JPS6325934B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to screw back pressure control of an injection device that drives an injection mechanism with an electric motor.

Injection molding machines that use an electric motor as a driving source for rotating the screw are already known, but even in this case, hydraulic pressure must be used to control the back pressure of the screw.

The present invention aims to provide a method and apparatus that can control the back pressure of the screw without using hydraulic pressure by converting the backward movement of the screw into rotational movement and controlling the rotational force with a brake device. It is something to do.

The present invention will be explained in detail below with reference to embodiments shown in the drawings.

In the figure, 1 indicates a mold clamping device, and 2 indicates an injection device. The mold clamping device 1 includes a tie bar 12 installed on a pair of fixed plates 10 and 11 on a machine stand 3, and a movable plate 13 movably attached to the tie bar 12. Molds 14, 14 are provided on opposing surfaces of the fixed plate 11 and the movable plate 13, respectively, and the movable plate 1
A screw shaft 15 is provided protruding from the opposite surface of 3. This screw shaft 15 is screwed into a rotary disk 16 that is rotatably attached to the other fixed plate 10, and the rotary disk 16
A gear 17 is attached to the movable plate 13, and when the rotary plate 16 rotates together with the gear 17, the screw shaft 15 moves together with the movable plate 13 by means of a screw lead.

The injection device 2 includes an injection heating cylinder 21 containing a screw 20 therein, and a housing 22 on the machine base that also serves to hold the injection heating cylinder 21. The housing 2
Inside the screw 2, there is a rear end portion of the screw 20, and a pair of support shafts 24 installed on both sides in parallel with the screw.
24, and a screw holding member 25 is attached to these support shafts 24, 24 so as to be slidable in the front and rear directions.

Further, an extension shaft 27 having a gear 26 is connected to the rear end of the screw 20, and the end of the extension shaft 27 is rotatably connected to the screw holding member 25.

Furthermore, a screw receiving member 28 provided at the rear of the screw holding member 25 has a shaft portion 3 rotatably held on the housing wall portion 22a and having a gear 29.
A screw shaft 30 integral with the housing wall 22a is screwed in, and the outer end of the shaft portion 30a is connected to a brake device 31 fixed to the housing wall portion 22a. This brake device 31 is equipped with a hysteresis brake inside.

This hysteresis brake consists of three parts: a field, a rotor, and a cup. When the field containing an excitation coil is magnetized by electricity and a magnetic field is generated between the rotor's inner and outer magnetic poles, the cup placed in the magnetic field also It is magnetized and has a structure in which the rotor and the cup are magnetically connected, and is commonly available on the market. 32 is a transmission shaft on the mold clamping device side, 33 is a transmission shaft on the injection device side, and the transmission shaft 32 is connected to the fixed platen 1 as shown in FIG.
It has a transmission gear 35 which is rotatably supported on the lower part of 0 and 11 and meshed with the gear 17 in the vicinity of the stationary platen 10. Further, the transmission shaft 32 is connected to a transmission shaft 36 via a joint 36a having a spline, and the transmission shaft 36 is connected to the transmission shaft 33 via an electromagnetically actuated clutch mechanism 34 so as to be able to move toward and away from the transmission shaft 33.

Further, the transmission shaft 33 is rotatably supported in the lower part of the housing 22 together with another transmission shaft 37, and on the transmission shafts 33 and 37 there are transmission gears 38 and 39 that mesh with the gears 26 and 29, respectively. A plurality of electromagnetically actuated clutch mechanisms 40 and 41 are provided for rotating and stopping the transmission shaft 3.
Servo motor 42 fixed to housing 22 at 7
are communicated via a drive belt 43.

Note that 44 and 45 are drive gears provided on the transmission shafts 33 and 37, 46 is a screw shaft for nozzle touch, and 4
7 is a clutch of the screw shaft 46.

In the example shown in FIG.
4a, 24a, screw receiving members 28, 28 are provided at both ends of the screw holding member 25, and screwed into the screw shafts 24a, 24a, respectively. Gears 29a, 29a that mesh with each other are provided, and the rotation of the gear 29 is transmitted to the support shafts 24, 24 via the gears 29a, 29a.
It has a structure that moves forward and backward together with the screw 20.

Next, the injection molding process will be explained.

With the transmission shafts 32 and 33 connected by the clutch mechanism 34, the servo motor 42 is rotated in the forward direction. At this time, on the injection device 2 side, the clutch mechanism 4
0 and 41 leave the transmission gears 38 and 39 free.

The rotary disk 16 is rotated by the transmission shaft 32, the transmission gear 35, and the gear 17, and the screw shaft 15 is sent out. As a result, the movable platen 13 moves forward to close the molds 14, 14, and further strong mold clamping is performed. When the mold clamping pressure reaches a predetermined pressure, the brake 48 is activated to fix the transmission shaft 32, and the clutch mechanism 3
4 to disconnect the transmission shaft 33.

Further, on the injection device side, the clutch mechanism 41 is operated in response to a command, and the transmission gear 39 is rotated together with the transmission shaft 33. As a result, the screw shaft 30 is rotated together with the gear 29, and the screw holding member 25 is advanced by the screw lead. This screw holding member 2
Since the extension shaft 27 at the rear end of the screw is supported on the screw 5, the screw 20 also moves forward together to perform injection.

When the injection is completed, the servo motor 42 is stopped in response to a command, and at the same time, the clutch mechanism 41 is actuated to disconnect the gear 39. Next, clutch mechanism 4
0 operates to rotate together with the transmission gear 38 and the transmission shaft 37. And again the servo motor 42
When the screw rotates in the opposite direction, the screw 20 rotates and the material is transferred. The backward force generated in the screw 20 due to the transfer of the material generates a rotational force in the screw shaft 30 through the screw holding member 25 in a direction opposite to that when the screw moves forward.

At the same time, the brake device 31 is activated, and the screw shaft 3
By applying a braking force to the 0, material is measured while generating so-called screw back pressure.

After weighing, the mold clamping mechanism turns on the electromagnetic brake 4.
8 is released, the clutch mechanism 34 is operated, and the transmission shaft 32 is connected to the transmission shaft 33 again. Further, by rotating the servo motor 42 in the reverse direction, the screw shaft 15 rotates in the reverse direction to open the mold, completing one cycle of injection molding. In addition, 15, 24a,
A ball screw is used for each of the 30 screw shafts in view of transmission efficiency.

In the above embodiments, a hysteresis brake was used as a brake device for controlling rotational force. However, this brake device may be of any type suitable for torque control that can be used in a stationary or nearly stationary state, such as a hysteresis brake. Motors, servo motors, torque motors, etc. can also be used.

As described above, this invention converts the backward movement of the screw caused by the charge of the molding material accompanying the rotation of the screw into a rotational motion and controls the rotational force, so that the following can be achieved. be effective.

1 The back pressure of the screw can be adjusted without using hydraulic pressure, making it possible to create a molding machine that does not use hydraulic pressure at all.

2 By using a hysteresis brake, etc., it is possible to control the rotational force without being affected by changes in the rotational speed due to the backward speed of the screw, and the back pressure can be controlled arbitrarily and precisely, resulting in uniform resin production. of kneading is obtained.

3. The brake can be used for holding pressure during injection filling.
Furthermore, the rotating shaft (screw shaft) can also be used as a driving shaft for advancing injection, which is rational.

4. By using an electromagnetic brake, it is easy to control the braking force, and it is also possible to perform complex control such as changing the back pressure as the screw retreats.

[Brief explanation of the drawing]

The drawings show an apparatus used to carry out the control method according to the present invention. Fig. 1 is a side view of an injection molding machine, Fig. 2 is a cross-sectional plan view of the injection device, and Fig. 3 is a longitudinal cross-section of the housing part. 4 is a cross-sectional plan view of the lower portion of the housing, FIG. 5 is a cross-sectional plan view of another embodiment of the injection device, and FIG. 6 is a vertical cross-sectional view of the housing portion of FIG. 5. 1...Mold clamping device, 2...Injection device, 20...Screw, 26...Gear, 27...Extension shaft, 31...
...brake device, 42...servo motor.

Claims (1)

[Scope of Claims] 1. A screw back of an injection device characterized in that the backward movement of the screw caused by the charge of molding material accompanying the rotation of the screw is converted into a rotational motion and the rotational force thereof is controlled. Pressure control method. 2. An extension shaft that is integrally connected to the rear end of the screw, has a gear that applies rotational force to the screw, and whose shaft end is rotatably connected to the screw holding member, and a pair of support shafts that are installed in the housing. the screw holding member which is provided to be movable forward and backward; a screw shaft which moves together with the screw holding member and which converts the backward movement of the screw into rotational movement; and a screw shaft which communicates with the shaft of the screw shaft and which moves the screw holding member. A back pressure control device for an injection device consisting of a brake device that controls the rotational force of the shaft.