JP2003320567A - Method for controlling mold clamping device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a power loss and also overheating by feeding an excessive electric current to a servomotor 15 owing to being controlled and driven such that the servomotor 15 compulsorily turned by a mold clamping force and a powerful die opening force is returned to an original locating position, when the servomotor 15 is positioned in a mold registering position. <P>SOLUTION: After a mold mounted on a stationary platen 4 and a movable platen 5 is registered by an opening/closing means 2 and positioned by the servomotor 15, when the movable platen 5 positioned by the servomotor 15 is displaced by an external force in the step of transferring to the mold clamping or in the step of releasing the mold clamping force then transferring to the powerful mold opening, a positioning target position of the movable platen 5 is moved in response to a displacement where the movable platen 5 is displaced by the external force. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method for smoothly moving and displacing a movable plate in an energy-saving manner when opening and closing a mold clamping device such as an injection molding machine and clamping the movable plate.

[0002]

2. Description of the Related Art According to a conventional control method for a mold clamping device shown in FIG. 1, after a mold is matched by an opening / closing means 2, a half nut 19 is engaged with an engaging portion 20 and a pressing means 3 is used. When the mold is clamped, the movable platen 5 is moved to the fixed platen 4 side by several mm from the mold matching position due to the mold clamping force, so that the servo motor 15 is forcibly rotated. At this time, when a spring 8 that acts to push open the fixed mold 6 and the movable mold 7 is provided, after the molds are matched by the opening / closing means 2, the mold is clamped by the pressing means 3. Alternatively, in the step of releasing the mold clamping force by the pressing means 3 and strongly opening the mold, the phenomenon that the movable mold 7 is separated from the fixed mold 6 by the spring 8 occurs. In order to prevent this abnormal phenomenon, the servo motor 15 is position-controlled at the mold matching position to prevent the spring 8 from separating the movable mold 7 from the fixed mold 6. Since the conventional control method controls the positioning of the servo motor 15 at the mold matching position in this way, the servo motor 15 returns to the original positioning position when rotated by the mold clamping force or the strong mold opening force. Servo motor 15
An excessive current flows through the servo motor 15 and power loss occurs, and the servomotor 15 overheats.

[0003]

SUMMARY OF THE INVENTION The present invention has been proposed to solve the problems of power loss and overheating of a servomotor in a mold clamping device as described above.

[0004]

[Means for Solving the Problems] That is, an opening / closing means for opening and closing a movable platen by a servomotor, and a means different from the servomotor for clamping the movable platen with respect to a fixed platen and / or performing a strong mold opening. In a method of controlling a mold clamping device including a clamping means for performing, a mold clamping process is performed after the molds attached to the fixed plate and the movable plate are matched by the opening / closing device, or a mold clamping force is applied. When the movable plate positioned by the servo motor is displaced by an external force in the step of releasing and moving to the strong mold opening, the movable plate is displaced by the external force to the positioning target position of the movable plate. The movable platen is moved according to the amount of displacement, and more specifically, the positioning target position of the movable platen is moved to a position where the movable platen is displaced by an external force.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a plan view of a partial cross section showing an outline of a mold clamping device for carrying out the present invention and a block diagram of a control device, and FIGS. 2 and 3 are flow charts showing a control method of the present invention.

The mold clamping device 1 includes an opening / closing means 2, a pressing means 3,
And a control device 22. The opening / closing means 2 is a fixed platen 4.
Servomotors 15 mounted on both side surfaces of the encoder, an encoder 16 connected to the drive shaft of the servomotors 15, and a ball screw 1
7 and a ball nut 18 screwed onto the ball screw 17 and attached to both side surfaces of the movable plate 5. In the vicinity of the four corners of the fixed platen 4 and the movable platen 5, through holes for slidably inserting four tie bars 9 are provided, and the movable platen 5 to which the movable mold 7 is attached is a fixed platen to which the fixed mold 6 is attached. 4, a servo motor 15 is arranged so that it can be moved toward and away from each other. The end of the ball screw 17 opposite to the fixed platen is supported by the support plate 10 so as to be rotatable and reciprocally movable.

The pressing means 3 is engaged with and disengaged from the engaging part 20 formed on the outer peripheral surface of the tie bar 9 and a driving device such as a cylinder provided on the side opposite to the fixed platen of the movable platen 5. And a mold clamping cylinder 11 that is provided on the side opposite to the movable platen of the fixed platen 4 and that pushes and pulls the tie bar 9. The internal space of the mold clamping cylinder 11 is divided into a mold clamping chamber 13 and a strong mold opening chamber 14 by a piston 12 fixed to the end surface of the tie bar 9, and an engaging portion 20 of the tie bar 9 is moved by a half nut 19 to a movable plate. 5, the pressure oil is supplied to the mold clamping chamber 13 to clamp and mold the mold, and the pressure oil is supplied to the strong mold opening chamber 14 to release the molded product from the mold. Therefore, strong mold opening is performed. The pressing means 3 is an example, and there are various other types. For example, the mold clamping cylinder may be provided on the movable platen 5 instead of the fixed platen 4, or the mold clamping cylinder and the half nut may be provided on the support platen 10 so that the movable platen and the support platen move integrally. Further, the engaging portion may be provided not on the tie bar but on a member protruding on the side opposite to the fixed plate of the movable plate.

The control device 22 includes an input unit 24, an output unit 25, a setting / display unit 26 and a storage unit 27, a speed control unit 28 and a current / power control unit 29, which are connected to a CPU 23 composed of a microprocessor by a bus line. The servo amplifier 31 is composed of The control device 22 controls the sequence control of the mold clamping device 1 and the injection device (not shown) and the control of the servomotor. The control device 22 is input to the input unit 24 based on the set values of the position, speed, force, etc. of the movable plate 5 set by the setting / display unit 26, and the operation program and constants stored in the storage unit 27. A speed signal is output from the output unit 25 to the hydraulic device 30 and the servo amplifier 31 that drive the mold clamping cylinder 11 so that the position of the tie bar 9 from the position sensor 21 and the position of the movable platen 5 from the encoder 16 are set positions. And control. In addition to the speed signal, the output unit 25 outputs a torque command for limiting the output torque of the servo motor 15 to the speed control unit 28.

The above control device 22 and servo amplifier 3
Although reference numeral 1 is composed of a known one, a portion related to positioning control of the servo motor 15 will be described. The positioning target position of the movable platen 5 set on the setting / display unit 26 is
The position signal of the movable platen 5 input to the input unit 24 from the encoder 16 fixed to the shaft of the servomotor 15 and the storage unit 2
It is collated by the calculation of the CPU 23 based on the control program stored in 7, and the calculated speed signal is input to the speed control unit 28 of the servo amplifier 31. The speed control unit 28 matches the speed signal with the speed value detected by the encoder 16, and outputs a control signal PID-calculated so that the speed value matches the speed signal to the current / power control unit 29. The current / power control unit 29 generates a current accurately corresponding to the control signal by a constant current circuit, further power-amplifies the current and supplies it to the servomotor 15. According to the servo system, which is a positioning control system including the control device 22, the servo amplifier 31, and the servo motor 15, as described above,
Positioning of the movable platen 5 is controlled by the servomotor 5 so that the movable platen 5 always reaches the target position set by the setting / display unit 26.

Next, the mold clamping operation in the mold clamping device 1 is shown in FIG.
It will be described based on. In this control, the CPU 23 controls the output unit 25 and the servo so that the position of the movable platen 5 becomes the target position set by the setting / display unit 26 based on the control program and constants stored in the storage unit 27 in the control device 22. The arithmetic processing is performed through the amplifier 31 and the servo motor 15 is controlled and executed. In the mold open state in which the movable mold 7 is separated from the fixed mold 6 as shown in FIG. 1, the half nut 19 is prevented from engaging with the tie bar 9, and the servo motor 15 is driven to move the movable plate 5 to the movable plate 5. It is brought close to the fixed platen 4. The movable mold 7 is matched with the fixed mold 6 (S1) and abutted to complete the mold closing. At this time, the encoder 16 that detects the distance from the mold closing completion position of the movable mold 7 detects the zero position. Then, the servo motor 15 is position-controlled with the zero position as the target position, and enters the servo lock state (S
2). In this state, even if the movable mold 7 has the spring 8, the elastic force of the spring 8 causes the movable mold 7 to move.
Does not separate from the fixed mold 6. Next, each half nut 19 is driven close to the tie bar 9, and the half nuts 1
9 and the tie bar 9 are engaged. Then, the mold clamping cylinder 11
The pressure oil is supplied to the mold clamping chamber 13 and the movable platen 5 is pulled toward the fixed platen 4 to clamp the mold. At this time, the movable platen 5 is further moved in the direction of the fixed platen 4 from the zero position by the mold clamping force, so that the servo motor 15 servo-locked moves the movable platen 5 from the zero target position (several mm). Is forcibly rotated to the negative side by an amount corresponding to (S3). Therefore, the servo motor 15 whose position is controlled to return to the original zero position
A relatively large current flows through the servo motor 15, and if this state continues, the servo motor 15 will generate heat and power will be lost. Therefore, the torque command to the servo motor 15 is changed to a lower predetermined value (S4), and the zero target position of the positioning control of the servo motor 15 is displaced by the external force which is the mold clamping force of the clamping means 3. The position is moved to the moved position by sequentially changing it every predetermined time (2 msec in this example) (S
5). This step S5 is repeated until the mold clamping is completed (S6). When the mold clamping is completed, the torque command changed to a low value is returned to the original value (S7). Note that steps S4 and S7 are executed as needed and are not essential.

The operation of the strong mold opening which is another embodiment of the present invention will be described with reference to FIG. After the mold is clamped by the pressing means 3 as described above, the molten resin injected and filled into the cavity of the mold from the injection device (not shown) is cooled and solidified to form a molded product. Then, the movable mold 7 is separated from the fixed mold 6 in order to separate and take out the molded product. At this time,
When the molded product has a large shape in the moving axis direction of the movable mold 7, the servo motor 15 is insufficient in the force required for releasing the molded product against the adhesive force between the molded product and the mold cavity surface. There is. Therefore, the hydraulic pressure of the clamping means 3 strongly opens the mold.

Prior to opening the strong mold, first, step S1
In No. 1, the hydraulic pressure supplied to the mold clamping chamber 13 of the mold clamping cylinder 11, which is the pressure clamping means, is released to release the mold clamping pressure. At this time, the half nut 19 maintains the engaged state with the tie bar 9, and further prevents the movable mold 7 from moving due to the elastic force of the spring 8 when the spring 8 is built in the movable mold 7. The servo motor 15 is servo-locked so that the movable platen 5 performs positioning control at the zero position, which is the mold closing completion position (S12). At this time, the encoder 16 that detects the distance from the mold closing completion position of the movable mold 7 detects the zero position. Next, when pressure oil is supplied to the strong mold opening chamber 14 of the mold clamping cylinder 11 to perform strong mold opening, the servo motor 15 which is servo-locked moves the movable plate 5 to the positive side by several mm. Accordingly, the target position of zero is forcibly rotated (S13). Therefore, the servo-locked servo motor 15 is position-controlled so as to return to the original zero position, so that a relatively large current flows through the servo motor 15, and if this state continues, the servo motor 15 generates heat and power is consumed. It will be a loss. Therefore, the torque command to the servomotor 15 is changed to a lower predetermined value (S14), and
The target position of the positioning control of the servo motor 15 which has been zero is sequentially changed every predetermined time (2 msec in this example) to the position displaced by the external force which is the strong mold opening force of the clamping means 3. To move (S15). This step S15 is repeated until the strong mold opening force is completed (S16). When the powerful mold opening is completed, the torque command changed to a low value is returned to the original value (S17). After that, the half nut 19 is disengaged from the tie bar 9 and the movable platen 5 is opened by the servo motor 15. Note that step S14 and step S17 are executed as necessary,
It is not mandatory.

Although the embodiments of the present invention have been illustrated and described above, this is merely an example, and the present invention should not be construed as being limited to the specific description of the embodiments.

For example, it is described that the torque command of the servo motor 15 is changed to a lower predetermined value after the movable platen 5 is moved by an external force and the servo motor 15 in the servo lock state is forcibly rotated. However, the movable platen 5 is moved by an external force and the servo motor 1 in the servo lock state
When 5 is forcibly rotated, the servo lock may be released, that is, the servo system of the servo motor 15 may be invalidated and the power supply to the servo motor 15 may be cut off.

Further, when the servo motor 15 in the servo lock is forcibly displaced by an external force, the target position of the servo motor 15 is moved to the displaced position, but it is displaced. You may make it move to the target position which is within the amount of displacement and a speed signal becomes within the range of a predetermined value.

Further, as means for detecting that the servo motor 15 which is servo-locked is forcibly displaced by an external force, the following may be mentioned. When the speed signal increases beyond the specified value. When the position value of the encoder 16 changes. Encoder 16
When the value of velocity or acceleration calculated based on the position value of exceeds the specified value.

[0017]

Since the present invention is carried out as described above, even in the case of a mold having a built-in spring, the mold is changed at the time of switching the process from completion of mold closure or clamping or pressure release to strong mold opening. The movable plate can be operated smoothly without opening and without power loss.

[Brief description of drawings]

FIG. 1 is a plan view of a partial cross section schematically showing a mold clamping device embodying the present invention and a block diagram of a control device.

FIG. 2 is a flow chart showing a control method of a mold clamping process in the present invention.

FIG. 3 is a flow chart showing a method of controlling the strong mold opening step in the present invention.

[Explanation of symbols]

1 ……… Mold clamping device 2 ……… Opening and closing means 3 ……… Clamping means 4 ……… Fixed board 5 ……… Movable plate 6 ……… Fixed mold 7 ……… Movable mold 8 ……… Spring 9 ……… Taiba 10 …… Support board 11 …… Mold clamping cylinder 12 ... Piston 13 …… Mold clamping chamber 14 …… Strong type room opening 15 ... Servo motor 16 ... Encoder 17 ... Ball screw 18 …… Ball nut 19 …… Half nut 20 ... Engagement part 21 …… Position sensor 22 ... Control device 23 ... CPU 24 …… Input section 25 …… Output section 26 …… Setting / display section 27 …… Memory unit 28 …… Speed control unit 29 ...... Current / power control unit 30 ... Hydraulic system 31 ... Servo amplifier

Claims (4)

[Claims] 1. An opening / closing means for opening and closing a movable platen by a servomotor, and a clamping means for clamping the movable platen to a stationary platen and / or for strongly opening the movable platen by means different from the servomotor. In the control method of the mold clamping device, the molds attached to the fixed plate and the movable plate are aligned by the opening / closing means and positioned by the servo motor,
Positioning of the movable platen when the movable platen positioned by the servo motor is displaced by an external force in the process of shifting to mold clamping or in the process of releasing the mold clamping force and shifting to strong mold opening A method of controlling a mold clamping device, wherein a target position is moved according to a displacement amount of the movable plate displaced by an external force. 2. When the movable plate positioned by the servo motor is displaced by an external force, a positioning target position of the movable plate is moved to a position where the movable plate is displaced by an external force. The method for controlling a mold clamping device according to claim 1, wherein: 3. When moving the positioning target position of the movable platen to a position where the movable platen is displaced by an external force, the torque command of the servo motor is changed to a lower value to move the positioning target position. The method for controlling the mold clamping device according to claim 1 or 2, wherein the original torque command value is returned to the original torque command value. 4. An opening / closing means for opening and closing the movable platen by a servomotor, and a clamping means for clamping the movable platen to the stationary platen and / or for strongly opening the movable platen by means different from the servomotor. In the control method of the mold clamping device, the molds attached to the fixed plate and the movable plate are aligned by the opening / closing means and positioned by the servo motor,
When the movable plate positioned by the servo motor is displaced by an external force in the step of shifting to mold clamping or in the step of releasing the mold clamping force and shifting to strong mold opening, the servo system of the servo motor A method for controlling a mold clamping device, characterized in that the current is cut off by disabling the current.