JP3305531B2 - Molding method of injection foam molding - 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 molding an injection-foam molded article using a resin material containing a foaming agent, and more particularly to a molding method suitable for softening automobile interior parts and the like.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Publication No. 61-4404
No. 9, as disclosed in the publication,
Plastic molded products in which interior materials such as dashboards or other surfaces are covered with a cushioning sponge skin material having a good feel are generally known, and plastic molded products molded using skin molding technology are also used in automobile interiors. It is produced for the softening of parts.

Recently, high-speed running of automobiles has become a normal condition, and rollover accidents have frequently occurred.
As a result of analyzing the state of damage to the human body caused by these accidents, it has become clear that the occupant collides with the chassis of the car, which has led to a serious bruising accident. For this reason, in order to reduce such damage, it is essential to soften the chassis part in the vehicle.

However, since the conventional plastic molded products are all softened with a touch point as a main theme, the degree of impact at the time of collision received from the base material of the chassis is not different from that of the base material. However, it is not suitable as a soft material for reducing damage.

[0005] In some cases, attempts have been made to use a skin molded product, urethane foam, or a foam molded product as a soft material for reducing damage.

[0006]

In the above-mentioned skin molded article, the already produced skin is supplied between the fixed mold and the movable mold for each molding, and the mold is brought to a state corresponding to the final shape of the molded article. Is opened, resin containing a foaming agent or the like is injected, and a mold is closed at a high speed and molded. However, this skin molded product does not increase the foaming ratio during foam molding, and the foam cells are also large and uneven. Therefore, the elastic force is extremely weak, and the effect of reducing damage can hardly be expected.

Also, when urethane foam or the like is used, the elastic force is insufficient, and there is a problem of pollution of materials and the like, and other alternative products are required.

[0008] Furthermore, since the foaming molded article is originally diverted to a molding method for responding to another use, it is not possible to select various enlargement modes, and as a result, the formation of foamed cells becomes non-uniform, resulting in an eggplant-like shape. There is a problem that large foam cells are formed and softening becomes insufficient.

The present invention has been made in view of the above points, and it is possible to obtain a molded product having a small and uniform foam cell, a high expansion ratio, a high elastic force, and an excellent surface appearance. An object of the present invention is to provide a method for molding an injection foam molded article.

[0010]

According to the present invention, a resin containing a foaming agent is injected into a cavity in a mold closed state of an injection molding machine, and after the injection is completed, the resin is expanded by a foaming gas. Move the movable mold while maintaining contact with the mold wall, stop the movable mold at a preset reference thickness position,
After the cooling is completed, the movable die is retracted to take out the product.

[0011] The present invention also provides a method of injecting a resin containing a foaming agent into a cavity in a mold closed state of an injection molding machine, and after completion of the injection, expands the resin by a foaming gas while maintaining contact with a mold wall surface. To stop the movable mold at the preset reference thickness excess position, then advance the movable mold from the reference excess thickness position to compress to the reference thickness position, and after cooling is completed, retract the movable mold. It is characterized by taking out the product.

According to the present invention, a resin containing a foaming agent is injected into a cavity in a mold closed state of an injection molding machine, and immediately after starting the injection process, the resin expands by foaming gas and moves while maintaining contact with a mold wall surface. Move the mold, stop the movable mold at the preset reference thickness position by the end of injection, and after cooling is complete,
The movable mold is retracted to take out the product.

According to the present invention, a resin containing a foaming agent is injected into the cavity while the mold of the injection molding machine is closed. Immediately after the start of the injection step, the resin expands due to the foaming gas and moves while maintaining contact with the mold wall surface. Move the mold, stop the movable mold at the pre-set reference thickness position before the injection is completed, then advance the moving mold from the reference thickness excess position to compress to the reference thickness position and complete cooling. Later, the movable mold is retracted to take out the product.

According to the present invention, a resin containing a foaming agent is injected into a cavity in a mold-open state in which a movable mold is moved to an intermediate position between a mold closing position and a reference thickness position of an injection molding machine, and an injection process is started. Immediately after, the movable mold is moved while maintaining the contact with the mold wall surface due to the expansion of the resin by the foaming gas, and the movable mold is stopped at a preset reference thickness position by the time injection is completed. Is retracted to take out the product.

In the present invention, the resin containing a foaming agent is injected into the cavity with the movable mold moved to the intermediate position between the mold closing position and the reference thickness position of the injection molding machine, and the injection step is started. Immediately after, the movable mold is moved while maintaining the contact with the mold wall surface by the expansion of the resin by the foaming gas, and by the completion of the injection, the movable mold is stopped at a position exceeding the preset reference thickness,
Next, the movable mold is advanced from the reference thickness excess position to compress the movable mold to the reference thickness position, and after the cooling is completed, the movable mold is retracted to take out the product.

[0016]

In the present invention, after the injection of the resin containing the foaming agent is completed, the movable mold is moved while maintaining contact with the mold wall surface by expansion of the resin by the foaming gas. For this reason, it is possible to obtain a molded product having a small and uniform foam cell, an improved foaming ratio, and a large elastic force even with a small thickness.

[0017] By moving the movable mold immediately after the start of the injection, it is possible to achieve a higher expansion ratio and a better surface appearance than a molded product obtained after the completion of the injection. By injecting the resin in the open state, the expansion ratio is higher and the surface appearance can be more excellent than that obtained by injecting the resin in the mold closed state.

Further, the moving mold is stopped at a position exceeding the predetermined reference thickness, and then the moving mold is advanced from the position exceeding the reference thickness and compressed to the reference thickness position, thereby improving the uniformity of foaming. Can be improved.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an injection molding apparatus according to a first embodiment of the present invention. The injection molding apparatus 100 includes an injection molding machine 101 and an injection molding machine arranged on the injection side of the injection molding machine 101. The apparatus includes an apparatus 101a and a mold clamping apparatus 101b for opening and closing a mold.

The injection device 101a includes a heating cylinder 105
The heating cylinder 105 is provided with a resin raw material charging section 105B at a rear end thereof, and a heater 105A is wound around an outer peripheral portion of the heating cylinder 105 so that the resin in the heating cylinder 105 has heat required for melting the resin. Is supplied.

A screw 102 is fitted and mounted in the heating cylinder 105. The screw 102 is driven forward and backward in the axial direction by an injection cylinder 103.
It is designed to be rotationally driven by a hydraulic motor 104.

At the entrance and exit of the oil chamber of the injection cylinder 103,
An electromagnetic direction switching valve 103a is connected, and the injection operation, the metering operation, and the suck-back operation of the injection cylinder 103 are switched by the electromagnetic direction switching valve 103a.
An electromagnetic flow control valve 103b is provided in an upstream main line of the electromagnetic direction switching valve 103a, and the flow rate of the pressure oil from the hydraulic pressure source 108 is controlled by the electromagnetic flow control valve 103b.
The pressure oil from the hydraulic source 108 is also supplied to the hydraulic motor 104, and a relief valve 103c is provided in a branch pipe branching between the hydraulic source 108 and the electromagnetic flow control valve 103b. Although a constant discharge pump is normally used as the hydraulic pressure source 108, a variable discharge pump controlled by electronic control may be used. In this case, the electromagnetic flow control valve 103b becomes unnecessary.

In the above configuration, the resin raw material charging section 10
The raw material charged into the heating cylinder 105 from 5B is plasticized by rotation of the screw 102 and heating by the heater 105A, and the molten resin is injected into a mold cavity described later by the forward movement of the screw 102.

The position of the screw 102 is detected by a position detecting device 112, and the detected signal is transmitted to the first to fourth comparators 113c, 114c, 114c, 114c of the injection control device 113A.
115c and 116c. Each of these comparators 113c, 114c, 115c, 116c
The first to fourth screw speed switching position setting devices 11
The set values from 3a, 114a, 115a and 116a are also inputted, and the comparators 113c and 114c
c, 115c, and 116c compare the signal from the position detecting device 112 with the set value, and when they match, the first to fourth screw speed setting devices 113b, 114b,
An activation signal is output to 115b and 116b. Screw speed setting devices 113b, 114b, 115b, 116b
Supplies the preset screw speed set value to the electromagnetic flow control valve 103b via the switching control unit 120 in response to the input of the start signal. Note that each comparator 113
The activation signals from c, 114c, 115c and 116c are
It is also used as a mold opening / closing timing signal as described later. In the case of an electronic control pump, this start signal is sent directly to the control unit.

A pressure sensor 212 is provided in a hydraulic circuit on the injection side of the injection cylinder 103 of the injection device 101a, and a detection signal from the pressure sensor 212 is input to a comparator 213c of the injection control device 113A. . The set value from the injection pressure setting device 213a is also input to the comparator 213c, and the comparator 213c provides a mold opening start signal to the arithmetic device 220 when the values match. This will be described in detail later.

The mold clamping device 101b is, as shown in FIG.
The movable mold 106 is provided with a mold clamping cylinder 350 for driving the movable mold 106 attached to the movable mold mounting plate 107. Mobile type 1 on 110
06 engage so that a mold cavity 111 is formed therebetween. This mold cavity 111
In molding, there are a case where the volume is changed during injection as described later and a case where the volume is changed after injection is completed.

The forward oil chamber 350A of the clamping cylinder 350
An electromagnetic directional control valve 351 for controlling the mold clamping cylinder 350 is provided in a conduit 320 connected to the retreat-side oil chamber 350B.
The upstream pipeline 352 is connected to a hydraulic pressure source 360 via an electromagnetic flow control valve 321. Further, an electromagnetic relief valve 332 for controlling the mold clamping pressure is connected to a branch pipe branching from the upstream pipe 352. Although a constant discharge pump is usually used as the hydraulic pressure source 360, a variable discharge pump controlled by electronic control may be used. In this case, the electromagnetic flow control valve 321 becomes unnecessary.

The movable type mounting plate 107 is provided with a movable type position detecting device 122 for detecting the position of the movable type 106.
The detection signal from the movable type position detecting device 122 is transmitted to, for example, the first to fourth comparators 12 of the mold opening / closing control device 123A.
3c, 124c, 125c, and 126c, respectively. Each of these comparators 123c, 124c, 125c,
The setting values from the first to fourth speed switching position setting devices 123a, 124a, 125a, 126a are also input to 126c.
124c, 125c, and 126c are the first to fourth mobile speed setting devices 123
b, 124b, 125b, 126b. Then, each mobile speed setting device 123b, 124
b, 125b, and 126b calculate the mobile-type set speed that is set in advance by the input of the start signal.
The speed of the movable mold 106 can be controlled in a multi-stage manner by giving it to the electromagnetic flow control valve 321 via a zero.

The mold opening / closing control device 123A also includes the movable mold 1
A first (reference thickness position) mold opening amount setting device 131A and a second (reference thickness excess position) capable of arbitrarily setting the mold opening amount 06
And the set values from the mold opening setting devices 131A and 131B are supplied to the comparator 1 along with the detection signal from the movable mold position detecting device 122.
31Ac and 131Bc are input. Each of the comparators 131Ac and 131Bc outputs a signal when the set value matches the detection signal.

Here, the reference thickness position refers to the movement position of the movable die 106 at which the final molded product thickness can be obtained, and the reference thickness excess position refers to the movable die 106 from the reference thickness position. Is the movement position where is slightly retracted.

Next, the configuration relating to the mold opening timings will be described.
This will be described with reference to FIG.

In FIG. 2, reference numeral 550 denotes a screw position setting device for arbitrarily setting a mold opening start signal, and the set value from the screw position setting device 550 is as follows.
Along with the detection signal from the position detection device 112, the comparator 5
51 is input. When the input set value and the detection signal match, the comparator 551 operates the arithmetic unit 2
A signal is supplied to the electromagnetic directional control valve 351 through the instruction 20 to instruct the mold opening operation at an arbitrary position of the screw during the filling process.

The arithmetic unit 220 also includes the injection control unit 1
13A each of comparators 113c, 114c, 115c, 11
The arithmetic unit 220 also receives signals from the comparators 113c, 114c, and 11c.
The mold opening timing can be controlled using any one of the signals from 5c and 116c.

The arithmetic unit 220 is also supplied with a signal from a timer 552 that is timing from the start of injection, and the mold opening timing can be controlled also by a time-up signal from the timer 552 for a set time.

The arithmetic unit 220 also receives signals from the comparators 131Ac and 131Bc of the mold opening / closing control unit 123A.
The mold opening timing can be controlled using these signals.

Note that these comparators 131Ac, 131
The signal from Bc uses only the signal at the reference thickness position from the comparator 131Ac, and the signal at the reference thickness position after the signal at the reference thickness position from the comparator 131Bc is used. There are two cases. And
The mold opening speed up to the reference thickness position or the position exceeding the reference thickness is controlled by the control of the electromagnetic flow control valve 321. The control of the electromagnetic flow control valve 321 is performed by the mold opening speed control unit 322 shown in FIG. It is.

Next, details of the mold opening speed control unit 322 will be described with reference to FIG.
This will be described with reference to FIG.

In FIG. 3, reference numerals 439, 440, 44
Reference numerals 1 and 442 denote timers.
The timings 40, 441, and 442 are provided from the start of the mold opening process and provide a time-up signal of a set time to the arithmetic unit 420. Reference numerals 433, 434, 435, and 436 denote mold opening speed setting devices.
3,434,435,436 are the timers 439,
The speed at each set time of 440, 441, 442 is set. Then, the arithmetic unit 420 calculates the time set by each of the timers 439, 440, 441, 442 and the mold opening speed setting units 433, 434, 435, 43.
6 to control the electromagnetic flow control valve 321 by calculating a speed gradient for each time based on the speed set in the step S6.
Is controlled as shown in FIG.

FIG. 5 shows a mold opening speed control section 322 having a configuration different from that of FIG. 3, and reference numerals 539, 540,
Reference numerals 541 and 542 denote position setting devices, and these position setting devices 539, 540, 541 and 542 set positions from the start of the mold opening process. In FIG. 5, reference numerals 533, 534, 535 and 536 denote mold opening speed setting devices.
534, 535, 536 are the position setting devices 539,
The speeds at the positions set in 540, 541, and 542 are respectively set. And arithmetic unit 4
Reference numeral 20 denotes each of the position setting devices 539, 540, 541, 5
The position set at 42 and the respective mold opening speed setting devices 53
3, 534, 535, and 536, the velocity gradient for each position is calculated based on the velocity set by the electromagnetic flow control valve 321.
Is controlled, whereby the movable mold 106 is controlled.
Is controlled, for example, as shown in FIG.

In FIG. 1, reference numeral 333 denotes a mold clamping pressure setting device which can arbitrarily set a mold clamping pressure at the time of injection.
32, medium pressure mold clamping setting section 733, and low pressure mold clamping setting section 7
34, and these setting units 732, 733, 7
The set value from 34 is input to the arithmetic unit 722. The arithmetic unit 722 can control the mold clamping pressure to any one of high pressure, medium pressure, and low pressure, and can also perform gradient control of the mold clamping pressure, and at an arbitrary timing during the filling process. It is also possible to switch the mold clamping pressure from a low pressure to a high pressure or vice versa.

Next, a configuration relating to various compression start timings will be described with reference to FIG.

In FIG. 7, reference numeral 650 denotes a screw position setting device for transmitting a mold compression start signal which can be set arbitrarily. The set value from the screw position setting device 650 is set by the position detector 112. The signal is input to the comparator 651 together with the detection signal. When the input set value matches the detection signal, the comparator 651 outputs the electromagnetic directional control valve 3 via the arithmetic unit 520.
A signal is given to 51 to instruct the die compression operation at an arbitrary position of the screw during the filling process.

The arithmetic unit 520 also includes the injection control unit 1
13A each of comparators 113c, 114c, 115c, 11
The arithmetic unit 520 also receives signals from the comparators 113c, 114c, and 11c.
The type compression start timing can also be controlled using one of the signals from 5c and 116c.

The arithmetic unit 520 also includes the injection control unit 1
The signal from the comparator 213c of the 13A is also input.
Can be controlled also by the signal output from the comparator 213c when the set value of the pressure sensor 212 and the detection signal from the pressure sensor 212 match.

The arithmetic unit 520 is also supplied with a signal from a timer 652 that is timing from the start of injection, and the mold compression start timing is controlled by a time-up signal of the set time from the timer 652. it can.

The arithmetic unit 520 also receives signals from the comparators 131Ac and 131Bc of the mold opening / closing control unit 123A.
The type compression timing can be controlled using these signals. Specifically, based on the signal from the comparator 131Bc, it is confirmed that the movable mold 106 has reached the position exceeding the reference thickness, and compression is started, and based on the signal from the comparator 131Ac, the movable mold 106 is After confirming that it has reached the thick position, the compression is stopped.

Next, regarding the multi-stage pressure control during the compression step,
This will be described with reference to FIGS.

In FIG. 8, reference numerals 139, 140, 14
1, 142, 143, 144 are timers, and these timers 139, 140, 141, 142, 143, 14
Reference numeral 4 designates a timing from the start of the compression step, and provides a time-up signal of a set time to the arithmetic unit 340.
8, reference numerals 133, 134, 135 and 13
6, 137 and 138 are compression mold clamping pressure setting devices,
These compression mold clamping pressure setting devices 133, 134, 13
5, 136, 137, and 138 are the timers 139,
The pressure at each set time of 140, 141, 142, 143, 144 is set. Then, the arithmetic unit 340 sets the timers 139, 140, 141, 1
42, 143, 144 and the compression mold clamping pressure setting devices 133, 134, 135, 136, 13
The electromagnetic relief valve 332 is controlled by calculating a pressure gradient for each time based on the pressure set in steps 7 and 138, whereby the mold clamping pressure in the compression step of the movable mold 106 is, for example, as shown in FIG. The control is performed as shown in FIG.

As described above, by using the apparatus of the first embodiment, it is possible to mold an injection foam molded article by using various molding methods, and each of these molding methods will be specifically described below.

First, the first molding method will be described.
In a high-pressure mold closed state in which the movable mold 106 and the fixed mold 110 are brought into contact with each other at a high pressure, a resin containing a foaming agent is injected into the mold cavity 111.

After the injection is completed, the mold opening operation is started.
The mold opening speed at this time is a constant speed or a gradient speed capable of maintaining contact with the mold wall surface due to expansion of the resin by the foaming gas. In the present invention, "injection completed" refers to a point in time when the foamed resin fills the cavity in the injection step.

When the mold opening progresses and the movable mold 106 reaches the arbitrarily set reference thickness position, the movable mold 106 is stopped at this position. Then, cooling is started in this state.

After the cooling is completed, the movable mold 106 is moved backward to take out the product. Thereafter, the above-described operation is repeated to sequentially perform the molding of the injection foam molded article.

Next, the second molding method will be described.
In the high-pressure mold closed state, the resin containing the foaming agent is injected into the mold cavity 111, and after the injection is completed, the mold opening operation is started. At this time, the mold opening speed is a constant speed or a gradient speed capable of maintaining the contact with the mold wall surface due to expansion of the resin by the foaming gas.

When the mold opening progresses and the movable mold 106 reaches the position exceeding the arbitrarily set reference thickness, the movable mold 106 is moved forward from that position and compressed to the reference thickness position. Then, cooling is started in that state.

After the cooling is completed, the movable mold 106 is moved backward to take out the product. Thereafter, the above-described operation is repeated to sequentially perform the molding of the injection foam molded article.

Next, the third molding method will be described.
In a low pressure mold closed state in which the movable mold 106 and the fixed mold 110 are in contact with each other at a low pressure, or in a tilt pressure mold closed state, a resin containing a foaming agent is injected into the mold cavity 111. individually,
The inclined pressure type closed state is a mold closed state due to the pressure during switching from the high pressure / low pressure type closed state to the low pressure / high pressure type closed state.

Immediately after the start of the injection step, mold opening is started based on the screw position or the injection time. The mold opening speed at this time is
A constant speed or a gradient speed capable of maintaining contact with the mold wall surface due to expansion of the resin by the foaming gas.

The movable mold 106 is moved to an arbitrarily set reference thickness position before the injection is completed, and stopped at this position. Then, cooling is started in that state.

After the cooling is completed, the movable mold 106 is retracted to take out the product. Thereafter, the above-described operation is repeated to sequentially perform the molding of the injection foam molded article.

Next, the fourth molding method will be described.
In a mold closed state at a low pressure or a gradient pressure, a resin containing a foaming agent is injected into the mold cavity 111, and the mold opening is started at the screw position or the injection time immediately after the start of the injection process.
The mold opening speed at this time is a constant speed or a gradient speed capable of maintaining contact with the mold wall surface due to expansion of the resin by the foaming gas.

The movable mold 106 is moved to a predetermined reference thickness excess position before the injection is completed, and when the movable mold 106 reaches the reference thickness excess position, the movable mold 106 is advanced from that position.
Apply compression to the reference thickness position. Then, cooling is started in that state.

After the cooling is completed, the movable mold 106 is moved backward to take out the product. Thereafter, the above-described operation is repeated to sequentially perform the molding of the injection foam molded article.

Next, a fifth forming method will be described.
In a mold opening state in which the mold is slightly open at a low pressure or a gradient pressure, that is, in a mold opening state in which the movable mold 106 is located between the mold closing position and the reference thickness position, the resin containing a foaming agent is injected into the mold cavity 111 and injected. Immediately after the start of the process, mold opening is started at the screw position or the injection time. The mold opening speed at this time is a constant speed or a gradient speed capable of maintaining contact with the mold wall surface due to expansion of the resin by the foaming gas.

The movable die 106 is moved to a preset reference thickness position before the injection is completed, and is stopped at that position.
Then, cooling is started in that state.

After the cooling is completed, the movable mold 106 is retracted to take out the product. Thereafter, the above-described operation is repeated to sequentially perform the molding of the injection foam molded article.

Next, the sixth molding method will be described.
In a mold opening state with a low pressure or an inclined pressure, the resin containing a foaming agent is injected into the mold cavity 111, and immediately after the injection process starts, the mold opening is started at the screw position or the injection time.
The mold opening speed at this time is a constant speed or a gradient speed capable of maintaining contact with the mold wall surface due to expansion of the resin by the foaming gas.

The movable die 106 is moved to a predetermined reference thickness excess position before the injection is completed, and when the movable die 106 reaches the reference thickness excess position, the movable die 106 is advanced from that position.
Apply compression to the reference thickness position. Then, cooling is started in that state.

After the cooling is completed, the movable mold 106 is moved backward to take out the product. Thereafter, the above-described operation is repeated to sequentially perform the molding of the injection foam molded article.

As described above, each of the above molding methods is
Since the mold opening speed at the time of mold opening is maintained at a speed that can maintain contact with the mold wall due to expansion of the resin by the foaming gas,
It is possible to obtain a molded product having a small and uniform foam cell, a high foaming rate and a high elasticity.

FIG. 10 shows a second embodiment of the present invention, wherein the molding method is used in combination with a counterpressure molding method.

That is, in the counter pressure molding method, a nitrogen gas or the like is injected into a mold cavity, and a resin containing a foaming agent is injected into the mold cavity at a high speed. For example, Japanese Unexamined Patent Publication (Kokai) No. 61-239917 discloses a molding method for injecting a gas into a mold cavity and injecting a molten resin under a pressurized state to foam-inject molding. Have been.

The basic steps of this counter pressure molding method are as follows. 1. A step of injecting nitrogen gas or the like into the mold. 2. Injecting and filling the molten resin. 3. Process to suppress foaming with nitrogen gas etc. 4. A step in which the molten resin comes into contact with the mold to form a skin layer (skin layer). 5. A step of discharging nitrogen gas or the like after the skin layer is formed. 6. A step of foaming the inside of a molded article.

The counter pressure molding method is to obtain a product having a smooth surface and an internal foam through the above steps. An apparatus configuration for implementing the method will be described below with reference to FIG.

In FIG. 10, reference numeral 750 denotes nitrogen gas or the like from a gas generator (not shown).
This is a switching valve for sealing the inside of the chamber 1, and the pressure of this gas is set to about 5 to ²⁰ kg / cm ² . For adjusting the pressure of nitrogen gas or the like, a pressure adjusting valve 751 such as an electromagnetic proportional valve
Is provided branched from the discharge-side gas pipe, and a drain valve 752 is provided in the discharge-side gas pipe. Also,
On the supply gas line side, a gas pressure detector 753 and a gas pressure setting device (not shown) branched from the gas line are provided.

In other respects, the configuration is the same as that of the first embodiment, and the operation is the same.

Next, a molding method combining the counter pressure molding method and the molding method of the first embodiment will be described.

First, the first molding method will be described.
In a high-pressure mold closed state in which the movable mold 106 and the fixed mold 110 are brought into contact with each other at a high pressure, nitrogen gas or the like is sealed in the mold cavity, and then the resin containing a foaming agent is injected into the mold cavity 111.

After the injection is completed, nitrogen gas or the like is discharged, and the mold opening operation is started. The mold opening speed at this time is a constant speed or a gradient speed capable of maintaining contact with the mold wall surface due to expansion of the resin by the foaming gas.

When the mold opening advances and the movable mold 106 reaches the arbitrarily set reference thickness position, the movable mold 106 is stopped at this position. Then, cooling is started in this state.

After the cooling is completed, the movable mold 106 is moved backward to take out the product. Thereafter, the above-described operation is repeated to sequentially mold the molded product.

Next, the second molding method will be described.
In the high-pressure mold closed state, nitrogen gas or the like is sealed in the mold cavity 111, and then the resin containing a foaming agent is injected into the mold cavity 111.

After the injection is completed, nitrogen gas or the like is discharged, and the mold opening operation is started. The mold opening speed at this time is a constant speed or a gradient speed capable of maintaining contact with the mold wall surface due to expansion of the resin by the foaming gas.

When the mold opening progresses and the movable mold 106 reaches a position exceeding the arbitrarily set reference thickness, the movable mold 106 is moved forward from that position and compressed to the reference thickness position. Then, cooling is started in that state.

After the cooling is completed, the movable mold 106 is moved backward to take out the product. Thereafter, the above-described operation is repeated to sequentially mold the molded product.

Next, the third molding method will be described.
In a mold closed state at a low pressure or a gradient pressure, nitrogen gas or the like is sealed in the mold cavity 111, and then a resin containing a foaming agent is injected into the mold cavity 111 to form a skin layer.

Immediately after the start of the injection step, nitrogen gas and the like are discharged, and opening of the mold is started according to the screw position or the injection time. The mold opening speed at this time is a constant speed or a gradient speed capable of maintaining contact with the mold wall surface due to expansion of the resin by the foaming gas.

The movable die 106 is moved to an arbitrarily set reference thickness position before the injection is completed and stopped at this position. Then, cooling is started in that state.

After the cooling is completed, the movable mold 106 is moved backward to take out the product. Thereafter, the above-described operation is repeated to sequentially mold the molded product.

Next, the fourth molding method will be described.
In a mold closed state at a low pressure or a gradient pressure, nitrogen gas or the like is sealed in the mold cavity 111, and then a resin containing a foaming agent is injected into the mold cavity 111 to form a skin layer.

Immediately after the start of the injection step, nitrogen gas and the like are discharged, and mold opening is started according to the screw position or the injection time. The mold opening speed at this time is a constant speed or a gradient speed capable of maintaining contact with the mold wall surface due to expansion of the resin by the foaming gas.

The movable mold 106 is moved to a predetermined reference thickness excess position before the injection is completed, and when the movable mold 106 reaches the reference thickness excess position, the movable mold 106 is advanced from that position.
Apply compression to the reference thickness position. And it cools in that state.

After the cooling is completed, the movable mold 106 is moved backward to take out the product. Thereafter, the above-described operation is repeated to sequentially mold the molded product.

Next, a fifth forming method will be described.
In a state where the mold is opened at a low pressure or an inclined pressure, nitrogen gas or the like is sealed in the mold cavity 111, and then a resin containing a foaming agent is injected into the mold cavity 111 to form a skin layer.

Immediately after the start of the injection step, nitrogen gas and the like are discharged, and the mold opening is started according to the screw position or the injection time. The mold opening speed at this time is a constant speed or a gradient speed capable of maintaining contact with the mold wall surface due to expansion of the resin by the foaming gas.

The movable mold 106 is moved to a preset reference thickness position before the injection is completed and stopped at that position.
Then, cooling is started in that state.

After cooling, the movable mold 106 is moved backward to take out the product. Thereafter, the above-described operation is repeated to sequentially mold the molded product.

Next, the sixth molding method will be described.
In a state where the mold is opened at a low pressure or an inclined pressure, nitrogen gas or the like is sealed in the mold cavity 111, and then a resin containing a foaming agent is injected into the mold cavity 111 to form a skin layer.

Immediately after the start of the injection step, nitrogen gas and the like are discharged, and mold opening is started based on the screw position or the injection time. The mold opening speed at this time is a constant speed or a gradient speed capable of maintaining contact with the mold wall surface due to expansion of the resin by the foaming gas.

The movable mold 106 is moved to a predetermined reference thickness excess position before the injection is completed, and when the movable mold 106 reaches the reference thickness excess position, the movable mold 106 is advanced from that position.
Apply compression to the reference thickness position. Then, cooling is started in that state.

After cooling is completed, the movable mold 106 is retracted to take out the product. Thereafter, the above-described operation is repeated to sequentially mold the molded product.

As described above, since the molding method of the first embodiment is combined with the counter pressure molding method, when foaming inside the molded article, the foaming cell is formed into a true sphere by precisely controlling the foaming speed. it can.

Although not particularly described in each of the molding methods, the mold cavity 11 is closed after the mold is completely closed.
The injection may be started when the gas pressure in 1 reaches a preset pressure. Thus, molding can be always performed at a constant and accurate pressure. Further, the gas pressure may be arbitrarily changed according to the filling state. Further, the evacuation may be performed at a certain timing at the end of molding. This makes it possible to more effectively prevent the surface skin layer from being roughened.

FIG. 11 to FIG. 14 show a third embodiment of the present invention, in which the molding method of the first embodiment is used in combination with a two-layer molding method.

That is, the two-layer molding method is a molding method in which two layers of the foam molding layer side and the non-foam molding layer side are molded simultaneously. This two-layer molding method is described in, for example, Japanese Patent Publication No. 4-26290. No. 6,086,045.

In FIG. 11, reference numeral 801 denotes a molding machine. The molding machine 801 includes a movable plate 8 that can move up and down along a support frame 815 fixed to a fixed support plate 805.
The movable plate 817 is driven to move up and down by a hydraulic cylinder 823.

On the front side of the movable plate 817, a first female die 819 and a second female die 821 are fixed vertically, and one male die attached to the movable support plate 807 is provided in front of these. 825 are located. And each female mold 81
9, 821, one of which faces the male mold 825 by moving up and down the movable plate 817.

On the back side of the fixed side support board 805, FIG.
As shown in the figure, a first injection device 813 is provided, and above the two molds 819, 821, 825,
As shown in FIG. 14, a second injection device 827 is provided so as to enable injection from the parting surface 821a.

The remaining configuration is the same as that of the first embodiment, and the operation is the same.

Next, a description will be given of a molding method in which the molding method of the first embodiment and the two-layer molding method are combined.

First, the first molding method will be described.
In the high-pressure mold closed state, non-foamed resin is injected into the cavity formed by the first female mold 819 and the male mold 825 to perform the first injection operation.

After the injection and subsequent cooling are completed, the male mold 82
With the primary molded product still attached to 5, the male mold 825 is retracted to the retreat limit to open the mold.

Next, the movable plate 817 is raised to make the second female mold 821 face the male mold 825, and then the male mold 825 is advanced to make the male mold 825 with the second female mold 821 and the primary molded product attached. And constitute a cavity.

Next, the resin containing the foaming agent is injected into the cavity in the high-pressure mold closed state to perform the second injection operation. Then, after the injection is completed, the mold opening operation is started. The mold opening speed at this time is a constant speed or a gradient speed capable of maintaining contact with the mold wall surface due to expansion of the resin by the foaming gas.

When the mold opening proceeds and the male mold 825 reaches the arbitrarily set reference thickness position, the male mold 825 is stopped at this position. Then, cooling is started in that state.

After the cooling is completed, the male mold 825 is retracted to take out the product. Thereafter, the above-described operation is repeated to sequentially mold the molded product.

Next, the second molding method will be described.
In the high-pressure mold closed state, non-foamed resin is injected into the cavity formed by the first female mold 819 and the male mold 825 to perform the first injection operation.

After the injection and subsequent cooling, the male mold 825 is retracted to the retreat limit and the mold is opened while the primary molded product is still attached to the male mold 825.

Next, the movable plate 817 is raised to make the second female die 821 face the male die 825, and then the male die 825 is advanced to move the male die 825 with the second female die 821 and the primary molded product attached thereto. And constitute a cavity.

Then, a resin containing a foaming agent is injected into the cavity in the high-pressure mold closed state to perform a second injection operation. Then, after the injection is completed, the mold opening operation is started. The mold opening speed at this time is a constant speed or a gradient speed capable of maintaining contact with the mold wall surface due to expansion of the resin by the foaming gas.

When the opening of the mold proceeds and the male mold 825 reaches a position exceeding the arbitrarily set reference thickness, the male mold 825 is moved forward from that position and compressed to the reference thickness position. Then, cooling is started in that state.

After the cooling is completed, the male mold 825 is retracted to take out the product. Thereafter, the above-described operation is repeated to sequentially mold the molded product.

Next, the third molding method will be described.
In the high-pressure mold closed state, non-foamed resin is injected into the cavity formed by the first female mold 819 and the male mold 825 to perform the first injection operation.

After completion of the injection and the subsequent cooling, the male mold 82
With the primary molded product still attached to 5, the male mold 825 is retracted to the retreat limit to open the mold.

Next, the movable plate 817 is raised to make the second female mold 821 face the male mold 825, and then the male mold 825 is advanced to make the male mold 825 with the second female mold 821 and the primary molded product attached. And constitute a cavity.

Next, in a mold closed state of low pressure or gradient pressure,
A second injection operation is performed by injecting a resin containing a foaming agent into the cavity. Immediately after the start of the injection process, mold opening is started based on the screw position or the injection time. The mold opening speed at this time is a constant speed or a gradient speed capable of maintaining contact with the mold wall surface due to expansion of the resin by the foaming gas.

The male mold 825 is moved to an arbitrarily set reference thickness position before the injection is completed and stopped at this position.
Then, cooling is started in that state.

After the cooling is completed, the male mold 825 is retracted to take out the product. Thereafter, the above-described operation is repeated to sequentially mold the molded product.

Next, the fourth molding method will be described. In the high-pressure mold closed state, non-foamed resin is injected into the cavity formed by the first female mold 819 and the male mold 825 to perform the first injection operation.

After completion of the injection and the subsequent cooling, the male mold 82
With the primary molded product still attached to 5, the male mold 825 is retracted to the retreat limit to open the mold.

Next, the movable plate 817 is raised to make the second female mold 821 face the male mold 825, and then the male mold 825 is advanced to make the male mold 825 with the second female mold 821 and the primary molded product attached. And constitute a cavity.

Next, in a mold closed state of low pressure or gradient pressure,
A second injection operation is performed by injecting a resin containing a foaming agent into the cavity. Immediately after the start of the injection process, mold opening is started based on the screw position or the injection time. The mold opening speed at this time is a constant speed or a gradient speed capable of maintaining contact with the mold wall surface due to expansion of the resin by the foaming gas.

The male mold 825 is moved to an arbitrarily set reference thickness position before the injection is completed. When the male mold 825 reaches the reference thickness position, the male mold 825 is advanced from that position to the reference thickness position. Apply compression. Then, cooling is started in that state.

After the cooling is completed, the male mold 825 is retracted to take out the product. Thereafter, the above-described operation is repeated to sequentially mold the molded product.

Next, a fifth forming method will be described.
In the high-pressure mold closed state, non-foamed resin is injected into the cavity formed by the first female mold 819 and the male mold 825 to perform the first injection operation.

After completion of the injection and the subsequent cooling, the male mold 82
With the primary molded product still attached to 5, the male mold 825 is retracted to the retreat limit to open the mold.

Next, the movable plate 817 is raised to make the second female die 821 face the male die 825, and then the male die 825 is advanced to move the male die 825 with the second female die 821 and the primary molded product. And constitute a cavity.

Next, the resin containing the foaming agent is injected into the cavity with the mold opened at a low pressure or a low pressure to perform a second injection operation. Immediately after the start of the injection process, mold opening is started based on the screw position or the injection time. The mold opening speed at this time is a constant speed or a gradient speed capable of maintaining contact with the mold wall surface due to expansion of the resin by the foaming gas.

The male mold 825 is moved to a preset reference thickness position by the time the injection is completed, and stopped at that position. Then, cooling is started in that state.

After the cooling is completed, the male mold 825 is retracted to take out the product. Thereafter, the above-described operation is repeated to sequentially mold the molded product.

Next, the sixth molding method will be described.
In the high-pressure mold closed state, non-foamed resin is injected into the cavity formed by the first female mold 819 and the male mold 825 to perform the first injection operation.

After the injection and the subsequent cooling, the male mold 82
With the primary molded product still attached to 5, the male mold 825 is retracted to the retreat limit to open the mold.

Next, the movable plate 817 is raised to make the second female die 821 face the male die 825, and then the male die 825 is advanced to move the male die 825 with the second female die 821 and the primary molded product. And constitute a cavity.

Next, the resin containing the foaming agent is injected into the cavity while the mold is being opened at a low pressure or a low gradient pressure to perform a second injection operation. Immediately after the start of the injection process, mold opening is started based on the screw position or the injection time. The mold opening speed at this time is a constant speed or a gradient speed capable of maintaining contact with the mold wall surface due to expansion of the resin by the foaming gas.

The male mold 825 is moved to a pre-set reference thickness position before the injection is completed, and when it reaches the reference thickness position, the male mold 825 is advanced from that position to reach the reference thickness position. Apply compression. Then, cooling is started in that state.

After the cooling is completed, the male mold 825 is retracted to take out the product. Thereafter, the above-described operation is repeated to sequentially mold the molded product.

As described above, since the molding method of the first embodiment is combined with the two-layer molding method, the two-layer molding method can be brought closer to the actual use of the molded article, and the subsequent steps such as laminating can be performed. There is a merit that can be omitted. Further, if the molding incorporates the counter pressure molding method, further effects can be obtained.

Although the above description is based on the example of the movement of the entire surface perpendicular to the moving axis direction of the movable die, the movable die to be moved in the molding method of the present invention does not necessarily mean the movement of the entire surface. However, the present invention is not limited to this, and includes the case of partial movement of the surface.

[0150]

As described above, according to the present invention, after the injection of the resin containing the foaming agent is completed, the mold opening is started to foam the molded article, and the mold opening speed at that time is controlled by the foaming gas. The expansion rate is such that the contact with the mold wall can be maintained, so that the foaming speed can be controlled accurately, and it is possible to obtain a molded product with small and uniform foam cells, high foaming rate and high elasticity. it can.

Further, by performing the movement of the movable mold immediately after the start of injection, it is possible to obtain a higher foaming ratio and a better surface appearance than a molded product obtained by performing the injection after completion of the injection. By injecting the resin in the open state, the foaming ratio is higher and the surface appearance can be more excellent than that obtained by injecting the resin in the mold closed state.

Further, the movable mold is stopped at a position exceeding the predetermined reference thickness, and then the movable mold is advanced from the position exceeding the reference thickness and compressed to the reference thickness position, thereby improving the uniformity of foaming. Can be improved.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing an injection molding apparatus according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing details of a mold opening timing control unit.

FIG. 3 is a configuration diagram showing details of a mold opening speed control unit.

FIG. 4 is a graph showing a change in speed at the time of an enlargement step by the control unit in FIG. 3;

FIG. 5 is a configuration diagram showing details of a mold opening speed control unit different from FIG. 3;

FIG. 6 is a graph showing a speed change at the time of an enlargement step by the control unit in FIG. 5;

FIG. 7 is a configuration diagram showing details of a compression timing control unit.

FIG. 8 is a configuration diagram showing details of a compression control unit.

FIG. 9 is a graph showing a pressure change during a compression step by the control unit in FIG. 8;

FIG. 10 is a configuration diagram of a molding apparatus according to a second embodiment of the present invention.

FIG. 11 is a configuration diagram of a molding apparatus showing a third embodiment of the present invention.

FIG. 12 is an explanatory view showing a state in which a cavity is formed by a male mold and a first female mold.

FIG. 13 is an explanatory view showing a state in which a cavity is formed by a male mold and a second female mold.

FIG. 14 is an explanatory view showing a state where two layers are formed.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 injection molding apparatus 101 injection molding machine 102 screw 105 heating cylinder 106 movable mold 110 fixed mold 111 mold cavity 350 mold clamping cylinder

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Shingo Nakayasu 1-8-3, Terabe-dori, Minami-ku, Nagoya-shi, Aichi Pref. Toshiba Machine Plastic Engineering Nagoya Office (72) Inventor Yoshiyoshi Kato Beauty 1-8-3, Terabe-dori, Minami-ku, Nagoya-shi, Aichi Prefecture Toshiba Machine Plastic Engineering Nagoya Sales Office (56) References JP-A-58-134720 (JP, A) JP-A-4-214311 ( JP, A) JP-A-6-198668 (JP, A) JP-B-48-20023 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 45/00-45/70 B29K 105: 04 B29L 31:58

Claims (4)

(57) [Claims] 1. A resin containing a foaming agent is injected into a cavity in a mold closed state of an injection molding machine. Immediately after the injection step is started, the movable mold is moved while maintaining contact with a mold wall surface by expansion of the resin by a foaming gas. A method for molding an injection-foamed product, comprising: stopping the movable mold at a predetermined reference thickness position before the injection is completed, and retracting the movable mold to take out the product after the completion of cooling. 2. A resin containing a foaming agent is injected into the cavity while the mold of the injection molding machine is closed. Immediately after the start of the injection process, the movable mold is moved while maintaining contact with the mold wall surface by expansion of the resin by the foaming gas. By the completion of the injection, the movable mold is stopped at a preset reference thickness excess position, and then the movable mold is advanced from the reference thickness excess position and compressed to the reference thickness position,
A method for molding an injection-foamed molded product, comprising removing a product by retracting a movable mold after cooling is completed. 3. A resin containing a foaming agent is injected into the cavity while the movable mold is moved to a desired position between the mold closing position and the reference thickness position of the injection molding machine, and the injection process is started. Immediately after, the movable mold is moved at a speed corresponding to the foaming speed of the foaming agent to start opening the mold, and by the completion of injection, the movable mold is stopped at a preset reference thickness position, and after the cooling is completed, the movable mold is moved. A method for molding an injection-foamed molded product, comprising retreating and removing a product. 4. A resin containing a foaming agent is injected into the cavity with the movable mold moved to a desired position between the mold closed position and the reference thickness position of the injection molding machine, and the injection process is started. Immediately after, the movable mold is moved while maintaining contact with the mold wall surface by expansion of the resin by the foaming gas, and by the completion of injection, the movable mold is stopped at a position exceeding a preset reference thickness, and then the reference thickness is determined. A method of molding an injection-foamed molded product, comprising moving a movable mold forward from a super position, compressing the movable mold to a reference thickness position, and after cooling, retracting the movable mold to take out a product.