JP3299866B2 - Injection molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for injecting a molten resin into a cavity of a mold (space for forming a molded product) and forcing (injecting) a high-pressure gas into the resin in the cavity.
The present invention relates to an injection molding machine for performing gas injection molding, which is one type of hollow injection molding, and in particular, a method in which a molten resin and a high-pressure gas are selectively injected into a mold with a time lag from an injection nozzle. The present invention relates to an injection molding machine for gas injection molding.

[0002]

^2. Description of the Related Art A molten resin is injected into a cavity of a mold, and before the molten resin in the cavity is solidified, a high-pressure inert gas of about 100 to 300 kg / cm ² (usually nitrogen gas) is introduced into the resin. In gas injection molding, press-fitting is performed by applying a holding pressure to the resin from the inside of the resin and pressing the surface side of the resin against the inner wall surface of the cavity, so that a good product without sink marks can be formed. Product weight can also be reduced.

In such gas injection molding, gas is injected (injected) into the resin in the cavity by introducing the gas into the resin in the cavity from an injection nozzle via a sprue, a runner, and a gate. Technique. A method in which a gas supply passage is formed in a mold, and gas is introduced into the resin in the cavity through the gas supply passage. It is common to take any one of the following.

In the above method, it is not necessary to form a gas supply passage for each mold, but the injection mechanism system is dedicated to gas injection molding. Further, in the above method, a gas supply passage must be formed for each mold, but since gas injection can be performed in synchronization with resin flow, a molded article having a high hollowness can be obtained, Also, the injection mechanism system need not be dedicated to gas injection molding. Therefore, the above method and the above method are appropriately used as needed, but the present invention belongs to an injection molding machine that adopts the former method.

Next, a conventional injection molding machine in which high-pressure gas is injected from an injection nozzle will be described with reference to FIG. FIG. 5 is a diagram showing a main configuration of an injection mechanism system of a conventional injection molding machine.

In FIG. 5, 1 is a heating cylinder, 2 is
A screw 3 is provided in the heating cylinder 1 so as to be able to rotate and move forward and backward. A check valve 3 is provided on a head portion of the screw, 4 is a nozzle holding cylinder screwed to a tip side of the heating cylinder 1, Reference numeral 5 denotes an injection nozzle screwed to the tip end side of the nozzle holding cylinder 3, 5 a denotes a nozzle hole of the injection nozzle 5, 6 denotes a needle holding body fixed so as to be in close contact with the inner peripheral surface of the nozzle holding cylinder 4, The heating cylinder 1 is bored in the axial direction so as to penetrate the needle holder 6 back and forth.
A plurality of molten resin passages communicating the space 1a on the tip side of the nozzle with the space 5b in the injection nozzle 5, 6b is a bottomed central hole formed in the needle holder 6, and 7 ″ is in the central hole 6b. The needle body 7a, the rear side of which is inserted so as to be able to move forward and backward by a predetermined amount, extends inside the needle body 7 "from the outer surface of the intermediate portion of the needle body 7" to the tip of the needle body 7 ". The first gas passage 8 pierced in the needle body 7 ″ is connected to the nozzle holding cylinder 4 and the needle so that the outer surface of the nozzle holding cylinder 4 extends to the center hole 6 b of the needle holding body 6. A second gas passage 9 pierced in the radial direction of the holder 6 is provided with a high-pressure gas supply source for supplying a high-pressure gas set at a predetermined pressure, for example, a high-pressure nitrogen gas, and 10 is a supply switch. Control valve (electromagnetic switching control valve), 11 is switching for exhaust Valve (electromagnetic switching valve), 1
Reference numeral 2 denotes a needle driving body which is held so as to be rotatable by a predetermined amount and is rotationally driven by an appropriate driving source. A driving unit of the needle driving body 12 in contact therewith;
Reference numeral 12c denotes a driven part of the needle driving body 12 which receives a force from the driving source. The driving body housing hole is formed in the radial direction of the nozzle holding cylinder 4 and the needle holding body 6 so as to be continuous.

In the configuration shown in FIG. 5, in a state before the injection after the end of the metering, the screw 2 is at the injection start position retracted from the position in FIG. Space 1a, needle holder 6
In the molten resin passage 6a and the space 5b in the injection nozzle 5,
The molten resin of a predetermined resin pressure that is measured and stored is filled. Further, at this time, the needle driving body 12 is located at the position indicated by the two-dot chain line in FIG. 5, and the needle body 7 ″ receiving the pressure of the molten resin is at the position retracted from the position of FIG. As a result, the first gas passage 7a and the second
And the passage of the molten resin in the injection nozzle 5 to the mold is in an open state. At this time, the supply switching control valve 10 and the exhaust switching control valve 11 are both closed.

In the above state, when the injection start timing is reached, the screw 2 is driven by an injection drive source (not shown).
Is rapidly advanced, and molten resin flows from the space 1a on the distal end side of the heating cylinder through the molten resin passage 6a of the needle holder 6, the space 5b in the injection cylinder 5, and the nozzle hole 5a, not shown. Injected into the mold. The screw 2 in FIG. 5 is shown at a position where the injection is completed (injection completed position).

Immediately after the injection is completed, the needle driver 12 is rotated from the two-dot chain line position to the solid line position by a needle position switching drive source (not shown). Then, the needle body 7 "whose rear end face is pushed forward moves forward. The needle body 7" shown in FIG.
Is shown in this forward position. When the needle body 7 "advances, the tip of the needle body 7" is pressed against the nozzle hole 5a of the injection nozzle 5, whereby the passage of the molten resin in the injection nozzle 5 to the mold is shut off,
The first gas passage 7a and the second gas passage 8 are communicated with each other, so that a high-pressure gas can be injected into the mold from the nozzle hole 5a.

Thereafter, the supply switching control valve 10 is opened, and the gas at a predetermined pressure from the high pressure gas supply source 9 is supplied to the second gas passage 8, the first gas passage 7a, the nozzle hole 5a, the sprue, and the runner. , Through the gate, is injected (injected) into the resin before solidification in the cavity of the mold. As a result, a holding pressure is applied to the resin from the inside of the resin by the high-pressure gas, and the surface side of the resin is pressed against the inner wall surface of the cavity, thereby guaranteeing good-quality molding without sink marks.

When the pressure-holding process using the high-pressure gas is completed, that is, when the resin in the cavity is solidified so as to maintain its outer shape, the supply switching control valve 10
Is closed, and after the predetermined timing, the exhaust switching control valve 11 is opened. As a result, in the resin in the mold,
The high-pressure gas present in the first and second gas passages 7a and 8 is exhausted (depressurized) (degassed). Note that the exhaust switching control valve 11 is closed at an appropriate timing after degassing.

When the above-mentioned degassing is completed, the needle driving body 12 is rotated from the solid line position to the two-dot chain line position by a needle position switching drive source (not shown). The needle body 7 "is retracted by the pressure of the filled molten resin. Therefore, the first gas passage 7a and the second gas passage 8 are disconnected from each other, and the molten resin mold in the injection nozzle 5 is opened. The passage to is opened.

[0013]

As described above, the conventional injection molding machine for gas injection molding shown in FIG. 5 uses the needle driving body 12 driven and controlled by the needle position switching drive source. The position of the needle body 7 "is switched. Therefore, a relatively expensive driving source such as a hydraulic cylinder, an air cylinder, or a motor is required as a needle position switching driving source.
The increased number of parts has been a bottleneck in reducing the cost of the entire machine (injection molding machine).

Accordingly, a technical problem to be solved by the present invention is to solve the above-mentioned problems of the prior art, and the purpose is to supply molten resin and high-pressure gas from the nozzle hole of the injection nozzle. In order to selectively inject into the mold with a time difference, in an injection molding machine for gas injection molding having a needle body whose advance / retreat position is controlled, a special purpose is used for switching the advance / retreat position of the needle body. An object of the present invention is to realize an injection molding machine which does not require a driving source and which can simplify a mechanism for switching the advance / retreat position of the needle body, thereby reducing the cost of the injection molding machine.

[0015]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method for selectively injecting a molten resin and a high-pressure gas into a mold with a time lag from a nozzle hole of an injection nozzle. In an injection molding machine for gas injection molding having a needle body whose retreat position is controlled , a high- pressure gas is used to advance the needle body and hold the advance position of the needle body. Then, configure.

[0016]

That is, the rear end face of the needle body is configured to be able to be pressed by the high-pressure gas, and immediately after the injection by the screw advance is completed, the needle body is advanced by the force of the high-pressure gas to turn off the injection path of the molten resin. At the same time, the injection path of the high-pressure gas is turned on. Further, at the time of retreat control of the needle body, the gas pressure on the rear end face side of the needle body is reduced by performing degassing, whereby the needle body is retracted by the pressure of the molten resin in the injection nozzle,
The molten resin injection path is turned on, and the high-pressure gas injection path is turned off.

[0018]

Embodiments of the present invention will be described below. FIG. 1 and FIG. 2 are diagrams showing a main configuration of an injection mechanism system in an injection molding machine for gas injection molding according to a first embodiment of the present invention (hereinafter, referred to as a first example). Reference numeral 1 denotes a state in which the pressure is maintained by the high-pressure gas, and FIG. 2 shows a state after the pressure-holding process is completed.

1 and 2, reference numeral 1 denotes a heating cylinder,
Reference numeral 2 denotes a screw disposed in the heating cylinder 1 so as to be able to rotate and move forward and backward. 3 denotes a check valve provided in a head portion of the screw. 4 denotes a nozzle screwed to the tip side of the heating cylinder 1. The holding cylinder, 5 is an injection nozzle screwed to the tip side of the nozzle holding cylinder 3, 5a is a nozzle hole of the injection nozzle 5, and 6 is a needle holder fixed so as to be in close contact with the inner peripheral surface of the nozzle holding cylinder 4. , 6a are the needle holder 6
And a plurality of molten resin passages 6 b ′ communicating with the space 1 a on the distal end side of the heating cylinder 1 and the space 5 b in the injection nozzle 5. The center hole 7 composed of the provided through-hole is a needle body inserted through the center hole 6b 'so that it can move forward and backward by a predetermined amount into the center hole 6b', and 7a is a needle body. The first gas passage, 8 pierced in the needle body 7 is connected to the outside surface of the nozzle holding cylinder 4 so as to continue inside the needle body 7 from the outer surface of the intermediate portion of the needle member 7 to the tip of the needle body 7. The nozzle holding cylinder 4 and the second gas passage 9 pierced in the radial direction of the needle holding body 6 are connected to a high pressure set at a predetermined pressure so that the center hole 6b 'of the needle holding body 6 extends from Gas, for example high pressure gas for supplying high pressure nitrogen gas A supply source 10 is a supply switching control valve (electromagnetic switching control valve), and 11 is an exhaust switching control valve (electromagnetic switching control valve).

In the configuration shown in FIGS. 1 and 2, in the state before the injection after the end of the metering, the screw 2 is at the injection start position further retreated than the position in FIG. The space 1a on the distal end side of the heating cylinder, the molten resin passage 6a of the needle holder 6, and the space 5b in the injection nozzle 5 are filled with the molten resin of a predetermined resin pressure measured and stored. At this time, the needle body 7 receiving the pressure of the molten resin is at the retracted position shown in FIG. As a result, the first gas passage 7a and the second gas passage 8 are disconnected from each other, and the passage of the molten resin in the injection nozzle 5 to the mold is opened. At this time, the supply switching control valve 10 and the exhaust switching control valve 1
1 are both in the closed state.

In the above state, when the injection start timing is reached, the screw 2 is driven by an injection drive source (not shown).
Is rapidly driven forward, and molten resin flows from the space 1a on the distal end side of the heating cylinder 1 through the molten resin passage 6a of the needle holder 6, the space 5b in the injection cylinder 5, and the nozzle hole 5a. Injected into a mold. Then, as the screw 2 advances at the end of the injection stroke, the tip of the screw 2 presses the rear end face of the needle body 7 to advance the needle body 7 to the position shown in FIG. As a result, the tip of the needle body 7 is pressed against the nozzle hole 5a of the injection nozzle 5, the passage of the molten resin in the injection nozzle 5 to the mold is cut off, and the first gas passage 7a and the second gas The passage 8 is communicated with the nozzle hole 5 into the mold.
A gas having a pressure higher than a is put in a state where it can be injected.

Immediately after the needle body 7 has advanced as described above, or after a predetermined timing,
The supply switching control valve 10 is opened, and gas at a predetermined pressure from the high-pressure gas supply source 9 passes through the second gas passage 8, the first gas passage 7a, the nozzle hole 5a, the sprue, the runner, and the gate. Is injected (injected) into the resin before solidification in the cavity of the mold. As a result, a holding pressure is applied to the resin from the inside of the resin by the high-pressure gas, and the surface side of the resin is pressed against the inner wall surface of the cavity, thereby guaranteeing good-quality molding without sink marks.

When the pressure-holding process using the high-pressure gas is completed, that is, when the resin in the cavity is solidified so as to maintain its outer shape, the supply switching control valve 10
Is closed, and after the predetermined timing, the exhaust switching control valve 11 is opened. As a result, in the resin in the mold,
The high-pressure gas present in the first and second gas passages 7a and 8 is exhausted (depressurized) (degassed). Note that the exhaust switching control valve 11 is closed at an appropriate timing after degassing.

When the above-mentioned degassing is completed, the screw 2 is rapidly forcibly retracted from the position shown in FIG. 1 to the position shown in FIG. 2, whereby the pressure of the molten resin filled in the space 5b in the injection nozzle 5 The needle body 7 retreats to the position shown in FIG. Accordingly, the communication between the first gas passage 7a and the second gas passage 8 is cut off, and the passage of the molten resin in the injection nozzle 5 to the mold is opened.

In the first example of such a configuration / operation,
Since the pressing force of the screw 2 is used to advance the needle body 7 and maintain the advance position of the needle body 7, a dedicated drive source is used to switch the advance / retreat position of the needle body. It is not necessary, and the mechanism for switching the advance / retreat position of the needle body can be simplified.

Next, a second embodiment of the present invention (hereinafter, referred to as a second embodiment)
A second example will be described. FIG. 3 and FIG.
FIG. 3 is a diagram showing a main configuration of an injection mechanism system in an injection molding machine for gas injection molding according to an example. FIG. 3 shows a state in which a dwell pressure is applied by high-pressure gas, and FIG. Respectively are shown. 3 and 4, the same components as those in FIGS. 1 and 2 are denoted by the same reference numerals, and description thereof will be omitted to avoid duplication.

3 and 4, reference numeral 6 'denotes a needle holder fixed so as to be in close contact with the inner peripheral surface of the nozzle holding tube 4, and 6b denotes a bottomed center hole formed in the needle holder 6'. , 7 ′ is a needle body whose rear side is inserted into the center hole 6b so as to be able to move forward and backward by a predetermined amount, 7a ′
A first gas passage 6c formed in the needle body 7 'is fixed to the bottom of the center hole 6b so as to penetrate from the rear end to the front end of the needle body 7'. The gas passage sealing body having a conical front end capable of sealing the rear end of the first gas passage 7a 'when the
A small space formed near the bottom of the center hole 6b of the needle holder 6 'even when the needle body 7' is at the retreat limit position;
8 ′ is a nozzle holding cylinder 4 so that the outer surface of the nozzle holding cylinder 4 extends to the small space 6d of the needle holder 6 ′.
And a second gas passage formed in the needle holder 6 '.

In the configuration shown in FIGS. 3 and 4, in the state before the injection after the end of the metering, the screw 2 is at the injection start position retracted from the position shown in FIG. The space 1a on the distal end side, the molten resin passage 6a of the needle holder 6 ', and the space 5b in the injection nozzle 5 are filled with the molten resin of a predetermined resin pressure measured and stored. At this time, the pressure in the small space 6d of the needle holding member 6 'is substantially equal to the atmospheric pressure. Therefore, the needle member 7' receiving the pressure of the molten resin is in the retracted position shown in FIG. Of the gas passage 7a 'is closed by the gas passage sealing body 6c. As a result, the first gas passage 7a 'and the second gas passage 8' are disconnected from each other, and the passage of the molten resin in the injection nozzle 5 to the mold is opened. is there. At this time, the supply switching control valve 10 and the exhaust switching control valve 11 are both closed.

In the above state, when the injection start timing is reached, the screw 2 is driven by an injection drive source (not shown).
Is rapidly advanced, and molten resin flows from the space 1a on the distal end side of the heating cylinder through the molten resin passage 6a of the needle holder 6 ', the space 5b in the injection cylinder 5, and the nozzle hole 5a. Injected into a mold.

When the screw 2 advances to the forward limit position shown in FIGS. 3 and 4 and the injection of the molten resin into the mold is completed, the supply switching control valve 10 is opened immediately and the second From the gas passage 8 'to the small space 6d of the needle holder 6'
A high-pressure gas is fed into the inside, whereby the needle body 7 ′ whose rear end face is pressed by the high-pressure gas advances from the position in FIG. 4 to the position in FIG. When the needle body 7 ′ is driven forward, the tip of the needle body 7 ′ is pressed against the nozzle hole 5 a of the injection nozzle 5, thereby blocking the passage of the molten resin in the injection nozzle 5 to the mold. ,
The first gas passage 7a 'and the second gas passage 8' communicate with each other via the small space 6d.

The supply of the high-pressure gas is continued even after the needle body 7 'advances, so that the gas at a predetermined pressure from the high-pressure gas supply source 9 is supplied to the second gas passage 8', the small space 6d,
Via the first gas passage 7a ', the nozzle hole 5a, the sprue, the runner, and the gate, it is press-fitted (injected) into the resin before solidification in the cavity of the mold. As a result, a holding pressure is applied to the resin from the inside of the resin by the high-pressure gas, and the surface side of the resin is pressed against the inner wall surface of the cavity, thereby guaranteeing good-quality molding without sink marks.

When the pressure-holding process using the high-pressure gas is completed, that is, when the resin in the cavity is solidified so as to maintain its outer shape, first, the supply switching control valve 10
Is closed, and after the predetermined timing, the exhaust switching control valve 11 is opened. As a result, in the resin in the mold,
First gas passage 7a ', small space 6d, second gas passage 8'
The high-pressure gas present in the gas is exhausted (depressurized) (gas is released).

When the above-mentioned degassing is completed, the small space 6d
The internal gas pressure is reduced to substantially the atmospheric pressure. Therefore, the needle body 7 ′ retreats to the position shown in FIG. 4 by the pressure of the molten resin filled in the space 5 b in the injection nozzle 5. Accordingly, the communication between the first gas passage 7a 'and the second gas passage 8' is cut off, and the passage of the molten resin in the injection nozzle 5 to the mold is opened. The exhaust switching control valve 11
Is closed at an appropriate timing after degassing.

In the second example of such a configuration / operation,
Since the force of the high pressure gas for holding pressure is used to advance the needle body 7 'and hold the advance position of the needle body 7', it is necessary to switch the advance / retreat position of the needle body. Therefore, a dedicated driving source is not required, and a mechanism for switching the forward / retreat position of the needle body can be simplified.

[0035]

As described above, according to the present invention, the molten resin and the high-pressure gas are selectively injected into the mold with a time difference from the nozzle hole of the injection nozzle. In an injection molding machine for gas injection molding having a needle body, a dedicated drive source for switching the advance / retreat position of the needle body is not required, and a mechanism for switching the advance / retreat position of the needle body is provided. An injection molding machine that can be simplified can be realized, and therefore, the cost of the machine (injection molding machine) can be reduced. The value of such an injection molding machine for gas injection molding is enormous.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a main configuration of an injection mechanism system in a state where a pressure is maintained by a high-pressure gas in an injection molding machine for gas injection molding according to a first embodiment of the present invention. .

FIG. 2 is an explanatory diagram showing a main configuration of an injection mechanism system in a state after a pressure-holding process is completed in an injection molding machine for gas injection molding according to a first embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a main configuration of an injection mechanism system in a state where a pressure is maintained by a high-pressure gas in an injection molding machine for gas injection molding according to a second embodiment of the present invention. .

FIG. 4 is an explanatory diagram showing a main configuration of an injection mechanism system in a state after a pressure-holding process is completed in the injection molding machine for gas injection molding according to the first embodiment of the present invention.

FIG. 5 is an explanatory view showing a main configuration of an injection mechanism system in a conventional injection molding machine for gas injection molding.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating cylinder 1a Space on the tip side of heating cylinder 2 Screw 3 Check valve 4 Nozzle holding cylinder 5 Injection nozzle 5a Nozzle hole 5b Space in injection nozzle 6,6 'Needle holder 6a Molten resin passage 6b, 6b' Center hole 6c Gas passage sealing body 6d Small space 7,7 ', 7 "Needle body 7,7a' First gas passage 8,8 'Second gas passage 9 High-pressure gas supply source 10 Supply switching control valve 11 Exhaust switching Control valve

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-7-32419 (JP, A) JP-A-3-67623 (JP, A) JP-A-3-43218 (JP, A) JP-A-3-32418 24930 (JP, A) Japanese Utility Model Application Hei 3-88711 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) B29C 45/00-45/84

Claims (1)

(57) [Claims] 1. A gas injection molding machine for injecting a high-pressure gas from an injection nozzle into a resin in a cavity after injecting a molten resin into a cavity of a mold. A heating cylinder incorporated as possible, a nozzle holding cylinder attached to the tip side of the heating cylinder, an injection nozzle attached to the tip side of the nozzle holding cylinder, and fixed inside the nozzle holding cylinder; A needle holder provided with a molten resin passage communicating the space on the distal end side of the heating cylinder and the space in the injection nozzle; and a needle holder inserted into a bottomed center hole of the needle holder, and A needle body held so as to be able to move forward and backward, a first gas passage formed in the needle body so as to penetrate from the rear end to the front end of the needle body, and the needle A gas passage sealing means provided at a bottom of a center hole of the holding body and capable of sealing a rear portion of the first gas passage when the needle body is at the retreat limit position; and the needle body is at a retreat limit position. In some cases, the nozzle holding cylinder and the small space formed near the bottom of the center hole of the needle holding body and the small space of the needle holding body from the outer surface of the nozzle holding cylinder are connected. A second gas passage formed in the needle holder, wherein at a timing immediately after the operation of injecting the molten resin into the mold by the advancement of the screw, the screw is moved from the second gas passage to the second gas passage. A high-pressure gas is sent into the small space to advance the needle body, thereby pressing the tip of the needle body against the nozzle hole of the injection nozzle and blocking the passage of the molten resin in the injection nozzle to the mold. The first gas passage communicates with the second gas passage through the small space, and a high-pressure gas is injected into the mold from the nozzle hole. At an appropriate timing after the supply of is completed, by degassing (decompression of gas), the needle body is retracted by the pressure of the molten resin,
Thus, the communication between the first gas passage and the second gas passage is cut off, and the passage of the molten resin in the injection nozzle to the mold is opened.