JPH10225965A - Ejector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a periphery of an injection molder from being stained while its durability can be improved by a method wherein a position according to rotation generated with a rotor is directly detected. SOLUTION: Since rotary motion generated with a servo motor 102 is converted to a linear motion to make an ejector pin feed device 18 function directly, a timing belt becomes unnecessary to be used. In order to control the servo motor 102, an encoder 131 as a rotary number sensor is fixed to a rear end of a hollow shaft 110, and the number of rotations of the rotor 107 can be directly detected with the encoder 131. Therefore, a position of a crosshead 25 can be accurately detected. Further, in order to detect a retreat limit position of the crosshead 25, a proximity switch 135 is arranged to a movable platen 11. The proximity switch 135 can be reset per each one forming. Further, a limit switch can be used in place of the proximity switch 135.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ejector device.

[0002]

2. Description of the Related Art Conventionally, in an injection molding machine, a resin heated and melted in a heating cylinder is filled at a high pressure into a cavity space of a mold apparatus, and cooled and solidified in the cavity space. Thus, a molded article is obtained. The mold device is composed of a fixed mold and a movable mold. The movable mold is moved forward and backward by a toggle mechanism, and is brought into contact with and separated from the fixed mold to perform mold closing, mold clamping, and mold opening. You can do it. Then, in opening the mold, the mold clamping device is retracted with the molded product remaining in the movable mold, and subsequently, the ejector pin is advanced by the ejector device, the molded product is ejected, and the mold is released. It has become.

[0003] To this end, the ejector pins are disposed with the front end facing the cavity space, and the rear end is fixed to an ejector plate. An ejector pin feeder is connected to a rear end of the ejector plate via an ejector rod. Then, when the ejector pin feeder is operated and the ejector plate is advanced through the ejector rod, the ejector pin fixed to the ejector plate is advanced.

By the way, in an electric injection molding machine,
Usually, the ejector pin feeder is operated by an electric motor. FIG. 2 is a front view of a conventional single-shaft ejector device, and FIG. 3 is a side view of a conventional single-shaft ejector device. In the figure, reference numeral 11 denotes a movable platen, and a movable mold (not shown) is attached to a front end (right end in FIG. 2) of the movable platen 11. The movable platen 11 is advanced and retracted by a toggle mechanism 14 along a tie bar 12 provided between a fixed platen (not shown) and a toggle support.

The rear end of the movable platen 11 (FIG. 2)
(The left end of the figure), an ejector pin feeder 16 is provided. In the ejector pin feeder 16,
A front end of a guide bar 18 is fixed to the movable platen 11, and a support 19 is fixed to a rear end of the guide bar 18. The support 19 is connected to the nut 2 via a bearing 20.
2 is rotatably supported.

[0006] The nut 22 is screwed with the ball screw shaft 24 on the inner periphery thereof.
The crosshead 25 is fixed to the front end of the crosshead 4, and the ejector rod 27 is fixed to the front end of the crosshead 25. Therefore, by rotating the nut 22, the ball screw shaft 24 can be advanced and retracted in the direction of arrow A, and the ejector rod 27 can be advanced and retracted in the same direction.

The ejector pin feeder 16 is operated by a servomotor 28, and a belt transmission mechanism 31 is disposed between the servomotor 28 and the nut 22. The belt transmission mechanism 31 includes a pulley 32 disposed on an output shaft of the servomotor 28, a pulley 33 disposed on a rear end of the nut 22, and a timing belt stretched between the pulleys 32, 33. 34.

Therefore, when the servo motor 28 is driven, the rotation of the servo motor 28 is transmitted to the nut 22 via the belt transmission mechanism 31. And the nut 22
The rotational motion is converted into a linear motion by the ball screw shaft 24 and the ejector pin (not shown) is moved forward and backward.
Next, a two-axis ejector device will be described.

FIG. 4 is a front view of a conventional two-axis type ejector device, and FIG. 5 is a side view of a conventional two-axis type ejector device. In the figure, reference numeral 11 denotes a movable platen, and a movable mold (not shown) is attached to a front end (right end in FIG. 4) of the movable platen 11. The movable platen 11
By the toggle mechanism 14, it is advanced and retracted along the tie bar 12 provided between the fixed platen (not shown) and the toggle support.

The rear end of the movable platen 11 (FIG. 4)
(The left end of the figure), an ejector pin feeder 16 is provided. In the ejector pin feeder 16,
The front end of the guide bar 18 is fixed to the movable platen 11, and the crosshead 41 is fixed to the rear end of the guide bar 18. Then, a nut 42 is fixed to the crosshead 41.

Further, the nut 42 is screwed on an inner periphery with a ball screw shaft 43, and the ball screw shaft 43 is
The front end is rotatably supported by the movable platen 11 by a bearing (not shown). The ejector rod 27 is fixed to the front end of the cross head 41. Therefore, by rotating the ball screw shaft 43, the crosshead 41 can be advanced and retracted, and the ejector rod 27 can be similarly advanced and retracted.

The ejector pin feeder 16 is operated by a servomotor 28, and a belt transmission mechanism 46 is disposed between the servomotor 28 and the ball screw shaft 43. . The belt transmission mechanism 46 is extended between the pulleys 32 disposed on the output shaft of the servomotor 28, a plurality of pulleys 33 disposed on the front end of the ball screw shaft 43, and the respective pulleys 32, 33. Timing belt 34.

Accordingly, when the servo motor 28 is driven, the rotation of the servo motor 28 is transmitted to the ball screw shaft 43 via the belt transmission mechanism 46. Then, the rotational motion is converted into a linear motion by the ball screw shaft 43 and the nut 42, and an ejector pin (not shown) is moved forward and backward.

[0014]

However, in the above-mentioned conventional ejector device, not only does the timing belt 34 need to be strongly stretched in order to completely protrude the molded product from the movable mold and release the molded product. Since the ejector pin needs to be repeatedly advanced and retracted, it is placed under severe conditions, and the durability of the ejector device is reduced.

That is, since the timing belt 34 needs to be strongly stretched, the ball screw shafts 24 (FIG. 2), 43
Of the ball screw shafts 24 and 43, the efficiency of the ball screw shafts 24 and 43 is reduced, and not only the load on the servomotor 28 is increased but also the life of the ball screw shafts 24 and 43 is shortened. In addition, since the timing belt 34 is stretched and the control accuracy of the ejector device is reduced, or the timing belt 34 is broken or worn, the timing belt 34 needs to be replaced in a relatively short time.

Furthermore, abrasion of the timing belt 34 generates abrasion powder, which contaminates the periphery of the injection molding machine. Therefore, it is conceivable to improve the durability by increasing the hardness of the timing belt 34. However, when the ejector device is operated at high speed, noise is generated. Although it is conceivable to use a chain, a rack and pinion, or the like instead of the timing belt 34, the control accuracy is low, and play occurs. Therefore, the area around the injection molding machine is soiled.

An object of the present invention is to provide an ejector device which can solve the problems of the above-mentioned conventional ejector device, can improve durability, and does not stain the periphery of the injection molding machine.

[0018]

For this purpose, in the ejector device of the present invention, there is provided a movable platen which is arranged to be movable back and forth along a tie bar in opposition to a fixed platen.
A stator attached to a rear end of the movable platen, a rotor disposed inside the stator, a hollow shaft fixed to the rotor, a ball nut fixed to the hollow shaft, and the ball nut The ball screw shaft includes a ball screw shaft that is screwed and moved forward and backward with the rotation of the ball nut, and a crosshead fixed to the ball screw shaft.

Then, the position due to the rotation generated by the rotor is directly detected.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view of a main part of an ejector device according to an embodiment of the present invention.
7 is a schematic view of an ejector device according to an embodiment of the present invention, FIG. 7 is a sectional view taken along line VV of FIG. 6, and FIG. 8 is a sectional view taken along line WW of FIG.

In the figure, reference numeral 11 denotes a movable platen,
Front end of the movable platen 11 (right end in FIGS. 1 and 6)
A movable mold (not shown) is attached to the dies. The movable platen 11 is advanced and retracted by a toggle mechanism 14 along a tie bar 12 provided between a fixed platen (not shown) and the toggle support 101. An ejector pin feeder 16 is provided at the rear end (left end in FIGS. 1 and 6) of the movable platen 11. In the ejector pin feeder 16, a front end of a guide bar 18 is fixed to a surface of the movable platen 11 facing the toggle support 101, and a servo motor 102 is fixed to a rear end of the guide bar 18 by bolts 103.

The servo motor 102 includes a stator 105 fixed to a motor frame 104,
5 and a rotor 107 arranged close to the inside of the stator 105. By supplying a current to the coil 106, the rotor 107 can be rotated. Further, the motor frame 104 has a front flange 1.
04a, rear flange 104b, stator frame 104
c, and the front flange 104a and the rear flange 104b
And a tie rod 138 for coupling and tightening.
The servomotor 102 may be of various types, such as an induction type or a synchronous type.

A hollow shaft 110 is fixed further inside the rotor 107, and both ends of the hollow shaft 110 are rotatably supported by the motor frame 104 by bearings 111 and 112. The hollow shaft 110 has a medium diameter portion 115 as a first portion disposed inside the rotor 107, and a large diameter portion as a second portion formed on the movable platen 11 side from the medium diameter portion 115. 116, and a small diameter portion 117 as a third portion formed on the toggle support 101 side with respect to the middle diameter portion 115, and a ball nut 120 is fixed inside the large diameter portion 116.

A ball screw shaft 121 is screwed with the ball nut 120, and the ball screw shaft 121
The crosshead 25 is fixed to the front end by a nut 123, and the ejector rod 27 is fixed to the crosshead 25. Then, the cross head 25 is prevented from rotating by the guide bar 18. Therefore, by driving the servo motor 102 and rotating the rotor 107, the ball nut 120 is rotated in the direction of arrow F, and the rotational motion is converted into linear motion by the ball nut 120 and the ball screw shaft 121, and the Head 2
5 can be advanced and retracted in the direction of arrow A along the guide bar 18. As a result, the ejector rod 27 and the ejector pin (not shown) can be moved in the same direction.

In this case, the crosshead 25 and the ejector rod 27 must be advanced and retracted by a stroke S required to eject a molded product (not shown) by the ejector pin. A concave portion 11a having a desired depth is formed.
In addition, since the ball screw shaft 121 is advanced and retracted by the stroke S by rotating the ball nut 120, a hollow portion 110a having a length corresponding to the stroke S is formed inside the middle diameter portion 115. .

As described above, in the present embodiment, the rotational motion generated by the servomotor 102 is converted into a linear motion, and the ejector pin feeder 16 is directly operated. There is no need to use it. Therefore, the durability of the ejector device can be improved, and the periphery of the injection molding machine is not stained.

Then, the ball screw shaft 121 is moved forward and backward in the hollow shaft 110 so that the servo motor 102
And the ball screw shaft 121 are integrated, the servo motor 102 is made flat, and the crosshead 25 is formed in the recess 11 a of the movable platen 11.
, The axial dimension of the ejector pin feeder 16 can be reduced. Further, the rotor 107 is provided outside the middle diameter portion 115 of the hollow shaft 110.
However, since the ball nut 120 is disposed inside the large diameter portion 116, the rotor 107 and the ball nut 120 overlap in the radial direction. Therefore, the radial dimension of the ejector pin feeder 16 can be reduced.

As a result, since the ejector pin feeder 16 can be disposed inside the toggle mechanism 14, the size of the mold clamping device can be reduced. In order to control the servomotor 102, an encoder 131 as a rotation speed sensor is fixed to a rear end of the hollow shaft 110,
The rotation speed of the rotor 107 can be directly detected by the encoder 131. Therefore, the position of the crosshead 25 can be accurately detected. In addition, a proximity switch 135 is provided on the movable platen 11 to detect the retreat limit position of the crosshead 25. The proximity switch 135 can be reset each time molding is performed. In addition,
A limit switch can be used in place of the proximity switch 135.

Since the hollow shaft 110 and the ball nut 120 are rotated by driving the servo motor 102, if the inertia is large, a delay may occur when controlling the rotation speed. Therefore, the hollow shaft 110 and the ball nut 120 are made thinner to reduce the inertia. Further, in order to reduce the frictional resistance between the ball nut 120 and the ball screw shaft 121, the two are lubricated with grease.
A greasing hole 132 is formed in the small-diameter portion 117, and a communication passage 133 that connects the greasing hole 132 and the hollow portion 110a is formed in the small-diameter portion 117 so that grease can be supplied. It has become.

It should be noted that the present invention is not limited to the above-described embodiment, but can be variously modified based on the gist of the present invention, and they are not excluded from the scope of the present invention.

[0031]

As described above in detail, according to the present invention, in the ejector device, the movable platen is provided so as to be able to move forward and backward along the tie bar in opposition to the fixed platen, and the rear of the movable platen. A stator attached to the end, a rotor disposed inside the stator, a hollow shaft fixed to the rotor, a ball nut fixed to the hollow shaft, and screwed with the ball nut, The ball screw shaft includes a ball screw shaft that is moved forward and backward with the rotation of the ball nut, and a crosshead fixed to the ball screw shaft.

Then, the position due to the rotation generated by the rotor is directly detected. In this case, since the ejector pins are moved forward and backward by converting the rotational motion generated by the rotor into linear motion, it is not necessary to use a timing belt. Therefore, the durability of the ejector device can be improved, and the periphery of the injection molding machine is not stained.

In addition, since the ball screw shaft is advanced and retracted in the hollow shaft, the axial dimension of the ejector pin feeder including the servomotor, the ball screw shaft and the like can be reduced. Therefore, the size of the mold clamping device can be reduced. Further, since the position due to the rotation generated by the rotor can be directly detected, the position of the crosshead can be accurately detected.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of an ejector device according to an embodiment of the present invention.

FIG. 2 is a front view of a conventional one-axis type ejector device.

FIG. 3 is a side view of a conventional one-axis type ejector device.

FIG. 4 is a front view of a conventional two-axis type ejector device.

FIG. 5 is a side view of a conventional two-axis type ejector device.

FIG. 6 is a schematic diagram of an ejector device according to an embodiment of the present invention.

FIG. 7 is a sectional view taken along line VV of FIG. 6;

FIG. 8 is a sectional view taken along line WW of FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Movable platen 12 Tie bar 25 Crosshead 105 Stator 107 Rotor 110 Hollow shaft 120 Ball nut 121 Ball screw shaft 131 Encoder

Claims (1)

[Claims] 1. (a) a movable platen that is disposed opposite to a fixed platen so as to be able to advance and retreat along a tie bar;
(B) a stator attached to the rear end of the movable platen; and (c) a rotor disposed inside the stator.
(D) a hollow shaft fixed to the rotor, (e) a ball nut fixed to the hollow shaft, and (f) a ball screwed to the ball nut and moved forward and backward with the rotation of the ball nut. An ejector device comprising: a screw shaft; and (g) a crosshead fixed to the ball screw shaft, and (h) a position detected by the rotation generated by the rotor is directly detected.