JPH0854016A - Feed drive device - Google Patents

Abstract

PURPOSE:To prevent application of excessive compressive force to a bearing and generation of radial clearance. CONSTITUTION:Pretension is supplied to a ball screw 8 by means of a nut 10. When the pretension is eliminated through extention of the ball screw 8 due to thermal expansion, compressive force is applied to bearings 4, 7. A disc spring 24 is flexured and receives the compressive force, so that excessive compressive force is not applied to the bearings. A compression ring 27 pushes an outer ring 6b of the bearing 6 to the side of the disc spring 24, so that radial clearance is not generated between an inner ring 6a and the outer ring 6b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a feed drive device having a heat compensation function using a ball screw.

[0002]

2. Description of the Related Art As a feed drive device using a ball screw, those shown in FIGS. 3 and 4 are conventionally known. FIG.
The feed drive device of is a double anchor feed drive device, and includes bearing housings 2 and 3 integrally fixed to the base 1 at a required interval, and two bearings in which the inner ring and the outer ring are arranged in the same direction. One set of two bearings in which the inner ring and the outer ring are arranged in the same direction opposite to the two bearings are set as one set, and the inner rings 4a and 5a of the bearings adjacent to each other are brought into contact with each other (front combination). )
Bearings 4,5,6,7 respectively mounted in mounting holes 2a, 3a of bearing housings 2,3, shafts 8a at one end of inner rings 4a, 5a of bearings 4,5, and other bearings 6,7. The inner ring 6a, 7a of the other end of the shaft portion 8b
Respectively, and the shaft portion 8a is fixed to the inner rings 4a, 5a by tightening the inner rings 4a, 5a of the bearings 4, 5 with the nut 9 screwed to the screw portion 8c.
By tightening the inner rings 6a, 7a of the bearings 6, 7 with the nut 10 screwed to the other threaded portion 8d, the shaft portion 8b is fixed to the inner rings 6a, 7a and rotated in the circumferential direction between the bearing housings 2, 3. The ball screw 8 freely erected and attached to the mutually facing open ends of the bearing housings 2 and 3 by a plurality of bolts 11 and 12 (only one is shown in the drawing), and each bearing 4 , 5, 6, 7 outer rings 4b, 5b, 6b, 7
The bearing retainers 13 and 14 for tightening b on the outside of the ball screw 8 to apply pre-tension to the ball screw 8 and the ball screw 8 are screwed together and move along the ball screw 8 by the circumferential rotation of the ball screw 8. The movable nut 15 and a drive motor (not shown) for rotating the ball screw 8 in the circumferential direction are provided.

The feed drive device of FIG. 4 is a single anchor type feed drive device, and the bearings 7, 7 of the bearing housing 3 of the feed drive device of FIG.
It has been changed to 6.

[0004]

3 and 4, the feed drive device of FIGS.
Since the pre-tension is applied to the ball screw 8 by the tightening of the ball screw 14, even if the ball screw 8 may expand due to thermal expansion, if the extension is within the range of the pre-tension, the expansion of the ball screw 8 is pre-determined. Since the change in internal stress is absorbed by the tension, the movement error (thermal displacement) of the movable nut 15 can be suppressed to a small level.

However, the extension of the ball screw 8 is large,
When the pretension is released, there is a disadvantage that excessive compression force (axial load) is applied to the bearings 4 and 7 in the feed drive device of FIG. Further, in the case of the feed drive device of FIG. 4, although there is no fear of the above, the inner ring 6a of the bearing 6 is the outer ring 6a.
Since it moves outward (to the right in FIG. 4) with respect to b, a gap is created in the radial direction.

The present invention provides a feed drive device in which, after the pretension applied to the ball screw is released, an excessive compressive force is not applied to the bearing and a radial gap is not formed in the bearing. The purpose is to

[0007]

In order to achieve the above object, the present invention provides a first bearing housing and a second bearing housing, which are integrally fixed to a base with a required space, and inner rings. Two or more first bearings mounted in the mounting holes of the first bearing housing as a front combination to be brought into contact with each other, and two front bearings mounted in the mounting holes of the second bearing housing as a front combination in which the inner rings are brought into contact with each other. Insert one or more first shaft portions into the inner ring of the first bearing and two or more second bearings and the second shaft portion of the other end into the inner ring of the second bearing, and screw them into the first screw portion. The first shaft portion is fixed to the inner ring of the first bearing by tightening the inner ring of the first bearing with the first nut, and the second nut is screwed to the second screw portion. Screwing the second shaft portion to the inner ring of the second bearing by tightening the inner ring of the second bearing with the screw and rotatably installed in the circumferential direction between the first bearing housing and the second bearing housing, A first bearing retainer that is attached to the opening end of the first bearing housing facing the second bearing housing by a first bolt and that fastens the outer ring of the first bearing to the one end side of a ball screw; and a first bearing retainer provided on the second bearing housing. A compression member inserted between the stepped portion and the outer ring of the innermost second bearing facing the stepped portion, and the second bearing housing is attached by a second bolt to attach the outer ring of the second bearing to the compression member. A second bearing retainer that is pressed against the compression member via a spring, and is screwed to the ball screw, A movable nut which moves along the ball screw by the rotation of the circumferential direction of the Lumpur screw was configured to have and a driving motor for rotating the ball screw in the circumferential direction.

The spring may be a disc spring. The second shaft portion of the ball screw inserted in the inner ring of the second bearing,
It is preferable that the inner ring of the second bearing is fixed by tightening the inner ring of the second bearing with the second nut screwed to the second screw part and the third nut screwed to the third screw part. Further, the drive motor may be configured such that the output shaft is connected to the ball screw by a coupling and attached to the first bearing housing.

[0009]

When the pretension applied to the ball screw is removed by the expansion of the ball screw due to heat and a compressive force is applied to the bearing, the spring receives the compressive force and bends according to the magnitude of the compressive force. Therefore, the bearing is not subjected to an excessive axial load. Also, when extending the ball screw,
Since the compression member pushes the outer ring of the bearing back toward the spring,
There is no radial clearance in the bearing.

When the disc spring is used as the spring, it is possible to easily obtain an appropriate force against the compressive force due to the thermal expansion of the ball screw. When the inner ring of the second bearing is tightened with the second nut and the third nut, the fixing position of the second shaft portion of the ball screw with respect to the inner ring of the second bearing can be adjusted.

If the drive motor is mounted on the first bearing housing and its output shaft is connected to the ball screw by a coupling, the structure of the rotary drive system of the ball screw becomes simple and the extension of the ball screw causes the drive motor to move. There is nothing like that.

[0012]

1 and 2 show an embodiment of a feed drive device according to the present invention. Members and the like having the same basic structure and function as those of the feed drive device of FIGS. 3 and 4 are designated by the same reference numerals, and detailed description thereof will be omitted.

Reference numeral 21 is a bearing retainer. The bearing retainer 21 includes a plurality of bolts 23 (shown in FIG.
Only books are shown. ), The outer rings 6b, 7b of the bearings 6, 7 are pressed against the stepped portion 3b of the bearing housing 3 via a plurality of disc springs 24 and the collar 25. The bearing retainers 13 and 21 are, as shown in FIG. 2, the outer rings 4b and 5 of the bearings 4, 5, 6 and 7, respectively.
A gap δ formed in the normal state between b, 6b, and 7b
1 and δ2 are eliminated (FIG. 1 is a state where there are no gaps δ1 and δ2), and the outer rings 4b, 5b, 6b and 7b are attached to the bearing housings 2 and 3 by abutting each other.

The step 3c of the bearing housing 3 and the outer ring 6 of the innermost bearing 6 of the bearing housing 3
A compression ring (compression member) 27 is provided between the b and b. Elasticity is imparted to the compression ring 27 by the notches 27a and 27b. As shown in FIG. 2, the compression ring 27 is formed such that its width is slightly larger than the distance between the stepped portions 3b and 3c formed in the bearing housing 3 in the normal state, and is pressed by the disc spring 24 as shown in FIG. It is compressed between the step portions 3b and 3c.

The ball screw 8 has a step portion 8e, a screw portion 8f, and a connecting portion 8g in addition to the shaft portions 8a and 8b and the screw portions 8c and 8d. The stepped portion 8e is a collar 28 for tightening the inner rings 4a, 5a of the bearings 4, 5 with the nut 9.
Receive through. A nut 29 is screwed onto the screw portion 8f. The nut 29 tightens the inner rings 6a and 7a of the bearings 6 and 7 via the collar 30 to fix the other nuts 1
Shaft part 8b of ball screw 8 on inner rings 6a, 7a in cooperation with
Is fixed.

The connecting portion 8g is provided at the end of the ball screw 8 on the bearing housing 2 side, and is connected to the output shaft 33 of the drive motor 32 via the coupling 31. The drive motor 32 is attached to the bearing housing 2.

Reference numeral 34 is a moving body to be fed, which is attached to the movable nut 15. Code 3
5 and 36 are seal members, which are provided between the bearing retainer 13 and the collar 28 and between the bearing housing 3 and the collar 3.
The space between 0 is sealed.

The thickness of the spacer 22 is set by the disc spring 24 so that an appropriate preload acts on the bearings 6, 7. Further, the force of the disc spring 24 is equal to that of the ball screw 8
Is set so that the bearings 4 and 7 are not subjected to an excessive axial load when they are expanded by thermal expansion.

Next, the operation of the feed drive device according to the present invention having the above-mentioned structure will be described. FIG. 1 shows an assembled state of the present feeding drive device, in which the ball screw 8 is pretensioned by being tightened by a nut 10. Therefore, even if the ball screw 8 expands due to thermal expansion, if the expansion is within the range of the pretension, the movement error of the movable nut 15 is suppressed to the minimum.

When the extension of the ball screw 8 exceeds the pretension and comes off, a compressive force is applied to the bearings 4 and 7,
The disc spring 24 bends and receives the compressive force. Therefore, an excessive compression force does not act on the bearing. Then, at this time, the compression ring 27 pushes the outer ring 6b of the bearing 6 which has been pushed by the disc spring 24 to the right in FIG. Therefore, the outer ring 6b follows the inner ring 6a of the bearing 6 that has moved to the right in FIG. 1 due to the extension of the ball screw 8, and no radial gap is created in the bearing.

Further, since the ball screw 8 only extends to the bearing housing 3 side, the drive motor 32 mounted on the bearing housing 2 is not affected.

The nuts 10 and 29 make it possible to adjust the fixing position of the shaft portion 8b of the ball screw 8 with respect to the inner rings 6a and 7a of the bearings 6 and 7 in accordance with the installation interval of the bearing housings 2 and 3. However, in the case where the bearing housings 2 and 3 are fixed to the base 1 such that the installation intervals thereof are adjustable, for example, the collar 30 is brought into contact with the step portion 8h of the ball screw 8 to make the nut 29.
Can be omitted.

The compression ring 27 may be another compression member such as a disc spring or the disc spring 24 may be another spring member such as the compression ring 27. The number of bearings used is not limited to that shown in the figure. The type of bearing mounted in the bearing housing is not limited to the angular ball bearing shown in Fig. 1, but it is a conical roller bearing, a thrust ball bearing and a radial ball or roller bearing, a thrust cylindrical roller bearing and a radial ball or roller bearing. It may be a combination of bearings or the like.

[0024]

As described above, according to the first aspect of the present invention.
Since the feed drive device according to the above is configured as described above,
Even if the pre-tension applied to the ball screw is released by the expansion due to the thermal expansion of the ball screw, the bearing is not subjected to excessive compressive force, and no radial gap is created in the bearing. .

When the spring is a disc spring, a force adapted to the compressive force generated by the thermal expansion of the ball screw can be easily obtained, and the structure, design and manufacture of the device can be simplified.

When the inner ring of the second bearing is tightened with the second nut and the third nut, the fixing position of the second shaft portion of the ball screw with respect to the inner ring of the second bearing is set by installing the first and second bearing housings. The distance can be adjusted correctly. Further, when the drive motor is attached to the first bearing housing without the spring mounted and the output shaft is connected to the ball screw by the coupling, the structure of the rotary drive system of the ball screw becomes simple, and the extension of the ball screw is achieved. Does not affect the drive motor.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a feed drive device according to the present invention.

FIG. 2 is a cross-sectional view of a compression ring.

FIG. 3 is a cross-sectional view of a conventional double anchor type feed drive device.

FIG. 4 is a sectional view of a conventional single anchor type feed drive device.

[Explanation of symbols]

 1 Base 2, 3 Bearing housing 2a, 3a Mounting hole 4, 5, 6, 7 Bearing 4a, 5a, 6a, 7a Inner ring 4b, 5b, 6b, 7b Outer ring 8 Ball screw 8a, 8b Shaft part 8c, 8d, 8f Screw Part 8g Connection part 9,10 Nut 11 Bolt 13 Bearing retainer 15 Movable nut 21 Bearing retainer 23 Bolt 24 Disc spring 27 Compression ring (compression member) 29 Nut 31 Coupling 32 Drive motor 33 Output shaft

Claims (4)

[Claims] 1. A first bearing housing and a second bearing housing, which are integrally fixed to a base at a required interval, and a front combination for bringing inner rings into contact with each other, and are mounted in a mounting hole of the first bearing housing. Two or more first bearings and two or more second bearings mounted in the mounting holes of the second bearing housing as a frontal combination for bringing the inner rings into contact with each other, and one end of the inner ring of the first bearing. By inserting the first shaft portion and the second shaft portion at the other end into the inner ring of the second bearing, and tightening the inner ring of the first bearing with the first nut screwed to the first screw portion, The shaft part is fixed to the inner ring of the first bearing, and the inner ring of the second bearing is tightened by the second nut screwed to the second screw part. A screw fixed to the inner ring of the second bearing so as to be rotatably mounted in the circumferential direction between the first bearing housing and the second bearing housing, and an opening facing the second bearing housing of the first bearing housing. A first bearing retainer that is attached to the end by a first bolt and tightens the outer ring of the first bearing to the one end side of the ball screw; and a step portion provided in the second bearing housing and an innermost inner surface facing the step portion. A compression member inserted between the outer ring of the second bearing and a second bearing retainer that is attached to the second bearing housing by a second bolt and presses the outer ring of the second bearing against the compression member via a spring. And is attached to the ball screw, and moves along the ball screw by the rotation of the ball screw in the circumferential direction. That a movable nut feed drive system being characterized in that includes a drive motor for rotating the ball screw in the circumferential direction. 2. The feed drive device according to claim 1, wherein the spring is a disc spring. 3. The second shaft portion of the ball screw inserted into the inner ring of the second bearing comprises a second nut screwed to the second screw portion and a third nut screwed to the third screw portion. 3. The feed drive device according to claim 1, wherein the feed drive device is fixed to the inner ring of the second bearing by tightening the inner ring of the two bearings. 4. The feed drive device according to claim 1, wherein the drive motor is mounted on the first bearing housing by coupling the output shaft to a ball screw with a coupling.