JP3517769B2 - Gas supply system for injection molding machine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas supply system for an injection molding machine that performs gas-assisted injection molding, and more particularly to a gas generator for generating a gas such as nitrogen gas and a gas generator for supplying the gas. The present invention relates to a gas supply system having a gas compression device for controlling the pressure (compression) of the generated gas.

[0002]

^2. Description of the Related Art A molten resin is injected into a cavity of a mold, and before the resin in the cavity is solidified, a high-pressure gas (usually an inert gas) of about 100 to 300 kgf / cm ² is injected into the resin. In the gas-assisted injection molding that injects (nitrogen gas is used), a holding pressure is applied to the resin from the inside of the resin and the surface side of the resin is pressed against the inner wall surface of the cavity, so a good product without sink marks is molded. In addition, since the hollow portion is formed inside the molded product, the weight of the molded product can be reduced.

In an injection molding machine for performing such gas-assisted injection molding, conventionally, high-pressure gas from a large-capacity high-pressure gas tank (high-pressure gas cylinder) is normally injected by a pressure reducing valve (pressure control valve). The gas pressure value was adjusted so that the gas was injected into the molten resin in the cavity.

However, when a large-capacity high-pressure gas tank is used, the scale of equipment becomes large and the legal regulation also increases. Furthermore, in order to replenish the high-pressure gas, high-pressure gas (high-pressure gas cylinder) must be purchased, which increases running costs.

Therefore, in order to solve the problems caused by using a large-capacity high-pressure gas tank, the applicant of the present application has controlled the small-scale nitrogen gas generator and the nitrogen gas supplied from this nitrogen gas generator to be boosted. It is equipped with a small-scale high-pressure gas tank for storing high-pressure nitrogen gas supplied from this gas compression device, and the gas pressure of the high-pressure gas tank with a small volume is desired by feedback control by the gas compression device. A gas supply system, which is designed to be accurately controlled by the pressure value, has been developed and proposed, for example, in Japanese Patent Application No. 8-8450.

[0006]

A gas supply system having the above-mentioned nitrogen gas generator, gas compressor, and high-pressure gas tank having a small capacity can be reduced in equipment scale.
Since it is not necessary to purchase nitrogen gas, running costs can be reduced.

However, since the small-capacity high-pressure gas tank has a small capacity and is replenished with a required amount in each molding cycle, there is no problem in forming a molded product having a normal hollow ratio. It was pointed out that when a molded product with a high hollow ratio is required, the amount of gas in a small-capacity high-pressure gas tank may be insufficient.

Further, depending on the molding conditions of the gas-assisted injection molding, gas injection from two different points is required, or two different injection gas pressures are required.
Gas injection or the like is required at three different timings, but no consideration has been given to this point in the prior art.

The present invention has been made in view of the above points,
It is an object of the present invention to provide a gas supply system that can handle gas-assisted injection molding of a molded product having a high hollow ratio. Further, the object of the present invention is to
Gas supply system that allows gas injection from two different locations, two different gas pressures, two different timings, and two different gas amounts. To provide.

[0010]

In order to achieve the above object, the present invention performs gas-assisted injection molding in which a molten resin is injected into a cavity of a mold and a high pressure gas is injected into the resin in the cavity. In a gas supply system attached to an injection molding machine, a gas generator, a gas compressor for controlling pressure (compression) of the gas supplied from the gas generator, and a high-pressure gas supplied from the gas compressor are stored. A small-capacity gas tank, a tank introduction control valve provided in the pipeline between the gas tank and the gas compression device, and a gas injection control provided in the pipeline between the gas tank and the gas introduction part of the injection molding machine. Two gas supply units equipped with valves are attached to one injection molding machine.
The gas tank and gas injection in each gas supply unit.
Connected to each other via the open / close control valve
Yes, take the configuration.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration of a gas supply system attached to an injection molding machine for performing gas-assisted injection molding according to an embodiment of the present invention.

In FIG. 1, 1 is an injection system mechanism of an injection molding machine, 2 is a mold opening / closing system mechanism of the injection molding machine, and a mold 2a in the mold opening / closing system mechanism 2 is clamped in the injection system. Molten resin is injected from the nozzle 1a in the mechanism 1 into the cavity of the mold 2a.

Reference numeral 3A denotes a first gas supply unit of the gas supply system, 3B denotes a second gas supply unit of the gas supply system, and the first and second gas supply units 3
A and 3B have the same configuration, and the same reference numerals are given to the same components of each unit.

First and second gas supply units 3A, 3B
In the above, 4 is a nitrogen gas generator, which continuously generates and outputs nitrogen gas from the supplied compressed dry air. 5
Is a gas compression device, which controls (compresses) the nitrogen gas (hereinafter, simply referred to as gas) supplied from the nitrogen gas generation device 4 through the check valve 6 to a set value. This gas compression device 5 includes a servomotor 7 that is feedback-controlled.
Is used as a drive source, and the boost cylinder device 8 has a function of compressing and controlling the gas pressure to a set pressure value. The measured gas pressure value of the gas pressure detection sensor 11 for detecting the gas pressure value in the small-capacity gas tank 10 will be described later. The servo motor 7 is feedback-controlled by the servo amplifier 9 so as to match the set gas pressure value. Each servo amplifier 9 is controlled by a system controller of an injection molding machine (not shown).

Reference numeral 10 denotes a small-capacity (for example, several tens to several hundreds cc) gas tank (small-capacity accumulator) for storing the high-pressure gas supplied from the gas compression device 5. The gas tank 10 and the gas compression device 5 are connected to each other. A gas tank introduction control valve (electromagnetic open / close control valve) 12 is provided in the pipeline between them. The gas tank introduction control valve 12 is used for the gas tank 10
When storing (introducing) high-pressure gas inside, it is opened,
It is closed when the high-pressure gas in the gas tank 10 is injected into the resin.

Reference numeral 13 is a gas injection control valve (electromagnetic open / close control valve) provided in a pipe line between the gas tank 10 and the gas introduction section 14A or 14B of the injection molding machine. In the present embodiment, the gas introduction part 14A is provided in the nozzle 1a of the injection system mechanism 1, and the gas introduction part 14A is provided.
B is provided in the mold 2 a of the mold opening / closing system mechanism 2. The gas injection control valve 13 is opened at least during the period when the high-pressure gas is injected into the resin. Reference numeral 15 is a gas discharge control valve (electromagnetic opening / closing control valve) provided in a pipe line between the gas injection control valve 13 and the gas introduction part gas introduction part 14A or 14B of the injection molding machine, and releases gas into the atmosphere. It is opened when doing, and closed at other times.

Reference numeral 16 denotes an inter-unit connecting pipe, which is a pipe between the gas tank 10 and the gas injection control valve 13 in the first gas supply unit 3A and the second gas supply unit 3B.
The pipe line between the gas tank 10 and the gas injection control valve 13 is connected, and the unit connection pipe 16 is provided with a unit connection control valve (electromagnetic opening / closing control valve or manual opening / closing control valve) 17. There is. The unit connection control valve 17 is opened when the gas of the first gas supply unit 3A and the gas of the second gas supply unit 3B are added and the gas is injected from one gas introduction portion, and otherwise is opened normally. Will be closed.

FIG. 2 shows the first and second gas supply units 3
It is a principal part sectional view which shows the structure of the pressure | voltage rise cylinder apparatus 8 of the said gas compression apparatus 5 in A, 3B. As shown in the figure, in this embodiment, two pressure | voltage rise cylinder apparatuses are mounted on one trolley | bogie 20. 8 (pressurizing cylinder device 8 of the first and second gas supply units 3A and 3B) are mounted adjacent to each other.

In FIG. 2, 21 is a pair of first compression cylinders, 22 is a piston body moving in the first compression cylinder 21, 23 is a piston rod having one end fixed to the piston body 22, and 24 is a piston rod. Second compression cylinder, 25
Is a piston body that moves in the second compression cylinder 24, 2
6 is a ball screw shaft having one end fixed to the piston body 25, and 27 is the other end of the piston rod 23 and the ball screw shaft 2
6 is a connecting plate to which the other end of 6 is fixed, 28 is a nut body screwed to the ball screw shaft 26, 29 is a bearing that rotatably holds the nut body 28, and 30 is a driven pulley fixed to the nut body 28.

The driven pulley 30 is adapted to transmit the rotational force of the servomotor 7 via a timing belt (not shown). When the driven pulley 30 rotates, a nut body 28 integrated with the driven pulley 30 is provided. Also rotates. Nut body 2
When 8 rotates, ball screw shaft 2
6 moves forward or backward, and each member 25, 26, 27, 23, 22 connected to the ball screw shaft 26 moves forward or backward.

Gas is fed from the nitrogen gas generator 4 into the first compression cylinder 21, and the piston body 22 of the first compression cylinder 21 is moved from the state shown on the right side in FIG. When driven in the direction of arrow A,
The gas compressed (pressurized) to a predetermined gas pressure value by the first compression cylinder 21 is sent to the second compression cylinder 24. When the piston body 25 of the second compression cylinder 24 is driven in the direction of arrow B from the state shown on the left side in FIG. 2, the second compression cylinder 24 further compresses (pressurizes) the gas pressure to a predetermined gas pressure value. The gas is sent to the gas tank 10 through the gas tank introduction control valve 12 in the open state.

Next, the operation of the gas supply system of this embodiment having the above configuration will be described. First, the operation of adding the gas of the first gas supply unit 3A and the gas of the second gas supply unit 3B and injecting them from one gas introduction part will be described. At this time, the unit connection control valve 17 is always set to the open state.

When storing gas in each gas tank 10 of the two gas supply units 3A and 3B, each gas tank introduction control valve 12 with each gas injection control valve 13 closed.
And the pressurized gas is sent from the respective gas compression devices 5 to the two gas tanks 10. On this occasion,
The gas pressure set values of the two gas tanks 10 are set to be equal, and as described above, by the feedback control,
Gas having a predetermined gas pressure value is stored in the two gas tanks 10.

Then, each gas tank introduction control valve 12 is closed at an appropriate timing before the gas injection start timing in each cycle. At this time, each gas discharge control valve 15 is also closed. After that, at the gas injection start timing immediately after the molten resin is injected into the cavity of the mold 2a that has been clamped, the gas injection control valve 13 or the second gas supply of the first gas supply unit 3A is reached. Either one of the unit 3B gas injection control valves 13 is opened, and a predetermined amount of high-pressure gas in the two gas tanks 10 is injected into the resin before solidification, whereby a holding pressure is applied from inside the resin to the resin. It is given to. When the gas injection is completed, the opened gas injection control valve 13 is closed, and the holding pressure by the trapped gas is applied to the resin during the holding pressure period. Then, when the pressure-holding process ends, the gas discharge control valve 15 on the side that controls the opening and closing of the gas injection control valve 13 is opened, and gas is degassed from the solidified resin. In addition, the opened gas discharge control valve 15
Is closed after degassing is complete.

Further, when it is confirmed that the gas injection control valve 13 is closed, the respective gas tank introduction control valves 12 are opened, and two gas compressions are performed in the two gas tanks 10 whose pressure has been reduced as a result of injecting a predetermined amount of gas. The high-pressure gas supplied from the device 5 is introduced to increase the gas pressure value in the gas tank 10 to the set value again.

By repeating the above-mentioned operation, the gases of the first and second gas supply units 3A and 3B are added together and the gas is injected from one gas introduction portion 14A or 14B. Will be done.

As described above, when the gases of the first and second gas supply units 3A and 3B are added and injected from one gas introduction section 14A or 14B, the amount of gas injected into the resin is reduced. It is possible to obtain a sufficient amount, and it is possible to easily mold a molded product having a high hollow ratio.

The first and second gas supply units 3
Gas of the same pressure from A and 3B is introduced at two gas introduction parts 14
It is also possible to introduce into A and 14B, and in this case, when the gas of the first gas supply unit 3A and the gas of the second gas supply unit 3B are added together and injected from one gas introduction part Similarly, the unit connection control valve 17 is always set to the open state, and at the time of gas injection, the gas injection control valve 13 of the first gas supply unit 3A and the gas injection control valve 13 of the second gas supply unit 3B. If both are opened, the gas of the same pressure will be injected into the resin from the two gas introduction parts 14A and 14B. If you do this,
Even if the resin has a fast solidification due to a thin portion in the middle of the molded product, the gas can be injected into the resin from two locations, so that the gas can be quickly injected into the required area.

Next, the gas of the first gas supply unit 3A is supplied from the gas introduction section 14A to the second gas supply unit 3B.
The operation of independently injecting the above gas from the gas introducing unit 14B will be described. At this time, the unit connection control valve 17 is always set to the closed state.

When the gas is stored in each gas tank 10 of the two gas supply units 3A and 3B, each gas tank introduction control valve 12 with each gas injection control valve 13 closed.
And the pressurized gas is sent from the respective gas compression devices 5 to the two gas tanks 10. On this occasion,
The gas pressure set value of the gas tank 10 of the gas supply unit 3A and the gas pressure set value of the gas tank 10 of the gas supply unit 3B are set to different desired values, and the two gas compression devices 5 (servo motor 7) are The two gas tanks 10 are independently feedback-controlled, and the gas having the gas pressure value set corresponding to each gas is stored in the two gas tanks 10.

Then, each gas tank introduction control valve 12 is closed at an appropriate timing before the gas injection start timing in each cycle. At this time, each gas discharge control valve 15 is also closed. After this, at the gas injection start timing immediately after the molten resin is injected into the cavity of the mold 2a that has been clamped, the gas injection control valve 13 of the first gas supply unit 3A is opened,
The high-pressure gas in the gas tank 10 of the first gas supply unit 3A is injected into the resin before solidification by a predetermined amount from the gas introduction portion 14A provided in the nozzle 1a, and the gas of the second gas supply unit 3B is also supplied. The injection control valve 13 is opened,
The high-pressure gas in the gas tank 10 of the second gas supply unit 3B is injected into the resin before solidification by a predetermined amount from the gas introduction portion 14B provided in the mold 2a. At this time, the opening timing of the gas injection control valve 13 of the first gas supply unit 3A and the opening timing of the gas injection control valve 13 of the second gas supply unit 3B are controlled independently of each other,
It is possible to get the timing shifted by a minute second. As a result, a holding pressure is applied to the resin from the inside of the resin. When the gas injection is completed, the gas injection control valve 13 of the first gas supply unit 3A and the gas injection control valve 13 of the second gas supply unit 3B are controlled to be closed independently of each other and trapped in the resin. Gas holding pressure will be applied during the holding period. When the pressure-holding process ends, the two gas discharge control valves 15
Is released, and gas is released from the solidified resin. Note that each gas discharge control valve 15 is closed after completion of degassing.

When it is confirmed that the gas injection control valves 13 are closed, the first and second gas supply units 3
Each gas tank introduction control valve 12 of A and 3B is opened, and each gas tank 1 is depressurized as a result of injecting a predetermined amount of gas.
The high-pressure gas supplied from each gas compression device 5 is introduced into 0, and the two gas tanks 10 store the gas of the gas pressure value set correspondingly again.

By repeating the above-described operation, the gas of the first gas supply unit 3A is independently injected from the gas introducing unit 14A, and the gas of the second gas supply unit 3B is independently injected from the gas introducing unit 14B. A continuous molding operation of assist injection molding will be performed.

Thus, the first gas supply unit 3A
Gas of the second gas supply unit 3B and the gas of the second gas supply unit 3B are independently injected from the gas introduction unit 14A, and gases having different gas pressure values,
It is possible to inject different amounts of gas from different parts at different injection timings.

Therefore, when forming molded articles having different shapes in one die 2a, it is possible to perform gas injection at a gas pressure, a gas amount, and an injection timing suitable for each molded article, Each molded product can be molded under optimum gas-assisted injection molding conditions.

Further, in the case of a composite molded article using different resin materials, the optimum gas pressure value, the gas amount, and the optimum gas pressure value are obtained according to the shape of each resin material and each resin material portion.
Gas can be injected at the injection timing. For example, in the case of a composite molded product of ABS resin and PP resin, ABS resin requires a gas pressure of 150 kgf / cm ² or more, and PP resin has a pressure of 40 to 80 kgf / cm ^2.
A moderate gas pressure is desirable, but this condition can easily be met.

Furthermore, even when the resin has a fast solidification due to a thin portion in the middle of the molded product, the gas can be injected into the resin from two locations at slightly different timings as necessary. Quickly and at the required timing in the required area
It becomes possible to inject accurately.

In the above description of the operation, the gas injection control valve 13 is closed immediately after the gas injection is completed. However, after the pressure holding process is completed, the gas tank introduction control valve 12 is closed.
Is opened to reduce the pressure on the gas compression device 5 side to return the gas into the boost cylinder device 8, and thereafter, the gas injection control valve 1
3 may be closed and then the gas discharge control valve 15 may be opened to perform degassing. In this case, the amount of gas released into the atmosphere can be reduced.

In addition, the gas supply system of the present embodiment, when the normal gas assist injection molding conditions,
It goes without saying that only one of the first gas supply unit 3A and the second gas supply unit 3B can be used and the other can be stopped. In addition, under the normal gas-assisted injection molding conditions, even if one of the gas supply units fails, the production can be continued without any trouble.

[0040]

As described above, according to the present invention, it is possible to provide a gas supply system capable of coping with gas-assisted injection molding of a molded product having a high hollow ratio. In addition, it is possible to inject gas from two different locations, inject gas at two different gas pressures, inject gas at two different times, or inject two different amounts of gas. System can be provided.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of a gas supply system attached to an injection molding machine that performs gas-assisted injection molding according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of essential parts showing the configuration of a boost cylinder device of the gas compression device in FIG.

[Explanation of symbols]

1 Injection system mechanism 1a nozzle Type 2 opening / closing system mechanism 2a mold 3A First gas supply unit 3B Second gas supply unit 4 Nitrogen gas generator 5 Gas compressor 6 Check valve 6 7 Servo motor 8 Booster cylinder device 9 Servo amplifier 10 small capacity gas tank 11 Gas pressure detection sensor 12 Gas tank introduction control valve 13 Gas injection control valve 14A, 14B gas introduction section 15 Gas emission control valve 16 Unit connection pipe 17 Unit connection control valve

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) B29C 45/00-45/84

Claims (6)

(57) [Claims] 1. A gas supply system attached to an injection molding machine for injecting a molten resin into a cavity of a mold and performing a gas-assisted injection molding for injecting a high-pressure gas into the resin in the cavity. Generator, gas compression device for controlling pressure (compression) of gas supplied from the gas generation device, small-capacity gas tank for storing high-pressure gas supplied from the gas compression device, the gas tank and the gas compression device A tank introduction control valve provided in a pipeline between the gas tank and a gas injection control valve provided in a pipeline between the gas tank and a gas introduction part of the injection molding machine, Two units are attached to one injection molding machine, and in each of the gas supply units, the gas tank and the front
The line between the gas injection control valve and the
Gas supply system for an injection molding machine, characterized in that the connection. 2. The gas supply for an injection molding machine according to claim 1, wherein the two gas supply units are configured to supply gas to the different gas introduction parts of the injection molding machine, respectively. system. 3. The gas supply system for an injection molding machine according to claim 1, wherein the two gas supply units are configured to respectively supply gases having different pressure values to the injection molding machine. 4. The gas supply unit according to claim 1, wherein the two gas supply units have different timings.
A gas supply system for an injection molding machine, wherein each gas is supplied to the injection molding machine. 5. The gas supply system for an injection molding machine according to claim 1, wherein the two gas supply units are configured to supply gases having different gas amounts to the injection molding machine, respectively. 6. The injection molding machine according to claim 1, wherein the gases of the two gas supply units are added and supplied to one of the gas introduction parts of the injection molding machine. Gas supply system.