JPH01122422A - Plasticizing device of injection molding machine - Google Patents

Abstract

PURPOSE:To enable the title device to control precisely the number of revolutions and back pressure of a screw at the time of plasticization, by a method wherein driving of either right or left direction is made possible by performing calculation and control of a manipulated variable by a control device with a microcomputor by making use of detected values of hydraulic pressure and the number of revolutions and a rate of the screw. CONSTITUTION:Detected signals of a pressure detector 9, a speed detector 11 in an axial direction of a screw 6, a position detector 10 and a number of revolution detector 12 of a hydraulic motor are applied to a control device 15 constituting of a microcomputor, manipulated variables i1, i2, i3 of servovalves 14, 14', 14'' are calculated and a hydraulic motor 21, injection cylinder 7 and miniature cylinder 13 are controlled. Prior to plasticization, the manipulated variable i2 of the servolvalve 14' is set up at the negative maximum value so that hydraulic oil within injection cylinder can be returned to a tank 17 side freely and the miniature cylinder 13 is used for control of microscopic pressure.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a plasticizing device for an injection molding machine.

(Prior Art) Conventionally, in an injection molding machine, back pressure during plasticization was controlled only by a large-capacity injection cylinder.

For this reason, it has been difficult to realize delicate movements. Also, because force was only applied in a certain direction, it was not possible to compensate for the occurrence of a large force in the opposite direction.
This caused a decrease in the accuracy of back pressure and rotational speed.

(Problems to be Solved by the Invention) In view of the problems of the prior art, a screw is fixed to the injection cylinder of an injection molding machine, and a new small cylinder is added to increase the number of revolutions of the screw during plasticization. This is intended to enable accurate control of back pressure.

(Solving Means by the Invention) A screw is fixed to a piston of a hydraulic cylinder via a connecting rod and a connecting member, and a small hydraulic cylinder is attached to a support plate of a hydraulic motor fixed to an end of the connecting member. The shaft of a small hydraulic cylinder is connected to the injection cylinder via a guide bar, and a servo valve is used to drive the injection cylinder, small hydraulic cylinder, and hydraulic motor, and the amount of operation is controlled by the oil pressure, screw rotation speed, speed, etc. Using the detected values, a microcomputer-based control device calculates and controls it, making it possible to drive in either the left or right direction.

(Example) In FIG. 1, 1 is a mold, and 2 is a heating cylinder.

3 is a hopper, and resin is supplied from the hopper 3 into the heating cylinder 2. 4 is a band heater that heats the cylinder;
5 is a reservoir for molten resin. 6 is a screw that connects the support plate 18 on the right side of the injection cylinder 7 with a connecting rod 20.
' via a connecting member 18a. The injection cylinder 7 injects the molten resin in the reservoir 5 toward the mold 1.

9. 9', 9', 9'''' are pressure detectors, 9 indicates the resin pressure Po of the reservoir, 9' indicates the back pressure PB of the screw 6, 91 indicates the auxiliary cylinder pressure Pc, and 9' indicates the hydraulic pressure. Detects the supply pressure Pm of the motor. 10 is a position detector, which detects the position Q of the screw. 11 is a speed detector, which detects the retraction speed V of the screw 6. 12 is a rotation speed detector, which detects the screw position Q. 14 is a servo valve, which is installed between the hydraulic motor 21 and the hydraulic pump 16. 17 is an oil tank. 14' is also a servo valve, which connects the injection cylinder 7 and the hydraulic pump 16. 8 is a temperature detector, which detects the temperature θC of the heating cylinder. 15 is a control device.

13 is a small cylinder attached to a support plate 18 fixed to the right end of the injection cylinder, and one end of the shaft 13a is attached to the support plate 18.
The guide bar 19 is fixed to the guide bar 19 and is driven by a small servo valve 141.

pressure detector 9, screw axial speed detector 11,
Detection signals from the position detector 10 and the hydraulic motor rotation speed detector 12 are input to a control device 15 composed of a microcomputer, and the servo valves 14, 14', 1
The operation amount 11j12Pi3 of 4' is calculated to control the hydraulic motor 21, the injection cylinder 7, and the small cylinder 13.

(Operation) Prior to plasticization, the operation amount 12 of the servo valve 14' is set to the negative maximum value, so that the oil in the Iro cylinder 7 flows into the tank 17.
A small cylinder 13 is used to control minute pressure. That is, the position of the injection cylinder 7 when the screw 6 moves forward is shown in FIG. 2, and the position of the injection cylinder 7 when the screw retreats is shown in FIG. 3, in a plasticized state.

FIG. 4 shows temporal changes in the flow rate of oil returning to the tank 17 during plasticization. In the case of the present invention, it is shown as a solid line.

uni, the small cylinder 1 is connected to the flow rate Q from the injection cylinder 7.
As a result of being able to realize highly accurate control in addition to the flow rate q1 by the control in step 3, the accuracy of the pressure also increases. The dotted line Q shows the case of conventional control using the injection cylinder 7 and servo valve, and the range of fluctuation is large because a large capacity drive device is used to control minute pressure.

Furthermore, since the rotational speed of the screw 6 is directly affected by the back pressure, the accuracy of the rotational speed of the screw 6 is also improved by controlling the backpressure according to the present invention, and as a result, the entire plasticizing process is controlled with high accuracy. Note that inside the control device 15, the detected value is used to set 1zP6 kti to 1x=-k>1Pa-.
Pc kx*Pm- to 1sV-kxa n + b
tt n? + b 12Payla=kzxPa-2
zP6 k23Pc kz4Pm-kBV-kza
n+bzinr+b22Pbr.

ia=-1(31po-k)mpl) k33Pc-
kasPm-, 5vk3* n + b sx n
+ b 32 Pyy is calculated to constitute a feedback control system. However, 1□~1cis represents the feedback coefficient, nr, Pl, and y represent the target values of the screw rotation speed and back pressure, respectively, and bi□~b3
t represents a constant. Further, the position α is used to switch the target value depending on the position of the screw.

(Effect) The screw is fixed to the piston of the hydraulic cylinder via the connecting rod and the connecting member, and a small hydraulic cylinder is attached to the hydraulic motor support plate fixed to the end of the connecting member, and the shaft of the small hydraulic cylinder is attached to the hydraulic motor support plate fixed to the end of the connecting member. was connected to the injection cylinder via a guide bar. With this structure, the back pressure during plasticization was conventionally controlled only with a large-capacity injection cylinder, making it difficult to realize delicate movements, but the present invention makes it possible to make fine adjustments. .

[Brief explanation of the drawing]

FIG. 1 shows an injection molding apparatus to which the present invention is applied. Figure 2 shows the position of the cylinder when the screw moves forward. FIG. 3 also shows the position of the cylinder when the screw is retracted. FIG. 4 shows a diagram of changes in oil flow rate during plasticization. In the figure; 1 mold 2 heating cylinder 3 hopper
4 Band heater 5 Reservoir 6 Screw 7 Injection cylinder 8 Temperature detector 9 Pressure detector 10 Position detector 11 Speed detector 12 Rotational speed detector 13 Small cylinder 14 Servo valve 15 Control device
16 Hydraulic pump 17 Oil tank 18
Support plate 19 Guide bar 20 Connecting rod 21
Hydraulic motors and above Applicant Sumitomo Heavy Industries, Ltd. Sub-Agent Patent Attorney Isamu Ohashi Figure 2 Figure 3 B Figure 4 0 Hours

Claims (1)

[Claims] A screw is fixed to a piston of a hydraulic cylinder via a connecting rod and a connecting member, and a small hydraulic cylinder is attached to a support plate of a hydraulic motor fixed to an end of the connecting member, and the shaft of the small hydraulic cylinder is fixed to the piston of a hydraulic cylinder through a connecting rod and a connecting member. is connected to the injection cylinder via a guide bar, and a servo valve is used to drive the injection cylinder, a small hydraulic cylinder, and a hydraulic motor, and the operation amount is determined by a microcomputer using detected values such as oil pressure, screw rotation speed, and speed. A plasticizing device for an injection molding machine, characterized in that it is controlled by a control device according to the invention.