JPH02307712A - Method and machine for injection-molding sandwich molded item - Google Patents

Abstract

PURPOSE:To stably form skin layer and at the same time mold a conforming molded item with no flow mark by a method wherein the flow rates of molten synthetic resins, which are injected respectively through an outside passage and an inside passage for forming the skin layer and core layer, are controlled by reciprocating only an inside torpedo so as to adjust the moving position of the inside torpedo to the predetermined intermediate position. CONSTITUTION:A control device 28b brings a screw reciprocatingly driving device 27b into actuation so as to advance a second screw 21 to the most advanced position in order to force molten synthetic resin for forming core layer in an inside passage 13. As a result, a part of the molten synthetic resin for forming the skin layer is injected in a cavity 37d, which is formed between both molds 37a and 37b. Concretely, molten synthetic resins, which flow respectively through both passages 12 and 13, flow in a nozzle hole 6a in the laminar flow, in which the core layer is completely covered by the skin layer, and is injected in the cavity 37d, which is formed between both the molds 37a and 37b. Further, by automatically moving the inside torpedo 8 to the predetermined intermediate position in order to hold it to that position, the flow rates of the molten synthetic resins, which flow through both the passages 12 and 13 respectively in the nozzle hole 6a, are controlled so as to allow to stably form the skin layer.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention provides an injection molding method for a sandwich molded product, in which a molten synthetic resin forming a skin layer and a core layer is injected from a nozzle to obtain a sandwich molded product, and Regarding the injection molding machine.

[Prior Art] Conventionally, in this type of injection molding machine, the following (a) and (b) are known as T-shaped nozzles for a twin-screw injection molding machine equipped with two injection units. There is.

(a) The inner nozzle, which is arranged concentrically within the outer nozzle and is slidable in its axial direction, is made rotatable by a rotating means, and the resin passage is opened and closed by the rotation of the inner nozzle, and
An actuating rod for opening and closing a nozzle hole of the inner nozzle is provided in the inner nozzle (see Japanese Patent Laid-Open No. 59-220341).

(b) An annular insert arranged concentrically within the injection head is provided so as to be slidable in the axial direction, and a needle having a connection passage is provided within the annular insert so as to be freely rotatable;
The connecting passage is opened and closed by rotating the needle to supply gas (see Japanese Patent Laid-Open No. 63-94805).

In addition, as other injection molding machines, (c) a manifold block with a multi-passage nozzle,
A plurality of injection heads and the same number of resin passages as there are injection rams are formed leading to a multi-passage nozzle, and each resin passage is provided with two manifold valves, and each injection is controlled by opening and closing of each manifold valve and a microprocessor. There is a method for obtaining a multi-layer molded product by controlling the operation of a ram and controlling the opening and closing of a plurality of resin passages (Japanese Patent Laid-Open No. 63-999).
(See Publication No. 18).

[Problem to be solved by the invention] However, in the above conventional technology, (a), (
In the case of b), the nozzle opening/closing mechanism is complicated and multiple drive devices are installed, so the control of opening/closing the nozzle hole is complicated, and the molten synthetic resin flowing into the nozzle hole is It is difficult to control the flow rate, making it impossible to form a stable skin layer, and since the nozzle hole of the outer nozzle is opened and closed by sliding the inner cylinder (or annular insert), the molten resin flows out from the nozzle hole every shot. There are problems in that it causes stringiness and it is difficult to make the diameter of the T-shaped nozzle too small from a strength standpoint.

On the other hand, in case (c), the control of 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 injection ram. The flow rate of synthetic resin is controlled by fully opening and closing each resin passage and by changing the speed of the injection head or injection ram, so it is not possible to precisely change the relative proportion of the injection amount in each resin passage. For this reason, a homogeneous skin layer cannot be formed, and it is difficult to mold a molded product with a complicated shape. In addition, for molded products with different injection volumes or injection volume ratios, nozzles with different flow path shapes, flow path cross-sectional areas, flow path cross-sectional area ratios, etc. must be replaced for each molded product, making the molding work difficult. The problem is that it is complicated.

The present invention has been made in view of the problems of the above-mentioned conventional technology, and although it has a simple structure, it is possible to form a stable skin layer and prevent stringing from shot to shot. It is an object of the present invention to provide an injection molding method for a sandwich molded product and an injection molding machine for the same, in which opening and closing of an inner passage and an outer passage and timing adjustment between opening and closing of each passage and operation of an injection unit are easy.

[Means for Solving the Problems] In order to achieve the above object, the injection molding method for a sandwich molded product of the present invention connects an injection nozzle main body to a first injection unit and a second injection unit, and By inserting the valve housing into the valve housing, an outer passage is formed, and by inserting into the valve housing an inner shaft having a tip sealing surface and a rear end sealing part, the inner shaft is fixed to the tip. Using an injection molding machine with an injection nozzle with a passage formed,
A mold in which only the outer passage is opened by retracting the inner torpedo, which was previously located at the most forward position, to a predetermined retreat position via the shaft, and the molten synthetic resin for forming the skin layer is clamped from the outer passage. Then, by advancing the inner torpedo to a predetermined intermediate position through the shaft, both the outer passage and the inner passage are opened, and the melting to form the skin layer and the core layer from the outer passage and the inner passage, respectively. The synthetic resin is injected into the mold, and then the inner torpedo is retreated to a predetermined retracted position via the shaft to close the inner passage, and the molten synthetic resin is injected into the mold from the outer passage to form the skin layer. After forming, a holding pressure is applied to the molten synthetic resin filled into the mold.

Injection molding machines that are directly used to carry out the above injection molding method include those described below.

Connecting an injection nozzle body to a first injection unit and a second injection unit each having a first screw and a second screw, and forming an outer passage by fitting a valve housing into the injection nozzle body, An injection nozzle is provided in which an inner passage is formed by inserting into the valve housing a shaft having an inner torpedo fixed to the distal end thereof, the inner torpedo having a tip sealing surface and a rear end sealing portion, and the inner torpedo is inserted into the shaft in the axial direction. An inner torpedo drive device equipped with a control unit is connected to the inner torpedo drive device for reciprocating the inner torpedo, and a first position detector and a first A position detector □ and a third position detector are provided, and when a detected value signal of the first position detector is input and the detected value signal matches a preset first set value, to move the inner torpedo to a predetermined retreat position, and when the detected value signal matches a preset second set value, the inner torpedo is moved to a predetermined intermediate position via the control section and the second injection unit The first injection unit is provided with a control device that advances the second screw to a predetermined position via the screw reciprocating drive device, and the detected value signal of the second position detector is input, and the detected value signal is set in advance. A control device is provided in the second injection unit to move the inner torpedo to a predetermined retreat position via the control unit and advance the first screw via the screw reciprocating drive device of the first injection unit when the value matches the set value. Meanwhile, a detected value signal of the third position detector is input, and the detected value signal becomes each setting value corresponding to a preset predetermined retreat position, the predetermined intermediate position, and the predetermined retreat position, respectively. An inner torpedo control device is provided to perform feedback control of the control section.

The inner torpedo drive device also 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 three-position directional switching valve. , and a control section that controls switching of the directional switching valve.

The inner torpedo drive device includes a sliding body fixed to the other end of the shaft, a guide tube of the sliding body, a screw member having one end screwed to the sliding body, and an output shaft connected to the screw member. It consists of an electric motor connected to the other end of the member and capable of rotating in forward and reverse directions, and a control section that controls switching between forward and reverse rotation of the electric motor.

Furthermore, the inner torpedo drive device includes a rack fixed to the other end of the shaft so as to extend in the axial direction of the shaft, and an electric motor capable of forward and reverse rotation having a pinion fixed to the output shaft that meshes with the rack. and a control section that controls switching between forward and reverse rotation of the electric motor.

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

Furthermore, the injection nozzle body can be disassembled into multiple parts.

[Function] In the injection molding method and the injection molding machine of the present invention, when starting injection molding, first, the inner torpedo is advanced to the most advanced position and the inner passage and the outer passage are closed by its tip sealing surface. do. Next, the inner torpedo was retreated to a predetermined retreat position to close the inner passage and open the outer passage, and the molten synthetic resin forming the skin layer from the first injection unit to the outer passage was partially compressed and the mold was clamped. Inject into the mold. Then, by advancing the inner torpedo to a predetermined intermediate position, the inner passage is opened, and when the molten synthetic resin forming the core layer is press-fitted from the second injection unit into the inner passage, the molten synthetic resin flowing through both passages is transferred to the skin layer. The core layer is completely surrounded by a laminar flow, and the flow rate of the molten synthetic resin flowing out from both passages is controlled and injected into the mold. Then, by retracting the inner torpedo to a predetermined retracted position and injecting only the molten synthetic resin for forming the skin layer from the first injection unit into the mold,
After forming a skin layer covering the sprue of the mold and its vicinity, a holding pressure is applied to the molten synthetic resin in the mold by the first injection unit.

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

(First Example) Figures 1, 2, and 3 (A), (B), (c
), the first screw 1. A screw reciprocating drive device 27a that reciprocates the second screw 2. A first screw reciprocating drive device 27b that reciprocates the screw, a plasticization drive device 29a that rotates the first screw 11, and a plasticization drive device 29b that rotates the second screw 21.
Mistake unit 1. The second injection unit 2 is arranged in parallel on a moving table (not shown), and these first screws 11. The second screw 21 has cylinders 30c and 30 at its ends, respectively.
Pistons 30a and 30b are fixedly slidable within the d. The bi-firing units 112 each have heads la and 2a.

On the other hand, the T-shaped nozzle main body 5, which is an injection nozzle main body, has a base 5a having connection parts 3 and 4 protruding on both sides,
The nozzle is composed of a distal end 5b which is removably coupled with a bolt or the like (not shown), and the front opening of the distal end 5b has a conical hole 6b and a nozzle hole 6a communicating with the conical hole 6b. A chip 6 is removably fixed. Then, connect one of the connecting parts 3 to the first injection unit 1
The other connecting portion 4 is connected to the head 2a of the second injection unit 2. The above-mentioned nozzle depth 6
In this case, the nozzle hole 6a is the mold plate 36a.

A stopper die 37a and a lower die 37 respectively fixed to 36b.
It is located in a position communicating with the cavity 37d of the mold consisting of b. In this embodiment, a T-shaped injection nozzle body is shown, but the injection nozzle body is not limited to this, and various shapes may be used.

Further, an annular outer torpedo 7 is fitted into the tip portion of the T-shaped nozzle body 5, and a cylindrical valve housing 11 is disposed concentrically within the T-shaped nozzle body 5 at its rear end. An outer passage 12 is formed between the inner peripheral surface of the T-shaped nozzle body 5 and the outer peripheral surface of the valve housing 11.

Furthermore, a shaft 9 is inserted into the valve housing 11 and is reciprocated by a piston 10a provided inside a hydraulic cylinder 10 attached to the rear end of the hydraulic cylinder 10. An inner passage 13 is formed between the inner peripheral surface 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 the shaft 9
The host portion 8a is provided with a tip sealing surface 8b and a rear end sealing portion 8c. When this rear end seal portion 8c is inserted into the inner passage 13, the inner passage 13 is closed. On the other hand, in the hydraulic cylinder 10,
Check valves 25a, 25b with variable throttle, pilot check valve 26a.

26b and two electromagnetic solenoids 24.

A hydraulic pressure generating source 25 is connected via a four-bottle, three-position directional control valve 24 having a hydraulic pressure generating source 242.
5, hydraulic tank 19, hydraulic pump 20, hydraulic pump 2
0], relief valve 221 oil pressure gauge 2
Contains 3.

Then, the control section 35a switches the directional switching valve 24 by energizing or de-energizing the electromagnetic solenoids 24+ and 242 of the directional switching valve 24. The above-mentioned control section 35a, piston 10a, hydraulic cylinder 10, variable throttle check valves 25a, 25b, pilot check valves 26a, 26
b, the directional switching valve 24 and the hydraulic pressure generation source 25 constitute an inner torpedo drive device 18a.

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

Note that instead of providing the large diameter portion 7b on the inner circumferential surface of the outer torpedo 7 described above, the inner circumferential surface of the outer torpedo 7 is made large in diameter over the entire length, and the rear end seal portion 8c of the inner torpedo 8 is
The inner passage 13 may be closed by forming a sealing annular protrusion on the inner circumferential surface thereof, which is abutted by the annular protrusion. Further, the cross-sectional shape of the through holes 7a, 8d of both torpedoes 7.8 is not limited to the circular shape shown in the drawings, but can be made into various shapes. Further, instead of the through hole 7a of the outer torpedo 7, a groove may be formed in the outer circumference 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 are provided, which are respectively attached to the first screw It, the second screw 2.1 and the piston 10a, and detect the respective movement positions. The detection value signals detected by each linear encoder 14, 15, and 16 are the control device 28 of the first injection unit.
a, control device 28b of the second injection unit 2;

It is input to the inner torpedo control device 17.

This control device 28a is configured in advance in the axial direction (
The first and second set values of the movement position in the direction of arrow B) are set, and when the detection value signal detected by the first linear encoder 14 matches the first set value, the control unit 3
By outputting a signal to 5a, the control unit 35a energizes the electromagnetic solenoid 24□ of the directional control valve 24, switches the pressure oil so that it flows in the direction of retracting the piston 10a, and moves the inner torpedo 8 to the most retracted position. make them retreat.

After this, when the detected f-table signal matches the second set value,
By outputting a signal to the control unit 35a, the control unit 35
a energizes the electromagnetic solenoid 241, and the piston 10a
Switch so that the pressure oil flows in the direction of advancing the inner 1
- By advancing the pin 8 to a predetermined intermediate position and outputting a signal to the control device 28b of the second injection unit 2, the control device 28b operates the screw reciprocating drive device 27b, and the second screw 2. is advanced to a predetermined position, that is, the most advanced position.

On the other hand, the control device 28b has a set value for the movement position of the piston 30b in the axial direction set in advance, and when the detection value signal detected by the second linear encoder 15 matches the set value, the control unit 35a By outputting a signal, the electromagnetic solenoid 24° is energized and switched, the inner torpedo 8 is retracted to the most retracted position, and the first
By outputting a signal to the control device 28a of the injection unit 1, the control device 28a operates the screw reciprocating drive device 27a.
By operating the first screw 11, the first screw 11 is advanced 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), etc., and cannot be changed. It is possible.

The inner torpedo control device 17 includes an input section 32 that inputs a detection value signal detected by the third linear encoder 16, and an input section 32 that inputs a detection value signal detected by the third linear encoder 16, and a respective a setting section 3 where a set value is set], a comparison section 33 that outputs a signal to an output section 34 when the detected value signal from the input section 32 and the setting value of the setting section 31 match, and a comparison section 33 that outputs a signal to the output section 34; Receive signal
1. Control unit 35a of inner torpedo drive device 1.8a
The output section 34 outputs a stop signal to switch the directional control valve 24 to an intermediate position via the control section 35a, and feeds back the moving position of the piston 10a to the control section 35a. The setting value corresponding to the predetermined intermediate position of the inner torpedo 8 in the setting part 31 is determined by the fluidity of the molten synthetic resin;
It is determined by 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 the state in which the inner torpedo 8
is located at a predetermined intermediate position, and the outer passage 12 and the inner passage 13 are fully open.If the inner torpedo 8 is advanced by f23 from this state, it will be in the state shown in FIG. When the rear end seal portion 8c comes into contact with the outer torpedo 7, the inner passage 13 is closed. 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 .degree. C. 1 as shown in FIG. 3(C).

Next, the operation of this embodiment will be explained with reference to FIG. 4 as well.

When starting injection molding, first, the first injection unit 1
and each control device 28a, 28b of the second injection unit 2
A signal is output to the control section 35a of the inner torpedo drive device 18a, and the control section 35a energizes the electromagnetic solenoid 241 of the directional control valve 24 to switch so that the pressure oil flows in the direction of advancing the piston 10a. 1゜a
By advancing the inner torpedo 8 through the shaft 9 to the most advanced position as shown in FIG. Close the inner passage 13. Each control device 28a, 28b is a plasticizing drive device 29a, respectively.
, 29b to output a signal to the first screw 1. and the second
As the screw 2I rotates, the synthetic resin in the first injection unit 1 and the second injection unit 2 is plasticized. Then, as shown in FIG. 4, at time t.

The control device 28a operates the screw reciprocating drive device 27a to operate the first screw 1. from time t1 to time t6. By advancing the molten synthetic resin, a portion of the molten synthetic resin for forming a skin layer is forced into the outer passageway 12. During this time, the moving position of the piston 30a in the axial direction is detected by the first linear encoder 14, and the time t2. 'j4, those detected values are set in advance in the control device 28a, respectively. When the value matches the second set value, the control device 28a energizes the electromagnetic solenoid 242 of the opening direction switching valve 24 from time t2 to time t3 via the control unit 35a, so that the pressure oil flows in the direction of retracting the piston 10a. Switch to
After retracting the inner torpedo 8 to the setting value set in the setting part 31, that is, to the most retracted position shown in FIG. Figure 3 (C) shows the torpedo 8 on the opening force side.
After maintaining the state shown in , the electromagnetic solenoid 241 is energized from time t4 to time t6 to advance the inner torpedo 8 to the set value set in the setting section 31, that is, to a predetermined intermediate position, By de-energizing the electromagnetic solenoid 24 at time ◯, the opening force side torpedo 8 is maintained in the state shown in FIG. 3(B) until time t7. On the other hand, the movement position of the piston 30a detected by the first linear encoder 14 at time t4 is determined by the control unit N28a.
Since it matches the second set value set in advance, the control device 28a outputs a signal to the control device 28b to
The control device 28b operates the screw reciprocating drive device 27b from time t4 to time t7, and the second screw 2□
The molten synthetic resin for forming the core layer is press-fitted into the inner passageway 13 by advancing it to the most advanced position between time t4 and time t7. As a result, a portion of the molten synthetic resin for forming the skin layer is transferred from time t2 to time t.
5, the molten synthetic resin is injected into the cavities 37d of the clamped molds 37a and 37b, and flows through both roads 12 and 13 from time t5 to time t8, forming a skin layer inside the nozzle hole 6a. The core layer is completely wrapped in a laminar flow and flows into the cavities 3 of both molds 37a and 37b.
Created within 7d. 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, 13 to the nozzle hole 6a is adjusted, and the molten synthetic resin A stable skin layer can be formed without depending on the fluidity of the molded product or the shape of the molded product. After this, the movement position of the piston 30b is detected by the second linear encoder 15, and the movement position of the piston 30b is detected at time t.
At step 7, the detected value matches the preset value set in the control device 28b, and the control device 28b outputs a signal to the control section 35a, thereby controlling the period from time t7 to time t9 via the control section 35a. energize the electromagnetic solenoid 242,
The pressure oil is switched to flow in the direction of retracting the piston 10a, and the inner torpedo 8 is retracted to the setting value set in the setting section 31, that is, the state shown in FIG. 3(C).

At time t9, the electromagnetic solenoid 242 is de-energized,
After holding the opening force side torpedo 8 at the most retracted position shown in FIG. 3(C) until time t12, the inner torpedo is turned on by energizing the electromagnetic solenoid 24 and switching the directional control valve 24 at time t12. 8 is advanced, and the opening force side torpedo 8 is maintained in the state shown in FIG. 3(A) from time t+3 to time t15. Furthermore, since the movement position of the piston 30b detected by the second linear encoder 15 at time t7 matches the set value preset in the control device 28b, the control device 28b outputs a signal to the control device 28a. , the control device 28a changes from time t to time tll.
In the meantime, the screw reciprocating drive device 27a is operated to advance the first screw 11 from time t7 to time t11, thereby pressurizing the molten synthetic resin into the open outer passage 12. , from time t8 to time t11+, only the skin layer is inserted into the cavities 37d of both molds 37a and 37b.
A high-quality sandwich molded product can be obtained in which the sprue of the lower mold 37b and its vicinity are also covered with a skin layer. Then, from time t1° to time t14, the pressure is maintained, and the first screw 11 moves slightly forward to the most advanced position to compensate for the shrinkage of the molded product, and then at time t14, each control device 28a, 28b operates the plasticizing drive devices 29a, 29b,
The first and second screws 11, 2+ are rotated and retracted to perform plasticization, and reach the most retracted position at time t'5.

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 pressure oil does not flow. is reliably prevented, and the inner torpedo 8 is firmly held at a stop.

Note that the forward movement of the first screw 11 from time t1 to ta and from t7 to tlo and the second movement from time t4 to t7
The forward motion of the screw 2I is not limited to uniform motion, and may be uniform acceleration motion or stepwise increasing speed. Further, from time t8 to time t7, the first screw 11 is held at a predetermined intermediate position and the injection of the molten synthetic resin forming the skin layer is interrupted, and during this time both molds 37a
, 37b, but this injection does not necessarily have to be interrupted.

Further, the inner torpedo 8 may be moved forward temporarily from time t6 to time t7, as indicated by the broken line X. Thereby, when passing through the corner 37c of the cavity 37d, the flow velocity of the molten synthetic resin is slowed down, and tearing of the outer skin layer can be reliably prevented.

Further, in the above embodiment, the inner torpedo 8 is maintained at the most retracted position shown in FIG. However, the state of the inner torpedo 8 is not limited to this, and the state of the inner torpedo 8 may be at an intermediate position between the state shown in FIG.

(Second Embodiment) As shown in FIG. 6, in the second embodiment, the inner torpedo drive device 18b has a hollow cylindrical shape that is fixed to the shaft 9 at one end and has a through female thread formed at the other end. a sliding body 39; a cylindrical guide tube 40 that accommodates the sliding body 39;
A rod-shaped screw member 43 is formed at one end with a male screw that can be screwed into the through-female screw of the sliding body 39, and an output shaft 41a is connected to the screw member 43 via a coupling 42, and is controlled by the control section 35b. It consists of a motor 41 capable of forward and reverse rotation, which is controlled to switch between forward and reverse rotation, and the other components are a first
It is the same as that of the example.

In this embodiment, the inner torpedo 8 is reciprocated via the shaft 9 by converting the rotational motion of the output shaft 41a of the electric motor 41 into the linear motion of the sliding body 39 via the coupling 421 and the screw member 43. and
Other operations are similar to those of the first embodiment.

Therefore, in this embodiment, compared to the first embodiment, the inner torpedo drive device 18b has a simpler structure, so the molding machine is smaller, less likely to break down, and easier to maintain.

The electric motor 41 mentioned above is a stepping motor.

A pulse motor etc. can be used.

(Third Embodiment) As shown in FIG. 7, in the third embodiment, the inner torpedo drive device 18c includes a rack 46 fixed to the other end of the shaft 9 so as to extend in the axial direction of the shaft 9.
When the output shaft 44a is engaged with the rack 46, a two-on 45 is fixed, and a control unit 35c controls switching between forward and reverse rotation, and an electric motor 44 capable of forward and reverse rotation is supported on a stand (not shown). The other configurations are the same as those of the first embodiment.

In this embodiment as well, the inner bead 8 is reciprocated via the shaft 9 by converting the rotational motion of the output shaft 44a of the electric motor 44 into linear motion of the rack 46 via the pinion 45. , and other operations are similar to those of the first embodiment.

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

In the invention as claimed in claim 1, only the inner torpedo is reciprocated, and while the movement position of the inner torpedo is adjusted to a predetermined intermediate position, the melt forming the skin layer and the core layer is 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 or the shape of the sandwich molded product, and flow marks do not occur, and the skin layer and core layer are The thickness of the molded material can also be changed as desired, allowing molded products of good quality to be produced.

In the invention as claimed in claim 2, (1) the structure is simple in that only the inner torpedo is reciprocated, so it is superior in strength;

(2) Adjust the flow rate of the molten synthetic resin flowing from the outer passage and the inner passage to the nozzle hole by adjusting the movement position of the inner torpedo to the first position.
Adjustment can be made by automatic control according to the movement position of the screw and the second screw, making it easy to adjust the timing of resin injection and flow rate, making it stable without depending on the fluidity of the resin or the shape of the molded product. It is possible to form a skin layer with a high quality, no flow marks are generated, the thickness of the skin layer and core layer can be changed as desired, and a molded product of good quality can be molded.

(3) Since the inner and outer passages are opened and closed at a location very close to the mold, resin can be prevented from dripping from the nozzle tip, and a separate drip prevention device is not required.

(4) The opening degree of the inner and outer passages can be easily changed with high precision and responsiveness during the injection process at a location very close to the mold, allowing molded products with complex shapes or varying thicknesses to be processed. A homogeneous product can be easily obtained.

(5) Sandwich molded products with different injection amounts or material ratios can be molded with one type of nozzle by changing each setting value.

In 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.

In the invention set forth in claims 4 and 5, in addition to the effects set forth in claim 2, the molding machine becomes smaller, has fewer breakdowns, and is easy to maintain.

In the invention set forth in claim 6, the stopping and holding of the inner 1-beat becomes firm.

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

[Brief explanation of the drawing]

FIG. 1 is a partially sectional configuration diagram of an embodiment of an injection molding machine of the present invention, FIG. 2 is a sectional view taken along line A-A in FIG. 1,
FIG. 3 shows the movement position of the inner torpedo 8 in each molding process of the nozzle of this embodiment, and (A) is a sectional view of the main part showing the state in which the inner torpedo is advanced to the most advanced position and the nozzle hole is closed. , (B) is a sectional view of the main part showing a state in which the inner torpedo is located at a predetermined intermediate position, and (C) is a sectional view of the main part showing a state in which the inner torpedo is retreated to the most retracted position and the inner passage is closed. In FIG. 4, the horizontal axis is time t,
Figure 5 is a graph for explaining a series of molding processes, with the vertical axis representing the injection amount of molten synthetic resin forming the skin layer and core layer, and the movement positions of the first screw, second screw, and inner torpedo. Fig. 1 is an enlarged sectional view of the main part (mold), Fig. 6 is a partial cross-sectional view of the main part of the second embodiment of the present invention, and Fig. 7 is an example of the third embodiment of the invention. FIG. 3 is a diagram illustrating the configuration of main parts in cross section. 1... first injection unit, 1. ...1st screw I
a, 2a...Het, 2...Second injection unit 2
1...Second screw, 3.4...Connection part, 5.
...T-shaped nozzle body, 5a...base, 5b...
Tip, 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 seal surface, 8c...Rear end seal part, 8d...Through hole, 9...Shaft,
DESCRIPTION OF SYMBOLS 10... Hydraulic cylinder, 10a... Piston, 11... Valve bousing, 12... Outer passage, 13... Inner passage, 1
4... 1st linear encoder, 15... 2nd linear encoder, 16... 3rd linear encoder, 17... Inner Tobee I control device, 18a, 18b
], 8c...Inner torpedo drive device, 19...Hydraulic tank, 20...Hydraulic pump,
21... Electric motor, 22... Relief valve (regulator), 23... Oil pressure gauge, 24... Directional switching valve, 24+, 24
□...Electromagnetic solenoid, 25...Hydraulic pressure source, 25a, 25b...Check valve with variable throttle (speed controller), 26a, 26b...Pilot check valve (check valve), 27a, 27b ...Screw reciprocating drive device, 28a,
28b-control device, 29a, 29b...plasticization drive device, 30a, 30b
・=Piston, 30c, 30d-cylinder, 31... Setting section, 32... Input section, 33.
...Comparison section, 34...Output section, 35a, 35
b, 35c...-control unit, 36a, 36b-mold plate, 37
a - Upper mold, 37b...Lower mold, 37c.
... Corner, 37d... Cavity, 39... Sliding body, 40... Guide tube, 41... Electric motor,
41a... Output shaft, 42... Coupling, 43... Screw member, 44... Electric motor, 44
a... Output shaft, 45... Pinion, 46...
・Rack, t...Time, t+"j+5・
...Time 1. 9. , j22. f23...distance.

Claims (1)

[Claims] 1) A first injection unit (1) and a second injection unit (
By connecting the injection nozzle body (5) to the injection nozzle body (5) and inserting the valve housing (11) into the injection nozzle body (5), an outer passageway (12) is formed, and the valve housing (11) is connected to the valve housing (1). an inner torpedo (8) having a tip sealing surface (8b) and a rear end sealing portion (8c) therein;
An injection molding machine equipped with an injection nozzle in which an inner passageway (13) is formed by inserting a shaft (9) with a shaft (9) fixed to the tip thereof is used. ) through the shaft (9) to a predetermined retracted position.
The molds (37a, 37b) are opened and the molten synthetic resin for forming the skin layer is clamped from the outer passageway (12).
), and then opening both the outer passageway (12) and the inner passageway (13) by advancing the inner torpedo (8) via the shaft (9) to a predetermined intermediate position, thereby opening the outer passageway (12). Molten synthetic resin for forming the skin layer and core layer is injected into the molds (37a, 37b) from the inner passageway (13), respectively, and then the inner toe beat (8) is injected into a predetermined position via the shaft (9). The inner passageway (13) is closed by retracting the molds (37a, 37b) to the retracted position.
) to form a skin layer, the mold (37a
, 37b) A method for injection molding a sandwich molded product, characterized in that holding pressure is applied to the molten synthetic resin filled into the interior. 2) First screw (1_1), second screw (2_1)
The injection nozzle body (5) is connected to the first injection unit (1) and the second injection unit (2) each having a In addition to forming a passageway (12), a tip sealing surface (8) is provided within the valve housing (11).
b) and an injection nozzle in which an inner passageway (13) is formed by inserting a shaft (9) fixed to the tip end of the inner torpedo (8) having a rear end seal part (8c); 9), an inner torpedo drive device (18a, 18b, 18c) equipped with a control section (35a, 35b, 35c) for reciprocating the inner torpedo (8) in the axial direction is connected to the first A first position detector (14), a second position detector (15), and a third position detector that detect the axial movement positions of the screw (1_1), the second screw (2_1), and the inner torpedo (8), respectively. (16), and furthermore, when the 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 (35a, 35b, 35c ), and when the detected value signal matches the preset second set value, the inner torpedo (8) is moved via the control section (35a, 35b, 35c) to a predetermined retreat position. 8) to a predetermined intermediate position and advances the second screw (2_1) to a predetermined position via the screw reciprocating drive device (27b) of the second injection unit (2). The detection value signal of the second position detector (15) is input to the injection unit (1), and when the detection value signal matches a preset setting value, the control unit (35a, 35b, 35c) is activated. A control device (28b) that moves the inner torpedo (8) to a predetermined retreat position through the control device and advances the first screw (1_1) through the screw reciprocating drive device (27a) of the first injection unit (1). The second injection unit (2) is provided with a detection value signal of a third position detector (16), and the detection value signal is inputted to a predetermined retreat position, the predetermined intermediate position, and a predetermined retreat position. The control units (35a, 35b)
, 35c) is provided with an inner torpedo control device (17) for feedback control. 3) The inner torpedo drive (18a) has a shaft (
9) A piston (10a) fixed to the other end, a fluid pressure cylinder (10) of the piston (10a), and a three-position directional switching valve (24) connected to the fluid pressure cylinder (10). The injection molding machine for sandwich molded products according to claim 2, comprising a fluid pressure generation source (25) connected to the fluid pressure generating source (25) and a control section (35a) for controlling switching of the directional switching valve (24). 4) The inner torpedo drive (18b) has a shaft (
9) A sliding body (39) fixed to the other end, a guide tube (40) of the sliding body (39), and a screw member (4) having one end screwed to the sliding body (39).
3), an electric motor (41) whose output shaft (41a) is connected to the other end of the screw member (43) and is rotatable in forward and reverse directions, and control for controlling switching between forward and reverse rotation of the electric motor (41). The injection molding machine for sandwich molded products according to claim 2, comprising: a part (35b). 5) The inner torpedo drive (18c) has a shaft (
9) A rack (46) is fixed to the other end 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). an electric motor (44) capable of forward and reverse rotation;
A control unit (35c) that controls switching between forward and reverse rotation of 44)
An injection molding machine for sandwich molded products according to claim 2, comprising: 6) Pilot check valves (26a, 26b) in the path between the fluid pressure cylinder (10) and the directional control valve (24)
4. The injection molding machine for sandwich molded products according to claim 3, further comprising: . 7) An injection molding machine for sandwich molded products according to claim 2, 3, 4, 5 or 6, wherein the injection nozzle body (5) can be disassembled into a plurality of parts.