JP2006077925A - Bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bearing device capable of reducing the rise of pre-load during high-speed rotation with a simple structure to increase a speed and to reduce power generation, and further controlling thermal displacement. <P>SOLUTION: This bearing device 10 comprises front-side bearings 12, 13 having an inner ring 14 externally fitted to a front end side of a rotating shaft 11, and an outer ring 15 internally fitted to a housing 16, rear-side bearings 17, 18 having an inner ring 19 externally fitted to a rear end side of the rotating shaft 11, and an outer ring 20 internally fitted to the housing 16, combined with the front-side bearings 12, 13 back to back to receive pre-load at a fixed position, and rotatably supporting the rotating shaft 11 in cooperation with the front-side bearings 12, 13, and an outer ring spacer 21 incorporated between the front-side bearings 12, 13 and the rear-side bearings 17, 18. One end side of both ends of the outer ring 20 of the rear-side bearing 18 is axially fixed to the housing, and the other end side is opened. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a bearing device that rotates at high speed, such as a machine tool.

  As an example of a conventional bearing device, a bearing device using a spacer provided with a first outer ring spacer, a second outer ring spacer, and an intermediate outer ring spacer is known (for example, a patent). Reference 1).

  In the bearing device disclosed in Patent Document 1, the cylindrical portion of the first outer ring spacer is in contact with the outer ring of one bearing, and the cylindrical portion of the second outer ring spacer is in contact with the outer ring of the other bearing. The intermediate outer ring spacer is disposed between the cylindrical portion of the first outer ring spacer and the cylindrical portion of the second outer ring spacer. The first outer ring spacer and the second outer ring spacer have a thermal expansion coefficient smaller than that of the rotating shaft, and the intermediate outer ring spacer has a thermal expansion coefficient larger than that of the rotating shaft. .

  As another example of a conventional bearing device, a bearing device including a hydraulic control device is known (see, for example, Patent Document 2).

In the bearing device disclosed in Patent Document 2, when the rotational speed (rotational speed) of the rotary shaft reaches the set rotational speed (rotational speed), the hydraulic control device is operated to pivot the bearing housing and the spacer. The amount of movement of the bearing housing is adjusted by the adjusting member and the spacer.
Japanese Patent Laid-Open No. 08-014252 (page 3-4, FIG. 1) Japanese Patent Laid-Open No. 02-279203 (page 3-4, FIG. 1)

  Incidentally, as shown in FIG. 4, in the bearing device 100 having the same structure as that of Patent Document 1, the rotating shaft 101 and the inner ring 104 are fitted on the front end side of the rotating shaft 101, and the outer ring 105 is fitted in the housing 106. The fitted front side bearings 102 and 103, the inner ring 109 are fitted on the rear end side of the rotating shaft 101, the outer ring 110 is fitted on the housing 106, the rear side bearings 107 and 108, the front side bearing 103 and the rear An outer ring spacer 111 and an inner ring spacer 112 arranged between the side bearings 107 are provided. The front-side bearing 102 is fixed in the axial direction by an outer ring pressing member 113 whose left end surface is fixed to the housing 106, and the rear-side bearing 108 is fixed in the axial direction by the outer ring pressing portion 114 of the housing 106. ing. The front-side bearings 102 and 103 and the rear-side bearings 107 and 108 are preloaded at a fixed position in a combination of the back surfaces. In this fixed position preload, for example, if the outer ring spacer width is deformed during operation, the bearing preload can be prevented from increasing and high-speed rotation is possible.

  However, in such a bearing device 100, even if the linear expansion coefficient of the outer ring spacer 111 is reduced, the thermal expansion in the outer ring spacer 111 is small when the ambient temperature rises. Since the thermal expansion is small, the force for pressing the front bearings 102 and 103 and the rear bearings 107 and 108 by the outer ring pressing member 114 is reduced. As a result, the low thermal expansion characteristic of the outer ring spacer 111 is offset by a decrease in elastic deformation in the outer ring spacer 111 due to a decrease in the pressing force. , 110 may cause rattling, and it is difficult to reduce the preload during operation.

  And when such a bearing apparatus 100 is used as a main spindle apparatus of a machine tool, the left side of the rotary shaft 101 corresponding to the main spindle in the figure is the tool side. When the temperature of the rotating shaft 101 rises, the rotating shaft 101 is based on the length L from the left end portion of the rotating shaft 101 to the intermediate position H between the front bearings 102 and 103 and the rear bearings 107 and 108. Is extended in the left direction, the thermal displacement of the rotating shaft 101 is increased, which may cause a decrease in the accuracy of the tool.

Further, in Patent Document 1 described above, when the high-speed rotation is performed with the fixed position preload, it is improved that the preload is increased and hinders the speed increase. However, the end surfaces of the outer rings are fixed by pressing from the housing side. For this reason, when the ambient temperature rises, the pressing force fluctuates, and not only can the expansion of the spacer be suppressed as intended, but also the outer ring may be rattled.
And in the said patent document 2, since it is necessary to arrange | position a hydraulic control apparatus outside the bearing apparatus, while it becomes a complicated structure, there exists a possibility that the whole apparatus may enlarge.

  The present invention has been made in view of the above circumstances, and its object is to reduce the increase in preload during high-speed rotation with a simple structure, to achieve high speed and low heat generation, and to suppress thermal displacement. An object of the present invention is to provide a bearing device that can be used.

  1) The bearing device of the present invention includes a front shaft bearing in which a rotating shaft, an inner ring is fitted on the front end side of the rotating shaft, and an outer ring is fitted in a housing, and an inner ring is mounted on the rear end side of the rotating shaft. A rear-side bearing that is fitted into the housing, is pre-stressed in a fixed position by a combination of the front-side bearing and the rear surface, and supports the rotary shaft rotatably with the front-side bearing; An outer ring spacer assembled between a front side bearing and the rear side bearing, wherein one end side of the outer ring of the front side bearing is fixed in an axial direction with respect to the housing, One end side of the outer ring of the rear side bearing is open.

  According to the bearing device having the above-described configuration, the outer ring of the rear side bearing is freed in the axial direction at one end side, so that the axial load applied to the outer ring spacer is limited only to the preload generated in the rear side bearing. be able to. Thereby, the deformation amount of the outer ring spacer when the ambient temperature fluctuates is made equal to the thermal expansion amount, the thermal expansion is controlled by the outer ring spacer, and the increase in preload due to the temperature rise can be reduced. Accordingly, it is possible to extend the bearing life and increase the rotation speed.

  2) The bearing device of the present invention is characterized in that, in the bearing device described in 1), the outer ring spacer is formed of a material having a linear expansion coefficient smaller than that of the rotating shaft.

  According to the bearing device configured as described above, if the outer ring spacer is formed from a low expansion material such as novinite cast iron, invar, ceramic, etc., compared with carbon steel made from other rotating shafts, housings, etc. Thus, it has a small linear expansion coefficient. As a result, when the temperature around the bearing rises due to high-speed rotation, the amount of thermal expansion of the outer ring spacer is small, so that the preload can be reduced.

  According to the bearing device of the present invention, it is possible to reduce a rise in preload during high-speed rotation with a simple structure, to achieve high speed and low heat generation, and to suppress thermal displacement.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing an embodiment of a bearing device according to the present invention, and FIG. 2 is a cross-sectional view showing a modification of the bearing device shown in FIG.

  As shown in FIG. 1, a bearing device 10 according to an embodiment of the present invention mainly includes a rotating shaft 11 and an inner ring 14 fitted on the front end side of the rotating shaft 11, and an outer ring 15 fitted on a housing 16. The front bearings 12 and 13 and the inner ring 19 are fitted on the rear end side of the rotary shaft 11, the outer ring 20 is fitted on the housing 16, and the front side bearings 12 and 13 and the rear combination are preloaded at a fixed position. The rear bearings 17 and 18 that support the rotary shaft 11 in cooperation with the side bearings 12 and 13 and the outer ring assembled between the front bearings 12 and 13 and the rear bearings 17 and 18. It comprises a seat 21 and an inner ring spacer 22.

  The rotary shaft 11 includes a draw bar (not shown), and the draw bar is moved forward and backward against a return spring (not shown), thereby clamping or cutting a tool (not shown) on the left end side in the drawing. Unclamp.

  As the front bearings 12 and 13, for example, angular contact ball bearings made of ceramic balls are used in a parallel combination, and the inner rings 14 and 14 with the inner ring spacer 23 assembled therebetween are fitted on the front end side of the rotary shaft 11, so Outer rings 15 and 15 with a seat 24 assembled therebetween are fitted in a large diameter portion 25 formed on the front side of the housing 16.

  One front side bearing 12 disposed on the left side of the front side bearings 12 and 13 has an inner ring fixing member 27 in which the left end surface of the inner ring 14 is screwed and fixed to the rotary shaft 11 via an inner ring spacer 26. The left end surface of the outer ring 14 is fixed in the bearing direction by the outer ring pressing member 28.

  In the other front side bearing 13 disposed on the right side of the front side bearings 12 and 13, the right end surface of the inner ring 14 is in contact with the inner ring spacer 22, and the right end surface of the outer ring 14 is larger than the housing 16. It is fixed in the axial direction by a stepped portion 29 formed at the end of the diameter portion 25.

  The rear side bearings 17 and 18 use, for example, ceramic ball angular ball bearings in a parallel combination in the same manner as the front side bearings 12 and 13, and the inner rings 19 and 19 with the inner ring spacer 30 assembled therebetween. The outer rings 20 and 20 that are externally fitted to the rear end side of the rotary shaft 11 and the outer ring spacer 31 are assembled therebetween have a loose amount of about 5 to 30 μm in the small diameter portion 32 formed on the rear stage side of the housing 16. It is fitted with a slight clearance fit and is not fixed to the small diameter portion 32 in the axial direction.

  One rear bearing 17 disposed on the left side of the rear bearings 17, 18 has the left end surface of the inner ring 19 in contact with the inner ring spacer 22, and the left end surface of the outer ring 20 is the outer ring spacer 21. Abut.

  The other rear side bearing 18 disposed on the right side of the rear side bearings 17 and 18 has the right end surface of the inner ring 19 fixed in the axial direction by the inner ring pressing member 33 and the right end surface of the outer ring 20 opened. Has been.

  The outer diameters of the front side bearings 12 and 13 are larger than the outer diameters of the rear side bearings 17 and 18. As a result, the assembly of the front bearings 12 and 13 can be performed after the assembly of the rear bearings 17 and 18 is completed.

  The outer ring spacer 21 is, for example, novinite cast iron (excellent castability, can be manufactured in a complicated shape, and can also be manufactured as a thin-walled cast, and has excellent corrosion resistance, heat resistance, low temperature brittleness, etc. Low-expansion materials such as Invar, Ceramic, etc., in the form of graphite graphite (CF-5) and spherical graphite structure (C-5) with excellent vibration and breathing function in the low frequency range It is molded as The outer ring spacer 21 has a smaller linear expansion coefficient than carbon steel used as the material of the rotary shaft 11, the other spacers 23, 24, 30, 31 and the housing 16. Thereby, when the temperature around the bearing rises due to high-speed rotation, the thermal expansion coefficient of the outer ring spacer is small, so that the preload can be reduced.

  In such a bearing device 10, since the right end surface of the outer ring 20 in the rear side bearing 18 is opened, the axial load applied to the outer ring spacer 21 is limited only to the preload load generated in the rear side bearings 17 and 18. can do. Thereby, the deformation amount of the outer ring spacer 21 when the ambient temperature fluctuates is made equal to the thermal expansion amount, the thermal expansion is controlled by the outer ring spacer 21, and the increase in the preload due to the temperature rise can be reduced. it can.

  Moreover, in this invention, the thermal elongation (thermal displacement) of the axis | shaft on a tool side can be restrained small. Since one end of the rear side bearing 18 is opened and the outer ring has a gap with respect to the housing, the outer ring 20 of the rear side bearing 18 slides to the left when the shaft extends, and is caused by thermal expansion on the tool side. Elongation can be suppressed. As a result, the reference position for the thermal expansion of the rotary shaft 11 when the bearing and its surrounding temperature rise becomes the intermediate position H1 between the front bearings 12 and 13, and from the left end of the rotary shaft 11 to the intermediate position H1. Up to the length Ln. Compared with the conventional one, the reference position is displaced to the tool side end of the rotary shaft 11, and the length L to the conventional intermediate position H> the length to the intermediate position H1 of the bearing device 10. Since L is L: Ln≈6: 10, even under the same temperature rise, the thermal displacement can be made much smaller than the conventional one, and the thermal displacement can be reduced to about 6/10 of the conventional one. Become.

Next, a modified example of the bearing device 10 will be described with reference to FIG.
As shown in FIG. 2, in this modification, the large diameter portion 25 of the housing 16 is shortened, the small diameter portion 32 is lengthened, and the front large bearing 25 is connected to the shortened large diameter portion 25. One front side bearing 12 on the left side in the figure is assembled through an adapter collar 34 disposed outside the outer ring 15. The outer ring 15 of the front bearing 12 has a left end surface fixed in the bearing direction by an outer ring pressing member 28 and a right end surface in contact with a thick outer ring spacer 35. The adapter collar 34 restrains the outer ring 15 in the radial direction.

  In this modification, the outer diameters of the front bearings 12 and 13 and the rear bearings 17 and 18 can be made the same. As a result, the use of the single standard bearings 12, 13, 17, and 18 eliminates the need to use a plurality of standard bearings, thereby preventing erroneous assembly and improving productivity. it can.

  According to the bearing device 10 described above, the outer ring 20 of the rear bearing 18 is freed in the axial direction on the right end surface, so that an axial load applied to the outer ring spacer 21 is generated in the rear bearings 17 and 18. Only preloading load can be made. Thereby, the deformation amount of the outer ring spacer 21 when the ambient temperature fluctuates is made equal to the thermal expansion amount, the thermal expansion is controlled by the outer ring spacer 21, and the increase of the preload due to the temperature rise can be reduced. it can. As a result, the bearing life can be extended and high-speed rotation can be achieved.

  Further, according to the bearing device 10, the outer ring spacer 21 is formed from a low expansion material such as novinite cast iron, invar, ceramic, etc., for example, so that the rotary shaft 11, the housing 16, the spacer 23, Compared with the carbon steel which 24, 30, 31 etc. use as a raw material, it has a small linear expansion coefficient. Thereby, when the temperature around the bearing rises due to high-speed rotation, the amount of thermal expansion of the outer ring spacer 21 is small, so the preload can be reduced.

Next, examples of the bearing device according to the present invention will be described.
In order to confirm the effect of the present invention, the calculated life ratio was calculated by applying the following conditions.
(Calculation condition)
Rotational speed: 18000min ^-1
Bearing: inner diameter φ70, outer diameter φ110 Ceramic ball angular contact ball bearings Built-in preload 200N
Bearing temperature rise: Outer ring 25 ° C, Inner ring 35 ° C
Outer ring spacer: length 70mm, temperature rise 20 ℃
Housing: Temperature rise 15 ° C, outer diameter φ150, carbon steel S45C
Rotating shaft and other spacer materials: Carbon steel S45C

As shown in FIG. 3, (1) corresponding to the conventional one has a linear expansion coefficient of the outer ring spacer of 11.5 × 10 ⁻⁶ / ° C. and a lid presser amount of 10 μm. Further, in (2) corresponding to the conventional one, the linear expansion coefficient of the outer ring spacer is 2.8 × 10 ⁻⁶ / ° C., and the lid pressing amount is 20 μm. In (3) corresponding to the present invention, the linear expansion coefficient of the outer ring spacer is 2.8 × 10 ⁻⁶ / ° C., and the lid pressing amount is 10 μm.

  As is apparent from the calculation results, (1) is a conventional example, and the preload during operation is 2700N. The calculated life ratio at this time was 1.0. In (2), when the preload during operation is 2400 N, the calculated life ratio becomes 1.4, and the life of the bearing life is small. On the other hand, (3) of the present invention reduced the preload during operation to 2000 N, the calculated life ratio was 2.0, and a life ratio twice that of (1) was obtained. . Thus, according to the present invention, it is understood that the preload during operation can be reduced and the bearing life can be extended as compared with the conventional one.

  The bearing device according to the present invention is not limited to the embodiment described above, and appropriate modifications, improvements, and the like are possible. For example, the front-side and rear-side bearings are not limited to ceramic ball angular ball bearings, and various rolling bearings such as angular ball bearings using steel balls or deep groove ball bearings may be applied.

It is sectional drawing which shows one Embodiment of the bearing apparatus which concerns on this invention. It is sectional drawing of the modification of the bearing apparatus shown in FIG. It is a table | surface which shows the calculation result of an Example. It is sectional drawing of the conventional bearing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Bearing apparatus 11 Rotating shaft 12, 13 Front side bearings 14, 19 Inner ring 15, 20 Outer ring 16 Housing 17, 18 Rear side bearing 21 Outer ring spacer

Claims (2)

A rotary shaft, an inner ring is fitted on the front end side of the rotary shaft, a front side bearing is fitted on the housing, and an inner ring is fitted on the rear end side of the rotary shaft, and an outer ring is fitted on the housing. A rear-side bearing that is internally fitted and is preloaded at a fixed position in combination with the front-side bearing and the rear surface, and that cooperates with the front-side bearing to rotatably support the rotary shaft; and the front-side bearing and the rear-side bearing An outer ring spacer assembled between and a bearing device,
One end side of the outer ring of the front side bearing is fixed in an axial direction to the housing, and one end side of the outer ring of the rear side bearing is opened.   The bearing device according to claim 1, wherein the outer ring spacer is formed of a material having a linear expansion coefficient smaller than that of the rotating shaft.

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