JP2007290306A - Gas injection molding method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems of long molding cycles, problems of strength caused by thin parts which is apt to cure earlier than other parts, and problems of cleaning or the like of soil and clogging of detailed parts of a mold, and to eliminate limitation of thin molding of large molding caused by difficulty of controlling a gas injection part or the like. <P>SOLUTION: In a molding method of gas-injection molding, inside of the mold is vacuumed before resin is injected into the mold, thereafter the resin is injected into the mold, and a high pressure gas is injected into the resin after the resin is injected. A molding apparatus has the mold 3, a vacuum container 2, piping 11 for connecting the mold and the vacuum container, a vacuum valve 10 provided on the piping 11, a high-pressure container 5, piping 28 for connecting the mold 3 and the high-pressure container, and an injection valve 8 and an exhaust valve 9 provided on the piping 28. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a gas injection method that realizes thin-wall molding by injecting high-pressure gas into a resin injected into a mold, and a gas injection molding apparatus that rationally implements this gas injection method.

  The gas injection molding method, which is suitable for molding large and thick resin molded products, injects resin into the mold at a low injection pressure, and injects high-pressure nitrogen gas into the injected resin to increase the thickness. A hollow part is formed in the part, the thickness of the resin molded product is made uniform, and the change in the cooling rate of the resin is minimized to prevent sink marks, and it works from the inside of the resin without applying a high secondary pressure. This is a hollow molding method that is widely used as a molding method for large-sized and thick-walled resin molded products because internal strain can be eliminated and warping can be prevented by maintaining the gas pressure to be applied (for example, patent documents) 1).

JP 2002-036279 A

  In the gas injection molding method, since a hollow portion is formed inside the resin molded product, the injection amount of the resin to the mold is smaller than the mold volume by the amount corresponding to the volume of the hollow portion (short shot). For this reason, the flow rate of the resin inside the mold becomes slow, and the resin temperature at the tip portion is lowered, so that there arises a problem that welds appear at the joint of the resin. In order to solve this problem, molding is performed by raising the mold temperature. In this case, however, there arises a problem that the cooling time is extended and the molding cycle becomes longer.

  In addition, the thin part in the resin molded product is easy to cure faster than other parts, so if you increase the gas pressure injected into the resin, gas may enter the part where you do not want to put the gas. May cause strength problems. For this reason, it is necessary to control the gas injection portion, but this control is often not solved by adjusting the gas pressure alone, and it is necessary to set an optimal gas flow path when designing the mold. . As described above, there are many problems caused by the design of the mold. Further, cleaning must be performed at least every 10,000 shots due to contamination, clogging, etc. of the fine mold parts caused by carbonization of the volatile gas from the molten resin and the release agent.

  As mentioned above, when trying to perform large-sized thin molding by the gas injection molding method, the injection pressure is increased to increase the flow rate of the resin, but the thin-walled portion tends to harden quickly, but the internal gas pressure is increased. Since it is destroyed from the thin-walled portion when high pressure is applied, the gas pressure has a limit, and at the same time, if gas enters the thin portion, it causes strength problems, so it is difficult to control the gas injection part and thin-wall molding is performed. Naturally had its limits.

  The object of the present invention is to solve the problems in the gas injection molding method, that is, the point that the molding cycle becomes long and the strength problem due to the fact that the thin-walled part is easily cured faster than other parts. A method for solving various problems including the point that there is a limit to thin molding of large-scale molding due to difficulty in controlling the target gas injection part, etc., and contamination of mold fine parts, clogging cleaning, etc. To provide an apparatus.

  The gas injection molding method of the present invention that solves the above problems is a gas injection molding method using a gas injection molding machine, wherein the mold is evacuated before the resin is injected into the mold, and then the mold Resin is injected into the mold, and after injecting the resin, high pressure gas is injected into the resin.

  The gas injection molding apparatus according to the present invention is a gas injection molding apparatus using a gas injection molding machine, comprising a mold having a predetermined molding space, a vacuum storage container, the mold and the vacuum storage container. A pipe to be connected; a vacuum valve provided in the pipe for evacuating the mold; a high-pressure storage container for storing high-pressure gas; a pipe for connecting the mold and the high-pressure storage container; It has a high-pressure gas valve for injecting high-pressure gas after injecting resin into the mold and a discharge valve for discharging gas.

  In the gas injection molding apparatus, the mold is composed of a moving mold and a fixed mold, and the mold on the other side is close to the mold on either the moving mold or the fixed mold. It is preferable to provide a proximity sensor for detecting this and to drive the vacuum valve by a signal from the proximity sensor.

  Further, in any one of the above gas injection molding apparatuses, it has a piston reciprocating type gas compressor, generates a high pressure on the cylinder head side of the gas compressor and generates a vacuum on the piston rod side, and It is preferable to connect the high-pressure storage container to the cylinder head side via a pipe and connect the vacuum storage container to the piston rod side via a pipe.

  In any of the above gas injection molding apparatuses, a branch pipe having one end opened to the atmosphere is connected to a pipe connected to the piston rod side of the gas compressor, and the pipe connected to the vacuum storage container side of the branch pipe is connected to the pipe. A first valve is provided that closes when a pressure is applied to the pipe and opens when a vacuum is applied, and opens when the pressure is applied to the pipe on the branch pipe. A second valve that is sometimes closed is preferably provided.

  In any of the above gas injection molding apparatuses, a gas outlet check valve is provided on the cylinder head side and a high pressure side pressure sensor is provided on the high pressure storage container side of the pipe connected to the cylinder head side of the gas compressor. Further, by driving or stopping the gas compressor based on the pressure value set in the high pressure side pressure sensor in the high pressure storage container, the pressure of the high pressure storage container is adjusted according to the set value of the high pressure side pressure sensor. It is preferable to control.

  In any of the above gas injection molding apparatuses, a vacuum pump and a piston reciprocating type gas compressor are used as a vacuum generation source of the vacuum storage container, and the vacuum pump and the gas compressor are connected to the vacuum storage container via a pipe. Are preferably connected.

  Further, in any of the above gas injection molding apparatuses, when a vacuum generating side in a piston reciprocating gas compressor is connected to a mold by a pipe and a vacuum is generated in the pipe by the gas compressor. A valve to be opened is provided, and the vacuum storage container and the mold are connected by a pipe, and a vacuum switching valve is provided in the pipe. By selectively driving the vacuum switching valve, the vacuum generated by the gas compressor is It is preferable that the inside of the mold can be evacuated by being vacuumed by acting in the mold or by a vacuum generated by the gas compressor and a vacuum acting on the vacuum storage container.

  In the gas injection molding method according to the present invention, since the inside of the mold is evacuated before injecting the resin into the mold, the injected resin is sucked into the mold to increase the flow velocity while mediating air. Although the heat conduction is small and the radiation action is present, it is very small. Therefore, the injected resin cools down slowly, and the resin easily flows through the thin portion. In addition, there is no air resistance to the resin flow, and the problem that air is accumulated in a narrow portion and the resin flow is obstructed is solved.

  In particular, since the cooling rate of the resin is slow, it is not necessary to increase the mold temperature for preventing welds, and the mold can be actively cooled. For this reason, while the injected resin is present in the molding space, the cooling rate is slow, and it cools quickly after contacting the mold, shortening the molding cycle and reducing the thickness of large molded products. Thin wall molding that prevents warping and sink marks of large molded products, which is the greatest effect of the gas injection molding method, becomes possible. As described above, it is possible to shorten the molding cycle which is only inferior to the solid molding in a general injection molding method, and a great economic effect can be obtained.

  In addition, because the mold can be cooled, it is possible to prevent carbonization of the lubricant and mold release agent, prevent contamination and clogging of fine parts of the mold, and reduce the number of cleanings. Can do.

  In addition, since the gas injection molding method is a short shot, the injection pressure is lower than the general molding method, but the injection pressure when injecting the resin by making the inside of the mold vacuum is further reduced. This makes it possible to use an injection molding machine with a low injection pressure (a smaller machine than the injection molding machine currently molding) even when molding a large product, which is economically advantageous. .

  In the first gas injection molding apparatus according to the present invention, a vacuum storage container and a high-pressure storage container are connected to a mold through respective pipes, and a vacuum valve is connected to the vacuum-side pipe and a high-pressure side pipe is connected to the mold. Since a high pressure valve and a discharge valve are provided, the mold can be evacuated by operating the vacuum valve, and the resin injected into the mold by operating the high pressure valve. The high pressure gas injected into the resin can be discharged by operating the discharge valve. Therefore, the gas injection molding method can be implemented rationally.

  In the second gas injection molding apparatus, a mold is provided by driving a vacuum valve provided in a vacuum side pipe by a signal from a proximity sensor provided on either the moving side mold or the fixed side mold. A reasonable vacuum can be drawn from the inside.

  In the third gas injection molding apparatus, a high pressure and a vacuum are generated simultaneously by generating a high pressure on the cylinder head side and generating a vacuum on the piston rod side using a piston reciprocating gas compressor. Therefore, the equipment is not increased in size.

  In the fourth gas injection molding apparatus, the pipe connected to the piston rod side of the gas compressor is provided with a branch pipe, the branch pipe is provided with the first valve and the pipe is provided with the second valve. Is pressurized by the gas compressor, the second valve is closed and the first valve is opened, whereby the pressurized air can be exhausted to the atmosphere, and the inside of the pipe is evacuated. When the second valve is opened and the first valve is closed, the vacuum storage container connected to the pipe can be evacuated reliably, and pressurized air can act. Absent.

  As described above, in the fourth gas injection molding apparatus, generation of high pressure and generation of vacuum can be realized by a single gas compressor, and the cost for generating a vacuum while reducing the size of the apparatus. It is sufficient to add several valves to the piping, and an economical device can be realized.

  In the fifth gas injection molding apparatus, the high pressure side pressure sensor is set to the set value of the high pressure side pressure sensor by providing a gas outlet check valve and a high pressure side pressure sensor in the high pressure side pipe connected to the cylinder head side of the gas compressor. Accordingly, the pressure of the high-pressure reservoir can be controlled by driving or stopping the gas compressor. Therefore, an abnormally high pressure does not act on the high-pressure side pipe or the high-pressure storage container, and safety can be ensured. In order to achieve further safety, it is desirable to install a safety valve.

  In the sixth gas injection molding apparatus, a vacuum pump and a piston reciprocating gas compressor are used as a vacuum generation source of the vacuum storage container, and each is connected to the vacuum storage container, so that the situation inside the vacuum storage container The vacuum can be evacuated in an optimum state depending on

  In the seventh gas injection molding apparatus, the die is connected to the vacuum generating side of the piston reciprocating gas compressor through a pipe provided with a valve that opens when a vacuum is generated by the gas compressor. At the same time, since the vacuum storage container is connected via a pipe provided with a vacuum switching valve, the vacuum pressure and capacity acting in the mold can be adjusted by selectively driving the vacuum switching valve.

  That is, when the vacuum switching valve is opened, a vacuum generated by a gas compressor and a vacuum by a vacuum storage container are applied to the mold to evacuate a large amount of air from the mold in a short time, and the vacuum switching valve is closed. In this case, a vacuum generated by a gas compressor can be applied to the mold to suck the gas generated from the resin during molding.

  Hereinafter, the most preferred embodiments of a gas injection molding method and a gas injection molding apparatus according to the present invention will be described with reference to the drawings. The gas injection molding method of the present invention (hereinafter simply referred to as “molding method”) is to evacuate the interior of the mold prior to injecting the resin into the mold. This prevents air-mediated heat conduction and slows down the resin cooling rate, thereby ensuring fluidity inside the mold, and injecting high-pressure gas into the injected resin. By doing so, it is possible to reliably fill even a minute part.

  A gas injection molding apparatus (hereinafter simply referred to as “molding apparatus”) according to the present invention rationally implements the molding method.

  In the present invention, the mold is composed of a moving side mold and a fixed side mold, and when the moving side mold and the fixed side mold are closed, a space (cavity) for molding a desired molded product is formed inside. It is formed. The number of molds on the moving side mold is not limited, and one or a plurality of moving molds are used depending on the shape of the target molded product.

  The position when vacuum is applied from the mold (the vacuum is applied to the mold), that is, the vacuum side pipe mold that is connected to the vacuum storage container connected to the mold or the vacuum side of the gas compressor and the vacuum acts The connection position with respect to is not particularly limited, and it is preferable to connect to the most reasonable site from the shape of the cavity.

  For example, if the connection position of the vacuum side piping to the mold corresponds to a portion having a large cross-sectional area in the cavity, the inside of the mold can be evacuated in a relatively short time. When it is made to correspond to the corners, the injected resin can flow smoothly into the corners, and it is possible to obtain a good molded product by filling the resin up to the minute part of the molded product. It becomes.

  The apparatus configuration as a vacuum generation source for applying a vacuum to the mold is not particularly limited, and it is possible to generate a vacuum sufficient to carry out the molding method of the present invention, and corresponds to the molding cycle. Any one having a sufficient capacity can be used. Such vacuum sources include a rotary or reciprocating vacuum pump, a gas compressor that reciprocates a piston linearly, and the like.

  Also, the apparatus configuration as a source of high-pressure gas injected into the resin injected into the mold is not particularly limited, and it is possible to generate sufficient high-pressure gas to carry out the molding method of the present invention. And what is necessary is just to have sufficient capacity | capacitance corresponding to a shaping | molding cycle. As such a high pressure source, there is a rotary type or reciprocating type high pressure compressor, and in particular, a gas compressor of a type in which a piston is linearly reciprocated is preferable.

  The vacuum storage container and the high-pressure storage container of the present invention are pre-accumulated in order to apply a vacuum in a mold in a short time or inject a large amount of high-pressure gas into a resin injected into the mold in a short time. And a function for smoothing the pulsation in a vacuum pump or a gas compressor, and any apparatus capable of exhibiting such a function can be used. As such a container, there is a container formed by cutting, forging, or welding, and any of them can be preferably used.

  The capacities of the vacuum storage container and the high-pressure storage container are not limited, and are preferably set as appropriate according to the capacity of the molding space (cavity) formed in the mold. According to the knowledge of the present inventor, the object could be sufficiently achieved even with a capacity of about 100 liters.

  In the present invention, “vacuum” means a value in which the internal pressure of the cavity is around 1 kilopascal. The value of the internal pressure is a pressure that can be obtained by solving the problems of the present invention, obtained as a result of repeated experiments by the present inventors.

  Next, the configuration of the molding apparatus according to the first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a flowchart illustrating the configuration of the molding apparatus according to the first embodiment. FIG. 2 is a schematic diagram for explaining the relationship between the moving side mold and the fixed side mold. FIG. 3 is a view for explaining the configuration of the main part of the mold when evacuation is started. FIG. 4 is a diagram for explaining the configuration of the main part of the mold as the vacuuming proceeds.

  First, the configuration of the molding apparatus A according to the first embodiment will be described with reference to FIG. In the figure, a molding apparatus A includes a mold 3, a vacuum generating section for applying a vacuum to the mold 3, and a high pressure gas generating section for injecting a high pressure gas into the resin injected into the mold 3. And is configured. The mold 3 includes a moving mold 3a and a fixed mold 3b, and is attached to an injection machine (not shown).

  The vacuum generation unit includes a vacuum pump 1, a vacuum storage container 2, a pipe 11 connecting the vacuum storage container 2 and the mold 3, and a vacuum sensor 30 provided near the outlet of the vacuum storage container 2 in the pipe 11. And a vacuum valve 10 provided on the mold 3 side of the vacuum sensor 30.

  In the vacuum generator configured as described above, the vacuum generated by the vacuum pump 1 is accumulated in the vacuum storage container 2, and the pressure is monitored by the vacuum sensor 30. In accordance with the opening operation of the vacuum valve 10, the vacuum accumulated in the vacuum storage container 2 acts on the mold 3 through the pipe 11, and the vacuum can be applied to the inside of the mold 3. When the pressure in the vacuum storage container 2 exceeds the set value of the vacuum sensor 30, the vacuum pump 1 is stopped.

  The high-pressure gas generator includes a gas compressor 4, a high-pressure gas storage container 5 that stores high-pressure gas, a pipe 22 that connects the gas compressor 4 and the high-pressure storage container 5, and the gas compressor 4 in the pipe 22. An outlet check valve 6 provided on the outlet side and a pressure sensor 7 provided in the vicinity of the high pressure storage container 5, a pipe 28 connecting the high pressure storage container 5 and the mold 3, and the high pressure storage container 5 in the pipe 28 In order to monitor the pressure inside the injection valve 8 and the mold 3 provided in the vicinity, the pressure monitoring sensor 26 provided in the vicinity of the mold 3 and the injection valve 8 in the pipe 28 are provided on the mold 3 side. And a discharge valve 9.

  In the high pressure gas generating section configured as described above, the high pressure gas generated from the gas compressor 4 is accumulated in the high pressure storage container 5 through the pipe 22 and the outlet check valve 6, and the internal pressure of the high pressure storage container 5 is a pressure sensor. When the set value of 7 is exceeded, the gas compressor 4 stops. The high-pressure gas stored in the high-pressure storage container 5 passes through the pipe 28 to the mold 3 (inside the resin injected into the mold 3) by opening the injection valve 8 with the discharge valve 9 closed. Injected. The pressure of the high pressure gas injected into the mold 3 is monitored by the monitoring sensor 26. Then, by closing the injection valve 8 and then opening the discharge valve 9, the high-pressure gas in the mold 3 (inside the resin injected into the mold 3) can be released to the atmosphere.

  The opening timing of the vacuum valve 10 is set so as to be synchronized with the operation of closing the mold 3. That is, as shown in FIG. 2, the moving side mold 3a constituting the mold 3 is attached to the movable platen 31a of the injection molding machine, and the fixed side die 3b is attached to the fixed platen 31b. A proximity sensor 32 that detects that the opposing mold has come close to one of the moving side mold 3a and the fixed side mold 3b is disposed, and a detection member 36 that is detected by the proximity sensor 32 is provided on the other side. It has been. The vacuum valve 10 can be opened or closed according to a signal generated when the proximity sensor 32 detects the detection member 36.

  An airtight seal 33 is disposed over the entire circumference of the cavity on the surface of the fixed side mold 3b that contacts the moving side mold 3a, and the surface of the moving side mold 3a is in contact with the airtight seal 33 so that the mold 3 is configured such that the cavity formed in 3 can maintain hermeticity. Further, a passage 35 is formed in the fixed mold 3 b, and the vacuum side pipe 11 is connected to the passage 35.

  The cross-sectional shape and dimensions of the hermetic seal 33 are not particularly limited, and an O-ring used as a general hermetic seal material can be used. However, the O-ring is not necessarily required, and a sealing material having a polygonal cross section can be used. In particular, the hermetic seal 33 preferably has a sufficient allowance. And it is preferable to comprise so that the detection member 36 can be detected by the proximity sensor 32 substantially simultaneously with the time when the moving side mold 3a comes into contact with the airtight seal 33.

  By configuring the airtight seal 33 and the proximity sensor 32 as described above, when the moving side mold 3a comes into contact with the airtight seal 33, the moving side mold 3a is stopped by the signal of the proximity sensor 32 and the moving side mold 3a is stopped. With the cooperation of the mold 3a and the hermetic seal 33, it is possible to make the mold 3 have an airtight structure and to open the vacuum valve 10 so that a vacuum is applied to the cavity.

  As shown in FIG. 3, the passage 35 formed in the stationary mold 3b is formed in a groove shape in a portion communicating with the cavity, and the passage 34 is configured in cooperation with the surface of the moving mold 3a. The The cross-sectional area of the groove has a value that is smaller than the cross-sectional area of the passage 35, and the cross-sectional area of the passage 34 changes according to the distance from the surface of the moving-side mold 3a. That is, the passage 34 has a cross-sectional area that is sufficiently larger than the cross-sectional area of the passage 35 when the moving-side mold 3a approaches the fixed-side mold 3b and contacts the airtight seal 33, as shown in FIG. When the moving-side mold 3a is closed toward the fixed-side mold 3b, a passage 34a having a smaller cross-sectional area (a cross-sectional area where resin does not leak) than the passage 35 is formed.

  In the molding apparatus A configured as described above, the proximity sensor 32 is not detecting the detection member 36 when the moving side mold 3a is sufficiently separated from the fixed side mold 3b. The state in which the vacuum valve 10 is closed is maintained, and no vacuum acts on the pipe 11.

  When the moving-side mold 3a approaches the fixed-side mold 3b and the surface of the moving-side mold 3a comes into contact with the airtight seal 33 as shown in FIG. A signal is generated upon detection, and the vacuum valve 10 opens in accordance with this signal. When the vacuum valve 10 is opened, the vacuum in the vacuum storage container 2 acts on the mold 3 through the pipe 11, and the inside of the mold 3 (the space formed by the moving side mold 3a, the airtight seal 33, and the fixed side mold 3b). Vacuum inside). At this time, the passage 34 has a large cross-sectional area corresponding to the separation dimension of the moving side mold 3a from the fixed side mold 3b, and the inside of the mold 3 can be evacuated in a short time. .

  As the moving mold 3a approaches the fixed mold 3b, the cross-sectional area of the passage 34 decreases, and when the moving mold 3a is pressed against the fixed mold 3b and the mold 3 is closed, FIG. As shown in FIG. 4, a passage 34 a having a smaller cross-sectional area than that of the passage 35 is formed. The cross-sectional area of the passage 34a at this time is such that the resin does not enter when the high-pressure gas is injected into the resin injected into the cavity and the resin comes into close contact with the molding surface of the mold 3, and from the resin within the mold 3. The generated gas can be sucked continuously.

  A molding procedure by the molding apparatus A will be briefly described. First, the vacuum pump 1 and the gas compressor 4 are driven to sufficiently accumulate the vacuum storage container 2 and the high-pressure storage container 5 respectively. At this time, the pressure in the vacuum storage container 2 is maintained at a preset vacuum by the vacuum sensor 30, and similarly, the pressure in the high-pressure storage container 5 is maintained at a preset pressure by the pressure sensor 7. In particular, the pressure of the high-pressure storage container 5 is set and maintained at or above the pressure injected into the resin injected into the mold 3.

  When the moving side mold 3a is brought close to the fixed side mold 3b, a signal is generated from the proximity sensor 32 at the same time as the moving side mold 3a comes into contact with the hermetic seal 33 with this approach. Based on this, the vacuum valve 10 is opened and a vacuum is applied to the mold 3, and the air in the mold 3 is sucked through the passages 34 and 35 in a short time.

  The vacuum inside the mold 3 is monitored by a vacuum sensor 30, and after confirming that a preset vacuum is acting, a high force acts on the movable platen 31a of the molding machine to clamp the mold 3 Is completed. Next, a predetermined amount of resin is injected into the cavity of the mold 3.

  When the resin is injected into the cavity of the mold 3, the injection valve 8 is opened with the discharge valve 9 provided in the pipe 28 closed, and the high pressure gas accumulated in the high pressure storage container 5 is injected into the resin. To do. As a result, the injected resin is filled to every corner of the cavity of the mold 3 to realize good molding. In this state, the pressure is maintained for a predetermined time. During this time, the pressure of the high-pressure gas with respect to the resin is monitored and held by the pressure monitoring sensor 26.

  When the molded product that has been injected into the mold 3 and pressed against the molding surface by the injected high-pressure gas has cooled appropriately, the injection valve 8 is closed and the discharge valve 9 is opened. The high-pressure gas injected into a certain molded product is discharged to the atmosphere.

  Thereafter, the movable platen 31 a is operated, the moving side mold 3 a is separated from the fixed side mold 3 b, the mold 3 is opened, and the cooled molded product is taken out from the mold 3. As a result, a series of molding cycles is completed, and the next molding cycle is started.

  Next, the configuration of the molding apparatus B according to the second embodiment will be described with reference to FIG. In the drawing, the same reference numerals are given to the same parts and the parts having the same functions as those of the above-described embodiment, and the description thereof is omitted.

  The forming apparatus B shown in the figure is configured to generate a vacuum and a high-pressure gas at the same time by using the gas compressor 4 constituting the high-pressure generator without using the vacuum pump 1 in the vacuum generator.

  The first-stage cylinder head side of the gas compressor 4 in the gas compressor 4 in the molding apparatus B is constituted by a first-stage piston 15 and a first-stage piston rod 16, and a first-stage cylinder head chamber 13 and a first-stage piston rod. Similarly, the two-stage cylinder head side is divided into a two-stage cylinder head chamber 18 and a two-stage piston rod chamber 19 by a two-stage piston 21 and a two-stage piston rod 20.

  And the high voltage | pressure generating part is comprised by the cylinder head side of each stage. That is, the first-stage cylinder head chamber 13 is connected to the atmosphere or a nitrogen generator (not shown) through the inlet check valve 12, and is connected to the second-stage cylinder head chamber 18 through the check valve 17. The configuration from the two-stage cylinder head chamber 18 to the mold 3 is the same as that in the first embodiment.

  Therefore, the gas obtained by increasing the pressure of air or nitrogen gas in the first-stage cylinder head chamber 13 is introduced into the second-stage cylinder head chamber 18 through the check valve 17 and is increased again in pressure with the movement of the second-stage piston 21 to increase the pressure. The gas is supplied to the pipe 22 and accumulated in the high-pressure reservoir 5.

  Moreover, the vacuum generation part is comprised at the piston rod side of each step. That is, the first-stage piston rod chamber 14 is connected to a pipe 27 derived from a branch pipe 27c whose end is open to the atmosphere. The pipe 27 is closer to the vacuum storage container 2 than the branch pipe 27c. A check valve 23 is provided as a first valve that closes when the pipe 27 is pressurized and opens when a vacuum is applied, and opens when the pipe 27 is pressurized in the branch pipe 27c. A check valve 24 is provided as a second valve that closes when acted upon.

  The pipe 27 is connected to the vacuum storage container 2 via the vacuum sensor 30, and the pipe 11 connected to the mold 3 is connected between the check valve 23 and the vacuum storage container 2. 11 is provided with a vacuum valve 29 serving as a vacuum switching valve. This vacuum valve 29 has a function of applying or blocking a vacuum to the mold 3 in the same manner as the vacuum valve 10 of the molding apparatus A in the first embodiment described above.

  Similarly, a pipe 27a derived from a branch pipe 27d whose end is open to the atmosphere is connected to the two-stage piston rod chamber 19, and the branch pipe 27d has the same function as the check valve 24. A check valve 24a is provided, and a check valve 23a having the same function as the check valve 23 is provided in the pipe 27a. The pipe 27 a is connected between the check valve 23 of the pipe 27 and the vacuum storage container 2.

  The check valves 23, 23a, 24, and 24a provided in the pipes 27 and 27a and the branch pipes 27c and 27d have a function that can be automatically opened and closed according to the pressure difference between the inlet port and the outlet port. Therefore, when the first-stage piston rod chamber 14 and the second-stage piston rod chamber 19 are vacuumed or pressurized and act on the pipes 27, 27a, the check valves 23, 23a, 24, 24a are pressures in the pipes 27, 27a. Depending on the difference between the pressure acting on the port acting on and the pressure acting on the opposite port, they automatically open or close, respectively. Therefore, it is possible to cause only the vacuum generated in the piston rod chambers 14 and 19 to act on the vacuum storage container 2 and the mold 3 without requiring special control.

  When the amount of vacuum generated in the two-stage piston rod chamber 19 is small, it is not always necessary to provide a vacuum circuit in the piston rod chamber 19, and only the vacuum generated in the first-stage piston rod chamber 14 is used. You can do it.

  In the vacuum generation section, vacuum is alternately generated in the first-stage piston rod chamber 14 and the second-stage piston rod chamber 19 as the pistons 15 and 21 reciprocate. In other words, in the first-stage piston rod chamber 14 and the second-stage piston rod chamber 19, vacuum and pressurization are alternately performed as the pistons 15 and 21 move.

  For example, when a vacuum is generated in the first stage piston rod chamber 14, the second stage piston rod chamber 19 is pressurized. Accordingly, the check valves 23, 23a are provided in the pipes 27, 27a, and the check valves 24, 24a are provided in the branch pipes 27c, 27d, so that the check valves 23, 24 and the first-stage piston rod chamber 14 are The check valves 23, 23a, 24, 24a are opened or closed depending on the pressure of the pipe 27 between the check valve 23a, 24a and the pressure of the pipe 27a between the two-stage piston rod chamber 19. By closing, only the vacuum acts on the pipe 27 closer to the vacuum storage container 2 than the check valves 23 and 23a.

  Therefore, the vacuum generated in the first-stage piston rod chamber 14 can be accumulated through the pipe 27 or the vacuum generated in the second-stage piston rod chamber 19 can be accumulated in the vacuum storage container 2 through the pipes 27a and 27. In addition, by opening the vacuum valve 29, it is possible to simultaneously apply the vacuum accumulated in the vacuum reservoir 2 to the mold 3 and the vacuum generated in each piston rod chamber 14, 19.

  Generation of vacuum and generation of high-pressure gas by the gas compressor 4 will be described. When the first-stage piston 15 of the gas compressor 4 moves to the first-stage cylinder head chamber 13 side, the gas in the first-stage cylinder head chamber 13 is compressed to an intermediate pressure (pressure lower than the pressure set in the high-pressure reservoir 5). Is done. At the same time, since the pressure in the two-stage cylinder head chamber 18 decreases, the gas in the first-stage cylinder head chamber 13 passes through the check valve 17 and is supplied to the two-stage cylinder head chamber 18.

  In the above state, the first-stage piston rod chamber 14 is evacuated and the second-stage piston rod chamber 19 is pressurized. At this time, since the first stage piston rod chamber 14 is in a vacuum state, the check valve 24 provided in the branch pipe 27c is closed, and the vacuum in the first stage piston rod chamber 14 is lower than the vacuum on the vacuum storage container 2 side. Then, the check valve 23 opens. At the same time, since the two-stage piston rod chamber 19 is in a pressurized state, the check valve 23a is closed and the check valve 24a is opened.

  Therefore, the high-pressure gas generated in the first-stage cylinder head chamber 13 is supplied to the second-stage cylinder head chamber 18, and the vacuum generated in the first-stage piston rod chamber 14 acts on the vacuum storage container 2 through the check valve 23 and the pipe 27. The pressurized gas generated in the two-stage piston rod chamber 19 is discharged from the branch pipe 27d to the atmosphere through the check valve 24a.

  Next, when the second-stage piston 21 of the gas compressor 4 moves to the second-stage cylinder head chamber 18 side, the already pressurized gas in the second-stage cylinder head chamber 18 is further pressurized and has a target pressure. The high pressure gas is supplied from the pipe 22 to the high pressure storage container 5. At this time, the first-stage cylinder head chamber 13 has a negative pressure, and air or nitrogen gas is sucked through the check valve 12.

  In this state, the first-stage piston rod chamber 14 is pressurized, the second-stage piston rod chamber 19 is evacuated, and the first-stage piston rod chamber 14 is in a pressurized state. For this reason, in the piping 27 connected to the first stage piston rod chamber 14, the check valve 23 is closed and the check valve 24 is opened. At the same time, since the two-stage piston rod chamber 19 is in a vacuum state, the check valve 24a is closed and the check valve 23a is opened. Accordingly, the pressurized gas generated in the first stage piston rod chamber 14 passes through the check valve 24 and is discharged to the atmosphere from the branch pipe 27c, and the vacuum generated in the second stage piston rod chamber 19 passes through the check valve 23a and the pipe 27a. It acts on the vacuum reservoir 2.

  Therefore, by closing the vacuum valve 29, the vacuum generated with the operation of the gas compressor 4 is accumulated in the vacuum reservoir 2. Then, by opening the vacuum valve 29, it is possible to cause the vacuum accumulated in the vacuum storage container 2 to act on the mold 3 to evacuate a large amount of air from the mold 3. After clamping the mold, it is possible to maintain the vacuum inside the mold 3 by the vacuum generated by the operation of the gas compressor 4 and to suck the gas generated from the injected resin.

  In the molding apparatus B configured as described above, it is possible to simultaneously generate vacuum and high-pressure gas by operating one gas compressor 4. For this reason, the configuration of the molding apparatus B is simplified, and the molding apparatus B can be downsized. In particular, it is economically advantageous because a system for generating a vacuum is configured by adding a plurality of check valves and a few pipes.

  Next, the configuration of the molding apparatus C according to the third embodiment will be described with reference to FIG. The molding apparatus C according to the present embodiment is configured by replacing the check valves 23, 23a, 24, 24a provided in the pipes 27, 27a of the molding apparatus B described above with valves that can be electrically controlled. Therefore, the system other than the system of the pipes 27 and 27a is configured the same as the molding apparatus B.

  That is, the first-stage piston rod chamber 14 is connected to a pipe 27 derived from a branch pipe 27c whose end is open to the atmosphere. The pipe 27 is closer to the vacuum storage container 2 than the branch pipe 27c. A vacuum pulling valve 37 serving as a first valve that is closed when the pipe 27 is pressurized and opened when a vacuum is applied, and a negative pressure sensor 39 are provided, and the pipe 27 is pressurized to the branch pipe 27c. An evacuation valve 38 is provided as a second valve that opens when the valve is closed and closes when a vacuum is applied. The pipe 27 is connected to the vacuum storage container 2 via the vacuum sensor 30, and the pipe 11 connected to the mold 3 is connected between the vacuum valve 37 and the vacuum storage container 2. 11 is provided with a vacuum valve 29.

  Similarly, a pipe 27a derived from a branch pipe 27d whose end is open to the atmosphere is connected to the two-stage piston rod chamber 19, and the branch pipe 27d has the same function as the vacuum exhaust valve 38. A vacuum exhaust valve 38a is provided, and a vacuum pulling valve 37a having a function similar to that of the vacuum pulling valve 37 and a negative pressure sensor 39a are provided in the pipe 27a. The pipe 27 a is connected between the vacuum valve 37 of the pipe 27 and the vacuum storage container 2.

  The vacuum valves 37 and 37a and the vacuum exhaust valves 38 and 38a are respectively configured as electromagnetic valves that open and close in response to electrical signals. And it is comprised so that the negative pressure sensors 39 and 39a can open and close according to the signal generate | occur | produced when the negative pressure of piping 27 and 27a is detected and it becomes a preset negative pressure value.

  In the above configuration, the vacuum and pressure acting on the pipes 27 and 27a are detected by the negative pressure sensors 39 and 39a provided on the pipes 27 and 27a, and the detected pressure is compared with a preset value. Thus, a signal is generated, and by controlling the opening and closing of the vacuum valves 37 and 37a and the vacuum exhaust valves 38 and 38a according to the signals, only the vacuum is applied to the pipe 27 on the vacuum storage container 2 side. Is possible.

  That is, for example, when the first-stage piston rod chamber 14 becomes vacuum and the second-stage piston rod chamber 19 is pressurized, the negative pressure sensor 39 recognizes that the pipe 27 is in a vacuum state and generates a signal. In response to the signal, the vacuum valve 37 is opened and the vacuum exhaust valve 38 is closed. At the same time, the negative pressure sensor 39a recognizes that the pipe 27a is in a pressurized state, generates a signal, and closes the vacuum valve 37a and opens the vacuum exhaust valve 38a in response to this signal.

  Accordingly, the vacuum generated in the first-stage piston rod chamber 14 acts on the vacuum storage container 2 through the pipe 27, and the pressurized gas generated in the second-stage piston rod chamber 19 is discharged to the atmosphere from the vacuum exhaust valve 38a provided in the pipe 27a. Is done.

  As described above, even when the evacuation valves 37 and 37a and the evacuation valves 38 and 38a that open and close according to the electrical signals are provided in the pipes 27 and 27a and the branch pipes 27c and 27d, the pipes are provided by the negative pressure sensors 39 and 39a. It is generated in each piston rod chamber 14, 19 by detecting the negative pressure of 27, 27a and opening / closing in accordance with the generated signal, as in the case where the check valves 23, 23a, 24, 24a are provided. Only the vacuum thus applied can act on the vacuum storage container 2.

  Even with the molding apparatus C configured as described above, it is possible to simultaneously generate vacuum and high-pressure gas by operating one gas compressor 4. For this reason, the structure of the shaping | molding apparatus C becomes simple and it becomes possible to achieve size reduction.

  In the molding apparatus C configured as described above, the vacuum pump 1 may be connected to the vacuum storage container 2 in the same manner as the molding apparatus A. In this way, by providing two vacuum sources in the vacuum generating section, when vacuuming a large amount of air existing inside the mold 3, the vacuum generated by the vacuum pump and accumulated in the vacuum storage container 2 is generated. When the mold is clamped and the vacuum inside the mold 3 is maintained and the gas generated by the resin is sucked, the vacuum accompanying the operation of the gas compressor 4 can be applied.

  That is, at the moment when the moving-side mold 3a contacts the fixed-side mold 3b, the volume in the mold 3 is large, and it is required to evacuate a large amount of air in a short time. For this reason, it is preferable to apply the vacuum of the vacuum storage container 2 so that a large amount of vacuuming can be realized even if the vacuum pressure is somewhat low. Further, after the mold clamping of the mold 3 is completed, it is required that the vacuum pressure inside the mold 3 is maintained at a preset value. For this reason, it is preferable to apply a vacuum from the gas compressor 4 capable of generating a high vacuum pressure.

  In order to select and operate a vacuum source for the mold 3, it is preferable to provide a vacuum valve between the connection portion of the pipe 11 connected to the mold 3 in the pipe 27 and the vacuum storage container 2. . Then, the vacuum pump is driven to store the vacuum in the vacuum storage container 2, and at the same time, the gas compressor 4 is driven to generate a vacuum alternately from the piston rod chambers 14 and 19 to act on the pipe 27. By opening the vacuum valve 29 provided in the vicinity of the vacuum storage container 2 and the vacuum valve 29, the vacuum of the vacuum storage container 2 and the vacuum generated from the gas compressor can be applied to the mold 3 simultaneously. . Further, the vacuum generated in the gas compressor 4 can be applied to the mold 3 by closing the vacuum valve provided in the vicinity of the vacuum storage container 2.

  In the molding method of the present invention, it is possible to obtain a good product by sufficiently filling the resin up to the fine part, and it is particularly used for molding a resin molded product having a large thick part and a thin part. And effective. Further, the molding apparatus according to the present invention is advantageous because it can effectively implement the molding method of the present invention.

It is a flow sheet figure explaining the structure of the shaping | molding apparatus which concerns on 1st Example. It is a schematic diagram explaining the relationship between a movement side metal mold | die and a fixed side metal mold | die. It is a figure explaining the structure of the principal part of the metal mold | die at the time of starting evacuation. It is a figure explaining the structure of the metal mold | die of the principal part accompanying progress of evacuation. It is a flow sheet figure explaining the composition of the forming device concerning the 2nd example. It is a flow sheet figure explaining the composition of the forming device concerning the 3rd example.

Explanation of symbols

A, B, C Molding device 1 Vacuum pump 2 Vacuum storage container 3 Mold 3a Moving side mold 3b Fixed side mold 4 Gas compressor 5 High pressure storage container 6 Outlet check valve 7 Pressure sensor 8 Injection valve 9 Release valve 10 Vacuum valve 11 Piping 12 Inlet check valve 13 First stage cylinder head chamber 14 First stage piston rod chamber 15 First stage piston 16 First stage piston rod 17 Check valve 18 Two stage cylinder head chamber 19 Two stage piston rod chamber 20 Two stage piston Rod 21 Two-stage piston 22 Piping 23, 23a, 24, 24a
Check valve 26 Pressure monitoring sensor 27, 27a Piping 31a Movable platen 31b Fixed plate 32 Proximity sensor 33 Airtight seal 34, 34a, 35 Passage 36 Detection member 37, 37a Vacuum valve 38, 38a Vacuum exhaust valve 39, 39a Negative pressure sensor

Claims (8)

In the gas injection molding method by the gas injection molding machine, the inside of the mold is evacuated before injecting the resin into the mold, and then the resin is injected into the mold, and further after the resin is injected A gas injection molding method characterized by injecting high-pressure gas into the resin. A gas injection molding apparatus using a gas injection molding machine, wherein a mold having a predetermined molding space, a vacuum storage container, a pipe connecting the mold and the vacuum storage container, and a metal provided in the pipe A vacuum valve for evacuating the mold, a high-pressure storage container for storing high-pressure gas, a pipe connecting the mold and the high-pressure storage container, and a high-pressure gas provided in the pipe after injecting resin into the mold A gas injection molding apparatus comprising: a high-pressure gas valve for injecting gas and a discharge valve for discharging gas. A proximity sensor for detecting that the mold on the other side is close to the mold on one side of the movable mold or the fixed mold, the mold comprising a movable mold and a fixed mold; The gas injection molding apparatus according to claim 2, wherein the vacuum valve is driven by a signal from the proximity sensor. It has a piston reciprocating gas compressor, generates high pressure on the cylinder head side of the gas compressor, generates vacuum on the piston rod side, and connects a high pressure storage container to the cylinder head side via piping. The gas injection molding apparatus according to claim 2, wherein a vacuum storage container is connected to the piston rod side through a pipe. A branch pipe having one end opened to the atmosphere is connected to a pipe connected to the piston rod side of the gas compressor, and is closed when pressure is applied to the pipe on the vacuum storage container side than the branch pipe and There is provided a first valve that opens when a vacuum is applied, and a second valve that opens when the pipe is pressurized and closes when a vacuum is applied to the branch pipe. The gas injection molding apparatus according to any one of claims 2 to 4, wherein the gas injection molding apparatus is provided. The pipe connected to the cylinder head side of the gas compressor is provided with a check valve for gas outlet on the cylinder head side and a high pressure side pressure sensor on the high pressure storage container side, and further, the high pressure side pressure is applied to the high pressure storage container. 6. The pressure of the high-pressure storage container is controlled according to the set value of the high-pressure side pressure sensor by driving or stopping the gas compressor based on the pressure value set in the sensor. A gas injection molding apparatus according to any one of the above. 7. A vacuum pump and a piston reciprocating gas compressor are used as a vacuum generation source of the vacuum storage container, and a vacuum pump and a gas compressor are connected to the vacuum storage container through a pipe. A gas injection molding apparatus according to any one of the above. In a piston reciprocating type gas compressor, a vacuum generating side and a mold are connected by a pipe, and a valve that is opened when a vacuum is generated by the gas compressor is provided in the pipe, and a vacuum storage container and a mold are provided. The pipe is connected with a vacuum, and a vacuum switching valve is provided in the pipe, and the vacuum switching valve is selectively driven so that the vacuum generated by the gas compressor is applied to the mold to evacuate or compress the gas. 8. The gas injection molding apparatus according to claim 2, wherein the inside of the mold can be evacuated by a vacuum generated by a machine and a vacuum acting on a vacuum storage container.

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