JPH1158470A - Injection device and injection method of injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize the quality of a molded item by dwelling in a die using high-frequency vibration so that the pressure can be applied over the entire inside surfaces of the die. SOLUTION: In a preplasticizing injection molding device in which a resin is plasticized by rotating a screw 14 and the resin, in a molten state, is sent to a front chamber 24 of a plunger 22 and the plunger 22 is advanced to inject the molten resin into a die, there are provided a magnetostrictor 36 attached to a member which is directly attached to a portion of the plunger 22 or connected thereto to transmit a linear motion, and magnetic field generating means 40, 41 to generate vibration energy in the magnetostrictor 36.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection apparatus and an injection method for an injection molding machine, and more particularly to an injection molding machine for an injection molding machine in which pressure is distributed to all corners of a cavity by maintaining a high-frequency fluctuation. The present invention relates to an apparatus and an injection method.

[0002]

2. Description of the Related Art In an injection molding machine, when an injection step of injecting a molten resin into a cavity in a mold is completed, the process proceeds to a pressure-holding step. In this pressure-holding step, the state in which the injection pressure is applied is maintained until the molten resin in the mold is cooled and reaches a certain hardness. This is to improve the quality of the molded product. If sufficient injection pressure and holding pressure are not applied, the molded product is liable to sink.

In the pressure-holding step, the pressure is gradually reduced as the molten resin cools and becomes harder. However, simply maintaining a constant pressure at each stage may not provide a uniform pressure to the end of the cavity.

Japanese Patent Application Laid-Open No. Hei 2-182426 discloses a technique for maintaining the pressure while applying a slight vibration to the molten resin as a countermeasure for spreading the holding pressure to every corner of the cavity.

[0005]

In the above prior art, in order to apply fine vibration to a resin filled in a cavity, a servo motor for driving a screw is superimposed on a pressure command signal for applying a holding pressure to a servomotor. A sine wave signal of about 100 Hz is applied, whereby a reciprocating motion is superimposed on the rotor of the servomotor at a predetermined minute angle around the point where the angle corresponding to the pressure command signal is rotated. As a result, the holding pressure is changed up and down around the set value.

However, in the above prior art, since vibration is directly generated by mechanical movement, the vibration frequency is low, and depending on the size and shape of the molded product, the pressure may reach every corner of the cavity during the pressure holding process. There was a problem that was not spread.

In addition, since the servomotor is controlled, it is difficult to control the applied vibration, and the vibration state varies.
There was also a problem that the quality of the molded product was not stable.

Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art and to stabilize the quality of a molded product by maintaining a pressure so that pressure is distributed to every corner of the cavity. An object of the present invention is to provide an injection device and an injection method for an injection molding machine.

[0009]

In order to achieve the above object, a first injection device according to the present invention plasticizes a resin by rotating a screw, sends molten resin to a front chamber of a plunger, and transmits the molten resin to the plunger. In a pre-plasticity injection device for injecting a molten resin into a mold by advancing, a magnetostrictive body attached directly to a part of the plunger or attached to a member that transmits linear motion by being connected to the plunger,
Magnetic field generating means for generating vibration energy in the magnetostrictive body.

A second injection device according to the present invention is an in-line injection device for plasticizing resin by rotating a screw and injecting molten resin accumulated in front of the screw into a mold by advancing the screw. And a magnetic field generating means for generating vibration energy in the magnetostrictive body, the magnetostrictive body being mounted directly on a part of the device or being connected to a screw and transmitting a linear motion.

In a first injection method according to the present invention, the rotation of the screw plasticizes the resin, sends the molten resin to the front chamber of the plunger, and injects the molten resin into the mold by advancing the plunger. After completion, the injection pressure of the molten resin is held by the plunger, a high-frequency fluctuating magnetic field is applied to the magnetostrictive body directly or indirectly attached to the plunger, and vibration energy generated in the magnetostrictive body is transmitted from the plunger to the molten resin. The holding pressure is performed while applying high frequency vibration to the molten resin.

In a second injection method according to the present invention, the resin is plasticized by rotation of the screw, and molten resin accumulated in front of the screw is injected into a mold by advancement of the screw. Holding the injection pressure of the molten resin, applying a high-frequency varying magnetic field to the magnetostrictive body directly or indirectly attached to the screw, transmitting vibration energy generated in the magnetostrictive body from the screw to the molten resin, The pressure is maintained while applying vibration.

According to the present invention configured as described above,
Using the magnetostrictive body as a vibration energy source, the generated vibration energy can be directly propagated to the plunger or screw, and the vibration can be transmitted to the molten resin filled in the mold while applying the holding pressure with the plunger or screw. . Therefore, during the pressure-holding step, high-frequency vibration pressure-holding is obtained, and the pressure propagates to every corner of the mold, so that the quality of the molded product can be stabilized.

When a giant magnetostrictive material is used as the material of the magnetostrictive body, a large amount of magnetostriction can be obtained in addition to being able to be driven at a low voltage.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an injection apparatus and an injection method for an injection molding machine according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows an embodiment in which the present invention is applied to a pre-plastic injection device. Reference numeral 10
Denotes a plasticizing portion of the molding material, and 12 denotes a metering / injection portion. The plasticizing section 10 will be described.
In the case of 0, the servo motor 13 is used as a drive source of the screw 14. The rotation of the servo motor 13 is controlled by a belt,
The power is transmitted to the shaft 16 via a transmission mechanism 15 including a pulley. Since the shaft 16 is connected to the rear end of the screw 14 rotatably inserted in the barrel 17, the rotation of the servomotor 13 acts as the rotation of the screw 14.

A heater 18 is mounted outside the barrel 17, and the barrel 17 is heated by the heater 18. The resin of the molding material is put into the barrel 17 from the hopper port 19 and is plasticized by the rotating screw 14.

As the screw 14 rotates, the molten resin is transferred to the tip of the screw 14 and supplied from the passage 20 to the metering / injection unit 12. In the metering / injection section 12, a front chamber 24 in which the molten resin that has passed through the passage 20 accumulates is formed in the sleeve 23 in which the plunger 22 fits. A nozzle 25 is mounted on the front end of the sleeve 23.

The plunger 22 moves forward and backward using a servomotor 26 for injection as a drive source. The rotational movement of the servomotor 26 is transmitted to a ball screw shaft 28 via a transmission mechanism 27 including a belt and a pulley. A nut 29 is screwed onto the ball screw shaft 28, and the rotational motion of the ball screw shaft 28 is converted into a linear motion of the plunger 22 via the nut 29. This nut 2
9 is connected to the plunger 22 via a coupling 30 and a load cell 32. During the weighing process, the back pressure applied to the retreating plunger 22 is detected by the load cell 32, and the magnitude of the rotational torque of the servomotor 26 is controlled so that the back pressure becomes a set value.

The position of the plunger 22 is controlled by a position detector such as an encoder, which feeds back a position signal based on the rotation angle of the servo motor 26, and is controlled by a servo control unit (not shown) so as to follow the command position. Has become.

Next, FIG. 2 shows a measuring / injection section 1 of the injection apparatus.
FIG. 2 is an enlarged view of FIG. With reference to FIG. 2, the magnetostrictive body and the magnetic field generating means directly connected to plunger 22 will be described.

A short rod-shaped magnetostrictive body 36 is connected to the rear end of the plunger 22 coaxially with the plunger 22 by screw connection. This magnetostrictive body 36 is
7. It is connected to the load cell 32 via the joint 38.

The material of the magnetostrictive body 36 is a giant magnetostrictive material. This giant magnetostrictive material is a material having a large magnetostriction of several thousands ppm which is much larger than the conventional magnetostrictive material. A typical composition is 1: 2 in the atomic ratio of the rare earth element R to iron Fe. As giant magnetostrictive materials available on the market,
ETREMA TERFENOL-D (registered trademark) and the like.

The magnetostrictive body 36 made of such a giant magnetostrictive material
, A magnetic coil 40 is arranged on the outer peripheral side, and a magnetic bias 41 is further arranged outside the magnetic coil 40. The magnetic bias 41 is for expanding the linear range of the magnetostriction of the magnetostrictive body 36 with respect to the strength of the magnetic field generated in the magnetic coil 40. The magnetic coil 40 and the magnetic bias 41 are held by a case 42, and constitute an integral actuator that converts magnetic energy into vibration together with the magnetostrictive body 36.

A magnetic field is generated in the magnetic coil 40 by being energized from a power supply (not shown), and the strength of the magnetic field at that time is controlled by a driver or controller (not shown) to apply a high-frequency current within a predetermined frequency range to the magnetic coil 40. It can be changed by flowing it.

Next, a description will be given of an injection method performed using the injection apparatus having the above-described configuration. In FIG. 2, first, the screw 14 is rotated to plasticize the resin. When the rotating screw 14 plasticizes the resin in the barrel 17, the molten resin is transferred to the front chamber 24 of the plunger 22 through the passage 20 by the rotation of the screw 14. When the front chamber 24 is filled with the molten resin, the resin pressure starts to increase. This resin pressure acts as a force for retracting the plunger 22.

In order to perform weighing, the plunger 22 is retracted while applying a predetermined back pressure. Plunger 22
However, the measurement is completed at the time when the plunger 22 is retracted by a preset stroke, and the position of the plunger 22 is maintained. Further, the rotation of the screw 14 is stopped.

Next, the process proceeds to the injection step, where the servo motor 2
6 is rotated to advance the plunger 22. The molten resin accumulated in the front chamber 24 by the advancing plunger 22 is injected from a nozzle 25 into a cavity in a mold (not shown). The fact that the cavity is filled with the molten resin during the filling is detected from the position of the plunger 22. Immediately after receiving the signal indicating the completion of filling, a holding pressure is applied to the molten resin in the cavity.

That is, when the filling is completed, the plunger 22
And a current is applied to the magnetic coil 40 and the magnetic bias 41 to generate a magnetic field. A high-frequency current having a predetermined frequency is passed through the magnetic coil 40. Magnetic coil 40
Since the magnetic field generated by the magnetic field fluctuates at a high frequency, displacement distortion occurs in the magnetostrictive body 36 receiving this magnetic field. This displacement distortion changes when the strength of the magnetic field is large, and fluctuates small when the strength of the magnetic field is small.

The vibration energy generated in the magnetostrictive body 36 in this manner can be directly transmitted to the plunger 22 and transmitted to the molten resin filled in the mold.
Therefore, during the pressure-holding step, the high-frequency vibration is held, and the pressure propagates to every corner of the mold, and the quality of the molded product can be stabilized.

Further, since a giant magnetostrictive material is used for the magnetostrictive body 36, much larger magnetostriction can be obtained and a low voltage can be obtained as compared with the case where a piezoelectric material or a conventional magnetostrictive material is used as a vibration source. Can be driven.

In the above-described embodiment of the pre-plastic injection device, the magnetostrictive body 36 is directly connected to a part of the plunger 22, but the position where the magnetostrictive body 36 is connected is not limited to this. Any member may be used as long as it is a member that transmits a linear motion.

Next, an embodiment in which the present invention is applied to an in-line injection device will be described with reference to FIG. In FIG. 3, reference numeral 50 denotes a screw for melting the resin and injecting the molten resin. Reference numeral 51 denotes a servomotor that drives the screw 50 to rotate. This servo motor 51
Is transmitted to the rotating shaft 53 via a transmission mechanism 52 composed of a belt and a pulley. Since the rotating shaft 53 is connected to the rear end of the screw 50 inserted rotatably in the barrel 54,
Rotates as the screw 50 rotates.

A heater is mounted on the outer periphery of the barrel 54. The resin is put into the barrel 54 from the hopper 55 and is plasticized by the rotating screw 50.

The molten resin is transferred toward the front as the screw 50 rotates. The molten resin accumulated in front of the screw 50 is injected from the nozzle 55 into the mold as the screw 50 advances.

The driving source for this injection is the servo motor 56. The rotational motion of the servomotor 56 is transmitted to the rotating shaft 58 via a transmission mechanism 57 including a belt and a pulley. A ball screw shaft 59 is connected to the rotation shaft 58. A nut 60 is screwed onto the ball screw shaft 59. The nut 60 has a structure integral with a housing 61 of a bearing that supports a rotating shaft 53 connected to the screw 50. The rotating motion of the ball screw shaft 59 is converted into a motion for moving the entire front portion straight from the nut 60. Is done.

In this in-line type injection device, the short rod-shaped magnetostrictive body 36 is mounted between the rotating shaft 58 and the ball screw shaft 59 which transmits linear motion to the screw 50, and is coaxial with the screw 50. It has been incorporated. The use of a giant magnetostrictive material for the magnetostrictive body 36 is the same as in the case of the pre-plastic injection device of FIG.

The magnetostrictive body 36 has, on its outer peripheral side,
A magnetic coil 40 and a magnetic bias 41 outside the magnetic coil 40 are arranged. The magnetic coil 40 and the magnetic bias 41 are held by a case 42, and the same components as those in the embodiment of FIG. 2 are incorporated. The connection position of the magnetostrictive body 36 may be directly connected to the rear end of the screw 50.

Next, a description will be given of an injection method which is carried out using the in-line type injection apparatus having the above-described configuration. First, the screw 50 is rotated to plasticize the resin, and the molten resin is transferred to the front of the screw 50. When the molten resin has accumulated, the screw 50 is retracted while applying a predetermined back pressure to the screw 50 for measurement. Screw 50
However, when the meter is retracted by a preset stroke, the weighing is completed, and the rotation of the screw 50 is stopped while the position of the screw 50 is maintained.

Next, in the injection step, the screw 50 is advanced by rotating the servomotor 56. The molten resin accumulated by the advancing screw 50 is injected from a nozzle 55 into a cavity in a mold (not shown). During this filling, the fact that the cavity was filled with the molten resin was confirmed by screw 5
0, the screw 50
And a current is applied to the magnetic coil 40 and the magnetic bias 41 to generate a magnetic field. A high-frequency current having a predetermined frequency is passed through the magnetic coil 40.

The vibration energy generated by the magnetostrictive body 36 propagates to the ball screw shaft 59, the rotating shaft 53, and the screw 50 which are connected coaxially, and can be transmitted to the molten resin while maintaining the pressure by the screw 50. Therefore, during the pressure-holding step, the high-frequency vibration is held, and the pressure propagates to every corner of the mold, and the quality of the molded product can be stabilized.

[0041]

As is apparent from the above description, according to the present invention, the generated vibration energy is transmitted directly to the plunger or screw using the magnetostrictive body as the vibration energy source. The high-frequency vibration can be transmitted to the molten resin filled in the mold while applying the holding pressure, and the pressure can propagate to every corner of the mold, and the quality of the molded product can be stabilized. .

By using a giant magnetostrictive material for the material of the magnetostrictive body, in addition to being able to be driven at a low voltage, a larger amount of magnetostriction can be obtained, and sufficient high frequency vibration necessary for holding pressure can be given to the molten resin. Becomes possible.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment in which the present invention is applied to a pre-plastic injection device.

FIG. 2 is a cross-sectional view showing a measuring / injection section in detail in the pre-plastic injection apparatus of FIG.

FIG. 3 is a cross-sectional view showing another embodiment in which the present invention is applied to an in-line injection device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Plasticization part 13 Servo motor 14 Screw 17 Barrel 18 Heater 22 Plunger 24 Front room 26 Servo motor 28 Ball screw shaft 29 Nut 36 Magnetostrictive body 40 Magnetic coil 41 Magnetic bias 50 Screw 59 Ball screw shaft 60 Nut

Claims (6)

[Claims] 1. A pre-plasticization type injection device for plasticizing resin by rotation of a screw, sending molten resin to a front chamber of a plunger, and injecting the molten resin into a mold by advancing the plunger. An injection apparatus comprising: a magnetostrictive body directly attached to a member that transmits a linear motion by being connected to a plunger; and a magnetic field generating unit that generates vibration energy in the magnetostrictive body. 2. An in-line type injection device for plasticizing resin by rotation of a screw and injecting molten resin accumulated in front of the screw into a mold by advancing the screw, wherein the injection resin is directly attached to a part of the screw, or An injection apparatus, comprising: a magnetostrictive body attached to a member that transmits linear motion by being connected to a magnetic field; and a magnetic field generating unit that generates vibration energy in the magnetostrictive body. 3. The injection apparatus according to claim 1, wherein the magnetostrictive body is made of a giant magnetostrictive material. 4. The resin is plasticized by rotation of the screw, the molten resin is sent to the front chamber of the plunger, and the molten resin is injected into the mold by advancing the plunger. After the injection is completed, the injection pressure of the molten resin is set by the plunger. And applying a high-frequency fluctuating magnetic field to the magnetostrictive body directly or indirectly attached to the plunger, transmitting vibration energy generated in the magnetostrictive body from the plunger to the molten resin, and applying high-frequency vibration to the molten resin to maintain the molten resin. An injection method for an injection molding machine, comprising performing pressure. 5. The plasticization of the resin by the rotation of the screw, the molten resin accumulated in front of the screw is injected into the mold by the advance of the screw, and after the injection is completed, the injection pressure of the molten resin is maintained by the screw. Applying a magnetic field having a high frequency fluctuation to a magnetostrictive body attached directly or indirectly to a screw, transmitting vibration energy generated in the magnetostrictive body to the molten resin from the screw, and performing pressure holding while applying high-frequency vibration to the molten resin. Characteristic injection method of injection molding machine. 6. The injection method for an injection molding machine according to claim 4, wherein a magnetostrictive body made of a giant magnetostrictive material is used as the magnetostrictive body.