JPS62105618A - Controller of motor-driven injection molding machine - Google Patents

Abstract

PURPOSE:To enable the titled controller to mold every cycle under the seme terms by keeping an operation state of an electric motor under that at the time of completion of plasticization during a period from the time of completion of the plasticization to commencement of an injection action of the next cycle. CONSTITUTION:When a shaft 84 is turned by a second electric motor 71 from a state where an injection action has been completed, an intermediate shaft 22 is turned through a drive gear 83 and driven gear 82, a screw 12 which is connected with the intermediate shaft 22 through a spline turns within a cylinder 10, through which resin pellets to be supplied within a cylinder 10 from a material supply port 10a is fused, plasticized and transferred in front of the cylinder 10. When the intermediate shaft 22 and screw 12 are moved by a predetermined stroke, a plasticization action is suspended. A detected value from a second pulse generator 73 at this time is stored in a memory 112, and a position of an axial direction and that of a turning direction of the screw 12 are kept as they are under a state at the time of completion of plasticizing action by actions of a first controller 108 and second controller 116 until the injection action of the next cycle is started.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a control device for an electric injection molding machine.

(B) Prior Art The injection device of a conventional injection molding machine includes a fully hydraulic type and a hydraulic/electric type. A fully hydraulic injection device uses a hydraulic motor to rotate a screw for plasticizing the resin material, and a hydraulic cylinder to move the screw for injecting the molten resin.

Further, in the 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 However, in the conventional injection device as described in (2), the screw retracts slightly due to the pressure of the molten resin in the cylinder between the end of plasticization and the start of injection. Because the machine rotates and rotates, the molding conditions for each cycle are unstable.
This poses a problem in that it becomes an obstacle when performing precise molding. In other words, the screw is rotated to knead and melt the resin material, and when a predetermined amount of plasticization is completed, the screw waits at that position until the injection process, but during this time, the pressure of the molten resin exerts a force on the screw to push it backwards. is working. The pushing force acting on this screw is supported by closing the switching valve of the hydraulic circuit that supplies hydraulic pressure to the injection cylinder, but leakage of hydraulic oil from the switching valve, seal, etc. is completely prevented. Since the screw cannot be stopped, the screw retracts as described above. The amount of retraction of the screw varies with each cycle depending on the degree of kneading of the resin material. For this reason,
The injection operation start position changes every cycle, which hinders precision molding. The present invention aims to solve these problems.

(d) Means for Solving Problems The present invention electrifies plasticization and injection, and changes the operating state of the electric motor from the end of plasticization to the start of the injection operation of the next cycle. By maintaining the condition, the above problem is solved. That is, the control device for an electric injection molding machine according to the present invention includes a first electric motor capable of driving a screw in the cylinder of the injection molding machine in a ring direction, a second electric motor capable of rotationally driving the screw, and a rotational position of the first electric motor. a first rotational position detection device that detects the rotational position of the second electric motor; a plasticization end position setting device that can set the screw position at the end of the plasticization stroke; A memory device that stores the detection value of the second rotational position detection device at the end of the stroke, and a plasticization end position setter that stores the detection value of the first rotational position detection device from the end of plasticization to the start of injection operation. a first controller that controls operation of the first electric motor to match the value;
From the end of plasticization to the start of injection operation, the detection value of the second rotational position detection device is above +! and a second controller for controlling the operation of the second electric motor so that the second electric motor matches the stored value of the second electric motor.

(e) Operation When the first electric motor is brought into a free rotation state (or brought into a state where a small driving force is generated) and the second electric motor is rotated, the screw is rotationally driven, and the resin material is plasticized within the cylinder.
The screw moves back due to resin pressure. When the screw retreats to the position set by the plasticization end position setter, a second
The signal from the rotational position sensing device is stored in a memory.

Further, at this point, the rotation of the first electric motor and the second electric motor is stopped. If the screw is retracted by the resin pressure in the cylinder in this state, the deviation between the actual screw position detected by the first rotational position detection device and the screw position set by the plasticization end position setting device occurs, so the first controller outputs a signal to drive the first electric motor so as to eliminate this deviation. Thereby, the position of the screw is always maintained at the state set by the plasticization end position setting device. Furthermore, if the screw is rotated by the resin pressure, the amount of rotation is detected by the second rotational position detection device, and the second controller detects the actual rotational position of the second electric motor and the value stored in the memory. A signal is output to operate the second electric motor so as to eliminate the deviation. Thereby, the rotational direction position of the screw is always maintained at the rotational direction position at the end of plasticization. By doing this, the axial and rotational positions of the screw are maintained as they were at the end of plasticization from the end of plasticization to the start of the injection process of the next cycle, and molding is performed under the same conditions for each cycle. Therefore, more precise molding can be performed.

(F) Embodiments Hereinafter, embodiments of the present invention will be described based on FIGS. 1 and 2 of the accompanying drawings.

As shown in FIG. 2, 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 casing 14 is constituted by a housing 16 and a cover 18, and thereby the chamber 2
0 is partitioned. A rotatable and axially movable intermediate shaft 22 is provided in this chamber 20 . intermediate shaft 22
has a small diameter shaft portion 24 and a large diameter shaft portion 26.

The tip of the small diameter shaft portion 24 is connected to the screw 12 by a spline. The small diameter shaft portion 24 is connected to the housing 16
Slide bearing mounted on 36. It is rotatably and axially movably supported by a receiver 38. intermediate shaft 2
A nut member 54 having a female thread that constitutes a ball screw mechanism 52 together with a male thread 50 provided at 411h48 is fixed to the large diameter shaft portion 26 side of No. 2. A first shaft 11811+48 provided with a male thread 50 is rotatably supported by a thrust pair link 56 and a bearing 58 with respect to the cover 18. The shaft 48 is connected to a first electric motor 70 outside the casing 4. The first electric motor 70 is provided with a first pulse generator 72 (first rotational position detection device). It is well supported. Outer circumference 1.1 of large diameter shaft portion 26 of intermediate 1 draw 22
A driven gear 82 is attached to rotate together with the intermediate shaft 22 by means of ``~-181.The driven gear 82 meshes with a drive southeast 83 with a collar 83a, 6MB4, which is connected to the shaft 84 by a sliding key 85, connects the housing 16 and the cover 1.
8f is rotatably supported by bearings 86 and 87. The part of @84 that protrudes from the outside of the casing 14 is connected to the second electric motor 71. Second
The electric motor 71 is provided with a second pulse generator 73 (second rotational position detection device).

FIG. 1 shows a device that controls the first electric motor 71 and the second electric motor 71. The device that controls the first electric motor 70 sets the plasticization end position of the screw 12. 102, an AD converter 104 that AD converts the signal from the plasticization end position setting device 102, a comparator 106 that compares the signals from the first pulse generator 72 and the AD converter 104, and the comparator 106. A first controller 108 that performs control to eliminate deviation, and a first controller 1
It has a drive circuit 110 that amplifies the signal from 08 and outputs it to the first electric motor 70. Further, the device for controlling the second electric motor 71 includes a memory 11 that stores a signal from the second pulse generator 73 when the screw 12 reaches the plasticization end position set by the plasticization end position setting device 102.
2. a comparator 114 that compares the signal from the memory 112 and the signal from the second pulse generator 73; a second controller 116 that performs control to eliminate the deviation calculated by the comparator 114; It has a drive circuit 118 that amplifies the signal from the controller 116 and outputs it to the second electric motor 71.

Next, the operation of this embodiment will be explained.

FIG. 2 shows the state in which the injection operation is completed and the plasticizing operation begins. From this state, the second electric motor 7! When @84 rotates, the intermediate shaft 22 also rotates via the drive gear 83 and driven tooth $82. When the intermediate shaft 22 rotates, the screw 12 connected to the first shaft through a spline rotates within the cylinder 10, and the resin pellets supplied into the cylinder 10 from the material supply port 10a provided with a hopper are rotated. Melt and plasticize, 11f of cylinder lO
(to the left in Figure 2). At this time, if the first electric motor 70e applies a constant torque in the direction of the injection operation to the slurry 48, an appropriate back pressure will be applied, and the degree of kneading can be adjusted in the same direction. In this way, when the intermediate @ 22 and the screw 12 move by a preset stroke, that is, when the detected value of the first pulse generator 72 matches the set value of the plasticization end position setter 102, the previous y
The conversion operation is stopped. The detected value from the second pulse generator 73 at the time when this plasticizing operation is stopped is stored in the memory 112. Thereafter, until the injection operation of the next cycle is started, the axial position and rotational position of the screw 12 are maintained at the state at the end of the mold-making operation by the actions of the first controller 108 and the second controller 116 as described below. will be maintained as is.

Even after the plasticization is completed, the pressure of the molten resin acts on the screw 12 to force it to retreat further. For example, if the screw 12 is retracted without rotation, the intermediate shaft 22 and the nut member 54 are also retracted without rotation, causing the shaft 48 to rotate. Therefore, the first electric motor 70 is rotated, thereby changing the detected value of the first pulse generator 72. 1st
The detected value of the pulse generator 72 is input to the comparator 106, where it is compared with the set value set by the plasticization end position setting device 102, and when the first electric motor 70 rotates as described above, A comparator 106 calculates the deviation. The first controller 108 issues a command to rotate the first electric motor 70 to the drive circuit 110 so as to eliminate this deviation. As a result, the screw 12 returns to the position at the end of plasticization.

Further, when the screw 12 is retreated and rotated due to the resin pressure, the position in the rotational direction is also returned to the state at the end of plasticization by the action of the second controller 116. That is, the rotation of the second electric motor 71 is detected by the second pulse generator 73, and this detected value and the memory B11
The comparator 1 compares the value stored in the comparator 2 (i.e., the detected value of the second pulse generator 73 at the end of plasticization) with the stored value stored in the comparator 1.
14, and when a deviation occurs, the second controller 116 outputs a rotation command to the drive circuit 118 to eliminate this deviation, and changes the rotational position of the second electric motor 71, that is, the screw 1.
The rotational position of No. 2 is returned to the state at the end of plasticization. In addition, in this case, the first electric motor 7 by the first *J controller 108
The above-mentioned control of 0 is also performed at the same time. As mentioned above, the first
By controlling the electric motor 70 and the second electric motor 71, the axial position and rotational position of the screw 12 are maintained as they were at the end of plasticization until the injection operation of the next cycle is started.

Therefore, the position of the screw 12 at the start of the injection operation does not change with each repeated cycle.

Therefore, molding conditions are stabilized and precise molding becomes possible.

In this embodiment, a pulse generator is used as the rotational position detecting device of the electric motor, but a tacho generator may also be used.

(g) As described in detail, according to the present invention, the first . Since the rotational position of the electric motor and the second electric motor is maintained at the rotational position at the end of plasticization, the screw is held in the fixed position for each cycle, stabilizing the molding conditions and enabling more precise molding. .

[Brief explanation of drawings]

FIG. 1 is a diagram showing a control device for an electric injection molding machine according to the present invention, and FIG. 2 is a diagram showing the electric injection molding machine. 12... Screw, 70... First electric motor, 71...
...Second electric motor, 72...First pulse generator (first rotational position detection device), 73...Second pulse generator (second
(rotational position detection device), 102...plasticization end position setter, 108...first controller, 112...memory device, 1
16...Second controller.

Claims (1)

[Scope of Claims] A control device for an electric injection molding machine including a first electric motor capable of driving a screw in an injection molding machine cylinder in an axial direction, and a second electric motor capable of rotationally driving the screw. a first rotational position detection device that detects the rotational position of the second electric motor; a second rotational position detection device that detects the rotational position of the second electric motor; and a plasticization end position setting device that can set the screw position at the end of the plasticization stroke. , a storage device that stores the detection value of the second rotational position detection device at the end of the plasticizing stroke, and a storage device that stores the detection value of the second rotational position detection device at the end of the plasticization stroke, and a storage device that stores the detection value of the first rotational position detection device from the end of plasticization to the start of the injection operation. a first controller that controls the operation of the first electric motor so as to match the set value of the end position setter; and a detected value detected by the second rotational position detector from the end of plasticization to the start of injection operation. a second controller that controls the operation of the second electric motor so that the value coincides with the stored value stored in the memory device.