CN112638616A

CN112638616A - Injection molding machine

Info

Publication number: CN112638616A
Application number: CN201980056432.5A
Authority: CN
Inventors: 堀田大吾; 大石洁; 横仓勇希; 松井佑树
Original assignee: Sumitomo Heavy Industries Ltd
Current assignee: Sumitomo Heavy Industries Ltd
Priority date: 2018-08-27
Filing date: 2019-08-26
Publication date: 2021-04-09
Also published as: JP7175674B2; CN116787722A; JP2020032544A; WO2020045359A1

Abstract

The invention provides an injection molding machine capable of shortening the time until the balance of shaft force becomes stable. An injection molding machine, comprising: a mold clamping device having a plurality of tie bars; and a connecting rod axial force adjusting device that adjusts the axial force of the connecting rod, the connecting rod axial force adjusting device having: an axial force detector that detects an axial force of the connecting rod; and an axial force control unit that controls the temperature of the tie bars based on a deviation between a detected value of the axial force of the tie bars and a set value, wherein the axial force detector is provided in the plurality of tie bars, the axial force control unit includes an axial force control command generation unit that generates a control command for raising the temperature of the tie bars when the detected value of the axial force of the tie bars is higher than the set value, and the axial force control command generation unit performs a deviation reduction process for reducing the deviation between the detected value and the set value and reduces a decrease amount of the temperature of the tie bars when the detected value of the axial force of the tie bars is lower than the set value.

Description

Injection molding machine

Technical Field

The present invention relates to an injection molding machine.

Background

The injection molding machine includes a mold clamping device for closing, clamping, and opening the mold. The mold clamping device has a plurality of tie bars that extend in accordance with a mold clamping force. The mold clamping force is dispersed and applied to the plurality of connecting rods, and the connecting rods extend. The force resisting the elongation of the connecting rod is referred to as the axial force.

For example, in the case of multi-piece molding, if the balance of the forces of pressing the molds is poor, the thickness of each molded product may be different. In order to solve this problem, a method of controlling the temperature of the connecting rod to improve the balance of the forces pressing the mold is being studied. Specifically, a method of raising/lowering the temperature of the connecting rod by a heater/cooler (for example, refer to patent document 1).

Here, the heating and cooling are switched over, and the controllability is deteriorated due to the discontinuity of the control. Therefore, it is preferable not to use a cooler but to change the connecting rod temperature only by "on"/"off" of the heater.

Prior art documents

Patent document

Patent document 1: japanese laid-open patent publication No. 2008-114513

Disclosure of Invention

Technical problem to be solved by the invention

However, in the (natural cooling) method of stopping the heater to lower the temperature of the connecting rod, it takes time to lower to a prescribed temperature. Therefore, there is a problem that the yield is lowered and the start-up time is prolonged.

The present invention has been made in view of the above problems, and a main object thereof is to provide an injection molding machine capable of shortening the time until the balance of axial forces becomes stable.

Means for solving the technical problem

In order to solve the above problem, according to an aspect of the present invention, there is provided an injection molding machine having:

a mold clamping device having a plurality of tie bars; and

a connecting rod axial force adjusting device for adjusting the axial force of the connecting rod, in the injection molding machine,

the connecting rod axial force adjusting device comprises:

an axial force detector that detects an axial force of the connecting rod; and

an axial force control unit for controlling the temperature of the connecting rod based on the deviation between the detected value of the axial force of the connecting rod and a set value,

the axial force detector is arranged on the plurality of connecting rods,

the axial force control unit includes an axial force control command generation unit that generates a control command for raising the temperature of the connecting rod when a detected value of the axial force of the connecting rod is higher than a set value,

when a detected value of the axial force of the connecting rod is lower than a set value, the axial force control command generation section performs a deviation reduction process of reducing a deviation of the detected value from the set value, and reduces a drop amount of the temperature of the connecting rod.

Effects of the invention

According to an aspect of the present invention, there is provided an injection molding machine capable of shortening the time until the balance of axial forces becomes stable.

Drawings

Fig. 1 is a diagram showing a state at the end of mold opening of an injection molding machine according to an embodiment.

Fig. 2 is a diagram showing a state of the injection molding machine according to an embodiment when clamping a mold.

Fig. 3 is a diagram showing a positional relationship of a tie bar of the injection molding machine according to the embodiment, and is a diagram of a fixed platen as viewed from a movable platen side.

Fig. 4 is a block diagram showing an example of axial force control of the injection molding machine according to the embodiment.

Fig. 5 is a block diagram showing another example of axial force control of the injection molding machine according to the embodiment.

Fig. 6 is a block diagram showing another example of the axial force control of the injection molding machine according to the embodiment.

Fig. 7 is a graph showing an example of the temperature and the mold clamping force of each tie rod in the axial force control of the injection molding machine according to the embodiment.

Detailed Description

Hereinafter, the embodiments for carrying out the present invention will be described with reference to the drawings, but the same or corresponding components are denoted by the same or corresponding reference numerals in the drawings, and the description thereof will be omitted.

Fig. 1 is a diagram showing a state at the end of mold opening of an injection molding machine according to an embodiment. Fig. 2 is a diagram showing a state of the injection molding machine according to an embodiment when clamping a mold. The injection molding machine includes a frame Fr, a mold clamping device 10, an operation device 70, a display device 80, a controller 90, and the like.

The controller 90 includes a CPU (Central processing Unit) 91 and a storage medium 92 such as a memory. The controller 90 controls the mold clamping unit 10, the operating unit 70, the display unit 80, and the like by causing the CPU91 to execute a program stored in the storage medium 92.

The controller 90 is connected to the operation device 70 and the display device 80. The operation device 70 receives an input operation by a user, and outputs a signal corresponding to the input operation to the controller 90. The display device 80 displays a display screen corresponding to an input operation in the operation device 70 under the control of the controller 90.

The display screen is used for setting the injection molding machine. The display screen is provided in plural, and is displayed in a switching manner or in a superimposed manner. The user operates the operation device 70 while viewing the display screen displayed on the display device 80, thereby performing setting (including input of set values) of the injection molding machine and the like.

The operation device 70 and the display device 80 may be formed of a touch panel, for example, and integrated together. The operation device 70 and the display device 80 of the present embodiment are integrated, but may be provided separately. A plurality of the operation devices 70 may be provided.

The mold clamping device 10 closes, raises, clamps, releases, and opens the mold of the mold device 30. The mold clamping device 10 includes a fixed platen 12, a movable platen 13, a toggle base 15, a tie bar 16, a toggle mechanism 20, and a mold clamping motor 21. Hereinafter, the moving direction of the movable platen 13 when the mold is closed (the right direction in fig. 1 and 2) is set to the front, and the moving direction of the movable platen 13 when the mold is opened (the left direction in fig. 1 and 2) is set to the rear.

The fixed platen 12 is fixed to the frame Fr. A fixed mold 32 is attached to a surface of the fixed platen 12 facing the movable platen 13.

The movable platen 13 is movable along a guide (e.g., a guide rail) 17 laid on the frame Fr, and is movable forward and backward with respect to the fixed platen 12. A movable mold 33 is attached to a surface of the movable platen 13 facing the fixed platen 12.

The movable platen 13 is moved forward and backward with respect to the fixed platen 12, thereby closing, clamping, and opening the mold. The fixed die 32 and the movable die 33 constitute a die apparatus 30.

The toggle seat 15 is connected to the fixed platen 12 with a gap therebetween, and is mounted on the frame Fr so as to be movable in the mold opening/closing direction. The toggle seat 15 may be movable along a guide laid on the frame Fr. The guide for the toggle seat 15 may also be the same as the guide 17 for the movable platen 13.

In the present embodiment, the fixed platen 12 is fixed to the frame Fr so as to oppose thereto, and the toggle seat 15 is movable in the mold opening/closing direction with respect to the frame Fr, but the toggle seat 15 may be fixed to the frame Fr so as to oppose thereto, and the fixed platen 12 may be movable in the mold opening/closing direction with respect to the frame Fr.

The tie bars 16 connect the fixed platen 12 and the toggle seats 15 with a gap therebetween. The connecting rod 16 has a plurality of rods. Each tie bar 16 extends in parallel with the mold opening and closing direction and in accordance with the mold clamping force.

The toggle mechanism 20 is disposed between the movable platen 13 and the toggle base 15. The toggle mechanism 20 is constituted by a crosshead 20a, a plurality of

links

20b, 20c, and the like. One link 20b is swingably attached to the movable platen 13, and the other link 20c is swingably attached to the toggle seat 15. These

links

20b and 20c are connected by a pin or the like so as to be freely bendable and stretchable. By advancing and retreating the crosshead 20a, the plurality of

links

20b and 20c flex and extend, and the movable platen 13 advances and retreats with respect to the toggle seat 15.

The mold clamping motor 21 is attached to the toggle seat 15. The mold clamping motor 21 advances and retracts the movable platen 13 by advancing and retracting the crosshead 20 a. A motion conversion mechanism that converts the rotational motion of the mold clamping motor 21 into a linear motion and transmits the linear motion to the crosshead 20a is provided between the mold clamping motor 21 and the crosshead 20 a. The motion conversion mechanism is constituted by, for example, a ball screw mechanism.

The mold clamping device 10 performs a mold closing process, a pressure raising process, a mold clamping process, a pressure releasing process, a mold opening process, and the like under the control of the controller 90. The injection molding machine repeatedly performs a metering process, a mold closing process, a pressure increasing process, a mold closing process, a filling process, a pressure maintaining process, a cooling process, a pressure releasing process, a mold opening process, an ejection process, and the like under the control of the controller 90, thereby repeatedly manufacturing a molded product. A series of operations for obtaining a molded product, for example, an operation from the start of a metering process to the start of the next metering process is also referred to as "shot" or "molding cycle". Also, the time required for 1 shot is also referred to as "molding cycle time" or "cycle time".

The one-shot molding cycle includes, for example, a metering step, a mold closing step, a pressure raising step, a mold closing step, a filling step, a pressure maintaining step, a cooling step, a pressure releasing step, a mold opening step, and an ejection step in this order. The sequence here is the order in which the respective steps start. The filling step, the pressure holding step, and the cooling step are performed during the mold clamping step. The end of the decompression process is consistent with the start of the mold opening process.

In the metering step, a metering motor of an injection device, not shown, is driven to rotate a screw of the injection device, not shown, at a set rotational speed, and the molding material is conveyed forward along a spiral groove of the screw. With this, the molding material is gradually melted. The screw is retracted as the liquid molding material is conveyed forward of the screw and accumulated in the front of a cylinder of an injection device, not shown.

In the mold closing step, the movable platen 13 is moved forward by driving the mold clamping motor 21 to move the crosshead 20a forward to the mold closing end position at the set moving speed, and the movable mold 33 is brought into contact with the fixed mold 32.

In the pressure raising step, the mold clamping motor 21 is further driven to further advance the crosshead 20a from the mold closing end position to the mold clamping position, thereby generating a mold clamping force. When the mold is closed, a cavity space, not shown, is formed between the movable mold 33 and the fixed mold 32.

In the mold clamping step, the mold clamping force generated in the pressure increasing step is maintained.

In the filling step, the injection motor of the injection device is driven to advance the screw of the injection device at a set moving speed, and the cavity space in the mold device 30 is filled with the liquid molding material accumulated in front of the screw.

In the pressure holding step, an injection motor of an injection device (not shown) is driven to press the screw of the injection device forward, and the pressure of the molding material at the tip end portion of the screw (hereinafter also referred to as "holding pressure") is held at a set pressure, and the molding material remaining in the cylinder of the injection device is pushed toward the mold device 30. The molding material in the mold device 30 can be supplemented by an insufficient amount due to cooling shrinkage. The filling step and the pressure holding step are collectively referred to as an injection step.

After the pressure holding step, the cooling step is started. In the cooling step, the molding material in the cavity space is solidified. The metering step may be performed in the cooling step for the purpose of shortening the molding cycle time.

In the pressure releasing step, the movable platen 13 is moved backward to reduce the clamping force by driving the clamping motor 21 to move the crosshead 20a backward from the clamping position to the mold opening start position. The mold opening start position and the mold closing end position may be the same position.

In the mold opening step, the mold closing motor 21 is driven to retract the crosshead 20a from the mold opening start position to the mold opening end position at a set moving speed, thereby retracting the movable platen 13 and separating the movable mold 33 from the fixed mold 32.

In the ejection step, an ejection rod of an ejection device, not shown, is advanced from the standby position to the ejection position at a set moving speed, and thereby a movable member, not shown, of the mold device 30 is advanced to eject the molded product. Then, the ejector rod is retracted at a set moving speed, and the movable member is retracted to the original standby position.

When the thickness of the mold apparatus 30 changes due to, for example, replacement of the mold apparatus 30 or a change in temperature of the mold apparatus 30, the mold thickness is adjusted so that a predetermined mold clamping force is obtained at the time of mold clamping. In the mold thickness adjustment, for example, the interval L between the fixed platen 12 and the toggle seats 15 is adjusted so that the link angle of the toggle mechanism 20 becomes a predetermined angle at the time when the movable mold 33 contacts the mold in which the fixed mold 32 contacts.

The mold clamping device 10 includes a mold thickness adjusting mechanism 22. The die thickness adjusting mechanism 22 adjusts the die thickness by adjusting the interval L between the fixed platen 12 and the toggle seat 15. The timing of the mold thickness adjustment is performed, for example, during a period from after the end of the molding cycle to before the start of the next molding cycle. The die thickness adjusting mechanism 22 includes, for example, a screw shaft 22a formed at the rear end of the connecting rod 16, a screw nut 22b rotatably held by the toggle base 15 so as not to advance and retreat, and a die thickness adjusting motor 22c for rotating the screw nut 22b screwed with the screw shaft 22 a.

A screw shaft 22a and a screw nut 22b are provided to each connecting rod 16. The rotational driving force of the die thickness adjusting motor 22c can be transmitted to the plurality of lead screw nuts 22b via the rotational driving force transmitting portion 22 e. The plurality of lead screw nuts 22b can be rotated in synchronization. Further, the plurality of screw nuts 22b can be rotated independently by changing the transmission path of the rotational driving force transmission portion 22 e.

The rotational driving force transmission portion 22e is formed of, for example, a gear. At this time, a driven gear is formed on the outer periphery of each screw nut 22b, a drive gear is attached to the output shaft of the die thickness adjusting motor 22c, and an intermediate gear that meshes with the plurality of driven gears and the drive gear is rotatably held in the center portion of the toggle seat 15. The rotational driving force transmission portion 22e may be formed of a belt, a pulley, or the like instead of a gear.

The operation of the die thickness adjusting mechanism 22 is controlled by a controller 90. The controller 90 drives the thickness adjustment motor 22c to rotate the lead screw nut 22 b. As a result, the position of the toggle seats 15 with respect to the tie rods 16 is adjusted, and the interval L between the fixed platen 12 and the toggle seats 15 is adjusted. Further, a plurality of die thickness adjusting mechanisms may be used in combination.

The interval L is detected using the die thickness adjustment motor encoder 22 d. The mold thickness adjusting motor encoder 22d detects the rotation amount and the rotation direction of the mold thickness adjusting motor 22c, and sends a signal indicating the detection result to the controller 90. The detection result of the die thickness adjusting motor encoder 22d is used for monitoring and controlling the position and the interval L of the toggle seat 15. The toggle seat position detector for detecting the position of the toggle seat 15 and the interval detector for detecting the interval L are not limited to the mold thickness adjustment motor encoder 22d, and a conventional detector can be used.

Further, the mold clamping device 10 of the present embodiment includes the mold clamping motor 21 as a driving source for moving the movable platen 13, but may include a hydraulic cylinder instead of the mold clamping motor 21. The mold clamping device 10 may have a linear motor for opening and closing the mold, or may have an electromagnet for clamping the mold.

Fig. 3 is a diagram showing a positional relationship of a tie bar of the injection molding machine according to the embodiment, and is a diagram of a fixed platen as viewed from a movable platen side. The injection molding machine has 4 connecting rods 16. The 4 tie bars 16 are disposed vertically symmetrically about a horizontal line L1 and horizontally symmetrically about a vertical line L2 as viewed in the mold opening and closing direction. The upper side of the horizontal line L1 is referred to as the top surface side, and the lower side of the horizontal line L1 is referred to as the ground surface side. The side closer to operation device 70 than vertical line L2 is referred to as an operation side, and the side closer to the opposite side of operation device 70 than vertical line L2 is referred to as an opposite side.

The mold clamping force is applied to the 4 tie bars 16 in a dispersed manner, and each tie bar 16 is elongated. The force resisting the elongation of each tie rod 16 is referred to as an axial force. When there is a difference in the effective lengths of the 4 tie rods 16, a difference in the axial force occurs between the tie rod 16 having a short effective length and the tie rod 16 having a long effective length. Here, the effective length of the tie bar 16 is a distance between the fixed platen 12 and the toggle seat 15 connected by the tie bar 16, and is measured in a state where, for example, a mold clamping force is not applied.

By adjusting the effective length of the connecting rod 16, the balance of the axial forces can be adjusted. The balance of the axial forces is set so that, for example, the surface pressures of the fixed mold 32 and the movable mold 33 become a target distribution at the time of mold clamping. The target distribution may be either a uniform distribution or a non-uniform distribution, and is set according to the situation. Molding defects can be reduced.

The connecting rod 16 is formed of a metal material, and thus the effective length of the connecting rod 16 varies according to the temperature of the connecting rod 16. The higher the temperature of the connecting rod 16, the longer the effective length of the connecting rod 16. By adjusting the temperature of the connecting rod 16, the effective length of the connecting rod 16 can be adjusted, and the balance of the axial forces can be adjusted.

Therefore, as shown in fig. 1 and 2, a heater 25, a temperature detector 27, an axial force detector 28, and the like are attached to each tie rod 16. The heater 25, the temperature detector 27, the axial force detector 28, and the like are provided in the mold clamping device 10.

To adjust the effective length of the connecting rod 16, the heater 25 heats the connecting rod 16. A portion of the connecting rod 16 heated by the heater 25 is referred to as a heating portion. The heater 25 is formed of an electric heater such as a heater, for example. The heater 25 is not limited to an electric heater, and may be formed of, for example, a hot water jacket.

The temperature detector 27 detects the temperature of the connecting rod 16 heated by the heater 25 and cooled by natural cooling. For example, the temperature detector 27 is disposed in the vicinity of the heater 25, and detects the temperature of the heating portion of the connecting rod. The temperature detector 27 outputs the detection result to the controller 90.

The controller 90 controls the heater 25 so that the actual value of the temperature of the heating portion of the connecting rod 16 becomes the set value. The control may be either feedback control or feedforward control.

Further, the controller 90 of the present embodiment controls the heater 25.

The axial force detector 28 detects the axial force of the connecting rod 16 heated by the heater 25 and cooled by natural cooling. The axial force detector 28 is, for example, of the strain gauge type, and detects the axial force of the connecting rod 16 by detecting the strain of the connecting rod 16.

The axial force detector 28 of the above embodiment is of a strain gauge type, but may be of a piezoelectric type, a displacement type, a hydraulic type, an electromagnetic type, or the like.

The axial force detector 28 outputs the detection result to the controller 90. The controller 90 may set the heating temperature of the connecting rod 16 heated by the heater 25 so that the actual value of the axial force detected by the axial force detector 28 becomes the set value.

Here, in the injection molding machine according to one embodiment, when the temperature of the connecting rod 16 is raised, the heater 25 is operated to raise the temperature. On the other hand, when the temperature of the connecting rod 16 is lowered, the heater 25 is stopped, and the temperature is lowered by natural cooling (natural heat dissipation and heat conduction to other components). In this way, the temperature of the connecting rod 16 can be changed only by turning "on"/"off" of the heater 25, and therefore, it is possible to prevent the control from becoming discontinuous and to prevent the controllability from deteriorating.

However, the response speed when the temperature of the connecting rod 16 is lowered by such a structure becomes slower than the response speed when the temperature is raised. When the temperature of the connecting rod 16 is lowered, the temperature cannot be lowered to a predetermined temperature (for example, atmospheric temperature or the like) or lower.

Next, the axial force control of the injection molding machine according to the embodiment will be described with reference to fig. 4. Fig. 4 is a block diagram showing an example of axial force control of the injection molding machine according to the embodiment.

The axial force command unit 910 is provided to the controller 90, for example. The axial force command unit 910 gives an axial force command (axial force set value) to each link 16 to the axial force control unit 920. Regarding the 4 links 16 shown in fig. 3, the upper left is set as the 1 st link, the lower left is set as the 2 nd link, the upper right is set as the 3 rd link, and the lower right is set as the 4 th link. The operator inputs the axial force set values of the 1 st to 4 th connecting rods to the controller 90 via the operation device 70. Thus, the shaft force command unit 910 outputs the shaft force set value Ncmd1 of the 1 st link, the shaft force set value Ncmd2 of the 2 nd link, the shaft force set value Ncmd3 of the 3 rd link, and the shaft force set value Ncmd4 of the 4 th link to the shaft force control unit 920 as shaft force commands.

The axial force control unit 920 is provided in the controller 90, for example. The axial force control unit 920 controls the temperature of the connecting rod 16 by controlling the heater 25 based on the axial force set values (Ncmd1 to Ncmd4) of the axial force command unit 910 and the axial force detection values (Nfb1 to Nfb4 described later) detected by the axial force detector 28.

The axial force control unit 920 includes a temperature command generation unit 921, a current command generation unit 922, a temperature calculation unit 923, an axial force calculation unit 924,

calculators

925 and 926, and a correction calculation unit 927.

The arithmetic unit 925 receives the axial force set values (Ncmd1 to Ncmd4) of the respective tie rods 16 from the axial force command unit 910, receives the axial force detection values (Nfb1 to Nfb4) of the respective tie rods 16 from the axial force calculation unit 924 described later, and outputs the differences (Ncmd1 to Nfb1, and Ncmd4 to Nfb4) between the axial force set values and the axial force detection values of the respective tie rods 16.

The temperature command generation unit 921 calculates the temperature change amount of each connecting rod 16 so that the deviation between the axial force set value and the axial force detection value becomes small, based on the output value of the arithmetic unit 925 (deviation reduction processing). For example, the temperature command generating unit 921 has a data table indicating the relationship between the temperature rise and the axial force rise of the connecting rod 16. The data table is configured to reduce the axial force as the temperature of the connecting rod 16 increases. The temperature command generation unit 921 calculates the temperature change amount of each connecting rod 16 using the difference between the axial force set value and the axial force detection value, for example, from a data table. That is, when the shaft force detection value is lower than the shaft force set value, a temperature change amount that reduces the temperature of the connecting rod 16 is calculated. On the other hand, when the shaft force detection value is higher than the shaft force setting value, a temperature change amount that raises the temperature of the connecting rod 16 is calculated.

The temperature command generation unit 921 generates a new target temperature of each tie rod 16 based on the temperature change amount of each tie rod 16 and the current target temperature of each tie rod 16. The temperature command generating unit 921 outputs the generated target temperatures (the target temperature Tcmd1 of the 1 st link, the target temperature Tcmd2 of the 2 nd link, the target temperature Tcmd3 of the 3 rd link, and the target temperature Tcmd4 of the 4 th link) to the arithmetic unit 926 as a temperature command.

The calculator 926 receives the target temperature (Tcmd1 to Tcmd4) of each connecting rod 16 from the temperature command generation unit 921, receives the temperature detection value (Tfb1 to Tfb4) of each connecting rod 16 from the temperature calculation unit 923, which will be described later, and outputs the difference between the target temperature and the temperature detection value (Tcmd1 to Tfb1, Tcmd4 to Tfb4) of each connecting rod 16.

The current command generation unit 922 outputs a control signal to the relay 25b corresponding to the heater 25 of each tie rod 16 so as to reduce the deviation between the target temperature and the temperature detection value, based on the output value of the arithmetic unit 926. The relay 25b controls the supply of electric power from the heater power supply 25a to the heater 25 in accordance with the control signal of the current command generating unit 922. Here, when the temperature detection value is higher than the target temperature, the current command generation section 922 outputs a control signal for turning "off" the heater 25. When the temperature detection value is lower than the target temperature, the current command generation unit 922 outputs a control signal for turning "on" the heater 25. When the heater 25 is turned "on", the electric power supplied from the heater power supply 25a to the heater 25 may be controlled by changing the duty ratio of the control signal in accordance with the difference between the target temperature and the temperature detection value. The connecting rod 16 is heated by supplying electric power from the heater power supply 25a to the heater 25.

The temperature calculation unit 923 calculates the temperature of the connecting rod 16 based on the detection signal of the temperature detector 27. In addition, the temperature detectors 27 are provided to the respective tie bars 16. The calculated temperature of the connecting rod 16 (the temperature detection value Tfb1 of the 1 st connecting rod, the temperature detection value Tfb2 of the 2 nd connecting rod, the temperature detection value Tfb3 of the 3 rd connecting rod, and the temperature detection value Tfb4 of the 4 th connecting rod) is output to the arithmetic unit 926.

The axial force calculation unit 924 calculates the axial force of the connecting rod 16 based on the detection signal of the axial force detector 28. Further, the axial force detectors 28 are provided to the respective tie bars 16. The calculated axial force of connecting rod 16 (axial force detection value Nfb1 of the 1 st connecting rod, axial force detection value Nfb2 of the 2 nd connecting rod, axial force detection value Nfb3 of the 3 rd connecting rod, and axial force detection value Nfb4 of the 4 th connecting rod) is output to arithmetic unit 925.

The correction arithmetic unit 927 receives the difference between the target temperature and the temperature detection value of each connecting rod 16 (Tcmd1-Tfb1, Tcmd4-Tfb4) output from the arithmetic unit 926. The correction calculation unit 927 determines whether or not there is a tie bar 16 whose temperature is commanded to decrease among the 4 tie bars 16. Here, the command for temperature reduction is a command for reducing the temperature of the connecting rod 16, and means that the "target temperature-temperature detection value" which is an output from the arithmetic unit 926 is a negative value. The temperature increase command is a command for increasing the temperature of the connecting rod 16, and means that the "target temperature-temperature detection value" which is an output from the arithmetic unit 926 is a positive value.

When there is a connecting rod 16 whose temperature has been instructed to decrease, the correction arithmetic portion 927 outputs an instruction to decrease the shaft force set value to the shaft force instruction portion 910. For example, the output shaft force offset amount Ns. The axial force offset amount Ns may be a predetermined value or a value that changes in accordance with the temperature decrease amount (difference between the target temperature and the temperature detection value) of the connecting rod 16 for which a temperature decrease is instructed.

When receiving a command to decrease the axial force set value from the correction calculation unit 927, the axial force command unit 910 decreases the axial force set value of each link 16. For example, if Ns is the offset amount of the axial force that decreases the axial force set value, the axial force set value Ncmd1-Ns of the 1 st link, the axial force set value Ncmd2-Ns of the 2 nd link, the axial force set value Ncmd3-Ns of the 3 rd link, and the axial force set value Ncmd4-Ns of the 4 th link are output to the axial force control unit 920 as new axial force commands.

In this way, by decreasing the axial force set value of each connecting rod 16, the target temperature generated by the temperature command generation unit 921 becomes higher. For example, when the temperature offset amount corresponding to the axial force offset amount Ns is Ts, the temperature command generation unit 921 outputs the target temperature Tcmd1+ Ts of the 1 st link, the target temperature Tcmd2+ Ts of the 2 nd link, the target temperature Tcmd3+ Ts of the 3 rd link, and the target temperature Tcmd4+ Ts of the 4 th link to the arithmetic unit 926 as a new temperature command.

Thereby, the target temperature can be raised while maintaining the temperature difference of the target temperatures of the 4 connection rods 16. Since the temperature difference of the target temperatures of the 4 tie rods 16 can be maintained, it is possible to adjust the balance of the axial forces, for example, the vertical direction axial force balance (the relationship between the group of the 1 st and 3 rd tie rods and the group of the 2 nd and 4 th tie rods), the horizontal direction axial force balance (the relationship between the group of the 1 st and 2 nd tie rods and the group of the 3 rd and 4 th tie rods), and the torsional direction axial force balance (the relationship between the group of the 1 st and 4 th tie rods and the group of the 2 nd and 3 rd tie rods).

Further, since the target temperature of the connecting rod 16 whose temperature detection value is higher than the target temperature can be raised by the correction calculation unit 927, the amount of temperature decrease can be reduced, the time required for natural cooling can be reduced, and the responsiveness can be improved. Further, when the axial force offset amount Ns of the correction calculation unit 927 is increased, the temperature offset amount Ts is also increased, and the difference between the target temperature output from the calculator 926 and the temperature detection value can be set to 0 or more in all the connecting rods 16. Thus, the heater 25 having good responsiveness raises the temperature of the connecting rod 16, thereby enabling the axial force control, and therefore, the responsiveness is further improved.

The correction arithmetic unit 927 determines the presence or absence of a command for temperature decrease of the connecting rod 16 based on the output of the arithmetic unit 926, but may determine the presence or absence of a command for temperature decrease of the connecting rod 16 based on the output of the arithmetic unit 925. That is, when the "axial force set value-axial force detection value" that is the output from the arithmetic unit 925 is positive, the correction arithmetic unit 927 determines that the instruction to decrease the temperature of the connecting rod 16 is issued and the axial force set value is decreased.

As described above, in the axial force control shown in fig. 4, a configuration is shown in which the axial force set value is reduced in all the connecting rods 16 when the axial force detection value is lower than the axial force set value in any one of the connecting rods 16 (when the temperature detection value of the connecting rod 16 is higher than the target temperature). Another axial force control will be described with reference to fig. 5 and 6.

Fig. 5 is a block diagram showing another example of axial force control of the injection molding machine according to the embodiment. In the axial force control shown in fig. 5, a configuration is shown in which when the axial force detection value is lower than the axial force set value in any one of the connecting rods 16 (when the temperature detection value of the connecting rod 16 is higher than the target temperature), the axial force detection value is added (offset) in all the connecting rods 16.

The axial force control unit 920A includes a temperature command generation unit 921, a current command generation unit 922, a temperature calculation unit 923, an axial force calculation unit 924, calculators 925A and 926, and a correction calculation unit 927A. The axial force control unit 920A shown in fig. 5 is different from the axial force control unit 920 shown in fig. 4 in the configurations of a correction arithmetic unit 927A and an arithmetic unit 925A. The other structures are the same, and redundant description is omitted.

The correction arithmetic unit 927A receives the difference between the target temperature and the temperature detection value of each connecting rod 16 (Tcmd1-Tfb1, Tcmd4-Tfb4) output from the arithmetic unit 926. The correction calculation unit 927A determines whether or not there is a tie bar 16 whose temperature is commanded to decrease among the 4 tie bars 16. When there is a connecting rod 16 whose temperature is instructed to decrease, the correction arithmetic portion 927A outputs an instruction to increase (offset) the detected value of the axial force. For example, the output shaft force offset amount Ns. The axial force offset amount Ns may be a predetermined value or a value that changes in accordance with the temperature decrease amount (difference between the target temperature and the temperature detection value) of the connecting rod 16 for which a temperature decrease is instructed.

The calculator 925A receives the axial force set values (Ncmd1 to Ncmd4) of the respective tie rods 16 from the axial force command unit 910, receives the axial force detection values (Nfb1 to Nfb4) of the respective tie rods 16 from the axial force calculation unit 924, receives the axial force offset amount Ns from the correction calculation unit 927A, and outputs the difference between the axial force set value and the offset axial force detection value of the respective tie rods 16 (Ncmd1-Nfb1-Ns,... logan.. loganl., Ncmd4-Nfb 4-Ns).

According to this configuration, as in the case of the axial force control shown in fig. 4, the responsiveness can be improved while adjusting the balance of the axial forces in the axial force control shown in fig. 5.

Further, the correction arithmetic unit 927A determines the presence or absence of a command for temperature decrease of the connecting rod 16 based on the output of the arithmetic unit 926, but may determine the presence or absence of a command for temperature decrease of the connecting rod 16 based on the output of the arithmetic unit 925A. That is, when the "axial force set value — axial force detection value" that is the output from the arithmetic unit 925 is positive, the correction arithmetic unit 927A may determine that a command for decreasing the temperature of the connecting rod 16 is issued and increase the axial force detection value.

Fig. 6 is a block diagram showing another example of the axial force control of the injection molding machine according to the embodiment. In the axial force control shown in fig. 6, a configuration is shown in which when the axial force detection value is lower than the axial force set value in any one of the connecting rods 16 (when the temperature detection value of the connecting rod 16 is higher than the target temperature), the target temperature is increased (offset) in all the connecting rods 16.

The axial force control unit 920B includes a temperature command generation unit 921, a current command generation unit 922, a temperature calculation unit 923, an axial force calculation unit 924,

calculators

925, 926, 928B, and a correction calculation unit 927B. The axial force control unit 920B shown in fig. 6 is different from the axial force control unit 920 shown in fig. 4 in the configurations of the correction calculation unit 927B and the calculator 928B. The other structures are the same, and redundant description is omitted.

The correction arithmetic unit 927B receives the difference between the target temperature and the temperature detection value of each connecting rod 16 (Tcmd1-Tfb1, Tcmd4-Tfb4) output from the arithmetic unit 926. The correction calculation unit 927B determines whether or not there is a tie bar 16 whose temperature is commanded to decrease among the 4 tie bars 16. When there is a connecting rod 16 whose temperature is instructed to decrease, the correction arithmetic portion 927B outputs an instruction to increase the target temperature. For example, the temperature offset Ts is output. The temperature offset amount Ts may be a predetermined value or a value that changes in accordance with the amount of temperature decrease (difference between the target temperature and the temperature detection value) of the connecting rod 16 for which a temperature decrease is instructed.

The calculator 928B receives the target temperature (Tcmd1 to Tcmd4) of each connecting rod 16 from the temperature command generation unit 921, receives the temperature offset amount Ts from the correction calculation unit 927B described later, and outputs a new target temperature (Tcmd1+ Ts,. to.. and. Tcmd4+ Ts) of each connecting rod 16. The new target temperature (Tcmd1+ Ts,. and. Tcmd4+ Ts) is input to the arithmetic unit 926.

According to this configuration, as in the case of the axial force control shown in fig. 4, the responsiveness can be improved while adjusting the balance of the axial forces in the axial force control shown in fig. 6.

Further, the correction arithmetic unit 927B determines the presence or absence of a command for temperature decrease of the connecting rod 16 based on the output of the arithmetic unit 926, but may determine the presence or absence of a command for temperature decrease of the connecting rod 16 based on the output of the arithmetic unit 925. That is, when the "axial force set value — axial force detection value" that is the output from the arithmetic unit 925 is positive, the correction arithmetic unit 927B may determine that the command for decreasing the temperature of the connecting rod 16 is issued and raise the target temperature.

Fig. 7 is a graph showing an example of the temperature and the mold clamping force of each tie rod in the axial force control of the injection molding machine according to the embodiment. In the upper graph, the horizontal axis represents the number of shots, the vertical axis represents the temperature, T1 represents the temperature of the 1 st tie rod, T2 represents the temperature of the 2 nd tie rod, T3 represents the temperature of the 3 rd tie rod, and T4 represents the temperature of the 4 th tie rod. In the lower graph, the horizontal axis represents the number of shots, and the vertical axis represents the detected value of the mold clamping force during mold clamping. The vertical axis may be an average value of detected values of the clamping force in the clamping step. The vertical axis may be a maximum value of the clamping force in the clamping step. The mold clamping force is the sum of the axial forces of the 1 st to 4 th tie bars (Nfb1+ Nfb2+ Nfb3+ Nfb 4). That is, the axial force detector 28 also serves as a mold clamping force detector for detecting a mold clamping force.

The axial force control (control "on") of the injection molding machine according to the first embodiment is started. As shown in the above-described graph, the axial force control is performed so as to heat the connecting rod 16 or maintain the temperature. In the example shown in fig. 7, the temperature T1 of the 1 st connecting rod is maintained and the temperatures T2 to T4 of the 2 nd to 4 th connecting rods are raised. This adjusts the balance of the axial force and improves the responsiveness of the axial force control.

However, the command to lower the temperature of the connecting rod 16 is to lower the amount of temperature drop or raise the temperature by raising the target temperature. Generally, the reduction of the axial force of the connecting rod 16 sets the command to lower the temperature to an amount of reduction thereof, or an amount to raise the temperature. That is, the axial force is reduced by an amount corresponding to the temperature offset amount. As shown in the lower graph, the actual value of the mold clamping force decreases. When the actual value of the clamping force is smaller than the set value by a predetermined value or more, the controller 90 controls the thickness adjustment mechanism 22 to narrow the interval L so that the actual value of the clamping force approaches the set value, in other words, the position of the toggle seat 15 is advanced toward the fixed platen 12. This enables recovery of a desired mold clamping force (mold clamping force correction). The timing of the mold clamping force correction is performed, for example, after the molding cycle is completed and before the next molding cycle is started.

In the example shown in fig. 7, the axial force command is changed (command change) in the middle of the axial force control. In the example shown in fig. 7, the temperature T2 of the 2 nd connecting rod is maintained, and the temperatures T1, T3, T4 of the 1 st, 3 rd, 4 th connecting rods are raised.

When the difference between the detected axial force value and the set axial force value falls within a predetermined range, the correction calculation unit 927 reduces the temperature of the connecting rod 16 while maintaining the relative temperature difference between the 4 connecting rods 16, as shown in fig. 7. This can reduce the temperature of the connecting rod 16 while maintaining the balance of the shaft forces. Further, the axial force of each tie rod 16 is increased by the decrease in the temperature of the tie rod 16, and the mold clamping force can be recovered.

Although not shown, the correction calculation unit 927 may perform control so as to lower the target temperature when the temperature of the connecting rod 16 becomes equal to or higher than the predetermined 1 st threshold temperature. This can prevent the temperature of the connecting rod 16 from becoming excessively high. At this time, the relative temperature difference of the 4 connection rods 16 is maintained, and the temperature of the connection rods 16 is reduced. This can reduce the temperature of the connecting rod 16 while maintaining the balance of the shaft forces. When the temperature of the connecting rod 16 becomes equal to or lower than the predetermined 2 nd threshold temperature, the above-described axial force control may be restarted.

While the embodiment of the injection molding machine and the like have been described above, the present invention is not limited to the above embodiment and the like, and various modifications and improvements can be made within the scope of the gist of the present invention described in the claims.

The injection molding machine may be provided with a heating range limiting mechanism for limiting the heating range of the connecting rod 16 heated by the heater 25. The heating range limiting mechanism is constituted by, for example, coolers disposed on both sides in the axial direction of the connecting rod 16 via heaters 25. The cooler is constituted, for example, by a water-cooled jacket. The cooler is not limited to the water-cooled jacket, and may be formed of, for example, a heat sink. The cooling method of the fins may be either a forced air cooling method or a natural air cooling method using a cooling fan. The heating range restriction mechanism can restrict the movement of heat applied to the tie bar 16 by the heater 25, and can shorten the time until the temperature of the entire mold clamping apparatus 10 becomes stable and shorten the time until the balance of the axial forces becomes stable. Further, the thermal expansion range of the connecting rod 16 can be managed, the amount of change in the effective length due to a change in the temperature of the connecting rod 16 can be managed with high accuracy, and the axial force can be adjusted with high accuracy. The heating range restriction means is not limited to the cooler, and may have any configuration as long as it can restrict the movement of heat. That is, heat can be insulated between the heating range and the outside of the heating range.

The controller 90 controls the cooler in such a manner as to limit the heating range of the connecting rod 16. At this time, the controller 90 may control the cooler so that the actual value of the temperature of the cooling portion of the connecting rod 16 becomes the set value. The temperature of the cooling portion of the connecting rod 16 is detected by a temperature detector different from the temperature detector 27. The temperature detector is disposed in the vicinity of the cooler. The controller 90 performs temperature control by the heater 25 in a state where the heating range limiting mechanism is operated. That is, the temperature control by the heating range limiting mechanism and the heater 25 is performed at the same time.

The example in which the injection molding machine according to the embodiment is provided with the axial force detectors 28 for each of the 4 tie rods has been described, but the invention is not limited thereto. The tie bars 16 may be disposed at least above and below the die apparatus 30 and/or the tie bars 16 may be disposed on the left and right sides of the die apparatus 30. By providing the tie bars 16 disposed above and below the die apparatus 30 with the axial force detectors 28, it is possible to adjust the balance of the axial force in the vertical direction. By providing the axial force detectors 28 in the tie bars 16 arranged on the left and right sides of the die apparatus 30, it is possible to adjust the balance of the axial force in the horizontal direction. Further, the number of detectors can be reduced.

Further, the injection molding machine according to the embodiment has been described using the heater 25 controlled by the controller 90, and the axial force of the connecting rod 16 is adjusted not in a stable temperature but in a direction to heat the connecting rod 16. That is, a cooler controlled by the controller 90 may be provided instead of the heater 25, and the axial force of the connecting rod 16 may be adjusted not in a stable temperature but in a direction to cool the connecting rod 16.

Here, in the injection molding machine provided with a cooler instead of the heater 25, when the temperature of the connecting rod 16 is lowered, the cooler is operated to lower the temperature. On the other hand, when the temperature of the connecting rod 16 is raised, the temperature is raised by stopping the cooler. In this way, the temperature of the connecting rod 16 can be changed only by turning "on"/"off" of the cooler, and therefore, control discontinuity can be prevented, and deterioration of controllability can be prevented.

However, with this structure, the response speed when the temperature of the connecting rod 16 is raised becomes slower than that when the temperature is lowered. When the temperature of the connecting rod 16 is raised, the temperature cannot be raised to a predetermined temperature (for example, atmospheric temperature or the like) or higher.

At this time, if there is a connecting rod 16 whose temperature has been instructed to increase in any one of the connecting rods 16, the correction calculation unit increases the axial force set value in all the connecting rods 16. Further, when there is a connecting rod 16 whose temperature is instructed to increase in any one of the connecting rods 16, the correction calculation unit may decrease the detected axial force value in all the connecting rods 16. Further, when any of the tie rods 16 has a tie rod 16 whose temperature has been instructed to increase, the correction calculation unit may decrease the target temperature for all the tie rods 16.

Accordingly, the target temperature of the connecting rod 16 whose temperature detection value has become lower than the target temperature can be reduced by the correction calculation unit, and therefore the amount of temperature increase can be reduced, and the responsiveness can be improved while maintaining the balance of the axial forces.

The present application claims priority based on japanese patent application No. 2018-158629, filed on day 27, 8/2018, the entire contents of which are incorporated by reference in the present specification.

Description of the symbols

10-mold clamping device, 16-connecting rod, 22-mold thickness adjusting mechanism, 25-heater, 27-temperature detector, 28-axial force detector, 90-controller, 910-axial force instruction part, 920A, 920B-axial force control part, 921-temperature instruction generation part (axial force control instruction generation part), 922-current instruction generation part, 923-temperature calculation part, 924-axial force calculation part, 925A, 926, 928B-arithmetic unit, 927A, 927B-correction arithmetic part (axial force control instruction generation part).

Claims

1. An injection molding machine, comprising:

a mold clamping device having a plurality of tie bars; and

the connecting rod axial force adjusting device comprises:

an axial force detector that detects an axial force of the connecting rod; and

the axial force detector is arranged on the plurality of connecting rods,

2. The injection molding machine according to claim 1,

the axial force control portion has a heater that heats the connecting rod, and reduces the temperature of the connecting rod by stopping the heater.

3. The injection molding machine according to claim 1 or 2,

the axial force control command generation unit reduces the set value of the axial force when the detected value of the axial force of the connecting rod is lower than the set value.

4. The injection molding machine according to any one of claims 1 to 3,

the axial force control command generation unit increases the detected value of the axial force when the detected value of the axial force of the connecting rod is lower than a set value.

5. The injection molding machine according to any one of claims 1 to 4,

the axial force control command generation unit adds a control command for raising the temperature of the connecting rod when the detected value of the axial force of the connecting rod is lower than a set value.

6. The injection molding machine according to any one of claims 1 to 5,

the axial force control command generation unit generates a control command for reducing the temperature of the tie rod when a difference between a detected value of the axial force of the tie rod and a set value falls within a predetermined range.

7. The injection molding machine according to any one of claims 1 to 6,

the axial force control section has a connecting rod temperature detector that detects a temperature of the connecting rod,

the shaft force control command generating unit generates a control command for reducing the temperature of the connecting rod when the connecting rod temperature detector detects that the temperature of the connecting rod has increased to a predetermined temperature.

8. The injection molding machine according to claim 6 or 7,

the axial force control command generation unit generates a control command for lowering the temperature of each connecting rod while maintaining the temperature difference between the plurality of connecting rods.

9. The injection molding machine according to any one of claims 1 to 8,

the mold clamping device comprises a toggle mechanism for moving the movable platen forward and backward and a toggle seat for connecting the toggle mechanism,

the injection molding machine further includes a control unit for controlling the mold clamping unit,

when the actual value of the mold clamping force is smaller than the set value by a predetermined value or more because the tie bar is heated by the tie bar axial force adjustment device, the control unit changes the position of the toggle seat so that the actual value of the mold clamping force approaches the set value.

10. An injection molding machine, comprising:

a mold clamping device having a plurality of tie bars; and

the connecting rod axial force adjusting device comprises:

an axial force detector that detects an axial force of the connecting rod; and

the axial force detector is arranged on the plurality of connecting rods,

the axial force control unit includes an axial force control command generation unit that generates a control command for reducing the temperature of the connecting rod when a detected value of the axial force of the connecting rod is lower than a set value,

when a detected value of the axial force of the connecting rod is higher than a set value, the axial force control command generation section performs a deviation reduction process of reducing a deviation of the detected value from the set value, and reduces an amount of increase in temperature of the connecting rod.

11. The injection molding machine according to claim 10,

the axial force control portion has a cooler that cools the connecting rod, and raises the temperature of the connecting rod by stopping the cooler.

12. The injection molding machine according to any one of claims 1 to 11,

the axial force detector also serves as a mold clamping force detector for detecting a mold clamping force.

13. The injection molding machine according to any one of claims 1 to 12,

a plurality of tie bars are arranged around the die assembly,

the axial force detectors are disposed at least on tie bars disposed above and below the die device and/or on tie bars disposed on left and right sides of the die device, respectively.