JPS645809B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a method of controlling an electric injection device.

(b) Conventional technology There are two types of injection devices of conventional injection molding machines: fully hydraulic type and hydraulic/electric type. A fully hydraulic injection device uses a hydraulic motor to rotate the screw for plasticizing the resin material, and a hydraulic cylinder to move the screw for injecting the molten resin. be.
In addition, a hydraulic/electric injection device uses an electric motor to rotate the screw for plasticizing, and moves the screw for injection using hydraulic pressure.

(c) Problems to be solved by the invention The injection device of the conventional injection molding machine as described above is
In any case, hydraulic cylinders are used, and the gaskets and sealing members used to seal the high-pressure oil are prone to wear and tear, requiring periodic replacement, and operation may be interrupted due to oil leaks. There are cases where the system has to be stopped, and there are many factors that reduce productivity.
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to make it possible to generate a predetermined screw back pressure when an injection device is motorized.

(d) Means and operation for solving the problems The present invention achieves the above object by electrifying both the plasticizing and injection operations and controlling the screw back pressure by the rotation of the electric motor. That is, during injection, the first motor capable of driving the screw in the axial direction is rotated, and the second motor capable of rotationally driving the screw is stopped, and during plasticization, the second motor is rotated, and the first motor is connected to the resin pressure sensor. The resin 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. By doing this, 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). An intermediate shaft 18 is supported by the casing 14 via a ball screw mechanism 16.
That is, the nut member 20 is fixed to the casing 14, and the nut member 20 is fixed to the outer diameter portion of the intermediate shaft 18.
A male thread that meshes with the ball screw mechanism 16 is formed. An end of the intermediate shaft 18 on the outside of the casing 14 is connected to the first electric motor 22 via an extendable joint (not shown). An end of the intermediate shaft 18 on the inside of the casing 14 is connected to a drive shaft 26 via a thrust bearing 24 . 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 has a spline 28
It is connected to the screw 12 so as to rotate together with it. 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, which drive gear 32 is connected to a shaft 34 by a sliding key 36. The sliding key 36 has a length longer than the stroke of the screw 12. An end of the shaft 34 on the outside of the casing 14 is connected to a second 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, a setting device 48, and a drive circuit 50. Current from the drive circuit 50 is output to the first electric motor 22. In addition, the control device 4
2 has components other than these, and the second
Although the operation of the electric motor 38 is also controlled, illustration thereof is omitted.

Next, the operation of this embodiment will be explained. 1st
The figure shows the injection completed state. When the injection is completed, the first electric motor 38 rotates the shaft 3, which is a rotational drive mechanism.
4, sliding key 36, driving gear 32 and driven gear 3
The rotational drive of the drive shaft 26 is started via 0. 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 10 (on the left side in FIG. 1). As the amount of 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 motor 22 rotates in a predetermined direction, the intermediate shaft 18 moves rightward in FIG. 1 due to the action of the ball screw mechanism 16. For this reason, the drive shaft 26 also moves to the right together with the intermediate shaft 18. For example, if this moving speed is made the same as the speed at which the screw 12 is moved by the molten resin transferred to the front of the cylinder 10, , the screw 12 moves without receiving pressure from the molten resin. In other words, the screw back pressure is not applied. If the speed of movement of the intermediate shaft 18 in the right direction is slower than above, the amount of increase in 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 move away from the molten resin. Move to the right while under pressure. In other words, the 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, when the first electric motor 22 is stopped, the screw 12 does not move at all, so the screw back pressure becomes maximum, and as described above, the intermediate shaft 18 is moved at the same speed as the backward speed of the screw 12 due to the molten resin. When the first electric motor 22 is rotated as shown in FIG. 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 46 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 50. The drive circuit 50 outputs a signal to rotate the first electric motor 22 so that the deviation becomes zero. That is, when the actual resin pressure is greater than the set value, the rotational speed of the first electric motor 22 is increased, and in the opposite case, the rotational speed of the first electric motor 22 is decreased. Therefore, the resin pressure is always controlled according to the set value. As the drive shaft 26 moves, the drive gear 32 moves along the sliding key 36 to follow the drive shaft 26 while being engaged with the driven gear 30 due to the action of the collar 32a. When the intermediate shaft 18, drive shaft 26, and screw 12 move by a predetermined amount in this way, the first electric motor 22 and the second electric motor 3
The rotation of 8 is stopped and the plasticizing stroke is completed. Thus, once the plasticizing stroke is completed, the injection stroke is then performed. 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,
Due to the action of the ball screw mechanism 16, the intermediate shaft 18 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, the molten resin that has been plasticized and melted within the cylinder 10 is injected. In addition, in this case as well, the drive gear 3
2 moves along with the driven gear 30 following the drive shaft 26. In this way, the state shown in Figure 1 is reached again,
Injection stroke is completed. One cycle is completed with the above steps, and the same operation is repeated thereafter. Eventually, the driving force of the first electric motor 22 moves the screw 12 for injection and applies back pressure to the screw.
Further, the second electric motor 38 rotates the screw 12 for plasticizing. In other words, both the injection operation and the plasticizing operation are motorized,
Does not require hydraulic drive. Further, 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) Effects of the invention As explained above, according to the present invention, both the rotation of the screw for plasticizing and the stroke of the screw for injection are motorized, and the back pressure of the screw during plasticization is also reduced to the actual level. Since the resin pressure is fed back and controlled by the rotation of the electric motor, the productivity of the injection molding machine is improved by eliminating the need for hydraulic equipment. control is possible. 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... cylinder, 12... screw, 14...
...Casing, 16...Ball screw mechanism, 18...
... Intermediate shaft, 20 ... Nut member, 22 ... First electric motor, 26 ... Drive shaft, 30 ... Driven gear, 32
... Drive gear, 38 ... Second electric motor, 40 ... Resin pressure sensor, 42 ... Control device.

Claims (1)

[Scope of Claims] 1. 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 section at the tip of the cylinder. A method for controlling an electric injection device having a resin pressure sensor configured to rotate a first electric motor and a second electric motor at the time of injection.
The electric motor is stopped, and during plasticization, the second electric motor is rotated, and the first electric motor is controlled at a rotational speed so that the resin pressure detected by the resin pressure sensor matches a preset value, which is different from that during injection. A method of controlling an electric injection device characterized by rotating it in the opposite direction.