JP2010082680A - Mold clamping apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold clamping apparatus which can reduce the flow rate of a hydraulic liquid to be supplied to a mold clamping cylinder. <P>SOLUTION: A piston 8 stowed in the mold clamping cylinder 9 has a large-diameter piston section 70 which divides a large-diameter cylinder chamber 67 into a first cylinder chamber 67a and a second cylinder chamber 67b, and a small-diameter piston section 71 which can slide in a small-diameter cylinder chamber 68. The end 7c of a tie bar blocks the opening 68c of the small-diameter cylinder chamber 68. A hydraulic circuit 76 is designed so as to connect or disconnect the first cylinder chamber 67a and second cylinder chamber 67b, connect or disconnect the first cylinder chamber 67a and small-diameter cylinder chamber 68, change over the supply destination of the hydraulic liquid from the hydraulic pressure source between the first cylinder chamber 67a and small-diameter cylinder chamber 68, and allow or disallow the discharge of the hydraulic liquid from the second cylinder chamber 67b and small-diameter cylinder chamber 68 to a tank 86. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a mold clamping device applied to a die casting machine or the like.

There is known a mold clamping device that supplies hydraulic oil to a hydraulic cylinder for mold clamping that accommodates a piston provided on a tie bar and generates a mold clamping force (for example, Patent Document 1). FIG. 7 shows a mold clamping cylinder 9 disclosed in Patent Document 1 and a hydraulic circuit 176 that supplies hydraulic oil to the mold clamping cylinder 9. The mold clamping cylinder 9 has a large diameter cylinder chamber 67 and a small diameter cylinder chamber 68. The hydraulic circuit 176 includes a fifth direction control valve 183 that connects or blocks the first cylinder chamber 67 a of the large diameter cylinder chamber 67 and the second cylinder chamber 67 b of the large diameter cylinder chamber 67. The technology of Patent Document 1 supplies the hydraulic fluid discharged from one of the first cylinder chamber 67a and the second cylinder chamber 67b to the other as the piston 8 moves by opening the fifth direction control valve 183. Can do. As a result, the technique of Patent Document 1 can obtain a large mold clamping force by closing the fifth direction control valve 183, while the fifth direction control valve 183 can obtain a driving force other than the mold clamping force. It is possible to reduce the flow rate of the hydraulic fluid supplied to the mold clamping cylinder 9 by opening. Details of the configuration and operation of the technique of Patent Document 1 will be described later.
JP 2007-167897 A

  As described in detail later, the technique of Patent Document 1 has a relatively large flow rate of hydraulic fluid when the piston 8 is moved in the mold clamping direction in order to obtain a driving force other than the mold clamping force.

  The objective of this invention is providing the mold clamping apparatus which can reduce the flow volume of the hydraulic fluid supplied to a mold clamping cylinder.

  A mold clamping apparatus according to a first aspect of the present invention includes a fixed die plate that holds a fixed mold, a movable die plate that holds a movable mold and is movable in a mold opening / closing direction with respect to the fixed die plate, A coupled portion for coupling to either the fixed die plate or the movable die plate, and a piston for generating a mold clamping force housed in the other of the fixed die plate or the movable die plate; And a tie bar provided on the one of the fixed die plate and the movable die plate, and a coupling portion that can be coupled to or released from the coupled portion, and the other of the stationary die plate and the movable die plate. A clamping cylinder that accommodates the piston, a hydraulic pressure source that supplies hydraulic fluid of a predetermined pressure to the clamping cylinder, and a discharge from the clamping cylinder. And a hydraulic pressure circuit that controls the flow of hydraulic fluid between the tank and the mold clamping cylinder, and the mold clamping cylinder has a large-diameter cylinder chamber. And a small-diameter cylinder chamber that communicates with the opposite side of the large-diameter cylinder chamber to the die plate-facing surface, and has a smaller diameter than the large-diameter cylinder chamber, and the piston in the large-diameter cylinder chamber A large-diameter piston portion that is slidable and divides the large-diameter cylinder chamber into a first cylinder chamber opposite to the small-diameter cylinder chamber and a second cylinder chamber on the small-diameter cylinder chamber side; A small-diameter piston portion that protrudes from the end surface of the small-diameter cylinder chamber side of the large-diameter piston portion, and is slidable in the small-diameter cylinder chamber. Protruding, A first rod portion having a diameter smaller than that of the small-diameter piston portion and closing an opening opening on the die plate facing surface side of the first cylinder chamber, and a side opposite to the die plate facing surface side of the small diameter piston portion A second rod portion projecting from an end surface of the small-diameter cylinder and having a diameter larger than that of the first rod portion and closing an opening portion on the opposite side to the die plate facing surface side of the small-diameter cylinder chamber, The pressure circuit can connect or disconnect the first cylinder chamber and the second cylinder chamber, can connect or disconnect the first cylinder chamber and the small-diameter cylinder chamber, and supplies hydraulic fluid from the hydraulic pressure source. Can be switched between the first cylinder chamber and the small-diameter cylinder chamber, and the discharge of hydraulic fluid from the second cylinder chamber and the small-diameter cylinder chamber to the tank can be allowed or prohibited.

  Preferably, the hydraulic circuit includes a first flow path connected to the first cylinder chamber, a second flow path connected to the second cylinder chamber, and a third flow path connected to the small diameter cylinder chamber. A flow path, a first communication flow path connecting the first flow path and the second flow path, a second communication flow path connecting the second flow path and the third flow path, The third flow path and the tank while connecting the first valve that opens and closes the first communication flow path, the second valve that opens and closes the second communication flow path, and the first flow path and the hydraulic pressure source. Or a third valve that is switched to connect the third flow path and the hydraulic pressure source while connecting the first flow path and the tank, and the third flow path, A fourth valve that opens and closes on a side closer to the third valve than a connection position between the third flow path and the second communication flow path.

  Preferably, when the coupled portion and the coupling portion are not coupled, the first cylinder chamber is connected to the second cylinder chamber and the small-diameter cylinder chamber, and the second cylinder chamber and the Supplying hydraulic fluid to the first cylinder chamber in a state in which discharge of the hydraulic fluid from the small-diameter cylinder chamber to the tank is prohibited, connecting the first cylinder chamber and the second cylinder chamber, and The hydraulic fluid is selectively supplied to the small-diameter cylinder chamber in a state where one cylinder chamber and the small-diameter cylinder chamber are shut off, and the tie bar is placed at a position where the coupled portion and the coupling portion can be coupled. When the coupled portion and the coupling portion are coupled, the first cylinder chamber, the second cylinder chamber, and the small-diameter cylinder chamber are shut off, and the second cylinder chamber and the small-diameter are separated. Cylinder chamber While permitting the discharge of a working fluid to al the tank, so as to perform mold clamping by supplying hydraulic fluid to said first cylinder chamber, having a control device which controls the coupling unit and the hydraulic circuit.

  Preferably, the apparatus has a moving mechanism for moving the movable die plate in the mold opening / closing direction, and the control device connects the first cylinder chamber and the second cylinder chamber after the solidification of the molding material, and With the cylinder chamber and the small-diameter cylinder chamber shut off, hydraulic fluid is supplied to the small-diameter cylinder chamber to move the movable die plate in the mold opening direction, thereby separating the fixed mold and the movable mold. After the separation, the coupled portion and the coupled portion are released, and after the release, the moving die plate is further moved in the mold opening direction by the moving mechanism, and the mold contact in the next cycle is performed after the release. By the time, the moving mechanism, the coupling part, and the hydraulic circuit are controlled so that the tie bar is moved to a position where the coupled part and the coupling part can be coupled in a mold contact state.

  Preferably, the control device causes the tie bar to reach the connectable position in the next cycle before mold closing in the next cycle, and the position of the tie bar and the position in the next cycle that are generated after the arrival. The tie bar is moved during mold closing in the next cycle so as to eliminate a deviation from the position where the coupling is possible.

  A mold clamping apparatus according to a second aspect of the present invention includes a fixed die plate that holds a fixed mold, a movable die plate that holds a movable mold and is movable in a mold opening / closing direction with respect to the fixed die plate, A piston that generates a clamping force for clamping the stationary mold and the movable mold, a clamping cylinder that houses the piston, a hydraulic pressure source that supplies hydraulic fluid of a predetermined pressure to the clamping cylinder, A tank for storing hydraulic fluid discharged from the clamping cylinder; and a hydraulic circuit for controlling a flow of hydraulic fluid between the hydraulic pressure source, the tank and the clamping cylinder, and the clamping cylinder Is connected to the large-diameter cylinder chamber to which hydraulic fluid is supplied when the movable die plate is moved in the mold clamping direction, and has a smaller diameter than the large-diameter cylinder chamber. Plate opening direction A small-diameter cylinder chamber to which hydraulic fluid is supplied when moved, and the piston is slidable in the large-diameter cylinder chamber, and the large-diameter cylinder chamber is opposite to the small-diameter cylinder chamber. A large-diameter piston portion that is divided into a first cylinder chamber and a second cylinder chamber on the small-diameter cylinder chamber side, and projects from the end surface of the large-diameter piston portion on the small-diameter cylinder chamber side, and slides on the small-diameter cylinder chamber A small-diameter piston portion, and a rod portion that closes an opening portion of the small-diameter cylinder chamber that opens to the opposite side of the small-diameter cylinder chamber from the end surface on the small-diameter cylinder chamber side of the small-diameter piston portion And the pressure receiving area on the first cylinder chamber side of the large diameter piston portion is the pressure receiving area on the second cylinder chamber side of the large diameter piston portion and the pressure receiving area on the small diameter cylinder chamber side of the small diameter piston portion. The hydraulic circuit can connect or disconnect the first cylinder chamber and the second cylinder chamber, can connect or disconnect the first cylinder chamber and the small-diameter cylinder chamber, The supply destination of the hydraulic fluid from the pressure source can be switched between the first cylinder chamber and the small diameter cylinder chamber, and the discharge of the hydraulic fluid from the second cylinder chamber and the small diameter cylinder chamber to the tank is permitted or prohibited. Possible, configured.

  According to the present invention, the flow rate of hydraulic fluid supplied to the mold clamping cylinder can be reduced.

  FIG. 1 is a front view including a cross-sectional view of a part of the configuration of a mechanical part of a mold clamping device 1 according to an embodiment of the present invention, showing a state before mold thickness adjustment. FIG. 2 is a view of the mold clamping device 1 of FIG. 1 as viewed from above. FIG. 3 is a front view including a cross-sectional view of a part of the configuration of the mechanical part of the mold clamping device 1, and shows a state where the molten metal ML is injected after the mold clamping is completed.

  The mold clamping apparatus 1 according to the present embodiment is applied to, for example, a die casting machine. The mold clamping apparatus 1 is configured as a so-called composite mold clamping apparatus, and includes a moving mechanism 40 mainly used for mold opening and closing and a mold clamping cylinder 9 mainly used for mold clamping. The mold clamping device 1 includes a fixed die plate 3, a movable die plate 4, a tie bar 7, and a half nut 20.

The fixed die plate 3 is fixed on the base 2. The fixed die plate 3 holds the fixed mold 5 on the front side.
The moving die plate 4 holds the moving mold 6 on the front surface (side facing the fixed die plate 3). The moving die plate 4 is provided on the base 2 so as to be movable in the mold opening direction A1 and the mold closing direction A2. Specifically, as shown in FIGS. 1 and 3, a sliding plate 11 fixed on the base 2 and a sliding plate fixed below the movable die plate 4 and slidable with respect to the sliding plate 11. Since the slider is constituted by the moving plate 12, the movable die plate 4 is supported with respect to the base 2 so as to be movable. The moving die plate 4 is formed with a through hole 4h into which the tie bar 7 is inserted. For example, the through holes 4 h are formed at the four corners of the movable die plate 4.
By closing the pair of molds of the fixed mold 5 and the movable mold 6, a cavity is formed between the recess 5 a (FIG. 1) of the fixed mold 5 and the recess 6 a (FIG. 1) of the movable mold 6. C (FIG. 3) is formed.

  A sleeve 60 is provided on the back surface of the fixed die plate 3. The sleeve 60 is fitted with a plunger tip 61 (FIGS. 1 and 3). The plunger tip 61 is connected to the tip of the plunger rod 62. As shown in FIGS. 1 and 3, the plunger rod 62 is connected to the piston rod 64 of the injection cylinder 65 through a coupling 63. The injection cylinder 65 is driven by hydraulic pressure to move the piston rod 64 forward and backward.

As shown in FIG. 3, the piston rod 64 is advanced in a state where the molten metal ML is supplied to the sleeve 60 through the supply port 60a, thereby forming between the clamped fixed mold 5 and the movable mold 6. The molten metal ML as a molding material is injected and filled in the cavity C to be formed.
In addition, an injection apparatus is comprised including each part 60-65. Further, a die casting machine (molding machine) is configured including the mold clamping device 1 and the injection device.

  The tie bar 7 is supported horizontally by the fixed die plate 3. A coupled portion 7a is formed at the free end of the tie bar 7 on the moving die plate 4 side. For example, the coupled portion 7 a is formed by arranging a plurality of ring-shaped groove portions extending in the circumferential direction on the outer periphery of the tie bar 7 in the axial direction of the tie bar 7. The groove portion may be formed in a spiral shape. In the middle of the tie bar 7, a piston 8 built in the mold clamping cylinder 9 is provided.

  The mold clamping cylinder 9 is formed inside the fixed die plate 3, and a piston 8 is incorporated in the fixed die plate 3 so as to be movable. By supplying high-pressure hydraulic oil to the cylinder chamber of the mold clamping cylinder 9, a force acts between the fixed die plate 3 and the tie bar 7, and the tie bar 7 is driven with respect to the fixed die plate 3. The tie bar 7 is movable with respect to the fixed die plate 3 within a movable range of the piston 8 connected to the tie bar 7, that is, within a stroke range of the mold clamping cylinder 9.

  The moving mechanism 40 is built in the base 2 and includes a screw shaft 41, a support member 42, a servo motor 43, and a movable member 44. The support member 42 is fixed to the base 2 and rotatably supports one end portion of the screw shaft 41. The other end of the screw shaft 41 is connected to a servo motor 43 fixed to the base 2. The screw shaft 41 is screwed into the movable member 44. The movable member 44 is fixed to both sides of the movable die plate 4 as shown in FIG.

  In the moving mechanism 40, by controlling the rotation of the servo motor 43, the screw shaft 41 rotates, and the rotation of the screw shaft 41 is converted into a linear motion of the movable member 44. As a result, the movable die plate 4 is driven in the mold opening direction A1 or the mold closing direction A2. The position of the movable die plate 4 is specified by detecting the position of the movable member 44 with the encoder 45 of the servo motor 43.

  The half nut 20 is disposed behind the through hole 4 h of the movable die plate 4. The half nut 20 is formed with a protrusion (see FIG. 5) that engages with the coupled portion 7a of the tie bar 7. In other words, the coupled portion 7a and the half nut 20 are formed in a saw blade shape and mesh with each other.

  The half nut 20 is opened and closed by a half nut opening / closing cylinder 21 (FIG. 2). When the half nut 20 is closed and meshed (coupled) with the coupled portion 7a of the tie bar 7, the tie bar 7 and the movable die plate 4 are coupled. When the half nut 20 is opened, the connection between the tie bar 7 and the movable die plate 4 is released.

  FIG. 4 is an enlarged view of the mold clamping cylinder 9. The mold clamping cylinder 9 has a large diameter cylinder chamber 67 and a small diameter cylinder chamber 68. The small-diameter cylinder chamber 68 communicates with the large-diameter cylinder chamber 67 on the side opposite to the die plate facing surface side (clamping direction side) and has a smaller diameter than the large-diameter cylinder chamber 67.

  The piston 8 has a large-diameter piston portion 70 that can slide in the large-diameter cylinder chamber 67 and a small-diameter piston portion 71 that can slide in the small-diameter cylinder chamber 68. Each of the large-diameter piston portion 70 and the small-diameter piston portion 71 is formed in a columnar shape, for example. The large-diameter piston portion 70 divides the large-diameter cylinder chamber 67 into a first cylinder chamber 67a on the side opposite to the small-diameter cylinder chamber 68 (on the mold opening direction side) and a second cylinder chamber 67b on the small-diameter cylinder chamber 68 side. is doing. The small diameter piston portion 71 protrudes from the end surface of the large diameter piston portion 70 on the small diameter cylinder chamber 68 side. The diameter D2 of the small diameter piston portion 71 is smaller than the diameter D1 of the large diameter piston portion 70. The small-diameter piston portion 71 can slide in the small-diameter cylinder chamber in a state where the communication portion between the large-diameter cylinder chamber 67 and the small-diameter cylinder chamber 68 is closed.

  The tie bar 7 has a tie bar main body 7b that protrudes from the end surface on the die plate facing surface side of the large-diameter piston portion 70 and closes the opening 67c that opens on the die plate facing surface side of the first cylinder chamber 67a. The tie bar main body 7b can slide on the opening 67c in a state where the opening 67c is closed. The diameter of the tie bar body 7b is determined by the clamping force. Further, the diameter D4 of the tie bar main body 7b is smaller than the diameter D2 of the small diameter piston portion 71. Therefore, the pressure receiving area on the first cylinder chamber 67a side of the large diameter piston portion 70 is larger than the pressure receiving area on the second cylinder chamber 67b side.

  Further, the tie bar 7 protrudes from the end surface of the small diameter piston portion 71 on the small diameter cylinder chamber 68 side, has a smaller diameter than the small diameter piston portion 71, and is in the mold clamping direction side of the small diameter cylinder chamber 68 (opposite to the large diameter cylinder chamber). A tie bar end 7c for closing the opening 68c. The tie bar end 7c can slide on the opening 68c in a state where the opening 68c is closed. The diameter D3 of the tie bar end 7c is larger than the diameter D4 of the tie bar body 7b. Therefore, the pressure receiving area on the first cylinder chamber 67a side of the large diameter piston portion 70 is the pressure receiving area on the second cylinder chamber 67b side of the large diameter piston portion 70 and the pressure receiving area on the small diameter cylinder chamber 68 side of the small diameter piston portion 71. Greater than sum.

  The hydraulic cylinder 75 is supplied with hydraulic oil to the mold clamping cylinder 9. The hydraulic pressure source 75 includes an electric pump, for example, and supplies hydraulic oil having a predetermined pressure. The mold clamping cylinder 9 can discharge hydraulic oil to the tank 86. The flow of hydraulic oil among the hydraulic source 75, the tank 86 and the mold clamping cylinder 9 is controlled by a hydraulic circuit 76.

  The hydraulic circuit 76 has a flow path for supplying hydraulic oil to each of the three cylinder chambers (67a, 67b, and 68) or discharging hydraulic oil from each of the three cylinder chambers (67a, 67b, and 68). is doing. Specifically, the first flow path 78 communicating with the first cylinder chamber 67a, the second flow path 79 communicating with the second cylinder chamber 67b, and the third flow path 80 communicating with the small diameter cylinder chamber 68 are provided. is doing.

  The hydraulic circuit 76 has a flow path for supplying hydraulic fluid discharged from one or two cylinder chambers to another cylinder chamber as the piston 8 moves between the three cylinder chambers. Specifically, the hydraulic circuit 76 includes a first communication channel 81 that communicates the first channel 78 and the second channel 79, and a second channel that communicates the second channel 79 and the third channel 80. And a communication channel 82.

  The hydraulic circuit 76 has a valve for allowing or prohibiting the flow of hydraulic fluid between the three cylinder chambers as described above. Specifically, the hydraulic circuit 76 includes a first direction control valve 83 that opens and closes the first communication flow path 81, and a second direction control valve 84 that opens and closes the second communication flow path 82. The first direction control valve 83 is switched between the closed position P101 and the open position P102. The second direction control valve 84 is switched between the closed position P103 and the open position P104. The 1st direction control valve 83 and the 2nd direction control valve 84 are comprised by the non-leak valve which can suppress the leak of hydraulic fluid in the closed position P101 or the closed position P103, for example.

  As described above, in the hydraulic circuit 76, a run-around circuit (differential circuit) is configured with respect to the first cylinder chamber 67a and the second cylinder chamber 67b, and also with respect to the first cylinder chamber 67a and the small diameter cylinder chamber 68. Also, a run-around circuit is configured.

  The hydraulic circuit 76 includes a third direction control valve 85 that switches the supply destination of the hydraulic oil from the hydraulic source 75 between the first cylinder chamber 67 a and the small diameter cylinder chamber 68. The third direction control valve 85 connects the hydraulic pressure source 75 and the first flow path 78 and connects the third flow path 80 and the tank 86 at the position P105. The third direction control valve 85 connects the hydraulic pressure source 75 and the third flow path 80 and also connects the first flow path 78 and the tank 86 at the position P106. The third direction control valve 85 shuts off both the hydraulic source 75 and the tank 86 and both the first flow path 78 and the third flow path 80 at the position P107.

  The hydraulic circuit 76 has a valve for permitting or prohibiting the discharge of the hydraulic fluid from the second cylinder chamber 67 b and the small diameter cylinder chamber 68 to the tank 86. Specifically, the hydraulic circuit 76 includes a fourth direction control valve 87 that opens and closes the third flow path 80 on the tank 86 side of the connection point between the third flow path 80 and the second communication flow path 82. Yes. The fourth direction control valve 87 is switched between the closed position P108 and the open position P109.

  In addition to this, the hydraulic circuit is provided with a pressure control valve or the like for setting the hydraulic oil from the hydraulic source 75 to a constant set pressure, but the illustration is omitted.

  FIG. 5 is a block diagram illustrating a configuration of a signal processing system related to driving of the tie bar 7 of the mold clamping device 1. FIG. 5 shows one tie bar 7, but the same applies to the other tie bars 7. In FIG. 5, the hydraulic circuit 76 is schematically shown.

  The mold clamping device 1 includes a control device 90 that controls operations of the moving mechanism 40, the hydraulic circuit 76, the half nut 20, and the like based on signals from various sensors and the like. The various sensors are, for example, an encoder 45, a position sensor 88 that detects the position of the tie bar 7, a pressure sensor 89 that detects the pressure in the cylinder chamber of the clamping cylinder 9, and a proximity switch 95 that detects the position of the coupled portion 7a. .

  The position sensor 88, for example, constitutes an optical or magnetic linear scale together with the scale portion 91 provided at the tie bar end portion 7c. The linear scale may be an absolute type or an incremental type.

  For example, the pressure sensor is provided so as to be able to detect the pressures of the three cylinder chambers (67a, 67b, and 68). However, in FIG. 5, only the pressure sensor 89 for detecting the pressure in the first cylinder chamber 67a is shown for convenience of illustration.

  The proximity switch 95 is provided on the back side of the half nut 20. The proximity switch 95 is a sensor that outputs a signal according to a change in the distance to the object. For example, the proximity switch 95 outputs an ON signal when the object approaches within a predetermined range. The proximity switch may output an ON signal when the object is separated from a predetermined range. The proximity switch 95 can be configured by an appropriate type of sensor such as a photoelectric sensor, a laser sensor, a magnetic sensor, or an ultrasonic sensor.

  The proximity switch 95 is fixed to the movable die plate 4 and provided with the outer peripheral surface side of the tie bar 7 as a detection direction. Accordingly, as the tie bar 7 moves in the axial direction, the distance between the detection surface of the proximity switch 95 and the outer peripheral surface of the tie bar 7 changes by the depth of the groove portion of the coupled portion 7a. For example, the proximity switch 95 does not output a signal when facing the groove portion of the coupled portion 7a (when separated from the tie bar 7), and when facing the protruding portion between the groove portions of the coupled portion 7a (tie bar). On signal is output when the signal is close to 7).

  The control device 90 includes a main control unit 91, a mold thickness adjustment unit 92, and a mold information setting unit 93. The function of the control device 90 is configured by hardware such as a processor and necessary software.

  The mold information setting unit 93 acquires and holds mold information related to the fixed mold 5 and the movable mold 6. The mold information is acquired when an operator inputs data to a control panel (not shown) or when the control device 90 reads data via a storage medium or a network. The mold information includes, for example, a mold thickness.

  The mold thickness adjusting unit 92 outputs information necessary for mold thickness adjustment to the main control unit 91 based on the output signals of the encoder 45 and the proximity switch 95 and the mold information held by the mold information setting unit 93. For example, the mold thickness adjusting unit 92 is based on the mold thickness held by the mold information setting unit 93 and the position of the tie bar 7 where the coupled portion 7a and the half nut 20 can be engaged when the mold contacts ( For example, the movement amount A) from the drive limit of the piston 8 is calculated, and the calculation result is output.

  The main control unit 91 performs various processes for comprehensively controlling the mold clamping device 1. For example, at the time of mold thickness adjustment, various direction control valves of the hydraulic circuit 76 are controlled based on signals from the mold thickness adjusting unit 92, the encoder 45, the position sensor 88, the pressure sensor 89, and the like. At the time of mold clamping, various direction switching valves of the hydraulic circuit 76 are controlled based on signals from the mold information setting unit 93 and the pressure sensor 89 and the like.

  FIG. 6 is a flowchart for explaining the outline of the operation of the mold clamping apparatus 1. In step S1, a mold closing step is performed in which the movable die plate 4 is moved from the mold opening position shown in FIG. 1 to the mold closing position shown in FIG. In the mold closing process, a drive signal is output from the control device 90 to the servo motor 43, and the moving die plate 4 is moved in the mold closing direction by the moving mechanism 40. The control device 90 specifies the position and speed of the moving die plate 4 based on the detection value of the encoder 45, and controls the position and speed of the moving die plate 4 based on the specifying result.

  In step S2, the fixed mold 5 and the moving mold 6 are in contact with each other. That is, mold contact is performed. The control device 90 can detect the mold contact based on the detection value of the encoder 45.

  In step S3, the half nut 20 is closed by the half nut opening / closing cylinder 21, and the half nut 20 and the coupled portion 7a mesh.

  In step S <b> 4, a control signal is output from the control device 90 to the hydraulic circuit 76, and the mold clamping is performed by the mold clamping cylinder 9. The operation of the hydraulic circuit 76 at this time will be described later. For example, the control device 90 determines whether or not the target mold clamping force has been obtained by specifying the extension amount of the tie bar 7 after the mold clamping is started based on the detection result of the position sensor 88. Then, hydraulic oil is supplied to the mold clamping cylinder 9 until a target mold clamping force is obtained.

  When the target mold clamping force is obtained, the injection cylinder 65 is driven while the target mold clamping force is maintained, and the molten metal is supplied to the cavity (step S5). Thereafter, when a condition determined by the control device 90 that the molten metal has solidified is satisfied, for example, a predetermined time elapses, the mold clamping cylinder 9 is depressurized. Further, an initial operation for mold opening is performed (step S6). That is, a control signal is output from the control device 90 to the hydraulic circuit 76, and the movable die plate 4 is moved a little in the mold opening direction by the mold clamping cylinder 9. Thereby, the fixed mold 5 and the movable mold 6 are separated from each other, and the molded product is separated from one of the fixed mold 5 and the movable mold 6. The operation of the hydraulic circuit 76 at this time will be described later.

  In step S7, the coupling between the half nut 20 and the coupled portion 7a is released. In step S8, a mold opening process for moving the movable die plate 4 to the mold opening position is performed. In the mold opening process, a drive signal is output from the control device 90 to the servo motor 43, and the moving die plate 4 is moved in the mold opening direction by the moving mechanism 40. Then, the movable die plate 4 reaches the mold opening position (mold opening limit). The control device 90 can detect that the movable die plate 4 has reached the mold opening position based on the detection value of the encoder 45. The molded product molded in the cavity C is extruded from the fixed mold 5 or the movable mold 6 by an unillustrated extrusion device after completion of mold opening or in parallel with mold opening.

  Before the half nut 20 and the coupled portion 7a are closed (step S3), the axial position of the tie bar 7 needs to be adjusted to a position where they can be coupled to each other. That is, it is necessary to eliminate the positional shift less than the pitch of the coupling groove between the protruding portion of the half nut 20 and the coupling groove of the coupled portion 7a.

  Therefore, the mold clamping device 1 is arranged in the axial direction of the tie bar 7 between the half nut 20 and the coupled portion 7a for the half nut coupling (step S3) in the next cycle in parallel with the mold opening process of step S8. Position adjustment is performed (step S10).

  Specifically, the main control unit 91 of the control device 90 determines that the position of the tie bar 7 is calculated and held in advance by the mold thickness adjusting unit 92 so that the half nut 20 and the coupled portion 7a can be coupled. The position of the tie bar 7 is controlled so as to reach. This position control is performed by outputting a control signal from the control device 90 to the hydraulic circuit 76 and moving the tie bar 7 in the mold opening direction or the mold clamping direction (mold closing direction) by the mold clamping cylinder 9. This position control is performed by feedback control based on the detection value of the position sensor 88. The operation of the hydraulic circuit 76 at this time will be described later. For example, the tie bar 7 reaches a position where the half nut 20 and the coupled portion 7a can be engaged before the mold opening process is completed. The control device 90 can confirm that the tie bar 7 has reached the connectable position based on the detection value of the proximity switch 95.

  Thereafter, during steps S2 and S3 in the next cycle, in the mold clamping cylinder 9, the position of the tie bar 7 is engaged with the half nut 20 and the coupled portion 7a due to various factors such as leakage of hydraulic oil. It may deviate from possible positions. Therefore, the mold clamping device 1 corrects the tie bar position in parallel with the mold opening in step S1 (step S9). This control is, for example, the same control as step S10.

  Note that the tie bar position correction control in step S9 is preferably performed continuously until the mold contact or until the half nut 20 and the coupled portion 7a are engaged. The control of the tie bar position correction may be started when a predetermined process of the molding cycle is started, such as when the mold opening is started. The control of the tie bar position correction is started when a positional deviation is detected, such as when a positional deviation is detected by the proximity switch 95 or when the deviation amount based on the detection value of the position sensor 88 exceeds a predetermined value. May be. The adjustment of the tie bar position in step S10 may be ended when the tie bar 7 reaches the connectable position, may be continued until a predetermined time such as completion of mold opening, or is continued until step S2 or S3. (Steps S10 and S9 may be made identical.)

  The operation of the hydraulic circuit 76 will be described. In steps S6, S9, and S10, the tie bar 7 is moved by the driving force generated in the mold clamping cylinder 9. However, this driving force may be smaller than the driving force at the time of mold clamping in step S4. Therefore, in order to reduce the flow rate of hydraulic oil in other processes (steps S6, S9, and S10) while obtaining a large driving force at the time of mold clamping in step S4, the operation of the hydraulic circuit 76 is as follows. To be controlled.

  In the mold clamping process of step S4, the hydraulic circuit 76 is controlled as follows. The first direction control valve 83 shown in FIG. 4 is set to the closed position P101. The second direction control valve 84 is set to the open position P104. The third direction control valve 85 is set to the position P105. The fourth direction control valve 87 is set to the open position P109.

  Accordingly, the hydraulic oil from the hydraulic source 75 is supplied to the first cylinder chamber 67a. The pressure in the second cylinder chamber 67b and the small diameter cylinder chamber 68 is a tank pressure. The first cylinder chamber 67a, the second cylinder chamber 67b, and the small diameter cylinder chamber 68 are blocked. That is, the run-around circuit is turned off.

Then, assuming that the pressure difference between the pressure supplied to the first cylinder chamber 67a and the tank pressure is P1, the number of tie bars is n, and the tank pressure is sufficiently smaller than the pressure difference P1, the mold clamping force W1 is
W1 = π / 4 × (D1 ² −D4 ² ) × P1 × n (1)
It becomes.

  As shown in FIG. 4, in the tie bar 7 (piston 8), a mold clamping force is obtained according to the difference between the diameter D4 of the smallest diameter tie bar body 7b and the diameter D1 of the largest diameter large piston part 70. Therefore, a large clamping force can be obtained.

  The diameter D4 of the tie bar body 7b is determined by the required mold clamping force. The diameter D1 of the large-diameter piston portion 70 is determined by the required mold clamping force, the diameter D4, and the pressure difference P1. In other words, the diameter D1 is determined by the clamping force if the pressure difference P1 is constant.

  In the mold opening initial operation process in step S6, the tie bar position correction process in step S9, and the tie bar position adjustment process in step S10, when a force in the mold clamping direction is applied to the piston 8, the hydraulic circuit 76 is as follows. Be controlled. The first direction control valve 83 is set to the open position P102. The second direction control valve 84 is set to the open position P104. The third direction control valve 85 is set to the position P105. The fourth direction control valve 87 is set to the closed position P108.

  Accordingly, the hydraulic oil from the hydraulic source 75 is supplied to the first cylinder chamber 67a. The second cylinder chamber 67b and the small diameter cylinder chamber 68 are connected to the first cylinder chamber 67a and are disconnected from the tank 86. That is, the run-around circuit is turned on.

  Since the first cylinder chamber 67a, the second cylinder chamber 67b, and the small diameter cylinder chamber 68 are in communication with each other, they have the same pressure. However, the pressure receiving area on the first cylinder chamber 67a side of the large diameter piston portion 70 is the pressure receiving area on the second cylinder chamber 67b side of the large diameter piston portion 70 and the pressure receiving area on the small diameter cylinder chamber 68 side of the small diameter piston portion 71. Since it is larger than the sum, a force in the mold clamping direction is applied to the piston 8. When the piston 8 moves in the mold clamping direction, the hydraulic fluid discharged from the second cylinder chamber 67b and the small diameter cylinder chamber 68 enters the first cylinder chamber 67a via the first communication channel 81 and the second communication channel 82. Refluxed.

The required flow rate Q1 at this time is expressed as follows, where the required speed of the clamping cylinder 9 is v (mm / s):
Q1 = π / 4 × (D3 ² −D4 ² ) × v × n (2)
It becomes. If the same control as that at the time of mold clamping is performed, the required flow rate is (D1 ² -D4 ² ) instead of (D3 ² -D4 ² ) in equation (2). Therefore, it is understood that the required flow rate Q1 is reduced by the run-around circuit.

  In the mold opening initial operation process in step S6, the tie bar position correcting process in step S9, and the tie bar position adjusting process in step S10, when a force in the mold opening direction is applied to the piston 8, the hydraulic circuit 76 is as follows. Be controlled. The first direction control valve 83 is set to the open position P102. The second direction control valve 84 is set to the closed position P103. The third direction control valve 85 is set to the position P106. The fourth direction control valve 87 is set to the open position P109.

  Accordingly, the hydraulic oil from the hydraulic source 75 is supplied to the small diameter cylinder chamber 68. The pressure in the first cylinder chamber 67a and the second cylinder chamber 67b is a tank pressure. Accordingly, the mold opening force is generated by the hydraulic oil supplied to the small diameter cylinder chamber 68. Further, when the piston 8 moves in the mold opening direction, the hydraulic oil discharged from the first cylinder chamber 67 a is returned to the second cylinder chamber 67 b via the first communication channel 81.

The mold opening force W2 at this time is
W2 = π / 4 × (D2 ² −D3 ² ) × P1 × n (3)
It becomes. The required flow rate Q2 in the mold opening direction is
Q2 = π / 4 × (D2 ² −D3 ² ) × v × n (4)
It becomes.

  Therefore, if the diameter D2 is a value close to the diameter D3, the required flow rate Q2 can be made small. The ratio between the diameter D2 and the diameter D3 affects the mold opening force W2. In general, the mold opening force is preferably a mold clamping force / 10 or more. Therefore, it is preferable to set the diameters D2 and D3 so that the mold opening force W2 falls within this range.

  When the tie bar 7 is stopped after the tie bar position adjustment in step S10 and before the tie bar position correction in step S9 is started, the control device 90 causes each cylinder chamber (67a, 67b and 68) to stop. The hydraulic circuit 76 is controlled so that hydraulic fluid does not flow in and out. For example, the first to fourth directional control valves (83 to 85 and 87) are set to the closed positions (P101, P103, P107, P108).

  For comparison with the present embodiment, the operation of the prior art shown in FIG. 7 will be described. In the technique shown in FIG. 7, the mold clamping force, the mold opening force, and the required flow rate in the mold opening direction are the same as the mold clamping force W1, the mold opening force W2, and the required flow rate Q2 in the mold opening direction of this embodiment.

  In the prior art shown in FIG. 7, when a driving force in the mold clamping direction is generated for adjusting the position of the tie bar 7, the hydraulic circuit 176 is controlled as follows. The fifth direction control valve 183 is set to the open position P202. The sixth direction control valve 185 is set to the position P205. The seventh direction control valve 187 is set to the closed position P208.

  Accordingly, the hydraulic oil from the hydraulic source 75 is supplied to the first cylinder chamber 67a. The second cylinder chamber 67b is connected to the first cylinder chamber 67a. The small diameter cylinder chamber 68 has a tank pressure.

  Since the first cylinder chamber 67a and the second cylinder chamber 67b communicate with each other, they have the same pressure. However, since the pressure receiving area on the first cylinder chamber 67a side of the large diameter piston portion 70 is larger than the pressure receiving area on the second cylinder chamber 67b side of the large diameter piston portion 70, the piston 8 has the pressure receiving direction in the mold clamping direction. Power is granted. When the piston 8 moves in the mold clamping direction, the hydraulic oil discharged from the second cylinder chamber 67b is returned to the first cylinder chamber 67a via the communication channel 181.

The required flow rate Q3 at this time is
Q3 = π / 4 × (D2 ² −D4 ² ) × v × n (5)
It becomes.

  Taking the 800 ton class clamping cylinder as an example, the prior art of FIG. 7 is compared with this embodiment.

  It is assumed that D1 = 440 mm, D2 = 275 mm, D3 = 240 mm, and D4 = 200 mm. Further, P1 = 16.5 MPa, and the operation speed v of the mold clamping cylinder is 10 mm / s for both mold clamping and mold opening.

The mold clamping force W1, the mold opening force W2, and the necessary flow rate Q2 are the same in both of the present embodiment and the prior art of FIG. 7, and from the formulas (1), (3), and (4), become.
W1 = π / 4 × (440 ² −200 ² ) × 16.5 / 9.8 / 1000 × 4
= 812tonf
W2 = π / 4 × (275 ² −240 ² ) × 16.5 / 9.8 / 1000 × 4
= 95.3tonf
Q2 = π / 4 × (275 ² −240 ² ) × 10 × 60/1000000 × 4
= 34L / min

  Since 95.3> = 812/10 = 81.2, the condition of mold opening force> = clamping force / 10 is satisfied.

The required flow rate Q1 in the present embodiment is obtained from the equation (2):
Q1 = π / 4 × (240 ² −200 ² ) × 10 × 60/1000000 × 4
= 33L / min
It becomes.

On the other hand, the required flow rate Q3 in the prior art shown in FIG.
Q3 = π / 4 × (275 ² −200 ² ) × 10 × 60/1000000 × 4
= 67L / min
It becomes.

  Therefore, according to the present embodiment, the required flow rate in the mold clamping direction can be reduced to about ½ compared to the prior art shown in FIG.

  As described above, according to the mold clamping device 1 of the present embodiment, the hydraulic circuit 76 is configured to fit the mold clamping cylinder 9 having a special shape. That is, not only the second cylinder chamber 67b but also the small-diameter cylinder chamber 68 is connected to the first cylinder chamber 67a by a run-around circuit. As a result, the hydraulic fluid discharged from the small diameter cylinder chamber 68 can be returned to the first cylinder chamber 67a to reduce the required flow rate.

  After the initial mold opening operation (step S6), the controller 90 tie-bars to a position where the coupled portion 7a and the half nut 20 can be coupled in a state where the mold is in contact by the mold contact in the next cycle (step S2). 7 is moved. Therefore, the half nut 20 and the coupled portion 7a can be coupled immediately after the mold contact, and the molding cycle can be shortened. Furthermore, by adjusting the position from the previous cycle, the required speed v in the mold clamping cylinder 9 can be reduced, and the load on the hydraulic circuit 76 can be reduced.

  The control device 90 causes the tie bar 7 to reach a position where the half nut 20 and the coupled portion 7a in the next cycle can be coupled by the start of mold closing in the next cycle (step S10). Then, the tie bar 7 is moved during mold closing in the next cycle so as to eliminate the deviation between the position of the tie bar 7 and the connectable position in the next cycle, which occurs after the arrival (step S9). Therefore, it is possible to appropriately perform the coupling by eliminating the position shift of the tie bar due to the leakage of hydraulic oil and the like while preparing for the coupling with a margin before the mold contact.

In the above embodiment, the half nut 20 is an example of the coupling portion of the present invention, the hydraulic source 75 is an example of the hydraulic pressure source of the present invention, and the hydraulic circuit 76 is an example of the hydraulic circuit of the present invention. The tie bar body 7b is an example of the first rod portion of the present invention, the tie bar end portion 7c is an example of the second rod portion of the present invention, and the first directional control valve 83 is the first valve portion of the present invention. The second direction control valve 84 is an example of the second valve of the present invention, the third direction control valve 85 is an example of the third valve of the present invention, and the fourth direction control valve 87 is the present. It is an example of the 4th valve of invention.

  The present invention is not limited to the above-described embodiments, and may be implemented in various aspects.

  The molding machine to which the mold clamping apparatus and the mold clamping method of the present invention are applied is not limited to a die casting machine. The molding machine includes a metal molding machine, a plastic injection molding machine, and a molding machine such as wood powder. An example of a molding machine for wood powder includes a machine for molding a material in which a thermoplastic resin is mixed with wood powder.

  The mold clamping device is not limited to a composite type or a direct pressure type. For example, the mold clamping device may be a toggle type. In other words, the mold clamping cylinder is not limited to one that is provided on the die plate and accommodates the piston provided on the tie bar.

  When the cylinder that accommodates the piston provided on the tie bar is provided on the die plate, the cylinder may be provided on the moving die plate. The hydraulic fluid is not limited to hydraulic oil. For example, water may be used.

  The hydraulic circuit may be changed as appropriate. The hydraulic circuit for obtaining the mold clamping force W1, the mold opening force W2, and the required flow rates Q1 and Q2 described in the embodiment can be variously configured. In other words, the first cylinder chamber and the second cylinder chamber can be connected or disconnected, the first cylinder chamber and the small-diameter cylinder chamber can be connected or disconnected, and the supply destination of the hydraulic fluid from the hydraulic pressure source is the first cylinder chamber. The hydraulic circuit that can be switched between the small-diameter cylinder chamber and the second cylinder chamber and the small-diameter cylinder chamber can permit or prohibit the discharge of the hydraulic fluid to the tank can be variously configured. Each of the first to fourth valves may be constituted by one valve or a plurality of valves. When the first to fourth valves are constituted by a plurality of valves, some of them may be shared with each other.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view partially including a cross-sectional view illustrating a configuration of a machine part of a mold clamping device according to an embodiment of the present invention. The figure which looked at the mold clamping apparatus of FIG. 1 from upper direction. The figure which shows the state at the time of the mold clamping completion of the mold clamping apparatus of FIG. The figure which shows the structure of the mold clamping cylinder of the mold clamping apparatus of FIG. The block diagram which shows the structure of the signal processing system which concerns on the drive of the tie bar of the mold clamping apparatus of FIG. The flowchart which shows the outline of operation | movement of the mold clamping apparatus of FIG. The figure which shows the structure of the conventional hydraulic circuit.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Mold clamping apparatus, 3 ... Fixed die plate, 4 ... Moving die plate, 5 ... Fixed mold, 6 ... Moving mold, 7 ... Tie bar, 7a ... Joined part, 7b ... Tie bar main body (1st rod part) 7c ... tie bar end (second rod part), 8 ... piston, 20 ... half nut (joint part), 9 ... clamping cylinder, 67 ... large diameter cylinder chamber, 67a ... first cylinder chamber, 67b ... first 2-cylinder chamber, 68 ... small-diameter cylinder chamber, 70 ... large-diameter piston part, 71 ... small-diameter piston part, 76 ... hydraulic circuit (hydraulic pressure circuit), 83 ... first direction control valve (first valve), 84 ... first Two-way control valve (second valve), 85... Third direction control valve (third valve), 87... Fourth direction control valve (fourth valve), 90.

Claims (6)

A fixed die plate for holding a fixed mold;
A movable die plate that holds a movable mold and is movable in a mold opening and closing direction with respect to the fixed die plate;
A coupled portion for coupling to either the fixed die plate or the movable die plate, and a piston for generating a mold clamping force housed in the other of the fixed die plate or the movable die plate; A tie bar with
The one of the fixed die plate or the movable die plate, and a coupling part that can be coupled to or released from the coupled part;
A mold clamping cylinder provided on the other of the fixed die plate or the movable die plate and containing the piston;
A hydraulic pressure source for supplying hydraulic fluid of a predetermined pressure to the mold clamping cylinder;
A tank for storing the hydraulic fluid discharged from the mold clamping cylinder;
A hydraulic circuit for controlling the flow of hydraulic fluid between the hydraulic pressure source, the tank and the clamping cylinder;
Have
The mold clamping cylinder is
A large-diameter cylinder chamber;
A small-diameter cylinder chamber that communicates with the opposite side of the large-diameter cylinder chamber on the side opposite to the die plate, and has a smaller diameter than the large-diameter cylinder chamber;
Have
The piston is
The large diameter cylinder chamber is slidable in the large diameter cylinder chamber and divides the large diameter cylinder chamber into a first cylinder chamber opposite to the small diameter cylinder chamber and a second cylinder chamber on the small diameter cylinder chamber side. A piston part;
A small-diameter piston portion projecting from the end surface of the large-diameter piston portion on the small-diameter cylinder chamber side, and capable of sliding the small-diameter cylinder chamber;
Have
The tie bar is
A first rod portion that protrudes from an end surface of the large-diameter piston portion on the die plate facing surface side, has a smaller diameter than the small-diameter piston portion, and closes an opening opening on the die plate facing surface side of the first cylinder chamber. When,
An opening that protrudes from the end surface opposite to the die plate facing surface side of the small diameter piston portion, has a larger diameter than the first rod portion, and opens to the opposite side of the small diameter cylinder chamber to the die plate facing surface side. A second rod portion for closing;
Have
The hydraulic circuit is
The first cylinder chamber and the second cylinder chamber can be connected or disconnected,
The first cylinder chamber and the small diameter cylinder chamber can be connected or disconnected,
The supply destination of hydraulic fluid from the hydraulic pressure source can be switched between the first cylinder chamber and the small diameter cylinder chamber.
The discharge of hydraulic fluid from the second cylinder chamber and the small diameter cylinder chamber to the tank can be allowed or prohibited,
Clamping device is composed of. The hydraulic circuit is
A first flow path connected to the first cylinder chamber;
A second flow path connected to the second cylinder chamber;
A third flow path connected to the small diameter cylinder chamber;
A first communication channel connecting the first channel and the second channel;
A second communication channel connecting the second channel and the third channel;
A first valve that opens and closes the first communication channel;
A second valve for opening and closing the second communication channel;
The third flow path and the tank are connected while the first flow path and the hydraulic pressure source are connected, or the third flow path and the tank are connected with the first flow path and the tank. A third valve that is switched to connect to a hydraulic pressure source;
A fourth valve that opens and closes the third flow path on the third valve side with respect to a connection position between the third flow path and the second communication flow path;
The mold clamping device according to claim 1, comprising: When the coupled portion and the coupling portion are not coupled,
The first cylinder chamber is connected to the second cylinder chamber and the small-diameter cylinder chamber, and the first cylinder chamber is in a state in which the discharge of hydraulic fluid from the second cylinder chamber and the small-diameter cylinder chamber to the tank is prohibited. Supply of hydraulic fluid to the cylinder chamber, and
Supplying hydraulic fluid to the small-diameter cylinder chamber in a state where the first cylinder chamber and the second cylinder chamber are connected and the first cylinder chamber and the small-diameter cylinder chamber are shut off;
Selectively moving the tie bar to a position where the coupled portion and the coupling portion can be coupled,
When the coupled portion and the coupling portion are coupled, the first cylinder chamber, the second cylinder chamber, and the small-diameter cylinder chamber are blocked, and the second cylinder chamber and the small-diameter cylinder chamber are separated from each other. In a state where the discharge of the hydraulic fluid to the tank is allowed, the hydraulic fluid is supplied to the first cylinder chamber to perform mold clamping.
The mold clamping device according to claim 1, further comprising a control device that controls the coupling portion and the hydraulic circuit. A moving mechanism for moving the moving die plate in the mold opening and closing direction;
The control device includes:
After the molding material is solidified, the first cylinder chamber and the second cylinder chamber are connected, and the first cylinder chamber and the small-diameter cylinder chamber are shut off, and hydraulic fluid is supplied to the small-diameter cylinder chamber. Moving the movable die plate in the mold opening direction, separating the fixed mold and the movable mold;
After the separation, release the coupled portion and the coupling portion,
After the release, the moving die plate is further moved in the mold opening direction by the moving mechanism,
The tie bar is moved to a position where the coupled portion and the coupling portion can be coupled in a state where the mold is in contact after the release until the mold contact in the next cycle.
The mold clamping apparatus of any one of Claims 1-3 which controls the said moving mechanism, the said connection part, and the said hydraulic circuit. The control device includes:
The tie bar reaches the connectable position in the next cycle by the start of mold closing in the next cycle,
The mold clamping device according to claim 4, wherein the tie bar is moved during mold closing in the next cycle so as to eliminate a deviation between the position of the tie bar and the position where the tie bar can be combined in the next cycle, which occurs after the arrival. . A fixed die plate for holding a fixed mold;
A movable die plate that holds a movable mold and is movable in a mold opening and closing direction with respect to the fixed die plate;
A piston that generates a clamping force for clamping the stationary mold and the movable mold, and a clamping cylinder that houses the piston;
A hydraulic pressure source for supplying hydraulic fluid of a predetermined pressure to the mold clamping cylinder;
A tank for storing the hydraulic fluid discharged from the mold clamping cylinder;
A hydraulic circuit for controlling the flow of hydraulic fluid between the hydraulic pressure source, the tank and the clamping cylinder;
Have
The mold clamping cylinder is
A large-diameter cylinder chamber to which hydraulic fluid is supplied when the movable die plate is moved in the mold clamping direction;
A small-diameter cylinder chamber that communicates with the large-diameter cylinder chamber, has a smaller diameter than the large-diameter cylinder chamber, and is supplied with hydraulic fluid when moving the movable die plate in the mold opening direction;
Have
The piston is
The large diameter cylinder chamber is slidable in the large diameter cylinder chamber and divides the large diameter cylinder chamber into a first cylinder chamber opposite to the small diameter cylinder chamber and a second cylinder chamber on the small diameter cylinder chamber side. A piston part;
A small-diameter piston portion projecting from the end surface of the large-diameter piston portion on the small-diameter cylinder chamber side, and capable of sliding the small-diameter cylinder chamber;
Have
From the end surface of the small diameter piston portion on the side of the small diameter cylinder chamber, a rod portion that closes the opening of the small diameter cylinder chamber on the side opposite to the large diameter cylinder chamber protrudes,
The pressure receiving area on the first cylinder chamber side of the large diameter piston portion is the sum of the pressure receiving area on the second cylinder chamber side of the large diameter piston portion and the pressure receiving area on the small diameter cylinder chamber side of the small diameter piston portion. big,
The hydraulic circuit is
The first cylinder chamber and the second cylinder chamber can be connected or disconnected,
The first cylinder chamber and the small diameter cylinder chamber can be connected or disconnected,
The supply destination of hydraulic fluid from the hydraulic pressure source can be switched between the first cylinder chamber and the small diameter cylinder chamber.
The discharge of hydraulic fluid from the second cylinder chamber and the small diameter cylinder chamber to the tank can be allowed or prohibited,
Clamping device is composed of.

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