JPH0136587Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to a mold clamping device for an injection molding machine.

(B) Prior Art There are two types of mold clamping devices for conventional injection molding machines: a direct pressure type mold clamping device and a toggle type mold clamping device.
A direct pressure mold clamping device uses a large-diameter hydraulic cylinder to directly press the movable platen, and a toggle-type mold clamping device uses a toggle mechanism to double the pushing force of a relatively small-diameter hydraulic cylinder. It is designed to use force to press the movable platen.

(c) Problems that the invention aims to solve However, the mold clamping devices of conventional injection molding machines as described above are all driven using hydraulic pressure, and a seal is used to seal the hydraulic pressure. , sealing members, etc. are used, and these parts wear out as they are used, so it is necessary to periodically replace the parts, and in some cases, oil leakage accidents may occur and operation may be stopped. However, there were some aspects where productivity was not sufficient. Furthermore, since it is necessary to arrange a relatively large hydraulic cylinder, the overall length of the mold clamping device becomes long, resulting in a problem that the device becomes larger. The present invention solves the above-mentioned problems, eliminates the need for periodic replacement of gaskets, eliminates the need to stop the equipment due to oil leakage accidents, etc., and provides a mold clamping device for injection molding machines with a more compact structure. The purpose is to obtain. Note that Japanese Patent Publication No. 47-46418 discloses a press device using an electric motor and a screw mechanism, but does not disclose control elements necessary as a mold clamping device for an injection molding machine.

(d) Means for solving the problems The present invention achieves the above object by using an electric motor to operate the mold clamping device. That is, the mold clamping device of the injection molding machine according to the present invention has the following features:
A fixed plate and an end housing fixed on the bed so as to face each other at a predetermined interval;
Four tie bars that are rotatably attached to the stationary platen and the end housing and have male threads of a ball screw mechanism on the outer periphery, and four female threads of a ball screw mechanism that engage with the male threads of the four tie bars. A movable platen to which a nut member is attached, an electric motor provided on the end housing or bed, a drive mechanism that transmits the rotational force of the electric motor to four tie bars and rotates them in a synchronized state, and the electric motor can be braked. A position detector that can detect a signal corresponding to the position of the movable platen, a torque detector that can detect a signal corresponding to the torque generated by the electric motor, and a signal from the torque detector when clamping the mold. The controller includes a controller that operates an electromagnetic brake when a predetermined value is reached, and a controller that operates an electromagnetic brake when a signal from a position detector reaches a predetermined value when the mold is opened.

(E) Effect With the above configuration, when the electric motor is rotated, the tie bar is rotationally driven via the drive mechanism, and the movable platen to which the nut member that engages with the male thread is attached moves in the axial direction of the tie bar. .
Therefore, mold clamping and mold opening can be performed by controlling the rotational direction of the electric motor and activating the electromagnetic brake based on signals from the position detector and the torque detector.

(f) Embodiments Hereinafter, embodiments of the present invention will be described based on FIGS. 1 and 2 of the accompanying drawings.

A fixed platen 12 and an end housing 14 are fixed onto the bed 10 by bolts 16 and 18, respectively. The fixed platen 12 and the end housing 14 are arranged in parallel so as to face each other with a predetermined spacing therebetween. Four tie bars 20 are rotatably supported on the fixed platen 12 and the end housing 14. As shown in FIG. 2, the tie bars 20 are arranged at each corner of the fixed platen 12 and the end housing 14 (i.e.
(located at each vertex position of the square). The tie bar 20 is rotatably supported by a bearing 22 with respect to the fixed platen 12, and the vertical force acting on the tie bar 20 in the left direction in FIG. 1 is supported by a thrust bearing 24. . The thrust bearing 24 is arranged between the stationary platen 12 and a nut 26 screwed into the thread at the end of the tie bar 20. Note that the nut 26 is prevented from loosening by a lock nut 28. The other end of the tie bar 20 is rotatably supported by a bearing 30 with respect to the end housing 14. Bearing 30 is held to end housing 14 by metal fittings 32. A male screw 34 of a ball screw mechanism is attached to the outer periphery of the tie bar 20.
is formed. Each male thread 34 has a nut member 36 having a female thread constituting a ball screw mechanism.
are interlocked. Four nut members 36 are fixed to a movable platen 38. The movable platen 38 has a hole 38a through which the tie bar 20 passes, and is movable in the axial direction of the tie bar 20 when the male screw 34 rotates. A movable mold 40 is attached to the movable platen 38, while a fixed mold 42 is attached to the fixed platen 12. End housing 1
An electric motor 44 is attached to the center of the motor 4. The electric motor 44 includes an electromagnetic brake 46, a torque sensor 48 (torque detector), and a pulse generator 50.
(position detector). The rotational force of the electric motor 44 is transmitted to the tie bar 20 by a drive mechanism 56 composed of a drive gear 52 and four driven gears 54. That is, the electric motor 44
A drive gear 52 is connected to the rotating shaft 44a by a key 58.
are attached, and driven gears 54 are attached to the tie bars 20 by keys 60, respectively. The driving gear 52 meshes with four driven gears 54 at the same time.

Next, the operation of this embodiment will be explained. 1st
In the figure, the movable mold 40 and the fixed mold 42 are in a clamped state in which they are in close contact with each other, and injection is performed in this state, and the mold is opened after cooling. That is, when the electric motor 44 is operated and the drive gear 52 is rotated in a predetermined direction,
Four driven gears 54 that mesh with this rotate in synchronization. Therefore, the movable platen 38 moves to the left in FIG. 1 due to the action of the nut member 36 that engages with the external thread 34 of the tie bar 20. Movement of the movable platen 38 is detected by a pulse generator 50, and when the movable platen 38 reaches a predetermined position, a controller (not shown) stops the electric motor 44 and activates the electromagnetic brake 46 to ensure stopping. This completes the mold opening and the molded product is taken out from the mold. Next, the movable platen 38 is moved to the right in FIG. 1 for the next molding. That is, the electric motor 44 is rotated in a direction opposite to the above-mentioned predetermined direction,
Rotating the tie bar 20 via the drive mechanism 56,
The movable platen 38 is moved by the action of the male screw 34 and the nut member 36. In this way, the movable mold 40 is brought into close contact with the fixed mold 42, and the electric motor 44 is further rotated until the torque value detected by the torque sensor 48 reaches a predetermined value, and when the torque value reaches the predetermined value, the electromagnetic brake is applied. 46 is activated. This maintains a predetermined torque value. The value of this torque is such that a predetermined mold clamping force acts between the fixed mold 42 and the movable mold 40. The next injection is carried out in the mold clamped state shown in FIG. Thereafter, the same cycle as in the above case is repeated.

The mold clamping device of this injection molding machine performs the mold clamping operation using the electric motor 44 as described above and does not use a hydraulic cylinder, so problems such as wear and tear of packings and seal members, oil leakage, etc. do not occur. . Further, since the stroke, moving speed, and mold clamping force of the movable platen 38 can be controlled by the electric motor 44, these can be easily controlled as desired using a general controller. In this embodiment, the electric motor 44 is provided with a pulse generator 50 as a position detector, but instead of this, the movement of the movable platen 38 is directly detected by a linear encoder provided on the bed 10. You can also do that. Further, instead of the torque sensor 48, a current detector of the electric motor 44 can be used as the torque detector. The electric motor 44 can also be placed on the bed 10.

(g) Effects of the invention As explained above, according to the invention, the mold clamping operation is performed by an electric motor, so there is no need for a hydraulic cylinder, and there is no need to periodically replace packings, sealing members, etc. This makes it possible to prevent oil leakage accidents and the like, and since no hydraulic cylinder is required, the entire mold clamping device can be downsized. Furthermore, since the mold clamping mechanism is simplified, sufficient space is secured on the back side of the movable platen, and the degree of freedom in installing the ejector is increased. In addition, since the mold clamping force is maintained in the mold clamping state by an electromagnetic brake, there is no need to supply a large current to the electric motor during mold clamping, which saves energy and is advantageous in terms of the durability of the electric motor. be.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing one embodiment of the present invention, and FIG. 2 is a sectional view taken along the - line in FIG. 1. 10...Bed, 12...Fixed plate, 14...End housing, 16, 18...Bolt, 20...
... Tie bar, 22 ... Bearing, 24 ... Thrust bearing, 26 ... Nut, 28 ... Lock nut, 30 ... Bearing, 32 ... Metal fitting,
34...Male thread, 36...Nut member, 38...
Movable plate, 40...Movable type, 42...Fixed type, 44
...Electric motor, 46...Electromagnetic brake, 48...Torque sensor, 50...Pulse generator, 52...
Drive gear, 54... Driven gear, 56... Drive mechanism.

Claims (1)

[Scope of utility model registration request] A fixed plate and an end housing fixed on the bed so as to face each other at predetermined intervals, and four pieces rotatably attached to the fixed plate and the end housing and having a male thread of a ball screw mechanism on the outer periphery. A tie bar, a movable platen having four nut members each having a female thread of a ball screw mechanism that engages with the male threads of the four tie bars, an electric motor provided on the end housing or bed, and the rotational force of the electric motor. A drive mechanism that transmits the signal to four tie bars and rotates them in synchronization, an electromagnetic brake that can brake the electric motor, a position detector that can detect a signal corresponding to the position of the movable platen, and a A torque detector that can detect a signal corresponding to torque is used, and when the mold is closed, the electromagnetic brake is activated when the signal from the torque detector reaches a predetermined value, and when the mold is opened, the signal from the position detector reaches a predetermined value. A mold clamping device for an injection molding machine, comprising: a controller that activates an electromagnetic brake when the brake is reached.