JPH0655389B2 - Injection molding method for sandwich molded article and its injection molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention provides a method for injection molding a sandwich molded article, in which a molten synthetic resin for forming a skin layer and a core layer is injected from an injection head to obtain a sandwich molded article. And its injection molding machine.

[Prior Art] Conventionally, in an injection molding machine of this type, an injection head of a twin-screw injection molding machine including two injection units is as follows.
The items (a) and (b) are known.

(B) The inner nozzle, which is concentrically arranged in the outer nozzle and is slidable in the axial direction thereof, is rotatable by the rotating means, and the resin passage is opened and closed by the rotation of the inner nozzle, and the inner nozzle is also rotated. An operating rod that opens and closes the nozzle hole of the inner nozzle is provided therein (see Japanese Patent Laid-Open No. 59-220341).

(B) An annular insert concentrically arranged in the injection head is provided slidably in the axial direction, and a needle having a connection passage is rotatably provided in the annular insert, and the needle is rotated to rotate the needle. A structure in which a gas can be supplied by opening and closing the connecting passage (Japanese Patent Laid-Open No. Sho 63-63).
-94805).

Further, as another injection molding machine, (c) a manifold block having a multi-passage nozzle is provided with resin passages that are connected to the multi-passage nozzles and are the same number as a plurality of injection heads and injection rams. Two manifold valves are provided, and the operation of each injection ram is controlled by the opening / closing of each manifold valve and the microprocessor to control the opening / closing of a plurality of resin passages to obtain a multi-layer molded product. Yes (Japanese Patent Laid-Open No. 63-9991)
No. 8).

[Problems to be Solved by the Invention] However, in the above conventional techniques, in both cases (a) and (b), the opening / closing mechanism of the nozzle hole is complicated and a plurality of drive devices are provided. Therefore, the control of opening and closing the nozzle hole becomes complicated, and it is difficult to control the flow rate of the molten synthetic resin flowing out to the nozzle hole, and a stable skin layer cannot be formed. Since the cylinder (or annular insert) is slid,
There is a problem that it is difficult in terms of strength to make the diameter of the injection head too small while causing stringing of the molten resin from the nozzle hole for each shot.

On the other hand, in the case of (c), the control of the opening and closing of the multi-passage nozzle is complicated, making it difficult to adjust the timing between the opening and closing of the multi-passage nozzle and the operation of each injection head or the injection ram, and the melt flowing out to the multi-passage nozzle Since the flow rate control of the synthetic resin is performed by fully opening and closing each resin passage and changing the speed of the injection head or the injection ram, it is not possible to finely change the relative proportion of both injection in each resin passage, Therefore, a uniform skin layer cannot be formed, and it is difficult to form a molded product having a complicated shape. Also, for molded products with different injection amounts or injection ratios, manifold blocks with different flow channel shapes, flow channel cross-sectional areas, flow channel cross-sectional area ratios, etc. must be exchanged for each molded product. There is a problem that the work is complicated.

The present invention has been made in view of the problems of the above-mentioned conventional techniques, and despite having a simple structure, it is possible to form a stable skin layer and prevent stringing for each shot. An object of the present invention is to provide an injection molding method of a sandwich molded product and an injection molding machine thereof which are capable of opening / closing the inner passage and the outer passage and easily adjusting the timing of opening / closing each passage and operating the injection unit.

[Means for Solving the Problems] In order to achieve the above object, in a method for injection molding a sandwich molded article of the present invention, an injection head main body is connected to a first injection unit and a second injection unit, and An outer passage is formed by inserting a valve housing into the valve housing, and an inner passage is formed by inserting a shaft having an inner torpedo having a front seal surface and a rear seal portion fixed to the front end into the valve housing. Using the injection molding machine equipped with the injection head, the inner torpedo, which was previously in the most advanced position, is retracted to the predetermined retracted position via the shaft to open only the outer passage and form the skin layer. The molten synthetic resin for injection is injected from the outer passage into the closed mold, and then the inner torpedo is placed through the shaft. By advancing to a fixed intermediate position, both the outer passage and the inner passage are opened, and molten synthetic resins for forming the skin layer and the core layer are injected into the mold from the outer passage and the inner passage, respectively, and then the shaft is opened. The inner torpedo is retracted to a predetermined retracted position to close the inner passage, and the molten synthetic resin is injected into the mold from the outer passage to form a skin layer, and then the molten synthetic resin filled in the mold. It is characterized by exerting a holding pressure on.

The following are injection molding machines used directly for carrying out the above injection molding method.

An injection head main body is connected to a first injection unit and a second injection unit each having a first screw and a second screw, and an outer passage is formed by fitting a valve housing into the injection head main body, and at the same time, a valve housing. An injection head in which an inner passage is formed by inserting a shaft having an inner torpedo having a leading end sealing surface and a trailing end sealing portion fixed to the leading end,
An inner torpedo driving device having a control unit for reciprocating the inner torpedo in the axial direction is connected to the shaft, and the axial movement positions of the first screw, the second screw and the inner torpedo are detected. First to do
A position detector, a second position detector, and a third position detector are provided, and a detection value signal of the first position detector is input,
When the detected value signal matches the preset first set value, the inner torpedo is moved to a predetermined retracted position through the control unit, and the detected value signal matches the preset second set value And a control device for moving the inner torpedo to a predetermined intermediate position via the control section and for moving the second screw forward to a predetermined position via a screw reciprocating drive device of the second injection unit, and When the detection value signal of the second position detector is input and the detection value signal coincides with a preset setting value, the inner torpedo is moved to a predetermined retracted position via the control unit and the first injection unit The second injection unit is provided with a control device for advancing the first screw via the screw reciprocating drive device, while the detection value signal of the third position detector is input. Detected value signal preset predetermined retracted position, provided with the predetermined intermediate position and the inner torpedo control apparatus for feedback control of the control unit so that the setting values corresponding to a predetermined retracted position.

Further, the inner torpedo drive device includes a piston fixed to the other end of the shaft, a fluid pressure cylinder of the piston, and a fluid pressure generation source connected to the fluid pressure cylinder via a directional switching valve at three positions. , A control unit for controlling switching of the directional control valve.

The inner torpedo drive device includes a sliding body fixed to the other end of the shaft, a guide tube of the sliding conductor, a screw member having one end screwed to the sliding body, and an output shaft having the screw member. And an electric motor that is connected to the other end of the electric motor and is capable of normal and reverse rotation, and a control unit that controls switching between normal and reverse rotation of the electric motor.

Further, the inner torpedo drive device is a rack fixed to the other end of the shaft so as to extend in the axial direction of the shaft, and a forward-reverse rotatable electric motor having an output shaft fixed to a pinion meshing with the rack, And a control unit for controlling switching between forward and reverse rotations of the electric motor.

Further, a pilot check valve is arranged in the path between the fluid pressure cylinder and the direction switching valve.

Further, the injection head body can be disassembled into a plurality of parts.

[Operation] In the injection molding method and the injection molding machine of the present invention, when starting the injection molding, first, the inner torpedo is advanced to the most advanced position, and the inner passage and the outer passage are closed by the tip sealing surface thereof. To do. Next, by retracting the inner torpedo to a predetermined retracted position, the inner passage is closed and the outer passage is opened, and a molten synthetic resin forming a skin layer is partially pressed into the outer passage from the first injection unit to clamp the mold. It is injected into the mold. Then, the inner passage is opened by advancing the inner torpedo to a predetermined intermediate position, and the molten synthetic resin forming the core layer is pressed into the inner passage from the second injection unit. The core layer is completely wrapped into the layered flow, and the molten synthetic resin flowing out from both passages is injected into the mold while the flow rate is adjusted. Then, the inner torpedo is retracted to a predetermined retracted position, and only the molten synthetic resin for forming the skin layer is injected into the mold from the first injection unit to cover the sprue of the mold and its vicinity. After forming the layers, the first injection unit applies a holding pressure to the molten synthetic resin in the mold.

[Embodiment] Next, an embodiment of the present invention will be described with reference to the drawings.

(First Embodiment) As shown in FIGS. 1, 2, and 3 (A), (B), and (C), a screw reciprocating drive device 2 for reciprocating the first screw 1 _1.
7a, the second screw reciprocating drive device 27b for the screw _{2 1} is reciprocated, first injection with first plasticizing drive 29a for rotating the screw _{1 1,} the plasticizing driving device 29b for rotating the second screw _{2 1} each The unit 1 and the second injection unit 2 are arranged side by side on a moving base (not shown), and the first screw 1 ₁ and the second screw 2 ₁ respectively have pistons at their ends which are slidable in the cylinders 30c and 30d. 30a and 30b are fixed. The ejection units 1 and 2 have heads 1a and 2a, respectively.

On the other hand, the T-shaped ejection head body 5 which is the ejection head body,
It is composed of a base portion 5a having connecting portions 3 and 4 projecting from both sides and a tip portion 5b which is removably coupled to the base portion 5a with a bolt or the like (not shown). A nozzle tip 6 having a conical hole 6b and a nozzle hole 6a communicating with the conical hole 6b is detachably fixed. Then, one connecting portion 3 is connected to the head 1 a of the first ejection unit 1, and the other connecting portion 4 is connected to the head 2 a of the second ejection unit 2. The nozzle tip 6 described above is located at a position where the nozzle hole 6a communicates with a cavity 37d of a die including an upper die 37a and a lower die 37b fixed to the die plates 36a and 36b, respectively. In the present embodiment, the injection head main body has a T shape, but the present invention is not limited to this and may have various shapes.

An annular outer torpedo 7 is fitted to the tip end portion of the T-shaped injection head main body 5, and a cylindrical valve concentrically arranged in the T-shaped injection head main body 5 at the rear end thereof. An outer passage 12 is formed between the inner peripheral surface of the T-shaped injection head body 5 and the outer peripheral surface of the valve housing 11 by connecting the housing 11. Further, a shaft 9 reciprocated by a piston 10a provided inside a hydraulic cylinder 10 attached to a rear end portion or the like is inserted into the valve housing 11, and the shaft 9 is reciprocally moved between them, that is, an inner peripheral surface of the valve housing 11. An inner passage 13 is formed between the outer peripheral surface of the shaft 9 and the outer peripheral surface of the shaft 9. An inner torpedo 8 is fixed to the tip of the shaft 9, and the inner torpedo 8 is guided by the large-diameter portion 7b of the inner peripheral surface of the outer torpedo 7 and reciprocated in the axial direction via the shaft 9. ,
The boss portion 8a is provided with a leading end sealing surface 8b and a trailing end sealing portion 8c. When the rear end seal portion 8c is inserted into the inner passage 13, the inner passage 13 is closed. The T-shaped injection head main body 5, the nozzle tip 6, the outer torpedo 7, the inner torpedo 8, the shaft 9 and the valve housing 11 constitute a T-shaped injection head.
On the other hand, the hydraulic cylinder 10 includes check valves 25a and 25b with variable throttles and pilot check valves 26a and 26b.
And 4 with _two electromagnetic solenoids 24 ₁ , 242
A hydraulic pressure generation source 25 via the direction switching valve 24 at the port 3 position
The hydraulic pressure generation source 25 includes a hydraulic tank 19, a hydraulic pump 20, an electric motor 21 for operating the hydraulic pump 20, a relief valve 22, and a hydraulic pressure gauge 23.

Then, the control unit 35a switches the directional control valve 24 and the electromagnetic solenoid ₂₄ 1, 24 ₂ of directional control valve 24 energized or de-energized state. The control unit 35a, the piston 10a, the hydraulic cylinder 10, the check valves with variable throttles 25a and 25b, the pilot check valves 26a and 26 described above.
The inner torpedo drive device 18a is configured by b, the directional control valve 24, and the hydraulic pressure generation source 25.

Further, as shown in FIG. 2, the above-described outer torpedo 7 has a plurality of through holes 7a penetrating in the axial direction, which are formed at intervals in the circumferential direction, and through the through holes 7a. The outer passage 12 and the nozzle hole 6a are communicated with each other, while the inner torpedo 8 has a plurality of through holes 8d formed at intervals in the circumferential direction and penetrating in the axial direction.
The inner passage 13 and the nozzle hole 6a communicate with each other via d.

Instead of providing the large-diameter portion 7b on the inner peripheral surface of the outer torpedo 7 described above, the inner peripheral surface of the outer torpedo 7 has a large diameter over its entire length, and the rear end seal portion 8c of the inner torpedo 8 is formed.
It is also possible to form an annular projecting portion for sealing, which is abutted against, on the inner peripheral surface thereof to close the inner passage 13. Further, the cross-sectional shape of the through holes 7a and 8d of both torpedoes 7 and 8 is not limited to the circular shape shown in the drawing, but may be various shapes. Further, instead of the through hole 7a of the outer torpedo 7, a groove may be formed on the outer peripheral portion of the outer torpedo 7.

On the other hand, a first linear encoder 14, a second linear encoder 15, and a third linear encoder 16 which are respectively installed on the first screw 1 ₁ , the second screw 2 ₁ , and the piston 10a and detect the respective moving positions are provided. , The detection value signals detected by the linear encoders 14, 15 and 16 are respectively controlled by the control device 2 of the first injection unit 1.
8a, the control device 28b of the second injection unit 2, and the inner torpedo control device 17 are input.

In the control device 28a, first and second set values of the moving position of the piston 30a in the axial direction (direction of arrow B) are set in advance, and the detection value signal detected by the first linear encoder 14 is set to the first setting. when the count value matches the value, by outputting a signal to the control unit 35a, the control unit 35a is energized to the electromagnetic solenoid 24 _{and second} directional control valve 24, switching to flow pressure oil in a direction to retract the piston 10a, The inner torpedo 8 is retracted to the final retracted position. After this, when the detection value signal matches with the second setting value, by outputting a signal to the control unit 35a, the control unit 35a is energized to the electromagnetic solenoid 24 _1, pressure oil in a direction to advance the piston 10a is The flow is switched so that the inner torpedo 8 is advanced to a predetermined intermediate position and the second
By outputting a signal to the control device 28b of the injection unit 2, the control device 28b causes the screw reciprocating drive device 27b.
Actuating the to advance second screw 2 ₁ to a predetermined position, that is fully forward position.

On the other hand, when the set value of the movement position of the piston 30b in the axial direction is set in advance and the detection value signal detected by the second linear encoder 15 matches the set value, the control device 28b causes the control unit 35a to operate. by outputting a signal, switching by energizing the magnetic solenoid 24 _2, the inner torpedo 8 with retracts to the most retracted position, first
By outputting a signal to the control device 28a of the injection unit 1, the control device 28a causes the screw reciprocating drive device 27a.
Is operated to advance the first screw ₁₁ to the most advanced position.

The first and second set values in the control device 28a and the set values in the control device 28b are determined by the fluidity of the molten synthetic resin, the shape of the molded product, the injection amount ratio (material ratio), and can be changed. is there.

Then, the inner torpedo control device 17 inputs the detection value signal detected by the third linear encoder 16 and the positions corresponding to the final retracted position, the predetermined intermediate position, and the final retracted position of the piston 10a in advance. The setting unit 31 for setting the set value, the comparing unit 33 that outputs a signal to the output unit 34 when the detected value signal from the input unit 32 and the setting value of the setting unit 31 match, and the signal from the comparing unit 33. In response to this, a stop signal is output to the control unit 35a of the inner torpedo drive device 18a, and the directional control valve 2 is transmitted via the control unit 35a.
4 to an intermediate position, and feeds back the movement position of the piston 10a to the control unit 35a. The set value corresponding to the predetermined intermediate position of the inner torpedo 8 in the setting unit 31 is determined by the fluidity of the molten synthetic resin, the shape of the molded product or the material ratio, and can be changed.

Note that FIG. 3 (A) shows a state in which the inner torpedo 8 is located at the most advanced position and the outer passage 12 and the inner passage 13 are closed, and FIG. 3 (B) shows that the inner torpedo 8 is At a predetermined intermediate position, the outer passage 12 and the inner passage 13 are in the fully opened state. When the inner torpedo 8 is advanced by l ₃ from this state, the state shown in FIG.
_When retracted by ₂ , the rear end seal portion 8c comes into contact with the outer torpedo 7 to close the inner passage 13. From this state, the rear end seal portion 8c can be inserted into the inner passage 13 by further retracting the inner torpedo 8 by l ₁ shown in FIG. 3 (C).

Next, the operation of this embodiment will be described with reference to FIG.

When starting injection molding, first, the first injection unit 1
And control devices 28a, 28b of the second injection unit 2
From the output of the signal to the control unit 35a of the inner torpedo drive 18a, the control unit 35a by energizing the electromagnetic solenoid 24 ₁ of directional control valve 24 is switched to the direction of advancing the piston 10a to flow pressure oil, Piston 10a
By advancing the inner torpedo 8 through the shaft 9 to the most advanced position as shown in FIG. 3 (A), the tip sealing surface 8b is brought into contact with the nozzle tip 6, and the outer passage 12 and The inner passage 13 is closed. Each control device 28a, 28b is a plasticizing drive device 29.
By outputting a signal to a and 29b and rotating the first screw 1 ₁ and the second screw 2 ₁ , the synthetic resin in the first injection unit 1 and the second injection unit 2 is plasticized. Then, as shown in FIG. 4, the controller 28a actuates a screw reciprocating drive device 27a at time t _1, by advancing the first screw 1 ₁ from time t ₁ to time t _6, A molten synthetic resin for forming a skin layer is partially pressed into the outer passage 12. During this time, the movement position in the axial direction of the piston 30a is detected by the first linear encoder 14, first each detection value thereof at the time t _2, t ₄ is preset in the control unit 28a, a second set value The control device 28a matches the control unit 35.
directional switching valve 2 from time t ₂ to time t ₃ via a
4 by energizing the electromagnetic solenoid 24 _2, the piston 10a
Is switched so that the pressure oil flows in the direction of retreating, and the inner torpedo 8 is retracted to the set value set in the setting unit 31, that is, the last retracted position shown in FIG. 3 (C), and then at time t ₃ . the electromagnetic solenoid 24 ₂ deenergized, after between inner torpedo 8 until the time t ₄ is held in the state shown in FIG. 3 (C), during from time t ₄ to time t _6, the electromagnetic solenoid 24 ₁ By energizing the inner torpedo 8 to the set value set in the setting unit 31, that is, advancing to a predetermined intermediate position, and turning off the electromagnetic solenoid 24 ₁ at time t ₆ , the time t ₇ Until then, the inner torpedo 8 is held in the state of FIG. 3 (B). On the other hand, the moving position of the piston 30a detected by the first linear encoder 14 at time t ₄ coincides with the second set value which is previously set in the control unit 28a, the controller 28a will output a signal to the control unit 28b by, between the control unit 28b from time _{t 4} to time _{t 7,} by operating the screw reciprocating drive device 27b, advancing a second screw _{2 1} to the most advanced position during from time _{t 4} to time _{t 7} By letting
Molten synthetic resin for forming the core layer is press-fitted into the inner passage 13. As a result, part of the molten synthetic resin for forming the skin layer, between the time t ₂ to time t _5, clamping the molds 37a, is injected into 37b of the cavity 37d in, from time t ₅ Up to time t ₈ , both passages 12,
The molten synthetic resin flowing in each of 13 becomes a layered flow in which the core layer is completely wrapped with the skin layer inside the nozzle hole 6a, and is injected into the cavity 37d of both molds 37a and 37b. Moreover, by automatically moving the inner torpedo 8 to a predetermined intermediate position and holding it at that position, the flow rate of the molten synthetic resin flowing out from both passages 12 and 13 to the nozzle hole 6a is adjusted, and the molten synthetic resin is adjusted. It is possible to form a stable skin layer without depending on the fluidity and the shape of the molded product. After that, the moving position of the piston 30b is detected by the second linear encoder 15, and the detected value at time t ₇ matches the preset value set in the control device 28b, and the control device 28b sends a signal to the control unit 35a. by outputting, by energizing between the electromagnetic solenoid 24 ₂ from the time t ₇ via the control unit 35a until time t _9, the switching in a direction to retract the piston 10a to flow pressure oil, the inner torpedo 8 The setting value set in the setting unit 31, that is, the state shown in FIG. After the electromagnetic solenoid 24 ₂ deenergized at time t _9, and between the inner torpedo 8 until the time t ₁₂ is held by the end retreat position shown by FIG. 3 (C), the electromagnetic solenoid 24 at time t _{12 1} to advance the inner torpedo 8 by Setsu換Ru the directional control valve 24 is energized, the between inner torpedo 8 from the time t ₁₃ to the time t ₁₅ is held in the state shown in FIG. 3 (a). Furthermore, since the movement position of the piston 30b which is detected by the second linear encoder 15 matches the predetermined set value in the control device 28b at time t _7, the control device 28b is able to output a signal to the controller 28a Control device 2
8a is between the time _{t 7} to the time _{t 11,} actuates the screw reciprocating apparatus 27a, the first screw _{1 1} time t
By advancing from ₇ to time t ₁₁ , the molten synthetic resin is press-fitted into the open outer passage 12,
From time t ₈ to t _11, only the skin layer is covered with the two molds 37.
It can be injected into the cavities 37d of a and 37b, and a good quality sandwich molded product in which the sprue of the lower mold 37b and its vicinity are also covered with the skin layer is obtained. Then, it becomes pressure holding state between from the time t ₁₀ to the time t _14, compensate shrinkage allowance of the molded article by the first screw 1 ₁ is slightly advanced to the most advanced position, then the time t ₁₄
Each control device 28a, 28b is a plasticizing drive device 29
By operating a and 29b, the first and second screws 1 ₁ and 2 ₁ retreat while rotating and plasticize, and reach the final retracted position at time t ₁₅ .

In this embodiment, since the pilot check valves 26a and 26b are provided in the path between the hydraulic cylinder 10 and the directional control valve 24, when the inner torpedo 8 is located at a predetermined intermediate position, the flow of pressure oil is prevented. Is reliably prevented, and the inner torpedo 8 is firmly held and stopped.

The time _t 1 _{~t 6,} t 7 first screw in _{~t 10 1 1} of forward motion and the time _t 4 ~t ₇ in the second
Forward movement of the screw 2 ₁ is not limited and uniform motion, may be one speed uniformly accelerated motion or stepwise increases. In addition, at times t _{6 to} t ₇ , the first screw 1 ₁
Is held at a predetermined intermediate position and the injection of the molten synthetic resin forming the skin layer is interrupted.
Although the skin layers in a and 37b are extended, this injection need not necessarily be interrupted.

Further, from time t ₆ to time t ₇ , the inner torpedo 8 may be temporarily advanced as indicated by the broken line X. As a result, when passing through the corner portion 37c of the cavity 37d, the flow rate of the molten synthetic resin becomes slow, and it is possible to reliably prevent the outer skin layer from breaking.

Further, in the above embodiment, the times t _{3 to} t ₄ and t.
Until ₉ ~t _12, inner torpedo 8 has been held in a state of the most retreated position shown in FIG. 3 (c) as the predetermined retracted position is not limited thereto, the state of the inner torpedo 8 , The state shown in FIG. 3 (c) and the state in which the state shown in FIG. 3 (c) is located ahead by the distance l ₁ from the state shown in FIG. 3 (c).

(Second Embodiment) As shown in FIG. 6, in the second embodiment, the inner torpedo drive device 18b has a hollow cylindrical shape with one end fixed to the shaft 9 and the other end formed with a penetrating female screw. The sliding body 39 and a cylindrical guide tube 40 that houses the sliding body 39.
And a rod-shaped screw member 43 having an external thread formed at one end thereof that can be screwed into the penetrating internal thread of the sliding body 39, and the output shaft 41a is connected to the screw member 43 via the coupling 42, and is controlled by the control unit 35b. It is composed of a forward / reverse rotatable electric motor 41 whose reverse rotation switching is controlled, and the other structure is the same as that of the first embodiment.

In the present embodiment, the rotational movement of the output shaft 41a of the electric motor 41 is converted into the linear movement of the sliding body 39 via the coupling 42 and the screw member 43, whereby the inner torpedo 8 is reciprocated via the shaft 9. Is something
Other operations are similar to those of the first embodiment.

Therefore, in this embodiment, as compared with the first embodiment, the inner torpedo drive device 18b has a simple structure, so that the molding machine can be downsized, there are few failures, and maintenance is easy.

As the electric motor 41 described above, a stepping motor, a pulse motor, or the like can be used.

Third Embodiment As shown in FIG. 7, in the third embodiment, the inner torpedo drive device 18c has a rack 46 fixed to the other end of the shaft 9 so as to extend in the axial direction of the shaft 9.
And a pinion 45 that meshes with the rack 46 is fixed to the output shaft 44a, the switching of forward and reverse rotation is controlled by the control unit 35c, and the forward and reverse rotatable electric motor 44 is supported by a table (not shown). The other structure is the same as that of the first embodiment.

Also in the present embodiment, the rotational movement of the output shaft 44a of the electric motor 44 is converted into the linear movement of the rack 46 via the pinion 45, so that the inner torpedo 8 is reciprocally moved via the shaft 9. The operation is similar to that of the first embodiment.

[Advantages of the Invention] Since the present invention is configured as described above, it has the effects described below.

In the invention of claim 1, only the inner torpedo is reciprocated to adjust the moving position of the inner torpedo to a predetermined intermediate position while forming a skin layer and a core layer injected from the outer passage and the inner passage, respectively. By adjusting the flow rate of the synthetic resin, a stable skin layer can be formed without depending on the fluidity of the resin and the shape of the sandwich molded product, flow marks do not occur, and the thickness of the skin layer and core layer is arbitrary Can be changed to, and a good molded product can be molded.

In the invention described in claim 2, (1) it has a simple structure in which only the inner torpedo is reciprocated, so that it is superior in strength.

(2) Since the flow rate of the molten synthetic resin flowing from the outer passage and the inner passage to the nozzle hole can be adjusted by automatically controlling the moving position of the inner torpedo according to the moving positions of the first screw and the second screw, The timing of resin injection and flow rate can be easily adjusted, a stable skin layer can be formed without depending on the fluidity of the resin and the shape of the molded product, and flow marks do not occur, and the skin layer and core layer The thickness of can be changed arbitrarily, and a good molded product can be molded.

(3) Since the inner passage and the outer passage are opened and closed at a portion very close to the mold, resin dripping from the tip of the nozzle can be prevented, and a separate dripping prevention device is unnecessary.

(4) Since the opening degree of the inner passage and the outer passage can be easily changed with high precision and response during the injection process at a site very close to the mold, even for molded products with complicated shapes or thickness changes A homogeneous product is easily obtained.

(5) It is possible to mold a sandwich molded product having different injection amounts or different material ratios by using one type of injection head by changing each set value.

According to the third aspect of the invention, since the reciprocating movement of the inner torpedo is performed by the action of fluid pressure, the driving force for reciprocating the shaft becomes large.

According to the invention described in claims 4 and 5, in addition to the effect described in claim 2, the molding machine has a small size, and there are few failures and maintenance is easy.

According to the sixth aspect of the invention, the inner torpedo is firmly held stationary.

In addition to the above effects, the invention according to claim 7 can be easily disassembled for inspection or cleaning, and maintenance is easy.

[Brief description of drawings]

FIG. 1 is a sectional view of a part of one embodiment of an injection molding machine of the present invention, and FIG. 2 is a sectional view taken along the line AA in FIG.
FIG. 3 shows the moving position of the inner torpedo 8 in each molding step of the nozzle part in the injection head of this embodiment,
(A) is a sectional view of an essential part showing a state where the inner torpedo is advanced to the most advanced position and the nozzle hole is closed, (B) is a sectional view of an essential part showing a state where the inner torpedo is located at a predetermined intermediate position. , (C) is a sectional view of an essential part showing a state in which the inner torpedo is retracted to the most retracted position to close the inner passage, and FIG. 4 shows the time t on the horizontal axis and the skin layer and the core layer on the vertical axis. FIG. 5 is a graph for explaining a series of molding steps by taking the injection amount of the molten synthetic resin to be injected, the moving positions of the first screw, the second screw and the inner torpedo, and FIG. 5 shows the main part (mold) of FIG. FIG. 6 is an enlarged sectional view, FIG. 6 is a main part configuration diagram showing a part of a second embodiment of the present invention in a section, and FIG. 7 is a main part configuration diagram showing a part of a third embodiment of the present invention in a section. is there. DESCRIPTION OF SYMBOLS ₁ ... 1st injection unit, 1 ₁ ... 1st screw 1a, 2a ... Head, 2 ... 2nd injection unit 2 ₁ ... 2nd screw, 3, 4 ... Connection part, 5 ... T-shaped injection head main body, 5a ... Base part , 5b ... Tip part, 6 ... Nozzle tip, 6a ... Nozzle hole, 6b ... Conical hole, 7 ... Outer torpedo, 7a ... Through hole, 7b ... Large diameter part, 8 ... Inner torpedo, 8a ... Boss part, 8b ... Tip Sealing surface, 8c ... Rear end seal portion, 8d ... Through hole, 9 ... Shaft, 10 ... Hydraulic cylinder, 10a ... Piston, 11 ... Valve housing, 12 ... Outer passage, 13 ... Inner passage, 14 ... First linear encoder, 15 ... 2nd linear encoder, 16 ... 3rd linear encoder, 17 ... Inner torpedo control device, 18a, 18b, 18c ... Inner torpedo drive device, 19 ... Hydraulic tank, 20 ... Hydraulic po Flop, 21 ... motor, 22 ... relief valve (regulator), 23 ... hydraulic meter, 24 ... directional control valve, ₂₄ 1, 24 2 _... electromagnetic solenoid 25 ... hydraulic pressure generating source, 25a, 25b ... variable throttle with the check valve (Speed controller), 26a, 26b ... Pilot check valve (check valve), 27a, 27b ... Screw reciprocating drive device, 28a, 28b ... Control device, 29a, 29b ... Plasticizing drive device, 30a, 30b ... Piston, 30c , 30d ... Cylinder, 31 ... Setting section, 32 ... Input section, 33 ... Comparison section, 34 ... Output section, 35a, 35b, 35c ... Control section, 36a, 36b ... Mold board, 37a ... Upper mold, 37b ... Bottom Mold, 37c ... Corner, 37d ... Cavity, 39 ... Sliding body, 40 ... Guide tube, 41 ... Electric motor, 41a ... Output shaft, 42 ... Coupling, 4 ... screw member, 44 ... motor, 44a ... output shaft, 45 ... pinion 46 ... rack, t ... time, _t 1 ~t _{15 ... time, l 1, l 2, l} 3 ... distance.

Claims (7)

[Claims] 1. An injection head main body (5) is connected to a first injection unit (1) and a second injection unit (2), and a valve housing (11) is fitted in the injection head main body (5). The outer passage (12) is formed by
Inside the valve housing (11), the tip sealing surface (8b)
And an injection molding machine having an injection head in which an inner passage (13) is formed by inserting a shaft (9) having an inner torpedo (8) having a rear end seal portion (8c) fixed to a front end thereof. Then, by retreating the inner torpedo (8), which was previously located at the most advanced position, to the predetermined retracted position via the shaft (9), only the outer passage (12) is opened to melt to form the skin layer. A mold (37) in which a synthetic resin is clamped from the outer passage (12).
a, 37b) and then by advancing the inner torpedo (8) through the shaft (9) to a predetermined intermediate position, the outer passage (12) and the inner passage (13).
Open together to open the outer passage (12) and the inner passage (1
3) Inject the molten synthetic resin for forming the skin layer and the core layer into the molds (37a, 37b) respectively, and then move the inner torpedo (8) to a predetermined retracted position via the shaft (9). Inside passage (13) by retracting
Closed, and melted synthetic resin from the outer passage (12) into the mold (3
7a, 37b) to form a skin layer by injection,
An injection molding method for a sandwich molded article, characterized in that a holding pressure is exerted on the molten synthetic resin filled in the mold (37a, 37b). 2. A first screw (1 ₁ ) and a second screw (2)
_The injection head body (5) is connected to a first injection unit (1) and a second injection unit (2) each having a valve housing (1).
The outer passage (12) is formed by inserting 1), and the inner torpedo (8) having the tip seal surface (8b) and the rear end seal portion (8c) is formed in the valve housing (11) at the tip portion. A control for axially reciprocating the inner torpedo (8) on the shaft (9), which comprises an injection head having an inner passage (13) formed by inserting a shaft (9) fixed to the shaft. Division (35
a, 35b, 35c) to which an inner torpedo drive device (18a, 18b, 18c) is connected, and the axial direction of the first screw (1 ₁ ), the second screw (2 ₁ ) and the inner torpedo (8) A first position detector (14), a second position detector (15) and a third position detector (16) for detecting the respective moving positions of the first position detector (14), and a detection value signal of the first position detector (14). Is input and the detection value signal matches the preset first setting value, the control unit (3
Inner torpedo (8) via 5a, 35b, 35c)
Is moved to a predetermined retracted position, and when the detected value signal matches the preset second set value, the control unit (35a, 3a
5b, 35c) to move the inner torpedo (8) to a predetermined intermediate position, and the second reciprocating screw drive (27b) of the second injection unit (2) to move the second
A control device (28a) for advancing the screw (2 ₁ ) to a predetermined position is provided in the first injection unit (1), and a detection value signal of the second position detector (15) is input,
When the detected value signal matches a preset set value, the inner torpedo (8) is moved to a predetermined retracted position via the control section (35a, 35b, 35c) and the first
Screw reciprocating drive device (27a) of the injection unit (1)
A control device (28b) for advancing the first screw (1 ₁ ) via the second injection unit (2) is provided on the other hand, while the detection value signal of the third position detector (16) is input, the detection value The control unit (35a, 35b, 35c) so that the signal becomes a preset value set in advance corresponding to the preset retracted position, the preset intermediate position and the preset retracted position, respectively.
Torpedo control device (1
An injection molding machine for sandwich moldings provided with 7). 3. The inner torpedo drive (18a) comprises a piston (10a) fixed to the other end of the shaft (9).
And a fluid pressure cylinder (10) for the piston (10a)
And a fluid pressure generation source (25) connected to the fluid pressure cylinder (10) through a three-position directional control valve (24),
A control unit (3) for controlling the switching of the directional control valve (24).
5a), and the injection molding machine of the sandwich molded product according to claim 2. 4. The inner torpedo drive device (18b) comprises a sliding body (39) fixed to the other end of the shaft (9).
A guide tube (40) of the sliding body (39), a screw member (43) having one end screwed to the sliding body (39), and an output shaft (41a) being the other end of the screw member (43). A forward / reverse rotatable electric motor (41) connected to the unit, and a control unit (35) for controlling switching of the forward / reverse rotation of the electric motor (41).
An injection molding machine for a sandwich molded article according to claim 2, which comprises b). 5. The inner torpedo drive device (18c) comprises a rack (46) fixed to the other end of the shaft (9) so as to extend in the axial direction of the shaft (9), and an output shaft (4).
4a) is a pinion (4) that meshes with the rack (46).
The injection of a sandwich molded product according to claim 2, comprising a forward-reverse rotation electric motor (5) to which 5) is fixed, and a control unit (35c) controlling switching of forward-reverse rotation of the electric motor (44). Molding machine. 6. A fluid pressure cylinder (10) and a directional control valve (2).
4) Pilot check valve (26a, 26a,
26b) is provided, The injection molding machine of the sandwich molded article according to claim 3. 7. An injection molding machine for sandwich molded articles according to claim 2, 3, 4, 5 or 6, wherein the injection head body (5) can be disassembled into a plurality of parts.