JPH07276448A - Injection molding machine - Google Patents

Abstract

PURPOSE:To improve the resistance to wear of a screw and a heating barrel by disposing a controller rotating the screw at the given number of revolutions at the time of injection process. CONSTITUTION:The number of revolutions of a screw 3 is controlled by controlling the flow rate of pressure oil applied to a hydraulic motor 5 by means of a solid flow rate control valve 27. On the other hand, the number of screw revolutions corresponding to injection speed set values from respective speed setting devices 21a-24a is computed by a converter 28, and the computed result is transferred to the solenoid flow rate control valve 27 through a signal changeover device 25b. Also a signal from a screw revolution speed setting device 29 is input into the solenoid flow rate control valve 27 in place of a signal from the signal changeover device 25b, and in the case the signal from the revolution speed setting device 29 is input into the solenoid flow rate control valve 27, the screw revolution speed is controlled without anything to do with the injection speed of the screw 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding machine, and more particularly to an injection molding machine capable of improving the wear resistance of a screw and a heating barrel.

[0002]

2. Description of the Related Art Generally, in an injection molding machine, a screw is rotated in a plasticizing / measuring step, and the resin raw material from a resin inlet is transferred to the screw tip side by the rotation of the screw, and is accumulated in a heating barrel by this transfer. The screw is retracted by the pressure of the molten resin, and the plasticization measurement is completed. The screw is moved forward without being rotated during injection into the mold.

By the way, when the resin raw material contains a hard additive such as glass fiber or mica (mica), when the screw is advanced in the injection process, the top of the flight of the screw and the inner wall of the heating barrel are separated. There is a problem that the above-mentioned additive is sandwiched between them and wear of the inner wall of the heating barrel is accelerated.

Therefore, conventionally, by devising the base material and surface treatment of the members of the screw and the heating barrel,
We have adopted a method to improve wear resistance.

[0005]

Although it is possible to improve the wear resistance of the screw and the heating barrel to some extent by the conventional method, there is a certain limit to the effect, which is not always sufficient. is there.

The present invention has been made in view of the above points, and an object thereof is to provide an injection molding machine capable of improving the wear resistance of a screw and a heating barrel.

Another object of the present invention is to provide an injection molding machine capable of further improving the wear resistance of the screw and the heating barrel.

Still another object of the present invention is to provide an injection molding machine capable of reducing wear of the heating barrel near the resin charging port.

[0009]

In order to achieve the above-mentioned object, the present invention provides a resin raw material from a resin charging port into a heating barrel, and a screw inserted into the heating barrel so as to be rotatable and retractable. An injection molding machine for plasticizing and measuring a resin raw material and injecting the resin raw material into a mold is characterized in that a control device for rotating a screw at a predetermined rotation speed is provided during an injection step.

Further, according to the present invention, the control device includes a converter for calculating and converting the screw rotational speed corresponding to the screw advancing speed during the injection process, and a controller for controlling the screw rotational speed by a signal from the converter. It is characterized in that it is configured from.

Further, the present invention is characterized in that a closing mechanism for closing the resin injection port is provided before the completion of the plasticizing and weighing.

[0012]

In the present invention, the control device drives the screw to rotate at a predetermined rotation speed during the injection process. That is, during the injection process, the screw not only advances, but also advances while rotating. Therefore, the amount of resin raw material that tries to get over the flight top of the screw is reduced,
It becomes possible to improve wear resistance.

Further, in the present invention, the control device is composed of a converter and a controller so that the screw rotation speed corresponding to the screw advancing speed can be obtained. Therefore, when the screw advances, there is no resin raw material that tries to get over the flight top of the screw, and it becomes possible to further improve wear resistance.

Further, in the present invention, a closing mechanism is provided so that the resin raw material is not supplied from the resin charging port at the time of plasticizing and measuring. Therefore, it is possible to prevent the heating barrel from being worn near the resin charging port.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of an injection molding machine according to the present invention. In the figure, reference numeral 1 is an injection molding machine. A screw 3 is inserted and arranged in a heating barrel 2 of the injection molding machine 1. The screw 3 is driven by an injection cylinder 4 in the axial direction by an injection stroke S, and a hydraulic pressure is applied. The motor 5 is driven to rotate.

On the base end side of the heating barrel 2, a resin charging port 2
a is provided, and on the tip side of the heating barrel 2,
A fixed mold 7 is attached via a fixed plate 6. A movable die plate 8 is arranged to face the fixed plate 6, and a movable die 9 is attached to a portion of the movable die plate 8 facing the fixed die 7. The movable mold 9 is moved to and from the fixed mold 7 by the mold clamping cylinder 10, and both molds 7 and 9 come into contact with each other to form a cavity 11 during mold clamping.

A position detecting device 12 for detecting the position of the screw 3 is installed on the screw 3, and the position detecting device 12 detects the position of the screw 3 while the injection stroke S is being moved. It has become.

In FIG. 1, reference numerals 13 to 16 are position setting devices, and these position setting devices 13 to 16 are
Any position between the injection strokes S can be set. Then, the detection value detected by the position detection device 12 and the values set in the position setting devices 13 to 16 are compared by the comparators 17 to 20, respectively, and when the detected value and the set value match. The comparators 17 to 20 output coincidence signals to the speed setters 21a to 24a.

Each of the speed setters 21a to 24a can set the injection speed (screw moving speed) to an arbitrary value, and the set injection is performed by inputting a coincidence signal from each of the comparators 17 to 20. The screw 3 is controlled so that the speed becomes the speed. That is, the injection stroke S
When, for example, the screw 3 passes through the position set in the position setting device 13 inside, the screw 3 is
It is controlled so that the injection speed is set to a.

The output signals from the speed setters 21a to 24a are input to the signal switching devices 25a and 25b, respectively,
The electromagnetic flow control valves 26 and 27 are controlled by the output signals from the signal switching devices 25a and 25b, respectively. The electromagnetic flow rate control valves 26 and 27 are held at the opening corresponding to the previous signal until the next signal is input.

The electromagnetic flow control valve 26 controls the flow rate of the pressure oil acting on the injection cylinder 4 to control the injection speed of the screw 3, and the electromagnetic flow control valve 27 controls the hydraulic motor. The rotational speed of the screw 3 is controlled by controlling the flow rate of the pressure oil that acts on the screw 5.

On the other hand, a converter 28 is set on the input side of the signal switching device 25b. The converter 28 has a screw rotation speed corresponding to the injection speed set value from each of the speed setters 21a to 24a. Is calculated and the calculation result is sent to the electromagnetic flow control valve 27 via the signal switching device 25b.

A signal from a screw rotational speed setting device 29 is input to the electromagnetic flow control valve 27 instead of the signal from the signal switching device 25b. The screw rotational speed setting device 29 is also provided. When the signal from is input to the electromagnetic flow control valve 27, the screw rotation speed is controlled regardless of the injection speed of the screw 3.

On the other hand, as shown in FIG. 2, a hopper 31 for accommodating the resin raw material 30 is connected to the resin charging port 2a of the heating barrel 2, and the resin charging port 2a is driven by an actuator 32. A shutter 33 is provided.

The actuator 32 includes a switching valve 34.
A pressure fluid source 35 is connected to the switching valve 34, and the switching valve 34 is switch-controlled by a command signal from a controller 36. The shutter 33 is normally open and closes before the completion of plasticizing and weighing.

Next, the operation of this embodiment will be described.
In the plasticizing and measuring step, the screw 3 is rotationally driven, and the rotation causes the resin raw material 30 from the hopper 31 to rotate.
Are transferred to the tip side of the screw 3. After that, the screw 3 is retracted by the pressure of the molten resin accumulated in the heating barrel 2 by this transfer, and the plasticization measurement is completed. After that, the screw 3 advances and injection into the molds 7 and 9 is performed.

However, when the resin raw material 30 contains a hard additive such as glass fiber or mica,
When the screw advances in the injection process, the above-mentioned additive is sandwiched between the flight top of the screw 3 and the inner wall of the heating barrel 2, and the abrasion of the screw 3 and the heating barrel 2 is accelerated.

However, in this embodiment, when the screw is advanced in the injection process, the screw 3 is rotated at a rotation speed corresponding to the injection speed.
Since it is rotated, the abrasion resistance of the screw 3 and the heating barrel 2 can be significantly improved. This will be described below.

When the screw 3 is rotated in the direction of arrow A at the time of advancing the screw in the injection process, the resin raw material 30 in the groove portion 37 of the screw 3 becomes
Transferred in the direction indicated by arrow B. When this transfer speed matches the forward speed of the screw 3, the resin raw material 30 is not subjected to the force that tries to get over the top of the flight 38 of the screw 3.

Next, the relationship between the injection speed and the corresponding screw rotation speed will be described. Generally, screw 3
Lead (pitch P) is P = D (screw diameter). Here, in order to facilitate understanding, when the injection speed is 1 m / min = 1000 mm / min and the screw diameter is D = 50 mm, the required rotation speed N is Becomes

The injection speed generally used is 3 to 6 m / m.
Since it is in, the rotation speed N of the screw 3 at that time is
From the above formula, 20 × (3-6) = 60-120 (rpm).

Therefore, the injection speed is 3 to 6 m / min.
In the case of the screw 3 having a diameter of 50 mm, the rotation speed N may be changed between 60 and 120 rpm.

By the way, in FIG. 1, the signal switching device 2
When the rotation speed of the screw 3 is controlled by the signal from the screw rotation speed setting device 29 instead of the signal from 5b, it is considered that the screw rotation speed does not match the injection speed. Then, for example, when the screw rotation speed is lower than the injection speed, some percentage of the resin raw material 30 will get over the top of the flight 38 as the screw 3 advances, and the resin raw material 30 that has passed over will cause some wear. It becomes a problem. However, compared with the case where the screw 3 is not rotated, the wear is extremely small, and the desired effect can be expected sufficiently.

Further, in the above embodiment, as shown in FIG. 2, the shutter 33 is closed before the completion of plasticizing and weighing. Therefore, it is possible to prevent abrasion of the heating barrel 2 near the resin charging port 2a. This will be described below.

When the shutter 33 is provided at the resin inlet 2a, it is structurally difficult to provide the shutter 33 close to the screw 3. Therefore, a space C is formed below the shutter 33 by the resin inlet 2a. Will be done.

Here, when the shutter 33 is closed after the completion of the plasticization measurement, the unmelted resin raw material 30 in the space C is dropped into the groove portion 37 of the screw 3 at the time of injection, and the dropped resin is dropped. The raw material 30 may cause abrasion of the heating barrel 2 near the resin charging port 2a.

However, in this embodiment, the shutter 33 is closed before the completion of the plasticizing and weighing, and the resin raw material 30 in the space C is
Since it is transferred to the front side of the screw 3 before the completion of plasticizing and weighing, there is no such problem as described above.

The inventors of the present invention have found that the injection molding machine 1 of the above-described embodiment is used.
Was used to injection-mold a resin containing PP (polypropylene) mica, which is a resin raw material in which abrasion of the screw 3 and the heating barrel 2 is particularly severe, and the degree of abrasion was measured.

As a result, it was confirmed that what was conventionally unstable in measurement after three months could sufficiently withstand long-term use, and it was found that abrasion resistance can be greatly improved.

[0040]

As described above, according to the present invention, the screw is not simply advanced during the injection process but is advanced while being rotated. Therefore, the wear resistance of the screw and the heating barrel can be improved. it can.

Further, according to the present invention, the number of revolutions of the screw during the injection process is made to correspond to the screw advancing speed, so that the abrasion resistance of the screw and the heating barrel can be further improved.

Further, since the resin charging port is closed before the completion of the plasticizing measurement of the present invention, it is possible to prevent the heating barrel from being worn near the resin charging port.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an injection molding machine according to an embodiment of the present invention.

FIG. 2 is an explanatory view showing details around a shutter of a resin charging port.

3A and 3B are explanatory views showing a relationship between an injection speed and a screw rotation speed.

[Explanation of symbols]

 1 Injection Molding Machine 2 Heating Barrel 2a Resin Injection Port 3 Screw 4 Injection Cylinder 5 Hydraulic Motor 7 Fixed Mold 9 Moving Mold 12 Position Detection Device 13, 14, 15, 16 Position Setting Device 17, 18, 19, 20 Comparator 21a, 22a, 23a, 24a Speed setting device 25a, 25b Signal switching device 26, 27 Electromagnetic flow control valve 28 Converter 29 Screw rotation speed setting device 30 Resin raw material 33 Shutter 36 Controller 37 Groove 38 Flight

Claims (3)

[Claims] 1. A resin raw material is supplied from a resin charging port into a heating barrel, and the resin raw material is plasticized and measured by a screw fitted in the heating barrel so as to be rotatable and retractable, and is injected into a mold. In the injection molding machine, the injection molding machine is provided with a control device for rotating the screw at a predetermined rotation speed during the injection process. 2. The control device comprises a converter for calculating and converting the screw rotational speed corresponding to the screw advancing speed during the injection process, and a controller for controlling the screw rotational speed by a signal from this converter. The injection molding machine according to claim 1, wherein: 3. A resin raw material is supplied into the heating barrel from a resin charging port, and the resin raw material is plasticized and metered by a screw fitted in the heating barrel so as to be rotatable and retractable, and is injected into a mold. In the injection molding machine, the injection molding machine is provided with a closing mechanism for closing the resin injection port before the completion of the plasticizing and weighing.