JP3124693B2 - Gas injection method and apparatus for 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 injection device of a molding machine for injecting a gas into a specific portion of a molded article to form a hollow shape, and more particularly to a gas injection device having a plurality of injection ports and corresponding to the injection port. The present invention relates to a gas injection device for forming a hollow portion in a portion and applying pressure to the resin from the hollow portion to obtain a uniform injection molded product.

[0002]

2. Description of the Related Art When molding by injecting a molten resin into a molding machine, an inert gas or the like is injected into a thick portion of a molded product and pressurized to form a hollow portion, thereby increasing the density of the resin. Prevents deformation caused by "sink" due to cooling after injection,
The amount of the resin material used can be reduced, and the strength can be improved. Conventionally, in order to hollow a predetermined part of a molded product,
After charging a pre-measured gas amount into a measuring cylinder, the pressure is increased by compression, and gas of the same pressure is simultaneously injected into a plurality of predetermined portions. However, the resin pressure in these plurality of predetermined portions has a considerable level, so that little gas is injected into the portion where the resin resistance is high, a large amount of gas is injected into the portion where the resistance is low, and a prescribed amount is injected into each predetermined portion. Is difficult to inject.

In order to solve this problem, Japanese Patent Laid-Open Publication No.
No. 781 is provided with a pressure gauge for detecting the resin pressure for each predetermined portion, and a control valve for controlling the gas supply. Based on the detected value of the pressure gauge, the control valve is controlled to inject gas. A technique for injecting a predetermined amount of gas into a predetermined portion is disclosed. As a control method of the control valve, a method of sequentially injecting gas from a predetermined portion with a high resin pressure and a method of simultaneously supplying gas to all predetermined portions and terminating the gas injection from a predetermined portion with a low resin pressure are disclosed. ing.

[0004]

The technique disclosed in the above publication uses a resin manometer to measure the resin pressure.
In order to measure the resin pressure, a precisely machined hole corresponding to the shape of the detection unit must be provided in order to provide a resin pressure detection unit in the mold. Further, since the measurement surface comes into contact with the resin, there is a problem that the shape of the measurement surface remains on the molded product. Further, the resin manometer has a problem that the structure is complicated and expensive because it comes into contact with a high-temperature resin.

The present invention has been made in view of the above-mentioned problems, and controls a control valve provided in a gas supply path to a predetermined hollow portion based on the position of a piston of a measuring cylinder, thereby controlling a predetermined value. The purpose is to inject a defined gas volume into the part.

[0006]

According to the first aspect of the present invention, a molten resin is injected into a mold space, and a gas is injected into the molten resin to form a hollow space. In the gas injection method of a molding machine in a processing method, a required amount of gas to be injected for each molded product is compressed and accumulated in a measuring cylinder by a reciprocating motion of a piston, and gas is supplied from the measuring cylinder to each predetermined portion of the molded product. Each control valve provided for each supply path is controlled based on a piston position of the measuring cylinder in accordance with preset conditions.

According to a second aspect of the present invention, there is provided a gas injection device of a molding machine in a processing method of injecting a molten resin into a mold space and injecting a gas into the molten resin to form a hollow space. A metering cylinder that compresses and accumulates the required amount of injected gas for each product by reciprocating the piston and discharges it.
A gas supply path for supplying gas from the measuring cylinder to a predetermined portion of the molded article; and a control valve provided in each of the gas supplying paths, based on a piston position of the measuring cylinder according to preset conditions. To control each of the control valves.

According to a third aspect of the present invention, a discharge pressure gauge for measuring a discharge pressure is provided on the discharge side of the measuring cylinder, and a difference between a preset set value and an output of the discharge pressure gauge is set to a predetermined value or less. And controlling at least one of the piston speed of the measuring cylinder and the control valve.

In the invention of claim 4, an injection gas pressure gauge for measuring an injection gas pressure is provided in each of the gas supply paths, and a difference between a preset value and an output of the injection gas pressure gauge is determined. At least one of the piston speed of the measuring cylinder and the control valve is controlled as follows.

[0010] In the invention of claim 5, a discharge pressure gauge for detecting a discharge pressure is provided on a discharge side of the measuring cylinder,
An injection gas pressure gauge for detecting an injection pressure is provided in each of the gas supply paths, and the operating state of each of the control valves, the measured value of the discharge pressure gauge and the measured value of the injection pressure gauge are displayed with respect to the piston position of the measuring cylinder. .

According to the present invention, the measuring cylinder moves the piston in the cylinder to the head side, guides the gas in the cylinder to the rod side, and compresses the gas according to the volume ratio between the head side and the rod side cylinder. The compression is performed by a first-stage compression process and a second-stage compression process in which the piston is moved to the rod side to compress the gas in the rod-side chamber. It is assumed that the gas amount calculated from the gas pressure in the inside and the piston position reaches a predetermined amount.

[0012]

According to the first and second aspects of the present invention, in the molding process, a test is performed before the product is formed, and when the hollow portion is formed, the conditions are established. A molding operation is performed. The test involves injecting more than the amount of gas to be injected into all specific parts of the molded article into the metering cylinder, determining the injection order for each specific part, and determining the piston position and its piston position so that each will have the required gas injection amount. The control data such as the opening / closing and the opening degree of the control valve provided in the gas supply path to the predetermined portion into which the gas is injected is established. After confirming that a predetermined gas volume is injected into each predetermined portion in this way, the molding of the product is performed by reproducing the test conditions. Therefore, by controlling each control valve based on the piston position of the measuring cylinder, it becomes possible to inject a predetermined amount of gas into each predetermined portion.

According to the third aspect of the present invention, the discharge pressure of the measuring cylinder is also measured in the test, and the difference between the discharge pressure established in the test and the discharge pressure in the product molding is determined to be equal to or less than a predetermined value at the time of product molding. By controlling at least one of the piston speed and the control valve, the gas injection accuracy is improved.

According to the fourth aspect of the present invention, similarly, in the test, the injection gas pressure in each gas supply path is also measured,
At the time of product molding, gas injection accuracy is improved by controlling at least one of the piston speed and the control valve so that the difference between the injection pressure established in the test and the injection pressure at the time of product molding becomes a predetermined value or less.

According to the fifth aspect of the present invention, the operation state of each control valve corresponding to the piston position of the measuring cylinder, the operating state such as the valve opening, and the measured values of the discharge pressure gauge and the injection gas pressure gauge are displayed on the monitor screen. Thereby, whether or not the product is molded in a correct state can be monitored.

In the sixth aspect of the present invention, the first-stage compression step is completed, and a certain percentage of the amount of gas moved toward the rod is supplied into the mold. This fixed ratio is determined in advance by a test, and if the moving amount is determined, the amount to be supplied to the mold can be determined. Since the amount of gas moved is determined by the gas pressure in the rod side cylinder and the piston position,
If the gas pressure and the piston position are determined, the gas supply amount is determined. Therefore, when a predetermined supply amount is obtained from the gas amount determined by the gas pressure in the rod-side cylinder and the piston position, this gas amount is set to a predetermined amount, and when the predetermined amount is reached, the first-stage compression process is completed. That is, when the first-stage compression step is completed, a predetermined supply rate is obtained by multiplying the gas amount in the rod-side cylinder by a certain ratio determined in the test.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a mold used in the present embodiment, and FIG. 2 shows a molded product formed by the mold. Mold 1
Comprises a mold 2 and a core mold 3 which are joined together to form a cavity 4 for molding a molded article 7. The mold mold 2 is provided with a resin injection nozzle 5, and the core mold 3 is provided with gas injection nozzles 6A, 6B, 6C, 6D for generating four hollow portions 8A, 8B, 8C, 8D. . The hatched area indicates the resin filling range, and the resin injection nozzle 5
The cross-sectional shape of the molded article 7 is shown except for the part of the injection path from.

FIG. 3 is a block diagram of the gas injection device of the present embodiment. This apparatus has four gas injection nozzles 6 in accordance with the mold 1 shown in FIG. 1, but this number can be changed according to the counterpart mold. The measuring cylinder 10 is a device that measures the amount of gas injected from the gas injection nozzle 6 and supplies the gas by pressurizing the same. The piston has a piston 11 and a piston rod 12 that moves the piston 11, and the piston rod 12 is a slider that is moved by a ball screw 13. 14 is connected. The ball screw 13 is composed of two
Driven by The servo motor 15 is provided with a pulse encoder 16 and outputs the rotation position and the number of rotations of the servo motor 15. With the measuring cylinder 10 bounded by the piston 11, the rod side is referred to as a rod side cylinder 17, and the opposite side is referred to as a head side cylinder 18. The measuring cylinder 10 is of a two-stage compression type and generates high-pressure gas. This apparatus is disclosed in detail in Japanese Patent Publication No. 6-4259 by the same applicant.
The compression step includes a first-stage compression step in which the gas injected into the head-side cylinder 18 is transferred to the rod-side cylinder 17 for compression, and a gas-injection nozzle 6A, 6B in which the gas in the rod-side cylinder 17 is compressed. , 6C, 6D
It consists of a step compression step. The gas is compressed in the first-stage compression step because the volume of the head-side cylinder 18 is larger than the volume of the rod-side cylinder 17, so that the gas moves from the larger volume to the smaller volume.

The head side cylinder 18 includes a nitrogen cylinder 19
And the pressure reducing valve 2 attached to the nitrogen cylinder 19
0, charge port 21 for taking in nitrogen gas, check valve 2
Nitrogen gas is injected through 2. A pressure sensor 23 is provided between the charge port 21 and the check valve 22 to measure the charge pressure of the nitrogen gas. A connection pipe 24 connecting the head side cylinder 18 and the rod side cylinder 17 is provided.
It has been prevented from flowing into. The rod side cylinder 17 is provided with a pressure sensor 26 for measuring the discharge pressure.

The connecting pipe 24 is connected to a gas injection pipe 30, and the gas injection pipe 30 is connected to the gas injection nozzles 6A, 6B, 6C, 6D.
Are branched into four 30A, 30B, 30C, and 30D. Note that 30A, 30B, 30C, 3
0D is displayed as 30A-D. Each gas injection pipe 30
In A to D, on-off valves 31A to D and opening degree adjustment valves 32A to
D, check valves 35A to 35D are provided in series, and the pressure sensor 3
4A to 4D, check valves 36A to 36D are mounted via branch pipes. The opening adjustment valves 32A to 32D adjust the valve opening with a small motor, and a pulse encoder 33A for detecting the opening is used.
To D are provided. The check valves 36A to 36D are connected to the exhaust pipe 37.
The exhaust pipe 37 is provided with an exhaust valve 38. The gas injection pipes 30A to 30D have measuring cylinders 10 attached thereto.
A pipe having a diameter sufficiently smaller than the diameter of the pipe is used.

By detecting the position of the slider 14 connected to the piston rod 12 of the measuring cylinder 10,
The position of the piston 11 can be detected. The position at which the piston 11 has moved fully on the rod side is the origin, and the position at which the piston 11 has moved fully on the head side cylinder 18 is the stroke end position. Origin detector 4 to detect these positions
1. A stroke end detector 42 is provided.

The measuring cylinder 10 and each valve are controlled by a control unit 40 having a microcomputer. The control unit 40 is provided with a display 43 for displaying the gas injection status. In addition, an instruction or the like from an operator is performed by the input device 44. Data from the pressure sensors 23, 26, and 34A to D are used as channel selection signals 45a from the control unit 40.
Is selected by the multiplexer 45 and input to the control unit 40 as a digital value by the A / D converter 46. The on-off valves 31A to 31D are instructed to open and close via a relay circuit 47. The opening degree of the opening degree adjustment valves 32A to 32D is adjusted via a relay circuit 48. The servo motor 15 is controlled via a servo controller 49 and a servo driver 50.

The operation of the apparatus having the above configuration will be described below.
First, a predetermined amount of nitrogen gas is supplied from the nitrogen cylinder 19 at a predetermined pressure determined by a test performed in advance, and the measuring cylinder 1
0 is charged to the head side cylinder 18. In charging, the pressure reducing valve 20 is set as low as possible to minimize the amount of gas left unused in the nitrogen cylinder 19, and the measuring cylinder 10 is used in a state close to a full stroke. However, at this time, the pressure of the pressure reducing valve 20 is set so that a predetermined pressure can be obtained with a margin by two-stage compression by reciprocation of the piston. The amount of gas injected into the cavity 4 shown in FIG.
Is determined by the amount of gas which is compressed in the first stage compression step and fed to the rod side cylinder 17, and the gas amount Q is determined based on the value of the pressure sensor 26 and the origin position of the piston 11. Calculated by the control unit 40 from the length Ls to the position of the piston 11 when the first-stage compression is completed. Therefore, when the charge pressure from the nitrogen cylinder 19 becomes lower than the set pressure, the first-stage compression completion position of the piston 11 increases toward the head-side cylinder 18 from the first-stage compression reference completion position E from the origin, and the predetermined injection gas Secure quantity.

The gas quantity Q to be charged is expressed by the following equation, assuming that the temperature is constant. Q = Pa × π (D ² −d ² ) × Ls / 4 (1) Pa: Absolute pressure in rod-side cylinder at completion of first stage compression (calculated from indicated pressure of pressure gauge 26) D: Cylinder inner diameter d: Piston rod outer diameter Ls: Distance from the origin position of the piston to the piston position at the time of completion of the first stage compression A temperature detecting end for measuring the cylinder temperature is attached to measure the cylinder temperature, and this temperature is measured. The volume of the first-stage compressed gas may be corrected according to Charles' law.

A check valve 22 provided in the immediate vicinity of the charge port 21 prevents gas from flowing backward in the first stage compression step, and the check valve 2
Reference numeral 5 indicates that gas flows from the head-side cylinder 18 to the rod-side cylinder 17 in the first-stage compression step, and prevents gas from flowing back to the head-side cylinder 18 in the second-stage compression step.

The piston operation of the measuring cylinder 10 is performed by a servo motor 15 through a ball screw 13. An origin detector 41 is provided with a position at which the piston 11 has moved to the full rod side as an origin. The slider 14 that moves by the rotation of the ball screw 13 moves the piston 11 in the direction of the origin via the piston rod 12, the origin detector 41 detects the detection end 14a provided on the slider 14, and then the pulse of the servomotor 15 The reproducibility is improved by stopping the servomotor 15 with the position at which the Z-phase signal (the signal that outputs one pulse per rotation) output from the encoder 16 as the origin position. Based on this origin position, nitrogen gas is first charged into the head-side cylinder 18, and then the piston 11 is moved toward the head-side cylinder 18 to perform first-stage compression. The first-stage compression is performed at a predetermined first-stage compression reference completion position E. As described above, the final completion is calculated from the value of Pa and the value of Ls representing the piston moving distance in the equation (1). The process is completed when the predetermined gas amount Q is secured in the rod-side cylinder 17. Pressure sensor 2
3 detects the charge gas pressure from the nitrogen cylinder 19.
When the set pressure exceeds the allowable range, the control unit 40 issues an alarm. In the second stage compression, the gas compressed and moved to the rod side cylinder 17 by the first stage compression is transferred to the piston 1.
1 is moved in the direction of the origin (the piston rod side), and the pressure is further increased. For the first-stage compression, the compression ratio of the output pressure of the first-stage compression to the suction gas when the first-stage compression is completed to the reference-completion position E is set to 3. From the second cycle, gas is charged into the head side cylinder 18 simultaneously with the second stage compression step.

The control unit 40 controls the servo motor 15 via the servo controller 49 and the servo driver 50. The servo controller 49 controls the servo motor 15 via the servo driver 50 according to the position data and speed data of the piston 11 from the control unit 40. The pulse encoder 16 provided on the servo motor 15 detects the rotation angle of the motor shaft of the servo motor 15,
A pulse train corresponding to the motor rotation angle is output to the servo controller 49 and the servo driver 50 based on the origin position. The servo controller 49 recognizes the motor rotation angle based on the input pulse train, and performs positioning of the piston 11 with respect to the origin position.

When the first stage compression is completed, the servo controller 49 outputs an operation completion signal Sc to the control unit 40, and the control unit 40 completes the movement of the piston 11 to the head side for a predetermined distance and the value of the pressure sensor 26 It is recognized that the predetermined gas amount Q has been charged to the rod-side cylinder 17.
Next, the second stage compression step is started. This start is performed by a start signal ST from the molding machine side. FIG. 1 shows a mold portion of the molding machine. The molding machine has a control section for controlling the entire molding machine. The control section outputs a start signal ST for requesting gas injection after resin injection.

Tests are performed prior to molding the product to establish the molding conditions. As the molding conditions, using the position of the piston 11 as a parameter, the opening / closing timing of the opening / closing valves 31A to 31D, the opening degrees of the opening degree adjusting valves 32A to 32D, the measured values of the pressure sensors 23, 26, and 34, the piston speed, and the like are used. The molding conditions for obtaining the best molded product in the test are established, and the correction conditions when the conditions deviate from these conditions are also established. The sequence of the gas injection operation is determined according to the molding conditions, programmed, and stored in the microcomputer of the control unit 40. This sequence includes steps from injection of nitrogen gas into the measuring cylinder 10 from the nitrogen cylinder 19 to injection of nitrogen gas into a predetermined portion and purging.

When the start signal ST is input from the molding machine, the control unit 40 sends control data to the servo controller 49 in accordance with a programmed sequence, controls the servo motor 15 via the servo driver 50, and performs the second stage compression. to go into. In this case, the position of the piston 11 is almost at the first stage compression reference completion position E as shown in FIG.
Start moving towards. The gas injection pattern differs depending on the shape of the molded product and the molding conditions. The control unit 40 outputs instruction data to the opening / closing valves 31A to 31D and the opening degree adjusting valves 32A to 32D in accordance with the sequence, and outputs the opening degree adjusting valves 32A to 32D.
, And the measurement values of the pressure sensors 26 and 34A to D are input, and a correction instruction is issued. Opening / closing valves 31A to 31D are relay circuits 4
7 is opened and closed at an arbitrary timing through the opening control valve 32.
A to D are arbitrary openings (0 to 100%) by small motor
, And this opening degree is determined by the pulse encoders 33A to 33A.
D is input to the control unit 40. This opening degree can be changed during gas injection depending on molding conditions. In this embodiment, a case is shown in which each of the gas injection nozzles 6A to 6D is fixed at a predetermined opening degree for each molded product.

The pressure sensors 34A to 34D are connected to the respective gas injection pipes 30.
A to D internal pressures are detected, and the pressure sensor 23 is connected to the nitrogen cylinder 1
The pressure sensor 26 detects the internal pressure of the rod-side cylinder 17. These pressure values are subjected to data sampling for each fixed movement position of the piston 11,
Store it in the corresponding memory. The multiplexer 45 includes the control unit 4
The analog signals of the pressure sensors 23, 26, 34A to D are sampled according to a channel selection signal 45a designated from 0, digitized by an A / D converter 46, input to the microcomputer of the control unit 40, and stored in the corresponding memory. It is stored and compared with the test data to check whether the data is within the allowable range. These data are displayed on the display 43 using the piston position as a parameter.

The opening adjustment valves 32A to 32D comprise a needle valve, a small motor for rotating the needle, and pulse encoders 33A to 33D for detecting the rotation angle of the needle.
The opening is 0 when the needle valve is fully closed, and 100% when fully open. The needle rotation angle from the fully closed state is detected by the pulse encoders 33A to 33D and calculated by counting using a corresponding counter (not shown) in the microcomputer. The fully closed state is recognized by a change in the motor drive current. The opening / closing instruction signals of the opening / closing valves 31A to 31D are also stored in the memory. On-off valve 3
The opening / closing timing of 1A to 1D and the opening of the opening adjustment valves 32A to 32D are also displayed on the display 43 using the piston position as a parameter. The check valves 35A to 35D prevent the back pressure from the gas injection nozzles 6A to 6D. The check valves 36A to 36D are check valves for connecting to the exhaust valve 38 without interference of the pipes to the gas injection nozzles 6A to 6D. The exhaust valve 38 is opened when the molding is completed, and releases the injected gas.

FIG. 4 shows a state display at the time of gas injection. In this example, the piston speed is controlled to a set value. The set value may be programmed so that the speed decreases gradually taking into account the temperature rise due to adiabatic compression of the gas. This figure shows display 4
3 is displayed as a monitor. This figure is a state diagram for the molded article shown in FIG. The horizontal axis indicates the stroke of the piston 11 and moves from the piston position shown in FIG. The start position is a position where the first-stage compression is completed, and is almost the position of the first-stage compression reference completion position E.
The vertical axis indicates the opening / closing timing of the opening / closing valves 31A to 31D, the portions indicating the valve opening degrees of the opening degree adjusting valves 32A to 32D, the internal pressure of the rod side cylinder 17 (measured value of the pressure sensor 26 shown by a solid line), and the gas injection pipe. 30A to 30D (measured values of pressure sensors 34A to 34D indicated by broken lines). Since the molded product 7 is symmetrical, the gas injection nozzles 6A and 6D and the gas injection nozzles 6B and 6C inject gas under the same conditions. Therefore, the opening / closing valves 31A and 31D and the opening / closing valves 31B and 31C have the same opening / closing timing, respectively, and the opening adjustment valves 32A and 32D and the opening adjustment valves 32B and 32C also have the same valve opening. The opening and closing timing of the on-off valves 31A to 31D is performed with reference to the origin position.

As shown in FIG. 1, the hollow portions 8A and 8D are thick portions and are located near the resin injection nozzle 5, so that the resin pressure is high and high pressure is injected, and the hollow portions 8B and 8C are relatively thin thick portions. , The resin pressure is relatively low, and the gas pressure to be injected is lower than that of 8A and 8D. Therefore, the on-off valves 31B and 31C are opened and closed at the low-pressure piston position, and the on-off valves 31A and 31D are opened and closed at the position near the high-pressure origin. Further, the opening degree adjusting valves 32A and 32D have large volumes of the hollow portions 8A and 8D so that the opening degree is large, and the opening degree adjusting valves 32B and 32C have small volumes of the hollow portions 8B and 8C so that the opening degree is small.

FIG. 5 shows an example in which an equal amount of gas is accurately injected when the hollow portions of the molded article are separated by the same shape. The display method is the same as that shown in FIG. Sensor 34
A to D) are shown. The valve opening / closing timing is performed based on the origin position. By opening and closing the on-off valves 31A to 31D at the piston positions confirmed in the test in advance, the pressures in the gas injection pipes 30A to 30D become equal. Further, the opening degrees of the respective opening degree adjustment valves 32A to 32D are all the same. Note that a program may be used in which the pressure of the rod-side cylinder 17 in the second stage compression (the pressure of the pressure sensor 26) is made constant by the servomotor 15.

During the gas injection shown in FIGS. 4 and 5, the detection values of the pressure sensor 26 indicating the internal pressure of the rod side cylinder 17 and the detection values of the pressure sensors 34A to 34D indicating the internal pressure of the gas injection pipes 30A to 30D are used during the test. When the data changes by a predetermined amount, for example, 10% or more, a correction instruction is output from the control unit 40 so as to be within a predetermined amount by increasing or decreasing the piston speed in a preset sequence. The correction can also be made by adjusting the opening / closing timing of the opening / closing valves 31A to 31D and the opening degree of the opening degree adjusting valves 32A to 32D. These corrections are also performed according to a sequence determined based on a test in advance.

In the above embodiment, nitrogen gas is used as the injection gas, but other inert gas, air or the like may be used. Further, in the present embodiment, a two-stage compressor which can obtain a high pressure with a simple structure is used, but one-stage compression may be performed by a normal cylinder.

[0038]

As is apparent from the above description, the present invention uses the piston position of the measuring cylinder as a parameter and reproduces the test results performed in advance, so that a predetermined amount of pressurized gas is applied to a predetermined portion. The hollow portion can be accurately formed by injection. In addition, since a resin pressure measuring device as conventionally used is not required, there is no need to design and process a mold for mounting the measuring device, and there is no possibility that the measurement surface is left behind on the product, Moreover, it becomes an inexpensive device.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an example of a mold used in an embodiment.

FIG. 2 is a perspective view of a molded product molded by the mold shown in FIG.

FIG. 3 is a block diagram showing a configuration of the present embodiment.

4 is a view showing a state of the molded article shown in FIG. 2 at the time of gas injection.

FIG. 5 is a view showing a state in which a hollow portion of a molded article has the same shape and accurately injects an equal amount of gas.

[Explanation of symbols]

 Reference Signs List 1 mold 4 cavity 5 resin injection nozzle 6 gas injection nozzle 8 hollow portion 10 measuring cylinder 11 piston 12 piston rod 13 ball screw 14 slider 15 servo motor 16, 33 pulse encoder 17 rod side cylinder 18 head side cylinder 19 nitrogen cylinder 22, 25 , 35, 36 Check valve 23, 26, 34 Pressure sensor 31 Open / close valve 32 Opening adjustment valve 38 Exhaust valve 40 Control unit 41 Origin detector 43 Display 49 Servo controller 50 Servo driver

Continued on the front page (72) Inventor Kenji Kono 5-6-2 Higashi-Hachiman, Hiratsuka-shi, Kanagawa Prefecture Mitsubishi Engineering Plastics Co., Ltd. Technology Center (72) Inventor Akimasa Kaneishi 5-6-1 Higashi-Yawata, Hiratsuka-shi, Kanagawa No. Mitsubishi Engineering Plastics Co., Ltd. Technical Center (56) References JP-A-6-23781 (JP, A) JP-A-50-24913 (JP, A) JP-A-5-261748 (JP, A) JP-A-1-128814 (JP, A) JP-A-8-132470 (JP, A) JP-A-5-177656 (JP, A) JP-A-8-99329 (JP, A) (58) Int.Cl. ⁷ , DB name) B29C 45/00-45/84 B29C 31/06

Claims (6)

(57) [Claims] In a gas injection method of a molding machine in a processing method of injecting a molten resin into a mold space and injecting a gas into the molten resin to form a hollow space, it is necessary to provide a molding machine with each molding product. The amount of gas to be injected is compressed and accumulated in the measuring cylinder by the reciprocating motion of the piston, and each control valve provided for each gas supply path for supplying gas from the measuring cylinder to each predetermined portion of the molded article is operated according to preset conditions. A gas injection method for a molding machine, wherein the control is performed based on a piston position of the measuring cylinder. 2. A gas injection device of a molding machine in a processing method in which a molten resin is injected into a mold space and a gas is injected into the molten resin to form a hollow space. Cylinder for compressing and accumulating the amount of gas to be injected by the reciprocating motion of the piston, discharging the gas, a gas supply path for supplying gas from the measurement cylinder to a predetermined portion of the molded product, and control valves provided in the gas supply path, respectively. Wherein the control valve is controlled based on a piston position of the measuring cylinder in accordance with a preset condition. 3. A discharge pressure gauge for measuring a discharge pressure is provided on a discharge side of the measurement cylinder, and a piston of the measurement cylinder is arranged so that a difference between a preset value and an output of the discharge pressure gauge is equal to or less than a predetermined value. The gas injection device for a molding machine according to claim 2, wherein at least one of a speed and the control valve is controlled. 4. An injection gas manometer for measuring an injection gas pressure in each of the gas supply passages, wherein the measuring cylinder is configured so that a difference between a preset set value and an output of the injection gas pressure gauge is equal to or less than a predetermined value. The gas injection device for a molding machine according to claim 2, wherein at least one of said piston speed and said control valve is controlled. 5. A discharge pressure gauge for detecting a discharge pressure is provided on a discharge side of the measuring cylinder, and an injection gas pressure gauge for detecting an injection pressure is provided in each of the gas supply paths. 3. The gas injection device for a molding machine according to claim 2, further comprising a monitor device for displaying an operation state of each of said control valves, and measurement values of said discharge pressure gauge and said injection gas pressure gauge. 6. A first-stage compression step in which the measuring cylinder moves a piston in the cylinder to a head side to guide gas in the cylinder to a rod side, and compresses the gas according to a volume ratio between the head side and the rod-side cylinder. The piston is moved to the rod side to compress the gas in the rod side chamber by a second stage compression step, and the first stage compression step is terminated by the gas pressure in the rod side cylinder and the piston. 3. The gas injection device for a molding machine according to claim 2, wherein a time when the gas amount calculated from the position reaches a predetermined amount.