JPH0427517A - Plasticator of injection molding machine - Google Patents

Abstract

PURPOSE:To improve precision of a stop position, by a method wherein operation of a deceleration starting position is performed with a backward movement position of a screw and a deceleration slope by making use of a backward movement speed of the screw and after arrival at the operated deceleration starting position, a rotary speed of the screw is decelerated. CONSTITUTION:A deceleration starting position of a screw 2 is operated based on a backward movement speed of the screw 2 by a deceleration slope and backward movement position (measuring position) of the screw 2 established beforehand by a control device 26. Then when the screw 2 arrives at the obtained deceleration starting position, a control signal based on the deceleration slope is put out. Driving force of a driving device 11 turning and driving the screw 2 is adjusted and a rotary speed of the screw 2 is decelerated so that the rotary speed of the screw 2 is coincident with the deceleration slope. With this contraction, measuring accuracy of resin is improved and an injection quantity at the next shot is made correct, through which precision of a molded product is improved effectively.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention relates to an in-line screw type injection molding machine.
In particular, the present invention relates to an in-line screw injection molding machine equipped with a control mechanism for increasing metering accuracy in screw rotation control for metering raw resin.

(B) Conventional technology Traditionally, injection molding machines have been used to rotate a screw fitted in a heating cylinder to plasticize a predetermined resin material, and at the same time, to retract the screw itself in the axial direction. , an in-line screw type in which plasticized resin material is accumulated in the space in front of the screw, and the screw is used as an injection ram, and the accumulated resin material is injected by the forward movement of the screw. Injection molding machines are known. By the way, the measurement of the injected resin in such an injection molding machine is considered important in obtaining a good product. In other words, the quality of the resin measurement greatly affects the quality of the product. Insufficient measurement may result in short shots or hairs, while too much measurement may result in cracks, etc. This is the cause of defective products.

For this reason, various weighing mechanisms have been studied for some time.
In reality, by installing a limit switch at the measurement completion position or by reading the position set by a position detector such as an encoder, potentiometer, etc., the electric or hydraulic motor that rotates the screw is stopped and the measurement is performed. A mechanism is adopted to ensure completion.

However, these devices continued to rotate even after the stop signal was received due to the inertia of the screw drive system, and due to differences in resin resistance, etc., the stop positions varied, resulting in poor metering accuracy.

Therefore, in order to solve the above-mentioned problems, JP-A-61-1
In Publication No. 58417, a predetermined deceleration slope is set in advance regardless of the screw rotation speed, a deceleration start position is calculated from the screw retraction limit set value and the deceleration slope from the screw rotation speed, and deceleration is started based on the input of the screw position signal. The screw rotation speed is reduced when the position is reached. Alternatively, a technique has been disclosed in which the back pressure is increased.

(c) Problems to be Solved by the Invention In the above technology, the deceleration slope is semi-fixed because it is unique to the size of the molding machine, that is, the inertia of the screw system.
According to the deceleration slope applied from the screw rotational speed, a deceleration start position before the screw retraction part is calculated, and the screw rotational speed is decelerated from the calculated position.

However, if the position of the deceleration slope is determined by the screw rotation speed, the actual screw retraction speed will vary depending on the resin properties, back pressure, etc. Without this, it would be difficult to stop at a fixed position, and there is a possibility that it would stop in front of the weighing position or go too far.

This is because if you focus only on the screw rotation speed,
When the back pressure setting is high, the screw retraction speed is slow even if the screw rotation speed is high; when the back pressure setting is low, the screw retraction speed is slow.
This means that the screw retracts at a high speed, and if the screw is decelerated at a certain deceleration slope, it will not be able to stop at the weighing position even if the screw retracts at a high speed. Furthermore, if the deceleration slope is set to suit a vehicle with a high backward speed, there is a problem in that it takes a long time to stop.

The present invention aims to solve such problems.

(d) Means for Solving the Problems The present invention provides a driving means for rotationally driving a screw 2 fitted in a heating cylinder 1 of an injection molding machine, and a screw 2 for retracting in the axial direction according to the rotational drive by the driving means. screw speed and position detection means for detecting the position and speed of the screw 2; screw retraction position setting means for presetting a screw retraction limit based on the injection amount; Based on the deceleration slope setting means to be set and the screw retraction speed, a deceleration start value 1 before the screw retraction position is determined according to the screw retraction position set by the screw retraction position setting means and the deceleration slope set by the deceleration slope setting means. a control device 26 which outputs a control signal based on the deceleration slope when the screw 2 reaches the deceleration start position based on the position output of the screw speed and position detection signal; The above problem is solved by having a deceleration means that adjusts the drive power of the drive means in accordance with a control signal from the drive means and decelerates the rotational speed of the screw in accordance with the deceleration slope.

(e) In the in-line screw type injection molding machine according to the present invention, as in function 2, the control device controls the speed based on the preset deceleration slope and the screw retraction speed from the screw retraction position (measured value N). A deceleration start position of the screw is calculated, and when the screw reaches the obtained deceleration start position, a control signal based on the deceleration slope is outputted to adjust the driving power of the drive means for rotationally driving the screw. , thereby reducing the rotational speed of the screw to match the deceleration slope.

This improves resin metering accuracy, and
As a result, the injection amount in the next shot becomes accurate, and the precision of the molded product is effectively improved.

(f) Example Examples will be described based on the drawings.

In FIG. 1, 1 is a heating cylinder of an electric injection molding machine, and a screw 2 fitted into the heating cylinder 1 has a connecting shaft 3.
A drive shaft 4 is connected via. At the rear end of the drive shaft 4, a ball screw 7 is attached to a pole nut 6 which is slidably but non-rotatably supported in a housing (not shown) in the axial direction.
A ball screw mechanism 8 screwed together is connected via a thrust bearing 5, and the rear end of the ball screw 7 is connected to an output shaft 10 of an injection motor 9.
As a result, as the ball screw 7 rotates forward and backward, which is rotated forward and backward by the injection motor 9 controlled by the control device 26 via the driver unloader 724, the pole nut 6 moves forward or backward in the axial direction, and the screw 2 is moved forward or backward via the drive shaft 4 and the connecting shaft 3.

On the other hand, a plasticizing motor 11 having a rotating shaft 14 parallel to the drive shaft 4 is provided, and a flanged gear 16 with flanges 15 on both sides is provided on the rotating shaft 14 via a ball spline 17. A gear 18 fixed to the drive shaft 4 is meshed with the flanged gear 16 while being sandwiched between the tails 5 on both sides.This causes the plasticizing motor to be controlled by the control device 26 via the driver amplifier 25. The rotation of 1 is
Transmitted to the drive shaft 4 through the rotating shaft 14, the flange gear 6 and the gear 18, the screw 2 is rotated through the connecting shaft 3, and the drive shaft 4 and As the gear 18 moves in the axial direction l\, the flanged gear 16 slides back and forth on the rotation shaft 14 via the ball spline 17. As a result, no matter what position the screw 2 is in as it advances or retreats, the rotation of the plasticizing motor 11 is transmitted to the gear 18 by the gear 16. Further, the connecting shaft 3 has a speed position detector 19 for detecting the speed and position of the screw 2.

FIG. 2 shows setting devices in the control device 26, including a screw rotation speed setting device 26a for setting the screw rotation speed and a screw retraction position setting device 26b for setting the screw retraction position.
This constitutes a deceleration slope setting device 26c that sets the deceleration slope.

In the injection device configured as described above, the plasticizing motor 1
When the metering operation is performed in step 1, the resin is metered and accumulated on the tip side of the screw 2, and the screw 2 is accordingly retracted. This retraction speed is determined by the resin properties, the back pressure applied by the injection motor 9, the amount of heating of the heating cylinder 1, the screw rotation speed, etc. This screw retraction speed is detected by the speed position detector 19 (for example, a linear encoder), and the screw retraction position set in advance by the setters 26b and 26c and the deceleration start position before the screw retraction position from the deceleration slope are determined. The speed position detector 19 detects that the calculated position has been reached, and outputs a control signal from the control device 26 based on the deceleration slope to adjust the screw rotation speed to the deceleration slope. 7 The deceleration slope is determined by the inertia of the screw system. If the screw retraction speed is slow, the deceleration start point will inevitably be closer to the metering position.

An example is shown in FIG. This is an example where (high) means the speed is fast and (low) means the speed is slow.

In the above-described system, the screw retraction speed is detected by one speed position detector, but the calculation may be performed using a signal obtained from the output of the rotary encoder 20 attached to the rear end of the injection motor 9.

Similar effects can also be obtained with a hydraulically driven motor.

(G) Effects of the Invention The present invention uses the screw retraction speed to calculate the deceleration start position based on the screw retraction position and the deceleration slope, and after reaching the calculated deceleration start position, the screw rotation speed is reduced. By decelerating the screw, the accuracy of the stop position can be improved by simply controlling the screw rotation speed, compared to deceleration control using the screw rotation speed, where the stop position varies without back pressure control. Also, there is no loss in measurement time.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the injection device of the present invention, Fig. 2 is a diagram showing the setting device section of the control device of the present invention, and Fig. 3 is a diagram showing the relationship between screw retraction speed and screw stroke. This is a diagram. 1...Heating part, 2...Screw, 3.Connection shaft,
4... Drive shaft, 5... Thrust bearing,
6...Pole nut, 7.Ball screw, 8...
Ball screw mechanism, 9... Injection motor, 10... Output shaft, 11... Plasticizing motor, 14... Rotating shaft, 15°'' collar, 16... Gear with collar, 17...
・Ball spline, 18...Gear, 19...Speed position detector, 2o, 210-Tary encoder,
24.25...Driver amplifier, 26...Control device, 26a/Screw rotation speed setting device, 26b...
・Screw retraction position setter, 26c...Deceleration slope setter. Patent applicant: Japan Steel Works, Ltd. Representative: Naohiko Yagi! W2J! 1 3rd B

Claims (1)

[Claims] A screw (2) fitted in a heating cylinder (1) of an injection molding machine.
), and the screw (2) retreats in the axial direction according to the rotational drive by the drive means.
screw speed and position detection means for detecting the position and speed of the screw, screw retraction position setting means for presetting a screw retraction limit based on the injection amount, and presetting a predetermined deceleration slope regardless of the screw retraction speed. a deceleration slope setting means, and from the screw retraction speed, calculating a deceleration start position before the screw retraction position according to the screw retraction position set by the screw retraction position setting means and the deceleration slope set by the deceleration slope setting means; , a control device (26) that outputs a control signal based on the deceleration slope when the screw (2) reaches the deceleration start position based on the screw speed and the position output of the position detection signal.
), and adjusting the driving power of the driving means according to the control signal from the control device (26), and adjusting the rotational speed of the screw,
A plasticizing device for an injection molding machine, comprising a deceleration means for decelerating the speed in accordance with the deceleration slope.