JP2524273B2 - Ball screw - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ball screw used for transferring or tightening an object in a machine tool, a molding machine or the like.

[0002]

2. Description of the Related Art A conventional ball screw has a structure in which a screw shaft having a constant screw pitch and a nut are screwed through a large number of balls, and when one of them rotates, the other shaft is screwed. It is configured to move in the direction to transfer or tighten the object.

[0003]

The problem in this case is that since the screw pitch is constant, the feed rate and torque are always constant, and unless the rotational speed is changed, the feed rate, torque, etc. That is, it cannot be changed.

Such a problem has been solved by JP-A-63-3920.
As described in Japanese Patent Publication, when a screw having different screw pitches is provided at both ends of a screw shaft and nuts are provided on both of the screws, when the high speed and low torque are required, the screw pitch is rough . feed screw shaft by rotating the square nut, also when the low speed high torque is required, the screw pitch by rotating the screw shaft is to send out nut towards dense.

However, this conventional structure requires a means for rotating one of the nuts, a means for rotating the screw shaft, and a means for switching the rotation, so that the structure becomes complicated,
Also, it is troublesome in terms of operation.

The present invention was conceived in order to solve the above-mentioned conventional problems, and an object thereof is to change the feed pitch and torque automatically by partially changing the thread pitch of a series of screws. It is to provide a ball screw having a new configuration that can be performed.

[0007]

The present invention according to the above object provides a ball screw in which a screw shaft and a nut are screwed together through a large number of balls, and the screw pitch of the screw shaft is partially changed. At the same time, an elastic ball seat that allows the ball to move in the axial direction in response to a change in the screw pitch is provided inside the nut.

Further, the screw pitch of the screw shaft is coarse in the middle part and is densely provided in the end part, and the elastic ball seat is composed of a coil spring wound around the screw shaft along the screw pitch. Ball grooves are formed on the surface of the spring facing the thread pitch.

[0009] Such a ball screw, as with previous ball screw as possible out adopting such a feed mechanism or clamping mechanism of machine tools and molding machine.

[0010]

[Operation] In the above structure, the nut or the screw shaft is moved in the axial direction by the rotation of the screw shaft or the nut. The ball also moves relatively in the thread groove. When the thread pitch of the screw shaft changes, the spacing of the elastic ball seats is compressed or expanded axially by the balls in the groove and changes equally to the changed thread pitch.

Further, as the screw pitch is changed, the moving speed and the torque are also changed, so that the high speed low torque or the low speed high torque is automatically obtained.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawings, 1 is a screw shaft, 2 is a nut, and 3 and 3 are many balls made of steel balls . The screw shaft 1 has a series of screws 4 with the same groove width on the outer periphery. The screw pitch of the screw 4 is different between the intermediate portion and the end portion, the screw pitch 4a at the intermediate portion is coarse, and the screw pitch 4b at the end portion is dense.

The nut 2 is composed of a main body having a length extending over a plurality of screw pitches, and an inner elastic ball seat 5 which allows axial movement of the balls 3 and 3 in response to changes in the screw pitch. Has been done.

The ball seat 5 according to this embodiment includes a screw 4
The coil spring has a quadrangular cross section and is wound around the screw shaft 1 along the pitch (1), and the ball groove 6 is formed on the surface of the coil spring facing the thread pitch.

One end 5a of the coil spring is fixed to the end of the nut, whereby the ball seat 5 rotates together with the nut 2, while the ball seats 3 and 3 contract or expand in the axial direction by the pressure of the balls 3 and 3.

The lateral width of the ball seat 5 formed by this coil spring is determined in accordance with the dense screw pitch 4b, and when the balls 3 and 3 are located at the screw pitch 4b, as shown in FIG.
As shown in FIG. 5, the ball seats 5 are designed to be completely contracted so that the ball seats 5 are in contact with each other.

A long hole 8 of a return guide 7 is bored in the nut 2 in the axial direction. The return guide 7 is composed of a pipe spirally wound around the outer periphery of the nut, one end of which is fixedly connected to a guide hole 9 at the end of the nut, and the other end of the pipe extends from the elongated hole 8 to the free end of the ball seat 5. It is connected to the ball hole 10 penetrating therethrough so as to move axially together with the ball seat 5.

Such a ball screw is used by connecting either one of the screw shaft 1 and the nut 2 to the movable member side and the other to the rotating means of the fixed member, and the screw shaft 1 is rotated at a fixed position. At this time, when the nut 2 and, conversely, when the nut 2 rotates in a fixed position, the screw shaft 1 linearly moves in the axial direction.

As the screw shaft 1 or the nut 2 moves, the balls 3 and 3 also move relatively in the axial direction. Further, since the ball seat 5 is also movable in the axial direction, the balls 3 and 3 in the screw groove can be contracted or expanded in the axial direction.

Therefore, the ball seat 5 is composed of the balls 3, 3
Since the distance is adjusted to the screw pitches 4a and 4b while receiving the balls, the relative positions of the screw grooves on the screw shaft side and the ball seating side do not shift, and the balls 3 do not bite. Even if the screw pitch changes in the middle of the screw 4, the movement of the screw shaft 1 or the nut 2 is not hindered, and the speed and torque change automatically and smoothly.

The return guide 7 also has a nut 2 at one end.
Is fixed to the guide hole 9 and the other end is connected to the ball hole 10 of the ball seat 5, and the ball seat 5 allows the other end to move axially in the elongated hole 8. It expands and contracts in the axial direction together with the ball seat 5. Further, since the lengths of the ball seat 5 and the return guide 7 do not change, the balls 3, 3 can be smoothly returned regardless of the change in the distance between the ball seat 5 and the return guide 7.

FIG. 4 and subsequent figures show an embodiment in which the ball screw of the present invention is used in a mold clamping device of a molding machine.

In the figure, 21 and 22 are fixed plates, 23 is a movable plate,
Reference numeral 24 is a split mold attached to the opposing surfaces of the fixed platen 22 and the movable platen 23, and 25 is a tie bar.

In the ball screw used here, the thread pitch of the series of screw shafts 1 is coarsely formed at the intermediate thread pitch 4a and densely formed at the both end thread pitches 4b for the purpose of low-speed mold opening and closing.

FIG. 4 shows a case where the ball screw having a large diameter is used as a single mold clamping ram. The screw shaft 1 is connected to the center of the back part of the movable platen 23, and the nut 2 is fixed to the fixed platen 21. It is rotatably installed in the center. Further, a mold clamping motor 26 such as a servo motor is attached to the fixed platen 21, and the nut 2 is rotated at a fixed position by the mold clamping motor 26 via a transmission member 27 such as a timing belt, whereby the screw shaft 1 is rotated. Move linearly in the direction to move the movable platen 23,
The molds 24 and 24 are configured to be opened and closed and clamped .

FIG. 5 shows a plurality of screw shafts 1, 1 having a small diameter.
Is used as a mold clamping rod in parallel with the back of the movable plate 23,
1 shows a mold clamping device in which the nuts 2 and 2 are rotatably arranged side by side on a fixed platen 21. In order to prevent the screw shafts 1 and 1 from being twisted, the screw shafts 1 and 2 are turned in opposite directions. 1 is provided.

In this case as well, although not shown in the drawing, the rotation of the nuts 2 and 2 is performed by a mold clamping motor via a timing belt or the like, and the rotation causes the screw shafts 1 and 1 to linearly move in the axial direction. The molds 24, 24 are opened and closed and the mold is clamped.

FIG. 6 shows a case in which part of the mold clamping rods 28, 28 provided at the four corners of the fixed platen 22 is the screw shafts 1, 1, and the movable platen 23 of the mold clamping rods 28, 28 is shown. Of the movable platen 23 is rotatably provided at the four corners of the movable platen 23, while the guide parts of the movable platen plate are screw shafts 1 and 1.
3, a mold clamping motor 26 is attached, and the nuts 2 and 2 are rotated by the mold clamping motor 26 via a transmission member 27, and the movable platen 23 is moved on a screw shaft in a fixed position, and the mold 24,
It has a structure capable of opening and closing 24 and clamping.

Also in this case, in order to prevent the screw shafts 1 and 1 at the four corners from being twisted, the diagonal screw shafts are provided with the directions of the screws 4 being opposite to each other.

In each of the above mold clamping devices, the series of screws 4 of the screw shaft 1 are formed more densely at both end portions than in the intermediate portion, so at the beginning of mold closing, the movable platen 23 is operated at low speed and high torque.
Moves. Then, when it moves to the roughly formed intermediate part, the speed becomes high, and when it reaches the end part, the speed is automatically reduced because it is densely formed, and the mold 2
The molds 4 and 24 are slowly closed, and the mold is clamped with a higher torque.

In FIGS. 4 and 6 , 29 is a mold thickness adjusting screw provided in the movable plate guide portion of the tie bars 25, 25, 30 is a mold thickness adjusting motor attached to the movable plate 23, 31
Mold thickness adjusting nut which is penetrated rotatably threaded shaft insertion portion of the movable plate 23, 32 is a rotating diversion belt provided over a mold thickness adjusting motor 30 and the mold thickness adjustment nut.

[0032]

As described above, according to the present invention, a series of screw pitches of the screw shaft are provided by partially changing the elasticity, and a large number of balls are elastic to allow the axial movement in accordance with the change of the screw pitch. Even if the pitch of a series of screw pitches is changed on the way, the ball seat of
Since the ball is configured to move smoothly in the thread groove of the thread pitch, the speed and torque can be automatically switched without providing a plurality of rotating means and switching means.

Further, the rotating means may be the same as that of the conventional constant speed, and since it does not require a switching device or the like, the structure is not particularly complicated, so that it can be easily applied as a feeding means for various devices.

Furthermore, since the ball seat is made of an elastic material such as a coil spring, an elastic force is exerted at the time of starting, so that not only a smooth starting can be realized but also a shock at the time of gear shifting or voltage change can be absorbed, It has features such as removing rush.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view of a main part of a ball screw according to the present invention.

FIG. 2 is a vertical cross-sectional side view of a main part when the distance between the ball seats changes according to the screw pitch.

FIG. 3 is a vertical sectional end view of the above.

FIG. 4 is a schematic cross-sectional view showing a main part of a mold clamping device when the ball screw of the present invention is used for a large-diameter mold clamping ram of a molding machine when the mold is opened and when the mold is closed. FIG.

FIG. 5 is a schematic plan view showing a cross section of a main part of the mold clamping device when the mold is closed when a plurality of mold clamping rods are used.

FIG. 6 is a schematic plan view showing a cross section of a main part of a mold clamping device when the mold clamping device is used as a mold clamping rod at four corners of the stationary platen when the mold is opened and when the mold is closed.

[Explanation of symbols]

 1 Screw Shaft 2 Nut 3 Ball 4 Screw 4a Coarse Screw Pitch 4b Dense Screw Pitch 6 Screw Groove 7 Return Guide 8 Long Groove 9 Guide Hole 10 Ball Hole

Claims (3)

(57) [Claims] 1. A ball screw in which a screw shaft and a nut are screwed together through a large number of balls, and the screw pitch of the screw shaft is partially changed to be provided in series, and a change in the screw pitch is dealt with. A ball screw characterized in that an elastic ball seat for allowing the axial movement of the ball is provided in the nut. 2. A thread pitch of the screw shaft is rough in the middle portion of claim 1, wherein the ball screw, characterized in that has been found densely provided at the ends. 3. The elastic ball seat comprises a coil spring wound around a screw shaft along a screw pitch, and a ball groove is formed on a surface facing the screw pitch of the coil spring. Ball screw.