JPH07246637A - Injection molding device - Google Patents

Abstract

PURPOSE:To cast resin surely into a cavity by connecting and arranging a cylinder part holding a turnable and movable screw member between a resin flow path and gate, contrive prevention of dwell of resin and unification of a resin temperature and manufacture a high-quality molded product by optimization of a molding condition. CONSTITUTION:A screw 31 is held turnably and movably into a cylinder 30 connected with a resin flow path 20. Simultaneously with injection of resin, a hydraulic pump 50 and a screw 31 are turned and resin is kneaded while the resin is being rolled into the cylinder 30. With the rolling-in of resin, the screw 31 and a hydraulic motor 50 are moved backward and when a quantity of a fixed backward movement is attained, injection of the resin from an injection nozzle 1 and a rotation of the hydraulic motor 50 are stopped by a displacement meter 63. Then when the screw 31 is moved forward by raising hydraulic pressure within a cylinder 60, the resin within the cylinder 30 is extruded and a gate 3a is opened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding apparatus, and more particularly to a structure suitable for an injection molding apparatus having a hot runner system configured to directly supply molten resin to the vicinity of a gate.

[0002]

2. Description of the Related Art Conventionally, in a molten resin supply system of an injection molding machine, a resin corresponding to a sprue or a runner portion in a cold runner system is constantly heated and only a resin inside a cavity is cured to manufacture a molded product. The hot runner system is used. In this system, a molten resin channel is formed inside the mold manifold and toppede, and a gate opening / closing mechanism for heating the periphery of this channel and opening / closing the gate at the end of the channel is provided. It is provided. As the gate opening / closing mechanism, for example, a needle valve structure is used. In this case, the tip of the needle is normally pressed against the gate to close the gate, but at the time of injection, by opening the gate by separating the tip of the needle from the gate, the molten resin is injected from the flow path into the cavity. It is like this. When a predetermined amount of molten resin is injected into the cavity, the needle is pressed against the gate to close the gate, and when the resin in the cavity solidifies, the mold opens and the molded product is taken out. . In this case, the points to be especially noted are the molten resin state in the manifold,
That is, uniformity of resin temperature, temperature change and residence time in the manifold, material deviation due to injection, resin temperature in the cavity, injection pressure and injection speed, resin filling point in the cavity, molded product side and manifold The temperature difference with the side and its repeated stability.

[0003]

In the above-mentioned conventional injection molding machine, particularly, the resin temperature, the injection pressure and the injection speed are controlled, and the pressure in the cavity is maintained at a predetermined value after the resin is filled, so that a precise molded product can be obtained. There are several drawbacks to carrying out precision molding processes for producing a. That is, after the molten resin is supplied from the injection nozzle into the mold, it passes through a relatively long flow path formed in the manifold and the toppede and is injected into the cavity from the gate. Therefore, there are the following problems. 1) Since the molten resin passes through the inside of the flow path while being heated by the heaters, temperature unevenness occurs in the uniform resin temperature as it passes through the flow path. For example, the temperature of the resin at the initial stage of injection, which is heated for a long time in the channel, may be higher than the resin temperature at the latter stage of injection. In this case, it is impossible to prevent the temperature rise of the injected resin because the resin is further pressurized during the injection into the cavity. 2) Due to the temperature change that occurs when passing through the flow path, and because the resin in the part of the flow path that is particularly close to the pipe wall stays longer than the resin that passes through the center of the flow path, deviation in material movement due to injection also occurs. Since it is easy, heat deterioration of the material may be caused. In particular, in general, the higher the injection pressure or the injection speed, the higher the temperature rise of the resin and the higher the compressibility, so the specific volume becomes smaller. Therefore, the quality of the molded product is further deteriorated. 3) Since the flow path is long, it is difficult to detect the filling point in the cavity based on the moving amount of the molding machine screw and the injection pressure waveform, and the controllability of the injection pressure and the injection speed is poor. Setting is difficult. As described above, the hot runner system has problems such as temperature control and thermal deterioration of the supplied resin, and it is difficult to control the molding conditions with high accuracy in order to improve the accuracy of the molded product. Therefore, the present invention has been made in view of the above problems, and its problem is to prevent deterioration of uniformity and thermal deterioration of the resin and to control molding conditions with high precision, whereby high-quality molded products can be manufactured. It consists in configuring an injection molding device.

[0004]

In order to solve the above problems, the present invention provides an injection molding apparatus provided with a resin flow path for supplying a molten resin toward the inside of a cavity for molding a molded product. The means includes a cylinder portion connected between a gate formed in the vicinity of the inlet of the cavity and the resin flow path, and a screw housed inside the cylinder portion so as to be rotatable about the axis and movable in the axis direction. A member, a rotation driving means for rotating the screw member, and a moving means for moving the screw member in the axial direction are provided.

Here, in the cylinder portion, it is preferable to provide a backflow preventing mechanism for preventing the resin flow backflowing along the periphery of the screw member.

Further, it is preferable to provide a gate opening / closing means for opening / closing the gate by increasing / decreasing the resin pressure at the tip of the cylinder portion.

Further, it is preferable that a detecting means for detecting the moving amount of the screw member is provided and the rotation driving means and / or the moving means is controlled according to the moving amount detected by the detecting means.

[0008]

According to the first aspect of the invention, the molten resin supplied through the resin flow path is caught by the rotation of the screw member,
And it is kneaded. Further, the screw member itself retracts due to the winding of the resin by the screw member, and thereafter, when a predetermined amount of resin is introduced into the cylinder portion, by advancing the screw member, the resin can be injected into the cavity. . Therefore, since the molten resin injected into the cavity is supplied from the cylinder portion every cycle, the amount of the molten resin retained can be reduced as compared with the conventional method, and the resin temperature and the resin material injected into the cavity can be reduced. Uniformity can be achieved. Moreover,
The resin flow in the resin flow channel smoothly flows due to the winding of the screw member, and the resin is then kneaded in the cylinder, so that the residence amount of the resin is significantly reduced and the uniformity of the resin temperature and the components is further enhanced. Therefore, a high-quality molded product can be manufactured.

According to the second aspect, since the backflow preventing mechanism is provided inside the cylinder portion, when the resin is injected from the cylinder portion into the cavity by the forward movement of the screw member,
It is possible to prevent the reverse flow of the resin from the cylinder portion to the resin flow path, avoid the stagnation of the resin once introduced into the cylinder portion, and accurately set the injection pressure by moving the screw member.

According to the third aspect, since the gate opening / closing means opens the gate when the resin pressure rises, it is not necessary to provide a driving unit for opening / closing the gate, and the internal structure of the cylinder section is not required. Can be easily configured.

According to the fourth aspect, since the amount of resin introduced into the cylinder portion can be known because the amount of movement of the screw member is detected and the molding process is controlled, the molding conditions can be further improved.

More specifically, by applying the fluid pressure to the screw member by the moving means, the resin can be wound into the cylinder portion at a predetermined pressure due to the rotation of the screw member. This fluid pressure determines the resin pressure in the cylinder and the movement amount (retraction amount) of the screw member.

Further, a step of winding the resin into the cylinder portion, a step of pushing the resin out of the cylinder portion into the cavity,
Also, by changing the fluid pressure for each pressure holding step of holding the resin pressure in the cavity, it is possible to set the resin pressure and the flow rate independent of each step.

[0014]

Embodiments of the injection molding apparatus according to the present invention will now be described with reference to the drawings. FIG. 1 shows an internal structure of a molding die according to this embodiment. Inside the die, a manifold 2 and a toppede 3 which form a flow path of resin injected from an injection nozzle 1 of a molding machine, A mold plate 4 having a cavity for molding a molded product is housed.

The manifold 2 includes a resin flow passage 20 for passing the molten resin injected from the injection nozzle 1, a heater 21 arranged around the resin flow passage 20, and a heat insulating plate 22 for keeping the manifold 2 warm. Have.

The toppede 3 includes a cylinder 30 connected to the resin passage 20, a screw 31 extending from the inlet side of the cylinder 30 toward the outlet side, and a needle nozzle 32 attached to the outlet side of the cylinder 30. , Cylinder 30
Member 33 mounted between the needle and the needle nozzle 32
A support member 35 slidably attached to the connection member 33 and biased in the outlet direction by the elastic force of a coil spring 34, which is an elastic member, and fixed to the support member 35. A needle shaft 36 for closing a nozzle hole formed at the tip of the cylinder, a band heater 37 wound around the cylinder 30, and a needle nozzle 3
2 has a band heater 38 wound around the circumference and a temperature sensor 39 for detecting the temperature of the cylinder 30.

A core 40 for molding a molded product is accommodated in the template 4, and a cavity 41 is formed in the core 40. Molten resin is injected into the cavity 41 from a gate 3a formed at the tip of the toppede 3. The molded product formed by solidifying the resin in the cavity 41 is projected by the ejector pins 42 arranged at a plurality of locations.

The screw 31 has a conical tip portion, a spiral fin 31a formed on the outer peripheral surface, and a backflow prevention ring 31b attached near the tip of the outer peripheral surface. The rear end of the screw 31 is connected to the hydraulic motor 50 via a connecting shaft 51. The hydraulic motor 50 is
An oil pressure chamber 52 formed inside and a connecting shaft 51 are rotatably accommodated in the oil pressure chamber 52, and a blade 53 is provided around the oil pressure chamber 52.
and a rotating body 53 having a. The rotating body 53 is adapted to rotate due to the difference in hydraulic pressure supplied by the hydraulic pipes 54 and 55. The hydraulic motor 50 is slidably accommodated in the cylinder 60, and is moved back and forth by the hydraulic pressure supplied by the hydraulic pipe 61. A detection rod 62 is fixed to the outer wall of the hydraulic motor 50, and the amount of movement of the hydraulic motor 50 can be detected by a displacement gauge 63 such as a magnet scale or a linear encoder.

Next, the molding process according to this embodiment will be described.
As shown in FIG. 2A, when the hydraulic motor 50 is rotated by forming a predetermined hydraulic pressure difference between the hydraulic pipes 54 and 55, the connected screw 31 also rotates. The molten resin in the resin flow path 20 is caught by the rotation of the screw 31, and at the same time, the resin corresponding to the amount of the taken-in resin is injected from the injection nozzle 1. The screw 31 retracts in the cylinder 30 while winding the molten resin, and at the same time retracts the hydraulic motor 50 to which a predetermined hydraulic pressure is applied by the hydraulic pipe 61 in the cylinder 60 (cylinder injection step). At this time, the screw 31 kneads the resin flowing into the cylinder 30 while positively pulling the resin out of the resin flow path 20 by rotation.

The displacement meter 63 detects the amount of retreat of the hydraulic motor 50 and the screw 31, and when a predetermined amount of retreat is reached, the hydraulic pressure difference between the hydraulic pipes 54 and 55 is eliminated to stop the rotation of the screw 31 and to eject the screw. The injection of resin from the nozzle 1 is also stopped. Therefore, the inflow of resin into the cylinder 30 is also stopped. The above steps may be performed from the time when the resin is injected into the cavity 41 and the gate 3a is closed to the time when the next resin is injected. Therefore, screw 3
Rotation and retraction of 1 can be done slowly. The temperature of the cylinder 30 is controlled by a band heater 37 and a temperature sensor 39, and is maintained at a predetermined temperature. The winding and kneading of the resin by the screw 31 promotes the homogenization of the temperature and components of the resin material, and further enhances the matching between the resin temperature in the cylinder 30 and the control temperature. Further, the inclusion of the resin by the screw 31 reduces the pressure of the resin in the resin flow path 20, and the resin is smoothly and evenly distributed in the cylinder 3
There is also an effect of moving the resin to 0, and it is also possible to prevent the resin, particularly in the vicinity of the peripheral wall of the resin flow path, from accumulating, and to avoid thermal deterioration of the resin.

Next, as shown in FIG. 2B, the hydraulic pipe 6
When the hydraulic pressure in the cylinder 60 is increased by 1, the hydraulic motor 50 and the screw 31 move forward. Screw 3
Since the backflow prevention ring 31b blocks the backflow of the resin with the advance of 1, the resin is pushed forward with the advance of the screw 31. Incidentally, as shown in FIG. 2 (c), normally, since a gap A is formed between the backflow prevention ring 31 b and the outer peripheral surface of the screw 31, the resin can flow to the front side of the cylinder 30. However, when the resin tries to flow to the rear side of the cylinder 30, the backflow prevention ring 3
The stepped portion B of 1b and the stepped portion C of the screw 31 are in contact with each other to cut off the resin flow path.

When the resin in the cylinder 30 is pushed forward, the resin pressure in the needle nozzle 32 increases, and this pressure causes the support member 35 to retreat against the elastic force of the coil spring 34, causing the needle shaft 36 to move to the nozzle. Move away from the hole. When the needle shaft 36 retracts, resin is injected from the gate 3a into the cavity 41. As described above, the resin is pushed out in the vicinity of the cavity 41, so that by setting the hydraulic pressure of the hydraulic pipe 61, the resin can be injected under desired molding conditions (the resin injection pressure and the injection speed) ( Cavity filling process). The amount of forward movement of the screw 31 is detected by the displacement meter 63, and when a predetermined amount of forward movement is obtained, the hydraulic pressure of the hydraulic pipe 61 is lowered and the forward movement of the screw 31 is stopped. At this time, the hydraulic pressure in the cylinder 60 that drives the screw 31 fluctuates when the inside of the cavity 41 is filled with the molten resin. Therefore, by detecting this fluctuation, the filling point of the resin into the cavity 41 is confirmed. be able to. When the screw 31 stops, the pressure in the needle nozzle 32 decreases, and the needle shaft 36 returns to the front due to the elasticity of the coil spring 34 to return to the gate 3
a is closed.

When the holding pressure control for maintaining the inside of the cavity 41 at a predetermined pressure is performed after the filling of the cavity 41 with the resin is completed, the cushion amount of the resin remains in the cylinder 30 even after the filling, and the cylinder 60 is kept. Since a hydraulic pressure slightly lower than that at the time of filling is continuously applied to the screw 31, the screw 31 continues to move forward at a low speed. After that, as the resin in the cavity 41 is solidified, the screw 31 further advances, and when the resin pressure eventually decreases, the pressure in the needle nozzle 32 decreases below a predetermined value, and the needle shaft 36 returns in the same manner as described above. The gate is closed. When the gate 3a is closed, the screw 31 rotates again to start the winding of the resin from the resin flow path 20. When the resin in the cavity 41 is completely cured, the mold opens and the ejector pin 42 ejects the molded product, and the cavity 41 is closed again and the state shown in FIG. 1 is restored.

As described above, according to this embodiment, since the molten resin is introduced while being wound into the toppede 3, the molten resin can be sucked and kneaded at the same time, and the temperature and the components of the resin can be made uniform. As well as
It is possible to smooth the flow of the resin in the resin flow path 20 and prevent the resin from staying. Therefore, thermal deterioration of the resin and unevenness in temperature and components can be avoided, and a high-quality molded product can be manufactured.

Further, since the screw 31 retracts as the resin is wound up, the screw 31
The amount of introduced resin can be known by detecting the amount of movement of the resin, and an accurate amount of resin can be delivered into the cavity 41. Moreover, since the injection pressure into the cavity 41 can be adjusted by the forward pressure of the screw 31, it is possible to set the molding condition with better controllability.

Since the molten resin is slowly introduced into the cylinder 30 from the resin flow path 20 by utilizing the solidification time and the removal time of the molded product, it is possible to flow the resin without reducing the specific volume of the resin. Therefore, it is possible to prevent the temperature rise due to the pressurization of the resin and the retention of the molten resin in the resin flow path 20. Further, the resin can be kneaded slowly within the above time, and the resin temperature and the uniformity of the components can be sufficiently enhanced.

In the above embodiment, the hydraulic pressure applied to the cylinder 60 is set for each of the above steps, so that the resin passage 2
Since it is possible to set conditions relating to the introduction amount, introduction speed or introduction pressure of resin from 0 to the cylinder 30 or from the cylinder 30 to the cavity 41, it is possible to optimize the molding conditions to retain the molten resin, The change can be prevented and the thermal deterioration of the resin can be avoided. Also, since the amount of resin injected into the cavity, the resin injection pressure, and the holding pressure value can be adjusted,
High-quality molded products can be manufactured.

This embodiment can be applied to any of the sprue hot type for heating only the sprue, the semi-hot type for heating a part of the runner, and the complete hot type for heating all of the sprue and runner.

[0029]

As described above, according to the present invention,
The molten resin is wound into the cylinder part by rotation of the screw member from the resin flow path and kneaded at the same time, and the resin is injected into the cavity from the cylinder part by the movement of the screw member. It is possible to reduce the amount of resin staying because it can be rolled up into the cylinder, and it is possible to make the resin temperature and resin material uniform by injecting resin from the cylinder part and kneading with the screw member. It is possible to manufacture a high-quality molded product.

[Brief description of drawings]

FIG. 1 is a sectional view of an internal structure of a mold showing an embodiment of an injection molding device according to the present invention.

2A and 2B are process diagrams (a) and (b) illustrating a molding process in the example, and an enlarged cross-sectional view (c) showing details of a backflow prevention ring.

[Explanation of symbols]

 2 manifold 3 topped 3a gate 4 template 20 resin flow path 21 heating heater 30 cylinder 31 screw 36 needle shaft 37 band heater 41 cavity 50 hydraulic motor 54, 55, 61 hydraulic pipe 60 cylinder

Claims (4)

[Claims] 1. An injection molding apparatus having a resin flow path for supplying a molten resin toward the inside of a cavity for molding a molded product, the gate being formed near the inlet of the cavity, and the resin flow path. A cylinder part connected between the cylinder part, a screw member housed inside the cylinder part so as to be rotatable about the axis and movable in the axis direction, and a rotation drive means for rotating the screw member.
An injection molding apparatus comprising: a moving unit that moves the screw member in the axial direction. 2. The injection molding apparatus according to claim 1, further comprising a backflow prevention mechanism that prevents a resin flow backflowing along the periphery of the screw member in the cylinder portion. 3. The injection molding apparatus according to claim 1, wherein a tip end of the cylinder portion is provided with gate opening / closing means for opening / closing the gate by increasing and decreasing a resin pressure. 4. The detecting device according to claim 1, further comprising a detecting means for detecting a moving amount of the screw member, and controlling the rotation driving means and / or the moving means according to the moving amount detected by the detecting means. The configured injection molding device.