JPH10244567A - Mold clamping device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To favorably and accurately control a mold clamping force during molding by providing a controlling device which controls, by feedback, the mold clamping force on the basis of the set mold clamping force and a load detected by a load detector. SOLUTION: A subtractor 68 calculates the difference between a load detected with a load detector 51 and a set mold clamping force command so as to output the calculated difference to an electromagnet controller 65, which generates a target mold clamping force corresponding to the difference so as to output a first and a second current command generators 66 and 67, which generates the respective current commands of respective currents fed to coils on the basis of the target mold clamping force so as to generate a mold clamping force between the first and the second electromagnets. Thus, the mold clamping force is controlled by feedback.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold clamping device.

[0002]

2. Description of the Related Art Conventionally, in an injection molding machine, a molten resin is injected from an injection nozzle of an injection device, and a fixed metal mold and a movable metal arranged to be able to advance and retreat with respect to the fixed metal mold. A molded product can be obtained by filling (solidifying) and solidifying the cavity space of a mold device composed of a mold. A mold clamping mechanism is provided for moving the movable mold to close, close, and open the mold of the mold apparatus.

[0003] The mold clamping mechanism includes a hydraulic mold clamping mechanism driven by supplying oil to a hydraulic cylinder, and an electric mold clamping mechanism driven by an electric motor. Tightening mechanisms are increasingly being used because they are not only highly controllable, but also clean and energy efficient. In this case, the electric motor is driven to rotate the ball screw to generate a thrust, and the thrust is expanded by a toggle mechanism to generate a large mold clamping force.

[0004]

However, in the above-mentioned conventional mold clamping mechanism, it is difficult to change the mold clamping force due to the characteristics of the toggle mechanism, and the responsiveness and stability are reduced. The mold clamping force cannot be controlled accurately. In addition, the toggle magnification characteristic of the toggle mechanism is greatly affected by the play, friction, thermal expansion, and the like of the toggle mechanism, and the mold clamping force cannot be generated accurately.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the problems of the conventional mold clamping mechanism and to provide a mold clamping device capable of accurately controlling a mold clamping force during molding.

[0006]

For this purpose, in the mold clamping apparatus of the present invention, a fixed platen, a fixed die attached to the fixed platen, and a predetermined distance from the fixed platen are arranged. A first electromagnet frame including a first electromagnet, a movable platen disposed to be able to advance and retreat along a tie bar provided between the fixed platen and the first electromagnet frame, and a movable platen. A second electromagnet frame including a movable mold attached thereto, a second electromagnet disposed opposite to the first electromagnet, and movably disposed with respect to the first electromagnet frame; ,
A link mechanism for connecting between the second electromagnet frame and the movable platen; an electric motor connected to the link mechanism for driving in the forward and reverse directions; and a movable platen via the link mechanism. It has a load detector for detecting an applied load, and a control device for performing feedback control of the mold clamping force based on the set mold clamping force and the load detected by the load detector.

The other mold clamping device of the present invention further has a position detecting means for detecting the position of the movable platen. Then, the control device performs feedback control of the position of the movable platen based on the set position and the position detected by the position detection unit.

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a first state diagram of the mold clamping device according to the embodiment of the present invention, and FIG. 2 is a second state diagram of the mold clamping device according to the embodiment of the present invention. In the figure, reference numeral 11 denotes a fixed platen, a first electromagnet frame 13 is provided at a predetermined distance from the fixed platen 11, and four first electromagnet frames 13 are provided between the fixed platen 11 and the first electromagnet frame 13. A tie bar 14 (only two tie bars 14 are shown in the figure) is installed.
A movable platen 12 is disposed along the tie bar 14 so as to face the fixed platen 11 so as to be able to advance and retreat (move in the left-right direction in the figure).

A fixed mold 15 is fixed to the fixed platen 11 and a movable mold 16 is fixed to the movable platen 12. The fixed mold 15 and the movable mold 16 are moved as the movable platen 12 advances and retreats. Are brought into and out of contact with each other. In addition,
When the fixed mold 15 and the movable mold 16 are brought into contact with each other, a cavity space (not shown) is formed between the fixed mold 15 and the movable mold 16, and the resin injected from an injection nozzle of an injection device (not shown) is formed. Is filled in the cavity space.

A first electromagnet 18 is fixed to the front surface (the right side in the figure) of the first electromagnet frame 13, and the first electromagnet 18 includes an electromagnetic laminated steel sheet 19 and a coil 21 for generating a magnetomotive force. . And the tie bar 14
The second electromagnet frame 20 is disposed so as to be movable along. A second electromagnet 22 is fixed to the back (left side in the figure) of the second electromagnet frame 20 so as to face the first electromagnet 18. The second electromagnet 22 is formed by an electromagnetic laminated steel sheet 23 and a magnetomotive force. From the coil 24 that generates the

A servomotor 27 with a reduction gear as an electric motor is connected to the front surface of the second electromagnet frame 20, and the servomotor 27 with the reduction gear and the movable platen 12
A single toggle type toggle mechanism 31 is provided as a link mechanism between them. The toggle mechanism 31 includes a first link 32 fixed to an output shaft 28 of the servomotor 27 with a speed reducer, a second link 33 supported swingably with respect to the movable platen 12, and a second link 33. And a pin 36 for connecting the first link 32 and the second link 33 to each other. Therefore, the toggle mechanism 31 is expanded and contracted by driving the servomotor 27 with a speed reducer, and the movable platen 12 and the movable mold 1 are moved.
The mold 6 can be advanced and retracted to open and close the mold.

On the other hand, a mold thickness adjusting nut 25 is provided on the back of the first electromagnet frame 13, and the mold thickness adjusting nut 2 is provided.
5 and a die thickness adjusting screw 14a formed at the rear end of the tie bar 14 are screwed together. Further, the mold thickness adjusting nut 25 is restrained by the first electromagnet frame 13 in the axial direction, and is moved together with the first electromagnet frame 13. Therefore, in a state where the toggle mechanism 31 is extended and the fixed mold 15 and the movable mold 16 are in contact with each other, a motor, a gear, and the like (not shown) are moved according to the thickness of the fixed mold 15 and the movable mold 16. The mold thickness can be adjusted by rotating the mold thickness adjusting nut 25 through the intermediary.

In this embodiment, a single toggle type toggle mechanism 31 is used, but a double toggle type toggle mechanism may be used. In the present embodiment, the rotation of the servomotor 27 with the speed reducer is directly transmitted to the toggle mechanism 31.
Other transmission means such as pulley belts, ball screws, etc. can also be used.

The first and second electromagnets 18, 2
2 are arranged to face each other, and at the time of mold clamping,
Currents in opposite directions are supplied to the coils 21 and 24 by a control device (not shown). At this time, the first and second electromagnets 18 and 22 have the same polarity to generate a repulsive force. The repulsive force is transmitted to the movable platen 12 as a mold clamping force via a toggle mechanism 31, and the mold clamping is performed. Is performed. Further, when the mold is closed and when the mold is opened, a current in the same direction is supplied to the coils 21 and 24 by the control device. At this time, the first and second electromagnets 18 and 22 have different polarities to generate an attractive force, and the attractive force prevents the first and second electromagnets 18 and 22 from separating. In this case, the required suction force may be sufficiently smaller than the mold clamping force. Therefore, current can be supplied to only one of the coils 21 and 24, and one of the first and second electromagnets 18 and 22 can be used as an attraction plate.

A load detector 5 for detecting a load applied to the movable platen 12 via the toggle mechanism 31 is provided between the toggle mechanism 31 and the movable platen 12.
1 is provided. The second electromagnet frame 20
In order to detect the position of the movable platen 12 with respect to the position, a position detector 52 as position detecting means is provided. The position detector 52 is fixed to the second electromagnet frame 20 and is fixed to the bar 53 protruding toward the fixed platen 11 and the movable platen 12.
3 comprises a sensor 54 for detecting the presence or absence of 3. Note that a load detector 51 may be provided between the second electromagnet frame 20 and the toggle mechanism 31. Further, the position of the second electromagnet frame 20 with respect to the movable platen 12 can be detected by fixing the bar 53 to the movable platen 12 and fixing the sensor 54 to the second electromagnet frame 20.

Next, a mold opening / closing control section and a mold clamping force control section of the control device will be described. FIG. 3 is a block diagram of a mold opening / closing control unit of the control device according to the embodiment of the present invention.
FIG. 2 is a block diagram of a mold clamping force control unit of the control device according to the embodiment of the present invention. In FIG. 3, 27 is a servomotor with a reduction gear, 52 is a position detector, 55 is a controller,
56 is a position setting device, and 57 is a subtractor.

The position setting device 56 generates position commands for closing and opening the mold based on the mold opening position and the set speed set by the operator, and outputs the position commands to the subtractor 57. . Then, the subtracter 57 obtains a difference between the position of the movable platen 12 (FIG. 1) detected by the position detector 52 and the position command, and outputs the difference to the controller 55. The controller 55
The servomotor 27 with a speed reducer is driven in accordance with the difference to rotate the first link 32 to move the movable platen 12 to the target position. In this manner, the mold opening / closing control section can perform feedback control of the position of the movable platen 12. In this case, since the position of the movable platen 12 is feedback-controlled, the mold can be closed and opened with high accuracy. A rotation angle detector (not shown) may be provided on the output shaft 28 as position detection means, and the position of the movable platen 12 may be detected according to the rotation angle of the output shaft 28 detected by the rotation angle detector. .

In FIG. 4, reference numeral 51 denotes a load detector,
61 is a mold clamping force setter, 65 is an electromagnet controller, 66
Is a first current command generator for generating a current command consisting of the value and direction of the current supplied to the coil 21 (FIG. 1);
7 is a second current command generator for generating a current command consisting of the value and direction of the current supplied to the coil 24, and 68 is a subtractor.

The mold clamping force setting unit 61 generates a mold clamping force command based on the mold clamping force and the operation time set by the operator, and outputs the mold clamping force command to the subtractor 68. Then, the subtracter 68 obtains a difference between the load detected by the load detector 51 and the mold clamping force command, and outputs the difference to the electromagnet controller 65.
The electromagnet controller 65 generates a target mold clamping force in accordance with the difference, and outputs the target mold clamping force to the first and second current command generators 66 and 67. The first and second current command generators 66 and 67 generate current commands for respective currents supplied to the coils 21 and 24 based on the target mold clamping force, and generate first and second electromagnets. A mold clamping force is generated between 18 and 22. As described above, the mold clamping force control section can perform feedback control of the mold clamping force.

Next, the operation of the mold clamping device having the above configuration will be described. First, the control device supplies currents in the same direction to the coils 21 and 24 to generate an attractive force, so that the first and second electromagnets 18 and 22 do not separate, and
With the toggle mechanism 31 in the extended state, the mold thickness adjusting nut 25 is rotated, and the first and second electromagnet frames 13,
20, the movable platen 12 and the movable mold 16 are advanced to bring the fixed mold 15 and the movable mold 16 into contact with each other. In this way, the mold thickness can be adjusted.

Next, the mold opening / closing control section drives the servomotor 27 with a speed reducer, places the toggle mechanism 31 in a contracted state, and retracts the movable platen 12 and the movable mold 16 to predetermined positions at high speed. At this time, the control device supplies current in the same direction to the coils 21 and 24 to generate an attractive force, and the first and second electromagnets 18 and 22 move the movable platen 12
To prevent separation due to inertial force caused by acceleration and deceleration.

Subsequently, the mold opening / closing control section drives the servomotor 27 with a speed reducer, places the toggle mechanism 31 in the extended state, and advances the movable platen 12 and the movable mold 16. As a result, as shown in FIG. 2, the fixed mold 15 and the movable mold 16 are brought into contact, and the mold is closed. At this time, the control device supplies currents in the same direction to the coils 21 and 24 to generate an attractive force, and the first and second electromagnets 18 and 22 are separated by inertial force due to acceleration and deceleration of the movable platen 12. Not to be.

The force required to advance the movable platen 12 and the movable mold 16 is sufficiently smaller than the mold clamping force. Therefore, a large load is not applied to the servomotor 27 with the speed reducer. Next, the mold clamping force control unit, in accordance with each current command generated by the first and second current command generator 66, 67, the coil 21,
Currents are supplied to the first and second electromagnets 18 and 22 in the same polarity to generate a repulsive force. At this time, the repulsive force is transmitted to the movable platen 12 via the toggle mechanism 31 as a mold clamping force.
2 and a movable mold 16 is fixed to the fixed mold 1.
5 and clamp the mold. This state is maintained until the mold is opened.

In this case, by changing the value of the current supplied to the coils 21 and 24, the mold clamping force can be changed during molding. Note that the repulsive force is f
Assuming that the current supplied to the coils 21 and 24 is I, when the first and second electromagnets 18 and 22 are used in a linear region, the repulsive force f and the current I have the following relationship.

F∝I ² and the repulsive force f is generated when the toggle mechanism 31 is placed in the extended state. It is not affected by expansion or the like. Therefore, the mold clamping force can be accurately controlled by feedback controlling the mold clamping force.

Subsequently, when a melted resin is filled in a cavity space (not shown), cooled and solidified, the mold clamping force is set to zero in the mold clamping force setting unit 61 within a time set by an operator. A large mold clamping force command is generated. As a result, the current supplied to the coils 21 and 24 is cut off, and the repulsive force f and the mold clamping force disappear.
Next, in this state, when the servomotor 27 with a speed reducer is driven in the reverse direction to contract the toggle mechanism 31, the movable platen 12 and the movable mold 16 are retracted. And FIG.
As shown in (2), the fixed mold 15 and the movable mold 16 are separated, and the mold is opened. At this time, the control device supplies a current in the same direction to the coils 21 and 24 to generate an attractive force, and the first and second electromagnets 18 and 22 do not separate due to inertial force due to acceleration and deceleration of the movable platen 12. To do.

It should be noted that the present invention is not limited to the above-described embodiment, but can be variously modified based on the gist of the present invention, and they are not excluded from the scope of the present invention.

[0028]

As described above in detail, according to the present invention, in a mold clamping device, a fixed platen, a fixed mold attached to the fixed platen, and a predetermined distance from the fixed platen. A first electromagnet frame provided with a first electromagnet, a movable platen disposed to be able to advance and retreat along a tie bar provided between the fixed platen and the first electromagnet frame, A movable mold attached to the movable platen; and a second electromagnet disposed to face the first electromagnet, the second electromagnet being movably disposed with respect to the first electromagnet frame. An electromagnet frame, a link mechanism connecting the second electromagnet frame and the movable platen, an electric motor connected to the link mechanism and capable of driving in the forward and reverse directions, and the link mechanism. And it has a load detector for detecting a load applied to the movable platen, a mold clamping force set, and based on the detected load by the load detector, and a controller for feedback controlling a mold clamping force.

In this case, when the motor is driven, the link mechanism is placed in the extended state, the movable platen is advanced,
The fixed mold and the movable mold are brought into contact, and the mold is closed. Next, when currents in opposite directions are supplied to the coil of the first electromagnet and the coil of the second electromagnet, a repulsive force is generated. At this time, the repulsive force is transmitted as a mold clamping force to the movable platen via the link mechanism, and the movable mold is pressed against the fixed mold to perform mold clamping.

Therefore, the mold clamping force can be changed during molding by changing the value of the current supplied to the coil according to the set mold clamping force. Further, since the repulsive force is generated when the link mechanism is placed in the extended state, the toggle magnification characteristic of the link mechanism is not affected by backlash, friction, thermal expansion and the like of the link mechanism. Therefore, the mold clamping force can be accurately controlled by feedback controlling the mold clamping force.

The other mold clamping device of the present invention further has a position detecting means for detecting the position of the movable platen. Then, the control device performs feedback control of the position of the movable platen based on the set position and the position detected by the position detection unit. In this case, since the position of the movable platen is feedback-controlled, the mold can be closed and opened with high accuracy.

[Brief description of the drawings]

FIG. 1 is a first state diagram of a mold clamping device according to an embodiment of the present invention.

FIG. 2 is a second state diagram of the mold clamping device according to the embodiment of the present invention.

FIG. 3 is a block diagram of a mold opening / closing control unit of the control device according to the embodiment of the present invention.

FIG. 4 is a block diagram of a mold clamping force control unit of the control device according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Fixed platen 12 Movable platen 13 First electromagnet frame 14 Tie bar 15 Fixed mold 16 Movable mold 18 First electromagnet 20 Second electromagnet frame 22 Second electromagnet 27 Servo motor with reduction gear 31 Toggle mechanism 51 Load detection Instrument 52 Position detector

Claims (2)

[Claims] 1. A fixed platen, (b) a fixed mold attached to the fixed platen, and (c) a first electromagnet disposed at a predetermined distance from the fixed platen. A first electromagnet frame, and (d) a movable platen disposed to be able to advance and retreat along a tie bar provided between the fixed platen and the first electromagnet frame;
A movable mold attached to the movable platen; and (f) a second electromagnet disposed so as to face the first electromagnet, and movably disposed with respect to the first electromagnet frame. A second electromagnet frame, (g) a link mechanism for connecting the second electromagnet frame and the movable platen, and (h) a link mechanism for driving in the forward and reverse directions. (I) a load detector for detecting a load applied to the movable platen via the link mechanism; and (j) a set clamping force and a load detected by the load detector. And a control device for performing feedback control of the mold clamping force. 2. The apparatus according to claim 1, further comprising: a position detecting unit configured to detect a position of the movable platen, wherein the control unit feeds back a position of the movable platen based on the set position and the position detected by the position detecting unit. The mold clamping device according to claim 1, which controls.