JP3279448B2 - Injection molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention enables gas injection molding, which is a kind of hollow injection molding, in which molten resin is injected into a cavity of a mold and high-pressure gas is injected into the resin in the cavity. It relates to an injection molding machine.

[0002]

2. Description of the Related Art Gas injection molding in which a molten resin is injected into a cavity of a mold and an inert gas such as a high-pressure nitrogen gas is injected into the molten resin before the molten resin in the cavity is solidified, A holding pressure is applied to the resin from inside the resin,
Since the front side of the resin is pressed against the inner wall of the cavity,
Good products without sink marks and the like can be molded, and the weight of molded products (products) can be reduced.

Various proposals have been made for such gas injection molding. For example, Japanese Patent Application Laid-Open No. 63-13971.
6, Japanese Patent Application Laid-Open No. 1-128814,
JP-A-47171, JP-A-6-321431, and the like disclose techniques relating to gas injection molding.

In the gas injection molding according to the prior art, a high-pressure gas supply device including a pneumatic valve unit is provided near a machine (injection molding machine), and is formed into a pneumatic valve unit and a mold. A configuration was used in which a connection with a gas injection port was established by an air pipe.

[0005]

As described above, in the prior art, there is a strong concept that a high-pressure gas supply device including a pneumatic valve unit is an external device independent of a machine. As a result, the pneumatic valve unit including the switching control valve for press-in control for injecting gas into resin and the switching control valve for exhaust control for exhausting gas from resin is independent of the machine body. And was located near the machine.

For this reason, a pipe connecting the pneumatic valve unit and a gas inlet formed in a mold or the like becomes longer, and the responsiveness of the gas injection control becomes slow due to the length of the pipe.
There was a problem that gas injection control with good responsiveness could not be performed. Also, in the gas exhaust process of exhausting gas from the resin, a method of releasing the high-pressure gas from the pneumatic valve unit to the atmosphere is often adopted. Therefore, the gas formed in the pneumatic valve unit and the mold is often used. There is also a problem that all the high-pressure gas in a considerably long pipe connecting the inlet and the inlet is wasted, and the gas consumption increases.

[0007] The present invention has been made in view of the above points,
An object of the present invention is to increase the responsiveness of gas injection control in an injection molding machine capable of gas injection molding. Another object of the present invention is to reduce wasteful consumption of high-pressure gas as much as possible.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention enables gas injection molding by injecting a molten resin into a cavity of a mold and pressing a high-pressure gas into the resin in the cavity. in the injection molding machine, gas injection pieces
And a switching control valve for press-fit control for press-fitting a gas from a high-pressure gas supply source into the resin,
And a pneumatic valve unit including at least a switching control valve for exhaust control for exhausting gas from the resin,
It has a configuration in which it is arranged on a die plate for attaching a mold .

[0009]

Since the pneumatic valve unit is disposed near the gas injection point, the piping between the pneumatic valve unit and the gas injection point is shortened, so that the switching control valve is turned on / off and feedback controlled. Pressurization control of high-pressure gas can be performed with good responsiveness according to the conditions and the like, which contributes to further molding of good products. In addition, since the piping length between the pneumatic valve unit and the gas injection point is short, waste gas consumption is greatly reduced even if a method is used in which the high-pressure gas from the pneumatic valve unit is released to the atmosphere during the gas exhaust stroke. it can.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the illustrated embodiments. FIG. 1 is an explanatory view showing an outline of a high-pressure gas supply device of an injection molding machine according to one embodiment of the present invention. In the figure, 1 is an air intake, 2 is a filter, 3 is a mist separator, 4 and 5 are pressure reducing valves, 6 is a nitrogen gas generator (nitrogen gas generator), 7 is a flow meter, 8 is a throttle valve, 9,
10 is a check valve, 11 is a gas pressure raising mechanism, 12 is an electric servomotor, 13, 14, 15 are pressure gauges, 16 and 17 are switching control valves controlled by air, 18 and 19 are electromagnetic control valves, and 20 is A molding die 21 composed of a fixed die 20A and a movable die 20B is a cavity for forming a molding space.

In this embodiment, a gas injection port for injecting high-pressure nitrogen gas into the resin in the cavity 21 is provided in the molding die 20, and the vicinity of the gas injection port, that is, the molding is performed. A pneumatic valve unit 30 composed of switching control valves 16 and 17 and electromagnetic control valves 18 and 19 is provided on a die plate,
Is attached.

FIGS. 2 and 3 show the arrangement of the pneumatic valve unit 30. FIG. 2 is a simplified plan view of the injection molding machine, and FIG. 3 is a right side view of FIG. 2 and 3, reference numeral 31 denotes a main part of the high-pressure gas supply device, which is constituted by removing the pneumatic valve unit 30 and the molding die 20 from the configuration of FIG. The part 31 is a main frame 3 of a machine (injection molding machine).
2 are arranged on the rear side. Further, as shown in FIG. 2, the fixed die plate 3 with the fixed mold 20A attached thereto.
The unit halves 30A, 30B of the pneumatic valve unit 30 are attached to the movable die plate 34 to which the movable mold 20B is attached, respectively. Here, in this embodiment, the pneumatic valve unit 30 is separated into unit halves 30A and 30B.
Pneumatic valve unit 30 combining A and 30B into one
May be attached to one of the fixed die plate 33 and the movable die plate 34.

Although not shown in FIGS. 2 and 3,
Main part 31 of high pressure gas supply device and pneumatic valve unit 3
0, the pipeline shown in FIG. 1 is arranged and connected, and between the pneumatic valve unit 30 and the gas injection port of the molding die 20, the pipeline shown in FIG. Are placed and connected. As a result, the length of the conduit between the pneumatic valve unit 30 and the gas inlet of the molding die 20 is very short.

2 and 3, reference numeral 35 denotes a support plate (tail stock), 36 denotes a mold clamping (mold opening / closing) cylinder, 36a denotes a piston rod of the mold clamping cylinder, 37 denotes a tie bar, and 38 denotes an injection unit. These configurations
Since the operation is generally known, a detailed description thereof is omitted here.

In the structure shown in FIG. 1, the air taken in from the intake port 1 is dust-removed by a filter 2 and moisture and oil are removed by a mist separator 3, and then nitrogen gas is generated through a pressure reducing valve 4. Is supplied to the vessel 6. Further, air is also supplied from the mist separator 3 to the electromagnetic control valves 18 and 19 via the pressure reducing valve 5. In the nitrogen gas generator 6, oxygen is removed from the atmosphere by a known filter method or adsorption method, and nitrogen gas is generated and output. The pressure of the atmosphere introduced from the intake port 1 is about 5 kgf / cm ² , and in this embodiment, the pressure of the nitrogen gas discharged from the nitrogen gas generator 6 is 3 kgf / cm ^2.
cm ² .

The nitrogen gas output from the nitrogen gas generator 6 is supplied through a flow meter 7, a throttle valve 8, and a check valve 9 to a gas booster mechanism 11 whose details will be described later. The pressure is increased (compressed) to a set pressure for press-fitting into the resin in the cavity 21 by the gas pressure increasing mechanism 11 that is driven and controlled in 12. The high-pressure nitrogen gas output from the gas pressure raising mechanism 11 is injected (injected) into a resin (not shown) in the cavity 21 via a switching control valve 16 controlled by air from an electromagnetic control valve 18. When the timing of the exhaust gas after the solidification of the molded article is reached, the switching control valve 16 is closed, and nitrogen gas is released to the atmosphere through the switching control valve 17 controlled by air from the electromagnetic control valve 19. .

In this embodiment, high-pressure nitrogen gas is injected from the molding die 20 into the resin. However, the injection point (gas injection port) of the high-pressure nitrogen gas is a nozzle or the like of an injection mechanism. If the gas inlet is provided in the nozzle as described above, the pneumatic valve unit 30 is installed on a fixed die plate, a heating cylinder, or the like.

Next, details of the gas pressure raising mechanism 11 will be described. In the present embodiment, the gas pressure increasing mechanism 11 includes two first gas compression cylinders 22 and one second gas compression cylinder 23, and the nitrogen gas from the nitrogen gas generator 6 Through the check valve 9, the first paired
Is introduced into the compression chamber 22a of the gas compression cylinder 22. Also, the first gas compression cylinder 22
The pressurized (compressed) nitrogen gas is introduced into the compression chamber 23 a of the second gas compression cylinder 23 via the check valve 10, and further pressurized (compressed) by the second gas compression cylinder 23. It has become.

As shown in FIG. 1, the electric servomotor 12
A pulley 24 is fixed to the output shaft of the motor. A timing belt 26 is stretched between the pulley 24 and a nut body 25 with a pulley.
The nut body 25 with the pulley is rotationally driven by the rotation of the nut. The nut body 25 with a pulley is held so as to be rotatable but not displaceable in the axial direction. A ball screw 27 is screwed to the nut body 25 with a pulley. The ball screw 27 moves in the axial direction. That is, a known ball screw mechanism constitutes a rotation → linear motion conversion mechanism for converting the rotation of the electric servomotor 12 into a linear motion.

The piston body 23b of the second gas compression cylinder 23 is connected to the ball screw 27 via a connecting mechanism as necessary, and the connecting members 28 and 2 are connected.
9 through the piston body 2 of the first gas compression cylinder 22
2b are connected. Therefore, the electric servomotor 12
Is rotated in the first direction, and the ball screw 27 is driven in the direction of arrow A in FIG. 1, the nitrogen gas in the compression chamber 22a of the first gas compression cylinder 22 is compressed by the piston body 22b. The pressure is increased and the second gas compression cylinder 23
Is introduced through the check valve 10 into the compression chamber 23a.
In the present embodiment, the first gas compression cylinder 22
Nitrogen gas pressure is about 3kgf / cm ² to 30kgf
/ Cm ² .

Further, when the electric servomotor 12 rotates in the second direction and the ball screw 27 is driven in the direction of arrow B in FIG. 1, the first gas compression cylinder 22 to the second gas compression cylinder 23 The nitrogen gas introduced into the compression chamber 23a is compressed by the piston body 23b, and the pressure is further increased. In this embodiment, the molten resin in the cavity 21 contains 100 kgf / cm
It is assumed that high-pressure nitrogen gas in the range of ^{2 to} 270 kgf / cm ² is injected, and the nitrogen gas is pressurized by the second gas compression cylinder 23 according to a set value.

Here, an accurate value of the gas pressure in the compression chamber 23a before compression can be detected by the pressure gauge 15, and the compression stroke is determined by an encoder (not shown) attached to the electric servomotor 12. Therefore, during the molding operation in the gas injection molding mode, the system controller of the machine (not shown) that captures these pieces of detection information performs the pressure holding setting condition of the gas injection molding mode set by the operator (this embodiment). Then, based on the gas pressure values which can be set in multiple stages along the time axis), the pressure feedback control of the electric servomotor 12 is performed via a servo amplifier (not shown) during the pressure increasing operation by the second gas compression cylinder 23. . That is, in the present embodiment, before the compression operation of the second gas compression cylinder 23, the compression chamber based on the gas pressure in the compression chamber 23a and the position information of the piston body 23b (encoder information of the electric servomotor 12). With the capacity of 23a, the system controller of the machine calculates the compression stroke required to obtain the set gas pressure,
The drive of the electric servomotor 12 is controlled via the servo amplifier based on the calculated value. At this time, the electric servomotor 1
2, the feedback control (current value feedback control) of the drive current value corresponding to the output torque calculated from the set gas pressure value is performed, whereby the pressure feedback control is achieved.

In this embodiment, the gas amount of the high-pressure nitrogen gas to be injected into the resin is not accurately measured, and the cavity volume value given at the initial setting of the molding conditions and the pressure at the start of the injection into the resin are not measured. Based on the gas pressure set value, the volume of the compression chamber 23a (the position of the piston body 23b) before compression is determined in advance by a system controller of the machine with a margin. Then, at the time of gas injection into the resin, the servo is controlled by the current value feedback control so that the set gas pressure value and the actually measured gas pressure value (here, the actually measured driving current value corresponding to the actually measured gas pressure value) match. The motor 12 is driven. The reason for this is that gas injection into the resin replaces the operation of applying a holding pressure via the cushion resin with a screw or the like in the first place, and pressure control is the most important control item. It is. Experiments have confirmed that the amount of high-pressure nitrogen gas injected into the resin is substantially stable even when such control is performed.

Next, the operation of the high-pressure gas supply device during the gas injection molding mode operation will be described. Before the compression operation of the nitrogen gas in the one-shot molding cycle, the switching control valves 16 and 17 are in the closed position, and in this state, the nitrogen gas is supplied from the nitrogen gas generator 6 to
The gas is introduced into the compression chamber 22a of the first gas compression cylinder 22 via the check valve 9 and the like. When a predetermined amount of nitrogen gas is stored in the compression chamber 22a, the servomotor 12 is driven to move the ball screw 27 in the direction of arrow A in FIG.
As a result, the piston body 22b of the first gas compression cylinder 22 also moves in the direction of arrow A, and the nitrogen gas in the compression chamber 22a is compressed and pressurized, and the pressurized nitrogen gas passes through the check valve 10. Is introduced into the compression chamber 23a of the second gas compression cylinder 23.

Next, the servo motor 12 is driven in the opposite direction by the current value feedback control as described above, and the ball screw 27 moves in the direction of arrow B in FIG. Thereby, the piston body 2 of the second gas compression cylinder 23
3b moves in the direction of arrow B by a predetermined compression stroke,
The nitrogen gas in the compression chamber 23a of the second gas compression cylinder 23 is increased to the set pressure value at the start of press-fitting. Then, at a timing when a predetermined amount of the molten resin is injected into the cavity 21, the switching control valve 16 is opened by the electromagnetic control valve 18, and a high-pressure nitrogen gas having a predetermined set pressure is injected into the molten resin in the cavity 21. . Here, as described above, since the pipeline between the pneumatic valve unit 30 and the gas inlet is very short, the high-pressure nitrogen gas is injected into the resin with extremely high responsiveness.

Even after the switching control valve 16 is opened, the servo motor 12 continues to be driven by the current value feedback control. For example, if the gas pressure set value during the gas press-in process is a constant value, the pressure becomes lower. The piston body 23b is gradually moved in the direction of arrow B in FIG. 1 to monitor the current value so that the constant value is maintained (that is, the corresponding drive current value (torque value) is constant). While performing current value feedback control.

If the gas pressure conditions for the gas injection step into the resin are set in multiple stages, the gas pressure is similarly variably controlled according to the set conditions during the gas injection step. For example,
Under the gas pressure setting condition as shown in FIG. 4, after a predetermined time t1 from the start of gas injection, the piston body 23b is moved in the direction of arrow B in FIG. While moving, current value feedback control is performed while monitoring the current value by the servomotor 12 so that the drive current value (torque value) corresponding to the pressure P2 is obtained. After a predetermined time t2 from the start of gas injection, the piston body 23b is moved in the direction of arrow A in FIG.
The current value feedback control is performed while monitoring the current value by the servo motor 12 so that the driving current value (torque value) corresponding to. In FIG. 4, the dashed line indicates the measured value of the gas pressure by the pressure gauge 15.

Even when such pressure feedback control is performed, the above-described short pipe length between the pneumatic valve unit 30 and the gas injection port is effective, and is sensitive and responsive. It greatly contributes to pressure feedback control.

Thereafter, when the resin in the cavity 21 is solidified, the piston body 23b is rapidly driven in the direction of the arrow A in FIG. 1 to reduce the pressure in the compression chamber 23a, thereby reducing the pressure in the resin and the pipeline. The nitrogen gas is collected in the compression chamber 23a. Thereafter, the switching control valve 16 is closed by the electromagnetic control valve 18,
Next, the switching control valve 17 is opened for a short time by the electromagnetic control valve 19 so that the nitrogen gas in the resin, which is still at a considerably higher pressure than the atmospheric pressure, or a short pipe line (the pneumatic valve unit 3).
The nitrogen gas (in the line between 0 and the gas inlet) is released. Therefore, the high-pressure gas is recovered to the high-pressure gas supply source (the second gas compression cylinder 23) before the gas exhaust stroke, and the pipe length between the pneumatic valve unit 30 and the gas inlet is short. In combination, wasteful consumption of high-pressure nitrogen gas can be reduced as much as possible, and running costs can be significantly reduced. Even if the high-pressure gas is not collected before the gas exhausting process, since the pipe length between the pneumatic valve unit 30 and the gas inlet is short, wasteful consumption of the high-pressure nitrogen gas is significantly reduced as compared with the conventional case. Needless to say, it can be reduced.

With the above operation, the operation of the high-pressure gas supply device in the one-shot molding cycle is completed.

As described above, according to this embodiment, since the pneumatic valve unit 30 is disposed near the gas inlet, the piping between the pneumatic valve unit 30 and the gas inlet is shortened. Accordingly, the press-in control of the high-pressure gas can be performed with good responsiveness according to the ON / OFF of the switching control valve and the pressure feedback control, which contributes to the further good molding. Also,
Since the length of the pipe between the pneumatic valve unit 30 and the gas inlet is short, even if a system is used in which the high-pressure gas from the pneumatic valve unit 30 is released to the atmosphere during the gas exhaust stroke, wasteful gas consumption is greatly reduced. it can.

Further, according to the present embodiment, since the nitrogen gas is pressurized in two stages, the required high pressure can be easily obtained, and the gas pressurizing mechanism can be made compact and inexpensive. Therefore, even if a gas pressure increasing mechanism is attached to each injection molding machine, the space factor is improved, and the layout in the factory is refreshed. In addition, a variable-capacity gas compression cylinder makes it possible to obtain a necessary and sufficient amount of high-pressure gas for each shot, so that high-pressure gas can be small in volume and legal regulations are reduced, making management and operation simple. Becomes

Further, according to the present embodiment, an electric servomotor is used as a drive source for boosting the pressure, and at least when the gas is injected into the resin, the pressure is feedback-controlled. Can be controlled so as to match the set conditions, and therefore, the dwell pressure control by the gas pressure can be performed precisely, which greatly contributes to the molding of non-defective products.

Although the present invention has been described with reference to the illustrated embodiments, it is needless to say that various modifications can be made by those skilled in the art without departing from the spirit of the present invention.
It is obvious to those skilled in the art that the valve in the pneumatic valve unit can be composed of only two electromagnetically controlled switching control valves.

[0035]

As described above, according to the present invention, in an injection molding machine capable of gas injection molding, the response of gas press-in control can be made good, and the wasteful consumption of high-pressure gas can be reduced. It has a remarkable effect that it can be reduced as much as possible.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an outline of a high-pressure gas supply device of an injection molding machine according to one embodiment of the present invention.

FIG. 2 is a simplified plan view of an injection molding machine according to one embodiment of the present invention.

FIG. 3 is a right side view of FIG. 2;

FIG. 4 shows an injection molding machine according to one embodiment of the present invention.
It is explanatory drawing which shows an example of the gas pressure setting condition at the time of a gas press-in stroke.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 air intake 2 filter 3 mist separator 4,5 pressure reducing valve 6 nitrogen gas generator (nitrogen gas generator) 7 flow meter 8 throttle valve 9,10 check valve 11 gas pressure increasing mechanism 12 electric servomotor 13,14, 15 Pressure gauge 16, 17 Switching control valve 18, 19 Electromagnetic control valve 20 Mold for molding 20A Fixed mold 20B Movable mold 21 Cavity 22 First gas compression cylinder 22a Compression chamber 22b Piston body 23 Second gas compression Cylinder 23a Compression chamber 23b Piston body 24 Pulley 25 Nut body with pulley 26 Timing belt 27 Ball screw 30 Pneumatic valve unit 30A, 30B Half unit of pneumatic valve unit 31 Main part of high-pressure gas supply device 33 Fixed die plate 34 Movable die plate

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-312431 (JP, A) JP-A-61-170521 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 45/00-45/84

Claims (2)

(57) [Claims] 1. An injection molding machine capable of injecting molten resin into a cavity of a mold and press-injecting high-pressure gas into the resin in the cavity, wherein a gas injection point is provided in the mold. A pneumatic valve unit including at least a switching control valve for press-in control for injecting gas from a high-pressure gas supply source into the resin and a switching control valve for exhaust control for exhausting gas from the resin, An injection molding machine characterized by being provided on a die plate for mounting a mold. 2. The injection molding machine according to claim 1, wherein the pneumatic valve unit is provided separately from a fixed die plate and a movable die plate.