JP2014020403A - Rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling bearing in which grease is readily held in a pocket of a retainer and an inner peripheral surface of the retainer even if centrifugal force is large under a high speed condition.SOLUTION: A rolling bearing includes: an inner race having a raceway surface; an outer race having a raceway surface; a plurality of rolling elements arranged between the raceway surface of the inner race and the raceway surface of the outer race so as to be rotatable and having a rolling surface with respect to the raceway surface of the inner race and the raceway surface of the outer race; and an annular retainer for retaining the rolling elements in a pocket so as to be rotatable. The axial size of the pocket of the retainer on an outer peripheral surface side is smaller than the axial size of the pocket on an inner peripheral surface side.

Description

  The present invention relates to a rolling bearing, and can be used particularly for applications that rotate at a high speed, such as machine tools and turbochargers.

  The main spindle of the machine tool is preferably one that rotates at a high speed in order to increase machining efficiency. In addition, since a variety of materials are required to be processed, one that rotates with a high load is preferable. As lubrication methods suitable for the main shaft rotating at high speed, for example, methods such as oil mist lubrication, oil air lubrication, and jet lubrication are known. However, such a lubrication method requires ancillary facilities such as compressed air and a fueling device, and increases the initial investment and running cost of the machine tool. On the other hand, grease lubrication is a preferable lubrication method because it requires less maintenance. Examples of the high-speed rolling bearing that supports a rotating shaft that rotates at high speed include an angular ball bearing and a cylindrical roller bearing that support a machine tool spindle (spindle) and the like. As greases used for these high-speed rolling bearings, greases based on low-viscosity synthetic oils and greases increased with barium soap are used. However, even if these greases are used, the centrifugal force is high at high speeds, so the grease is easily removed from the cage pocket and the inner circumferential surface of the cage to the outer circumferential surface of the cage, and the base oil and thickener are used. Since the separation of the toner tends to proceed, poor lubrication tends to occur. In addition, since heat generation due to the stirring resistance of the lubricant becomes a big problem at high speed, the amount of grease filled is generally less than that of a normal bearing. Accordingly, there is a need for grease technology that keeps the grease in the vicinity of the rolling surface and does not cause poor lubrication for a long period of time.

  There are some which are shown in patent documents 1 to such a demand. In this technique, a fine groove for oil sump is provided on the outer peripheral surface of the cage to improve lubricity.

JP 2001-248655 A

  However, in the technique shown in Patent Document 1, since the oil retaining fine groove is provided on the outer peripheral surface of the cage, it is not possible to keep grease on the pocket of the cage or the inner peripheral surface of the cage. difficult. Therefore, the present invention provides a rolling bearing in which grease is easily held in the pocket of the cage or the inner peripheral surface of the cage even when centrifugal force is large at high speed.

  In order to achieve the above object, a rolling bearing according to the present invention includes an inner ring having a raceway surface, an outer ring having a raceway surface, and a rollable arrangement between the inner ring raceway surface and the outer ring raceway surface. In a rolling bearing having a plurality of rolling elements having a raceway surface and a rolling surface with respect to the outer ring raceway surface, and an annular cage that holds the rolling body in a pocket so as to be freely rollable, an outer peripheral surface of the pocket of the cage The axial dimension on the side is smaller than the axial dimension on the inner peripheral surface side of the pocket. Further, the pocket preferably has a taper in which the axial dimension on the outer peripheral surface side is smaller than the axial dimension on the inner peripheral surface side of the pocket.

  According to the present invention, it is possible to provide a rolling bearing in which grease is easily held in the pocket of the cage or the inner peripheral surface of the cage.

It is sectional drawing which shows the angular ball bearing with a seal | sticker as an example about schematic structure of the rolling bearing which concerns on one Embodiment of this invention. It is sectional drawing which shows the angular ball bearing with a seal | sticker as an example about the schematic structure of the conventional rolling bearing.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  Embodiments of a rolling bearing according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a longitudinal sectional view showing the structure of an angular ball bearing which is a kind of rolling bearing 1 according to the present invention. This angular ball bearing has a rolling contact between the outer race 2 having a raceway surface 2a on the inner peripheral surface, the inner race 2 having a raceway surface 3a opposite to the raceway surface 2a of the outer race 2 on the outer peripheral surface, and both raceway surfaces 2a and 3a. A plurality of rolling elements 5 (balls) arranged freely, an annular cage 6 that holds the rolling elements 5 between the outer ring 2 and the inner ring 3, and a seal 10 for holding grease in the rolling bearing It has.

  In the conventional rolling bearing shown in FIG. 2, an axial dimension B1 on the outer peripheral surface side of the pocket 7 of the cage 6 holding the rolling element 5 and an axial dimension B2 on the inner peripheral surface side of the pocket 7 are as follows. While the dimensions are substantially the same, the axial dimension of the outer peripheral surface side of the pocket of the cage for holding the rolling elements of the rolling bearing of the present invention shown in FIG. 1 is the same as the inner peripheral surface side of the pocket. Smaller than the axial dimension. Moreover, it is preferable that the rolling element contact surface 9 of the pocket has a taper in which the axial dimension on the outer peripheral surface side is smaller than the axial dimension on the inner peripheral surface side of the pocket.

  This makes it possible to retain grease and grease base oil over a long period of time because the grease that is blown from the cage pocket or cage inner surface to the outer surface of the cage due to centrifugal force during high-speed rotation can be retained on the cage inner surface. Can be supplied to the rolling elements, outer ring, and inner ring, and the lubrication life can be dramatically improved. In addition, since a large amount of grease can be retained in the pocket or inner peripheral surface side of the cage, friction due to contact between the cage and the rolling elements is reduced, and wear of the cage is unlikely to occur.

Either a urea compound or a metal soap can be used as the thickener for the grease sealed in the rolling bearing. Further, it is preferable to use a grease having a kinematic viscosity in the range of 10 to 80 mm ² / s at 40 ° C. so that no abnormal noise or torque increase occurs even at high speed. Thus, by using the rolling bearing having the cage of the present invention by grease lubrication, it becomes difficult to cause poor lubrication even under high speed, and the lubrication life can be extended.

  The following tests and observations were performed on the rolling bearings of Examples 1 to 4 and Comparative Examples 1 and 2. Table 1 shows the cage material, grease type, cage shape, bearing durability test life ratio, cage wear, and grease leakage test leakage rate of Examples 1 to 4 and Comparative Examples 1 and 4. In addition, each holder | retainer of an Example and a comparative example is reinforced with glass fiber. The conditions and observation methods for each test are as follows.

(1) Bearing endurance test In the bearing test, an angular ball bearing (inner diameter Φ50 mm) was filled with grease at 5% of the space volume, a constant pressure axial load of 1200 N was applied, and the inner ring was rotated at 18000 min ⁻¹ . The outer ring is cooled by cooling water. The time at which the abnormal temperature rises was defined as the seizure life. The seizure life is represented by 1 as the life of Comparative Example 1 and the other as a ratio thereto.

(2) Cage wear observation endurance test after bearing endurance test (1) The cage pocket portion after observation was observed, and it was observed whether there was any wear due to contact with the balls.

(3) Grease leakage test A 6210 ball bearing (outer diameter 90 mm, inner diameter 50 mm, width 20 mm) equipped with a heat-resistant rubber seal is filled with 30% grease and rotated for 100 hours at an axial load of 980 N and a rotational speed of 15000 min ^−1. The subsequent grease leakage rate was measured.

As shown in Table 1, Examples 1 to 3 which are rolling bearings of the present invention had a long life, no wear, and few grease leaks.

DESCRIPTION OF SYMBOLS 1 Rolling bearing 2 Outer ring 2a, 3a Raceway surface 3 Inner ring 5 Rolling body 6 Cage 7 Pocket 8, 9 Rolling body contact surface B1 Axial dimension on the outer peripheral surface side of pocket B2 Axial dimension on the inner peripheral surface side of pocket

Claims (2)

  An inner ring having a raceway surface, an outer ring having a raceway surface, and a plurality of rolling rings disposed between the inner ring raceway surface and the outer ring raceway surface and having rolling surfaces with respect to the inner ring raceway surface and the outer ring raceway surface. In a rolling bearing having a rolling element and an annular cage that holds the rolling element in a pocket so as to roll freely, the axial dimension on the outer circumferential surface side of the pocket of the cage is such that the inner circumferential surface side of the pocket A rolling bearing characterized by being smaller than the dimension in the axial direction. The rolling bearing according to claim 1, wherein the pocket has a taper in which an axial dimension on the outer peripheral surface side is smaller than an axial dimension on the inner peripheral surface side of the pocket.

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