JP2000263609A - Forward and backward drive of molding machine - Google Patents

Abstract

(57) [Problem] To provide a forward / backward drive device using a rotation → linear motion conversion mechanism configured to advance a ball screw shaft back and forth by rotation of a ball nut body, thereby reducing the moment of inertia, and Improve responsiveness and machine performance. SOLUTION: A ball nut body which rotates by receiving a rotating force of a motor, a ball screw shaft which is screwed to the ball nut body and moves in the axial direction by rotation of the ball nut body,
And a driven body that linearly moves with the ball screw under the axial driving force of the ball screw shaft. The bearing is formed between the cylindrical case member of the ball nut body, the mounting ring member fixed to the support frame, and the outer peripheral surface of the cylindrical case member and the inner peripheral surface of the mounting ring member. It is constituted by interposed rolling elements.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a forward and backward drive of a molding machine, such as an injection molding machine or a die casting machine, provided with a mechanism for converting rotation from a linear to a linear motion by a ball nut body and a ball screw shaft. The present invention relates to a forward / backward drive device in which the outer periphery of a ball screw shaft is supported via a bearing, and the ball screw shaft is moved forward / backward by rotation of a ball nut body to move a driven body back and forth.

[0002]

2. Description of the Related Art It is known that a molding machine such as an injection molding machine uses a motor such as an electric servomotor as a drive source of a forward / reverse mechanism. Rotation by a ball nut body and a ball screw shaft → linear motion is converted by a linear motion conversion mechanism, and the driven member (for example, a member for reciprocating an eject pin in an eject system, a movable die in a mold opening / closing system) A member for reciprocating the plate,
In the case of the injection system, a member for reciprocating the screw)
Forward and backward.

In the case of using the rotation-to-linear motion conversion mechanism as described above, a structure in which a ball screw shaft is supported and the ball nut body is moved forward and backward by rotation of the ball screw shaft, or the ball nut body is supported in a rotating manner. Then, any one of the configurations in which the ball screw shaft is moved forward and backward by rotation of the ball nut body is adopted. When the latter rotation-to-linear motion conversion mechanism is employed, the ball nut body, which transmits the rotation of the motor via an appropriate rotation transmission mechanism, is rotated on a suitable support member via a bearing (such as a boring bearing). It must be held freely.

FIG. 4 is a diagram showing a conventional configuration of the latter rotation-to-linear motion conversion mechanism, and FIG. 5 is an enlarged view of a main part of FIG.

In FIGS. 4 and 5, reference numeral 51 denotes a movable die plate to which a movable die (not shown) is attached; 52, a toggle link mechanism for moving the movable die plate 51 back and forth with respect to a fixed die plate (not shown); Reference numeral 53 denotes a plurality of bearings fitted in the holding holes of the movable die plate 51, reference numeral 54 denotes a ball nut body rotatably held by the plurality of bearings 53, and reference numeral 55 denotes the rotation of a motor (not shown) to the ball nut body 54. Pulley 56 for the ball nut body 54
Is a ball screw shaft screwed into the shaft.

The outer ring of each bearing 53 is fixed to a movable die plate 51 (movable die plate 51).
The ball nut body 54 is firmly fitted and integrated with the inner ring of each bearing 53 which is rotatable via a ball on the outer ring. The inner ring 53 and the ball nut body 54 rotate integrally. The pulley 5
5, the rotation of a motor (not shown) serving as an ejection drive source mounted on the movable die plate 51 is transmitted via a timing belt (not shown). It is designed to rotate together. In addition, at the end 56a of the ball screw shaft 56,
An eject pin (not shown) is connected via an appropriate connecting member, and the eject pin is configured to be able to advance and retreat in a movable mold (not shown).

In the above-described configuration, at the timing when the resin injected and filled into the mold is cooled and solidified, the movable die plate is driven via the toggle link mechanism 52 by the driving force of a motor (not shown) as a mold opening / closing drive source. The mold is opened by being driven backward (driven in the direction away from the fixed-side die plate), and after completion of the mold opening or during the mold opening, a motor (not shown) serving as an eject drive source is moved in a predetermined direction. Is driven to rotate. The rotation of the ejecting motor is transmitted to the pulley 55, and the ball nut body 54 is driven to rotate in a predetermined direction together with the pulley 55. The rotation of the ball nut body 54 causes the ball screw shaft 5 to rotate.
6 is driven forward, whereby an eject pin (not shown) is driven forward, and the molded product is ejected from the movable mold.

[0008]

The conventional rotation described above →
In the linear motion conversion mechanism, the ball nut body 5
The outer ring of the bearing 53 is fitted with the inner ring of the bearing 53, and the outer ring of the bearing 53 is
The ball nut body 5
Numeral 4 is configured to be rotatably supported by a ball (roller) located between the inner ring and the outer ring of the bearing 53 so as to be able to rotate smoothly.

By the way, in the rotation-to-linear motion conversion mechanism using the ball nut body and the ball screw shaft, the moment of inertia M of the rotating body when the pulley 55 is excluded is considered.
Is expressed as M = GD ² by the radius D to the inner ring of the bearing 53 that rotates integrally with the ball nut body, and the weight G obtained by adding the weight of the ball nut body 54 and the weight of the inner ring of the bearing 53. Since the ordinary bearing 53 having the inner ring, the outer ring, and the rolling element is used, there is a limit in reducing the radius D of the rotating body, and therefore, the moment of inertia M of the rotating body is equal to GD ^2. There was naturally a limit to reducing the size. However, good high-speed response is in the machine (molding machine) obtained, by reducing the moment of inertia M = GD ^2, has been demanded to improve the transient response.

In the conventional configuration shown in FIGS. 4 and 5, the number of bearings 53 is large, and a support frame (movable die plate 5) for fitting the outer ring of the bearing 53 is used.
There is also a problem that the processing of the holding hole of 1) and the mounting of the bearing 53 are troublesome, and the assemblability of the ball nut body is ultimately poor.

[0011] The present invention has been made in view of the above points,
The purpose is to support the ball nut body,
In the forward / backward drive of a molding machine using a rotation → linear motion conversion mechanism configured to advance the ball screw shaft back and forth by the rotation of the ball nut body, the moment of inertia M = GD ² is reduced, so that the transient response (Rise / fall characteristics) to improve machine performance. Another object of the present invention is to improve the assemblability of a ball nut body.

[0012]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides a ball nut body which is rotated by the rotational force of a motor, and which is screwed into the ball nut body to rotate in the axial direction. A ball screw shaft that moves to
And a driven body that linearly moves with the ball screw under the axial driving force of the ball screw shaft. The bearing is formed between the cylindrical case member of the ball nut body, the mounting ring member fixed to the support frame, and the outer peripheral surface of the cylindrical case member and the inner peripheral surface of the mounting ring member. It is constituted by interposed rolling elements.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram showing a configuration of a forward / reverse drive device in an eject system of an injection molding machine according to one embodiment of the present invention, and FIG. 2 is an enlarged view of a main part of FIG.

1 and 2, reference numeral 1 denotes a movable die plate to which a movable die (not shown) is attached, 2 denotes a toggle link mechanism for moving the movable die plate 1 back and forth with respect to a fixed die plate (not shown), Reference numeral 3 denotes a bearing fitted in the holding hole of the movable die plate 1 to rotatably hold the ball nut body 4, reference numeral 4 denotes a ball nut body rotatably held by the bearing 3, and reference numeral 5 denotes a ball nut body 4. A pulley 6 for transmitting the rotation of a motor (not shown) is a ball screw shaft screwed to the ball nut body 4.

As shown clearly in FIG. 2, the bearing 3 has a part of the outer peripheral surface of the cylindrical case member 7 of the ball nut body 4 and a mounting fitting fitted into the holding hole of the movable die plate 1. It comprises a ring member 8 and a ball 9 located between the outer peripheral surface of the cylindrical case member 7 and the inner peripheral surface of the mounting ring member 8. Reference numeral 7a denotes an annular groove having an arcuate cross section formed on the outer peripheral surface of the cylindrical case member 7, and 8a denotes an annular groove having an arcuate cross section formed on the inner peripheral surface of the ring member 8 for attachment. The ball 9 is rollably fitted. In the present embodiment, the annular grooves 7a, 8a and the balls 9 which are symmetrically arranged in the drawing and the ball 9 constitute an angular bearing which also serves as a radial / thrust bearing, and the bearing 3 and the ball nut body 4 are integrated in advance. In this state, the movable die plate 1 is assembled into the holding hole of the movable die plate 1 at a time. Then, the mounting ring member 8 is fixed to the movable die plate 1 with the mounting bolts 10 so that the mounting ring member 8
Is more reliably held so that it cannot rotate and cannot move in the axial direction.

As described above, the integrated bearing 3
The pulley 5 is fixed to the ball nut body 4 rotatably mounted on the movable die plate 1 via mounting bolts 11, and the pulley 5 is an eject drive source mounted on the movable die plate 1. The rotation of a motor (not shown) is transmitted via a timing belt (not shown).

An eject pin (not shown) is connected to the end 6a of the ball screw shaft 6 via an appropriate connecting member, and the eject pin can move in and out of a movable mold (not shown). Has become.

In this embodiment having such a configuration,
At the timing when the resin injected and filled in the mold is cooled and solidified, the movable die plate 1 is driven via the toggle link mechanism 2 by the driving force of a motor (not shown) serving as a mold opening / closing drive source.
Is driven backward to open the mold, and after the mold opening is completed or during the mold opening, a motor (not shown) serving as an ejection drive source is rotationally driven in a predetermined direction. The rotation of the ejecting motor is transmitted to the pulley 5, and the ball nut body 4 is driven to rotate together with the pulley 5 in a predetermined direction. Then, by the rotation of the ball nut body 4, the ball screw shaft 6 is driven forward, whereby the eject pin (not shown) is driven forward, and the molded product is ejected from the movable mold. When the eject pin is returned, the motor serving as the mold opening / closing drive source is driven to rotate in the opposite direction, the pulley 5 and the ball nut body 4 rotate in the opposite direction, and the ball screw shaft 6 is driven backward. As a result, the eject pin is returned to a predetermined position.

In the present embodiment, as described above,
The bearing 3 is a cylindrical case member 7 of the ball nut body 4.
, An attachment ring member 8, and a ball 9. That is, in the present embodiment, the cylindrical case member 7 of the ball nut body 4 has the function of the inner ring of the conventional bearing shown in FIGS. The configuration is omitted. Therefore, as in the conventional case, when viewed from the rotating body when the pulley 5 is excluded, the radius D of the rotating body is reduced by the absence of the inner ring of the conventional bearing, and the weight M of the rotating body is reduced. since conventional reduced by an amount no inner ring of the bearing, it is small rotating body inertia moment M = GD ^2, thereby, the improvement of rotation → transient response of the linear motion converting mechanism (rising / falling characteristic) It becomes possible to plan. In addition, since the bearing 3 has a simple structure integrated with the ball nut body 4, assembly to the movable die plate 1 is simple and easy, and assemblability is improved.

In the above-described embodiment, an example has been described in which a ball is used as a rolling element of a bearing. However, a conical roller or the like can be used as a rolling element. Further, in the above-described embodiment, an example in which the rotation → linear motion conversion mechanism is applied to the eject system has been described, but it is also possible to apply the present invention to the mold opening / closing system and the injection system.
It is obvious to those skilled in the art.

The present invention is also applicable to a configuration in which a spline shaft coupling mechanism is added to the ball screw shaft of this mechanism in the above-mentioned rotation → linear motion conversion mechanism using a ball screw / ball nut.

That is, as in the other embodiment of the present invention shown in FIG. 3, in addition to the screw groove 6b for screwing the ball nut body 4 around the outer periphery of the ball screw shaft 6, a straight line along the axial direction is provided. The spline groove 6c may be formed together, and the rotation preventing member 21 may be connected to the spline groove 6c by a spline shaft, and the rotation preventing member 21 may be fixed to an appropriate holding frame member 22. With such a configuration, the rotation of the ball screw shaft 6 and the driven body connected to the ball screw shaft 6 can be prevented by the rotation preventing member 21 connected to the ball screw shaft 6 by a spline shaft. Since it is not necessary to provide a plurality of guide bars through which the driven body is guided and inserted to prevent the rotation, the mechanism of the machine can be reduced in size.

[0023]

As described above, according to the present invention, there is provided a molding machine using a rotation → linear motion conversion mechanism in which a ball nut body is pivotally supported and a ball screw shaft is moved forward and backward by rotation of the ball nut body. In the forward / reverse drive device, the moment of inertia can be reduced to improve the transient response and improve the performance of the machine. Further, the assemblability of the ball nut body can be improved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration of a forward / reverse drive device in an ejection system of an injection molding machine according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is an explanatory diagram showing a configuration of a forward and backward drive device in an injection molding machine according to another embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a configuration of a conventional rotation → linear motion conversion mechanism.

FIG. 5 is an enlarged view of a main part of FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Movable die plate 2 Toggle link mechanism 3 Bearing 4 Ball nut body 5 Pulley 6 Ball screw shaft 7 Cylindrical case member of ball nut body 4 8 Mounting ring member 9 Ball

Claims (2)

[Claims] 1. A ball nut body which rotates by receiving a rotational force of a motor, a ball screw shaft which is screwed to the ball nut body and moves in an axial direction by rotation of the ball nut body.
And a driven body that linearly moves with the ball screw under the axial driving force of the ball screw shaft. The bearing is formed between the cylindrical case member of the ball nut body, the mounting ring member fixed to the support frame, and the outer peripheral surface of the cylindrical case member and the inner peripheral surface of the mounting ring member. A forward and backward drive for a molding machine, comprising a rolling element interposed. 2. The spline groove along the axial direction is formed on the outer periphery of the ball screw shaft in addition to a screw groove for screwing the ball nut body together. A member connected to the spline groove in the spline shaft is fixed to an appropriate holding member so as to prevent the rotation of the ball screw shaft;