JPH0470128B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mold clamping device for a molding machine using an electric motor as a driving source.

A mold clamping device consists of a rotating member in a fixed position, a screw shaft for mold clamping that is screwed into the rotating member and whose tip is connected to a movable platen, and a member that transmits the rotational force of an electric motor to the rotating member. Already known.

However, the electric motor used there is an induction motor, and the speed and torque cannot be controlled by itself, so a reduction gear is used to switch the rotational speed. In addition, speed control is limited to the speed according to the reduction ratio of the reducer used, and the rotational inertia is large and responsiveness is poor. It was considered inappropriate as a driving source for the required mold clamping device.

In addition, since the screw shaft used there is a sliding screw, there is a large rotational resistance and a problem with response.As for the mold clamping force, it is not possible to continue energizing under overload conditions, so there is no special method. Since the position of the movable platen is controlled by a limit switch, the setup is complicated, such as having to adjust the position every time the mold is changed, and there are issues that need to be improved in terms of control accuracy and holding force. It was hot.

This invention uses a servo motor as the electric motor, which can obtain a very large torque when rotating at low speed, has a high torque inertia ratio, has good responsiveness, and has a wide variable speed range, and also drives the electric motor by improving the screw shaft. This is an attempt to solve the problems that arise when using a computer as a source.

In addition, this invention can control the amount of movement of the movable plate and the closing position of the mold by detecting the amount of rotation of the servo motor, thereby solving the problem of control when using a limit switch, etc., and controlling the mold in stages. It is an object of the present invention to provide a mold clamping device that can perform injection compression molding, injection foam molding, etc. that require control of the closed position.

The present invention is characterized by a rotating member in a fixed position, a screw shaft for mold clamping that is screwed onto the rotating member and whose tip is connected to a movable platen, and transmitting the rotational force of an electric motor to the rotating member. In the mold clamping device, the rotary member and the screw shaft are screwed together through balls, and the electric motor is a servo motor, and the servo motor detects the amount of rotation of the servo motor to control the movable platen. A rotation amount detector is provided to control the amount of movement and the closed position of the mold.

The present invention will be explained in detail below using illustrated examples.

The mold clamping mechanism 1 includes a pair of fixed plates 10 and 11 provided facing each other on the machine stand 3;
The required number of tie bars 1 were constructed over 11
2, 12, and a movable platen 13 movably attached to the tie bars 12, 12. A fixed mold 14a and a movable mold 14b are provided on the opposite surfaces of the fixed plate 11 and the movable plate 13, respectively, and on the opposite surface of the movable plate 13, a screw groove 15 is provided on the outer peripheral surface.
A screw shaft 15 for mold clamping marked a is connected.
This screw shaft 15 is inserted into a nut-shaped bearing member 18 of a rotary cylinder 17, which is a rotating member in a fixed position, which is rotatably inserted into the fixed platen 10 using a ball bearing 16. A large number of balls 19, 19 in a spiral groove provided on the inside and the threaded groove 15
When the rotary cylinder 17 rotates, it moves linearly in the axial direction by fitting with the rotary cylinder 17.

Furthermore, a toothed sprocket 20 is attached to the end of the rotary cylinder 17 protruding from the fixed plate 10 at a distance from the fixed plate 10, and an electromagnetic brake 21 is provided between the fixed plate 10 and the sprocket 20. be.

The electromagnetic brake 21 has a structure generally called a hysteresis brake, and is composed of a field core with a built-in coil and an armature made up of a magnet with hysteresis characteristics. When the coil is energized, the field core is magnetized and a magnetic field is generated. When the armature is generated, the armature is also magnetized, and the field core and the armature are magnetically connected. When the armature tries to rotate, a braking force is generated, which acts as a force to prevent rotation.

Such an electromagnetic brake 21 is constructed by loosely fitting the field core 21a side into the rotary cylinder 17 and attaching it to the fixed platen 10.
The armature 21b side is fixed to the side surface of the sprocket 20.

Reference numeral 22 denotes a servo motor fixed horizontally inside the machine base 3, which is equipped with a rotation amount detector 23 and has a toothed sprocket 25 attached to a rotating shaft 24 protruding from the side wall of the machine base.
A toothed belt 26 is stretched across the sprocket 5 and the sprocket 20.

Next, position control and holding of the mold by the mold clamping device will be explained.

First, in the case of injection compression molding, the servo motor 2
Rotate 2 in the forward direction. The rotational force of the servo motor 22 is converted from the sprocket 25 of the rotating shaft 24 to the thrust of the screw shaft 15 screwed into the rotating tube 17 at a fixed position, and the movable platen 1
3 in the mold clamping direction.

The rotation amount detector 23 detects that the movable mold 14b has reached the preset mold closing position A shown in FIG. Cylinder 1
Restrain 7. As a result, the movable platen 13 is also restrained together with the movable mold 14b via the screw shaft 15, and is held in a state that can withstand injection pressure.

Next, molten resin 28 is injected from the injection tube 27 into the closed mold. After injection is completed, electromagnetic brake 2
Cut off the current to 1 and release the brake. Then, the servo motor 22 is rotated forward again to rotate the movable plate 13.
At the same time, the movable mold 14b is moved until the next set position B is detected by the rotation amount detector 23, the resin 28 in the mold is compressed, and a strong mold clamping process begins.
After cooling, the servo motor 22 is reversely rotated, and the movable platen 1
3 in the mold opening direction to release the molded product.

In the above embodiment, injection filling is performed while the movable mold 14b is held at the mold closing position A, but the movable mold 14b is moved forward until it reaches the mold closing position B or touches the fixed mold 14a, and then While injecting and filling the molten resin 28 into the closing mold, the movable mold 14b is moved backward together with the movable platen 13 due to its internal pressure, and the rotation amount detector 2 detects when the mold closing position A has been reached.
3 is detected, the injection filling is completed and the electromagnetic brake 21 is operated as necessary. After a predetermined period of time has elapsed, the brake is released in the same manner as above, and the servo motor 22 is rotated in the forward direction again. The mold 14b may be moved forward to enter the compression process.

In addition, in the case of injection foam molding, the movable mold 14b
is in contact with the fixed mold 14a, or the setting position B
The servo motor 22 is rotated in the forward direction to move the movable platen 13 together with the movable mold 14b until the amount of rotation is detected by the rotation amount detector 23.

Once it has moved to the specified position, apply electromagnetic brake 2.
1 is activated, the servo motor 22 is stopped, and the movable platen 13 is also stopped in the mold closed state.

Next, foamable resin 28 is injected into the mold. After the injection is completed, the current value applied to the electromagnetic brake 21 is changed to zero or a predetermined low current value. As a result, the movable platen 13 generates a retreating force due to the foaming pressure of the resin 28 in the mold, and moves together with the screw shaft 15 in the mold opening direction. Further, as the screw shaft 15 moves backward, a rotational force is generated in the bearing member 18.

The rotational force in the bearing member 18 and the braking force of the electromagnetic brake 21 (the current value and the braking force are almost proportional) can be balanced and the brake can be slipped, thereby maintaining a predetermined pressure inside the mold. , the mold volume increases and foams.

When the rotation amount detector 23 detects that the movable platen 13 has retreated to the predetermined mold closing position A, the current of the electromagnetic brake 21 is increased to maintain that position and cool the molded product.

In this case, the increase in mold volume does not depend on the foaming pressure;
The servo motor 22 may be rotated in reverse at high speed to forcibly retreat to the mold closing position A. After cooling, the servo motor 22 rotates in the opposite direction and enters a mold opening process, whereby the molded product is released from the mold. In addition, the above electromagnetic brake 2
1 may be omitted and the movable platen may be held or restrained by using the servo motor as a brake by the braking force of the servo motor 22.

As mentioned above, in this invention, since the rotating member in a fixed position and the screw shaft are screwed together through the ball, the rotational resistance of the screwed part is extremely small, and even with a small rotational force, the screw shaft can be secured. Move to. In addition, the electric motor is a servo motor, and the servo motor is equipped with a rotation amount detector that detects the amount of rotation of the servo motor and controls the amount of movement of the movable platen and the closing position of the mold. The closing position of the mold can be arbitrarily set only by controlling the rotational force, and the closing position of the mold can be controlled at the same time as the set position is detected, so the accuracy is higher than when doing it mechanically, and the position can be adjusted using a limit switch. It has the advantage of not requiring the complicated settings required for detection and control.

[Brief explanation of the drawing]

The drawings show one embodiment of a mold clamping device for an electric molding machine according to the present invention, and FIG. 1 is a partially longitudinal side view, and FIG. 2 is a sectional view showing the setting position of a mold. 1... Mold clamping device, 13... Movable platen, 14a...
Fixed mold, 14b...Movable mold, 15...Screw shaft for mold clamping, 15a...Thread groove, 17...Rotating cylinder,
18... Bearing member, 19... Ball, 20, 24
... Sprocket, 21 ... Electromagnetic brake, 22
... Servo motor, 23 ... Rotation amount detector, 25
...Toothed belt.

Claims (1)

[Scope of Claims] 1. A rotating member in a fixed position, a screw shaft for mold clamping that is screwed into the rotating member and whose tip is connected to a movable platen, and a member that transmits the rotational force of an electric motor to the rotating member. In the mold clamping device, the rotating member and the screw shaft are screwed together through balls, and the electric motor is a servo motor, and the servo motor detects the amount of rotation of the servo motor to detect the amount of movement of the movable platen. A mold clamping device for an electric molding machine, characterized in that it is provided with a rotation amount detector for controlling the closed position of the mold and the closed position of the mold.