JP2008032070A - Ball bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ball bearing enabling an improvement in the flow of an oil therein by improving the shape of a cage, an increase in rotating accuracy by reducing heating due to the stagnation of the oil, and capable of contributing to an increase in machining accuracy when applied to support the spindle of a machine tool. <P>SOLUTION: A plurality of balls 3 are interposed between the raceway surfaces 1a, 2a of an inner ring 1 and an outer ring 2. The ball bearing has a ring cage 4 supporting the balls 3. In the cage 4, a plurality of pockets 4c for supporting the balls 3 are disposed at the lateral intermediate position of the ring cage body 4a circumferentially at equal intervals. The projection part 4d extending to the inner diameter side is formed at the pocket-to-pocket portion 4b of the cage body 4a at the lateral center of the cage body. The surface of the projection part 4d opposed to the balls 3a is a conical surface 4da reduced in diameter toward the inner diameter side of the pockets 4c. Since the conical surface 4da is brought into contact with the balls 3, the movement of the cage 4 in the radial and circumferential directions is so restrained as to guide rolling elements. The projection part 4d is formed only on a part of the pockets 4c uniformly arranged in the circumferential direction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an angular ball bearing mainly used for supporting a main shaft of a machine tool, and more particularly, to a ball bearing of a type (rolling body guide) in which a cage is guided by a rolling element.

  There are multiple methods for restraining the cage behavior in angular ball bearing cages. These methods include the method of guiding the cage on the outer diameter surface of the bearing inner ring (inner ring guide), and the cage with a rolling element. In general, a guide method (rolling element guide) and a guide method (outer ring guide) in which a cage outer diameter surface is guided by a bearing outer ring inner diameter surface. Among these, the most general technique is rolling element guide, and as such a rolling element guide retainer, a polyamide resin material is usually injection-molded. The rolling element guide retainer is provided with a protrusion on the inner diameter side of a pocket, which is a part for holding the rolling element, and restrains the rolling element with a conical portion of the protrusion. Usually, this protrusion is provided between all the pockets (for example, refer patent document 1).

FIG. 8 shows the shape of a conventional general rolling element guide retainer. The illustrated retainer 50 is formed in an annular shape by injection molding of a polyamide-based resin material or the like, and is a pocket for retaining a ball 53 in the middle in the width direction at a plurality of circumferential positions of the annular retainer body 51. 54 are arranged equally. A protrusion 55 is provided in each pocket portion 52 of the cage main body 51, and a conical surface in which the surfaces facing the balls 53 in the pockets 54 on both sides of the protrusion 55 become a small diameter toward the inner diameter side of the cage main body 51. A surface 55a is formed. The cage 50 serves as a rolling element guide that restricts the radial and circumferential movement of the cage 50 by the conical surface 55a. Usually, the protrusion 55 is formed in a trapezoidal shape when viewed in the circumferential direction at the center in the width direction of the cage body 51 and is provided between all the pockets 54.
JP 2004-124951 A

  In recent years, the rotational speed of bearings has increased, and along with this, bearing lubrication is often applied from grease lubrication to oil lubrication. However, in rolling bearings that support machine tools, when oil lubrication is applied, a certain amount of lubricating oil passes inside the bearing. This increases bearing torque and generates heat. As a result, the machining accuracy of the workpiece may deteriorate, or the bearing may overheat.

In the case of the ball bearing provided with the cage 50 of FIG. 8, since the projections 55 projecting toward the inner diameter side of the cage 50 are provided between all the pockets 54, the projections 55 narrow the bearing internal space. It may be a factor that obstructs the flow of the lubricating oil, and may cause deterioration of the work machining accuracy and bearing seizure as described above.
As a method for suppressing the heat generation of the bearing, there are methods for adjusting the oil amount and the air amount, but a large-scale device is required for that purpose. That is, in the main spindle of the machine tool, since heat generation causes elongation of the shaft and greatly affects the machining accuracy of the workpiece, it is important to suppress heat generation of the bearing as much as possible. Therefore, a separate cooling structure is also provided. Some of them are equipped with a device capable of supplying a quantitatively stable lubricating oil so as to be able to lubricate in the vicinity of the boundary lubrication region in order to suppress heat generation of the bearing. In order to perform stable bearing operation under such a lubrication environment, it is necessary to always supply new lubricating oil to the inside of the bearing reliably, and it is required to increase the efficiency of supply and discharge oil by expanding the bearing internal space.

  The object of the present invention is to improve the flow of oil inside the bearing by devising the shape of the cage, to reduce heat generation due to oil retention, thereby improving the rotation accuracy, and to machine tools The present invention is to provide a ball bearing that can contribute to improvement of machining accuracy when applied to support of a main shaft of the main body.

  In the ball bearing of the present invention, there are a plurality of balls as rolling elements between the raceways of the inner ring and the outer ring, and there is a cage that holds the plurality of balls. In the middle of the width direction, a plurality of pockets for holding the balls are equally distributed in the circumferential direction, and a protrusion extending toward the inner diameter side is provided in the center of the cage body width direction in the portion between the pockets of the cage body, The surface of the protrusion facing the ball is a conical surface having a smaller diameter toward the inner diameter side of the cage body, and the conical surface is in contact with the ball so that the cage moves in the radial and circumferential directions. In the ball bearing which is a rolling element guide type to be regulated, the protrusions are provided only for some of the pockets which are evenly arranged in the circumferential direction.

According to this configuration, since the protruding portion that protrudes toward the inner diameter side of the cage body is provided only for a part of the pockets, the space penetrating from the bearing width surface is increased, and the inside of the bearing is increased. Oil flow is good. The protrusion is a conical surface facing the ball and functions as a rolling element guide for the cage, but the protrusion corresponds to a part of the pockets that are evenly arranged in the circumferential direction. If provided, the function of rolling element guidance is obtained. Further, although the number of protrusions is reduced, the function of keeping the balls of the cage in an equidistant position is maintained because the portion between the pockets of the cage body is interposed between the balls.
Since the oil flow inside the bearing is thus improved, there is no increase in bearing torque or heat generation due to stirring resistance, and the occurrence of overheating of the bearing can be suppressed. When applied to support of the spindle of a machine tool, the rotation accuracy of the spindle is improved, and the machining accuracy of the workpiece is improved.

In the present invention, the number of the protrusions may be ½ or less of the number of pockets. If the number of protrusions is reduced, the effect of improving the oil flow in the bearing is difficult to obtain.
It is preferable that the number of pockets is at most ½.

  The ball bearing of the present invention may be an angular ball bearing for a machine tool main shaft. As a result, the rotation accuracy of the spindle is improved, and the machining accuracy of the workpiece is also improved.

  In the ball bearing of the present invention, there are a plurality of balls as rolling elements between the raceways of the inner ring and the outer ring, and there is a cage that holds the plurality of balls. In the middle of the width direction, a plurality of pockets for holding the balls are equally distributed in the circumferential direction, and a protrusion extending toward the inner diameter side is provided in the center of the cage body width direction in the portion between the pockets of the cage body, The surface of the protrusion facing the ball is a conical surface having a smaller diameter toward the inner diameter side of the cage body, and the conical surface is in contact with the ball so that the cage moves in the radial and circumferential directions. In the ball bearing that is a rolling element guide type to be regulated, the protrusions are provided only for some of the pockets that are evenly arranged in the circumferential direction of the pockets. It is possible to reduce the heat generated by oil retention. This makes it possible to improve the rotational accuracy. Therefore, when applied to support of the spindle of machine tools, it can contribute to the improvement of machining accuracy.

  A first embodiment of the present invention will be described with reference to FIGS. The ball bearing A is an angular ball bearing, and includes an inner ring 1, an outer ring 2, a ball 3 that is a rolling element interposed between the raceway surfaces 1 a and 2 a of the inner and outer rings 1 and 2, and a ball 3. And an annular retainer 4 that is held at predetermined intervals along the direction.

The cage 4 is annularly injection-molded with an injection-moldable resin such as a polyamide-based resin material, and a plurality of pockets 4c that hold the balls 3 in the middle of the width direction of the annular cage body 4a. (FIG. 3) are equally distributed in the circumferential direction.
In each pocket portion 4b of the cage main body 4a, a protrusion 4d extending partially toward the inner diameter side of the cage 4 is formed at the center in the cage body width direction. The protrusion 4d has a trapezoidal cross-sectional shape along the axial direction. The protruding portion 4d has a conical surface 4da whose side surfaces on both sides facing the ball 3 have a small diameter toward the inner diameter side of each pocket 4c. A portion constituted by the cage body 4a of the pocket 4c is a cylindrical surface, and a conical surface 4da on the inner surface of the protruding portion 4d is smoothly continued following the substantially cylindrical surface. The conical surface 4da has an inclination and an inner diameter substantially along the inner surface of the ball 3. The conical surface 4da restricts the movement of the retainer 4 in the radial direction and the circumferential direction, and serves as a rolling element guide.
The cylindrical surface formed by the cage main body 4a of the pocket 4c is fitted to the portion on the outer diameter side from the vicinity of the center of the arrangement of the balls 3 (that is, the pitch circle diameter). Further, the cylindrical surface may be slightly conical with a large diameter on the outer diameter side.

  The illustrated cage 4 has twelve pockets 4c in the circumferential direction, and a pair of projections 4D formed by a pair of projections 4d provided on adjacent pillars 2b is three pairs in the circumferential direction of the cage 4. It is arranged. Therefore, between the protrusion pair 4D, two column parts 2b each having no protrusion 4d are equally arranged at three locations in the circumferential direction of the retainer 4.

According to the ball bearing having the above configuration, the protrusion 4d protruding toward the inner diameter side of the cage 4 is provided only for a part of the pockets 4c of the pockets 4c. The oil flow inside the bearing becomes better. The protrusion 4d has a conical surface 4da that faces the ball 3, and functions the cage 4 as a rolling element guide, but with respect to some pockets 4 that are evenly arranged in the circumferential direction. If the protrusion 4d is provided, the rolling element guide function can be obtained. Further, although the number of the protrusions 4d is reduced, since the inter-pocket portion 4b of the cage main body 4a is interposed between the pockets 4, the function of keeping the balls 3 of the cage 4 in the equidistant position is maintained.
Since the oil flow inside the bearing is thus improved, there is no increase in bearing torque or heat generation due to stirring resistance, and the occurrence of overheating of the bearing can be suppressed. When applied to support of the spindle of a machine tool, the rotation accuracy of the spindle is improved, and the machining accuracy of the workpiece is improved.

  FIG. 6 shows another example of the cage. The retainer 4 of this example is similar to the above in that it includes 12 pockets 4c, but four pairs of protrusions 4D are equally arranged in the circumferential direction of the retainer 4, and the protrusions 4D There is a difference in that the column portions 2b that do not have the protruding portions 4d are equally arranged at four locations in the circumferential direction of the cage 4 one by one. In the case of this embodiment, since the number of the column parts 2b which do not have the projection part 4d is small compared with the said embodiment, the smoothness of the flow of the lubricating oil supplied to the internal space of the ball bearing A falls a little. However, the stability of the behavior of the cage 4 is increased by the rolling element guide function of the protrusion pair 4D.

  Thus, the smoothness of the flow of the lubricating oil and the stability of the behavior of the cage 4 vary depending on the number of the protrusions 4D and the pillars 2b that do not have the protrusions 4d. Therefore, these numbers are appropriately set in consideration of both characteristics depending on the conditions of the application target. In particular, when applied to support of the spindle of a machine tool, it is desirable that the number of protrusion pairs 4D is three or more and ½ or less of the number of pockets 4c. The number of protrusions 4d is preferably ½ or less of the number of pockets 4c.

  FIG. 7 shows an example of a machine tool spindle device provided with the ball bearing A of the present invention. As the ball bearing A, the angular ball bearing of any one of the first and second embodiments is used. In the spindle device 20, two of the ball bearings A are used as a back surface combination. The two ball bearings A rotatably support both ends of the main shaft 22 in the housing 21. The inner ring 1 of each ball bearing A is positioned by a front side inner ring positioning spacer 23 and a rear side inner ring spacer 24, and is fastened and fixed to the main shaft 22 by an inner ring fixing nut 25. The outer ring 2 is positioned and fixed in the housing 21 by an outer ring positioning spacer 26 on the front side, an outer ring spacer 27 on the back side, and outer ring pressing lids 28 and 29.

  The spindle 22 is provided with a chuck (not shown) for detachably attaching a tool or a work (not shown) to the front end 22a, and a drive source such as a motor transmits rotation to the rear end 22b. They are connected via a mechanism (both not shown). The motor may be built in the housing 21. Lubricating oil is supplied to the internal space of each ball bearing A by lubricating oil supply means (not shown). The spindle device can be applied to various machine tools such as a machining center, a lathe, a milling machine, and a grinding machine.

  When the ball bearing A is applied to support the main shaft 22 of such a spindle device (machine tool) 20, the flow of lubricating oil in the inner space is good, so that heat generation is suppressed and the rotation accuracy of the main shaft 22 is reduced. Improves the machining accuracy of the workpiece. In particular, such a good flow of the lubricating oil is extremely effective in a machine tool whose speed is increasing.

In each of the above embodiments, the protrusion 4d of the cage 4 has the conical surface 4da on both sides. However, for the pocket 4c where the protrusion 4d is located only on one side, the protrusion on the pocket 4c side is provided. The side surface of the portion 4d can have any shape, and for example, may be a side surface shape that is farther from the ball 3 than the conical surface.
Moreover, although the example of the single-row angular contact ball bearing was described in the said embodiment, a double-row angular contact ball bearing may be sufficient. In FIG. 7, the example in which the main shaft 22 is supported by the two angular ball bearings A in combination on the back surface is shown. Furthermore, the ball bearing of the present invention can be applied to industrial machines other than machine tools.

It is a partially cutaway sectional view of a ball bearing concerning a 1st embodiment of this invention. It is a top view which shows an example of the holder | retainer integrated in the ball bearing of the embodiment. FIG. 3 is a partially expanded view seen from the direction of line III in FIG. 2. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 3. FIG. 5 is a cross-sectional view taken along line VV in FIG. 4. It is a top view which shows the modification of a holder | retainer. It is sectional drawing which shows an example of the spindle apparatus for machine tools provided with the ball bearing of 1st Embodiment. It is a top view which shows the example of the conventional holder | retainer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Inner ring 1a ... Raceway surface 2 ... Outer ring 2a ... Raceway surface 3 ... Ball 4 ... Cage 4a ... Ring part 4b ... Inter-pocket part 4c ... Pocket 4d ... Projection part 4da ... Conical surface 21 ... Spindle device (machine tool)
22 ... Spindle A ... Angular contact ball bearing (ball bearing)

Claims (3)

  A plurality of balls, which are rolling elements, are interposed between the raceway surfaces of the inner ring and the outer ring, and there is a cage that holds the plurality of balls, and this cage is located in the middle of the annular cage body in the width direction. A plurality of pockets for holding balls are equally distributed in the circumferential direction, and a protrusion extending toward the inner diameter side is provided at the center in the width direction of the cage body in the portion between the pockets of the cage body. The opposing surface is a conical surface having a small diameter toward the inner diameter side of the cage main body, and the conical surface is in contact with the balls so that the rolling element guide type regulates the radial and circumferential movement of the cage. The ball bearing according to claim 1, wherein the protrusions are provided only for a portion of the pockets that are equally arranged in the circumferential direction.   2. The ball bearing according to claim 1, wherein the number of the protrusions is equal to or less than ½ of the number of pockets. 3. The ball bearing according to claim 1, wherein the ball bearing is an angular ball bearing for a machine tool spindle.

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