JP2002067135A - Blow molding method and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent hunting by employing an electromotor as a drive source of a mold in place of a hydraulic mechanism and generating set mold clamping force by one electromotor without making the electromotor large-sized. SOLUTION: At first, a servo motor 10 is rotationally driven, while positionally controlled by a position controller 18, to perform the closing operation of molds 12 and 13. After the completion of mold closing operation, the control circuit 14 of the molds 12 and 13 is changed over from positional control to torque control by a control mode changeover device 21, and pressure not less than the air pressure supplied to the parison in the molds 12 and 13 is applied to the molds 12 and 13 to perform mold clamping operation. In this mold clamping operation, the torque of the servo motor 10 is controlled in order to generate the maximum mold clamping force within the overload time of the servo motor 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a blow molding method.

[0002]

2. Description of the Related Art There is a very efficient blow molding method for molding a thermoplastic resin such as vinyl chloride or polyethylene into a hollow molded article such as a bottle or a container. As an example, a heated and melted thermoplastic resin is extruded or injected into a tube shape by a blow molding machine to form a parison, and when the parison has a size suitable for a hollow molded product, a pair of left and right dies are hydraulically driven. Tighten with cylinder. Next, pressurized air is blown into the parison, and the parison is brought into close contact with the inside of the mold and cooled and solidified to form a hollow molded article such as a bottle or a container.

[0003]

In such a blow molding method, since a hydraulic cylinder is used as an electric power source of a mold, oil leakage has always been a problem. For this reason,
It has been difficult to use a blow molding machine in a clean room for equipment, machines and products that dislike oil deposition. In addition, when hydraulic pressure is used, it is difficult to manage changes in hydraulic pressure characteristics due to temperature changes, and precise positioning with reproducibility has not been performed. It is conceivable to use an electric source instead of the power source of the mold by such hydraulic pressure. However, when an electric motor such as a servomotor is used as the electric source of the pair of dies, there are the following problems. That is, when moving each mold, a position command is given to the servomotor of each mold, and each servomotor is driven by position control. However, in the position control, the generated torque is indefinite. Therefore, when the mold is closed after the mold is closed, a hunting phenomenon occurs in which the mold swings right and left due to imbalance of the generated torques of both servomotors, and this adversely affects the characteristics of the product at the time of curing. There is a concern that quality and surface properties will deteriorate.

When air is fed to the parison after the mold is clamped, a reaction force is applied to the mold, but when the servo motor is driven by position control, a large torque is not generated and the mold is opened by the reaction. There is a risk. An apparatus in which the hunting phenomenon is improved is described in Japanese Patent Application Laid-Open No. 2-108517. In this publication, the molds are moved by position control until the molds are closed by the servomotors of the molds. During the tightening process, one of the servomotors is set to the position control, and the other is set to the torque control. Despite the tightening force, it requires two servomotors, which increases the cost of the equipment. A combination of a servomotor and a ring arm in place of the above-mentioned motor system is disclosed in
Japanese Patent Application Laid-Open No. Hei 7-3089 discloses a combination of a servomotor and a toggle mechanism.
No. 59, No. 7-3314544, No. 8-10394
And JP-A-10-151667, however, these publications require a ring arm or a toggle mechanism, which complicates the structure of the apparatus and may cause a response delay. In each of the above publications, as the tightening force increases, the capacity of the servomotor increases, and the tie bar of the mold also increases in diameter. The present invention has been made in view of such a conventional problem, and employs an electric motor instead of a hydraulic mechanism as a driving source of a mold.
By using an overload circuit that has not been actively used in the past, a set clamping force is generated by one electric motor without increasing the size of the electric motor, thereby solving the problems such as the hunting. With the goal.

[0005]

In order to achieve the above object, a specific invention uses a single electric motor as a drive device for opening and closing a pair of dies, and the electric motor uses the electric motor via a transmission member to form the dies. After the mold is closed at high speed, when the mold is closed, the electric motor is overloaded, a high torque is generated, and the mold is clamped with the set clamping force. . Preferably, the time for generating the mold clamping force is 2-3 seconds, and the cooling time is about 30 seconds.
Seconds. In order to achieve the object, after the mold clamping in the blow molding method, the reverse rotation of the electric motor is prevented, the overload is released, and the molded article is cooled in this state. Is released, and then the electric motor is reversed to open the mold. In order to achieve the object, the electric motor in this blow molding method is a servomotor, and the servomotor is first rotated and driven by position control by a position controller to perform a mold closing operation. The control mode switch switches from position control to torque control, and performs a mold clamping operation by applying a pressure equal to or greater than the air pressure supplied to the parison in the mold to the mold. It is characterized in that the servomotor is torque controlled so as to generate the maximum mold clamping force within the load time. In order to achieve the above object, a related invention provides a single electric motor as a driving device for opening and closing a pair of molds, and the electric motor is used to feed the molds at high speed via a transmission member to close the molds. After that, when closing the mold, overload the electric motor,
A blow molding apparatus is provided with a control circuit for generating a high torque and clamping a mold with a set clamping force. In order to achieve the above object, after the mold clamping in the blow molding apparatus, the reverse rotation of the electric motor is prevented, the overload is released, and the molded article is cooled in this state. Wherein the control circuit has a function of releasing the reverse rotation preventing state, and then reversing the electric motor to open the mold. In order to achieve the object, the electric motor in the blow molding apparatus is a servomotor, and the control circuit first rotates the servomotor by position control by a position controller to perform a closing operation of a mold. After the closing operation is completed, the control mode switcher switches the position control to the torque control, and performs a mold clamping operation by applying a pressure equal to or higher than the air pressure supplied to the parison in the mold to the mold.In this mold clamping operation, It is characterized in that the servomotor is torque controlled so as to generate the maximum clamping force within the overload time of the servomotor.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Representative embodiments of the apparatus according to the fourth, fifth and sixth aspects will be described below. In FIG. 1, A
Indicates a blow molding machine. In this blow molding machine A, a driving force of a servomotor 10 which is a kind of a single electric motor is transmitted by a transmission member 11 such as a lead screw to a pair of dies 12,
The opening / closing operation and the mold clamping operation of the pair of dies 12 and 13 are performed. The drive of the single servomotor 10 is controlled by a control circuit 14. In addition, a servomotor to which a lock device for preventing reverse rotation of the output shaft is added is used.

The control circuit 14 of the servo motor 10 includes:
It comprises a controller 15 and a servo driver 16.
In the control circuit 14, a deviation between a mold moving distance set value provided by a setting unit provided in the controller 15 and a position feedback signal from the pulse encoder 17 for measuring the moving distance of the mold is obtained. The controller 18 performs position control as a major loop. This position deviation is given to the servo driver 16 as a speed command, and is compared with a speed feedback signal obtained by differentiating the amount of pulse from the pulse encoder 17 with time by a differentiator 19. It is provided to the servomotor 10 through a mode switch 21 and a torque controller 22. The controller 15 further includes a torque setting value setting unit. After the closing operation of the molds 12 and 13 is completed, the servo motor 10 is switched from the position control to the torque control by the control mode switch 21 in the mold clamping process. There is a configuration.

[0008] The operation of the device having the above structure is described in claim 1,
A description will be given as a representative embodiment of the method invention described in the second and third aspects. First, the servo motor 10 is connected to the position controller 18.
, And the molds 12 and 13 are closed. After the closing operation of the molds, the control circuit 14 of the molds 12 and 13 is switched from the position control to the torque control by the control mode switch 21 to increase the pressure higher than the air pressure supplied to the parisons in the molds 12 and 13. The mold clamping operation is performed on the molds 12 and 13. In this mold clamping operation, the torque of the servo motor 10 is controlled so as to generate the maximum mold clamping force within the overload time of the servo motor 10. In other words, the servo motor is normally operated so as not to be overloaded, but the servo motor is usually allowed to have an overload state for about 5 to 8 seconds. That is the point of the present invention. After this maximum clamping force is generated, the reverse rotation of the servomotor 10 is prevented, and the overload is released. That is, after the servo motor 10 is set in the lock mode and the motor 10 is locked in a state where the tightening force is maintained, the overload state is released, and the mold clamping is performed during the parison blowing and cooling and removal of the molded product. Maintain power. For example, the servo motor 10 is locked by, for example, fixing an output shaft of the servo motor 10 with an electromagnetic clutch normally attached to the servo motor 10 so that the output shaft is not reversed. By doing so, the pair of molds is fixed in a state of being strongly tightened. At this time, the input for rotating the torque motor 10 is turned off. When the pair of dies 12 and 13 are opened after cooling the molded product, the reverse rotation prevention state of the servo motor 10 is released, the electric motor is reversed, and the dies 12 and 13 are open.

Specifically, first, the mold clamping force is released, the control circuit 14 of the servomotor 10 is switched to position control, the dies 12, 13 are opened at high speed, returned to the original position, and the next parison is supplied. Prepare for.

FIG. 3 is a diagram showing the opening and closing movement of the mold in one cycle of the blow molding machine A. The mold 12,
Servo motor 10 is used as a drive source for opening / closing 13 and closing the mold.
Is used, but the servo motor used as a lifting drive source of a plunger (not shown) used for extruding a parison in a blow die head may also be used. Also, in order to control the thickness of the parison, a servomotor is used as a drive source for raising and lowering the nozzle of the blow die head, or a servomotor is used for driving the blow nozzle into a mold. In this case, these may be used in common.

[0011]

According to the first, second and third aspects of the present invention, the opening and closing operation and the closing operation of the pair of left and right dies are performed by a single electric motor, so that the dies are formed during molding. It is possible to perform stable mold clamping control and blow molding without opening the mold in response to the air supplied to the parison inside and without hunting during mold clamping. By overloading the electric motor during mold clamping, the set mold clamping force can be exhibited without increasing the capacity of the electric motor. As a result, an existing tie bar can be used without increasing the size of the tie bar of the mold, and conversion from a hydraulic cylinder system to an electric system can be easily performed.

Further, by overloading the electric motor to generate a high torque, the pair of dies can be clamped by the set clamping force. In addition, since the drive source is an electric motor, the influence of temperature such as oil pressure is small, and there is no problem of oil leakage. In the invention according to claim 2, in the step of expanding the parison and cooling and removing the molded article following the mold clamping, the reverse rotation of the electric motor is prevented, the overload is released, and the cooling of the molded article is performed in this state. By doing so, overheating and backlash of the motor can be prevented.

[0013] The device invention according to claim 4 can implement the method invention according to claim 1 and exhibit its effects. The device invention according to claim 5 can implement the method invention according to claim 2 and exhibit its effects. The device invention according to claim 6 can implement the method invention according to claim 3 and exhibit its effects.

[Brief description of the drawings]

FIG. 1 is a mechanism diagram of an embodiment.

FIG. 2 is a block diagram of a control circuit.

FIG. 3 is a diagram showing opening and closing movements of a mold in one cycle of the apparatus.

[Explanation of symbols]

 10 Servo motor 12 Mold 13 Mold

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[Procedure amendment]

[Submission date] November 8, 2001 (2001.11.
8)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 6

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0005

[Correction method] Change

[Correction contents]

[0005]

In order to achieve the above object, a specific invention uses a single electric motor as a drive device for opening and closing a pair of dies, and the electric motor uses the electric motor via a transmission member to form the dies. After the mold is closed at high speed, when the mold is closed, the electric motor is overloaded, a high torque is generated, and the mold is clamped with the set clamping force. . Preferably, the time for generating the mold clamping force is 2-3 seconds, and the cooling time is about 30 seconds.
Seconds. In order to achieve the object, after the mold clamping in the blow molding method, the reverse rotation of the electric motor is prevented, the overload is released, and the molded article is cooled in this state. Is released, and then the electric motor is reversed to open the mold. In order to achieve the object, the electric motor in this blow molding method is a servomotor, and the servomotor is first rotated and driven by position control by a position controller to perform a mold closing operation. The control mode switch switches from position control to torque control, and performs a mold clamping operation by applying a pressure equal to or greater than the air pressure supplied to the parison in the mold to the mold. It is characterized in that the servomotor is torque controlled so as to generate the maximum mold clamping force within the load time. To put it simply, the servo motor is usually operated so as not to be overloaded.
It is permissible for about 8 seconds to about 8 seconds, and it is the point of the present invention that the tightening force is generated by making maximum use of this allowable range. In order to achieve the above object, a related invention provides a single electric motor as a driving device for opening and closing a pair of molds, and the electric motor is used to feed the molds at high speed via a transmission member to close the molds. After that, at the time of mold clamping, a blow molding device is provided, in which a control circuit for overloading the electric motor to generate high torque and clamping the mold with the set clamping force is provided. . In order to achieve the above object, after the mold clamping in this blow molding device,
The reverse rotation of the electric motor is prevented, the overload is released, the molded article is cooled in this state, and after the cooling, the reverse rotation prevention state of the electric motor is released, and then the electric motor is reversed. The control circuit has a function of opening a mold. In order to achieve the object, the electric motor in the blow molding apparatus is a servomotor, and the control circuit first rotates the servomotor by position control by a position controller to perform a closing operation of a mold. After the closing operation is completed, the control mode switcher switches the position control to the torque control, and performs a mold clamping operation by applying a pressure equal to or higher than the air pressure supplied to the parison in the mold to the mold.In this mold clamping operation, It is characterized in that the servomotor is torque controlled so as to generate the maximum clamping force within the overload time of the servomotor.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction contents]

The control circuit 14 of the servo motor 10 includes:
Specifically, the controller 15 and the servo driver 16
(See FIG. 2). In this control circuit 14,
The deviation between the mold moving distance set value provided by the setting unit provided in the controller 15 and the position feedback signal from the pulse encoder 17 for measuring the moving distance of the mold is obtained. Is performed. This position deviation is given to the servo driver 16 as a speed command, and is compared with a speed feedback signal obtained by differentiating the amount of pulse from the pulse encoder 17 with time by a differentiator 19. It is given to the servomotor 10 through the mode switch 21 and the torque controller 22 (see FIG. 2). The controller 15 is further provided with a torque setting value setting unit. After the closing operations of the molds 12 and 13 are completed,
In the mold clamping process, the control mode switch 21 switches the servo motor 10 from position control to torque control.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction contents]

[0008] The operation of the device having the above structure is described in claim 1,
A description will be given as a representative embodiment of the method invention described in the second and third aspects. First, the servo motor 10 is connected to the position controller 18.
, And the closing operation of the pair of dies 12 and 13 is performed. After the mold closing operation is completed, the dies 12, 13
The control circuit 14 is switched from the position control to the torque control by the control mode switch 21, and performs a mold clamping operation by applying a pressure higher than the air pressure supplied to the parison in the dies 12, 13 to the dies 12, 13. In this mold clamping operation, the torque of the servo motor 10 is controlled so as to generate the maximum mold clamping force within the overload time of the servo motor 10. After this maximum clamping force is generated, the reverse rotation of the servomotor 10 is prevented, and the overload is released. That is, after the servo motor 10 is set in the lock mode and the motor 10 is locked in a state where the tightening force is maintained, the overload state is released, and the mold clamping is performed during the parison blowing and cooling and removal of the molded product. Maintain power. As an example, the lock of the servo motor 10 is fixed by an electromagnetic clutch normally attached to the servo motor 10 so that the output shaft of the servo motor 10 is not reversed. By doing so, the pair of dies 12 and 13 are fixed in a state of being strongly tightened. At this time, this servo motor 10
Is turned off. After cooling this molded product,
When the pair of dies 12 and 13 are opened, the reverse rotation preventing state of the servomotor 10 is released, the servomotor 10 is reversed, and the pair of dies 12 and 13 are
open.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction contents]

Further, by overloading the electric motor to generate a high torque, the pair of dies can be clamped by the set clamping force. Further, since the driving source is an electric motor, the influence of temperature such as oil pressure is small, and there is no problem of oil leakage, so that it is possible to cope with a clean room.
In the invention according to claim 2, in the step of expanding the parison and cooling and removing the molded article following the mold clamping, the reverse rotation of the electric motor is prevented, the overload is released, and the cooling of the molded article is performed in this state. By doing so, overheating and backlash of the electric motor can be prevented.

Claims (6)

[Claims] An electric motor is used as a drive device for opening and closing a pair of dies, and the electric motor is used to feed the dies at high speed via a transmission member to close the dies. Characterized in that a high torque is generated by overloading the mold, and the mold is clamped with a set clamping force. 2. After the mold clamping, the reverse rotation of the electric motor is prevented, the overload is released, the molded article is cooled in this state, and after cooling, the reverse rotation prevention state of the electric motor is released. 2. The blow molding method according to claim 1, wherein the electric motor is turned over to open the mold. 3. The electric motor is a servomotor, and the servomotor is first driven to rotate by position control by a position controller to perform a mold closing operation. After the mold closing operation is completed, the position is controlled by a control mode switch. The control is switched from control to torque control, and the mold clamping operation is performed by applying a pressure equal to or higher than the air pressure supplied to the parison in the mold to the mold. In this mold clamping operation, the maximum mold clamping is performed within the overload time of the servo motor. 3. The blow molding method according to claim 1, wherein a torque of the servomotor is controlled to generate a force. 4. A single electric motor is provided as a drive device for opening and closing the pair of dies. The electric motor is used to feed the dies at high speed via a transmission member to close the dies. And a control circuit for overloading the electric motor to generate a high torque and clamping the mold with a set clamping force. 5. After the mold is clamped, the electric motor is prevented from rotating in the reverse direction, the overload is released, and the molded product is cooled in this state. After cooling, the electric motor is released from the reverse rotation preventing state. 5. The blow molding apparatus according to claim 4, wherein the control circuit has a function of opening the mold by reversing the electric motor. 6. The electric motor is a servo motor, and the control circuit drives the servo motor to rotate first by position control by a position controller 18 to perform a mold closing operation. The control mode switch switches from position control to torque control, and performs a mold clamping operation by applying a pressure equal to or higher than the air pressure supplied to the parison in the mold to the mold. In this mold clamping operation, the servo motor is overloaded. 5. A structure in which a servomotor is torque-controlled so as to generate a maximum mold clamping force within a time.
Or the blow molding apparatus according to 5.