JPH11198206A - Ball screw circulation apparatus for motor-driven injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a ball screw from having a short lifetime. SOLUTION: Ball screw shafts 21, 35, 64 and 72, ball screw nuts 23, 41, 65 and 73 screwed in with the ball screw shafts, a driving means for rotating the ball screw shafts and a ball screw circulation means which drives the driving means at a specified timing and under a different driving condition from an ordinary working time and circulates balls in the ball screw nuts, are provided. In this case, a lubricant can be enough fed to ball screws 84-87. In addition, as balls stored in the ball screw nuts 23, 41, 65 and 73 are separated from the screw faces and are sufficiently circulated through a return tube, each ball is released from restriction and becomes under free condition and the direction can be changed. As there becomes no possibility of applying always a large load on the same position of each ball, it is possible to prevent the ball screw 84-87 from having a short lifetime.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ball screw circulation device for an electric injection molding machine.

[0002]

2. Description of the Related Art Conventionally, in an injection molding machine, a screw is advanced in a heating cylinder, and molten resin is injected at a high pressure to fill a cavity space of a mold apparatus. In the above, a molded article is obtained by cooling and solidifying the resin.

To this end, the mold apparatus includes a fixed platen to which a fixed mold is attached, a movable platen to which a movable mold is attached, and a toggle mechanism for moving the movable platen forward and backward. By actuating and moving the movable platen forward and backward, the mold device can be closed, closed and opened.

[0004] In the case of an electric injection molding machine, an electric motor is provided for moving a screw in and out of the heating cylinder and for operating the toggle mechanism. The rotary motion generated by the electric motor is converted into a linear motion by a ball screw formed by combining a ball screw shaft and a ball screw nut, and the screw, a crosshead connected to the toggle mechanism, and the like. It is transmitted to.

In this case, a lubricant such as grease is periodically supplied to the ball screw.

[0006]

However, in the conventional electric injection molding machine, the ball screw shaft is used not only at a relatively high load and a small stroke but also at the same position. Often. Therefore, since a large load is always applied to the same portion of each ball accommodated in the ball screw nut, even if lubrication is periodically supplied, the life of the ball screw is reduced in a short time.

The present invention solves the above-mentioned problems of the conventional electric injection molding machine and provides a ball screw circulating device for the electric injection molding machine which can prevent the ball screw from having a short life. The purpose is to provide.

[0008]

In order to achieve the object, a ball screw circulation device for an electric injection molding machine according to the present invention comprises a ball screw shaft, a ball screw nut screwed to the ball screw shaft, and a ball screw nut. There is provided a driving means for rotating the ball screw shaft, and a ball screw circulating means for driving the driving means at a predetermined timing under driving conditions different from those in a normal operation to circulate the balls in the ball screw nut.

In another ball screw circulating apparatus for an electric injection molding machine according to the present invention, the ball screw circulating means drives the driving means at a lower speed than in a normal operation. In still another ball screw circulating device for an electric injection molding machine according to the present invention, the ball screw circulating means drives the driving means with a lower torque than in a normal operation.

In still another ball screw circulating device for an electric injection molding machine according to the present invention, the ball screw circulating means drives the driving means with a longer stroke than in a normal operation. In still another ball screw circulating device for an electric injection molding machine according to the present invention, the ball screw circulating means circulates the ball at the timing of lubrication.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 2 is a schematic view of the electric injection molding machine according to the embodiment of the present invention, and FIG. 3 is a perspective view of the electric injection molding machine according to the embodiment of the present invention. In the figure, reference numeral 11 denotes an injection device, 12 denotes a mold clamping device arranged to face the injection device 11, 13 denotes a molding machine frame that supports the injection device 11 and the mold clamping device 12, and 14 denotes the molding machine frame. An injection device frame 3 supported by the injection device 11 and supporting the injection device 11.
Reference numeral 1 denotes a guide provided along the longitudinal direction of the injection device frame 14, and reference numeral 43 denotes a mold device including a fixed mold 44 and a movable mold 45.

A ball screw shaft 21 is rotatably supported by the injection device frame 14, and one end of the ball screw shaft 21 is connected to a plasticizing moving motor 22 as driving means. The ball screw shaft 21 and the ball screw nut 23 are screwed together to form a ball screw 84, and the ball screw nut 23 and the injection device 11 are connected via a spring 24 and a bracket 25. Therefore, when the plasticizing movement motor 22 is rotated in the forward and reverse directions, the rotational movement of the plasticizing movement motor 22 is converted into a linear movement by the ball screw 84, and the linear movement is transmitted to the bracket 25. You. The bracket 25 moves along the guide 31 with the arrow A
The injection device 11 is moved forward and backward.

A heating cylinder 15 is fixed to the bracket 25 forward (to the left in FIG. 2), and an injection nozzle 16 is provided at a front end (left end in FIG. 2) of the heating cylinder 15. . A hopper 17 is disposed on the heating cylinder 15, and a screw 26 is disposed inside the heating cylinder 15 so as to be able to advance and retreat and rotate freely, and a rear end (a right end in FIG. 2) of the screw 26 is a support member. 32 rotatably supported.

A screw rotation servomotor 33 is attached to the support member 32. The rotation generated by driving the screw rotation servomotor 33 causes the rotation of the screw 26 via a timing belt 34.
It is transmitted to. Further, in the injection device frame 14, a ball screw shaft 35 is rotatably supported in parallel with the screw 26, and the ball screw shaft 35 and an injection servomotor 36 as a driving means.
Are connected via a timing belt 37. The front end of the ball screw shaft 35 is screwed with a ball screw nut 41 fixed to the injection pressure plate 32b to form a ball screw 85. The injection pressure plate 32b is fixed to the support member 32 via a load cell 32a. Accordingly, the rotation generated by driving the injection servomotor 36 is applied to the ball screw shaft 3 via the timing belt 37.
5 and the ball screw shaft 35 is rotated.
As a result, the ball screw nut 41 is moved in the direction of arrow B.

Next, the operation of the injection device 11 having the above configuration will be described. First, in the weighing step, the screw rotation servomotor 33 is driven, and the timing belt 3 is driven.
4 by rotating the screw 26,
6 is moved backward (moves rightward in FIG. 2) to a predetermined position. At this time, the resin supplied from the hopper 17 is heated and melted in the heating cylinder 15, and is stored (accumulated) in front of the screw 26 as the screw 26 retreats.

Next, in the injection step, the injection nozzle 16 is pressed against the fixed mold 44, the injection servomotor 36 is driven, and the ball screw shaft 35 is rotated via the timing belt 37. At this time, the support member 32 is moved with the rotation of the ball screw shaft 35 to move the screw 26 forward (to the left in FIG. 2), so that the resin accumulated in front of the screw 26 is injected. Injected from the nozzle 16, the fixed mold 44 and the movable mold 45
Is filled in the cavity space 47 formed between the two.

Next, the mold clamping device 12 will be described. The mold clamping device 12 includes a fixed platen 51, a toggle support 52, and the fixed platen 51 and the toggle support 52.
And the fixed platen 5
1 and a movable platen 54 which is disposed so as to be able to advance and retreat (move in the horizontal direction in the figure) along the tie bar 53, and is disposed between the movable platen 54 and the toggle support 52. Provided toggle mechanism 56. The fixed platen 51 and the movable platen 5
4, the fixed mold 44 and the movable mold 45 are attached to face each other.

The toggle mechanism 56 moves the movable platen 54 with the tie bar 53 by moving the crosshead 58 between the toggle support 52 side and the movable platen 54 side by a mold clamping servomotor (not shown) as a driving means. The movable mold 45 is moved toward and away from the fixed mold 44 to perform mold closing, mold closing and mold opening.

To this end, the toggle mechanism 56 includes a toggle lever 61 swingably supported by the crosshead 58, a toggle lever 62 swingably supported by the toggle support 52, Platen 54
, And the link between the toggle levers 61 and 62 and between the toggle lever 62 and the toggle arm 63 are link-coupled to each other.

A ball screw shaft 64 is rotatably supported by the toggle support 52, and the ball screw shaft 64 and a ball screw nut 65 fixed to the crosshead 58 are screwed together. 86 are formed. Then, in order to rotate the ball screw shaft 64, the mold clamping servomotor is attached to a side surface of the toggle support 52.

Accordingly, when the mold clamping servomotor is driven, the rotational movement of the mold clamping servomotor is converted into a linear movement by the ball screw 86, and the linear movement is transmitted to the crosshead 58. Is moved in the direction of arrow C. That is, the crosshead 58
Is advanced (moved to the right in FIG. 2), the toggle mechanism 56 is extended, the movable platen 54 is advanced, the mold is closed and the mold is clamped, and the crosshead 58 is retracted.
(To the left in FIG. 2), the toggle mechanism 56
Is bent, the movable platen 54 is retracted, and the mold is opened.

On the back of the movable platen 54, an ejector device 71 is provided.
The ejector pin extends through the movable mold 45 and has a front end (right end in FIG. 2) facing the cavity space 47, and an ejector pin (not shown) disposed behind the ejector pin (left side in FIG. 2). Ejector rod not provided, a ball screw shaft 72 disposed behind the ejector rod and rotated by a servo motor for projection (not shown) as driving means, and the ball screw shaft 72
The ball screw 87 is formed by the ball screw shaft 72 and the ball screw nut 73.

Accordingly, when the servo motor for projecting is driven, the rotational motion of the servo motor for projecting is converted into linear motion by the ball screw 87, and the linear motion is transmitted to the ejector rod, and the ejector rod and the ejector pin are moved. Is moved in the direction of arrow D. Reference numeral 94 denotes a display unit. Incidentally, a lubricant is periodically supplied to the ball screws 84 to 87. However, each ball screw shaft 21, 35, 6
4, 72 are not only used with a relatively high load and a small stroke, but are often used in the same position.

In this case, the ball screw nuts 23, 41,
Since a large load is always applied to the same portion of each of the balls (not shown) accommodated in the balls 65 and 73, even if the lubricant is periodically lubricated, the ball screws 84 to 87 have a short life. I will. Therefore, each ball is periodically circulated so that a large load is not always applied to the same portion of each ball.

FIG. 1 is a block diagram of a ball screw circulating device of an electric injection molding machine according to an embodiment of the present invention, FIG. 4 is a diagram showing an inspection display screen of a display unit in the embodiment of the present invention, and FIG. FIG. 6 is a longitudinal sectional view of the ball screw according to the embodiment of the present invention, and FIG. 6 is a transverse sectional view of the ball screw according to the embodiment of the present invention. In the figure, reference numeral 22 denotes a plasticizing movement motor for rotating the ball screw shaft 21; 36, an injection servomotor for rotating the ball screw shaft 35 (FIG. 2);
Reference numeral 1 denotes a control unit, 82 denotes a mold clamping servomotor that rotates the ball screw shaft 64, 83 denotes a protrusion servomotor that rotates the ball screw shaft 72, 94 denotes a display unit, and 95 denotes the control unit. Ball screw circulation means.

By the way, the cycle of lubricating the ball screws 84 to 87, that is, the lubrication interval, is as follows.
It is determined based on the operation time or the number of operation shots of the electric injection molding machine. For this purpose, the operation time or the number of operation shots is counted by a counter (not shown) in the control unit 81, and when the count value reaches a set value, the control unit 81 displays an inspection display on the display unit 94 as shown in FIG. A screen is formed, an alarm is issued, and the electric injection molding machine is stopped to urge the worker to greasing.

Therefore, the ball screw circulating means 95
At a predetermined timing, for example, when the worker
4 to 87, lubricant is supplied, and at the timing when the screw circulation button b1 displayed on the inspection display screen is touched, the plasticizing movement motor 22, the injection servomotor 36,
Servo motor 82 for mold clamping and servo motor 83 for protrusion
Are driven under driving conditions different from those during normal operation. In the present embodiment, the plasticizing movement motor 22, the injection servomotor 36, the mold clamping servomotor 82, and the ejection servomotor 83 are operated at a low speed (for example, a maximum speed of 10).
[%] Speed, low torque, and long stroke. Therefore, the ball screw shafts 21, 3
5, 64, 72 are rotated at a low speed and are moved with a long stroke in the axial direction. Note that the ball screw shafts 21, 35, 64, 72 can be reciprocated one or more times according to their length.

Therefore, the lubricant can be sufficiently supplied to the ball screws 84 to 87. Also, the ball 91 accommodated in the ball screw nuts 23, 41, 65, 73
Are separated from the screw surface and sufficiently circulated through the return tube 92, so that each ball 91
The constraint by ~ 87 is released, and the direction becomes free and the direction can be changed. As a result, a large load is not always applied to the same portion of each ball 91, so that the life of the ball screws 84 to 87 can be prevented in a short time.

Even if the ball screw shafts 35, 64, 72 cannot be moved by the necessary stroke length due to space restrictions, at least only the ball screw shaft 21 has the required stroke length. Can be moved. In an electric injection molding machine in which lubricant is automatically supplied to each of the ball screws 84 to 87 by a pump (not shown), the ball screw circulating means 95 supplies lubricant at a predetermined timing, The plasticizing movement motor 22, the injection servomotor 36,
Servo motor 82 for mold clamping and servo motor 83 for protrusion
Are driven under driving conditions different from those during normal operation.

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 a ball screw circulating apparatus for an electric injection molding machine, a ball screw shaft and a ball screw nut screwed to the ball screw shaft are provided. A driving means for rotating the ball screw shaft; and a ball screw circulating means for driving the driving means at a predetermined timing under driving conditions different from those in a normal operation to circulate the ball in the ball screw nut.

In this case, the lubricant can be sufficiently supplied to the ball screw. Further, since the balls accommodated in the ball screw nut are separated from the screw surface and sufficiently circulated through the return tube, each ball is released from the restraint, and can be changed to a free state and changed direction. Therefore, since a large load is not always applied to the same portion of each ball, it is possible to prevent the life of the ball screw from being shortened in a short time.

[Brief description of the drawings]

FIG. 1 is a block diagram of a ball screw circulation device of an electric injection molding machine according to an embodiment of the present invention.

FIG. 2 is a schematic view of an electric injection molding machine according to an embodiment of the present invention.

FIG. 3 is a perspective view of the electric injection molding machine according to the embodiment of the present invention.

FIG. 4 is a diagram showing an inspection display screen of a display unit according to the embodiment of the present invention.

FIG. 5 is a longitudinal sectional view of the ball screw according to the embodiment of the present invention.

FIG. 6 is a cross-sectional view of the ball screw according to the embodiment of the present invention.

[Explanation of symbols]

 21, 35, 64, 72 Ball screw shaft 22 Plasticizing movement motor 23, 41, 65, 73 Ball screw nut 33 Screw rotation servo motor 36 Injection servo motor 82 Mold clamping servo motor 83 Projection servo motor 91 Ball 95 Ball screw circulation means

Claims (5)

[Claims] 1. A ball screw shaft, (b) a ball screw nut screwed with the ball screw shaft, (c) a driving means for rotating the ball screw shaft, and (d) a predetermined timing And a ball screw circulating means for driving the driving means under driving conditions different from those in normal operation to circulate the balls in the ball screw nut. 2. The ball screw circulating device for an electric injection molding machine according to claim 1, wherein said ball screw circulating means drives said driving means at a lower speed than during normal operation. 3. The ball screw circulating device for an electric injection molding machine according to claim 1, wherein the ball screw circulating means drives the driving means with a lower torque than in a normal operation. 4. The ball screw circulation device for an electric injection molding machine according to claim 1, wherein said ball screw circulation means drives said drive means with a longer stroke than in a normal operation. 5. The ball screw circulating device for an electric injection molding machine according to claim 1, wherein said ball screw circulating means circulates the ball at a timing when lubrication is performed.