CN108602225B

CN108602225B - Injection molding machine

Info

Publication number: CN108602225B
Application number: CN201780011349.7A
Authority: CN
Inventors: 羽野胜之; 王川; 水原弹; 常深浩基
Original assignee: Sumitomo Heavy Industries Ltd
Current assignee: Sumitomo Heavy Industries Ltd
Priority date: 2016-03-25
Filing date: 2017-03-27
Publication date: 2021-05-25
Anticipated expiration: 2037-03-27
Also published as: JP6721672B2; CN108602225A; WO2017164420A1; JPWO2017164420A1

Abstract

The injection molding machine of the invention comprises: the die mounting disc is provided with one of the fixed die and the movable die; a connecting plate connected to the die mounting plate at an interval in a die opening/closing direction; a die thickness adjusting mechanism for adjusting the die thickness by adjusting the interval; and a control device for controlling the die thickness adjusting mechanism, the die thickness adjusting mechanism having: a screw shaft formed on a rod connecting the die mounting plate and the connecting plate; a screw nut retained on one of the die mounting plate and the coupling plate; and a die thickness adjusting motor that rotates one of the screw shaft and the screw nut that are screwed together, wherein the control device stores a reference position of a position of the screw nut with respect to the screw shaft, and restores the position to the reference position if the position deviates from the reference position.

Description

Injection molding machine

Technical Field

The present invention relates to an injection molding machine.

Background

The injection molding machine described in patent document 1 includes: a screw shaft formed on a connecting rod connecting the fixed pressure plate and the toggle seat; a screw nut rotatably attached to the toggle seat; and a die thickness adjusting motor for rotating the screw nut screwed to the screw shaft. The injection molding machine drives the mold thickness adjusting motor to adjust the position of the toggle seat, thereby adjusting the mold thickness.

Prior art documents

Patent document

Patent document 1: japanese laid-open patent publication No. 2006 and 334944

Disclosure of Invention

Technical problem to be solved by the invention

However, after the completion of the die thickness adjustment, the position of the screw nut with respect to the screw shaft may be displaced, and the stability of the clamping force may be lowered.

The present invention has been made in view of the above problems, and a main object thereof is to provide an injection molding machine in which stability of mold clamping force is improved.

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 including: the die mounting disc is provided with one of a fixed die and a movable die; a connecting plate connected to the die mounting plate at an interval in a die opening/closing direction; a die thickness adjusting mechanism for adjusting the die thickness by adjusting the interval; and a control device for controlling the die thickness adjusting mechanism, the die thickness adjusting mechanism having: a screw shaft formed on a rod connecting the die mounting plate and the connecting plate; a screw nut retained on one of the die mounting plate and the coupling plate; and a die thickness adjusting motor that rotates one of the screw shaft and the screw nut that are screwed together, wherein the control device stores a reference position of a position of the screw nut with respect to the screw shaft, and restores the position to the reference position if the position deviates from the reference position.

Effects of the invention

According to an aspect of the present invention, there is provided an injection molding machine in which stability of mold clamping force is improved.

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 the embodiment at the time of mold clamping.

Fig. 3 is a flowchart showing an example of the processing of the control device performed after the die thickness adjustment is completed.

Fig. 4 is a flowchart showing a modification of the process of the control device performed after the die thickness adjustment is completed.

Fig. 5 is a diagram showing a temporal change in the position of the screw nut with respect to the screw shaft in the die thickness adjustment mechanism according to the embodiment.

Detailed Description

Hereinafter, a mode for carrying out the present invention will be described with reference to the drawings, and the same or equivalent structures are denoted by the same or equivalent reference numerals in the drawings to omit descriptions thereof.

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 when the injection molding machine according to the embodiment is clamped. As shown in fig. 1 and 2, the injection molding machine includes a frame Fr, a mold clamping device 10, an injection device 40, an ejector device 50, and a control device 90. In the following description, the moving direction of the movable platen 13 when the mold is closed (the right direction in fig. 1 and 2) is set as 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 as the rear.

The mold clamping device 10 closes, clamps, and opens the mold of the mold device 30. The mold clamping device 10 is of a horizontal type in which the mold opening and closing direction is horizontal. 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, a mold clamping motor 25, and a motion conversion mechanism 26.

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 advanced and retracted relative to the fixed platen 12, and mold closing, mold clamping, and mold opening are performed. The stationary mold 32 and the movable mold 33 constitute a mold apparatus 30.

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

In the present embodiment, the fixed platen 12 is fixed to the frame Fr, 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, 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 an interval L therebetween. A plurality of (e.g., 4) tie bars 16 may be used. Each tie bar 16 extends in parallel with the mold opening and closing direction and in accordance with the mold clamping force. At least 1 tie bar 16 is provided with a mold clamping force detector 18. The mold clamping force detector 18 detects deformation of the tie bar 16 to detect the mold clamping force, and sends a signal indicating the detection result to the control device 90.

The mold clamping force detector 18 is not limited to the strain gauge type, and may be of a piezoelectric type, a capacitive type, a hydraulic type, an electromagnetic type, or the like, and the attachment position thereof is not limited to the tie bar 16.

The toggle mechanism 20 moves the movable platen 13 relative to the fixed platen 12. The toggle mechanism 20 is disposed between the movable platen 13 and the toggle base 15. The toggle mechanism 20 is constituted by a cross head 21, a pair of links, and the like. Each link group includes a 1 st link 22 and a 2 nd link 23 connected by a pin or the like so as to be extendable and retractable. The 1 st link 22 is pivotally attached to the movable platen 13 by a pin or the like, and the 2 nd link 23 is pivotally attached to the toggle seat 15 by a pin or the like. The 2 nd link 23 is coupled to the crosshead 21 via the 3 rd link 24. When the crosshead 21 is advanced and retreated, the 1 st link 22 and the 2 nd link 23 expand and contract, and the movable platen 13 is advanced and retreated with respect to the toggle seat 15.

The structure of the toggle mechanism 20 is not limited to the structure shown in fig. 1 and 2. For example, in fig. 1 and 2, the number of nodes is 5, but may be 4, and one end of the 3 rd link 24 may be connected to the nodes of the 1 st link 22 and the 2 nd link 23.

The mold clamping motor 25 is attached to the toggle seat 15 and operates the toggle mechanism 20. The mold clamping motor 25 advances and retracts the crosshead 21, thereby extending and retracting the 1 st link 22 and the 2 nd link 23 and advancing and retracting the movable platen 13.

The motion conversion mechanism 26 converts the rotational motion of the mold clamping motor 25 into the linear motion of the crosshead 21. The motion conversion mechanism 26 includes a screw shaft and a screw nut screwed to the screw shaft. Balls or rollers may be interposed between the screw shaft and the screw nut.

The operation of the mold clamping device 10 is controlled by a control device 90. As shown in fig. 1 and 2, the control device 90 includes a cpu (central Processing unit)91, a storage medium 92 such as a memory, an input interface 93, and an output interface 94. The control device 90 causes the CPU91 to execute a program stored in the storage medium 92, thereby performing various controls. The control device 90 receives a signal from the outside through the input interface 93 and transmits a signal to the outside through the output interface 94. The controller 90 controls the mold closing process, mold opening process, and the like.

In the mold closing step, the mold clamping motor 25 is driven to advance the crosshead 21 to the mold closing end position at a set speed, and the movable platen 13 is advanced to bring the movable mold 33 into contact with the fixed mold 32. The position and speed of the crosshead 21 are detected by, for example, an encoder 25a of the mold clamping motor 25. The encoder 25a detects the rotation of the mold clamping motor 25, and transmits a signal indicating the detection result to the control device 90.

In the mold clamping step, the mold clamping motor 25 is further driven to further advance the crosshead 21 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 34 is formed between the movable mold 33 and the fixed mold 32, and the injection device 40 fills the cavity space 34 with a liquid molding material. The filled molding material is cured, thereby obtaining a molded article. The number of the cavity spaces 34 may be plural, and in this case, plural molded articles can be obtained at the same time.

In the mold opening step, the mold closing motor 25 is driven to retract the crosshead 21 to the mold opening completion position at a set speed, and the movable platen 13 is retracted to separate the movable mold 33 from the fixed mold 32. After that, the ejector 50 ejects the molded product from the movable mold 33.

The toggle mechanism 20 increases the driving force of the mold clamping motor 25 and transmits the increased driving force to the movable platen 13. This increased magnification is also referred to as the wrist magnification. The toggle magnification is changed according to an angle θ formed by the 1 st link 22 and the 2 nd link 23 (hereinafter, also referred to as "link angle θ"). The link angle θ is obtained from the position of the crosshead 21. The toggle magnification is at a maximum when the link angle θ is 180 °.

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, the interval L between the fixed platen 12 and the toggle seat 15 is adjusted so that the link angle θ of the toggle mechanism 20 becomes a predetermined angle when the movable mold 33 contacts the mold of the fixed mold 32, for example.

The mold clamping device 10 includes a mold thickness adjusting mechanism 60 for adjusting the mold thickness by adjusting the distance L between the fixed platen 12 and the toggle seat 15. The die thickness adjusting mechanism 60 includes: a screw shaft 61 formed at the rear end of the connecting rod 16; a screw nut 62 rotatably held by the toggle seat 15; and a die thickness adjusting motor 63 for rotating the screw nut 62 screwed to the screw shaft 61.

Each connecting rod 16 is provided with a screw shaft 61 and a screw nut 62. The rotation of the die thickness adjusting motor 63 can be transmitted to the plurality of screw nuts 62 via a rotation transmitting portion 64 configured by a belt, a pulley, and the like. The plurality of lead screw nuts 62 can be rotated in synchronization. Further, the plurality of screw nuts 62 may be rotated by changing the transmission path of the rotation transmission portion 64.

The rotation transmitting portion 64 may be formed of a gear or the like instead of a belt or a pulley. In this case, a driven gear is formed on the outer periphery of each screw nut 62, a drive gear is attached to the output shaft of the die thickness adjusting motor 63, 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 operation of the die thickness adjusting mechanism 60 is controlled by the control device 90. The controller 90 drives the thickness adjustment motor 63 to rotate the screw nut 62, thereby adjusting the position of the toggle seat 15 holding the screw nut 62 rotatably with respect to the fixed platen 12 and adjusting the interval L between the fixed platen 12 and the toggle seat 15.

In the present embodiment, the screw nut 62 is rotatably held by the toggle seat 15, and the connecting rod 16 on which the screw shaft 61 is formed is fixed to the fixed platen 12, but the present invention is not limited to this.

For example, the screw nut 62 may be rotatably held by the fixed platen 12, and the connecting rod 16 may be fixed to the toggle seat 15. In this case, the interval L can be adjusted by rotating the screw nut 62.

Further, the screw nut 62 may be fixed to the toggle seat 15, and the connecting rod 16 may be rotatably held by the fixed platen 12. In this case, the interval L can be adjusted by rotating the connecting rod 16.

Further, the screw nut 62 may be fixed to the fixed platen 12, and the connecting rod 16 may be rotatably held by the toggle seat 15. In this case, the interval L can be adjusted by rotating the connecting rod 16.

The die thickness adjusting mechanism 60 adjusts the interval L by rotating one of a screw shaft 61 and a screw nut 62 that are screwed together. A plurality of die thickness adjusting mechanisms 60 may be used, or a plurality of die thickness adjusting motors 63 may be used.

Here, the fixed platen 12 corresponds to a die mounting plate described in the technical scope, the toggle seats 15 correspond to a coupling plate described in the technical scope, and the connecting rods 16 correspond to rods described in the technical scope.

The controller 90 detects the mold contact of the movable mold 33 with the fixed mold 32 by driving the mold thickness adjusting motor 63 with the mold clamping motor 25 stopped, for example, while setting the link angle θ of the toggle mechanism 20 to a predetermined angle. The interval L between the fixed platen 12 and the toggle seat 15 when the mold contact is detected is set to the target interval L0 (not shown).

The detection of the die contact is performed, for example, during a period from a state in which the movable die 33 is separated from the fixed die 32 to a state in which the die thickness adjustment motor 63 is driven to advance the toggle seat 15 and advance the movable platen 13 coupled to the toggle seat 15. That is, the detection of the die-contact is performed by the closing of the die apparatus 30.

When the movable mold 33 contacts the fixed mold 32, the mold clamping force starts to rise. Therefore, the control device 90 monitors the mold clamping force during driving of the mold thickness adjusting motor 63, and detects mold contact based on the mold clamping force. The controller 90 may determine that mold contact has been made, for example, when the detection value of the mold clamping force detector 18 becomes a threshold value. The time difference of the detection value of the clamping force detector 18 may be used for this determination.

When the movable mold 33 contacts the fixed mold 32, the torque of the mold thickness adjusting motor 63 starts to increase. Therefore, the control device 90 can monitor the torque of the die thickness adjusting motor 63 during driving of the die thickness adjusting motor 63 and detect die contact based on the torque. Control device 90 may determine that the mold contact is performed when the detection value of torque detector 65 becomes a threshold value. This determination may be made by using the time difference of the detection value of torque detector 65.

The controller 90 detects the die contact by closing the die device 30 by the die thickness adjusting motor 63, but may detect the die contact by depressurizing the die device 30 by the die thickness adjusting motor 63. The decompression of the mold device 30 is started from the mold-closed state. It is possible to determine that the state of the mold apparatus 30 has returned to the mold-contacting state when the detection value of the mold-clamping-force detector 18 becomes the threshold value. Alternatively, it may be determined that the state of the mold apparatus 30 is restored to the mold-contacting state when the detection value of the torque detector 65 becomes the threshold value.

For detecting the mold contact, only one of the mold clamping force detector 18 and the torque detector 65 may be used, or both may be used.

The control device 90 stops the driving of the die thickness adjusting motor 63 after the die thickness adjustment is completed.

Since the molding operation is repeated after the completion of the mold thickness adjustment, the mold clamping motor 25 repeats the pressure increase and pressure reduction of the mold device 30, and the screw nut 62 is pushed rearward when the mold device 30 is pressurized and the screw nut 62 is pushed forward when the mold device 30 is depressurized. As a result, after the die thickness adjustment is completed, the position of the screw nut 62 with respect to the screw shaft 61 (hereinafter, simply referred to as "the position of the screw nut 62") may be displaced.

Therefore, the control device 90 stores the position of the lead screw nut 62 at the end of the die thickness adjustment as a reference position, and monitors the position of the lead screw nut 62. The position of the screw nut 62 is detected using, for example, an encoder 63a of the die thickness adjusting motor 63. The encoder 63a detects the rotation angle, rotation speed, rotation direction, and the like of the mold thickness adjusting motor 63, and transmits a signal indicating the detection result to the control device 90.

Fig. 3 is a flowchart showing an example of the processing of the control device performed after the die thickness adjustment is completed. The process shown in fig. 3 is performed, for example, after the mold opening is completed and before the mold closing is started. The control device 90 may perform the processing shown in fig. 3 every cycle, or may perform the processing periodically.

The controller 90 first determines whether the position of the lead screw nut 62 is not deviated from the reference position (step S11). The determination can be made as follows: when the misalignment of the screw nut 62 exceeds the allowable range, it is determined that the position of the screw nut 62 is deviated from the reference position; when the displacement of the screw nut 62 is within the allowable range, it is determined that the position of the screw nut 62 is not deviated from the reference position. The allowable range is set in advance based on the detection accuracy of the encoder 63a, the allowable range of variation in the clamping force, and the like.

If the position of the lead screw nut 62 is not deviated from the reference position (NO in step S11), the control device 90 proceeds to step S13 and performs the processing after step S13.

On the other hand, when the position of the screw nut 62 is deviated from the reference position (YES in step S11), the controller 90 drives the die thickness adjusting motor 63 to return the position of the screw nut 62 to the reference position (step S12). Restoring the position of the lead screw nut 62 to the reference position includes moving the misalignment of the lead screw nut 62 from outside the allowable range to within the allowable range. By returning the position of the screw nut 62 to the reference position, the stability of the mold clamping force can be improved. By returning the position of the screw nut 62 to the reference position, it is possible to prevent the displacement of the screw nut 62 from accumulating and increasing the variation in the mold clamping force.

This effect is more remarkable when a motor without a brake is used as the die thickness adjusting motor 63 instead of a brake-attached motor that restricts rotation of the output shaft when the drive is stopped. By using a motor without a brake, the motor can be reduced in size and cost.

However, after the completion of the mold thickness adjustment, the thickness of the mold device 30 may change due to a change in the temperature of the mold device 30 or the like. When the thickness of the mold device 30 changes, the mold clamping force varies. If the mold clamping force varies, the controller 90 performs a process of correcting the mold clamping force.

The controller 90 determines whether the variation in the mold clamping force is out of the allowable range (step S13). The deviation of the mold clamping force is a difference between a detected value of the mold clamping force and a set value of the mold clamping force. When the variation in the mold clamping force is within the allowable range (step S13, NO), the control device 90 ends the process of this time.

On the other hand, when the deviation of the mold clamping force exceeds the allowable range (YES at step S13), the controller 90 calculates the target displacement amount of the screw nut 62 based on the deviation of the mold clamping force (step S14). The relationship between the deviation of the mold clamping force and the target displacement amount is stored in the storage medium 92 in advance, and the controller 90 calculates the target displacement amount based on the deviation of the stored data and the mold clamping force. The larger the deviation of the mold clamping force, the larger the target displacement amount. The target displacement amount is calculated from the difference between the detected value of the clamping force at the current position of the screw nut 62 and the set value of the clamping force, and is calculated so that the difference becomes zero.

Next, the control device 90 corrects the reference position based on the calculated target displacement amount (step S15). The new reference position is obtained from the position at the time of calculation of the target displacement amount and the target displacement amount, and is set to a position shifted by the target displacement amount from the position at the time of calculation of the target displacement amount so that the difference between the detected value of the mold clamping force and the set value of the mold clamping force is zero. When the detected value of the mold clamping force is larger than the set value, the control device 90 changes the reference position in a direction in which the interval L between the toggle seat 15 and the fixed platen 12 becomes wider. On the other hand, when the detected value of the mold clamping force is smaller than the set value, the control device 90 changes the reference position in a direction in which the distance L between the toggle seat 15 and the fixed platen 12 becomes narrower.

Next, the controller 90 drives the die thickness adjustment motor 63 to shift the position of the lead screw nut 62 to the corrected reference position (step S16), and ends the process of this time. The position of the screw nut 62 is aligned with the corrected reference position, whereby the detected value of the mold clamping force is matched with the set value of the mold clamping force. This can further improve the stability of the clamping force.

The process performed by the control device 90 after the completion of the die thickness adjustment is not limited to the process shown in fig. 3. For example, the controller 90 may perform only steps S11 to S12, and may not perform the process of correcting the mold clamping force.

Fig. 4 is a flowchart showing a modification of the process of the control device performed after the die thickness adjustment is completed. The process shown in fig. 4 is performed, for example, after the mold opening is completed and before the mold closing is started. The control device 90 may perform the processing shown in fig. 4 every cycle, or may perform the processing periodically.

The controller 90 first determines whether or not mold clamping force correction is being performed using the reference position of the correction screw nut 62 (step S21). Whether or not the mold clamping force correction is used is switched by, for example, an input operation of a user.

When the mold clamping force correction is used (YES at step S21), the control device 90 determines whether or not the deviation of the mold clamping force exceeds the allowable range (step S13). When the deviation of the mold clamping force exceeds the allowable range (YES at step S13), the controller 90 proceeds to step S14 and performs the processing after step S14.

In step S14, the target displacement amount of the screw nut 62 is calculated from the difference in the mold clamping force as described above. The relationship between the deviation of the mold clamping force and the target displacement amount is stored in the storage medium 92 in advance, and the control device 90 calculates the target displacement amount from the stored data and the deviation of the mold clamping force. The larger the deviation of the mold clamping force, the larger the target displacement amount. The target displacement amount is calculated from the difference between the detected value of the clamping force at the current position of the screw nut 62 and the set value of the clamping force, and is calculated so that the difference becomes zero.

In step S15 following step S14, the reference position is corrected based on the calculated target displacement amount as described above. The new reference position is obtained from the position at the time of calculation of the target displacement amount and the target displacement amount, and is set to a position shifted by the target displacement amount from the position at the time of calculation of the target displacement amount such that the difference between the detected value of the mold clamping force and the set value of the mold clamping force is zero. When the detected value of the mold clamping force is larger than the set value, the control device 90 changes the reference position in a direction in which the interval L between the toggle seat 15 and the fixed platen 12 becomes wider. On the other hand, when the detected value of the mold clamping force is smaller than the set value, the control device 90 changes the reference position in a direction in which the distance L between the toggle seat 15 and the fixed platen 12 becomes narrower.

In step S16 following step S15, the thickness adjustment motor 63 is driven as described above to shift the position of the lead screw nut 62 to the corrected reference position. The position of the screw nut 62 is aligned with the corrected reference position, whereby the detected value of the mold clamping force is matched with the set value of the mold clamping force. This can further improve the stability of the clamping force. After step S16, control device 90 ends the process of this time.

On the other hand, when the mold clamping force correction is not used (steps S21, NO) or when the mold clamping force correction is used (steps S21, YES) and the variation in the mold clamping force is within the allowable range (steps S13, NO), the control device 90 proceeds to step S11 and performs the processing after step S11.

In step S11, it is determined whether or not the position of the lead screw nut 62 is deviated from the reference position as described above. The determination can be made as follows: when the positional deviation of the screw nut 62 exceeds the allowable range, it is determined that the position of the screw nut 62 is deviated from the reference position; when the positional deviation of the screw nut 62 is within the allowable range, it is determined that the position of the screw nut 62 is not deviated from the reference position. The allowable range is set in advance in accordance with the detection accuracy of the encoder 63a, the range of variation that can be tolerated by the mold clamping force, and the like.

In step S11, if the position of the lead screw nut 62 is not deviated from the reference position (step S11, NO), the control device 90 ends the process of this time.

On the other hand, in step S11, when the position of the lead screw nut 62 is deviated from the reference position (YES in step S11), the control device 90 proceeds to step S12.

In step S12, the thickness adjustment motor 63 is driven as described above to return the position of the lead screw nut 62 to the reference position. Restoring the position of the lead screw nut 62 to the reference position includes moving the misalignment of the lead screw nut 62 from outside the allowable range to within the allowable range. By returning the position of the screw nut 62 to the reference position, the stability of the mold clamping force can be improved. By returning the position of the screw nut 62 to the reference position, it is possible to prevent the displacement of the screw nut 62 from accumulating and increasing the variation in the mold clamping force.

Fig. 5 is a diagram showing a temporal change in the position of the screw nut with respect to the screw shaft in the die thickness adjustment mechanism according to the embodiment. The passage of time is indicated in figure 5 by the number of shots. The position of the screw nut 62 varies linearly in fig. 5, but may vary in a curved shape.

Since the molding operation is repeated after the completion of the mold thickness adjustment, the mold clamping motor 25 repeatedly increases and decreases the pressure of the mold device 30, and when the mold device 30 increases the pressure, the screw nut 62 is pushed rearward, and the toggle seat 15 is pushed rearward.

As a result, after the die thickness adjustment is completed, the position of the screw nut 62 with respect to the screw shaft 61 may be displaced. The position of the screw nut 62 is easily displaced in a direction in which the distance L increases as the toggle seat 15 is retracted.

Therefore, the control device 90 stores the position of the lead screw nut 62 at the end of the die thickness adjustment as the reference position 1, and monitors the position of the lead screw nut 62. The position of the screw nut 62 is detected using, for example, an encoder 63a of the die thickness adjusting motor 63. The encoder 63a detects the rotation angle, rotation speed, rotation direction, and the like of the mold thickness adjusting motor 63, and transmits a signal indicating the detection result to the control device 90.

The control device 90 monitors whether the position of the lead screw nut 62 deviates from the reference position 1. When the position of the screw nut 62 exceeds the allowable range of the reference position 1, it is determined that the position of the screw nut 62 is deviated from the reference position 1. On the other hand, when the position of the screw nut 62 is within the allowable range of the reference position 1, it is determined that the position of the screw nut 62 is not deviated from the reference position 1. The allowable range is set in advance based on the detection accuracy of the encoder 63a, the allowable range of variation in the clamping force, and the like.

As shown in fig. 5, the controller 90 drives the die thickness adjustment motor 63 to correct the position of the screw nut 62 each time it determines that the position of the screw nut 62 is deviated from the reference position 1. In fig. 5, the position correction of the screw nut 62 accurately restores the position of the screw nut 62 to the reference position 1, but the position of the screw nut 62 may be moved within the allowable range of the reference position 1. By shifting the position of the screw nut 62 within the allowable range of the reference position 1, the stability of the mold clamping force can be improved.

However, after the completion of the mold thickness adjustment, the thickness of the mold device 30 may change due to a change in the temperature of the mold device 30 or the like. The temperature of the mold apparatus 30 tends to increase with the passage of time, and therefore the thickness of the mold apparatus 30 tends to become thicker with the passage of time. However, the thickness of the mold device 30 may be reduced.

When the thickness of the mold device 30 changes, the mold clamping force may deviate from the target mold clamping force when the position of the screw nut 62 matches the reference position 1. Therefore, when the thickness of the mold device 30 is changed, the stability of the mold clamping force may be impaired if only the position of the screw nut 62 is monitored.

Here, the controller 90 may monitor not only the position of the screw nut 62 but also the mold clamping force. The mold clamping force is detected by a mold clamping force detector 18. The control device 90 monitors whether or not the detection value of the mold force is within the allowable range of the set value. When the detected value of the mold clamping force is within the allowable range of the set value, it is determined that the mold clamping force does not deviate from the target mold clamping force. On the other hand, when the detected value of the mold clamping force exceeds the allowable range of the set value, it is determined that the mold clamping force is deviated from the target mold clamping force.

When the controller 90 determines that the mold clamping force is deviated from the target mold clamping force, the reference position of the screw nut 62 is corrected to be changed from the reference position 1 to the reference position 2 as shown in fig. 5. The correction amount is set so that the mold clamping force matches the target mold clamping force when the position of the screw nut 62 matches the reference position 2. This allows the reference position of the screw nut 62 to be appropriately changed in response to a variation in the thickness of the die device 30, thereby maximizing the effect of monitoring the position of the screw nut 62.

After the reference position is corrected, the control device 90 monitors whether the position of the lead screw nut 62 is deviated from the reference position 2. When the position of the screw nut 62 exceeds the allowable range of the reference position 2, it is determined that the position of the screw nut 62 is deviated from the reference position 2. On the other hand, when the position of the screw nut 62 is within the allowable range of the reference position 2, it is determined that the position of the screw nut 62 is not deviated from the reference position 2. The allowable range is set in advance based on the detection accuracy of the encoder 63a, the allowable range of variation in the clamping force, and the like.

As shown in fig. 5, the controller 90 drives the die thickness adjustment motor 63 to correct the position of the screw nut 62 each time it determines that the position of the screw nut 62 is deviated from the reference position 2. In fig. 5, the position correction of the screw nut 62 accurately restores the position of the screw nut 62 to the reference position 2, but the position of the screw nut 62 may be moved within the allowable range of the reference position 2. By shifting the position of the screw nut 62 within the allowable range of the reference position 2, the stability of the mold clamping force can be improved.

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 mold clamping device 10 of the above embodiment is of a horizontal type in which the mold opening and closing direction is the horizontal direction, but may be of a vertical type in which the mold opening and closing direction is the vertical direction.

The vertical mold clamping device comprises a lower platen, an upper platen, a toggle seat, a connecting rod, a toggle mechanism, a mold clamping motor, a mold thickness adjusting mechanism and the like. Either one of the lower platen and the upper platen is used as a fixed platen, and the other is used as a movable platen. The lower pressing plate is provided with a lower die, and the upper pressing plate is provided with an upper die. The lower die and the upper die form a die device. The lower mold may be mounted to the lower platen via a rotary table. The toggle seat is arranged below the lower pressure plate. The toggle mechanism is arranged between the toggle seat and the lower pressing plate. The connecting rod is parallel to the vertical direction, penetrates through the lower pressing plate and is connected with the upper pressing plate and the toggle seat.

The vertical die thickness adjusting mechanism adjusts the gap between the upper platen and the toggle seat according to the change in the thickness of the die device, for example. In this die thickness adjustment, the interval between the upper platen and the toggle seat is adjusted so that the link angle of the toggle mechanism becomes a predetermined angle when the lower die contacts the die contacting the upper die. The link angle can be adjusted to a predetermined angle at the end of mold closing, and a predetermined mold clamping force can be obtained at the time of mold clamping. The die thickness adjusting mechanism comprises: a screw shaft formed at the connecting rod; a lead screw nut retained to one of the upper platen and the toggle seat; and a die thickness adjusting motor for rotating one of the screw shaft and the screw nut which are screwed together. The die thickness adjustment mechanism may further have a lead screw nut retained to the other of the upper platen and the toggle seat. The upper platen corresponds to a die mounting plate described in the technical scope, the toggle seats correspond to a connecting plate described in the technical scope, and the connecting rods correspond to rods described in the technical scope.

The mold clamping device 10 of the above embodiment includes the toggle mechanism 20 and the mold clamping motor 25 for operating the toggle mechanism 20, and may include a linear motor for mold opening and closing and an electromagnet for mold clamping.

The electromagnetic mold clamping device includes, for example, a fixed platen, a movable platen, a rear platen, a tie bar, an adsorption plate, a bar, a mold thickness adjusting mechanism, and the like. The rear platen is disposed on the opposite side of the fixed platen (i.e., behind the movable platen) with respect to the movable platen. The connecting rod connects the fixed pressing plate and the rear pressing plate with an interval along the mold opening and closing direction. The adsorption plate is freely advanced and retreated with the movable pressing plate at the rear part of the rear pressing plate. The rod is inserted through the through hole of the rear pressure plate and is connected with the movable pressure plate and the adsorption plate. An electromagnet is formed on at least one of the rear platen and the adsorption plate, and the adsorption force of the electromagnet acts between the rear platen and the adsorption plate to generate a mold clamping force.

The electromagnet type die thickness adjusting mechanism adjusts the die thickness by adjusting the interval between the movable platen and the adsorption plate. In this mold thickness adjustment, the distance between the movable platen and the suction plate is adjusted so that a predetermined gap is formed between the suction plate and the rear platen when the mold in which the movable mold contacts the fixed mold contacts. A predetermined gap can be formed between the suction plate and the rear platen at the end of mold closing, and a predetermined mold clamping force can be obtained at the time of mold clamping. The die thickness adjusting mechanism comprises: a screw shaft formed on the rod; a screw nut held by one of the movable platen and the suction plate; and a die thickness adjusting motor for rotating one of the screw shaft and the screw nut which are screwed together. The die thickness adjusting mechanism may further include a screw nut held by the other of the movable platen and the suction plate. The movable platen corresponds to the die mounting plate described in the technical scope, and the suction plate corresponds to the coupling plate described in the technical scope.

The present application claims priority from Japanese patent application No. 2016-.

Description of the symbols

10-mould clamping device

12-stationary platen

13-Movable platen

15-toggle seat

16-connecting rod

18-mold clamping force detector

20-toggle mechanism

21-crosshead

25-mold clamping motor

26-motion conversion mechanism

30-mould device

40-injection device

50-liftout attachment

60-die thickness adjusting mechanism

61-screw shaft

62-lead screw nut

63-die thickness adjusting motor

64-rotation transmitting part

65-Torque Detector

Claims

1. An injection molding machine, comprising: the die mounting disc is provided with one of a fixed die and a movable die; a connecting plate connected to the die mounting plate at an interval in a die opening/closing direction; a die thickness adjusting mechanism for adjusting the die thickness by adjusting the interval; and a control device for controlling the die thickness adjusting mechanism,

the die thickness adjusting mechanism has: a screw shaft formed on a rod connecting the die mounting plate and the connecting plate; a screw nut retained on one of the die mounting plate and the coupling plate; and a die thickness adjusting motor for rotating one of the screw shaft and the screw nut which are screwed together,

the control device stores the position of the screw nut with respect to the screw shaft at the time of completion of the die thickness adjustment as a reference position, monitors the position of the screw nut after the completion of the die thickness adjustment, and restores the position of the screw nut to the reference position when it is detected that the position of the screw nut is deviated from the reference position.

2. The injection molding machine according to claim 1,

the control device corrects the reference position based on a difference between a detected value of the mold clamping force and a set value of the mold clamping force.