JPH07323436A - Method, die and device for gas charging injection molding - Google Patents

Abstract

PURPOSE:To provide gas charging injection molding method, die and device wherein, even if the filling amount of molten resin varies with each shot of injection molding, a satisfactory molding can be stably effected. CONSTITUTION:A die 20 is provided with a main cavity 22, a cylindrical auxiliary cavity 23 in communication with the main cavity and a piston-like movable die part 40 movable back and forth in the auxiliary cavity 23 to change the content volume of the auxiliary cavity 23. Before a molten resin 30 enters the auxiliary cavity 23, the pressing action is directed by a gas cylinder device 41 in the direction of decreasing the volume of the auxiliary cavity 23 and, by attaining a balance of the gas pressure for moving the molten resin 30 forward and the pressing force of the movable die part 40, the volume of the auxiliary cavity 23 is automatically regulated, so that a gas channel 31 in the molten resin 30 accurately becomes a predetermined volume.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas injection injection molding method and a mold thereof, and can be used for molding interior and exterior products such as automobile bumpers and dashboards, or molded products such as casings of home electric appliances.

[0002]

2. Description of the Related Art Conventionally, a gas injection injection molding method has been used as an injection molding method by which a lightweight and highly rigid molded product can be obtained. In this method, after injection of a molten resin into the main cavity in the mold, an inert gas such as pressurized nitrogen gas is injected into the cavity for injection molding. A gas flow path (hereinafter referred to as “gas channel”) is formed in the filled molten resin by the gas pressure, and the gas in the gas channel presses the molten resin toward the molding surface of the mold, Since the excess molten resin is discharged into a small space provided outside the main cavity (hereinafter referred to as "auxiliary cavity"), a uniform thin hollow molded product can be molded.

[0003]

However, the filling amount of the molten resin filled in the mold from the injection molding device is not always constant, and may vary from shot to shot. If the filling amount fluctuates significantly due to variations,
There is a problem that the following problems occur. That is, when the amount of the molten resin filled is too small, the amount of the molten resin filled in the auxiliary cavity is insufficient even if all the molten resin is filled, so that a gas channel is formed up to the inside of the auxiliary cavity. Punctured,
Since the pressure of the gas is not sufficiently transmitted, the volume of the molten resin in which the gas channel is formed is greatly reduced. As a result, defects such as sink marks and deformation occur on the surface of the molded product. On the other hand, when the filling amount of the molten resin is too large, the auxiliary cavity is filled with the molten resin before the gas channel reaches the predetermined position of the molten resin.
Gas channels are no longer formed, and solid thick-walled parts are formed in the portions where molten resin gas-channels are to be formed.As a result, the molded product is formed on the surface of the thick-walled part where gas does not flow. Problems such as sink marks occur.

An object of the present invention is to provide a gas injection injection molding method and a mold and apparatus for the same, which can stably perform good molding even if the filling amount of the molten resin to be filled varies in each shot of injection molding. To do.

[0005]

According to the gas injection injection molding method of the present invention, after starting the filling of the molten resin into the main cavity of the mold, a pressurized gas is injected into the main cavity to form the molten resin. A gas injection injection molding method in which injection molding is performed while forming a gas channel that is a passage for a pressurized gas, in which a cylindrical auxiliary cavity communicating with the main cavity and an interior of the auxiliary cavity are advanced and retracted. A piston-shaped movable mold part for changing the inner volume of the auxiliary cavity is provided in the mold, and a predetermined volume of the auxiliary cavity is reduced before the molten resin enters the auxiliary cavity. A pressing force is applied to the movable mold part in advance, and the movable resin part is moved backward by the molten resin against the pressing force.

The injection mold of the present invention comprises a pressing means for pressing the movable mold part in a direction in which the volume of the auxiliary cavity decreases with respect to the mold used in the gas injection injection molding method. Is provided.

The injection molding apparatus of the present invention is an apparatus used in the above-mentioned gas injection injection molding method, and includes a drive source for supplying a driving force to the pressing means in the gas injection injection mold. It is characterized by being configured.

In the above, it is desirable to employ a gas cylinder device as the pressing means. If this gas cylinder device is connected to the gas supply means by a pipe or the like, this gas supply device also serves as a drive source for the pressing means. It will be. At this time, it is preferable that the gas cylinder device is connected to the gas supply device through the pressure adjusting means.

[0009]

According to the present invention, after the molten resin is filled in the main cavity of the mold, pressurized gas is injected into the cavity and the molten resin filled in the main cavity of the mold is filled in the injection means. The pressure expands the entire main cavity and the injected pressurized gas forms a gas channel inside the molten resin. Then, the molten resin that has reached the auxiliary cavity enters the inside of the auxiliary cavity mainly by the pressure of the gas injected into the molten resin, and retreats the movable mold portion against the pressing force of the pressing means. As a result, excess molten resin is extruded into the auxiliary cavity, and a hollow molded product having a predetermined volume and uniform resin thickness is molded.
In the above, since the amount of gas injected into the mold is set to a predetermined amount in advance, the pressure of the gas that causes the molten resin to enter the auxiliary cavity becomes smaller as the gas channel in the molten resin expands. . Therefore, if the pressing force of the pressing means is set according to the pressure of the gas inside the gas channel when expanded to a predetermined volume, the gas channel in the molten resin will have a predetermined volume during gas injection molding. When the pressure reaches, the pressure of the gas and the pressing force of the pressing means are almost balanced (preferably completely balanced), and the molten resin that has entered the auxiliary cavity cannot move any further. By balancing the pressure of this gas and the pressing force of the pressing means, the volume of the auxiliary cavity is automatically adjusted to a volume according to the filling amount of the molten resin, and melts for each shot of injection molding. Even if the filling amount of the resin changes, only the amount of molten resin required for the molded product will stay in the main cavity, while the excess molten resin will be reliably pushed into the auxiliary cavity, and Therefore, the above-mentioned object is achieved. In this case, it is preferable that the pressure of the gas and the pressing force of the pressing unit are balanced, but if the condition that the molten resin flows into the auxiliary cavity against the pressing force of the pressing unit can be set, the gas injection of the present invention can be performed. In injection molding, it is not always necessary that the pressure of the gas and the pressing force are balanced.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an injection molding machine 1 according to the first embodiment of the present invention. The injection molding machine 1 is a gas injection injection molding device, and has an injection device 10 as an injection means for filling a synthetic resin and a mold 20 which is a mold for molding.
The injection device 10 is for kneading the molten resin 30 in the cylindrical barrel 11 with a screw (not shown) and injecting it into the mold 20. A nozzle 12 is provided at the tip of the barrel 11. The nozzle 12 is connected to the filling port 21 of the mold 20, and the molten resin 30 and the gas are sent into the mold 20 through the nozzle 12. A blow-in pipe 13 for injecting a pressurized gas is inserted inside the nozzle 12. The blow-in pipe 13 uses an inert gas such as nitrogen gas supplied from a gas unit 14 which is a gas supply means to melt the molten resin 30 in the mold 20.
It is something to inject inside. The gas from the blowing pipe 13 forms a gas channel 31 inside the molten resin 30.

The mold 20 has a main cavity 22 for molding a molten resin 30 filled therein and an auxiliary cavity 23 in communication therewith. The main cavity 22 is a space having a thin plate portion 24 having a small depth and a gas channel guide portion 25 in which a part of the bottom surface of the thin plate portion 24 is recessed. Main cavity
Molten resin 30 filled inside 22 is filled from the filling port 21 at the left end in the drawing to the auxiliary cavity at the right end in the drawing.
It flows toward 23. The gas channel guide portion 25 is a space having a larger depth dimension than the thin plate portion 24 in order to promote the formation of the gas channel 31 inside the molten resin 30, and extends over the entire length of the main cavity 22 in the left-right direction in the drawing. Has been formed. By the gas channel guide portion 25, the gas channel 31 is formed inside the molten resin 30 over substantially the entire length of the main cavity 22 in the left-right direction in the drawing.

The auxiliary cavity 23 is a cylindrical space extending vertically in the drawing. The upper end portion of the auxiliary cavity 23 in the figure is connected to the main cavity 22 via the communication portion 26,
Inside the auxiliary cavity 23, a movable mold part 40 is provided so as to be movable back and forth. It is configured such that the inner volume of the auxiliary cavity 23 changes as the movable mold part 40 moves back and forth, that is, moves in the vertical direction in the drawing. The movable mold part 40 is
It is a piston-like member having a flat cross section corresponding to the auxiliary cavity 23. Below the movable mold part 40 in the figure, a gas cylinder device 41 is provided as a pressing means for pressing the movable mold part 40 in the direction in which the internal volume of the auxiliary cavity 23 decreases. The gas cylinder device 41 is moved forward by the pressure of an inert gas such as nitrogen gas supplied to the inside, and is retracted by a coil spring or the like provided inside when the pressure of the inert gas disappears. The inert gas is supplied by the gas unit 14, and the gas unit 14 also serves as a drive source for driving the gas cylinder device 41. In FIG. 1, the auxiliary cavity 23 has a cylindrical shape extending in the vertical direction, but it may have a cylindrical shape extending in the horizontal direction.

The gas injection pipe 13 and the gas cylinder device 41 of the injection device 10 are connected to the gas unit 14 via a gas supply circuit 50 which is a valve unit having a plurality of types of valves. The gas supply circuit 50 includes a main pipe 51 that connects the gas unit 14 and the gas supply circuit 50 to each other.
And branch pipes 52 to 55 branched from the main pipe 51. The main pipe 51 sends the high pressure gas supplied from the gas unit 14 to the gas supply circuit 50. A pressure adjusting valve 56 is provided in the middle of the main pipe 51. By the pressure adjusting valve 56, the pressure of the gas supplied to the gas supply circuit 50 is adjusted to a predetermined first pressure value P ₁ even if the flow rate of the gas changes. The branch pipe 52 is a gas injection pipe of the gas supply circuit 50 and the injection device 10.
It is a pipe that connects with 13. The high pressure gas having the first pressure value P ₁ is sent to the gas blowing pipe 13 of the injection device 10 through the branch pipe 52.

The branch pipe 53 is connected to the gas supply circuit 50 and the gas cylinder.
It is a pipe that connects with the device 41, and a pressure adjusting means
A pressure reducing valve 57 is provided. The branch pipe 53
The pressure of the gas supplied to the cylinder device 41 is the pressure reducing valve 57.
The first pressure value P₁To the second pressure value P₂Decompressed to
It is like this. Drives this gas cylinder device 41
Second pressure value P of gas₂Is set as follows.
That is, the second pressure value P₂Is the first pressure value P₁The gas of
Gascha formed in the molten resin 30 by using a specified amount
Gas channel when the channel 31 reaches the specified volume
Gas pressure in 31 and second pressure value P₂Driven by the gas pressure of
Setting to balance with the pressing force of the gas cylinder device 41
Has been done. Specifically, the second pressure value P ₂Is the first pressure
Value P₁It is set slightly lower. Pressure reducing valve for branch pipe 53
An exhaust pipe 58 is connected between the 57 and the gas cylinder device 41.
Has been done. The exhaust pipe 58 is supplied to the gas cylinder device 41.
Gas is released to the atmosphere.
A top valve 59A is provided. The stop valve 59A is
Closed when driving the cylinder device 41, and after completion of molding
It is released when the pressing force of the gas cylinder device 41 is released.
It is a thing. By opening the stop valve 59A, the gas cylinder
The gas inside the device 41 is exhausted to the outside through the exhaust pipe 58.
It is supposed to be.

The branch pipe 54 is a pipe for collecting the high pressure gas in the gas channel 31 formed inside the molten resin 30 or opening it to the atmosphere, and a stop valve 59B is provided in the middle thereof. One end of the branch pipe 54 is connected to a gas tank or the like not shown, and the other end is connected to the gas blowing pipe 13 of the injection device 10 via the branch pipe 52. The stop valve 59B is
While being closed at the time of molding, it is opened after the completion of molding, and is opened until the high-pressure gas in the gas channel 31 drops to a predetermined pressure, and is closed when the gas drops to a predetermined pressure. The stop valve 59B allows the high-pressure gas in the gas channel 31 to be collected in the tank or the like or opened to the atmosphere while maintaining a predetermined pressure.

The branch pipe 55 is a pipe for gradually exhausting a relatively low pressure gas in the gas channel 31 formed inside the molten resin 30, and a stop valve 59C is provided in the middle thereof. One end of the branch pipe 55 is open to the atmosphere, and the other end is connected to the gas blowing pipe 13 of the injection device 10 via the branch pipe 52. This gradual depressurization is to prevent puncture. The stop valve 59C is closed at the time of molding, and after the molding is completed, the high pressure gas in the gas channel 31 is collected and the pressure is reduced, and then the stop valve 59C is opened. The stop valve 59C exhausts the gas in the gas channel 31 to the outside to bring the inside of the gas channel 31 to the atmospheric pressure. In addition, in FIG. 1, each valve of the gas supply circuit 50 is
Although shown with a symbol indicating a manual valve, these valves also include a solenoid valve, a pressure regulating valve, and the like.

The operation of this embodiment will be described below. In performing the gas injection molding, a second pressure value P ₂ that gives a pressing force to the gas cylinder device 41 that balances the gas pressure in the gas channel 31 completed by previously injecting the gas having the first pressure value P ₁ is obtained. The pressure reducing valve 57 is adjusted so that the secondary pressure becomes the second pressure value P ₂ . And
After starting the filling of the molten resin 30 into the main cavity 22, the gas is supplied from the gas unit 14 for a predetermined time.
As a result, a gas having a predetermined pressure is injected into the molten resin 30 filled in the main cavity 22, and a pressing force is generated in the gas cylinder device 41. This gas cylinder device
The pressing force of 41 causes the movable mold part 40 to move to the auxiliary cavity 23.
It is in a state of being pressed in the direction of decreasing the volume of. After that, the molten resin 30 reaching the auxiliary cavity 23 advances mainly due to the pressure of the gas in the gas channel 31, and enters the inside of the auxiliary cavity 23. The pressure of the gas that advances the molten resin 30 gradually decreases from the first pressure value P ₁ as the gas channel 31 expands, and as shown in FIG. 2, when the gas channel 31 is not fully expanded,
Since it is sufficiently larger than the pressing force of the gas cylinder device 41, the molten resin 30 moves forward against the pressing force of the gas cylinder device 41 while retracting the movable mold part 40.

On the other hand, the pressing force of the gas cylinder device 41 is set so as to be balanced with the pressure of the gas when the gas channel 31 reaches a predetermined volume, and therefore, as shown in FIG. When the gas channel 31 therein reaches a predetermined volume, the pressure of the gas and the pressing force of the gas cylinder device 41 are balanced, and the molten resin 30 that has entered the auxiliary cavity 23
Cannot move forward against the pressing force of the gas cylinder device 41 any more. Thereby, even if the filling amount of the molten resin 30 filled in the mold 20 is changed, the volume of the auxiliary cavity 23 is automatically adjusted according to the filling amount of the molten resin 30, and the gas in the molten resin 30 is adjusted. The channel 31 does not become smaller or larger than the predetermined volume, only the amount of the molten resin 30 required for the molded product remains in the main cavity 22, and the excess molten resin 30 is surely kept in the auxiliary cavity. It will be stored in 23.

According to this embodiment as described above, the following effects can be obtained. That is, the movable mold part 40 is provided inside the auxiliary cavity 23 so as to be movable back and forth, and
40 is pressed with a predetermined pressing force by the gas cylinder device 41,
Since the molten resin 30 that has entered under the pressure of the gas in the gas channel 31 causes the movable mold part 40 to retreat against the pressing force of the gas cylinder device 41, the volume of the auxiliary cavity 23 is equal to that of the molten resin 30. It will be automatically adjusted according to the filling amount, even if the filling amount of the molten resin 30 changes
It is possible to reliably form the gas channel 31 having a predetermined volume in the inside 30.

For this reason, since the filling amount of the molten resin 30 varies from shot to shot in the gas injection molding, if the filling amount of the molten resin 30 is small, the auxiliary cavity 23
Volume of the molten resin enters the auxiliary cavity 23
Even if the amount of 30 is small, gas does not enter the auxiliary cavity 23, and it is possible to prevent the gas channel 31 from expanding to the auxiliary cavity 23 and puncturing, so that problems such as sink marks and deformation may occur. Can be prevented. On the other hand, when the filling amount of the molten resin 30 is too large, the volume of the auxiliary cavity 23 is expanded, and any excess molten resin 30 that does not become a molded product is stored in the auxiliary cavity 23, and the gas channel 31 of a predetermined volume is surely secured. Therefore, it is possible to prevent the occurrence of defects such as sink marks and deformation in advance. Therefore, even if the filling amount of the molten resin 30 varies, good molding can be stably performed.

Further, since the pressing means for pressing the movable mold part 40 is the gas cylinder device 41 driven by the compressive fluid, the force for pressing the movable mold part 40 can be adjusted accurately and the compressive fluid can be adjusted. Since it is driven by the gas, the movable mold part 40 can be automatically retracted without controlling the gas cylinder device 41 if a force stronger than the pressing force generated by the gas cylinder device 41 is applied. Simple gas supply circuit
Even with 50, the operation in gas injection molding can be surely performed.

Further, since the gas unit 14 also serves as the drive source of the gas cylinder device 41 and the gas cylinder device 41 is connected to the gas unit 14 via the pressure reducing valve 57, the gas supplied to the gas cylinder device 41 is Pressure is molten resin 30
It is always lower than the pressure of the gas injected into the inside of the chamber, the gas pressure can be easily controlled, and the gas supply circuit 50 can be simplified.

Next, the effects of the present invention will be described based on concrete experimental examples. [Experimental Example] This experimental example is an experiment in which gas injection molding is repeated a plurality of times based on the present invention. As a mold, a mold for molding a substantially box-shaped molded product 60 shown in FIG. 4 is molded, and a mold having basically the same structure as the mold 20 shown in the above embodiment is adopted. This molded product 60 includes thin plate portions 61 to 64 having the same thickness on the back surface, the top surface, and both side surfaces in the figure.
Is provided, and the front surface and the bottom surface are opened. Thin plate
Each of 62 to 64 is provided with a thick portion 62A, 63A, 64A having a large thickness along the front edge. Thick part 62A, 63A, 64A
A series of gas channels 65 extending in a U shape inside the
Is provided. A spillover portion 66 is formed at the lower edge of the thick portions 63A and 64A in the figure by the molten resin that has entered the auxiliary cavity. Gas channel 65
Is formed by injecting gas from a gas injection port 67 provided on the front end surface of the thin plate portion 62. The injection port 67 is located at a position offset to the left side in the figure from the center of the end face of the thin plate portion 62, and
In the figure, the dimension L1 from the left end to the center of the inlet 67 is different from the dimension L2 from the right end to the center of the inlet 67. The respective dimensions of such a molded product 60 are set as follows. Thickness t: 3 mm Height H: 300 mm Width W: 400 mm Depth D: 200 mm Dimension L1: 150 mm Dimension L2: 250 mm [Comparative example] This comparative example is an experimental example performed for comparison with the experimental example. With the movable mold part 40 of the mold 20 fixed at the rearmost position so that the volume of the auxiliary cavity 23 does not change, the same molded product 60 as in the experimental example is gas injection-molded a plurality of times.

[Injection Conditions] In the above experimental examples and comparative examples, injection molding was performed under the same injection conditions as described below, using a 650-ton injection molding machine. Injection conditions Materials used: Polypropylene (Idemitsu Petrochemical Co., Ltd.)
Product name: Idemitsu POPOLY PRO J-750H, melt index MI = 10g / 10 minutes) Molding temperature: 220 ℃ Mold temperature: 30 ℃ Gas injection pressure: 20 MPa Resin filling time: 5.0 seconds Gas injection time: 2 0.0 second Here, the gas injection is performed 4 seconds after the resin filling is started, and the gas discharge is performed for 15 seconds after the pressure in the gas channel is maintained for 15 seconds after the completion of the gas injection. .

[Experimental Result] In the experimental example, the surface of the molded product 60 obtained in all shots has no defective portion such as “sink”, and even if there is a variation in the filling amount of the molten resin, it is ensured. I got a good product. In the comparative example, among the obtained plurality of molded products 60, due to the variation in the filling amount, the filled molten resin is insufficient, the gas channel 65 reaches the spillover portion 66, and the spillover portion 66 is punctured. was there. Due to this puncture, thick part 63A,
Since there is a sink mark near the bottom edge of 64A,
0 was a defective product. From this, it was found that a defective product was generated in the comparative example.

The present invention is not limited to the above-mentioned embodiments, but includes the following modifications and the like. That is, as the auxiliary cavity, a movable mold part that moves back and forth along a direction intersecting with the flow direction of the molten resin.
It is not limited to one having 40, but may be one having a movable mold part that advances and retreats along the flow direction of the molten resin.

Further, in the above embodiment, one gas unit 14 serves both as a gas supply means for supplying gas to the gas blowing pipe 13 of the injection device 10 and as a drive source for giving a driving force to the gas cylinder device 41. The gas supply means and the drive source may be provided separately. However, if they are also used, the effect that the gas supply circuit can be simplified can be obtained.

Further, the pressure adjusting means is not limited to the pressure reducing valve, but may be one provided with a pressure controller for operating the opening degree of the pressure adjusting valve based on the signal of the sensor for detecting the pressure of the molten resin in the auxiliary cavity. However, the effect of facilitating the gas pressure control can be obtained by using the above-described embodiment.

Further, in the above-mentioned embodiment, after the molten resin 30 is filled, the gas cylinder device 41 is driven to apply the pressing force to the movable mold portion 40. The pressing force may be applied to the portion, and the timing of applying the pressing force to the movable mold portion 40 may be any time before the molten resin enters the auxiliary cavity, such as gas injection or molten resin filling. It may be before or after the timing.

Further, a stop valve provided on the branch pipes 53 to 55
59A, 59B, and 59C are not limited to those that are manually operated, but may be automatic open / close valves with actuators installed.If automatic open / close valves are used, each automatic open / close valve may be sequence-controlled by the operation of the injection device, etc. Good.

The pressurized gas is not limited to nitrogen gas, but may be an inert gas such as argon, in short, as long as it has a high pressure and there is no danger of explosion.

[0032]

As described above, according to the present invention, even if the filling amount of the molten resin to be filled varies for each shot of injection molding, good molding can be stably performed.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing the overall configuration of an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing a state in a step of the embodiment.

3 is a view similar to FIG. 2 showing a state in one step after the step of FIG. 2.

FIG. 4 is a partially cutaway perspective view showing a molded product molded in an experimental example of the present invention.

[Explanation of symbols]

 1 injection molding machine 10 injection device as injection means 14 gas unit that also serves as gas supply means and drive source 20 mold 22 main cavity 23 auxiliary cavity 30 molten resin 37 pressure reducing valve as pressure adjusting means 40 movable mold section 41 pressing Gas cylinder device as means

Claims (5)

[Claims] 1. A method for injecting a pressurized gas into the main cavity after starting the filling of the molten resin into the main cavity of the mold to form a gas channel, which is a passage for the pressurized gas, inside the molten resin. A gas injection injection molding method for performing injection molding while a cylinder-shaped auxiliary cavity communicating with the main cavity, and a piston-shaped movable metal for advancing and retracting inside the auxiliary cavity to change the internal volume of the auxiliary cavity. A mold part is provided in the mold, and a predetermined pressing force in a direction in which the volume of the auxiliary cavity is reduced is applied to the movable mold part before the molten resin enters the auxiliary cavity. A gas injection injection molding method, characterized in that the movable mold part is moved backward with a molten resin against the pressing force. 2. After starting to fill the main cavity with the molten resin, a pressurized gas is injected into the main cavity to form a gas channel as a passage for the pressurized gas inside the molten resin. While being a gas injection injection mold for performing injection molding, a cylinder-shaped auxiliary cavity communicating with the main cavity and a piston-shaped auxiliary cavity for advancing and retracting the inside of the auxiliary cavity to make the internal volume of the auxiliary cavity variable. A gas injection injection molding mold comprising a movable mold part and a pressing means for pressing the movable mold part in a direction in which the volume of the auxiliary cavity decreases. 3. The gas injection injection mold according to claim 2, wherein the pressing means is a gas cylinder device. 4. A main cavity for molding a molten resin, a cylinder-shaped auxiliary cavity communicating with the main cavity, and a piston-shaped movable member for advancing and retracting the inside of the auxiliary cavity to change the inner volume of the auxiliary cavity. A gas injection injection molding apparatus for performing gas injection injection molding using a mold provided with a mold part and a pressing means for pressing the movable mold part in a direction of reducing the volume of the auxiliary cavity. An injection means for filling the molten resin in the main cavity of the mold, a gas supply means for supplying a pressurized gas injected into the molten resin filled in the cavity, and a pressing means for the movable mold part And a drive source that supplies a driving force to the gas injection injection molding apparatus. 5. The gas injection injection molding apparatus according to claim 4, wherein the pressing means is a gas cylinder apparatus, and the gas cylinder apparatus is connected to the gas supply means via pressure adjusting means, and the gas supply is performed. A gas injection injection molding apparatus, wherein the apparatus also serves as the drive source.