JP7661666B2 - Injection Molding Machine - Google Patents

Description

The present invention relates to an injection molding machine.

In an injection molding machine, a mold closing process is carried out in which a fixed mold and a movable mold, which constitute a mold device for molding a molded product, are brought into contact with each other. A technology has been proposed that uses a hydraulic cylinder as a clamping device to move the movable mold during the mold closing process.

JP2006-015553A

Patent Document 1 describes a technique for the mold opening process when a hydraulic cylinder is used in the mold clamping device. Specifically, during the mold opening process, the torque is limited and the time element is monitored to detect whether there is an abnormality.

When a hydraulic cylinder is used in the clamping device, if control is performed to move the movable platen during the mold closing process, the torque or pressure is limited to a low level and the time element is monitored to detect whether or not there is an abnormality. In this control, the torque or pressure is limited to a low level, so due to the influence of loads such as friction, the mold closing time until the mold closing process is completed varies greatly. For this reason, the monitoring time (time element) for determining whether or not there is an abnormality must be set long with a considerable margin of error.

Therefore, during the mold closing process, if a foreign object is caught between the fixed mold and the movable mold when it is being determined whether the mold closing process has been completed within the monitoring time, a load will continue to be applied to the mold device until the monitoring time has elapsed.

One aspect of the present invention provides a technology that enables rapid detection of abnormalities when controlling the speed of the movable platen during the mold closing process.

An injection molding machine according to one aspect of the present invention includes a stationary platen on which a stationary mold is attached, a movable platen on which a movable mold is attached, a mold clamping device that performs a mold closing process in which the movable platen is moved by fluid pressure to bring the movable platen into contact with the stationary platen, a hydraulic cylinder that generates fluid pressure, a flow path that connects multiple oil chambers of the hydraulic cylinder, a bi-directional rotary pump provided in the middle of the flow path, a servo motor that controls the rotation of the bi-directional rotary pump, and a control unit that controls the mold clamping device. The mold clamping device is capable of switching the flow of oil flowing through the flow path based on the rotation direction of the bi-directional rotary pump. The control unit includes a speed control unit that controls the speed of the movable platen in the mold closing process, an acquisition unit that acquires a pressure value indicating the fluid pressure generated by the movement of the movable platen, a determination unit that determines whether the pressure value acquired by the acquisition unit exceeds a predetermined threshold value, and a motor control unit that controls the output of the servo motor according to the pressure value .

According to one aspect of the present invention, when controlling the speed of the movable platen, changes in fluid pressure caused by the movement of the movable platen are detected, making it possible to quickly detect abnormalities.

FIG. 1 is a diagram showing a state when mold opening of an injection molding machine according to an embodiment is completed. FIG. 2 is a diagram showing a state during mold clamping of the injection molding machine according to the embodiment. FIG. 3 is a diagram illustrating an example of a mold clamping device according to the first embodiment. FIG. 4 is a diagram showing components of the control device according to the first embodiment in the form of functional blocks. FIG. 5 is a diagram illustrating an example of pressure control in the pressure control unit of the control device according to the first embodiment. FIG. 6 is a diagram showing an example of speed control in the speed control unit according to the first embodiment. FIG. 7 is a flowchart showing a process for performing speed control in the mold closing process of the control device according to the first embodiment. FIG. 8 is a diagram showing an example of speed control in the speed control unit according to the first modification.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that in each drawing, the same or corresponding components are denoted by the same or corresponding reference numerals, and the description thereof may be omitted.

Figure 1 is a diagram showing the state of an injection molding machine according to one embodiment when mold opening is completed. Figure 2 is a diagram showing the state of an injection molding machine according to one embodiment when mold clamping is performed. In this specification, the X-axis direction, Y-axis direction, and Z-axis direction are perpendicular to each other. The X-axis direction and Y-axis direction represent the horizontal direction, and the Z-axis direction represents the vertical direction. When the mold clamping device 100 is of a horizontal type, the X-axis direction is the mold opening and closing direction, and the Y-axis direction is the width direction of the injection molding machine 10. The negative side of the Y-axis direction is called the operation side, and the positive side of the Y-axis direction is called the anti-operation side.

1 and 2, the injection molding machine 10 includes a clamping device 100 that opens and closes the mold device 800, an injection device 300 that injects molding material into the mold device 800, a moving device 400 that moves the injection device 300 forward and backward relative to the mold device 800, a control device 700 that controls each component of the injection molding machine 10, and a frame 900 that supports each component of the injection molding machine 10. The injection molding machine 10 also includes an ejector device (not shown) that ejects a molded product molded by the mold device 800 from the mold device 800 (movable mold 820). The frame 900 includes a clamping device frame 910 that supports the clamping device 100, and an injection device frame 920 that supports the injection device 300. The clamping device frame 910 and the injection device frame 920 are each installed on the floor 2 via a leveling adjuster 930. The control device 700 is disposed in the internal space of the injection unit frame 920. Each of the components of the injection molding machine 10 will now be described.

(Mold clamping device)
In the description of the mold clamping apparatus 100, the moving direction of the movable platen 120 during mold closing (e.g., the positive X-axis direction) is defined as the front, and the moving direction of the movable platen 120 during mold opening (e.g., the negative X-axis direction) is defined as the rear.

The mold clamping device 100 performs the mold closing process, pressure increase process, mold clamping process, depressurization process, and mold opening process of the mold device 800. The mold device 800 includes a fixed mold 810, a movable mold 820, and a movable member 830 that is arranged inside (hollow portion of) the movable mold 820 so as to be movable back and forth.

The mold clamping device 100 is, for example, a horizontal type, and the mold opening and closing direction is horizontal. The mold clamping device 100 has a fixed platen 110, a movable platen 120, tie bars 140, a hydraulic cylinder 150, etc.

The fixed platen 110 is fixed to the mold clamping unit frame 910. A fixed mold 810 is attached to the surface of the fixed platen 110 facing the movable platen 120.

The movable platen 120 is arranged to be freely movable in the mold opening and closing direction relative to the mold clamping unit frame 910. A guide 101 for guiding the movable platen 120 is laid on the mold clamping unit frame 910. A movable mold 820 is attached to the surface of the movable platen 120 facing the fixed platen 110. By moving the movable platen 120 back and forth relative to the fixed platen 110, the mold closing process, pressurization process, mold clamping process, depressurization process, and mold opening process of the mold device 800 are performed.

The tie bars 140 connect the fixed platen 110 and the cylinder body 151 of the hydraulic cylinder 150 (see FIG. 3) at a distance L in the mold opening/closing direction. Multiple tie bars 140 (e.g., four) may be used. The multiple tie bars 140 are arranged parallel to the mold opening/closing direction and extend according to the mold clamping force.

The hydraulic cylinder 150 is attached to the movable platen. The hydraulic cylinder 150 drives the movable platen 120 by a so-called direct pressure system, and moves the movable platen 120 in the mold opening and closing direction. The configuration of the hydraulic cylinder 150 and the details of the drive mechanism will be described later (see FIG. 3).

The mold clamping device 100 performs processes such as mold closing, pressure increase, mold clamping, depressurization, and mold opening under the control of the control device 700.

In the mold closing process, the hydraulic cylinder 150 is driven to advance the hydraulic cylinder 150 (piston portion 152 described below) to the mold closing completion position at a set moving speed, thereby advancing the movable platen 120 and touching the movable mold 820 to the fixed mold 810. The position and moving speed of the hydraulic cylinder 150 are detected, for example, using a cylinder pressure sensor. The cylinder pressure sensor detects the extension/retraction position of the hydraulic cylinder 150 and sends a signal indicating the detection result to the control device 700. As a result, the control device 700 can perform feedback control (position control of the hydraulic cylinder 150) regarding the position of the hydraulic cylinder 150 (movable platen 120) based on the signal indicating the detection result of the cylinder pressure sensor during the mold clamping process and the mold opening process described below.

In addition, the hydraulic cylinder position detector that detects the position of the hydraulic cylinder 150 and the hydraulic cylinder movement speed detector that detects the movement speed of the hydraulic cylinder 150 are not limited to cylinder pressure sensors and general-purpose sensors can be used.

In the pressure increase process, the hydraulic cylinder 150 is further driven to control the pressure of the hydraulic cylinder 150 to a predetermined pressure (hereinafter, "target clamping pressure"), and the pressure of the hydraulic cylinder 150 is increased to generate a clamping force. The pressure of the hydraulic cylinder 150 is detected, for example, using a pressure sensor (cylinder pressure sensor) provided in the hydraulic cylinder 150. The cylinder pressure sensor detects the pressure of a predetermined oil chamber inside the hydraulic cylinder 150 (for example, the oil chamber 155 described below) and sends a signal indicating the detection result to the control device 700. As a result, the control device 700 can perform feedback control of the pressure of the hydraulic cylinder 150 (pressure control of the hydraulic cylinder 150) based on the signal indicating the detection result of the cylinder pressure sensor during the pressure increase process and the clamping process and depressurization process described below.

In the mold clamping process, the hydraulic cylinder 150 is driven to maintain the pressure of the hydraulic cylinder 150 at the target mold clamping pressure. In the mold clamping process, the mold clamping force generated in the pressure increase process is maintained. In the mold clamping process, a cavity space 801 (see Figure 2) is formed between the movable mold 820 and the fixed mold 810, and the injection device 300 fills the cavity space 801 with liquid molding material. The filled molding material is solidified to obtain a molded product.

The number of cavity spaces 801 may be one or more. In the latter case, multiple molded products are obtained simultaneously. An insert material may be placed in a part of the cavity space 801, and another part of the cavity space 801 may be filled with molding material. A molded product in which the insert material and molding material are integrated is obtained.

In the depressurization process, the clamping force is reduced by driving the hydraulic cylinder 150 to reduce the hydraulic cylinder 150 from the target clamping pressure.

In the mold opening process, the hydraulic cylinder 150 is driven to move the hydraulic cylinder 150 (piston portion 152) backward at a set moving speed from the mold opening start position to the mold opening completion position, thereby moving the movable platen 120 backward and separating the movable mold 820 from the fixed mold 810. After that, the ejector device ejects the molded product from the movable mold 820. The mold opening start position and the mold closing completion position may be the same position.

The setting conditions for the mold closing process, the pressure increase process, and the mold clamping process are set together as a series of setting conditions. For example, the moving speed, position (including the mold closing start position, the moving speed switching position, the mold closing completion position, and the mold clamping position), pressure (including the target mold clamping pressure), and mold clamping force of the hydraulic cylinder 150 in the mold closing process and the pressure increase process are set together as a series of setting conditions. The mold closing start position, the moving speed switching position, the mold closing completion position, and the mold clamping position are arranged in this order from the rear side to the front, and represent the start and end points of the section in which the moving speed is set. The moving speed is set for each section. There may be one or more moving speed switching positions. The moving speed switching position does not have to be set. Only one or two of the mold clamping position, the target mold clamping pressure, and the mold clamping force may be set.

The setting conditions for the depressurization process and mold opening process are also set in the same manner. For example, the movement speed and position of the hydraulic cylinder 150 in the depressurization process and mold opening process (mold opening start position, movement speed switching position, and mold opening completion position) are set together as a series of setting conditions. The mold opening start position, movement speed switching position, and mold opening completion position are arranged in this order from the front to the rear, and represent the start and end points of the section in which the movement speed is set. The movement speed is set for each section. There may be one or more movement speed switching positions. The movement speed switching position does not have to be set. The mold opening start position and the mold closing completion position may be the same position. Furthermore, the mold opening completion position and the mold closing start position may be the same position.

In addition, the moving speed and position of the movable platen 120 may be set instead of the moving speed and position of the hydraulic cylinder 150. Also, instead of the position of the hydraulic cylinder 150 (e.g., the clamping position) or the position of the movable platen 120, a target clamping pressure or clamping force may be set.

In addition, the mold clamping device 100 of this embodiment is a horizontal type in which the mold opening and closing direction is horizontal, but it may also be a vertical type in which the mold opening and closing direction is vertical.

(Ejector device)
In describing the ejector device, similarly to the description of the mold clamping device 100, the direction of movement of the movable platen 120 when the mold is closed (e.g., the positive direction of the X-axis) is defined as the front, and the direction of movement of the movable platen 120 when the mold is opened (e.g., the negative direction of the X-axis) is defined as the rear.

The ejector device is attached to the movable platen 120 and moves forward and backward together with the movable platen 120. The ejector device has an ejector rod that ejects the molded product from the mold device 800 and a drive mechanism that moves the ejector rod in the movement direction of the movable platen 120 (X-axis direction).

The ejector rod comes into contact with a movable member 830 that is arranged inside the movable mold 820 and can freely move back and forth, thereby moving the movable member forward.

The drive mechanism has, for example, an ejector motor and a motion conversion mechanism that converts the rotational motion of the ejector motor into the linear motion of the ejector rod. The motion conversion mechanism includes a screw shaft and a screw nut that screws onto the screw shaft. Balls or rollers may be interposed between the screw shaft and the screw nut.

The ejector device performs the ejection process under the control of the control device 700. In the ejection process, the ejector device advances the movable member 830 to eject the molded product.

The position and movement speed of the ejector rod are detected, for example, using an ejector motor encoder. The ejector motor encoder detects the rotation of the ejector motor and sends a signal indicating the detection result to the control device 700. In addition, the ejector rod position detector that detects the position of the ejector rod and the ejector rod movement speed detector that detects the movement speed of the ejector rod are not limited to the ejector motor encoder, and general types can be used.

(Injection unit)
In the explanation of the injection unit 300, unlike the explanations of the mold clamping unit 100 and the ejector unit 200, the movement direction of the screw 330 during filling (e.g., the negative X-axis direction) is described as the forward direction, and the movement direction of the screw 330 during metering (e.g., the positive X-axis direction) is described as the rearward direction.

The injection device 300 is mounted on a slide base 301, and the slide base 301 is arranged so as to be freely movable forward and backward with respect to the injection device frame 920. The injection device 300 is arranged so as to be freely movable forward and backward with respect to the mold device 800. The injection device 300 touches the mold device 800 and fills the cavity space 801 in the mold device 800 with molding material. The injection device 300 has, for example, a cylinder 310, a nozzle 320, a screw 330, a metering motor 340, an injection motor 350, a load detector 360, and the like.

Cylinder 310 heats the molding material supplied to the inside from supply port 311. The molding material includes, for example, resin. The molding material is formed, for example, in pellet form and supplied to supply port 311 in a solid state. Supply port 311 is formed at the rear of cylinder 310. A cooler 312 such as a water-cooled cylinder is provided on the outer periphery of the rear of cylinder 310. A heater 313 such as a band heater and a temperature detector 314 are provided on the outer periphery of cylinder 310 forward of cooler 312.

The cylinder 310 is divided into a plurality of zones in the axial direction of the cylinder 310 (e.g., the X-axis direction). A heater 313 and a temperature detector 314 are provided in each of the plurality of zones. A set temperature is set in each of the plurality of zones, and the control device 700 controls the heater 313 so that the detected temperature of the temperature detector 314 becomes the set temperature.

The nozzle 320 is provided at the front end of the cylinder 310 and is pressed against the mold device 800. A heater 313 and a temperature detector 314 are provided on the outer periphery of the nozzle 320. The control device 700 controls the heater 313 so that the detected temperature of the nozzle 320 becomes the set temperature.

The screw 330 is arranged in the cylinder 310 so that it can rotate freely and move forward and backward. When the screw 330 is rotated, the molding material is sent forward along the spiral groove of the screw 330. As the molding material is sent forward, it is gradually melted by heat from the cylinder 310. As the liquid molding material is sent forward to the front of the screw 330 and accumulates at the front of the cylinder 310, the screw 330 is moved backward. When the screw 330 is then moved forward, the liquid molding material accumulated in front of the screw 330 is injected from the nozzle 320 and filled into the mold device 800.

A backflow prevention ring 331 is attached to the front of the screw 330 and can move back and forth as a backflow prevention valve to prevent the molding material from flowing back from the front to the rear of the screw 330 when the screw 330 is pushed forward.

When the screw 330 is advanced, the backflow prevention ring 331 is pushed backward by the pressure of the molding material in front of the screw 330, and retreats relative to the screw 330 to a blocking position (see FIG. 2) where the flow path of the molding material is blocked. This prevents the molding material accumulated in front of the screw 330 from flowing backward.

On the other hand, when the screw 330 is rotated, the backflow prevention ring 331 is pushed forward by the pressure of the molding material sent forward along the spiral groove of the screw 330, and advances relative to the screw 330 to an open position (see FIG. 1) where the flow path of the molding material is opened. This causes the molding material to be sent forward of the screw 330.

The backflow prevention ring 331 may be either a co-rotating type that rotates with the screw 330, or a non-co-rotating type that does not rotate with the screw 330.

In addition, the injection device 300 may have a driving source that moves the backflow prevention ring 331 back and forth between the open position and the closed position relative to the screw 330.

The metering motor 340 rotates the screw 330. The driving source for rotating the screw 330 is not limited to the metering motor 340 and may be, for example, a hydraulic pump.

The injection motor 350 advances and retreats the screw 330. Between the injection motor 350 and the screw 330, a motion conversion mechanism that converts the rotational motion of the injection motor 350 into the linear motion of the screw 330 is provided. The motion conversion mechanism has, for example, a screw shaft and a screw nut that screws onto the screw shaft. A ball or roller may be provided between the screw shaft and the screw nut. The drive source that advances and retreats the screw 330 is not limited to the injection motor 350, and may be, for example, a hydraulic cylinder.

The load detector 360 detects the force transmitted between the injection motor 350 and the screw 330. The detected force is converted to pressure by the control device 700. The load detector 360 is provided in the force transmission path between the injection motor 350 and the screw 330, and detects the force acting on the load detector 360.

The load detector 360 sends a signal indicating the detection result to the control device 700. The detection result of the load detector 360 is used to control and monitor the pressure that the screw 330 receives from the molding material, the back pressure on the screw 330, the pressure that the screw 330 exerts on the molding material, and the like.

The pressure detector that detects the pressure of the molding material is not limited to the load detector 360, and a general one can be used. For example, a nozzle pressure sensor or a mold internal pressure sensor may be used. The nozzle pressure sensor is installed in the nozzle 320. The mold internal pressure sensor is installed inside the mold device 800.

The injection device 300 performs a metering process, a filling process, a pressure holding process, etc. under the control of the control device 700. The filling process and the pressure holding process may be collectively referred to as the injection process.

In the metering process, the metering motor 340 is driven to rotate the screw 330 at a set rotational speed, and the molding material is sent forward along the spiral groove of the screw 330. As a result, the molding material is gradually melted. As the liquid molding material is sent forward of the screw 330 and accumulates at the front of the cylinder 310, the screw 330 is moved backward. The rotational speed of the screw 330 is detected, for example, using the metering motor encoder 341. The metering motor encoder 341 detects the rotation of the metering motor 340 and sends a signal indicating the detection result to the control device 700. In addition, the screw rotational speed detector that detects the rotational speed of the screw 330 is not limited to the metering motor encoder 341, and a general one can be used.

In the metering process, in order to limit the sudden retreat of the screw 330, the injection motor 350 may be driven to apply a set back pressure to the screw 330. The back pressure on the screw 330 is detected, for example, using a load detector 360. The load detector 360 sends a signal indicating the detection result to the control device 700. When the screw 330 retreats to the metering completion position and a predetermined amount of molding material is accumulated in front of the screw 330, the metering process is completed.

The position and rotational speed of the screw 330 in the metering process are set together as a series of setting conditions. For example, a metering start position, a rotational speed switching position, and a metering completion position are set. These positions are arranged in this order from the front to the rear, and represent the start and end points of the section for which the rotational speed is set. The rotational speed is set for each section. There may be one or more rotational speed switching positions. The rotational speed switching position does not have to be set. In addition, a back pressure is set for each section.

In the filling process, the injection motor 350 is driven to advance the screw 330 at a set moving speed, and the liquid molding material accumulated in front of the screw 330 is filled into the cavity space 801 in the mold device 800. The position and moving speed of the screw 330 are detected, for example, using the injection motor encoder 351. The injection motor encoder 351 detects the rotation of the injection motor 350 and sends a signal indicating the detection result to the control device 700. When the position of the screw 330 reaches the set position, a switch from the filling process to the pressure holding process (so-called V/P switch) is performed. The position where the V/P switch is performed is also called the V/P switch position. The set moving speed of the screw 330 may be changed depending on the position of the screw 330, time, etc.

The position and movement speed of the screw 330 in the filling process are set together as a series of setting conditions. For example, the filling start position (also called the "injection start position"), the movement speed switching position, and the V/P switching position are set. These positions are arranged in this order from the rear to the front, and represent the start and end points of the section for which the movement speed is set. The movement speed is set for each section. There may be one or more movement speed switching positions. The movement speed switching position does not have to be set.

An upper limit value for the pressure of the screw 330 is set for each section in which the movement speed of the screw 330 is set. The pressure of the screw 330 is detected by the load detector 360. If the detection value of the load detector 360 is equal to or lower than the set pressure, the screw 330 is advanced at the set movement speed. On the other hand, if the detection value of the load detector 360 exceeds the set pressure, the screw 330 is advanced at a movement speed slower than the set movement speed so that the detection value of the load detector 360 is equal to or lower than the set pressure, in order to protect the mold.

In addition, after the position of the screw 330 reaches the V/P switching position during the filling process, the screw 330 may be temporarily stopped at the V/P switching position, and then the V/P switching may be performed. Just before the V/P switching, instead of stopping the screw 330, the screw 330 may be moved forward or backward at a slow speed. In addition, the screw position detector that detects the position of the screw 330 and the screw movement speed detector that detects the movement speed of the screw 330 are not limited to the injection motor encoder 351, and general ones can be used.

In the holding pressure process, the injection motor 350 is driven to push the screw 330 forward, and the pressure of the molding material at the front end of the screw 330 (hereinafter also referred to as the "holding pressure") is maintained at a set pressure, and the molding material remaining in the cylinder 310 is pushed toward the mold device 800. The molding material that is insufficient due to cooling contraction in the mold device 800 can be replenished. The holding pressure is detected, for example, using a load detector 360. The load detector 360 sends a signal indicating the detection result to the control device 700. The set value of the holding pressure may be changed depending on the elapsed time from the start of the holding pressure process, etc. The holding pressure and the holding time for holding the holding pressure in the holding pressure process may each be set multiple times, or may be set together as a series of setting conditions.

During the dwelling process, the molding material in the cavity space 801 in the mold device 800 is gradually cooled, and when the dwelling process is completed, the entrance to the cavity space 801 is blocked by solidified molding material. This state is called a gate seal, and prevents the molding material from flowing back from the cavity space 801. After the dwelling process, the cooling process is started. During the cooling process, the molding material in the cavity space 801 is solidified. A weighing process may be performed during the cooling process in order to shorten the molding cycle time.

The injection device 300 of this embodiment is an in-line screw type, but may also be a pre-plastication type, etc. An injection device of the pre-plastication type supplies molding material molten in a plasticization cylinder to an injection cylinder, and injects the molding material from the injection cylinder into a mold device. Within the plasticization cylinder, a screw is arranged so that it can rotate freely but cannot move forward or backward, or the screw is arranged so that it can rotate freely and move forward or backward. Meanwhile, within the injection cylinder, a plunger is arranged so that it can move forward or backward.

In addition, the injection device 300 of this embodiment is a horizontal type in which the axial direction of the cylinder 310 is horizontal, but it may be a vertical type in which the axial direction of the cylinder 310 is vertical. The mold clamping device combined with the vertical injection device 300 may be either a vertical type or a horizontal type. Similarly, the mold clamping device combined with the horizontal injection device 300 may be either a horizontal type or a vertical type.

Thus, in this embodiment, the injection unit 300 is electrically driven by electric actuators such as the metering motor 340 and the injection motor 350. This allows the injection unit 300 to be relatively more responsive to control commands from the control unit 700 than when it is hydraulically driven. Therefore, the injection molding machine 10 can achieve relatively excellent controllability of the injection unit 300.

(Mobile device)
In describing the moving device 400, similar to the description of the injection device 300, the movement direction of the screw 330 during filling (e.g., the negative X-axis direction) will be described as the forward direction, and the movement direction of the screw 330 during metering (e.g., the positive X-axis direction) will be described as the rearward direction.

The moving device 400 moves the injection device 300 forward and backward relative to the mold device 800. The moving device 400 also presses the nozzle 320 against the mold device 800 to generate nozzle touch pressure. The moving device 400 includes a hydraulic pump 410, a motor 420 as a drive source, a hydraulic cylinder 430 as a hydraulic actuator, and the like.

The hydraulic pump 410 has a first port 411 and a second port 412. The hydraulic pump 410 is a pump that can rotate in both directions, and by switching the rotation direction of the motor 420, it draws in hydraulic fluid (e.g., oil) from either the first port 411 or the second port 412 and discharges it from the other port to generate hydraulic pressure. The hydraulic pump 410 can also draw in hydraulic fluid from a tank and discharge the hydraulic fluid from either the first port 411 or the second port 412.

The motor 420 operates the hydraulic pump 410. The motor 420 drives the hydraulic pump 410 with a rotational direction and rotational torque according to a control signal from the control device 700. The motor 420 may be an electric motor or an electric servo motor.

The hydraulic cylinder 430 has a cylinder body 431, a piston 432, and a piston rod 433. The cylinder body 431 is fixed to the injection device 300. The piston 432 divides the inside of the cylinder body 431 into a front chamber 435 as a first chamber and a rear chamber 436 as a second chamber. The piston rod 433 is fixed to the fixed platen 110.

The front chamber 435 of the hydraulic cylinder 430 is connected to the first port 411 of the hydraulic pump 410 via the first flow path 401. The hydraulic fluid discharged from the first port 411 is supplied to the front chamber 435 via the first flow path 401, thereby pushing the injection device 300 forward. The injection device 300 is moved forward, and the nozzle 320 is pressed against the fixed mold 810. The front chamber 435 functions as a pressure chamber that generates nozzle touch pressure of the nozzle 320 by the pressure of the hydraulic fluid supplied from the hydraulic pump 410.

Meanwhile, the rear chamber 436 of the hydraulic cylinder 430 is connected to the second port 412 of the hydraulic pump 410 via the second flow path 402. The hydraulic fluid discharged from the second port 412 is supplied to the rear chamber 436 of the hydraulic cylinder 430 via the second flow path 402, thereby pushing the injection device 300 backward. The injection device 300 is retracted, and the nozzle 320 is separated from the fixed mold 810.

In this embodiment, the moving device 400 includes a hydraulic cylinder 430, but the present invention is not limited to this. For example, instead of the hydraulic cylinder 430, an electric motor and a motion conversion mechanism that converts the rotational motion of the electric motor into the linear motion of the injection device 300 may be used.

(Control device)
The control device 700 is configured, for example, by a computer, and has a CPU (Central Processing Unit) 701, a storage medium 702 such as a memory, an input interface 703, and an output interface 704 as shown in Figures 1 and 2. The control device 700 performs various controls by causing the CPU 701 to execute a program stored in the storage medium 702. The control device 700 also receives signals from the outside via the input interface 703, and transmits signals to the outside via the output interface 704.

The control device 700 repeatedly manufactures molded products by repeating processes such as the metering process, mold closing process, pressure increase process, mold clamping process, filling process, pressure holding process, cooling process, depressurization process, mold opening process, and ejection process. A series of operations required to obtain a molded product, for example the operations from the start of a metering process to the start of the next metering process, is also called a "shot" or "molding cycle." The time required for one shot is also called the "molding cycle time" or "cycle time."

One molding cycle includes, for example, a metering process, a mold closing process, a pressurization process, a mold clamping process, a filling process, a pressure holding process, a cooling process, a depressurization process, a mold opening process, and an ejection process, in this order. The order here refers to the order in which each process starts. The filling process, the pressure holding process, and the cooling process are performed during the mold clamping process. The start of the mold clamping process may coincide with the start of the filling process. The end of the depressurization process coincides with the start of the mold opening process.

Note that, in order to shorten the molding cycle time, multiple processes may be performed simultaneously. For example, the metering process may be performed during the cooling process of the previous molding cycle, or during the mold clamping process. In this case, the mold closing process may be performed at the beginning of the molding cycle. The filling process may be started during the mold closing process. The ejection process may be started during the mold opening process. If an opening/closing valve is provided to open and close the flow path of the nozzle 320, the mold opening process may be started during the metering process. This is because even if the mold opening process is started during the metering process, molding material will not leak from the nozzle 320 as long as the opening/closing valve closes the flow path of the nozzle 320.

In addition, one molding cycle may include processes other than the metering process, mold closing process, pressure increase process, mold clamping process, filling process, pressure holding process, cooling process, depressurization process, mold opening process, and ejection process.

For example, after the completion of the dwelling process and before the start of the metering process, a pre-metering suck-back process may be performed in which the screw 330 is retracted to a preset metering start position. This can reduce the pressure of the molding material accumulated in front of the screw 330 before the start of the metering process, and can prevent the screw 330 from retracting suddenly at the start of the metering process.

In addition, after the metering process is completed and before the filling process is started, a post-metering suck-back process may be performed in which the screw 330 is retracted to a preset filling start position (also called the "injection start position"). This can reduce the pressure of the molding material accumulated in front of the screw 330 before the filling process starts, and can prevent the molding material from leaking from the nozzle 320 before the filling process starts.

The control device 700 is connected to an operation device 750 that accepts input operations by the user and a display device 760 that displays a screen. The operation device 750 and the display device 760 may be configured, for example, by a touch panel 770 and may be integrated. The touch panel 770 as the display device 760 displays a screen under the control of the control device 700. The screen of the touch panel 770 may display, for example, information such as the settings of the injection molding machine 10 and the current state of the injection molding machine 10. In addition, the screen of the touch panel 770 may display, for example, an operation unit such as a button that accepts input operations by the user and an input field. The touch panel 770 as the operation device 750 detects an input operation on the screen by the user and outputs a signal corresponding to the input operation to the control device 700. As a result, for example, the user can operate the operation unit provided on the screen while checking the information displayed on the screen to set the injection molding machine 10 (including input of setting values). In addition, the user can operate the operation unit provided on the screen to perform the operation of the injection molding machine 10 corresponding to the operation unit. The operation of the injection molding machine 10 may be, for example, the operation (including stopping) of the clamping device 100, the ejector device 200, the injection device 300, the moving device 400, etc. The operation of the injection molding machine 10 may be, for example, switching of a screen displayed on the touch panel 770 serving as the display device 760, etc.

In this embodiment, the operation device 750 and the display device 760 have been described as being integrated as the touch panel 770, but they may be provided independently. Also, multiple operation devices 750 may be provided. The operation device 750 and the display device 760 are arranged on the operation side (negative Y-axis direction) of the mold clamping device 100 (more specifically, the fixed platen 110).

First Embodiment
Next, the details of the mold clamping device 100 will be described with reference to FIG.

Figure 3 is a diagram showing an example of the mold clamping device 100 according to this embodiment. Specifically, Figure 3 is a diagram showing the operating state of the mold clamping device 100 in the mold closing process. Note that in Figure 3, the mold device 800 is omitted from the drawing.

As shown in FIG. 3, the mold clamping device 100 includes a fixed platen 110, a movable platen 120, a tie bar 140, a hydraulic cylinder 150, a hydraulic circuit 160, and a servo motor 170.

The hydraulic cylinder 150 includes a cylinder body portion 151, a piston portion 152, a rod portion 153, and a cylinder closure portion 154.

The cylinder body 151 is a fixed part of the hydraulic cylinder 150. The cylinder body 151 is connected to one end of a tie bar 140, the other end of which is connected to the fixed platen 110. This fixes the distance between the cylinder body 151 and the fixed platen 110 at a constant value (distance L). The cylinder body 151 has a hollow portion whose front end (the end in the negative direction of the X-axis) is open.

One of the cylinder body 151 and the fixed platen 110, which are connected via the tie bar 140, is fixed to the mold clamping unit frame 910, and the other is movably mounted on the mold clamping unit frame 910. This allows the tie bar 140 to be allowed to stretch due to the generation of the mold clamping force.

One end of the piston portion 152 is inserted into the interior (hollow portion) of the cylinder body portion 151, and the other end is fixed to the movable platen 120. This allows the piston portion 152 to move in the front-to-back direction (X direction) due to the action of the working oil supplied to and discharged from the cylinder body portion 151, and as a result, the movable platen 120 fixed to one end of the piston portion 152 can be moved in the front-to-back direction (X direction). In addition, the piston portion 152 is provided with a hollow portion that is open to the interior side of the cylinder body portion 151.

One end of the rod portion 153 is fixed to the closed end of the hollow portion of the cylinder body portion 151 (i.e., the end in the negative direction of the X-axis), and the other end is inserted into the hollow portion of the piston portion 152. This allows the rod portion 153 to move the piston portion 152 forward (in the positive direction of the X-axis) by the action of hydraulic oil supplied to the hollow portion of the piston portion 152 (oil chamber 157 described below). In addition, the rod portion 153 is provided with a hole portion extending in the axial direction from the other end side inserted into the hollow portion of the piston portion 152.

The cylinder closing portion 154 closes the open end of the cylinder body portion 151. The cylinder closing portion 154 is provided with a through hole through which the piston portion 152 can pass and move back and forth.

In addition, oil chambers 155 to 157 are provided inside the hydraulic cylinder 150.

The oil chamber 155 is provided at the closed end (the end in the negative X-axis direction) of the hollow portion of the cylinder body 151, partitioned by the inner wall of the cylinder body 151 and the tip (one end) of the piston 152. This allows the piston 152 to apply a clamping force to the movable platen 120 by the action of the hydraulic oil supplied to the oil chamber 155. The oil chamber 155 is provided with a port 155P for supplying and discharging the hydraulic oil.

This embodiment describes the mold closing process, and the hydraulic circuit that supplies and discharges working oil to the oil chamber 155 to apply the mold clamping force can be the same as a conventional hydraulic circuit, so its description is omitted.

The oil chamber 156 is provided at the open end (the end in the positive direction of the X-axis) of the cylinder body 151, partitioned by the inner wall of the cylinder body 151, the inner wall of the cylinder closing portion 154, and the middle portion of the piston portion 152. This allows the piston portion 152 to move backward (i.e., move in the negative direction of the X-axis) due to the action of hydraulic oil supplied to the oil chamber 156. The oil chamber 156 is provided with a port 156P for supplying and discharging hydraulic oil.

The oil chamber 157 is defined by the inner wall of the hollow portion of the piston portion 152 and the tip of the rod portion 153. This allows the piston portion 152 to move forward (i.e., move in the positive direction of the X-axis) due to the action of hydraulic oil supplied to the oil chamber 157. The oil chamber 157 is connected to a hole in the rod portion 153, and a port 157P is provided at the tip of the hole in the rod portion 153 for supplying and discharging hydraulic oil between the oil chamber 157.

The hydraulic circuit 160 drives the hydraulic cylinder 150. The hydraulic circuit 160 includes a mold closing side relief valve 161, a mold opening side relief valve 162, an adjustment valve 163, a bidirectional rotary pump 164, a check valve 165, a check valve 166, a pressure sensor 167, a tank 168, and oil passages OL1 to OL3.

Oil passage OL1 connects the tank 168, the mold closing side relief valve 161, the mold opening side relief valve 162, the check valve 165, and the check valve 166.

The oil passage OL2 connects the supply/discharge port 157P of the oil chamber 157 to the double rotary pump 164. The oil passage OL2 is also connected to each of the mold closing side relief valve 161, the adjustment valve 163, and the check valve 165. A pressure sensor 167 is provided near the supply/discharge port 157P of the oil chamber 157 in the oil passage OL2.

Oil passage OL3 connects the supply/discharge port 156P of the oil chamber 156 to the double rotary pump 164. Oil passage OL2 connects to each of the mold opening relief valve 162, the adjustment valve 163, and the check valve 166.

The bi-rotary pump 164 is provided on a flow path (oil passage OL2 and oil passage OL3) that connects between multiple oil chambers (oil chamber 157 and oil chamber 156) of the hydraulic cylinder 150 that generates fluid pressure. The bi-rotary pump 164 in this embodiment adjusts the flow direction and flow amount of the working oil flowing between the oil passage OL2 and the oil passage OL3 by being driven by the servo motor 170. In this way, the bi-rotary pump 164 can discharge the working oil to either the oil passage OL2 or the oil passage OL3 based on the drive of the servo motor 170.

For example, the bi-rotary pump 164 discharges the working oil supplied from oil passage OL2 to oil passage OL3 based on the drive of the servo motor 170. This creates a flow path through which the working oil flows from the supply/discharge port 157P of the oil chamber 157, through oil passage OL2 and then oil passage OL3, to the supply/discharge port 156P of the oil chamber 156. This causes the piston portion 152 to retract (i.e., move in the negative direction of the X-axis), thereby realizing the mold opening process in which the movable mold 820 is moved in the mold opening direction.

As another example, the double rotary pump 164 discharges the working oil supplied from oil passage OL3 to oil passage OL2 based on the drive of the servo motor 170. This creates a flow path through which the working oil flows from the supply/discharge port 156P of the oil chamber 156, through oil passage OL3 and oil passage OL2, to the supply/discharge port 157P of the oil chamber 157. This causes the piston portion 152 to move forward (i.e., move in the positive direction of the X-axis), thereby realizing the mold closing process in which the movable mold 820 is moved in the mold closing direction.

The mold opening relief valve 162 is a relief valve provided in the oil passage OL3, and is a mechanical valve that switches between an open state and a blocked state based on the pressure of the working oil flowing through the oil passage OL3. For example, during the mold opening process, when the pressure in the oil passage OL3 reaches or exceeds a predetermined pressure, the mold opening relief valve 162 is opened and the working oil flowing through the oil passage OL3 is discharged to the tank 168 via the oil passage OL1.

The mold closing side relief valve 161 is a relief valve provided in the oil passage OL2, and is a mechanical valve that switches between an open state and a closed state based on the pressure of the working oil flowing through the oil passage OL2. For example, during the mold closing process, when the oil passage OL2 reaches or exceeds a predetermined pressure, the mold closing side relief valve 161 is in a connected state, and the working oil flowing through the oil passage OL2 is discharged to the tank 168 via the oil passage OL1.

The check valve 165 is a valve that allows hydraulic oil to flow in one direction from oil passage OL1 to oil passage OL2 and prevents backflow. In the hydraulic circuit 160 of this embodiment, the check valve 165 is provided so that working oil is supplied from the tank 168 to the oil passage OL2.

The check valve 166 is a valve that allows hydraulic oil to flow in one direction from oil passage OL1 to oil passage OL3 and prevents backflow. In the hydraulic circuit 160 of this embodiment, the check valve 166 is provided so that working oil is supplied from the tank 168 to the oil passage OL3.

The tank 168 stores hydraulic oil. The tank 168 is also connected to the mold opening side relief valve 162, the mold closing side relief valve 161, the check valve 165, and the check valve 166 through oil passage OL1. As a result, the tank 168 stores the working oil discharged from the mold opening side relief valve 162 or the mold closing side relief valve 161 through oil passage OL1. The tank 168 also supplies the stored working oil through oil passage OL1 from the check valve 165 to oil passage OL2, or from the check valve 166 to oil passage OL3.

The adjustment valve 163 is a valve for adjusting the amount of oil in each of the oil passages OL2 and OL3 during the mold opening process and the mold closing process. By providing the adjustment valve 163, the flow rate can be adjusted to be constant during the mold opening process and the mold closing process.

The pressure sensor 167 is located on the oil passage OL2 near the supply/discharge port 157P of the oil chamber 157 of the hydraulic cylinder 150, and detects the pressure acting on the oil chamber 157 of the hydraulic cylinder 150.

In other words, in the hydraulic circuits that control the hydraulic cylinders that were previously used, a variable pump that could only discharge working oil in one direction was often used instead of a bidirectional rotary pump 164 that could discharge working oil in both directions. When such a variable pump was used, an electromagnetic switching valve (an example of a directional switching valve) was provided to switch the oil chamber that supplied the working oil. The mold opening process and mold closing process were realized by switching the oil chamber to which the working oil was supplied using this electromagnetic switching valve.

Conventional electromagnetic switching valves were often installed near the hydraulic cylinder. If a pressure sensor were installed in such a conventional hydraulic circuit, various parts that make up the electromagnetic switching valve would be between the hydraulic sensor and the hydraulic cylinder. Therefore, in conventional hydraulic circuits, it was difficult for the pressure sensor to detect the pressure applied to the oil chamber of the hydraulic cylinder.

In contrast, in the hydraulic circuit 160 of this embodiment, the oil chamber that supplies the working oil can be switched by switching the discharge direction of the working oil from the bidirectional rotary pump 164 depending on the rotation direction of the servo motor 170. This configuration makes it unnecessary to provide an electromagnetic contactor or the like between the hydraulic cylinder 150 and the pressure sensor 167. Furthermore, the hydraulic circuit 160 of this embodiment can reduce the number of components compared to conventional hydraulic circuits, so the piping length of the hydraulic circuit 160 can be shorter than conventional ones. Since the piping length can be shortened, the hydraulic circuit 160 can be formed from steel pipes. This makes it possible to reduce pressure changes due to disturbances.

The hydraulic circuit 160 that hydraulically drives the mold clamping device 100 (hydraulic cylinder 150) is configured as a closed circuit as described above. Moreover, in the hydraulic circuit 160 according to this embodiment, the pressure sensor 167 and the hydraulic cylinder 150 are directly connected by oil line OL2A (part of oil line OL2). In the hydraulic circuit 160, pressure changes due to disturbances can also be reduced, so the pressure sensor 167 can detect the pressure applied to the oil chamber 157 of the hydraulic cylinder 150 with high accuracy.

Compared to conventional hydraulic circuits, the hydraulic circuit 160 of this embodiment does not have an electromagnetic contactor and has a short piping length, so the amount of heat generated is small and the oil temperature is less likely to rise. This makes it possible to reduce the amount of hot water used in the hydraulic circuit 160. This allows the capacity of the tank 168 to be reduced, making the mold clamping device 100 more compact.

The servo motor 170 operates based on control from the control device 700 and controls the rotation of the double rotary pump 164. As a result, the control device 700 can control the operation of the double rotary pump 164 by controlling the servo motor 170.

The control device 700 controls the flow of hydraulic oil in the hydraulic circuit 160 by controlling the bi-directional rotary pump 164 (servo motor 170), and realizes the mold closing process and mold opening process by the mold clamping device 100. The control device 700 also realizes the pressurization process, mold clamping process, and depressurization process by controlling the hydraulic circuit 160, but a description of these will be omitted.

Figure 4 is a diagram showing the components of the control device 700 according to the first embodiment in functional blocks. Each functional block shown in Figure 4 is conceptual, and does not necessarily have to be physically configured as shown in the figure. It is possible to configure all or a part of each functional block by distributing and integrating it functionally or physically in any unit. All or any part of the processing functions performed by each functional block are realized by a program executed by the CPU 701. Alternatively, each functional block may be realized as hardware using wired logic. As shown in Figure 4, the control device 700 includes an input processing unit 711, a pressure control unit 712, a speed control unit 713, a switching unit 714, an acquisition unit 715, a determination unit 716, a stop control unit 717, and a notification unit 718. The control device 700 also includes a threshold storage unit 710 on the storage medium 702.

The threshold memory unit 710 stores the pressure threshold used when performing speed control during the mold closing process.

The input processing unit 711 processes the input of a user operation from the operation device 750 via the input interface 703. For example, the input processing unit 711 processes the input of a selection operation of either pressure control or speed control from the user when performing a mold closing process.

In this embodiment, when moving the movable platen in the mold closing process, the switching unit 714 switches between control of moving the movable platen 120 and the piston portion 152 by pressure control by the pressure control unit 712 and control of moving the movable platen 120 and the piston portion 152 by speed control by the speed control unit 713 based on the selection operation input and processed by the input processing unit 711. The pressure control unit 712 and the speed control unit 713 will be described later.

The pressure control unit 712 performs pressure control using the hydraulic cylinder 150 during the mold closing process. Figure 5 shows an example of pressure control in the pressure control unit 712. Figure 5 shows the speed 1502 and pressure 1501 of the piston portion 152.

In the example shown in Figure 5, the mold closing process begins at the mold closing start time. The pressure control unit 712 controls the movable platen 120 together with the piston portion 152 of the hydraulic cylinder 150 to a speed V1. Then, after the piston portion 152 reaches the mold protection position, the pressure control unit 712 switches the control performed on the piston portion 152 from speed control to pressure control. Pressure control is a control that prevents pressure above a predetermined limit value from being applied, and is also called low pressure control. The predetermined limit value is a pressure value lower than the pressure applied from the start of mold closing to the arrival at the mold protection position.

The determination unit 716 determines whether the time it takes for the movable platen 120 to reach the pressure increase start position (an example of a predetermined position) exceeds a monitoring time (an example of a predetermined time). In the example shown in Figure 5, it is assumed that an abnormality occurs at time t1, such as the mold device 800 trapping a foreign object. As a result, the speed 1502 of the movable platen 120 decreases together with the piston portion 152.

The judgment unit 716 judges that an abnormality has occurred if the monitoring time t2 is exceeded. In this way, no judgment is made until the monitoring time t2 has elapsed after the foreign object is trapped, but the effect of the foreign object having little effect on the mold device 800 due to the low pressure control is obtained.

The stop control unit 717 controls the servo motor 170 to stop when the judgment unit 716 judges that the time required to reach the boost start position (an example of a specified position) exceeds the monitoring time (an example of a specified time).

When the judgment unit 716 judges that the time taken to reach the pressure increase start position (an example of a predetermined position) has exceeded the monitoring time (an example of a predetermined time), the notification unit 718 notifies the operator using the injection molding machine 10, a monitoring center, etc., that an abnormality has occurred.

However, when the pressure applied to the piston portion 152 is reduced, as in the case of low pressure control by the pressure control portion 712, it becomes susceptible to the effects of friction, etc., and the completion time of the mold closing process varies. Therefore, in the low pressure control by the pressure control portion 712, the monitoring time t2 is set with a margin. When determining whether an abnormality has occurred based on such monitoring time t2, it may take a long time to detect the abnormality.

Therefore, the control device 700 of this embodiment enables speed control by the speed control unit 713 instead of pressure control by the pressure control unit 712.

Returning to Figure 4, the speed control unit 713 of this embodiment controls the speed of the hydraulic cylinder 150, which moves during the mold closing process, as well as the movable platen 120 fixed to the hydraulic cylinder 150.

Specifically, the speed control unit 713 of this embodiment controls the speed of the piston unit 152 and the movable platen 120 to a speed V1 from the start of the mold closing process until they reach the mold protection position. Then, after the piston unit 152 and the movable platen 120 reach the mold protection position, the speed control unit 713 controls the speed of the piston unit 152 and the movable platen 120 to a speed V2 (speed V2 < speed V1) until they reach the pressure increase start position. When the speed control unit 713 performs speed control, it determines whether or not there is an abnormality based on the pressure value detected by the pressure sensor 167. In other words, this embodiment is equipped with the above-mentioned hydraulic circuit 160, and therefore has high detection accuracy for the pressure value, making it possible to determine whether or not there is an abnormality based on the pressure value.

In addition, feedback control may be incorporated into the speed control unit 713 to control the speed of the piston portion 152 and the movable platen 120 so as to prevent variation.

The acquisition unit 715 acquires from the pressure sensor 167 a pressure value indicating the fluid pressure applied to the oil chamber 157 of the piston portion 152 due to movement of the piston portion 152 and the movable platen 120.

Furthermore, the acquisition unit 715 acquires the position of the piston portion 152 in the mold closing direction from a linear sensor (not shown) provided on the hydraulic cylinder 150. This makes it possible to recognize whether the piston portion 152 has reached the mold protection position or the temperature rise start position. The mold protection position is a position where the speed or pressure is reduced to protect the mold device 800. The temperature rise start position is a position (an example of a predetermined position) where the mold closing process is completed.

The determination unit 716 determines whether the pressure value acquired by the acquisition unit 715 exceeds the pressure threshold value stored in the threshold memory unit 710.

Figure 6 is a diagram showing an example of speed control in the speed control unit 713 according to this embodiment. Figure 6 shows the speed 1601 of the piston portion 152 and the pressure value 1602 of the fluid pressure acquired by the acquisition unit 715.

In the example shown in Figure 6, the mold closing process is started at the mold closing start time. The speed control unit 713 controls the movable platen 120 together with the piston portion 152 of the hydraulic cylinder 150 to move at a speed V1. Then, after the piston portion 152 reaches the mold protection position, the speed control unit 713 controls the movable platen 120 together with the piston portion 152 to move at a speed V2 (speed V2 < speed V1). By moving the movable platen 120 at such a low speed, it is possible to protect the movable mold 820 fixed to the movable platen 120.

The acquisition unit 715 acquires a pressure value P2 that is reduced from the pressure value P1 in accordance with the speed change by the speed control unit 713.

The threshold memory unit 710 stores a pressure threshold T1 until the mold protection position is reached and a pressure threshold T2 from the mold protection position until the pressure increase start position is reached for speed control by the speed control unit 713. In this way, the threshold memory unit 710 stores a predetermined pressure threshold according to the positions to which the movable platen 120 and the piston portion 152 have moved.

The determination unit 716 determines whether the pressure value acquired by the acquisition unit 715 exceeds the pressure threshold stored in the threshold storage unit 710. In this embodiment, the determination unit 716 makes a determination based on a predetermined pressure threshold for each position to which the movable platen 120 and the piston unit 152 move. Specifically, the determination unit 716 determines whether the acquired pressure value exceeds the pressure threshold T1 until the mold protection position is reached, and determines whether the acquired threshold exceeds the pressure threshold T2 from the mold protection position until the pressure increase start position is reached. In addition, in the case of speed control, as in pressure control, the determination unit 716 may determine whether an abnormality has occurred depending on whether the time until the pressure increase start position is reached exceeds the monitoring time.

6, at time t3, the determination unit 716 determines that the pressure value acquired by the acquisition unit 715 exceeds the pressure threshold value T2 stored in the threshold value storage unit 710. In this way, with the speed control of this embodiment, if a foreign object is trapped, an abnormality determination can be made immediately.

The stop control unit 717 performs control to stop the servo motor 170 when it is determined that the pressure value acquired by the determination unit 716 exceeds the pressure threshold value. Note that, in this embodiment, a case where control is performed to stop the servo motor 170 is described, but the present invention is not limited to control to stop the servo motor 170, and it is also possible to perform control to rotate the servo motor 170 in reverse, for example.

When the notification unit 718 determines that the pressure value acquired by the judgment unit 716 exceeds the pressure threshold value, it notifies the operator using the injection molding machine 10, a monitoring center, etc. that an abnormality has occurred.

Figure 7 is a flowchart showing the process of speed control in the mold closing process of the control device 700 according to this embodiment. Note that the pressure control may be performed using a method similar to that used in the past, and a description thereof will be omitted.

First, the control device 700 determines whether or not the mold closing process by speed control has started (S701). If it is determined that the mold closing process by speed control has not started (S701: No), the process ends.

When the control device 700 determines that the mold closing process by speed control has begun (S701: Yes), the speed control unit 713 controls the servo motor 170 to perform speed control so that the piston portion 152 moves to a speed V1 (S702).

The acquisition unit 715 acquires a pressure value indicating the fluid pressure applied to the oil chamber 157 of the piston portion 152 from the pressure sensor 167 (S703).

Until the mold protection position is reached, the determination unit 716 determines whether the pressure value acquired by the acquisition unit 715 exceeds the pressure threshold T1 (S704). If the determination unit 716 determines that the acquired pressure value exceeds the pressure threshold T1 (S704: Yes), the stop control unit 717 performs stop control on the servo motor 170, and the notification unit 718 notifies the user that an abnormality has occurred (S705), and the process ends.

On the other hand, if the determination unit 716 determines that the acquired pressure value does not exceed the pressure threshold T1 (S704: No), the acquisition unit 715 acquires the position of the piston portion 152 in the mold closing direction (S706). The determination unit 716 determines whether the position of the piston portion 152 acquired by the acquisition unit 715 has reached the mold protection position (S707). If it is determined that the mold protection position has not been reached (S707: No), the process is repeated from S702.

On the other hand, if the judgment unit 716 determines that the position of the piston portion 152 acquired by the acquisition unit 715 has reached the mold protection position (S707: Yes), the speed control unit 713 controls the servo motor 170 to perform speed control so that the piston portion 152 reaches speed V2 (S708).

The acquisition unit 715 acquires a pressure value indicating the fluid pressure applied to the oil chamber 157 of the piston portion 152 from the pressure sensor 167 (S709).

Until the mold protection position is reached, the determination unit 716 determines whether the pressure value acquired by the acquisition unit 715 exceeds the pressure threshold T2 (S710). If the determination unit 716 determines that the acquired pressure value exceeds the pressure threshold T2 (S710: Yes), the stop control unit 717 performs stop control on the servo motor 170, and the notification unit 718 notifies the user that an abnormality has occurred (S711), and the process ends.

On the other hand, if the determination unit 716 determines that the acquired pressure value does not exceed the pressure threshold T2 (S710: No), the acquisition unit 715 acquires the position of the piston portion 152 in the mold closing direction (S712). The determination unit 716 determines whether the position of the piston portion 152 acquired by the acquisition unit 715 has reached the temperature rise start position (S713). If it is determined that the position has not reached the mold protection position (S713: No), the process is repeated from S708.

On the other hand, if the judgment unit 716 determines that the position of the piston portion 152 acquired by the acquisition unit 715 has reached the temperature rise start position (S713: Yes), it terminates the processing.

As in the above-described processing procedure, in this embodiment, the speed of the piston portion 152 and the movable platen 120 is controlled from the mold protection position until they reach the pressure increase start position, and whether or not there is an abnormality is determined based on the pressure value detected by the pressure sensor 167. This allows for immediate detection of any abnormality, such as when a foreign object is trapped, thereby realizing protection of the mold device 800. Furthermore, in this embodiment, by performing the above-described speed control, it is possible to suppress variation in the end time of the mold closing process.

(Variation 1)
In the above embodiment, the speed control is performed at the speed V2 from the die protection position to the pressure increase start position. However, the speed control after the die protection position is not limited to one stage, and may be performed in multiple stages. Therefore, in this modified example, the speed control is performed in multiple stages after the die protection position.

Figure 8 is a diagram showing an example of speed control in the speed control unit 713 relating to variant example 1. Figure 8 shows the speed 1801 of the piston portion 152 and the pressure value 1802 of the fluid pressure acquired by the acquisition unit 715.

In the example shown in Figure 8, the mold closing process begins at the mold closing start time. The speed control unit 713 controls the piston portion 152 of the hydraulic cylinder 150 to have a speed V1. Then, when the piston portion 152 reaches the first mold protection position, the speed control unit 713 controls the piston portion 152 to have a speed V3 (speed V3 < speed V1).

Then, when it reaches the second mold protection position, the speed control unit 713 controls the piston portion 152 to have a speed V4 (speed V4 < speed V3), and when it reaches the third mold protection position, the speed control unit 713 controls the piston portion 152 to have a speed V5 (speed V5 < speed V4).

As shown in FIG. 8, the acquisition unit 715 detects a decrease in the pressure value 1202 detected by the pressure sensor 167 in accordance with the speed change by the speed control unit 713.

In this modified example, the pressure threshold 1803 stored in the threshold storage unit 710 is set to decrease according to the speed. For example, the threshold storage unit 710 stores a pressure threshold T1 from the start of mold closing to the arrival at the first mold protection position, a pressure threshold T3 from the arrival at the first mold protection position to the arrival at the second mold protection position, a pressure threshold T4 from the arrival at the second mold protection position to the arrival at the third mold protection position, and a pressure threshold T5 from the arrival at the third mold protection position to the arrival at the temperature rise start position.

Then, the determination unit 716 determines whether the pressure value acquired by the acquisition unit 715 exceeds a pressure threshold value (any one of pressure threshold values T1, T3, T4, and T5) stored in the threshold memory unit 710 that is associated with the position where the pressure value was detected.

8, at time t4 after arrival at the third mold protection position, the determination unit 716 determines that the pressure value acquired by the acquisition unit 715 has exceeded the pressure threshold T5 stored in the threshold memory unit 710. The processing performed when it is determined that the pressure value has exceeded the pressure threshold T5 stored in the threshold memory unit 710 is the same as in the embodiment described above, and therefore will not be described here.

(Variation 2)
In the above-described embodiment, an example has been described in which it is determined whether or not an abnormality has occurred based on whether or not the acquired pressure value is higher than the pressure threshold value stored in the threshold value storage unit 710. However, the threshold value used to determine whether or not an abnormality has occurred is not limited to the pre-stored pressure threshold value. Therefore, in Modification 1, an example will be described in which the pressure value is updated based on the actually acquired pressure value.

In this modified example, the acquisition unit 715 adds a predetermined value to the pressure value acquired this time, and associates the value with the position at which the pressure value was acquired as the next pressure threshold, and updates the threshold memory unit 710. The position at which the pressure value was acquired can be acquired from a linear sensor (not shown) provided on the hydraulic cylinder 150. The predetermined value is a value determined to allow for a margin when determining an abnormality, and may be any value according to the embodiment. The interval between positions at which pressure values are acquired is an interval determined according to the embodiment. This allows the pressure threshold to be updated for each position, taking friction, etc. into consideration, and improves the accuracy of abnormality detection.

In this modified example, the acquisition unit 715 has updated the threshold storage unit 710 with a value obtained by adding a predetermined value to the pressure value acquired this time (one shot) as the next pressure threshold. However, the present invention is not limited to a method of updating the next pressure threshold based on the pressure value of one shot, and the mold closing process may be performed multiple times (e.g., 10 times) and the threshold storage unit 710 may be updated with a moving average of the pressure values acquired by the acquisition unit 715 multiple times as the pressure threshold.

(Variation 3)
The above-described embodiment and modified examples have been described with reference to examples in which the pressure threshold is stored in the threshold storage unit 710. However, the pressure threshold is not limited to being a static parameter, and may be a dynamically generated parameter.

The determination unit 716 of this modified example holds a mathematical model representing the hydraulic circuit 160 and the hydraulic cylinder 150. The determination unit 716 then obtains the rotational speed of the servo motor 170 controlled by the speed control unit 713, and applies the rotational speed to the mathematical model to calculate an estimate of pressure indicating the fluid pressure generated in the hydraulic cylinder 150.

Then, the determination unit 716 determines whether the difference between the pressure value acquired by the acquisition unit 715 and the estimated pressure value is equal to or greater than a predetermined value. The determination unit 716 determines that an abnormality has occurred when the difference between the pressure value acquired by the acquisition unit 715 and the estimated pressure value is equal to or greater than a predetermined value. In this modified example, an example using a combination of the estimated pressure value and a predetermined value is described, but an abnormality detection similar to that using the pressure threshold value shown in the above-mentioned embodiment and modified example can be realized. Furthermore, when a determination is made using a combination of the estimated pressure value and a predetermined value, in addition to the same effects as the above-mentioned embodiment, an abnormality determination can be made with higher accuracy taking into account the rotation speed of the servo motor.

In the above-described embodiment and modified example, the piping length can be reduced by forming the hydraulic circuit 160 into a closed circuit using the bidirectional rotary pump 164 and the servo motor 170. This can suppress disturbances, and improves the accuracy of anomaly detection based on the pressure value detected by the pressure sensor 167 when low-speed control is performed between the mold protection position and the temperature rise start position.

In this embodiment and the modified example, an example has been described in which an abnormality is detected based on the pressure value detected by the pressure sensor 167 when low-speed control is performed between the mold protection position and the temperature rise start position in a closed circuit such as the hydraulic circuit 160. However, the method of detecting an abnormality based on the pressure value detected by the pressure sensor 167 while low-speed control is performed between the mold protection position and the temperature rise start position is not limited to the example using the closed circuit described above, and may be applied to a conventional open-circuit hydraulic circuit.

In the above-described embodiment and modified examples, after the mold protection position, the speed control unit 713 performs speed control on the piston portion 152, thereby reducing the variation in the arrival time to the temperature rise start position.

In the above-described embodiment and modified example, when speed control is performed in the mold closing process, the judgment unit 716 judges whether or not the pressure value acquired from the pressure sensor 167 exceeds the pressure threshold value, thereby judging an abnormality such as the entrapment of a foreign object. This allows for quicker abnormality detection compared to the conventional judgment of whether or not the monitoring time has passed. In addition, since stop control can be performed more quickly than in the past, the mold device 800 can be protected.

Although the above describes an embodiment of the injection molding machine according to the present invention, the present invention is not limited to the above embodiment. Various changes, modifications, substitutions, additions, deletions, and combinations are possible within the scope of the claims. Naturally, these also fall within the technical scope of the present invention.

This application claims priority to Japanese Patent Application No. 2021-062344, filed on March 31, 2021, the entire contents of which are incorporated herein by reference.

10: Injection molding machine 100: Clamping device 110: Fixed platen 120: Movable platen 150: Hydraulic cylinder 160: Hydraulic circuit 170: Servo motor 700: Control device 710: Threshold memory unit 711: Input processing unit 712: Pressure control unit 713: Speed control unit 714: Switching unit 715: Acquisition unit 716: Determination unit 717: Stop control unit 718: Notification unit

Claims (6)

a fixed platen on which a fixed mold is mounted;
a movable platen on which a movable mold is mounted;
a mold clamping device that performs a mold closing step of moving the movable platen by a fluid pressure to bring the movable platen into contact with the fixed platen;
a hydraulic cylinder for generating the fluid pressure;
A flow path connecting a plurality of oil chambers of the hydraulic cylinder;
a bidirectional rotary pump provided in the flow path;
A servo motor for controlling the rotation of the double rotary pump;
A control unit that controls the mold clamping device,
the mold clamping device is capable of switching a flow of oil flowing through the flow path based on a rotation direction of the bidirectional rotary pump,
The control unit is
a speed control unit that controls a speed of the movable platen in the mold closing process;
an acquisition unit that acquires a pressure value indicating the fluid pressure generated by the movement of the movable platen;
a determination unit that determines whether the pressure value acquired by the acquisition unit exceeds a predetermined threshold value;
a motor control unit that controls an output of the servo motor in response to the pressure value;
An injection molding machine comprising: the determining unit performs a determination for each position to which the movable platen is moved based on the predetermined threshold value that is set in advance.
2. The injection molding machine according to claim 1. the determining unit determines whether a time taken for the movable platen to reach a predetermined position exceeds a predetermined time.
2. The injection molding machine according to claim 1. a pressure control unit that controls a pressure on the movable platen in the mold closing process;
a switching unit that switches between the pressure control by the pressure control unit and the speed control by the speed control unit when moving the movable platen in the mold closing step,
The determination unit, when performing the pressure control by the pressure control unit, determines whether a time taken to reach the predetermined position exceeds the predetermined time, and, when performing the speed control by the speed control unit, determines whether the pressure value acquired by the acquisition unit exceeds the predetermined threshold.
4. The injection molding machine according to claim 3 . A storage unit that stores the predetermined threshold value,
The predetermined threshold value stored in the storage unit is updated in accordance with the pressure value acquired by the acquisition unit.
2. The injection molding machine according to claim 1. the determination unit calculates an estimate of a pressure generated by movement of the movable platen from a rotation speed of the servo motor that generates the fluid pressure, and determines that the predetermined threshold has been exceeded when a difference between the estimated pressure value and the pressure value acquired by the acquisition unit is equal to or greater than a predetermined value.
2. The injection molding machine according to claim 1 .

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