JPH03108514A - Mold clamping device in motor-driven type molding machine - Google Patents

Abstract

PURPOSE:To stepwise control the closing position of a mold by performing engagement of a rotary member and a screw shaft via a ball and constituting a motor of a servomotor and providing a detector for amount of rotation to the servomotor and detecting the amount of rotation of this servomotor and controlling both the moving range of a movable platen and the closing position of the mold. CONSTITUTION:A rotary cylinder 17 becoming a positional rotary member is freely rotated by utilizing a ball bearing 16 and penetrated through a fixed plate 10. A screw shaft 15 for mold clamping is inserted into the nutlike bearing member 18 of the rotary cylinder 17. When this rotary cylinder 17 is rotated by engagement of many balls 19, 19 in a spiral groove provided to inside of the bearing member 18 and screw grooves 15, the screw shaft 15 for mold clamping is rectilinearly moved to the axial direction. Further a detector 23 for amount of rotation is equipped to a servomotor 22 horizontally fixed to the inside of a mechanical base 3. This detector 23 detects the amount of rotation of the servomotor 22 and controls the moving range of a movable platen 13 and the closing positions of the molds 14a, 14b. Thereby detection of the setting position and control of the closing positions of the molds are simultaneously performed.

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, and the rotational speed is switched using a reduction gear. 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 responsiveness.As for mold clamping force, it is not possible to continue energizing in an overloaded state, so there is no other option. Since special means are required and the position of the movable platen is controlled by limit switches, the setup is complicated as the position needs to be adjusted 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 something.

This invention uses a servo motor as an electric motor, which can obtain a very large torque when rotating at low speed, has good responsiveness due to a large torque inertia ratio, and has a wide variable speed range, and uses the electric motor as a drive source by improving the screw shaft. This is an attempt to solve the problem of the case.

In addition, this invention can control the amount of movement of the movable platen 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 limit switches, etc., and molding the mold in stages. An object of the present invention is to provide a mold clamping device that can perform injection compression molding, injection foam molding, etc. that require control of the closed position of the mold.

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 10.11 provided facing each other on the machine base 3, a required number of tie bars 12.12 installed across the fixed plates 10.11, and a plurality of tie bars 12.12 installed on the tie bars 12.12. It has a movable platen 13 which is movably attached. 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 mold clamping screw shaft 15 marked with 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 inside the
By fitting into the thread groove 15a, when the rotary cylinder 17 rotates, it moves linearly in the axial direction.

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

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

Such an electromagnetic brake 21 has the above-mentioned filled core 2i.
The a side is loosely fitted into the rotary tube 17 and fixed to the stationary platen 10, and the armature 2ib side is fixed to the side surface of the sprocket 20 for installation.

22 is a servo motor fixed horizontally inside the machine base 3,
A toothed sprocket 25 is attached to a rotating shaft 24 which is equipped with a rotational amount detector 23 and protrudes from the side wall of the machine, and a toothed belt 26 spans between the sprocket 25 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 22 is rotated 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, thereby moving the movable platen 1 in the mold clamping direction. Moving.

The rotation amount detector 23 detects that the movable mold 14b has reached the preset mold closing position A shown in FIG. to restrain. 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 the injection specific pressure.

Next, molten resin 28 is injected from the injection tube 27 into the closed mold. After the injection is completed, the current to the electromagnetic brake 21 is cut off to release the brake.

Then, the servo motor 22 is rotated forward again to move the movable mold 14b together with the movable platen 13 until the next setting position B is detected by the rotation amount detector 23, and the resin 28 in the mold is moved.
is compressed and enters the strong mold clamping process. After cooling, the servo motor 22 is reversely rotated to move the movable platen 13 in the mold opening direction to release the molded product.

In the above embodiment, the movable mold 14b is held at the mold closing position A and injection filling is performed, but the movable mold 14b is moved forward until it touches the mold closing position B1 or the fixed mold 14a,
Thereafter, while the molten resin 28 was injected and filled into the closing mold, the movable mold 14b was moved backward together with the movable platen 13 by the internal pressure, and the rotation amount detector 23 detected that the mold closing position A was reached. If so, the injection filling is completed, and the electromagnetic brake 21 is operated as necessary, and 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 forward again to move the movable mold 14b forward. Alternatively, the compression process may be started.

In the case of injection foam molding, the servo motor 22 is rotated forward until the movable mold 14b contacts the fixed mold 14a or the set position B is detected by the rotation amount detector 23. At the same time, the movable platen 13 is moved.

Once the mold has moved to a predetermined position, the electromagnetic brake 21 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 approximately proportional) are:
It is possible to slip the brakes while maintaining balance,
As a result, while maintaining a predetermined pressure within the mold, the mold volume increases and foaming occurs.

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 mold volume may be increased without depending on the foaming pressure, and the servo motor 22 may be forced to retreat to the mold closing position A by rotating the servo motor 22 in reverse at high speed. 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. Note that the electromagnetic brake 21 is omitted and the servo motor 22 is used instead.
The movable platen may be held or restrained by using a servo motor as a brake with the braking force of the movable platen.

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 closed position of the mold can be arbitrarily set by controlling only the rotational force, and the closed position of the mold can be controlled at the same time as the set position is detected, so the accuracy is higher than when done mechanically, and the position can be adjusted using a limit switch. Its features include the fact that it does not require the complicated settings that would be required for detection and control.

[Brief explanation of drawings]

The drawings show one embodiment of the 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 the mold. 1... Mold clamping device 13... Movable platen 4a...
・Fixed mold 5...Mold clamping screw shaft 7...Rotating tube 9...Ball 0.24...Sprocket...Electromagnetic brake 3...Rotation amount detector 14b...Movable metal Type 15a...Thread groove 18...Bearing member 22...Servo motor 25...Toothed belt

Claims (1)

[Scope of Claims] A rotary member in a fixed position, a screw shaft for mold clamping that is screwed into the rotary member and whose tip is connected to a movable platen, and a member that transmits the rotational force of an electric motor to the rotary member. In this 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 and calculates the amount of movement of the movable platen. A mold clamping device for an electric molding machine, characterized in that it is equipped with a rotation amount detector for controlling the closed position of a mold.