JPH11165337A - Driving system for molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid an increase in a rating of a motor driven servo motor by reducing a starting current of the motor for driving a molding machine. SOLUTION: In the driving system for a molding machine for inputting a driving force generated from a motor driven servo motor 11 via a reduction gear to a drive input unit of an injecting unit 1 of the machine, a reduction gear ratio variable type reduction gear 10 is used as a reduction gear, and controlled so that a reduction gear ratio is increased at the time of a large load of the injecting unit and decreased at the time of a small load.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a drive system of a molding machine such as an injection molding machine or an extrusion molding machine, and more particularly to a drive system of a molding machine driven by an electric servomotor.

[0002]

2. Description of the Related Art For example, an injection molding machine includes an injection unit,
Operation units such as a mold clamping unit and an ejector unit are provided. These operating units are activated at some stage in the injection molding process and perform a defined task. Conventionally, an electric servomotor is used as a drive source of such an operation unit, and a driving force generated by the electric servomotor is input to a driving force input section of the operation unit via a speed reducer. (Japanese Patent Laid-Open No. 8-39)
No. 633).

In a conventional injection molding machine using an electric servomotor of this type as a driving source, a reduction ratio of a reduction mechanism for performing one operation (for example, a mold closing operation or an injection operation) is fixed, and the mold clamping is performed. When the load is very large, such as when the mold is closed in the unit or when the injection is performed in the injection unit, the drive current of the electric servomotor is increased to around 300% of the rated value to drive.

[0004]

However, when the starting current is increased to 300% of the rated current and the motor is driven, the efficiency of the motor is poor and the heat generation is large. On the other hand, if a servo motor with a large rated output is used to solve this problem, the size will be larger than that of the mold clamping unit and the injection unit, and the whole molding machine will be large, and the power consumption will increase. Due to the large inertia of the motor, there is a problem that the rise time at the time of startup becomes long and the resin starts to cool down, and there is a problem that ancillary equipment such as a transformer becomes large.

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention can reduce the starting current of an electric servomotor without increasing the size and rated output of the electric servomotor, and as a result, achieve a small injection It is an object of the present invention to provide a drive system of an injection molding machine or an extrusion molding machine that can shorten the rise time of an operation and a mold closing operation.

[0006]

According to a first aspect of the present invention, there is provided a driving system of a molding machine for inputting a driving force generated by an electric servomotor via a speed reducer to a driving force input section of an operation unit of the molding machine. The above-mentioned problem has been solved by providing a variable reduction ratio type speed reducer as the speed reducer.

In this drive system, the load torque of the electric servomotor can be reduced by increasing the reduction ratio of the speed reducer. Therefore, when the load is large, such as at the time of starting the operation unit, the drive current of the electric servomotor can be reduced by setting the reduction ratio to a large value. Can be.

According to a second aspect of the present invention, in the first aspect, the speed reduction ratio of the variable speed reduction type speed reducer is increased when at least one of starting of the operation unit, pressure holding, and locking of mold clamping is performed. The above problem is solved by providing control means for reducing the speed reduction ratio of the variable speed reduction type speed reducer while the operation unit is moving.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a partial configuration of an injection unit 1 of an injection molding machine according to an embodiment. The injection unit 1 has a heating cylinder 3 in which a screw 2 is housed so as to be able to advance and retreat and rotate freely, and a housing 4 for holding the heating cylinder 3. A screw moving member 5 is arranged inside the housing 4 so as to be non-rotatable and movable in the front-rear direction. A screw rotating gear 6 connected to the rear end of the screw 2 is rotatably supported by the screw moving member 5. . The screw rotation gear 6 is driven by the electric servomotor 11 or another drive source via another reduction mechanism (not shown).

At the rear end of the screw moving member 5, a screw shaft 7 as a driving force input portion is screwed. The screw shaft 7 is connected to an electric servomotor 11 via a speed reducer 10 with a variable reduction ratio. The speed reducer 10 includes a drive pulley 1 connected to an output shaft of an electric servomotor 11.
2, a driven pulley 13 connected to the screw shaft 7, and a belt 14 wound between the pulleys 12 and 13.

The drive pulley 12 has a small diameter portion 12a,
The driven pulley 13 has a large-diameter portion 13a and a tapered portion 12c connecting the large-diameter portion 12b and the tapered portion 12c.
It has a small diameter portion 13b and a tapered portion 13c connecting them. In this belt pulley type reduction gear 10,
Small diameter portion 12a of drive pulley 12 and driven pulley 1
3, the large diameter portion 13a of the drive pulley 12 and the small diameter portion 13b of the driven pulley 13 correspond. The belt 14 is wound between the corresponding large diameter portion and small diameter portion, and the switching position is switched by the switching device 15 so that the reduction ratio can be switched between two stages.

When the belt 14 is wound between the small diameter portion 12a of the drive pulley 12 and the large diameter portion 13a of the driven pulley 13, the reduction ratio becomes large. Drive pulley 1
2 large diameter portion 12b and driven pulley 13 small diameter portion 13b
If the belt 14 is wound between them, the reduction ratio becomes small.

The switching device 15 is controlled by control means (not shown), and switches the reduction ratio to a large side at the time of starting the injection operation and at the time of holding pressure, and switches the reduction ratio to a small side at the time of intermediate filling (during movement). It has become.

FIG. 2 shows the change characteristics of the reduction ratio during the injection operation controlled by the control means.

As described above, the reduction ratio of the speed reducer 10 is set to a large value at the time of starting (injection start) and holding pressure with a large load, and the reduction ratio is set to a small value (normal value) at the time of filling. The load torque of the electric servomotor 11 during the pressure holding can be reduced, and the driving current at that time can be reduced.
Therefore, the drive current can be supplied in a well-balanced manner throughout the injection process, so that efficiency can be improved, heat generation can be prevented, and electricity costs can be saved. As a result, the rise time of the injection operation can be reduced.

Further, since the starting load on the electric servomotor 11 is reduced, it is not necessary to increase the rating of the electric servomotor 11, so that the entire molding machine can be reduced in size, and the control of the transformer and the like can be realized. Ancillary equipment can be downsized. In addition, when developing a large-sized injection molding machine, it was necessary to develop a large-sized electric servomotor together with the conventional one. Can be used to make large injection molding machines. Further, in a structure in which the starting torque is increased by using two small servomotors, two servomotors are required, and the structure of the transmission unit becomes complicated, resulting in an increase in cost. If this is the case, the complexity of the structure and extra cost increase can be eliminated.

It should be noted that the variable reduction ratio type speed reducer is not limited to the belt pulley type as in the above embodiment, but various types can be employed. For example, a torque converter type reduction gear, an electromagnetic transmission type reduction gear, a gear switching type reduction gear and the like can be adopted. Further, a multi-stage transmission that can change the gear ratio to not only two stages but multiple stages or a continuously variable transmission that can change continuously can be employed. In this case, the gear ratio can be more smoothly switched. In any case, a large reduction ratio at the time of startup and a reduction ratio after the startup can be used. The electric servomotor may be of any type such as an analog type, a digital type, an induction type and a permanent magnet type.

Further, in the above-described embodiment, the case where the present invention is applied to the injection unit of the injection molding machine has been described, but the present invention can of course be applied to other operation units. In that case,
The reduction gear between the driving force input unit of the operation unit and the electric servomotor may be replaced with a variable reduction gear reducer so that a large reduction ratio is obtained when the load is large. For example,
When the present invention is applied to a double toggle type mold clamping unit disclosed in Japanese Patent Application Laid-Open No. 9-164570 and the like, the speed reducer between the driving force input portion of the crosshead and the electric servomotor is a variable reduction ratio type speed reducer. The large reduction ratio may be set at the time of startup and at the time of mold locking. When the present invention is applied to an ejector unit, the same technique may be applied to a speed reducer of a driving force input unit connected to an ejector rod.

The present invention is not limited to an injection molding machine, but can be similarly applied to various operation units of an extrusion molding machine.

[0021]

As described above, according to the present invention,
The speed reducer between the driving force input section of the operating unit of the molding machine and the electric servomotor is a variable speed-reduction type speed reducer that can be switched to a large reduction ratio when the operation unit is started, so the size of the electric servomotor is large. Without starting, the starting current can be reduced, and the problems of efficiency deterioration and heat generation can be solved. In addition, since it is possible to start efficiently with a large reduction ratio at the time of starting, it is also possible to realize a shortened rise time of the injection operation and the mold closing operation as a result.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an injection unit of an injection molding machine according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a change in a reduction ratio during an injection operation of the injection unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Injection unit 7 ... Screw shaft (driving force input part) 10 ... Variable reduction ratio type reduction gear 11 ... Electric servo motor

Claims (2)

[Claims] 1. A drive system of a molding machine for inputting a driving force generated by an electric servomotor to a driving force input portion of an operation unit of the molding machine via a speed reducer, wherein the speed reducer has a variable reduction ratio type reduction gear. A drive system for a molding machine, comprising a molding machine. 2. The speed reduction ratio of the variable speed reduction type speed reducer according to claim 1, wherein the speed reduction ratio of the variable speed reduction type speed reducer is increased when at least one of the operation unit is activated, the pressure is maintained, and the mold is locked. A drive system for a molding machine, further comprising control means for reducing a reduction ratio of the variable speed reduction type speed reducer.