JPH0124618B2 - - Google Patents

Description

[Detailed description of the invention] (Technical field) The present invention relates to a mold clamping device in an injection molding machine,
In particular, the present invention relates to a mold clamping device that employs a ball screw mechanism as a moving mechanism for a movable platen.

(Prior art) The mold clamping device of an injection molding machine has the function of moving a movable platen, clamping the mold between it and a fixed platen, and further clamping the mold so as to oppose the pressure of the injection resin. is required. For this reason, conventionally, a direct pressure mold clamping device in which the movable platen is directly moved by a hydraulic cylinder, a toggle type mold clamping device in which the movable platen is moved via a link mechanism, etc. have been used.

On the other hand, it has been considered to adopt a ball screw mechanism used in machine tools and the like as a moving mechanism for the movable platen in the mold clamping device as described above.

(Problems to be Solved by the Invention) However, in the mold clamping device of an injection molding machine, in addition to the function of clamping the mold against the injection resin pressure,
Since the mold is normally required to have the ability to open and close at high speed, it is far from desirable to employ a ball screw mechanism as a moving mechanism for the movable platen. In other words, when a ball screw mechanism is used as a moving mechanism for the movable platen in a mold clamping device, by increasing the lead angle of the ball screw mechanism, it is possible to increase the opening and closing speed of the mold. However, in this case, in order to obtain the necessary clamping force, it becomes necessary to use a large-sized rotary drive means with a large operating force to drive the ball screw mechanism, which poses a problem that becomes extremely disadvantageous economically. Conversely, if the lead angle of the ball screw mechanism is reduced in order to obtain the necessary clamping force with a small rotary drive means with low operating force, the moving speed of the movable platen will inevitably decrease. As a result, it becomes difficult to open and close the mold at high speed, leading to a decrease in productivity.Therefore, in the past, a ball screw mechanism was used as the moving mechanism for the movable platen. It could hardly be said that this was a desirable situation.

(Means for Solving the Problems) Against this background, the present invention provides a mold clamping device that employs a ball screw mechanism as a moving mechanism for a movable platen, and increases the size of the rotational drive means that drives the ball screw mechanism. This device was designed to provide a mold clamping device that can obtain the necessary clamping force without having to move the mold, and can open and close the mold at high speed. In the mold clamping device of an injection molding machine, which moves the platen, clamps the mold between it and the fixed platen, and further clamps the mold against the pressure of the injection resin, a predetermined ball screw structure is used. While attaching one end of the male screw member screwed to the nut member to the movable platen, a rotation driving means is connected to the nut member screwed to the male screw member, and the rotation driving means rotates the nut. The movable platen is moved by rotating the member to perform a mold clamping operation of the mold between the movable platen and the fixed platen, and the armature member is rotatable integrally with the nut member. and a field assembly member is provided so as to be magnetically attached to the armature member while facing the armature member, and further, when the field assembly member is magnetically attached to the armature member, A fluid pressure cylinder is connected to the field assembly member so as to apply a rotational action to the nut member in the direction of bringing the movable platen closer, and after the mold is clamped, the field assembly member is connected to the nut member. By magnetically attaching the armature member, the mold can be clamped based on the operating force of the fluid pressure cylinder.

(Operations and Effects) According to such a mold clamping device, by increasing the lead angle of the ball screw mechanism, the movable platen can be moved and the mold can be opened and closed at high speed. On the other hand, when the mold is clamped, the operating force of the fluid pressure cylinder is applied as a rotational force to the nut member, and the movable platen is rotated against the fixed platen by the rotational operation of the nut member based on the operating force of the fluid pressure cylinder. Since the mold is clamped by being pressed by You can gain power.

In other words, according to the mold clamping device according to the present invention, by setting the lead angle of the ball screw mechanism large, it is possible to obtain the necessary clamping force without increasing the size of the rotational drive means that drives the ball screw mechanism. At the same time, it becomes possible to open and close the mold at high speed.

Furthermore, in the present invention, since the movable platen is constantly pressed against the fixed platen based on the operating force of the fluid pressure cylinder, the resin material injected into the mold cavity is cooled. Another advantage is that even if the mold shrinks, it will not cause insufficient clamping force of the mold.

In other words, in a mold clamping device that uses a ball screw mechanism as a moving mechanism for a movable platen, when clamping a mold, the mold is prevented from opening due to the pressure of the resin material injected into the cavity. Therefore, it is also possible to simply prevent the rotation of the nut member (ball screw mechanism) by magnetically attaching the field assembly member to the armature member, thereby preventing the movable platen from moving relative to the fixed platen. However, in this case, if the clamping allowance of the mold changes as the resin material in the cavity shrinks due to cooling, the threading force between the nut member and the male thread member in the ball screw mechanism will loosen accordingly, causing the mold to tighten. This causes problems such as insufficient clamping force due to the corresponding decrease in clamping force. However, in the mold clamping device according to the present invention, when clamping the mold, the movable platen is constantly pressed against the fixed platen based on the operating force of the fluid pressure cylinder. Therefore, even if the resin material in the cavity shrinks due to cooling, the movable platen is moved closer to the fixed platen by an amount corresponding to the change in the clamping allowance of the mold due to the contraction of the resin material, and the fixed platen is moved closer to the fixed platen. The pressing force of the movable plate against the
Therefore, depending on the shrinkage of the resin material due to cooling,
There is no shortage of clamping force of the mold.

(Example) Hereinafter, in order to clarify the present invention more specifically, one example thereof will be described in detail based on the drawings.

First, in FIG. 1, 10 is a movable mold 12.
It is a movable platen to which a holder is attached, and its four corners are slidably supported by four tie bars 14. The tie bars 14 are arranged parallel to each other in the front-rear direction (horizontal direction in the figure), and are fixed at their front ends (right side end in Figure 1) to a fixed platen 18 to which the fixed mold 16 is fixed. At its rear end, it is fixed to a flange 22 of the housing 20.

The housing 20 has a cylindrical shape with a flange 22 on the outer periphery, and is fixed to a stationary member (not shown). A shaft 24 having a bottomed cylindrical shape and having an opening at the front end is disposed, the front side of which is rotatably supported by the inner circumferential surface of the housing 20 but not movable in the front-rear direction. Note that the rear end portion of the shaft 24 is rotatably supported by a stationary member 26.

A cylindrical ball screw nut (hereinafter simply referred to as a nut) 28 is installed in the opening of the shaft 24.
is fixed. A longitudinal cylindrical ball screw 30 fixed to the movable platen 10 at the front end is disposed to pass through this nut 28 in the front-rear direction, and the nut 28 is connected to the nut 28 via a steel ball (not shown).
It is screwed together. A ball screw structure is adopted between the nut 28 and the ball screw 30, and here, the cylindrical ball screw 30
constitutes the male screw member.

Further, a large gear 32 is fixedly installed on the outer peripheral surface of the rear end side of the shaft 24.
A small gear 38 fixed to an output shaft 36 of an electric servo motor (hereinafter simply referred to as motor) 34 is engaged with the motor. When the motor 34 is driven to rotate, the rotation is reduced by the gears 38 and 32 and transmitted to the shaft 24, so that the nut 28 is rotated. Depending on the direction of rotation of this nut 28, the ball screw 30,
In turn, the movable platen 10 is moved forward or backward to open and close the molds 12 and 16. Here, the lead angle between the nut 28 and the ball screw 30 is set to be sufficiently large. Therefore, the movable platen 10 is moved at a sufficiently high speed, and the molds 12 and 16 are opened and closed at a sufficiently high speed.
As is clear from the above description, in this embodiment, the electric servo motor 34 constitutes the rotational drive means, and the shaft 24 and the ball screw nut 28 constitute a nut member. In other words, the shaft 24, the ball screw nut 28, and the ball screw 30 constitute a ball screw mechanism as a mechanism for moving the movable platen 10.

On the other hand, on the outer peripheral surface of the shaft 24, a disc-shaped bearing cover 40 is rotatably mounted on the shaft 24 so as to close the opening on the rear end side of the housing 20 and to be rotatable relative to the housing 20. It is inserted so that it can slide in the direction. A ring-shaped field assembly member 42 is fixed to the outer periphery of the bearing cover 40. Further, a disc-shaped armature 44 is fixed to the outer peripheral surface of the shaft 24 in a state where it faces the field assembly member 42 with a slight distance therebetween. And field assembly member 42
is always separated from the armature 44, but when a coil (not shown) disposed within the field assembly member 42 is excited, it moves in the axial direction of the shaft 24 and magnetizes the armature 44. I'm starting to be able to dress up.

Further, the bearing cover 40 is formed with an arm portion 46 extending radially outward,
As shown in FIG. 2, an air cylinder 48 serving as a fluid pressure cylinder is connected to the distal end of the arm portion 46 at the distal end of a piston rod 50 thereof. The air cylinder 48 is disposed substantially perpendicular to the axes of the arm portion 46 and the shaft 24, and is connected to a stationary member 52 at the end on the cylinder head side.
When the piston 54 is retracted toward the cylinder head and the piston rod 50 is contracted, the bearing cover 40, that is, the field assembly member 42, is rotated in the direction of advancing the ball screw 30. Conversely, when the piston rod 50 is extended, the field assembly member 42 is rotated in a direction that causes the ball screw 30 to retreat.

The expansion and contraction operations (extending and retracting operations) of the piston rod 50 of the air cylinder 48 are here controlled by a pneumatic circuit 56 shown in FIG. That is, the pneumatic circuit 56 includes a 4-port 2-position electromagnetic switching valve 58, and normally directs compressed air from the pneumatic source 60 to the filter 6.
2. Air cylinder 4 via regulator 64, lubricator 66, switching valve 58 and check valve 68
Air is supplied to the head side chamber 70 on the cylinder head side of 8, while air is discharged from the rod side chamber 72 on the piston rod 50 side via the variable throttle valve 74, the switching valve 58 and the muffler 76, so that the piston rod 50 is extended. ing. And the switching valve 5
When the solenoid 78 of 8 is energized, the air pressure source 6
The compressed air supplied from 0 to the switching valve 58 is supplied to the rod side chamber 72 via the check valve 80, while the air in the head side chamber 70 is discharged via the variable throttle valve 82, the switching valve 58, and the muffler 76. The piston rod 50 is then retracted. In addition,
84 is a pressure gauge.

To mold a predetermined molded product using such a mold clamping device, first, the motor 34 is rotated in the normal direction to advance the movable platen 10 toward the fixed platen 18, and the movable mold 12 is pressed against the fixed mold 16. . In this case, as described above, since the lead angle between the nut 28 and the ball screw 30 is set to be large, the movable platen 10 can be moved at high speed.

Next, with the movable mold 12 pressed against the fixed mold 16, the field assembly member 42 is pressed against the fixed mold 16.
The coil inside is excited, and the field assembly member 42 is magnetically attached to the armature 44. After the field assembly member 42 is magnetically attached to the armature 44, the solenoid 78 of the switching valve 58 of the pneumatic circuit 56 is energized, the piston rod 50 of the air cylinder 48 is moved backward, and the movable platen 10 (ball screw 30) is moved. the field assembly member 42 in the direction of approaching the fixed platen 18;
In turn, the nut 28 is rotated to press the movable mold 12 onto the fixed mold 16. And after that,
A resin material is injected into the cavity formed between the molds 12 and 16, and a predetermined molding operation is performed. Note that this injection of the resin material is performed by an injection device (not shown) inserted into a tapered hole 86 formed in the stationary platen 18.

In this way, the movable platen 10 is pressed against the fixed platen 18 based on the operating force of the air cylinder 48, so that the ball screw 30 (nut 28)
Even if the pressing force of the movable platen 10 against the fixed platen 18 is not large enough due to the large lead angle of the motor 34 and the rotational force of the motor 34, a sufficiently large clamping force can be obtained, and the movable platen 10 is moved backward. Even if the injection resin pressure acts on the movable mold 12 in this direction, the molds 12 and 16 can be sufficiently firmly clamped against the injection resin pressure. In addition, the air cylinder 48
Since the movable platen 10 is always pressed against the fixed platen 18 based on the operating force of the
Even if the resin material injected into the cavity shrinks due to cooling, the mold 1 due to the shrinkage of the resin material
The movable platen 10 is moved closer to the fixed platen 18 side by an amount corresponding to the variation in the clamping allowance of 2 and 16, and the fixed platen 1
Therefore, the pressing force of the movable platen against the mold 1 is kept constant, and therefore, due to the contraction of the resin material, the mold 1
There is no possibility of insufficient clamping force as shown in 2.16.

Note that, as described above, since the clamping force of the molds 12 and 16 is obtained based on the operating force of the air cylinder 48, the motor 34 as a rotational drive means is
A small device with low operating force (output) is sufficient.

On the other hand, after the resin material is injected into the cavity, when a certain cooling and solidifying period has passed and a predetermined molding operation is completed, the solenoid 78 of the switching valve 58 in the pneumatic circuit 56 is demagnetized, and the air cylinder 48 As the piston rod 50 is extended, the coil in the field assembly member 42 is demagnetized, and the magnetic state between the armature 44 and the field assembly member 42 is canceled.
Rotation of the shaft 24 is allowed. At the same time, the motor 34 is reversed, and the ball screw 30,
That is, the movable platen 10 is moved backward and the mold opening operation is performed. In addition, also in this case, the movable platen 10
Of course, it is possible to move at high speed.

When the mold opening operation by reversing the motor 34 is completed, the molded product formed in the cavity is released from the movable mold 12 by the ejector pin 88 projected forward from the movable mold 12.
taken out. After that, a new molding cycle similar to that described above will be repeated again. The ejector pin 88 is projected by moving the ejector rod 90, which is disposed through the movable platen 10, the ball screw 30, the shaft 24, and the stationary member 26, in the axial direction.

As explained above, according to the mold clamping device of this embodiment, the electric servo motor 3 as the rotational drive means
4, it is possible to obtain the required mold clamping force while adopting a small type with low operating force (output), and the molds 12 and 16 can be opened and closed at high speed. Moreover, insufficient clamping force due to shrinkage of the resin material can be effectively avoided.

In addition, in this embodiment, the electric servo motor 34 is used as the rotational drive means, and the air cylinder 48 is used as the fluid pressure cylinder, so the control of the entire device is easy and the structure of the device itself can be made compact. There are some advantages.

Furthermore, in the mold clamping device of this embodiment, since the clamping force is obtained based on the operating force of the air cylinder 48, the air cylinder 48
The advantage is that the clamping force can be easily adjusted by adjusting the pressure of the air, and for the same reason, it is possible to easily display the clamping force using the pressure gauge 84. There are also some advantages.

Although one embodiment of the present invention has been described above, this is a literal illustration, and the present invention should not be interpreted as being limited to this specific example.

For example, in the embodiment described above, the air cylinder 48, which is easy to handle, is used as the fluid pressure cylinder, but it is also possible to use another fluid pressure cylinder such as a hydraulic cylinder instead of the air cylinder 48.

Further, in the embodiment described above, the clamping force was obtained based on both the operating force of the air cylinder 48 and the rotational force of the electric servo motor 34, but the operating force of the air cylinder 48, that is, the hydraulic cylinder Of course, it is also possible to obtain the clamping force based only on the

Further, in the embodiment described above, the electric servo motor 34 was employed as the rotation drive means, but it is also possible to employ other rotation drive means such as a hydraulic servo motor.

In addition, although not listed one by one, various modifications,
It goes without saying that the present invention can be implemented in a modified manner.

[Brief explanation of drawings]

FIG. 1 is a front cross-sectional view showing a mold clamping device of an injection molding machine according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view showing the same along with a pneumatic circuit for driving and controlling an air cylinder. 10: Movable plate, 12, 16: Mold, 18: Fixed plate, 20: Housing, 24: Shaft, 28:
Ball screw nut, 30: Ball screw (male thread member), 34: Electric servo motor (rotation drive means),
40: bearing cover, 42: field assembly member, 44: armature, 48: air cylinder (fluid pressure cylinder), 56: pneumatic circuit.

Claims (1)

[Scope of Claims] 1 Mold clamping in an injection molding machine in which a movable platen is moved to clamp a mold between it and a fixed platen, and the mold is further clamped to counter the injection resin pressure. In the apparatus, one end of a male screw member screwed to a nut member having a predetermined ball screw structure is attached to the movable platen, while a rotational drive means is connected to the nut member screwed to the male screw member, By rotating the nut member by the rotary drive means, the movable platen is moved to perform a mold clamping operation of the mold between the fixed platen and the nut member. An armature member is provided to be integrally rotatable, and a field assembly member is provided to be magnetically attached to the armature member while facing the armature member, and further, the field assembly member is magnetically attached to the armature member. A fluid pressure cylinder is connected to the field assembly member so as to apply a rotational action to the nut member in the direction of bringing the movable plate closer to the fixed plate, and after the mold is clamped, In, by magnetically attaching the field assembly member to the armature member,
A mold clamping device characterized in that the mold can be clamped based on the operating force of the fluid pressure cylinder. 2. The mold clamping device according to claim 1, wherein the rotational drive means is an electric servo motor, and the fluid pressure cylinder is an air cylinder.