JP2001179786A - Injection molding machine having multipoint gate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection molding machine having multipoint gate constituted so as to control injection timing corresponding to the flow irregularity of a resin. SOLUTION: An injection molding machine having a multipoint gate is constituted so as to include a mold 12 demarcating a cavity corresponding to the shape of an injection-molded product to be injection-molded, an injection part 13 for injecting a molten resin in the cavity through a plurality of valve gates 16, 17, a plurality of the pressure sensors 14 provided in the flow route of the molten resin in the cavity, and a control part 15 opening the valve 17a of the valve gate 17 on the basis of the flow detection signal of the molten resin of each pressure sensor 14 in such a state that the molten resin is injected in the cavity through one valve gate 16.

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 having a multipoint gate.

[0002]

2. Description of the Related Art Conventionally, when molding an injection molded article having a relatively large shape, an injection molding machine having a multipoint gate has been used in order to flow a molten resin through the entire cavity of a mold. An injection molding machine having such a multipoint gate is configured, for example, as shown in FIG. In FIG. 4, an injection molding machine 1 having a multi-point gate includes a mold 3 defining a cavity 2 corresponding to the shape of an injection-molded product to be injection-molded, and a molten resin in the cavity 2 of the mold 3. And a cylinder 4 for injection. The mold 3 is divided by a predetermined dividing line, is supported so as to be openable and closable, and is configured to be closed with a predetermined pressure when closed. The cylinder 4 is configured to inject the supplied molten resin into the cavity 2 of the mold 3 through a valve gate described later.

In the case shown in the figure, the mold 3 has a plurality of (two in the drawing) valve gates 5 and 6 for injecting the molten resin into the cavity 2. The valve gates 5 and 6 are configured to be opened and closed by valves 5a and 6a, respectively. These valves 5
a and 6a are controlled to be opened and closed by a valve gate controller 7. The valve gate controller 7 controls the injection timing of the molten resin into the cavity 2 by controlling the driving of the valves 5a and 6a based on the position of the cylinder 4 and the like.

According to the injection molding machine 1 having such a configuration,
By closing the mold 3 and clamping the mold at a predetermined pressure to seal the cavity 2, the cylinder 4 is driven to drive the molten resin from the cylinder 4 into the cavity 2 through the valve gates 5 and 6. Inject.

At this time, the valve gate controller 7
Determines the injection timing corresponding to the injection state of the resin based on the position of the cylinder 4 and the like, and opens the valves 5a and 6a to inject the molten resin into the cavity 2 according to the injection timing. In this way, the injection timing is controlled in accordance with the injection state of the molten resin, and the expected joining position (the so-called weld position) of the flowing resin from each of the valve gates 5 and 6 in the cavity 2 is determined.
, The quality of the injection-molded product 8 molded in the cavity 2 is stabilized.

[0006]

However, in the injection molding machine 1 having such a configuration, the injection timing is controlled according to the injection state of the resin. The flow front position of the molten resin changes due to the difference in the flow state due to the flow variation. For this reason, the weld position of the flowing resin from each of the valve gates 5 and 6 may be deviated from a desired position, so that the molding failure rate increases and the quality of the injection molded product becomes unstable.

SUMMARY OF THE INVENTION In view of the foregoing, it is an object of the present invention to provide an injection molding machine having a multi-point gate in which the injection timing is controlled in accordance with the resin flow variation.

[0008]

According to the present invention, there is provided a mold for defining a cavity corresponding to the shape of an injection-molded article to be injection-molded, and a plurality of valve gates in the cavity. An injection unit for injecting molten resin, a plurality of sensors provided in a flow path of the molten resin in the cavity, and opening and closing valves of each valve gate based on a molten resin flow detection signal of each sensor. This is accomplished by an injection molding machine having a multi-point gate including a controller. In the injection molding machine according to the present invention, preferably, the sensor is a pressure sensor, which detects a pressure due to the flow of the molten resin and outputs a flow detection signal. In addition, the injection molding machine according to the present invention is preferably arranged such that the control unit injects the molten resin into the cavity through one valve gate, and the other valve gates based on the flow detection signal from each sensor. Open the valve.

According to the above configuration, the flow state of the molten resin actually injected into the cavity is detected by a sensor, preferably a pressure sensor. For example, when the pressure sensor detects a pressure equal to or higher than a predetermined pressure, this is detected. As the injection timing, the control unit opens the valve of each valve gate to inject the molten resin from each valve gate into the cavity.

As a result, the molten resin is injected into the cavity in accordance with the flow state of the molten resin in the cavity, instead of the injection state of the molten resin as in the prior art. However, since the injection timing of each valve gate can be determined according to the flow state, the weld position of the molten resin from each valve gate can always be controlled to a desired position in the cavity. Therefore, even when a resin having a large flow variation is used, for example, in the case of a recycled material, it is possible to eliminate a shift in a weld position of a molten resin due to a flow variation and to reduce molding defects of an injection molded product. The quality of the injection molded product can be stabilized.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings. FIG. 1 shows a schematic configuration of a first embodiment of an injection molding machine having a multipoint gate according to the present invention. In FIG. 1, an injection molding machine 10
A mold 12 defining a cavity 11 corresponding to the shape of an injection-molded product to be injection-molded, a cylinder 13 for injecting a molten resin into the cavity 11 of the mold 12, and provided in the cavity 11. And a control unit 15 for controlling the injection of the molten resin from the cylinder 13 into the cavity 11.

The mold 12 is divided by a predetermined dividing line, is supported so as to be openable and closable, and is configured to be clamped at a predetermined pressure when closed. The cylinder 13 is configured to inject the supplied molten resin into the cavity 11 of the mold 12 through a valve gate described later.

In this case, the mold 12 has a plurality of (two in the drawing) valve gates 16 and 17 for injecting the molten resin into the cavity 11 in the case shown in the figure. Gates 16 and 17 are each connected to a valve 16
a, 17a. The opening and closing of these valves 16a and 17a are controlled by the control unit 15 described above.

The sensor 14 is a pressure sensor in the case of the drawing, and is disposed in a flow path of the molten resin injected into the cavity 11. Thereby, each sensor 1
4 detects the pressure due to the flow of the molten resin.

The control unit 15 is configured as a valve gate controller in the case of the drawing, and
When the pressure value detected by the flow of the molten resin in the cavity 11 exceeds the predetermined value, the valves 16a,
The valve 17a is driven to open, and the injection timing of the molten resin into the cavity 11 is controlled. Here, the control unit 15 may be configured such that the detection signal of the pressure sensor 14 is directly or amplified by an amplifier and input, and the level of the detection signal of the pressure sensor 14 may be determined therein. Then, a determination circuit may be provided.

The injection molding machine 10 according to the embodiment of the present invention
With the above configuration, injection molding is performed as follows with reference to FIG. First, in FIG. 2A, at the same time as the start of injection, the control unit 15 (see FIG. 1) drives and opens the valve 16a. This allows
Molten resin 18 is injected from the cylinder 13 into the cavity 11 via the valve gate 16. Then, the molten resin 18 injected into the cavity 11 is
When it flows through the inside and reaches one pressure sensor 14a, the pressure sensor 14a detects the pressure due to the flow of the molten resin 18.

Here, as shown in FIG. 2B, the control unit 15 uses a detection signal from the pressure sensor 14a based on the time from when the valve 16a is opened to when the pressure sensor 14a detects the pressure. The flow velocity of the molten resin 18 to the pressure sensor 14a via the valve gate 16 is calculated, and at a predetermined weld position 19, both valve gates 16 and 1 are calculated.
The valve 17a of the valve gate 17 is set so that the injection timing is such that the flow of the molten resin 18 from the nozzle 7 merges.
Is driven to open. As a result, as shown in FIG. 2C, in addition to the valve gate 16, the valve gate 1
Since the molten resin 18 is injected into the cavity 11 even through 7, the molten resin 18 injected from each of the valve gates 16 and 17 merges in the cavity 11.

In this case, the joining position of the molten resin is determined by the control unit 15 controlling the valve 17a of the valve gate 17 while monitoring the flow state of the molten resin 18 injected into the cavity 11 from the valve gate 16. It is set at the weld position 19 described above. Accordingly, even if the flow state of the molten resin 18 varies, the valve opening control of the valve 17a is performed based on the flow state. Of the molten resin 18 merge.

Conversely, the control unit 15 appropriately controls the opening timing of the valve 17a of the valve gate 17, that is, the injection timing from the valve gate 17, so that the control unit 15 can move the valve 17 to an arbitrary position in the cavity 11. The weld position 19 can also be moved.

The control of the injection timing by the control unit 15 is performed based on the flow of the molten resin 18 injected into the cavity 11 during the injection molding of the injection molded article in the cavity 11. The occurrence rate of defects in the injection molded product due to the fluctuation of the flow state of the molten resin 18 is reduced, and the quality of the injection molded product is improved. Thereby, particularly when a recycled material having a large flow variation is used, the cavity 11 of the molten resin 18 from the valve gates 16 and 17 is always kept at a desired weld position 19.
Injection into the inside is performed, and a high quality injection molded product is injection molded. In the above description, first, the valve 16a of the valve gate 16 is opened, and the pressure sensor 1 is opened.
4a, the flow of the molten resin 18 is detected, but not limited to this.
7a is opened and the molten resin 1 is detected by the pressure sensor 14a.
8 may be detected.

FIG. 3 shows the configuration of a second embodiment of the injection molding machine according to the present invention. 3, the injection molding machine 20 is the same as the injection molding machine shown in FIG. 1 except that three valve gates 21, 22, 23 for injecting the molten resin 18 into the cavity 11 are provided. It has the same configuration as the machine 10.

According to the injection molding machine 20 having such a configuration, first, at the same time as the start of the injection, the control section 15 drives and controls the valve 21a of the valve gate 21 to open the valve. Thereby, the molten resin 18 is injected from the cylinder 13 into the cavity 11 via the valve gate 21. And
When the molten resin 18 injected into the cavity 11 flows in the cavity 11 and reaches one of the pressure sensors 14a, the pressure sensor 14a detects the pressure due to the flow of the molten resin 18 and the control unit 15 Second valve gate 2
The second valve 22a is opened.

Thus, the molten resin 18 is injected into the cavity 11 through the valve gates 21 and 22.
Then, the molten resin 18 injected into the cavity 11
Flows through the cavity 11 and the other pressure sensor 14
b, the pressure sensor 14b
The control unit 15 opens the valve 23a of the third valve gate 23 by detecting the pressure due to the flow of.

Here, the control unit 15 controls the pressure sensor 14
a, the flow rate of the molten resin 18 is calculated based on the time from when the valve 21a is opened to when the pressure sensor 14a, 14b detects the pressure. The valve 23a of the valve gate 23 is driven and opened so that the injection timing is such that the flows of the molten resin 18 from the 21, 22, and 23 merge.

As a result, the three valve gates 21 and
Since the molten resin 18 is injected into the cavity 11 through the cavity 2, 23, the molten resin 18 injected from each of the valve gates 21, 22 and 23 joins in the cavity 11.
In this case, the joining position of the molten resin is determined by the control unit 15 while monitoring the flow state of the molten resin 18 injected into the cavity 11 by the valves 22a, 23 of the valve gates 22, 23.
By controlling a, it can be set to the weld position described above. As a result, even if the flow state of the molten resin 18 varies, the valves 22a and 23a are controlled to open based on the flow state.
Always at the desired weld position, each valve gate 21,
The molten resin 18 from 2 and 23 joins.

As described above, according to the injection molding machines 10 and 20 of the present invention, even if a flow variation occurs due to a difference in the flowability of the injected molten resin, the flow state of the molten resin is changed. Since monitoring is performed by the pressure sensor provided in the flow path, the valve opening timing of the other valve gates, that is, the injection timing is determined according to the flow state of the actually injected molten resin, Since a constant weld position is always obtained, the incidence of defective injection molded products can be reduced, and injection molded products of good quality can be molded.

In the above-described embodiment, in any of the injection molding machines 10 and 20, first, the valves 16a and 21a of the valve gates 16 and 21 located above in the drawing are opened to start injection. Although the flow state of the molten resin 18 injected from the valve gates 16 and 21 is monitored, the present invention is not limited to this, and the valve of any valve gate is opened to monitor the flow state of the molten resin. Obviously, another valve gate may be opened according to the flow state. In the above-described embodiment, the flow state of the molten resin 18 in the cavity 11 is detected by the pressure sensor 14. However, the present invention is not limited to this. , Any other type of sensor can be used.

[0028]

As described above, according to the present invention,
The flow state of the molten resin actually injected into the cavity is detected by a sensor, preferably a pressure sensor.For example, when the pressure sensor detects a pressure equal to or higher than a predetermined pressure, this is set as injection timing, and the control unit sets each valve gate to The molten resin is injected into the cavity from each valve gate by opening the above valves. Thus, even if there is a variation in the flow of the molten resin, the molten resin is injected into the cavity in accordance with the flow state of the molten resin in the cavity, instead of the injection state of the molten resin as in the related art. Since the injection timing of each valve gate can be determined according to the flow state, the weld position of the molten resin from each valve gate can always be controlled to a desired position in the cavity. Therefore, eliminating the displacement of the weld position of the molten resin,
It is possible to reduce molding defects of the injection molded product and to stabilize the quality of the injection molded product. Thus, according to the present invention, there is provided an injection molding machine having an extremely excellent multi-point gate, wherein the injection timing is controlled in accordance with the flow variation of the molten resin.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a configuration of a first embodiment of an injection molding machine according to the present invention.

FIG. 2 is a schematic view sequentially showing a valve gate opening / closing state during injection molding by the injection molding machine of FIG. 1;

FIG. 3 is a schematic sectional view showing the configuration of a second embodiment of the injection molding machine according to the present invention.

FIG. 4 is a schematic sectional view showing a configuration of an example of a conventional injection molding machine.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 injection molding machine 11 cavity 12 mold 13 cylinder 14 pressure sensor (sensor) 15 control unit (valve gate controller) 16, 17 valve gate 16a, 17a valve 18 molten resin 19 weld position 20 injection molding machine 21, 22, 23 valve Gate 21a, 22a, 23a Valve

Claims (3)

[Claims] 1. A mold for defining a cavity corresponding to the shape of an injection-molded article to be injection-molded, an injection section for injecting a molten resin into the cavity through a plurality of valve gates, A plurality of sensors provided in a flow path of the molten resin, and a control unit that controls opening and closing of valves of each valve gate based on a flow detection signal of the molten resin of each sensor. Injection molding machine with point gate. 2. The injection molding machine according to claim 1, wherein the sensor is a pressure sensor, and detects a pressure due to the flow of the molten resin and outputs a flow detection signal. 3. The method according to claim 1, wherein the control unit opens a valve of another valve gate based on a flow detection signal from each sensor while injecting the molten resin into the cavity through one valve gate. The injection molding machine according to claim 1, characterized in that: