JPS6137409A - Method of controlling motor driven injection apparatus - Google Patents

Abstract

PURPOSE:To improve the production efficiency of an injection molding machine, by allowing both the rotation of a screw for plasticizing and the stroke of the screw to be driven by motors, feeding back the actual resin pressure to control the screw back pressure at the plasticizing by the rotation of the motor. CONSTITUTION:When an intermediate shaft 18, a driving shaft 26 and a screw 12 are moved in prescribed amounts, the rotation of a first motor 22 and a second motor 38 is stopped to complete the plasticizing stroke. After the completion of the plasticizing stroke, the injection stroke is carried out. That is, with the second motor 38 kept stopped, when the first motor 22 is rotated reversely, the intermediate shaft 18 is moved to the left in Fig. 1 by the action of a ball screw mechanism 16. As a result, a screw 12 is also moved via a thrust bearing 24 and the driving shaft 26. Thus, a melted resin that has been plasticized and melted in a cylinder 10 is injected. The screw back pressure at the plasticizing can be controlled in a prescribed manner by controlling the rotational speed of the first motor 22 to move the intermediate shaft 18 in a prescribed speed.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention has 1! The present invention relates to a method of controlling a dynamic injection device.

(b) Prior Art The injection device of a conventional injection molding machine includes a fully hydraulic type and a hydraulic/electric combination type. In a fully hydraulic injection device, a hydraulic motor rotates a screw for plasticizing the resin material, and a hydraulic cylinder moves the screw for injecting molten resin.

Further, in a hydraulic/electric injection device, a screw for plasticizing is rotated by an electric motor, and a screw for injection is moved by hydraulic pressure.

(c) Problems to be solved by the invention In any case, the injection device of the conventional injection molding machine as described above uses a hydraulic cylinder, and the injection device uses a hydraulic cylinder to seal high-pressure oil, a seal member, etc. Since they are prone to wear and tear, they require periodic replacement work, and there are also cases where operations have to be stopped due to oil leaks, and there are many factors that reduce productivity. Ta.

The present invention solves the above problems and makes it possible to generate a predetermined screw back pressure when an injection device is motorized. The purpose is to

(d) Means and action for solving the problems The present invention includes:
The above objective is achieved by electrifying both the plasticizing and injection operations and controlling the screw back pressure by rotation of the electric motor. That is, during injection, the first motor that can drive the screw in the axial direction is rotated, and the second motor that is capable of rotating the screw is stopped, and during kadaization, the second motor is rotated, and the first motor is connected to the resin pressure sensor. It is rotated in the opposite direction to that during injection at a rotational speed controlled so that the resin pressure detected by is consistent with a preset setting value. By doing so, the screw is retracted while the resin pressure in the nozzle portion is maintained at the set value.

(E) Embodiments Hereinafter, embodiments of the present invention will be described based on FIG. 1 of the accompanying drawings.

A screw 12 is inserted into a cylinder 10 of an injection molding machine. A casing 14 is attached to the rear end side of the cylinder 10 (upstream side in the resin flow direction). The intermediate shaft 18 is connected to the casing 14 via the ball screw mechanism 16.
is supported.

That is, a nut member 20 is fixed to the casing 14, and a male thread that engages with the nut member 20 to form the ball screw mechanism 16 is formed on the outer diameter portion of the intermediate shaft 18. The end of the intermediate shaft 18 on the outside of the casing 14 is connected to the first electric motor 22 via an expandable joint (not shown), and the end of the intermediate shaft 18 on the inside of the casing 14 is connected to the thrust bearing 24. The drive shaft 26 is connected to the drive shaft 26 via the drive shaft 26 . That is, although the intermediate shaft 18 and the drive shaft 26 rotate separately, they can transmit axial force to each other. The other end of the drive shaft 26 is connected to the screw 12 by a spline 28 so as to rotate together with the screw 12 . A driven gear 30 is attached to the drive shaft 26 so as to rotate together with the driven gear 30. The driven gear 30 meshes with a drive gear 32 with a collar 32a, and this drive gear 32 is connected to a shaft 34.
is connected by a sliding key 36. The sliding key 36 has a length longer than the stroke of the screw 12. The outer end of the casing 1-4 of the shaft 34 is connected to the second
It is connected to an electric motor 38. A resin pressure sensor 40 is provided at the nozzle portion at the tip of the cylinder 10. A signal from the resin pressure sensor 40 is input to a control device 42 . The control device 42 includes an amplifier 44, a comparator 46 . Setting device 48
and a drive circuit 50. Current from drive circuit 50 is output to 'fS1 motor 22. In addition, the control Il
The device 42 has components other than these, and a second
- Although the operation of the electric R38 is also controlled, illustration of these components is omitted.

Next, the operation of this embodiment will be explained. FIG. 1 shows the injection completed state. When the injection is completed, the first electric motor [38 starts rotating the drive shaft 26 through the shaft 34, the sliding key 36, the drive gear 32, and the driven gear 30, which are rotation drive mechanisms. Since the drive shaft 26 is connected to the screw 12 by a spline 28, the screw 12 rotates within the cylinder 10, melts and plasticizes the resin material supplied from the material supply port 10a to the inner diameter of the cylinder 10, and is transferred to the nozzle section in front of (on the left side in FIG. 1). As the molten resin transferred to the front of the cylinder 10 increases, the resin pressure at the nozzle portion of the cylinder 10 tends to rise, but this resin pressure is controlled to a predetermined state by the rotation of the first electric motor 22. That is, when the first electric @ 22 rotates in a predetermined direction, the ball screw mechanism 16
Due to this action, the intermediate shaft 18 moves to the right in FIG. Therefore, the drive shaft 26 also moves to the right together with the intermediate shaft 18, but for example, the speed of this movement is controlled by the cylinder 10.
If the speed is the same as that at which the screw 12 moves due to the molten resin being transferred forward, the screw 12 will move without receiving pressure from the molten resin. In other words, the screw back pressure is not applied. Intermediate shaft 1
If the moving speed of g in the right direction is slower than above, the amount of increase in the molten resin will be greater than the amount of increase in volume at the tip of the cylinder 10 due to the movement of the screw 12, so the screw 12 will reduce the pressure from the molten resin. Move to the right while receiving it. In other words, a state occurs in which screw back pressure is generated. The magnitude of this screw back pressure is determined by the moving speed of the intermediate shaft 18 in the right direction in the figure, that is, the rotational speed of the first electric motor 22. That is, the first electric 4! ! When the screw 22 is stopped, the screw 12 does not move at all, so the screw back pressure becomes maximum, and as mentioned above, the Ml electric motor 22 moves the intermediate shaft 18 at the same speed as the retraction speed of the screw 12 due to the molten resin. When the screw is rotated, the screw back pressure becomes 0, and at an intermediate speed, the first electric motor 2
2 produces a screw back pressure between 0 and the maximum value depending on the rotation speed. Actually, the rotational speed of the first electric motor 22 is controlled by the control device 42 as follows. That is, the resin pressure at the nozzle portion of the cylinder 10 is detected by the resin pressure sensor 40, and a signal indicating the actual resin pressure is inputted to the comparator 4 through the amplifier 44. The comparator 46 compares the set value preset by the setter 48 with the actual resin pressure, and sends the deviation to the drive circuit 5o. The drive circuit 50 is
A signal is output to rotate the first electric motor 22 so that the difference becomes zero. That is, when the actual resin pressure is greater than the set value, the rotation speed of the first electric motor 22 is increased,
In the opposite case, the rotational speed of the first electric motor 22 is reduced.

Therefore, the resin pressure is always controlled according to the set value. Note that as the drive shaft 26 moves, the drive gear 32
2a, the sliding key 36 moves along the sliding key 36, following the drive shaft 26, while being engaged with the driven gear 30. When the intermediate shaft 18, drive shaft 26, and screw 12 move by a predetermined amount in this manner, the rotation of the first electric motor 22 and the second electric motor 38 is stopped, and the plasticizing stroke is completed. In this way, once the cartonization stroke is completed, the injection stroke is performed next. That is, while the second electric motor 38 remains stopped, the first electric motor 22 is rotated in the opposite direction to that in the case of the plasticizing stroke described above. When the first electric motor 22 rotates, the intermediate shaft 1 is rotated by the action of the ball screw mechanism 16.
8 moves to the left in FIG. Therefore, the screw 12 also moves to the left in FIG. 1 via the thrust bearing 24 and the drive shaft 26. As a result, cylinder 10
The molten resin that has been made concave inside is injected. Note that in this case as well, the drive gear 32 moves together with the driven gear 30 following the drive shaft 26. In this way, the state shown in FIG. 1 is reached again, and one cycle is completed when the injection stroke is completed, and the same operation is repeated thereafter. Eventually, the driving force of the first electric motor 22 moves the screw 12 for injection, and the screw Back pressure is applied and the second electric motor 38 rotates the screw 12 for plasticizing. That is, both the injection operation and the plasticizing operation are motorized and do not require hydraulic drive;
The screw back pressure during plasticization can be controlled in a predetermined manner as described above by controlling the rotational speed of the first electric motor 22 and moving the intermediate shaft 18 at a predetermined speed.

(f) As described in detail, according to the present invention, - Both the rotation of the screw for curvature and the stroke of the screw for injection are motorized, and the back pressure of the screw during plasticization is also reduced. Since the actual resin pressure is fed back and controlled by the rotation of the electric motor, there is no need for hydraulic equipment, improving the productivity of the injection molding machine. It becomes possible to apply control power.

Therefore, the screw back pressure can be controlled as specified, and the molten resin can be uniformly kneaded.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an electric injection device for carrying out the method of the present invention. 10... e cylinder, 12 - screw, 14... casing, 16... ball screw mechanism, 18... - intermediate shaft, 20... seat/to member, 22 - Φ - first electric motor , 26... Drive shaft, 30... Driven gear, 32...
Fist drive gear, 38...second electric motor, 4o...resin pressure sensor, 42...control device.

Claims (1)

[Claims] A first electric motor capable of driving a screw in the cylinder of an injection molding machine in the axial direction via a ball screw mechanism, a second electric motor capable of rotationally driving the screw, and a nozzle provided at the tip of the cylinder. In a method of controlling an electric injection device having a resin pressure sensor, the first electric motor is rotated and the second electric motor is stopped during injection, and the second electric motor is rotated and the first electric motor is controlled by the resin pressure sensor during plasticization. A control method for an electric injection device, characterized in that the electric injection device is rotated in a direction opposite to that during injection at a rotational speed controlled so that the detected resin pressure matches a preset setting value.