JPH022659B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a table transfer device, and in particular, to a table transfer device.
This invention relates to a table transfer device that allows accurate micro-feeding and rapid-feeding of a table of a machine tool or the like by using a lead difference between ball screws.

(Prior Art) Generally, various tables such as work tables in machine tools are often moved by a table transfer device using a ball screw. This table transfer device using a ball screw has one ball screw shaft rotatably supported on a fixed bed, a ball nut is screwed to this ball screw shaft via a steel ball, and The table is fixed to a ball nut. The ball screw shaft is rotationally driven by a stepping motor or a servo motor to reciprocate the ball nut together with the table in the axial direction, thereby obtaining a predetermined table feeding motion.

In devices using a stepping motor, when the stepping motor is rotated one step (in the case of a stepping motor with 800 divisions, the rotation angle is 360°/800 = 0.45°), the ball screw shaft also rotates at the same angle. The table is rotated and the table is moved axially by a certain distance in accordance with the lead of the ball screw shaft.

(Problem to be solved by the invention) However, there is a certain limit to the resolution of the stepping motor (minimum resolution of about 4 μm), and the conventional table transfer device as described above is required to perform fine feeding beyond a certain limit. I can't. Furthermore, the higher the resolution of the stepping motor is, the higher the speed of rotation is required to rapidly feed the table, and it becomes impossible to rapidly feed the table above a certain limit. Furthermore, a high-resolution stepping motor is itself extremely expensive, increasing the manufacturing cost of the entire device.

It is also possible to interpose a speed change gear between the stepping motor and the ball screw shaft to change the moving distance of the ball nut for a given rotation angle of the motor, thereby allowing minute or rapid feeding, but this would increase the size of the entire device. Not only that, but also the inevitable manufacturing errors of the transmission gear itself make it extremely difficult to achieve accurate minute feeds. Furthermore, due to the backlash between the gears, it is difficult to accurately transmit the rotational driving force of the motor to the ball screw shaft, which not only makes it impossible to accurately position the table, but also makes it difficult to accurately position the table. Bad sex.

Furthermore, if the lead of the screw is made small for minute feed, rapid feed becomes impossible and precise thread cutting becomes difficult, while on the other hand, if the lead of the screw is made large, minute feed becomes difficult. Further, when the ball screw shaft is rotated at high speed for rapid feeding, if the shaft rotation speed exceeds a critical speed, the ball screw shaft will cause resonance. Therefore, it must be used at a speed below the allowable rotation speed.
There were restrictions on fast table feed.

(Means for Solving the Problems) In order to eliminate the drawbacks of the conventional table transfer device, the table transfer device according to the present invention has the following features:
A drive source installation base that is attached to a fixed bed so as to be able to reciprocate in the same direction as the table, two rotary drive sources fixed on this drive source installation base, and each of these two rotary drive sources. Two ball screw shafts with different lead lengths are connected to the output shaft so as to extend in the table movement direction, and two ball screw shafts are screwed onto these two ball screw shafts and are connected to the fixed bed side and the table side, respectively. The table is equipped with two ball nuts fixed to the table, and is constructed so that the table can be precisely fed minutely or quickly by adjusting or adding the feed amounts of the two ball screws.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings.

As shown in FIGS. 1 to 3, a pair of tracks 2, 2 are arranged parallel to each other on the upper surface of the flanges 1a, 1a on both sides of the fixed bed 1. A table 4 is provided above so as to be movable in the axial direction along the tracks 2, 2 via four linear sliding bearings 3, 3, 3, 3.

As shown in FIG. 4, each of the linear sliding bearings 3 has load ball grooves 5 and non-load ball grooves 6 that extend in the axial direction formed alternately in the circumferential direction on the inner surface, and load balls adjacent to each other The groove 5 and the no-load ball groove 6 are continuously connected at both ends thereof, and each forms an endless loop. Further, each track base 2 is also formed with a ball rolling surface 7 corresponding to the load ball groove 5 of each bearing 3.
A large number of balls 8, 8, . . . are arranged between the ball rolling surface 7 and the no-load ball groove 6. Balls 8, 8, . . . are held by a retainer 9 between each bearing 3 and each track base 2. Therefore, when the bearings 3, 3, 3, 3 move in the axial direction on the tracks 2, 2, the balls 8, 8, . The ball enters the ball groove 6, moves there in the axial direction, and returns again between the load ball groove 5 and the ball rolling surface 7. In this way, the tracks 2, 2 of the table 4
smooth movement can be guaranteed.

The fixed bed 1 also has the flange 1.
Flanges 1b, 1b having a spacing width slightly narrower than the spacing width of flanges a, 1a are provided so as to extend to the right side in FIG. And this flange 1b, 1
Tracks 10, 10 are arranged parallel to each other on the track 10, and a drive source mounting base 12 is mounted on the track 10 in the same direction as the table 4 via two linear sliding bearings 11, 11. It is attached so that it can slide.

The linear sliding bearing 11 is a double-row angular type, and as shown in FIGS. 5, 6, and 7, two ball rolling grooves 13 are provided on one side.
13 is provided and a ball escape hole 14,1 is provided inside.
4, a retainer 16 that holds two rows of load balls, and a pair of side covers 17, 17 that communicate the ball rolling grooves 13, 13 and the ball escape holes 14, 14. It consists of The load balls 18, 18 are connected to the ball rolling groove 1.
3, 13 and ball escape holes 14, 14. This ball rolling groove 13,
The contact angle α between 13 and the load balls 18, 18 is approximately
Although the angle is 45 degrees, it is not limited to 45 degrees, and may be in the range of 30 to 60 degrees.

The drive source installation stand 12 is arranged below the table 4, and two stepping motors 20 and 21 are fixed to the upper surface thereof. The stepping motors 20 and 21 are divided into 1000 parts, that is, the rotation angle per step is 360 degrees/1000=
The angle used is 0.36 degrees. These stepping motors 20 and 21 are arranged substantially parallel to the moving direction of the table 4, and each output shaft 22 and 2
3 is oriented such that it projects towards the lower part of the table 4. Furthermore, a ball screw shaft 2 is connected to each output shaft 22, 23 of the stepping motors 20, 21 via coupling rings 24, 25.
6 and 27 are connected to each other. These ball screw shafts 26 and 27 are made of threaded bodies that are slightly longer than the table 4, and are arranged in parallel to each other directly below the table 4 so as to extend in the moving direction of the table 4. . Further, on the outer peripheral surfaces of both of these ball screw shafts 26, 27, a spiral ball screw groove (for example, right-handed thread) 28,
29 are engraved on each. The lead amount of one ball screw groove 28 is set to 4 mm,
The lead amount of the other ball screw groove 29 is set to 3.9 mm.

Further, ball nuts 31 and 32, which will be described later, are screwed onto both the ball screw shafts 26 and 27, respectively. Of these two ball nuts 31 and 32, one ball nut 31 is connected to the housing 33.
The other ball nut 32 is fixed to the lower surface of the table 4 via a housing 34.

The structure of the ball nuts 31 and 32 will be explained with reference to FIG. 8. The cylindrical ball nut 31 fitted on the outer periphery of the ball screw shaft 26 is a cylindrical first nut having an annular flange 35 at one end. An element body 36, and a cylindrical second nut element body 37 having a male thread carved on the outer periphery of one end into which the nut is screwed.
and an annular spacer 38 interposed between the first and second nut bodies 36 and 37. On the inner peripheral surfaces of the first and second nut bodies 36 and 37, spiral thread grooves 40 and 41 having the same lead as the spiral thread groove 28 on the outer periphery of the ball screw shaft 26 are formed in a spiral shape, respectively. At the same time, the thread grooves 40 and 41 and the thread groove 2 on the outer periphery of the ball screw shaft 26
A large number of steel balls 42, 42, . . . are arranged between the ball screw shaft 26 and the steel balls 42,
42, . . . are thread grooves 28, which correspond to each other in the ball screw shaft 26 and the first and second nut bodies 36, 37,
40 and 41 to move the ball nut 31 made up of the first and second nut bodies 36 and 37 in the axial direction with respect to the ball screw shaft 26. Further, the first and second nut bodies 36, 37 are urged in the direction of separating from each other by a spacer 38 inserted between them, and the steel balls 42, 42, . . . , 41, there is no backlash (axial gap), and the response when the ball nut 31 moves in the axial direction due to the rotation of the ball screw shaft 26 is improved.

Next, the operation of this embodiment will be explained.

First, consider the case where one stepping motor 20 is stopped and the other stepping motor 21 is rotated one step clockwise. Since the stepping motor 20 is stopped, the ball screw shaft 26 is held fixed to the ball nut 31, and the drive source mounting base 12 is fixed on the fixed bed 1 side via the ball nut 31 and the ball screw shaft 26. Can be stopped in position. On the other hand, the stepping motor 21 performs one step, that is, 360 degrees/
It is rotated by an angle of 1000=0.36 degrees, and the ball screw shaft 27 is also rotated by the same angle. And the ball nut 32 is 3.9mm x (0.36 degrees/360 degrees) = 0.0036
It is moved to the right by mm, and the table 4 is also moved to the right by the same distance. Conversely, when the stepping motor 21 is rotated one step counterclockwise, the table 4 is moved leftward by 0.0039 mm.

On the other hand, consider the case where when the stepping motor 20 is rotated clockwise, the stepping motor 21 is also rotated clockwise at the same time. The ball screw shaft 26 rotates 360 degrees/1000= for one step rotation of the stepping motor 20.
Since it is rotated clockwise by 0.36 degrees, the drive source installation base 12 is rotated to the left by 4 mm x (0.36 degrees/360
degree) = 0.004mm. Along with this, the table 4 is also moved to the left by 0.004 mm. Therefore, in this case, the table 4 is moved leftward by a difference of 0.0001 mm between the rightward movement distance of 0.0039 mm by the stepping motor 21 and the leftward movement distance of 0.004 mm by the stepping motor 20, which is extremely small. A large amount of feeding motion is performed.

Furthermore, if the stepping motor 20 is rotated to the left while the stepping motor 21 is rotated to the right,
This time, conversely, the table 4 is moved to the right by 0.004 mm for one step of leftward rotation of the stepping motor 20. Therefore, the table 4 has a rightward movement distance of 0.0039 mm due to the stepping motor 21 and a rightward movement distance of 0.004 mm due to the stepping motor 20.
mm and is moved to the right by the sum of 0.0079 mm, resulting in an extremely large rapid feed operation.

(Effects of the Invention) As described above, the table transfer device according to the present invention allows the table to be moved by the difference or sum of the respective table feed amounts by two ball screws having different lead amounts. Since one ball nut is fixed to the fixed bed side and the other ball nut is fixed to the table side, both minute and rapid table feeding can be performed extremely accurately, allowing for highly accurate and quick table positioning. becomes possible.

In addition, since there is no need to use a transmission gear between the ball screw shaft and the drive source, there is no delay in operation due to play or manufacturing errors in the transmission gear or clutch, and the response is extremely high compared to when a transmission is used. In addition to being good for this purpose, the entire device can be made compact. Furthermore, it is possible to make the lead smaller in order to minutely feed the ball nut, or to make the feeding movement more minute and accurate than when using a high-resolution stepping motor, and the manufacturing cost is also lower. be able to.

[Brief explanation of drawings]

1, 2, and 3 are a plan view, a front view, and a side view of a table transfer device according to an embodiment of the present invention, FIG. 4 is a half cross-sectional view of a bearing unit, and FIG. 5 is a half cross-sectional view of a bearing unit. side view,
Figure 6 is a partially cutaway plan view of the bearing unit.
7 is a sectional view taken along the line -- in FIG. 6, and FIG. 8 is an enlarged longitudinal sectional view of the ball nut. 1... Fixed bed, 2... Track platform, 3, 11...
...Bearing for linear sliding, 4...Table, 12
... Drive source installation stand, 20, 21 ... Stepping motor, 26, 27 ... Ball screw shaft, 31, 3
2... Ball nut.

Claims (1)

[Claims] 1. In a table transfer device in which a table mounted on a fixed bed so as to be reciprocally movable is moved by a predetermined distance by a ball screw interposed between the fixed bed and the table, a table is mounted on the fixed bed in the direction of table movement. A drive source installation stand mounted so as to be movable back and forth in the same direction, two rotary drive sources fixed on the drive source installation stand, and the above two rotary drive sources connected to respective output shafts of these two rotary drive sources. Two ball screw shafts with different lead amounts extending in the table movement direction, a ball nut screwed into one of these two ball screw shafts and fixed to the fixed bed side, A table transfer device comprising: a ball nut screwed onto a ball screw shaft and fixed to a table side.