JPH03219935A - Injection molding method and injection device - Google Patents

Abstract

PURPOSE:To prevent a reinforced fiber from breaking, by a method wherein a large cylinder for measurement is arranged on a position separated from a screw fitting position, an injection plunger which is fitted into the large cylinder is made into a hollow plunger having a through hole, the inside of which is made a flow path for raw materials and the flow path is made interruptible between the hollow plunger and a screw. CONSTITUTION:Molding raw materials comprised of plastic and a reinforced fiber is pressed into a small cylinder 6 from a pressing-in cylinder 18 by a pressing-in piston 20, the plastic is molten with a rotation of a screw 8 in the small cylinder 8 and the molding raw materials are kneaded. The molding raw materials are fed to the hollow plunger 4 connecting with the small cylinder 6 and measured and sent into a large cylinder 2 which is fitted over the hollow plunger 4. The hollow plunger 4 is moved in the direction where measure capacity is increased with this measurement action, after completion of the measurement, a rotation of the screw 8 is suspended and the screw 8 is brought into contact with the hollow plunger 4, through which raw material flow path is interrupted.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to an injection acid injection method and an injection apparatus.

(b) Conventional technology Fiber-reinforced resin (usually abbreviated as FRP), which is made by mixing fibers with high impact strength such as glass fibers into plastic, can improve the disadvantages of plastics that are weak in impact, so it can be used for helmets, etc. It is used in applications that require light weight and impact strength. For example, when glass fiber is used as the reinforcing fiber for FRP, the fiber is 14.7 to 25.
It is a long fiber of 4mm (0.5~1°゛), and also has FR
As the plastic for P, for example, unsaturated polyester resin is used. In the molding process of FRP, an important step is to disperse and knead the reinforcing fibers mixed into the plastic so as not to cut them. This makes it possible to fully utilize the impact strength of the reinforcing fibers.

Among the various FRP molding methods, press molding and injection molding are relatively popular.Press molding has the advantage of producing products with high impact strength because fewer fibers are cut, but the material The disadvantages are that there is a lot of loss, it is difficult to automate, the molding speed is slow, and it takes about four times as long as injection molding.On the other hand, injection molding has the advantage of being easy to automate and short molding time. As will be described later, there is a problem in that sufficient impact strength cannot be obtained because the reinforcing fibers are easily cut.Figures 4 and 5 show the injection device of a conventional injection molding machine for FRP. This is a so-called in-line screw type in which a screw 50 is fitted into a cylinder 52 for rotation and reciprocation, and a backflow prevention ring 54 is provided at the tip of the screw 50.Backflow prevention ring 54 has a structure that can prevent the resin from flowing back from the left to the right at a position in the screw groove that is in contact with the flight part 50a on the right side of the illustrated position. The devices are connected.BMC (bulk molding compound = large molding resin composition)
, TMC (thick molding compound = resin composition for molding thick materials) and SMC (sheet molding compound = resin composition for sheet molding) and other FRP resin raw materials are supplied into the cylinder 52 due to so-called biting. Therefore, the material is supplied together with the reinforcing fiber raw material onto a push cylinder 60 by an automatic material supply device 58, and is pushed into the cylinder 52 by a push piston 62. A nozzle 64 is provided on the left end side of the cylinder 52 in the figure, and this injection device A is fixed on a movable table 66. By moving the moving table 66 to the left in the figure, it is possible to press the nozzle 64 against the opening 68a of the mold 68.

In the step of measuring the molten resin, the screw 50 rotates and sends the molten resin to the metering chamber 56 provided in front of the screw 50, and the resin pressure in the metering chamber 56 causes the screw 50 to gradually retreat to the right in the figure. At this time, the backflow prevention ring 54 is located at the left position in the miso so as not to interfere with the transfer of the resin. The resin mixed with reinforcing fibers is transferred to the measuring chamber 56 through such a narrow gap. When the measurement is completed, the injection process begins, the rotation of the screw 50 is stopped, and the moving table 66 is moved to the left to inject the nozzle 64.
is pressed against the opening 68a of the mold 68. screw 5
The screw 50 is moved forward by driving a forward/backward movement device (not shown) connected to the molten resin connected to the meter 0, and the molten resin in the metering chamber 56 is injected into the mold 68 through the nozzle 64. At this time, the backflow prevention ring 54 is located at the right position in the groove to prevent the resin from flowing back from the metering chamber 56 through the groove of the screw 50 to the right side in the figure. The resin injected into the mold 68 is cooled and the molded product is taken out.

Next, the injection molding machine shown in FIG. 5 will be explained. Fourth
Fitted within the hollow plunger 72 is a rotatable screw 70 fitted with a backflow prevention ring 54 of the same construction as shown. The hollow plunger 72 is
It is integrally fixed to a cylinder 74 having a collar 74a at its end. A push piston 62 and a push cylinder 60 are attached to the cylinder 74 .

The outer diameter portion of the hollow plunger 72 is slidably fitted into a large cylinder 76 having a collar 76a.

A measuring chamber 80 defined by the tip 70a of the screw 70 and the tip 72a of the hollow plunger 72 is formed inside the large cylinder 76 where the nozzle 78 is provided on the left end side in the figure. A fluid pressure cylinder 82 is attached to the collar 74a of the small cylinder 74, and the rod 82 of this cylinder
a is connected to the collar 76a of the large cylinder 76. This allows the screw 70 and hollow plunger 72 to reciprocate without changing their relative axial positions, unlike that shown in FIG. Note that the large cylinder 76 is attached to a moving table (not shown).

In the process of measuring molten resin, the screw 70 rotates and transfers the molten resin to the measuring chamber 80 in front of the screw 70.
The hollow plunger 72 and screw 70 gradually retreat to the right in the figure due to the resin pressure.

At this time, the backflow prevention ring 54 is located at the left position within the groove so as not to interfere with the transfer of the resin. The resin mixed with reinforcing fibers is transferred to the measuring chamber 80 through such a narrow gap. When the measurement is completed, the injection process begins, and the rotation of the screw 70 is stopped, and a moving table (not shown) is driven to advance the large cylinder 76 to the left, and the nozzle 78 is pressed against the opening of the mold (not shown). By applying fluid pressure to the right chamber of the fluid pressure cylinder 82, the small cylinder 74.
The hollow plunger 72 and screw 70 are advanced to the left. At this time, the backflow prevention ring 58 prevents the resin from reaching the measuring chamber 80.
It is located at the right position in the groove so that it does not flow backward through the groove of the screw 70 to the right side in the figure. Molding is performed by injecting resin into a mold.

(c) Problems to be Solved by the Invention However, in the conventional injection device for FRP as described above, plastic containing long reinforcing fibers passes through the narrow gap of the screw equipped with the backflow prevention ring. The problem is that it is sent to the weighing room. For this reason, the reinforcing fibers are easily cut during the measuring process (reducing the impact strength of the molded product).In addition, the reinforcing fibers may become entangled with the backflow prevention ring, which not only hinders its operation. Since the backflow prevention ring is worn out, there is a problem with the durability of the injection device.Furthermore, due to these structures, it is necessary to increase the effective length (L) of the screw, and the ratio (L) to the screw diameter (D) /D) is as large as 7 to 14. Therefore, the reinforcing fibers within the screw are easily damaged.Furthermore, in the structure shown in Fig. 4, the fitting length of the screw with respect to the cylinder during the metering process. There is also the problem that non-uniformity in kneading cannot be avoided because the length gradually becomes shorter.On the other hand, in the structure shown in Fig. 5, the cylinder part and the hollow plunger are doubled, and Since the screw is fitted into a hollow plunger, the screw diameter tends to be small, and the reinforcing fibers are bent with a small radius of curvature during cross-wiring and metering, which can easily damage the reinforcing fibers. There is this problem.The present invention aims to solve this problem.

(d) Means for Solving the Problems The present invention arranges a large measuring cylinder at a position away from the screw mounting position, and replaces the injection plunger fitted in the large cylinder with a hollow plunger having a through hole. The above problem is solved by making the inside of this a flow path for the raw material and making it possible to shut off the flow path between the hollow plunger and the screw. That is, in the injection molding method of the present invention, a molding material made of plastic and reinforcing fibers is pushed into a small cylinder (6) from a push cylinder (18) by a push piston (20), and a screw ( 8) melts the plastic and kneads the molding raw material, sends the molten plastic molding raw material to the hollow plunger (4) connected to the small cylinder (6), and the large cylinder fitted with the hollow plunger (4). (2), the hollow plunger (4) is moved in the direction of increasing the measured volume by this measuring operation, and after the measurement is completed, the rotation of the screw (8) is stopped and the screw (8) and the hollow plunger are (4
) to block the raw material flow path, and then, while maintaining this state, the hollow plunger (4) is operated in the injection direction to inject the molding raw material, and the above method The injection device for carrying out the above includes a large cylinder (2) having a nozzle part (2a) at the tip and a measuring chamber (2b) inside the tip side, and a large cylinder (2) that is movably fitted into the cylinder and extends in the axial direction. A hollow plunger (4) having a through hole, a small cylinder (6) that is integrally attached to one end of the plunger, a screw (8) that is slidably and rotatably fitted into the plunger, and a motor that rotates the plunger (8). 12), a first fluid pressure cylinder (14) attached to this, a second fluid pressure cylinder (16) attached to the large cylinder (2), a pushing cylinder (18) provided to the small cylinder (6), and Push piston (2
0), and the hollow plunger (4) has:
The inner diameter is smaller than that of the small cylinder (6), and a tapered hole (4a) is provided at the end of the small cylinder (6). ) is provided with a tapered shaft portion (8a) that can close the rod (14a) of the first fluid pressure cylinder (14).
) is attached to the end of the small cylinder (6) opposite to the hollow plunger (4), and the rod (16a) of the second hydraulic cylinder (16) is attached to the hollow plunger (4). It is characterized by being attached. The screw (8) preferably has a value (L/D) of 3 to 4, which is the effective length (L) divided by the diameter (D). Note that the symbols in parentheses indicate corresponding members in the embodiment.

(e) Working The FRP raw material mixed with plastic and reinforcing fibers is pushed from the push cylinder into a small cylinder that is externally heated by the push piston. The screw in the small cylinder is positioned in a retracted position by the first hydraulic cylinder and rotates away from the tapered bore of the hollow plunger. That is, the inner diameter portion of the small cylinder and the inner diameter portion of the hollow plunger are in communication. Here, the FRP raw material has an L/D of 3 to 4 compared to the usual 7 to 14.
It is melted and kneaded by the rotation of a screw with extremely small, thick and deep grooves. As a result, the molten plastic FRP raw material is kneaded to a predetermined degree while preventing the reinforcing fibers from being damaged. The molten resin is sent from the tip of the screw into the hollow plunger, and then into the metering chamber of the large cylinder. Along with this movement, the hollow plunger gradually retreats as if being pulled out of the large cylinder.
When the completion of metering is detected, the motor stops and the screw rotation stops. Subsequently, the first hydraulic cylinder is actuated to advance the screw so that its tapered shaft abuts the tapered hole of the hollow plunger. The nozzle portion is pressed against the mold, and then the hollow plunger is advanced by the pressure of the second fluid pressure cylinder, and the molten resin is injected into the mold.

As a result, an FRP injection molded product with high impact strength and less damage to reinforcing fibers can be obtained.

(F) Embodiment Figures 1 and 2 show an embodiment of the present invention. The large cylinder 2 arranged as an end member of the injection device is provided with a nozzle part 2a with a thin hole at the end.
A measuring chamber 2b having a tapered hole shape is provided inside the a side. The hollow plunger 4, which is slidably fitted into the large cylinder 2, is provided with a through hole 4b in the axial direction.
A tapered hole 4a is provided at the end of this opposite to the measuring chamber 2b. The measuring chamber 2b can be heated by a heating section (not shown). A collar portion 4c is provided outside the tapered hole portion 4a. A small cylinder 6 is integrally attached to one side of this. small cylinder 6
The inner diameter 6a of the hollow plunger 4 is larger than the through hole 4b of the hollow plunger 4, and a screw 8 is slidably and rotatably fitted into the through hole 4b. Screw 8 is L/D
It is thicker (usually 60-100mm) and has a groove depth of 13, which is significantly smaller than the usual 7-14.
It has a screw shape with a depth of ~25mm,
The compression ratio is also a low compression ratio of 1 to 1.2. At the end of the screw 8 facing the hollow plunger 4, a tapered shaft portion 8a having a conical shape is formed. The tapered shaft portion 8a can close the through hole 4b by abutting against the tapered hole portion 4a. That is, communication between the through hole 4b of the hollow plunger 4 and the inner diameter 6a of the small cylinder 6 can be cut off. The other end of the screw 8 is connected via a shaft joint 10 to a rotating shaft 12a of a motor 12 that rotates the screw. motor 12
Two first fluid pressure cylinders 14 are attached to the case 1.2b at the upper and lower positions in the figure, and the rod 14a of these is attached to the end of the small cylinder 6 on the opposite side from the hollow plunger 4 side. installed. On the other hand, the large cylinder 2 has two second fluid pressure cylinders 16 at the top and bottom positions in the figure.
It is attached to face the first fluid pressure cylinder 14, and its rod 16a is attached to the collar 4c of the hollow plunger 4. small cylinder 6
A pushing cylinder 18 is attached to the material supply port 8b of the pushing cylinder 18, and a pushing piston 20 is provided inside the pushing cylinder 18. The members attached to the hollow plunger 4 are movable in the left and right directions in the figure while maintaining their relative positions. In addition,
The large cylinder 2 and the second fluid pressure cylinder 16 are attached to a moving table (not shown), and the moving table can move the entire injection device in the left-right direction in the figure.

Next, the operation of this embodiment will be explained. FIG. 1 shows a state in which the cross-talk process is entered, and hydraulic pressure is supplied to the oil chamber 14b on the right side in the figure of the first fluid pressure cylinder 14, and the screw 8 is in the retreated position shown in the figure. As a result, the tapered shaft portion 8a of the screw 8 is located away from the tapered hole portion 4a of the hollow plunger 4, and the hollow plunger 40 through hole 4b and the inner diameter 6a of the small cylinder 6 are in communication. While driving the motor 12 to rotate the screw 8,
The push piston 20 is operated to push the FRP raw material mixed with plastic and reinforcing fibers housed in the push cylinder 18 into the small cylinder 6 which is externally heated.

The FRP raw material has an L/D of 3 to 4 compared to the usual 7 to 14.
The molten resin is melted and kneaded by the rotation of the screw 8 with a significantly smaller thick (and deep groove) and low compression ratio, and is made to a predetermined kneading degree while preventing the reinforcing fibers from breaking.Next, the molten resin is Hollow plunger 4 from the tip of 8
When the through hole 4b is filled, it is further sent to the measuring chamber 2b of the large cylinder 2.

Along with this operation, the hollow plunger 4 gradually retreats to the right in the figure so as to be removed from the large cylinder 2, and when it is detected that it has moved to the metering completion position shown in Figure 2, the motor 12 stops. Then, the screw 8 stops rotating. Subsequently, hydraulic pressure is introduced into the oil chamber 14c on the left side in the figure of the first fluid pressure cylinder 14 to advance the screw 8, and the tapered shaft portion 8 of the screw 8 is advanced.
a butt against the tapered hole 4a of the hollow plunger 4. Thereby, the communication between the through hole 4b of the hollow plunger 4 and the inner diameter 6a of the cylinder 6 is cut off, and it is possible to prevent the molten resin in the metering chamber 2b and the through hole 4b from flowing back to the right in the figure. The injection device is moved to the left in the figure by a moving device (not shown) to press the nozzle portion 2a of the large cylinder 2 against a mold (not shown), and then hydraulic pressure is applied to the oil chamber 16b on the right side in the figure of the second fluid pressure cylinder 16. The hollow plunger 4 is advanced in the injection direction to the left in the figure, and the molten resin in the measuring chamber 2b is injected into the mold. After the injection is completed, hydraulic pressure is introduced into the oil chamber 14b on the right side in the figure of the first fluid pressure cylinder 14 to retreat the screw 8 to the first illustrated position.
Now you can move on to the next crosstalk process.

(Test Results) Using the same FRP material, molding by press, injection molding by a conventional injection device, and injection molding by the device of the present invention were performed, and the results are shown in FIG. 3 for comparison. It can be seen that the impact strength of molded products made using the apparatus of the present invention is significantly improved compared to those made using the conventional injection apparatus.

(G) As described in detail, the present invention provides a molded product with less damage to reinforcing fibers and significantly higher impact strength than injection molded products made from FRP raw materials using conventional injection equipment. can be manufactured. Therefore, an injection molded product having a value close to the impact strength of a molded product formed by press molding can be manufactured in about 25% of the press molding time. Furthermore, since no backflow prevention ring is used, the injection device can have a long life. Furthermore, since the metering chamber can be provided at a location unrelated to the screw diameter, the inner and outer diameters of the hollow plunger and the metering stroke can be freely set.
It can easily meet demands for large-capacity molded products.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view showing the arrangement of the crosstalk process of an injection device according to an embodiment of the present invention, FIG. 2 is a vertical cross-sectional view showing the state of entering the injection process, and FIG. Comparison diagram between those tested using the conventional method and those tested using the conventional method, Part 4
The figure is a partial cross-sectional view of a conventional in-line screw type injection device, and FIG. 5 is a longitudinal cross-sectional view of another type of conventional injection device. 2...Large cylinder, 2a...Nozzle part, 2b...
Measuring chamber, 4...Hollow plunger, 4a...Tapered hole, 6...Small cylinder, 8...Screw 8a...
- Tapered shaft portion, 12... Motor, 14 - - First fluid pressure cylinder, 14a... Rod, 16... Second fluid pressure cylinder, 16a... Rod, 18... Pushing cylinder, 20 ...Pushing piston, D...(screw) diameter, L...(screw) effective length. Patent patent applicant Japan Steel Works, Ltd.

Claims (1)

[Claims] 1. A molding material made of plastic and reinforcing fibers is pushed into a cylinder (1) by a pushing piston (20).
8) into the small cylinder (6), and then press the small cylinder (
The plastic is melted and the molding raw material is kneaded by the rotation of the screw (8) in 6), and the molten plastic molding raw material is sent to the hollow plunger (4) connected to the small cylinder (6), and the hollow plunger (4) The metering operation moves the hollow plunger (4) in the direction of increasing the metering volume, and after metering is completed, the rotation of the screw (8) is stopped and the screw (8) and the hollow plunger (4) to block the raw material flow path, and then, while maintaining this state, the hollow plunger (4) is moved in the injection direction to inject the molding raw material. Characteristic injection molding method. 2. A large cylinder (2) having a nozzle part (2a) at its tip and a measuring chamber (2b) inside the tip side, and a hollow plunger (2) which is movably fitted into this and has a through hole in the axial direction. 4), a small cylinder (6) that is integrally attached to one end of this, a screw (8) that is slidably and rotatably fitted to this, a motor (12) that rotates this, and a motor (12) that is attached to this. a first fluid pressure cylinder (14) attached to the large cylinder (2) and arranged facing the first fluid pressure cylinder (14);
The hollow plunger (4) has an inner diameter smaller than the inner diameter of the small cylinder (6), and the hollow plunger (4) has a push cylinder (18) and a push piston (20) provided in the small cylinder (6). A tapered hole (4a) is provided at the side end of the cylinder (6), and the screw (8) has a tapered shaft (8) that can close the tapered hole (4a).
a), the rod (14a) of the first hydraulic cylinder (14) is attached to the end of the small cylinder (6) opposite to the hollow plunger (4), and An injection device characterized in that the rod (16a) of the fluid pressure cylinder (16) is attached to the hollow plunger (4). 3. The effective length (L) of the screw (8) is the diameter (
3. The injection device according to claim 2, wherein the value divided by D) (L/D) is 3 to 4.