JPS61236443A - Table transfer device - Google Patents

Abstract

PURPOSE:To make possible to precisely feed a table with both fine feed amount and fast feed amount, by transferring the table by an amount corresponding to the difference between or the sum of table feed amounts of two ball screws having different lead amounts from each other. CONSTITUTION:A drive source mounting bed 12 is attached on a stationary bed 1 so that it is reciprocatable in the same directions as the moving direction of a table 4. Two stepping motors 20, 21 are secured to the drive source mounting bed 12. Two ball screw shafts 26, 27 having different lead amounts in the moving direction of the table 4 are coupled to the output shafts of the stepping motors 20, 21, respectively. A ball nut 31 is threadedly engaged with the ball screw shaft 26, and is secured to the stationary bed 1 side. Meanwhile a ball nut 32 is threadedly engaged with the ball screw shaft 27, and is secured to the table 4 side.

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 for a machine tool, etc., which can be used for micro-feeding or rapid-feeding using a lead difference between two ball screws. The present invention relates to a table transfer device that can be used accurately.

(Prior Art) Generally, various tables such as work tables in machine tools are often moved by a T-table transfer device using a ball screw. The table transfer device using this ball screw is rotatably supported on a fixed bed and has a single ball screw shaft.A ball nut is screwed to this ball screw shaft via a steel ball. The table is fixed to the pole nut. The ball screw shaft is rotationally driven by a stepping motor or a servo motor to reciprocate the pole nut in the axial direction together with the table, 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 degrees), 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 cannot perform micro-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 feed the table faster than 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 movement distance of the ball nut for a given rotation angle of the motor, thereby allowing minute feeding and transportation, but this would increase the size of the entire device. Not only that, but it is extremely difficult to achieve accurate minute feeds due to unavoidable manufacturing errors in the transmission gear itself. Furthermore, backlash between the gears makes it difficult to accurately transmit the rotary driving force of the motor to the ball screw shaft, which not only makes it impossible to accurately position the table, but also prevents the rotation of the motor from rotating when changing the direction of rotation of the ball screw shaft. poor responsiveness.

Furthermore, if the lead of the screw is made small, it will not be possible to perform fast feed, and precise thread cutting will become difficult. On the other hand, if the lead of the screw is made large, minute feed will become difficult. Furthermore, when the ball screw shaft is rotated at high speed for rapid feed, if the shaft rotation speed exceeds a critical speed, the ball screw shaft will cause resonance. For this reason, it had to be used at a rotational speed below the allowable rotation speed, and there were restrictions on the rapid feeding of the table.

(Ninth Means for Solving the Problems) Statement 1 to Eliminate the Disadvantages of the Conventional Table Transfer Device The table transfer device according to the present invention is attached to a fixed bed so as to be movable back and forth in the same direction as the table. 7
A tlK power source installation base, two rotary drive sources fixed on this drive source installation base, and connected to each output shaft of these two rotary drive sources so as to extend in the direction of movement of the table. two ball screw shafts with different lead amounts,
It is equipped with two pole nuts that are screwed onto these two ball screw shafts and fixed to the fixed bed side and the table side respectively, and the table can be adjusted accurately by adjusting the feed amount of the two ball screws or by adding them together. It is configured to be able to perform minute feeding or rapid feeding.

(Example) Embodiments of the present invention will be described in detail below with reference to the drawings.

As shown in FIGS. 1 to 3, on the upper surface of seven langes la and la on both sides of the fixed bed 10, a pair of tracks 2
2 are arranged parallel to each other, and on both tracks 2.2, a cheagle 4 is mounted along the tracks 2, 2 via four straight sliding bearings 3, 3, 3.3. It is provided so that it can move in the axial direction.

As shown in FIG. 4, each of the above-mentioned linear sliding bearings 3 has load ball grooves 5 and non-load pawls 86 that extend in the axial direction on the inner surface and are alternately formed in the circumferential direction, and load ball grooves that are adjacent to each other. 5 and the no-load ball groove 6 are continuously connected at both ends thereof, and each forms an endless loop. Also, on each track 2,
Four ball rolling surfaces 7 are formed corresponding to the loaded ball grooves 5 of each bearing 3, and a large number of balls 8, 8 are located between the loaded ball grooves 5 and the pawl rolling surfaces 7 and within the non-load ball grooves 6. ．． ...... will be arranged. Between each bearing 3 and each track 2, there is a retainer 9 with a ball 818.
．． ... is maintained. Therefore bearing 3
, 3, 3.3 moves in the axial direction on the track 2.2,
Ball 8.8. . . . rolls between the loaded ball groove 5 and the ball rolling surface 7, enters the unloaded ball groove 6, moves there in the axial direction, and rolls again with the loaded ball groove 5. It is designed to return to the 7th floor. In this way a smooth movement of the table 4 relative to the track 2.2 can be ensured.

The 1L fixed pedestal 1 has the flange 1m long.

Flange lb having a spacing width slightly narrower than the spacing width of la
, lb are provided so as to extend to the right side in FIG. And on this flange lb, lb is a track base 10.1.
0 are arranged parallel to each other, and the track 10IC is installed so that the drive source installation base 12 can slide in the same direction as the table 4 via two linear sliding bearings 1, 1, 11. It is being

The linear sliding bearing 11 is a double row angular type, and as shown in FIGS. 5, 6 and 7,
A hole bearing block 15, which has two ball rolling grooves 13.13 on one side and ball relief holes 14 and 14 inside, a retainer 16 that holds two rows of loaded balls, and a pole rolling groove. It is composed of a pair of side covers 17, 17 which communicate the running grooves 13, 13 and the ball escape hole 14°14. The load pole 18.18 circulates between the ball rolling groove 13.13 and the ball relief hole 14.14. The contact angle α between the pole rolling grooves 13, 13 and the load ball 18.18 is approximately 4.5 degrees, but it is not limited to 45 degrees, and may be in the range of 30 to 60 degrees. Bye.

The drive source installation stand 12 is arranged below the table 4, and two stepping motors 20.
21 is fixed. This stepping motor 20.
21 is divided into 1000, that is, the rotation angle per l step is 360 degrees/'1000=0.36 degrees. Both stepping motors 20.2
1 is arranged substantially parallel to the moving direction of the table 4, and each output shaft 22.

23 is oriented such that it projects towards the lower part of the table 4. Furthermore, both stepping motors 20
．． 21, each output shaft 22.23 is provided with a coupling 24.23.
Ball screw shafts 26 and 27 are connected via 25, respectively. These ball screw shafts 26 and 27 are screw bodies that are slightly longer than the table 4.
They are arranged parallel to each other directly below the table 4 so as to extend in the moving direction of the table 4. 1L Spiral ball screw grooves (for example, right-handed threads) 28 and 29 are formed on the outer peripheral surfaces of both ball screw shafts 26 and 27 over substantially the entire length. The lead amount of one ball screw groove 28 is set to 4.times., and the lead amount of the other ball screw groove 29 is set to 3.9 tm.

Furthermore, ball nuts 31 and 32 (described later) are respectively screwed onto both of the ball screw shafts 26 and 27. Of these two pole nuts 31.32, one ball nut 31f1. The pole nut 32 is fixed to the upper surface of the fixed ped 1 via the /S housing 33, and the other pole nut 32 is fixed to the lower surface of the table 4 via the housing 3-4.

Regarding the composition of Ball Nara) 31 (32'), Part 8
To explain with reference to the figure, a cylindrical pole nut 31 fitted on the outer periphery of the ball screw shaft 26 has an annular 7
A cylindrical first nut body 36 having a flange 35, a cylindrical second nut body 37 having a male thread carved on the outer periphery of one end into which the nut is screwed; It consists of a T-ring-shaped spacer 38 interposed between the second nut bodies 36 and 37. 1st. 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 spirally formed on the inner peripheral surfaces of the second nut bodies 36 and 37, respectively. In addition, a large number of steel balls 42, 42. ...... are arranged, and as the ball screw shaft 26 rotates, the steel balls 42, 42° ... are connected to the ball screw shaft 26 and the first... The second nut body 36.37 rolls in the corresponding thread grooves 28, 40.41, and the first
．． Second nut body 36. , 37 Yoshi Naru Paul Natsutto 3
1 in the axial direction of the ball screw shaft 26. Well, first. The second nut bodies 36, 37 are urged away from each other by a spacer 38 inserted between them, and the steel balls 42, 42. ...... and screw groove 2
There is no backlash (axial gap) between 8 and 40°41.

The rotation of the ball screw shaft 26 improves the responsiveness when the pole nut 31 moves in the axial direction.

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 connected to the ball nut 3.
1 and these pole nuts 3
1 and a ball screw shaft 26, the drive source installation base 12 is fixed at a fixed position on the fixed bed 1 side. On the other hand, the stepping mode, 21, is 1 step, that is, 360 degrees/1
000=α Rotated by an angle of 36 degrees, ball screw shaft 2
7 is also rotated by the same angle. And Paul Nut 3
2 is 3.9■X (0.36 degrees/36o degrees) = 0, O
It is moved to the right by O39-, and the table 4 is also moved to the right by the same distance. Conversely, if the stepping motor 21 is rotated one step counterclockwise, the table 4 will move to the left.
．． 0039 positions are moved.

On the other hand, consider a case where the stepping motor 21 is also rotated clockwise at the same time as the stepping motor 2o rotates clockwise. The ball screw shaft 26 is fixed to the ninth fixed bed L side, which is rotated to the right by 360 FV1000 = 0.36 degrees per one step rotation of the stepping motor 20.
Due to the threaded relationship with 1.

The drive source installation stand 12 is 4■X (0.36tL) toward the left.
/360 degrees) = 0.004 m. Along with this, Cheezle 4 is also moved to the left by 0.004■. Accordingly, in this case, the table 4 is moved to the left by a difference of 0.0001 m between the rightward movement distance by the stepping motor 21 of 0.0039 and the leftward movement distance α004■ by the stepping motor 20. .

An extremely small amount of feeding operation is performed.

Further, when the stepping motor 21 is rotated to the right, the stepping motor 20 is rotated to the left.

This time, conversely, the table 4 is moved to the right α00411IB in response to one step left rotation of the stepping motor 20. This third table 4 is the sum α00 of the rightward movement distance α0039 m by the stepping motor 21 and the rightward movement distance 0.004 by the stepping motor 20.
It is moved to the right by 79 ■, and an extremely large continuous feeding operation is performed.

(Effect of the invention) As described above, the table transfer fold f according to the present invention is as follows:
One pole nut is fixed to the fixed bed side, and the other pole nut is fixed to the table side, so that the table can be moved by the difference or sum of the table feed amounts caused by two ball screws with different lead amounts. Therefore, both minute and rapid table feeding can be performed extremely accurately, and highly accurate and rapid table positioning is possible.

Additionally, 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. For convenience, the entire device can be packed into a compact VC. Furthermore, it is possible to make the lead smaller in order to minutely feed the pole nut, or to make the feed operation more minute and accurate than when using a high-resolution stepping motor, and to reduce the manufacturing cost. I can do it.

[Brief explanation of the drawing]

FIGS. 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 the bearing unit, FIG. 5 is a side view of the bearing unit, and FIG. 6 is a partially cutaway view of the bearing unit. FIG. 7 is a sectional view taken along line II in FIG. 6, and FIG. 8 is an enlarged vertical sectional view of the pole 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 31.32...Pole nut.

Claims (1)

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