JPH10122248A - Bearing support structure of rotary shaft and motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain a creep and support the rotation of a rotary shaft smoothly by push-pressing so as to oppose to the maximum force for moving an outer race in a radius direction by the rotation of the rotary shaft from the radius direction outside while allowing the axial direction movement of the outer race and pressing the outer race against a bearing support hole. SOLUTION: In a spring holding hole 22, a compression coil spring 23 is interposed between a corresponding outer race 14a and a groove bottom 20 as push-press means and the spring force of the compression coil spring 23 is exerted from a radius direction outside toward the center of a bearing for the outer periphery surface of the outer race 14a. When a rotary shaft 25 is rotated, a spring force is set to a larger force than the maximum force generated in the lateral direction of the outer race 14a and the play of the outer race 14a is prevented by opposing, even if the maximum force generates in the radius direction of the outer race 14a. The outer race 14a is pushed against a connection point of a hollow part 11b and a cylindrical hole part. Thereby, the outer race 14a restrains a creep rotated at very slow speed in a reverse direction and the rotary shaft 25 can be rotated smoothly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing support structure in which an inner ring rotary type bearing is moved in an axial direction following thermal expansion of a rotating shaft, and more particularly to a method for suppressing the occurrence of outer ring creep and a bearing. The technology relates to the technology of suppressing vibration.

[0002]

2. Description of the Related Art An inner ring such as an angular ball bearing or a deep groove ball bearing is integrally fitted into both ends of a rotating shaft, and an outer ring thereof is used as a bearing housing for a bearing at one end of the rotating shaft. And the bearing at the other end of the rotating shaft,
A preload spring is fitted in the bearing housing with a loose fit (gap fit) to allow axial movement, and a preload spring is provided that presses the outer ring of the axially movable bearing from the axial direction. The preload spring is made of an elastic material such as rubber. Envelopment and friction between the outer ring end surface are increased, and the outer ring is rotated around the inner circumference of the bearing support hole with the rotation of the rotating shaft due to the minute gap between the bearing support hole of the bearing housing and the outer ring loosely fitted in the bearing support hole. There is one that suppresses the so-called creep phenomenon in which the roller rolls slowly in the anti-rotation direction (Japanese Patent Laid-Open No. 5-64390). When creep occurs, differential slippage occurs between the outer race and the bearing support hole, causing not only wear at the joint surface of the outer ring and the bearing surface, but also a problem of damaging the bearing and the bearing housing by heating with frictional heat. . Also, in this prior art document, in order to achieve the same purpose, the loosely fitted outer ring and the axially inner bearing cover are integrally connected, and the bearing cover and the bearing housing are moved by a predetermined amount in the axial direction. It is possible, however, to disclose a structure in which the members are integrally connected by a tightening screw in the rotational direction.

Further, as a technology somewhat similar to the present application,
Japanese Patent Application Laid-Open No. 7-123629 is available. This technology is
The present invention relates to a bearing structure for a small DC motor, in which a motor shaft is supported by a first sintered oil-impregnated bearing, and the sintered oil-impregnated bearing is press-fitted into a bearing support hole of a frame. On the output shaft side of the oil-impregnated bearing, a second sintered oil-impregnated bearing having a smaller diameter than the bearing support hole is inserted, and an elastic material is interposed between the outer peripheral surface of the second bearing and the bearing support hole,
A lateral pressure (a force in a direction orthogonal to the axial direction) is applied to the motor shaft via the second bearing, thereby killing a small rotating gap between the first sintered oil-impregnated bearing and the motor shaft, and the output-side shaft is Prevents swinging motion (vibration).

[0004]

Although creep can be suppressed in the above method, the loosely-fitted bearing outer ring still has a small gap for axial movement between the bearing outer ring and the bearing support hole. The clearance causes the entire bearing to swing and oscillate, causing vibration and noise during high-speed rotation. Further, when the outer ring vibrates against the inner surface of the bearing support hole, abrasion occurs between the outer ring and the inner surface of the support hole, which further promotes the vibration and shortens the life of the bearing.
In addition, the influence of the gap between the first oil-impregnated bearing and the motor shaft rotatably supported in the shaft support hole is reduced by using the second oil-impregnated bearing arranged side by side axially outside the first oil-impregnated bearing. Although the shaft is prevented from running, the shaft can be prevented from swaying. However, in this structure, two oil-impregnated bearings are arranged side by side, so that a space for mounting the shaft in the axial direction becomes large as the bearing structure. Have a problem.
In addition, in this case, the motor shaft is pressed into each of the shaft support holes of the second oil-impregnated bearing and the first oil-impregnated bearing, so that the resistance due to the pressing force acts on the motor shaft, and the motor shaft is smoothly moved. Rotation may be hindered. An object of the present application is to reduce the creep, suppress the vibration caused by the gap between the bearing outer ring and the bearing support hole, reduce the vibration in the axial direction, increase the life of the bearing, and rotate the rotating shaft smoothly. An object of the present invention is to provide a shaft bearing support structure. Another object of the present invention is to provide an electric motor having such a bearing support structure, particularly an electric motor for rotating a machining spindle of a machine tool.

[0005]

SUMMARY OF THE INVENTION The present invention allows an outer ring of an inner ring rotary type bearing which is axially movably fitted into a bearing support hole and is preloaded from the axial direction to allow the outer ring to move in the axial direction. Then, the outer ring is pressed against the bearing support hole from the outside in the radial direction by pressing the outer ring against the maximum force for moving the outer ring in the radial direction by the rotation of the rotating shaft. With the resistance by pressing the outer ring against the bearing support hole,
The rotation of the outer ring (creep phenomenon) is suppressed, and the generation of vibration due to the effect of the gap between the outer ring and the bearing support hole is suppressed.
The bearing life is extended, and the rotating shaft is smoothly supported by the inner ring against the outer ring pressed in such a manner.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the present invention, an outer ring of an inner ring rotary type bearing in which a rotating shaft is integrally fitted to an inner ring thereof is fitted in a bearing support hole so as to be movable in the axial direction, and the outer ring is axially moved by a preload spring. In the bearing support structure for a rotating shaft formed by pressing, a pressing means for pressing the bearing outer ring from the outside in the radial direction while allowing the axial movement of the bearing outer ring is provided.

The outer ring is fitted in a gap in the bearing support hole so as to be movable in the axial direction. The bearing support hole is composed of a cylindrical hole portion having a constant radius and a concave portion recessed outward in the radial direction, and a pressing means is provided so that the bearing outer ring is pressed at a connection point between the cylindrical hole portion and the concave portion. is there. On the diametrically opposite side of the recess, a pressing means is provided.

The bearing support hole may be a cylindrical hole having a constant radius, and a pressing means may be provided so that the bearing outer ring is pressed at one point on the circumference of the cylindrical hole.

The pressing means is, for example, an elastic material interposed between a bearing housing having a bearing support hole and a bearing outer ring. The elastic material is, for example, a spring material,
More specifically, it is a cylindrical coil spring. In the case of a cylindrical coil spring, since it also bends in a direction perpendicular to the compression direction, the axial movement of the outer ring can be allowed.

[0010] The above-described structure is an electric motor in which both ends of the rotating shaft are integrally fitted to the inner ring of the inner ring rotating type bearing, and the outer ring of the bearing at the tip end of the rotating shaft is axially fixed to the bearing housing. , Applied to the support of the outer ring of the bearing on the rear end side of the rotating shaft. Further, in the above configuration, the rotating shaft is a machining spindle of a machine tool, and a motor structure is interposed between bearings before and after supporting the machining spindle, and a bearing of a tool mounting portion side at a tip of the machining spindle is provided. The present invention is also applied to the support of the outer ring of a bearing on the rear side of a rotating shaft in a spindle device with a built-in motor in which the outer ring is fixed in the axial direction to a bearing housing.

According to the above, the outer ring of the bearing is pressed in the radial direction by the pressing means, whereby the outer ring is pressed against the bearing support hole. Due to the pressing resistance, the outer ring rotates slightly in the opposite direction due to the rotation of the inner ring of the bearing. Creep can be suppressed, and abrasion of the outer ring outer peripheral surface and the inner surface of the support hole due to creep and damage due to frictional heat can be prevented. In addition, since the bearing outer ring is pressed against the support hole, vibration due to the effect of the gap in the bearing support hole can be suppressed, and wear due to the vibration can be suppressed. Can be extended. Even in the case of suppressing the vibration of the bearing outer ring, the structure that pushes the bearing outer ring from the outside in the radial direction does not increase the axial space, and the inner ring that rotates against the pressed outer ring rotates. Since the rotary shaft is fitted integrally with the shaft, the rotary shaft can be smoothly rotated regardless of the pressing force. When the rotating shaft thermally expands, the pressing means allows the outer ring to move in the axial direction, so that the basic operation of being able to escape the extension due to the heat is not impaired.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an electric motor A (for example, an electric motor for rotating a main shaft of a machine tool at a high speed) which generates relatively high heat and greatly expands and contracts due to the heat of a rotating shaft will be described. As shown in FIG. 1, the casing 1 is configured by integrally connecting a front bearing bracket 3 and a rear bearing bracket 4 to the front and rear of a casing body 2. A bearing housing 6 having a bearing support hole 5 is provided at the center of the front bearing bracket 3. In the bearing support hole 5, a pair of angular ball bearings 7, 7 exemplified as inner ring rotary type bearings are sandwiched between inner and outer spacers 8, 9 similar to a rear bearing described later. Are sandwiched by the bearing cap 10 from the outside in the axial direction to the bottom wall 6a of the bearing housing 6, and are fixed in the axial direction.

As shown in FIG. 2, a bearing housing 12 having a bearing support hole 11 penetrating back and forth is provided at the center of the rear bearing bracket 4. Bearing housing 1
A bearing cover 13 is integrally connected to the inner end of 2.
Of course, it may be formed integrally with the bearing housing 12. The bearing support hole 11 has a constant radius slightly larger than the diameter of the outer ring 14a of the pair of angular ball bearings 14, 14 exemplified as an inner ring rotation type bearing (so as to allow a clearance fit between the outer ring 14a). It comprises a cylindrical hole portion 11a and a concave portion 11b cut in an arc shape so as to concave a part of the cylindrical hole portion 11a to the outside. The bearing support hole 11 has a pair of angular ball bearings 14, 1.
4 are spacers 8, 9 between the inner ring 14b and the outer ring 14a, respectively.
The outer races 14a are clearance-fitted in a state of sandwiching them, and are movable in the axial direction. Bearing housing 1
2 is closed by a bearing cover 15, and the bearing cover 15 and an outer ring 14 of an angular ball bearing 14 on the rear side in the axial direction are provided.
A metal disc spring-shaped preload spring 16 having an annular corrugated cross section is interposed between the end faces of FIG. 3A by being compressed in an appropriate amount in the axial direction to apply a preload to the rolling ball 14c via the outer ring, thereby improving rotation accuracy. ing.

As shown in FIG. 3, an angular contact ball bearing 1
The bearing support hole 11 of the bearing housing 12 is provided on the opposite side of the recess 11b in the diametric direction (just opposite the center of the circumferential length of the recess 11b) across the recesses 4 and 14.
A groove 20 having a rectangular cross section is formed over the entire length. As shown in FIG. 4, a holding member 21 having a thickness that does not protrude from the groove 20 into the bearing support hole 11 is sandwiched between the bearing covers 13 and 15, and is fitted into the groove 20 with its axial position determined. Have been. The holding member 21 is provided with a spring holding hole 22 at a position opposing the outer ring 14a of the pair of angular ball bearings 14, 14, respectively. In each spring holding hole 22,
An elastic material exemplified as the pressing means, here a compression coil spring 23, is interposed between the corresponding outer ring 14a and the groove bottom 20a, and applies a spring force of the compression coil spring 23 in a radial direction with respect to the outer peripheral surface of the outer ring 14a. It acts from the outside toward the center of the bearing. This spring force is set to a force larger than the maximum force generated in the lateral direction (radial direction) of the outer ring 14a when the rotating shaft 25 rotates, and even if the maximum force is generated in the radial direction of the outer ring 14a, In contrast to this, the outer ring 14a is prevented from rattling due to the minute gap between the outer ring 14a and the support hole 11. As a result, the outer ring 14a is pressed against the two connection points (also referred to as receiving portions) 11d between the concave portion 11b and the cylindrical hole portion 11a.

The inner ring 7b of the angular ball bearings 7, 7 on the axial front end, and the angular ball bearings 14, 1 on the axial rear end side.
The four inner rings 14b are integrally fitted with both end portions of the rotating shaft 25, respectively. The inner races 7b, 14b are connected to the stepped portions 25a, 25 of the rotary shaft 25 for both the front (output side) and rear bearings.
5b are tightened by bearing nuts 26 and 27. A rotor 28 is integrally provided on the outer periphery of a central portion of the rotating shaft 25, and a stator 29 is provided inside the casing body 1.
Is provided.

In the electric motor having the above structure, a rotating magnetic field is generated by the stator 29, thereby rotating the rotor 28, and the rotating shaft 25 is attached to the outer rings 7a, 14a by the inner rings 7b, 14b of the front and rear angular ball bearings 7, 14. Rotate against. The bearings 14 on the rear side in the axial direction are outer rings 14a, 1
4a is tightly fitted in the bearing support hole 11, so there is a small gap between the support hole 4a and the support hole 11. However, the compression coil spring 23 presses against the two receiving portions 11d of the bearing support hole 11. Therefore, the outer ring 1
4a is prevented from slewing and vibration, and creep in which the outer ring 14a rotates in the opposite direction at a very low speed due to the inner ring 14b rotating at high speed is suppressed. Therefore, wear of the joint surface between the bearing outer ring 14a and the support hole 11 due to creep is suppressed, and damage to those members due to generation of frictional heat is prevented.

Further, since the outer ring 14a is pressed and fixed at a part (two places) of the bearing support hole 11, the gap between the outer ring 14a and the support hole 11 causes the bearing outer ring 14a to vibrate. The support hole 11 due to vibration
Is also suppressed. Thereby, the life of the bearing 14 and the bearing housing 12 is extended,
Easy maintenance. Even in the case where the influence of the gap between the bearing outer ring 14a and the support hole 11 is eliminated as described above, since the pressing force is not directly applied to the rotation shaft 25, the rotation shaft 25 The inner ring 14b that rotates inside the pressed outer ring 14a rotates smoothly.

Further, heat is generated by rotation of the rotor 28 and the like, and when the heat causes the rotary shaft 25 to thermally expand, the axially front-side angular ball bearings 7, 7 have their outer rings 7a fixed in the axial direction. Therefore, the bearings 7 cannot move forward in the axial direction due to the extension of the rotary shaft 25. Of course, the shaft portion (output side portion) that protrudes forward from the bearings 7, 7 is affected by heat and causes some thermal expansion.
It is extremely small because the length of the shaft portion protruding forward is short. Therefore, when connecting the output side portion of the rotating shaft 25 and, for example, the main shaft 100 of a machine tool with the joint 101, the joint 101 is provided with a mechanism for absorbing a large axial length change due to the heat of the rotating shaft 25. There is no need to prepare. Since the bearings 14 on the rear side in the axial direction are clearance-fitted in the bearing support holes 11, the thermal expansion of the rotary shaft 25 causes
An attempt is made to move rearward through the inner ring 14b. Outer ring 14
When a moves backward, the outer ring 14a is pressed from the outside in the radial direction by the compression coil spring 23 in the present application, but the compression coil spring 23 can also bend in a direction perpendicular to the pressing direction. The distal end portion of the compression coil spring 23 that is in contact with the outer ring 14a bends slightly backward due to the rearward movement of the outer ring 14a, or causes a slip between the distal end of the compression coil spring 23 and the outer ring 14a,
The rearward movement of the outer ring 14a is smoothly performed, and the thermal expansion of the rotating shaft 25 is allowed, so that the internal stress of the rotating shaft 25 is prevented from increasing.

FIG. 5 shows another example of the pressing means. Spring holding hole 2 of holding member 21 holding compression coil spring 23
2 is a bottomed hole as shown in FIG.
A pressing member 30 having a U-shaped cross section is movably fitted in the radial direction of the bearing 14, and a compression coil spring 23 is interposed between the pressing member 30 and the bottom of the bottomed hole. Due to the force, the distal end surface of the pressing member 30 moves to the bearing outer ring 14a.
Is pressed inward in the radial direction. Outer ring 1 of pressing member 30
The pressing surface 30a with the outer ring 4a is an arc surface which coincides with a part of the arc surface in the circumferential direction of the outer ring 14a. Spring holding hole 2
2 has a bottomed hole, and the spring member is interposed between the bottom and the outer ring 14a.
a regardless of whether or not it is interposed between
Is pressed against the bottom 20 a of the groove 20, so that it is possible to prevent the holding member 21 from rattling against the bearing 14 in the radial direction.

FIG. 6 shows another example of the arrangement of the pressing means. The inner ring rotating type bearing 14 is connected to two compression coil springs 23.
Is pressed by one point (pressing point) 11D on the circumference of the bearing support hole 11A formed of a cylindrical hole having a constant radius. Two compression coil springs 23
, And the angular interval in the circumferential direction between the pressing point 11D and the pressing point 11D are set to 120 degrees. In FIG. 7, as in FIG. 6, two compression coil springs 23 are used as a pressing means for one bearing 14, and a support hole 11B is formed with a constant radius. It is recessed radially outward from the portion 11e, and has an appropriate circumferential deployment angle (for example, 90 degrees to
The compression coil spring 23 presses from the opposite side of the receiving portion 11g between the concave portion 11f and the cylindrical hole portion 11e.

FIG. 8 shows still another example. Bearing 14
A reinforcing outer ring 14d is tightly fitted to the outer ring 14a,
Both outer rings 14a and 14d are completely integrated. The receiving portion 1 is provided between the bearing support hole 11E and the reinforcing outer ring 14d.
A plurality of small balls 14e are interposed at positions corresponding to 1d, respectively. Numeral 40 denotes a spacing member for keeping the position of the small ball 14e in the circumferential direction from moving, and the whole of the space holding member 21 is prevented from rotating in the circumferential direction by the holding member 21. According to this configuration, the reinforcing outer ring 14d is pressed against the bearing support hole 11E by the spring force of the compression coil spring 23 via the small ball 14e arranged on the receiving portion 14d. Since the reinforcing outer ring 14d is integrally fitted to the outer ring 14a of the bearing 14 and the outer ring 14a is reinforced, the pressing force of the compression coil spring 23 is set to be large enough to cause deformation of the bearing outer ring 14a. If necessary, that is, the rotation of the rotating shaft 25
When the spring force for opposing the maximum radial force generated in a must be large enough to cause deformation of the bearing outer ring 14a, the reinforcing outer ring 14d is
In order to prevent the deformation of the reinforcing outer ring 14d (that is, the outer ring 14a), the compression coil spring 23 having such a large spring force can be used without any problem.
Even if the pressing force is extremely large, when thermal expansion occurs in the rotating shaft 25, the small ball 14
Since e rotates and guides the reinforcing outer ring 14d in the axial direction, the reinforcing outer ring 14d (outer ring 14a) can smoothly move in the axial direction. In the above-described example, the compression coil spring has been described as the spring material. However, other types of springs, for example, a flat spring or a leaf spring, may be used. It may be an elastic body capable of obtaining a pressing force by the following method. Further, in the above-described embodiment, an example has been described in which the outer ring is supported at three points (two receiving parts and one pressing part) or four points (two receiving parts and two pressing parts). The outer ring may be increased further, or the outer ring may be pressed at one place to press the outer ring against one of the bearing support holes. Even in this case, only the outer ring can be prevented from slewing and rotating.

[0022]

As described above, according to the present invention, the outer ring of the bearing is pushed from the outside in the radial direction, and a part of the outer ring is directly
Alternatively, since the bearing is indirectly pressed against the bearing support hole, creep of the outer ring can be suppressed by the pressing resistance, and wear of the outer ring outer peripheral surface and the inner surface of the support hole due to creep and damage due to frictional heat can be prevented. In addition, since the bearing outer ring is pressed against the support hole, the vibration of the bearing due to the effect of the gap in the bearing support hole can be suppressed, and the wear due to the vibration can also be suppressed. In addition to extending the life of the bearing, it is also possible to suppress the sliding motion of the bearing. Even in the case of suppressing the vibration of the bearing outer ring, the structure that pushes the bearing outer ring from the outside in the radial direction does not increase the axial space, and the inner ring that rotates against the pressed outer ring rotates. Since the rotary shaft is fitted integrally with the shaft, the rotary shaft can be smoothly rotated regardless of the pressing force. Then, when there is thermal expansion of the rotating shaft, the bearing can be moved in the axial direction to escape the extension of the rotating shaft, and an increase in the internal stress of the rotating shaft can be suppressed.

Further, in the motor adopting the bearing structure of the present invention, noise is reduced by suppressing vibration, maintenance is facilitated by extending the life of the bearing, and the size in the longitudinal direction is not increased. Moreover, since the bearing structure of the present invention is adopted on the side opposite to the output side of the rotating shaft of the electric motor, the extension of the shaft due to the thermal expansion of the rotating shaft at the output side connected to the main shaft of the machine tool is extremely small. Therefore, there is no need for a mechanism for absorbing large axial movement due to thermal expansion in the joint means with the main shaft.

[Brief description of the drawings]

FIG. 1 is a sectional view of a motor employing the present invention.

FIG. 2 is an enlarged sectional view of a main part of the present application.

FIG. 3 is a sectional view taken along line III-III of FIG. 2;

FIG. 4 is a plan view of a spring holding member.

FIG. 5 is another example of the pressing means.

FIG. 6 is another example.

FIG. 7 is still another example.

FIG. 8 is still another example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Bearing support hole 11a Cylindrical hole part 11b Recess part 11d Connection point (receiving part) 14 Bearing 14a Outer ring 14b Inner ring 16 Preload spring 21 Holding member 23 Compression coil spring 25 Rotary shaft A Motor

Claims (7)

[Claims] A rotating shaft formed by axially moving an outer ring of an inner ring rotating type bearing having a rotating shaft integrally fitted to an inner ring thereof in a bearing support hole, and pressing the outer ring axially by a preload spring. The bearing support structure of (1), further comprising pressing means for pressing the bearing outer ring from the outside in the radial direction while allowing the axial movement of the bearing outer ring. 2. The bearing support structure for a rotary shaft according to claim 1, wherein the outer ring is fitted into the bearing support hole with a clearance. 3. The bearing support hole includes a cylindrical hole portion having a constant radius and a concave portion recessed radially outward, and a bearing outer ring is pressed at a connection point between the cylindrical hole portion and the concave portion. The bearing support structure for a rotary shaft according to claim 1, further comprising a pressing unit. 4. A bearing support structure for a rotary shaft according to claim 3, wherein a pressing means is provided on the opposite side of the concave portion in the diameter direction. 5. The bearing support hole according to claim 1, wherein the bearing support hole is a cylindrical hole having a constant radius, and pressing means is provided so that the bearing outer ring is pressed at a point on the circumference of the cylindrical hole. Rotary shaft bearing support structure. 6. The bearing according to claim 1, wherein the pressing means is an elastic material interposed between the bearing housing having the bearing support hole and the bearing outer ring. Rotary shaft bearing support structure. 7. Both ends of the rotating shaft are integrally fitted to the inner ring of the inner ring rotating type bearing, respectively, and the outer ring of the bearing on the leading end side of the rotating shaft is axially fixed to the bearing housing, and the rear end of the rotating shaft is provided. An electric motor, wherein the outer ring of the bearing on the side is supported by the bearing support structure according to any one of claims 1 to 6.