected pump pressure PS Set pump pressure Pr Detected hydraulic oil pressure Pc Reference hydraulic pressure Pt Internal hydraulic pressure PT Mold clamping pressure setting Sr Detected tie bar position Sc Reference tie bar position Tc Reference elapsed time Td Observation time Tr Actual elapsed time Tc Reference elapsed time Vd Actual pressure drop rate Vc Reference pressure drop rate

Claims

1. a plurality of tie bars for applying a clamping force between the fixed mold and the movable mold via the fixed platen and the movable platen; a hydraulic actuator provided between the tie bar and the fixed platen; a hydraulic pump for supplying hydraulic oil to the hydraulic actuator; A control unit for controlling the operation of the hydraulic pump, The hydraulic actuator includes: a mold clamping side oil chamber to which hydraulic oil is supplied when the mold clamping force is applied; a mold release side oil chamber to which hydraulic oil is supplied when the mold clamping force is released and the mold is released; a piston that separates the mold clamping side oil chamber from the mold release side oil chamber, The control unit is After increasing the pressure of the hydraulic oil to a set mold clamping force, in a mold clamping block state in which the set mold clamping force is maintained, determining a degree of wear of a seal member provided on the piston based on a degree of decrease in pressure of the hydraulic oil in the mold clamping side oil chamber; A mold clamping device characterized by:

2. The degree of pressure drop of the hydraulic oil is The pressure drop is determined by at least one of a time period during which the pressure drops, a rate at which the pressure drops, and a frequency at which the pressure drops. The mold clamping device according to claim 1 .

3. The pressure drop time of the hydraulic oil is The determination is made by comparing an actual elapsed time until the detected pressure of the hydraulic oil decreases to a predetermined reference pressure with a predetermined reference elapsed time. The mold clamping device according to claim 2.

4. The rate of pressure decrease is The actual decrease rate of the detected pressure of the hydraulic oil is determined by comparing the actual decrease rate with a predetermined reference decrease rate. The mold clamping device according to claim 2.

5. The frequency of the pressure reduction is The determination is made by comparing the actual pressure drop count at which the detected pressure of the hydraulic oil drops to a predetermined reference pressure with the predetermined reference pressure drop count. The mold clamping device according to claim 2.

6. The control unit is issuing an alarm when it is determined that the degree of wear has reached a predetermined wear standard; The mold clamping device according to any one of claims 1 to 5.

7. In the mold clamping block state, The control unit is When a reduction in the volume of the mold clamping side oil chamber is detected, The hydraulic oil is supplied from the hydraulic pump toward the mold clamping side oil chamber, When the detected pump pressure of the hydraulic oil from the hydraulic pump rises to a predetermined set pump pressure, The supply of the hydraulic oil from the hydraulic pump to the mold clamping side oil chamber is stopped. The mold clamping device according to any one of claims 1 to 6.

8. The control unit is detecting a reduction in the volume of the mold clamping-side oil chamber based on a pressure of the hydraulic oil in the mold clamping-side oil chamber; The mold clamping device according to claim 7.

9. The control unit is detecting a reduction in the volume of the mold clamping side oil chamber based on a movement amount of at least one of the tie bars and the movable platen toward a retreat side; The mold clamping device according to claim 7.

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