Rolling bearing

Abstract

In a rolling bearing 1, a cage 5 has an annular guided surface Sb that is guided by an annular guide surface Sa of an outer ring 3 during operation of the bearing, and pockets 6 are formed by circular holes having a uniform opening dimension W in the radial direction, large pockets 6A and small pockets 6B being provided as the pockets 6. When the design value of the radial clearance Ga2 between the guide surface Sa and the guided surface Sb is denoted by δ, the size of the radial clearance Ga2 during operation of the bearing is denoted by δ0, and the sizes of the circumferential clearances Gb1, Gb2 respectively formed between balls 4 and the large pockets 6A and small pockets 6B in the retainer 5 in a neutral state are denoted by ε1 and ε2, the inequality expression ε2 < δ0 < ε1 and the inequality expression 0 mm < (δ - δ0) < 0.5 mm are established, and a cage movable region 10 forms a non-perfect circular shape that is circumscribed by a circle of which the diameter is the size δ0 of the radial clearance Ga2 during operation of the bearing.

Description

Rolling bearings

[0001] The present invention relates to a rolling bearing.

[0002] 9A shows a schematic cross-sectional view of a rolling bearing 100. The rolling bearing 100 shown in the figure comprises a pair of raceways (inner ring 101 and outer ring 102) that are arranged radially opposite each other and rotate relative to each other about a central axis via a plurality of rolling elements (here, balls) 103, and an annular cage 104 that holds the plurality of rolling elements 103 at intervals in the circumferential direction. The cage 104 is fitted between the pair of raceways so that, in an unloaded state in which gravity, rotational force, etc. are not acting on the rolling bearing, radial gaps 111 and 112 are formed between the cage 104 and the outer peripheral surface 101 a of the inner ring 101 and the inner peripheral surface 102 a of the outer ring 102, respectively, and a circumferential gap 113 is formed between the cage 104 and the rolling elements 103 that are accommodated in pockets 105 each consisting of a circular hole with a constant opening dimension along the radial direction. The radial gaps 111 and 112 are also called "guide gaps," and the circumferential gap 113 is also called "pocket gap."

[0003] Rolling bearings can be broadly classified into raceway guided and rolling element guided types depending on the guide type of the cage 104, and raceway guided types can be further classified into outer ring guided and inner ring guided types. In a broad sense, the outer ring guided type is a type in which the radial clearance 112 is smaller than the radial clearance 112 of the two radial clearances 111 and 112. Outer ring guided bearings include types in which the circumferential clearance 113 formed between the pocket forming surface 105a of the cage 104 in the neutral position (the cage 104 in an unloaded state) and the rolling elements 103 is larger than the radial clearance 112, and types in which it is smaller than the radial clearance 112. Figures 9A and 9B show the former, and Figures 10A and 10B show the latter. Although not shown, the inner ring guided type is, in a broad sense, a type in which the radial clearance 111 is smaller than the radial clearance 112 of the two radial clearances 111 and 112. Also, although not shown in the figures, the rolling element guided type is a type in which the opening dimensions of the pocket 105 are not constant along the radial direction, and the radial gap formed between the pocket forming surface 105a and the rolling element 103 is smaller than the two radial gaps 111 and 112.

[0004] During operation of the rolling bearing 100, in which the inner ring 101 and the outer ring 102 rotate relative to each other, the cage 104 may experience an abnormally high-speed whirling (self-excited vibration at several times the cage rotation frequency), also known as the high-speed whirl phenomenon. This high-speed whirl phenomenon is said to occur even when the dn value, calculated as the product of the inner diameter [mm] and the rotation speed [rpm] of the rolling bearing 100, is approximately 1,500,000 or less (dn≦1,500,000). The high-speed whirl phenomenon may cause abnormal noise, vibration, increased torque, torque fluctuation, heat generation, and the like. The high-speed whirl phenomenon is said to be caused, for example, by frictional forces generated by contact between the guide surfaces of the raceways and the guided surfaces of the cage 104, or by frictional forces generated by contact between the pocket-forming surfaces 105 a of the cage 104 and the rolling elements 103.

[0005] The mechanism by which the high-speed whirl phenomenon occurs, which is caused by frictional forces generated by contact between the guide surface of the raceway ring and the guided surface of the cage 104, will be explained using the outer ring guide type rolling bearing 100 shown in Figures 9A and 9B as an example. In this case, the guide surface of the raceway ring is the inner peripheral surface 102a of the outer ring 102, and the guided surface of the cage 104 is the outer peripheral surface of the cage 104. Although not shown, in an inner ring guide type rolling bearing, the "guide surface of the raceway ring" = "the outer peripheral surface of the inner ring", and the "guide surface of the cage" = "the inner peripheral surface of the cage".

[0006] First, as shown in Fig. 9A , when the retainer 104 is displaced in the 0 o'clock (12 o'clock) direction relative to the axis O, the retainer 104 comes into contact with the inner circumferential surface 102a of the outer ring 102 at the 0 o'clock position. At this time, if the inner ring 101 is rotating clockwise, a frictional force F acts on the retainer 104 in a direction that displaces it in the 9 o'clock direction. When the retainer 104, displaced by the frictional force F, comes into contact with the inner circumferential surface 102a of the outer ring 102 at the 9 o'clock position, a frictional force F is generated on the retainer 104 that displaces it in the 6 o'clock direction, as shown in Fig. 9B . Then, as the inner ring 101 continues to rotate and the above-mentioned phenomenon (displacement of the retainer 104 and contact with the inner circumferential surface 102a of the outer ring 102) is repeated, the retainer 104 will whirl at high speed in the direction opposite to the rotational direction of the inner ring 101.

[0007] Next, the mechanism by which the high-speed whirl phenomenon occurs, which is caused by frictional forces generated by contact between the pocket forming surface 105 a of the cage 104 and the rolling elements 103, will be described with reference to FIGS. 10A and 10B . As shown in FIG. 10A , when the cage 104 is displaced toward 0 o'clock (12 o'clock) with respect to the axis O, the rolling elements 103 located at the 3 o'clock and 9 o'clock positions come into contact with the pocket forming surface 105 a at the 6 o'clock position. If the inner ring 101 is rotating clockwise at this time, a frictional force F is generated in the cage 104, displacing it toward the 3 o'clock position. When the cage 104 is displaced by this frictional force F, the rolling elements 103 located at the 0 o'clock and 6 o'clock positions come into contact with the pocket forming surface 105 a at the 9 o'clock position, as shown in FIG. 10B . Accordingly, a frictional force F is generated that displaces the cage 104 toward the 6 o'clock position. This phenomenon is subsequently repeated, causing the cage 104 to whirl at high speed in the same direction as the rotation of the inner ring 101.

[0008] In order to prevent the occurrence of abnormal noise, vibration, etc. resulting from the high-speed whirling phenomenon of the cage as mentioned above, for example, in the rolling bearing described in Patent Document 1 below, a predetermined amount of imbalance is intentionally imparted to the cage, causing the cage to rotate in an eccentric state (with part of the cage constantly in contact with the raceway).

[0009] JP 2011-196513 A

[0010] However, to realize the technical means described in Patent Document 1, it is necessary to first form the cage into a point-asymmetric shape, which requires a lot of work to precisely machine the cage. Furthermore, to ensure the durable life required of a rolling bearing, it is necessary to suppress wear at the constant contact area between the cage and the raceway. Therefore, it is necessary to take measures such as subjecting the opposing surfaces of the raceway and the cage, which come into contact with each other, to finishing processing such as precision polishing, and finishing these two surfaces with extremely high precision. Therefore, realizing the technical means described in Patent Document 1 poses the problem of high costs.

[0011] In view of the above circumstances, an object of the present invention is to provide a low-cost rolling bearing that can prevent, to the greatest extent possible, the occurrence of the high-speed whirl phenomenon and the resulting abnormal noise and vibrations.

[0012] The present invention, which has been devised to achieve the above object, is a rolling bearing comprising a pair of raceways arranged radially opposite to each other and rotating relative to each other via a plurality of rolling elements, and an annular cage in which a plurality of pockets each accommodating the rolling elements individually are formed at intervals in the circumferential direction, one of the pair of raceways having an annular guide surface, and the cage having an annular guided surface facing the guide surface in the radial direction, each pocket being a circular hole with a constant opening dimension along the radial direction, wherein at least one of the plurality of pockets is formed as a large pocket, and the remaining pockets are formed as small pockets with opening dimensions smaller than that of the large pocket, and the design value of the radial clearance formed between the guide surface and the guided surface is δ, and the size of the radial clearance when the bearing is in operation is δ ０ The size of the circumferential clearances formed between the large pocket forming surface and the small pocket forming surface of the cage in a neutral state and the rolling elements is defined as ε １ and ε ２ Then, ε ２ <δ ０ <ε １ and 0 mm < (δ - δ ０ ) < 0.5 mm is satisfied, and when the cage movable area is defined as the area surrounded by lines connecting the outer edges of a scatter diagram obtained by plotting countless positions on a two-dimensional coordinate system where the cage can exist without contacting a pair of raceways and rolling elements, this cage movable area is determined to be the area surrounded by lines connecting the outer edges of the scatter diagram when the cage movable area is within the range of the above-mentioned radial clearance δ during bearing operation. ０ The "neutral state" in this invention means that the center of the circular hole in the cage that forms the pocket and the center of the rolling element are aligned, and they are not in contact with each other.

[0013] First, as explained with reference to Figures 9 and 10, during bearing operation in which a pair of raceways rotate relative to one another, the frictional force generated by contact between the cage and raceways and the frictional force generated by contact between the cage and rolling elements are directed in opposite directions. Therefore, if the above two types of frictional forces can be generated in a balanced manner during bearing operation, it is thought that one of the above two types of frictional forces, both of which cause the high-speed whirl phenomenon, can be reduced or offset by the other frictional force.

[0014] Therefore, in the rolling bearing according to the present invention, at least one of the pockets formed by the circular holes provided in the cage is formed as a large pocket, and the remaining pockets are formed as small pockets with opening dimensions smaller than those of the large pocket, and further, the size δ of the radial clearance (= "guiding clearance") formed between the guide surface of the raceway ring and the guided surface of the cage during bearing operation is ０ and the size ε of the circumferential clearances (= "pocket clearances") formed between the large pocket forming surface (surface forming the large pocket) and the small pocket forming surface (surface forming the small pocket) of the cage in the neutral state and the rolling elements. １ and ε ２ Between ２ <δ ０ <ε １ The following inequality is established. When this configuration is adopted, it becomes possible to switch between contact between the rolling elements and the small pockets of the cage and contact between the guide surfaces of the raceways and the guided surfaces of the cage due to radial displacement of the cage during bearing operation. Therefore, it becomes possible to reduce or cancel out one of the two types of frictional forces that occur during bearing operation by using the other frictional force.

[0015] Normally, the guide clearance during bearing operation is δ ０ The clearance becomes smaller than the designed value δ due to expansion of the cage caused by heat and centrifugal force. This reduction (δ - δ ０ ) is at most about 0.5 mm under conditions where the high-speed whirl phenomenon occurs, and 0 mm < (δ - δ ０ ) < 0.5 mm.

[0016] Even when the above two inequalities are satisfied, depending on the relationship between the pocket arrangement and the radial clearance, there is a possibility that only the small pockets of the cage will come into contact with the rolling elements, and that the guide surface of the raceway ring will not come into contact with the guided surface of the cage. In this case, the expected whirl suppression effect cannot be achieved. Therefore, in the present invention, when the area surrounded by the lines connecting the outer edges of the scatter diagram obtained by plotting countless positions on a two-dimensional coordinate system where the cage can exist without contacting a pair of raceways and rolling elements is defined as the "cage movable area," the area surrounded by the lines connecting the outer edges of the scatter diagram is defined as the "cage movable area." When the size of the radial clearance δ when the bearing is in operation is δ, the cage movable area is ０ The pocket clearances of the small pockets, the design values ​​of the guide clearances, and the arrangement of the large and small pockets are devised so that the non-circular shape is circumscribed by a circle with a diameter of . This makes it possible to appropriately switch between contact between the rolling elements and the (small pockets of) the cage and contact between the guide surface of the raceway ring and the guided surface of the cage by displacing the cage.

[0017] The rolling bearing according to the present invention is able to prevent the occurrence of the high-speed whirl phenomenon by providing the cage with pockets consisting of two types of circular holes, one large and one small, with different opening dimensions, and can be realized more easily and at lower cost than the technical means described in Patent Document 1. Furthermore, due to the configuration of the present invention, the guided surface of the cage does not always come into contact with the guide surface of the raceway ring, and the frequency of contact between the guide surface and the guided surface can be reduced compared to the rolling bearing described in Patent Document 1, so there is no need to finish the guide surface and guided surface to an extremely high level of precision.

[0018] The contact portion of the cage movable region with respect to the circumscribing circle is arc-shaped with a length in the circumscribing circle's circumferential direction, and a plurality of these arc-shaped contact portions are provided at intervals in the circumscribing circle's circumscribing circle's circumscribing direction. It is particularly preferable to provide three or more arc-shaped contact portions at equal intervals in the circumscribing circle's circumscribing direction. This allows the cage to finely switch its contact target at regular intervals, thereby enabling one of the two types of frictional forces generated during bearing operation to be appropriately reduced or offset by the other frictional force.

[0019] In the above configuration, the arrangement of the multiple pockets (large pockets and small pockets) can be, for example, such that when the retainer is divided equally into six areas in the circumferential direction, the large pockets are arranged in the first, third, and fifth areas clockwise, and the small pockets are arranged in the second, fourth, and sixth areas.

[0020] In the above configuration, the guide surface may be the inner peripheral surface of the outer ring of the pair of raceways that is arranged radially outside the retainer, or the outer peripheral surface of the inner ring of the pair of raceways that is arranged radially inside the retainer.

[0021] As described above, according to the present invention, it is possible to realize at low cost a rolling bearing that can prevent as much as possible the occurrence of the high-speed whirl phenomenon and the abnormal noise and vibrations that may result from it.

[0022] 9A is a partial schematic plan view of a rolling bearing according to an embodiment of the present invention. FIG. 9B is a cross-sectional view taken along the arrows A1-A1 in FIG. 1. FIG. 9C is a cross-sectional view taken along the arrows A2-A2 in FIG. 1. FIG. 9D is a schematic plan view of a cage incorporated in the rolling bearing shown in FIG. 1. FIG. 9E is a diagram showing the cage movable area, etc. of a rolling bearing employing the cage shown in FIG. 4. FIG. 9F is a schematic view for explaining how to determine the cage movable area. FIG. 9G is a diagram showing the cage movable area, etc. of a rolling bearing employing a cage according to a modified example. FIG. 9H is a diagram showing the cage movable area, etc. of a rolling bearing not having the configuration of the present invention. FIG. 9H is a schematic cross-sectional view of an outer ring guide type rolling bearing in which the radial clearance between the outer ring inner diameter and the cage outer diameter is smaller than the circumferential clearance between the pocket forming surface and the rolling elements. FIG. 9H is a cross-sectional view showing the state in which the cage of the rolling bearing shown in FIG. 9A has been displaced radially. FIG. 9I is a schematic cross-sectional view of an outer ring guide type rolling bearing in which the radial clearance between the outer ring inner diameter and the cage outer diameter is larger than the circumferential clearance between the pocket forming surface and the rolling elements. 10B is a cross-sectional view showing a state in which the cage of the rolling bearing shown in FIG. 10A is displaced in the radial direction. FIG.

[0023] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Unless otherwise specified, the terms "axial direction," "radial direction," and "circumferential direction" used below to indicate directionality refer to a direction parallel to the axis O of the rolling bearing 1 shown in Fig. 1, a radial direction of a circle centered on the axis O, and a circumferential direction of a circle centered on the axis O, respectively. In Fig. 2 and Fig. 3, the "axial direction," "radial direction," and "circumferential direction" are indicated by arrows X, Y, and Z, respectively.

[0024] Fig. 1 is a partial schematic plan view of a rolling bearing 1 according to an embodiment of the present invention, and more specifically, a partial schematic plan view of the rolling bearing 1 in an unloaded state in which gravity, rotational force, and the like are not acting. Fig. 2 is a cross-sectional view taken along line A1-A1 in Fig. 1, and Fig. 3 is a cross-sectional view taken along line A2-A2 in Fig. 1. The rolling bearing 1 shown in Fig. 1 and other figures is a so-called angular contact ball bearing comprising a pair of raceways (inner ring 2 and outer ring 3) made of a highly rigid metal material such as bearing steel (high carbon chromium bearing steel), a plurality of balls 4 rollably interposed between the inner ring 2 and the outer ring 3, and an annular cage 5 that holds the plurality of balls 4 at intervals in the circumferential direction, the balls 4 contacting an arc-shaped inner raceway surface 2b formed on the outer peripheral surface 2a of the inner ring 2 and an arc-shaped outer raceway surface 3b formed on the inner peripheral surface 3a of the outer ring 3 at a contact angle α.

[0025] The cage 5 has a plurality of pockets 6 formed therein, each accommodating one ball 4, and the cage 5 shown in the figure has a total of 24 pockets 6 formed at intervals of 15°. As shown in Figures 2 and 3, each pocket 6 is a circular hole with a constant opening dimension (pocket diameter) W along the radial direction, and the pocket forming surface 7 of the cage 5, which forms the pockets 6, is formed as a cylindrical surface with a constant diameter.

[0026] A resin cage made of a resin material such as PA66 resin or phenolic resin (particularly, cloth-based phenolic resin) is used as the cage 5. However, as long as each pocket 6 is formed with a circular hole as described above, it is also possible to use a known cage other than a resin cage as the cage 5, such as a so-called machined cage obtained by cutting a metal material into a predetermined shape, or a pressed cage obtained by joining a pair of cage blanks that have been press-molded (punched) into a predetermined annular shape.

[0027] 2 and 3 , in an unloaded state in which gravity, rotational force, and the like are not acting on the rolling bearing 1, the cage 5 is in a neutral state (a state in which it is not in contact with the balls 4, or the inner ring 2 or the outer ring 3) in which it forms radial clearances between itself and the inner ring 2 and the outer ring 3, and forms circumferential clearances between itself and the balls 4 accommodated in the pockets 6. Therefore, when the cage 5 is in the neutral state, a first radial clearance Ga1 is formed between the outer peripheral surface 2 a of the inner ring 2 and the inner peripheral surface 5 a of the cage 5, a second radial clearance Ga2 is formed between the inner peripheral surface 3 a of the outer ring 3 and the outer peripheral surface 5 b of the cage 5, and a circumferential clearance Gb, also referred to as a "pocket clearance," is formed between the balls 4 and the pocket-forming surface 7 of the cage 5. By setting these various clearances, good operability of the rolling bearing 1 is ensured.

[0028] In the rolling bearing 1 of this embodiment, the second radial clearance Ga2 is smaller than the first radial clearance Ga1. For this reason, the rolling bearing 1 of this embodiment is an angular contact ball bearing in which the guide surface Sa, as referred to in the present invention, is formed by the inner circumferential surface 3a of the outer ring 3, and the guided surface Sb is formed by the outer circumferential surface 5b of the cage 5, and the second radial clearance Ga2 forms the "guide clearance."

[0029] The characteristic configuration of the rolling bearing 1 of this embodiment having the above configuration will be explained using as a representative example a case in which the inner diameter (diameter of the guide surface Sa) of the outer ring 3 is designed to be 95.26 mm, the outer diameter (diameter of the guided surface Sb) of the cage 5 is designed to be 95 mm, and the ball diameter is designed to be 8.73 mm. In this case, the design value δ of the second radial clearance Ga2 as a guide clearance is 0.26 mm.

[0030] The cage 5 of the rolling bearing 1 forms two types of pockets 6, each consisting of a circular hole, with different opening dimensions (pocket diameters) W. That is, the pockets 6 include large pockets 6A and small pockets 6B whose pocket diameter W is smaller than that of the large pockets 6A, and at least one large pocket 6A and one small pocket 6B are provided. In this embodiment, a total of 24 pockets 6 are provided at 15° intervals, and large pocket groups BG, each consisting of four consecutive large pockets 6A in the circumferential direction, and small pocket groups SG, each consisting of four consecutive small pockets 6B in the circumferential direction, are arranged alternately in groups of three in the circumferential direction, as shown in FIG.

[0031] The balls 4 housed in each pocket 6 are common balls with the same diameter. Therefore, the circumferential gap Gb formed between the pocket forming surface 7 (large pocket forming surface) that forms the large pocket 6A and the ball 4 is larger than the circumferential gap Gb formed between the pocket forming surface 7 (small pocket forming surface) that forms the small pocket 6B and the ball 4. Hereinafter, when distinguishing between the two circumferential gaps Gb that differ in size, the former will be referred to as the "large pocket gap Gb1" and the latter as the "small pocket gap Gb2."

[0032] The pocket diameter W of the large pocket 6A and the small pocket 6B is determined by the size δ of the guide clearance (second radial clearance Ga2) during bearing operation. ０ and the size of the large pocket gap Gb1 ε １ and the size of the small pocket gap Gb2 ε ２ Between ２ <δ ０ <ε １ The first inequality (magnitude relationship) is set to hold.

[0033] Here, the size of the guide clearance during bearing operation δ ０is determined taking into consideration the bearing temperature T under operating conditions under which the high-speed whirl phenomenon of the cage 5 occurs. As mentioned above, the high-speed whirl phenomenon is said to occur even when the dn value, calculated as the product of the inner diameter [mm] of the rolling bearing and the rotational speed [rpm], is approximately 1,500,000 or less (dn≦1,500,000), and the bearing temperature in this case is set to T≈30°C. When the guide ring is the outer ring 3 (when the guide surface Sa is provided on the outer ring 3), as in the rolling bearing 1 according to this embodiment, the magnitude δ of the guide clearance during bearing operation ０ can be calculated using the following formula: ０ = δ + d ｒ ・(T-20)・α ｒ -d ｃ ・(T-20)・α ｃ The various parameters in the above formula are: δ: design value of guide clearance [mm], T: bearing temperature [°C], d ｒ : diameter of guide surface Sa [mm], d ｃ : diameter of guided surface Sb [mm], α ｒ : coefficient of linear expansion of (the material forming) the outer ring 3 [1 / °C], α ｃ : Linear expansion coefficient of the cage 5 [1 / °C], where δ is 0.26, T is 30, d ｒ : 95.26, d ｃ : 95.0, α ｒ : 12.5 x 10 －６ , α ｃ : 50 x 10 －５ The linear expansion coefficient of the outer ring 3 is that of SUJ2, which is classified as bearing steel according to JIS G 4805, and the linear expansion coefficient of the cage 5 is that of a fabric-based phenolic resin. ０ = 0.22 mm.

[0034] As described above, the diameter of the ball 4 is 8.73 mm, and the size of the guide clearance during bearing operation is δ ０ = 0.22 mm, the above ε ２ <δ ０ <ε １ In order to establish the first inequality, for example, if the pocket diameter W of the large pocket 6A is 9.13 mm and the size ε of the large pocket gap Gb1 is １is set to 0.4 mm, and the pocket diameter W of the small pocket 6B is set to 8.93 mm, and the size ε of the small pocket gap Gb2 is set to ２ is set to 0.2 mm.

[0035] 9 and 10 , when the rolling bearing 1 is in operation with the inner ring 2 and outer ring 3 as a pair of raceways rotating relative to one another, the frictional force generated by contact between the cage 5 and the raceways and the frictional force generated by contact between the cage 5 and the balls 4 are directed in opposite directions. Therefore, in the rolling bearing 1 according to this embodiment, the two types of frictional forces are generated in a well-balanced manner when the bearing is in operation, so that one of the two types of frictional forces that cause the high-speed whirl phenomenon is reduced or offset by using the other frictional force.

[0036] Specifically, a large pocket 6A and a small pocket 6B having an opening dimension W smaller than that of the large pocket 6A are provided as the pockets 6 for accommodating the balls 4, and further, the above-mentioned ε ２ <δ ０ <ε １　 The first inequality (magnitude relationship) is set to hold.

[0037] In this case, due to radial displacement of the cage 5 during bearing operation, it is possible to switch between contact between the balls 4 and the pocket forming surface 7 of the small pocket 6B and contact between the inner peripheral surface 3a (guiding surface Sa) of the outer ring 3 and the outer peripheral surface 5b (guided surface Sb) of the cage 5. This makes it possible to reduce or cancel out one of the two types of frictional forces, which are directed in opposite directions, by the other frictional force, thereby suppressing the occurrence of the high-speed whirl phenomenon.

[0038] In order to achieve the above function during bearing operation, it is necessary to switch the contact object of the cage 5 between the balls 4 and the outer ring 3 due to displacement of the cage 5 even when the outer ring 3 or the cage 5 undergoes thermal expansion, etc. Therefore, in the above first inequality, it is not the design value δ of the guide clearance but the magnitude δ of the guide clearance during bearing operation that is used. ０ Normally, the size of the guide clearance during bearing operation is δ ０ The guide clearance becomes smaller than the designed value δ due to expansion caused by heat and centrifugal force. This reduction (δ - δ ０) is at most about 0.5 mm under conditions where the high-speed whirl phenomenon occurs, so 0 mm < (δ - δ ０ ) < 0.5 mm. ０ = 0.22 mm, the second inequality holds.

[0039] As described above, even if large pockets 6A and small pockets 6B having different opening dimensions W are provided, depending on the relationship between the arrangement of the pockets 6 and the guide clearance Ga2, it is possible that only the pocket forming surface 7 of the small pocket 6B will come into contact with the balls 4, and that contact will not be achieved between the inner peripheral surface 3a (guiding surface Sa) of the outer ring 3 and the outer peripheral surface 5b (guided surface Sb) of the cage 5. In this case, the expected whirl suppression effect cannot be achieved. Therefore, in the rolling bearing 1 of this embodiment, when the area surrounded by lines connecting the outer edges of a scatter diagram obtained by plotting countless positions on a two-dimensional coordinate system where the cage 5 can exist without coming into contact with the raceways 2, 3 and balls 4 is defined as the "cage movable area," it is determined that this cage movable area is within the range of the size δ of the guide clearance Ga2 during bearing operation. ０ The pocket clearance Gb2 of the small pocket 6B, the design value δ of the guide clearance Ga2, and the arrangement of the large pockets 6A and small pockets 6B were devised so that the non-circular shape was circumscribed by a circle having a diameter of [mu]. Figure 5 shows the cage movable area 10 of the cage 5 in which the large pockets 6A and small pockets 6B are arranged in the manner shown in Figure 4.

[0040] The cage movable area 10 shown in FIG. 5 is the size δ of the guide clearance during bearing operation. ０1. The cage movable region 10 has a non-circular shape with a circle 11 having a diameter of 0.22 mm (=0.22 mm) as its circumscribing circle, and is in contact with the circle 11 at multiple points. The contact portions 12 of the cage movable region 10 with respect to the circle 11 are arc-shaped with a length in the circumferential direction of the circle 11, and six of these arc-shaped contact portions 12 are provided at equal intervals along the circumferential direction of the circle 11. Therefore, the cage movable region 10 of the rolling bearing 1 of this embodiment has six arc-shaped contact portions 12 with the circle 11 (circumscribing circle) and six non-contact portions 13 that are not in contact with the circle 11, arranged alternately in the circumferential direction of the circle 11. The arc-shaped contact portions 12 indicate the range in which the cage 5 contacts the guide surface Sa of the raceway ring (the inner peripheral surface 3 a of the outer ring 3), and the non-contact portions 13 indicate the range in which the pocket forming surface 7 of the cage 5 contacts the balls 4.

[0041] The cage movable range 10 indicates that the cage 5 can move freely without coming into contact with other components (the inner ring 2, the outer ring 3, and the balls 4). Therefore, if the center of the cage 5 is located within the cage movable range 10 during bearing operation, the center of the cage 5 will be subjected to centrifugal force and move to the outer edge of the cage movable range 10. When the center of the cage 5 reaches the outer edge of the cage movable range 10, the cage 5 comes into contact with the inner circumferential surface 3 a (guide surface Sa) of the outer ring 3 or the balls 4, is subjected to a frictional force in the tangential direction, and moves along the outer edge of the cage movable range 10. At this time, in the region (arcuate contact portion 12) of the outer edge of the cage movable range 10 that is in contact with the circle 11 (circumscribed circle), a frictional force F1 acts on the cage 5 due to contact with the guide surface Sa, and in the region (non-contact portion 13) that is not in contact with the circle 11, a frictional force F2 in the opposite direction to the frictional force F1 acts on the cage 5 due to contact with the balls 4. Therefore, during bearing operation, the two types of friction forces F1 and F2, which are directed in opposite directions, act alternately on the cage 5, so that one of the friction forces F1 and F2 is appropriately reduced by the other, thereby making it possible to appropriately prevent the occurrence of the high-speed whirl phenomenon.

[0042] The rolling bearing 1 of this embodiment is able to prevent the occurrence of the high-speed whirl phenomenon by providing the cage 5 with pockets 6 (large pocket 6A and small pocket 6B) consisting of two types of circular holes, one large and one small, with different opening dimensions W, and this can be achieved more easily and at lower cost than adopting the technical means described in Patent Document 1. In particular, due to the configuration of the rolling bearing 1 of this embodiment, the cage 5 (the guided surface Sb thereof) does not always come into contact with the guide surface Sa of the raceway ring, and the frequency of contact between the guide surface Sa and the guided surface Sb is reduced, so wear can be suppressed without the need to finish these surfaces to high precision.

[0043] For reference, a method for determining the position where the cage 5 can exist without contacting the balls 4, which is necessary for determining the cage movable area 10, will now be briefly described with reference to FIG.

[0044] 6 is a conceptual diagram showing a portion of the cage 5 and two balls 4 accommodated in pockets 6 of the cage 5. In the figure, the symbol O indicates the axis, the symbol C indicates the center of the cage 5, the symbol B indicates the center of the ball 4, and the symbol P indicates an arbitrary point on the pocket forming surface 7 of the cage 5. Note that the subscript (index) of the symbol B and the left-hand character of the subscript of the symbol P indicate the numbers of the ball 4 and the pocket 6 that accommodates it, and the right-hand character of the subscript of the symbol P indicates the j-th point when the pocket forming surface 7 is discretized (mesh divided).

[0045] First, the center B of ball 4 ｉ From an arbitrary point P on the pocket forming surface 7 of the pocket 6 containing the ball 4 ｉ,j The magnitude (absolute value d) of the vector pointing to the point P on the pocket forming surface 7 is compared with the radius (r) of the ball 4. If the absolute value d is greater than the radius r of the ball 4, ｉ,j If the absolute value d is equal to or smaller than the radius r of the ball 4, it is determined that the point P on the pocket forming surface 7 does not interfere with the ball 4. ｉ,j is determined to interfere with the ball 4. Thereafter, the same determination process is carried out for other points P.

[0046] In the example shown in FIG. 5, the point P on the pocket forming surface 7 of the pocket 6 containing the ball 4 having the center indicated by the symbol B1 is 1,j and point P 1,j+1 does not interfere with the ball 4, and the pocket 6 accommodating the ball 4 has a center indicated by the symbol B2. 2,j and point P 2,j+1 will interfere with the balls 4. If the relational expression f(i, j)>0 holds for all i and j when f(i, j)=d-r, then the position of the cage center C at that time can be said to be a point where the cage 5 can exist without coming into contact with the balls 4. Furthermore, if the position of the cage center C is within a circle whose center is the axis and whose diameter is the guide clearance, then it can be said that the cage 5 can exist without coming into contact with the raceways either. Therefore, a point that satisfies both of the above conditions is determined to be a point where the cage 5 can exist without coming into contact with both the balls and the raceways.

[0047] Next, the position of the cage center C and the phase of the cage are changed, and a determination operation similar to the determination operation performed in the first step is performed. Then, if there is even one phase at the selected position of the cage center C that is determined to be the above-mentioned "point on the cage movable area," the selected position of the cage center C is determined to be a "point on the cage movable area."

[0048] The rolling bearing 1 according to an embodiment of the present invention has been described above, but the embodiment of the present invention is not limited to this, and various modifications can be made within the scope that does not deviate from the gist of the present invention.

[0049] For example, the arrangement of the large pockets 6A and small pockets 6B provided in the cage 5 can be changed as appropriate, taking into consideration the ease of manufacturing the cage 5, whirl suppression ability, heat balance, etc. Figure 7 shows the cage movable area 10 of a cage 5 (a cage 5 having a total of 24 pockets 6) in which the arrangement of both pockets 6A and 6B is different from that in Figure 4, and the magnitude δ of the guide clearance during bearing operation. ０1. The cage movable area 10 is shown as a circle 11 having a diameter of 0.22 mm (=0.22 mm), and this cage movable area 10 has arc-shaped contact portions 12 that make line contact with the circle 11 and non-contact portions 13 that do not contact the circle 11, which are arranged alternately in pairs in the circumferential direction of the circle 11. Although detailed illustration is omitted, this cage movable area 10 is for a cage 5 that has alternating pairs of large pocket groups BG, each of which is made up of six large pockets 6A arranged in succession, and small pocket groups SG, each of which is made up of six small pockets 6B arranged in succession.

[0050] Here, an example of a case where the whirl suppression effect described above cannot be adequately achieved depending on the arrangement of the large pockets 6A and the small pockets 6B will be described with reference to Figure 8. Figure 8 shows the cage movable area 10 and the magnitude δ of the guide clearance during bearing operation when a cage 5 having a total of 24 pockets 6 is used, in which large pocket groups BG each consisting of two successively arranged large pockets 6A and small pocket groups SG each consisting of two successively arranged small pockets 6B are alternately provided in groups of six. ０ 1 shows a circle 11 having a diameter of 0.22 mm (=0.22 mm). As is clear from the figure, the cage movable area 10 in this case has no contact portion with the circle 11, and is not in contact with the circle 11 over the entire circumference. This means that, during bearing operation, contact between the cage 5 and the guide surface Sa of the raceway ring is not realized, and only contact between the small pockets 6B of the cage 5 and the balls 4 is realized. In this case, only one-directional friction force F2, i.e., the friction force that causes the high-speed whirl phenomenon, acts on the cage 5, and therefore the high-speed whirl phenomenon cannot be prevented.

[0051] The rolling bearing 1 described above is one in which the outer ring 3 is provided with a guide surface Sa that guides the cage 5, but the present invention is also applicable to a rolling bearing 1 in which the inner ring 2 is provided with a guide surface Sa that guides the cage 5, i.e., a rolling bearing 1 in which the guide clearance during bearing operation is constituted by a first radial clearance Ga1 between the outer peripheral surface 2a of the inner ring 2 and the inner peripheral surface 5a of the cage 5. In this case, the magnitude δ of the guide clearance during bearing operation ０ The calculation formula for δ is as follows: ０ = δ + d ｃ・(T-20)・α ｃ -d ｒ ・(T-20)・α ｒ The various parameters in this calculation formula are: δ: design value of guide clearance [mm], T: bearing temperature [℃], d ｒ : diameter of guide surface Sa (outer peripheral surface 2a of inner ring 2) [mm], d ｃ : diameter of guided surface Sb (inner peripheral surface 5a of cage 5) [mm], α ｒ : coefficient of linear expansion of (the material forming) the inner ring 2 [1 / °C], α ｃ : the linear expansion coefficient of the cage 5 [1 / °C].

[0052] Furthermore, rollers (cylindrical rollers, needle rollers, etc.) can be used instead of balls 4 as the rolling elements that make up rolling bearing 1. In other words, the present invention is applicable not only to ball bearings, but also to roller bearings such as cylindrical roller bearings and needle roller bearings.

[0053] As described above, the present invention can effectively prevent the occurrence of the high-speed whirl phenomenon in the cage 5 constituting the rolling bearing 1, and is therefore particularly suitable for use in rolling bearings used in applications where the high-speed whirl phenomenon is likely to occur. For example, when a ball bearing is used as a rolling bearing for supporting the main spindle of a machine tool or the reaction wheel of a spacecraft, the ball bearing is subjected to a relatively large axial preload during use. Specifically, the ratio of the radial load Fr to the axial load Fa (= Fr / Fa) applied during operation is often 3 or less, and in such cases, the high-speed whirl phenomenon is particularly likely to occur. This is because the more uniform the spacing between the rolling elements (balls), the more likely the high-speed whirl phenomenon is to occur. Conversely, when the radial load acting on the ball bearing is significantly greater than the axial load (for example, when the above ratio Fr / Fa exceeds 3), lead / lag occurs among the balls, resulting in uneven ball spacing, making the high-speed whirl phenomenon less likely to occur. Therefore, the present invention can be particularly suitably applied to ball bearings used in applications where the relationship Fr / Fa≦3.0 holds, such as support bearings for the main spindles of machine tools and reaction wheels of space equipment.

[0054] The rolling bearing 1 according to the present invention has been described above, but the present invention is not limited to the above-described embodiment and can be embodied in various other forms without departing from the spirit of the present invention. The scope of the present invention is defined by the claims, and further includes equivalents set forth in the claims and all modifications within the scope of the claims.

[0055] REFERENCE SIGNS LIST 1 Rolling bearing 2 Inner ring 3 Outer ring 4 Ball (rolling element) 5 Cage 6 Pocket 6A Large pocket 6B Small pocket 7 Pocket forming surface 10 Cage movable area 11 Circle 12 Contact portion 13 Non-contact portion BG Large pocket group SG Small pocket group F, F1, F2 Friction force Ga1 First radial clearance (guiding clearance) Ga2 Second radial clearance (guiding clearance) Gb Circumferential clearance Sa Guide surface Sb Guided surface W Opening dimension (pocket diameter) δ Design value of guide clearance (radial clearance) δ ０ Size of the guide clearance (radial clearance) when the bearing is in operation ε １ Large pocket clearance ε ２ Small pocket gap size

Claims

1. A rolling bearing comprising a pair of raceways arranged radially opposite to each other and rotating relative to each other via a plurality of rolling elements, and an annular cage having a plurality of pockets circumferentially spaced apart, each pocket accommodating the rolling elements individually, one of the pair of raceways having an annular guide surface, and the cage having an annular guided surface radially opposed to the guide surface, each pocket being a circular hole with a constant opening dimension along the radial direction, wherein at least one of the plurality of pockets is configured as a large pocket and the remaining pockets are configured as small pockets with opening dimensions smaller than that of the large pocket, and the design value of the radial clearance formed between the guide surface and the guided surface is δ, and the size of the radial clearance when the bearing is in operation is δ. ０ The size of the circumferential clearances formed between the large pocket forming surface and the small pocket forming surface of the cage in a neutral state and the rolling elements is defined as ε １ and ε ２ Then, ε ２ <δ ０ <ε １ and 0 mm < (δ - δ ０ ) < 0.5 mm is satisfied, and when an area surrounded by lines connecting the outer edges of a scatter diagram obtained by plotting an infinite number of positions on a two-dimensional coordinate system where the cage can exist without contacting the pair of raceways and the rolling elements is defined as the cage movable area, this cage movable area is determined to be within the range of the radial clearance δ during bearing operation. ０ A rolling bearing characterized by having a non-circular shape with a circle having a diameter of as the circumscribing circle.

2. A rolling bearing as set forth in claim 1, wherein the contact area between the cage movable area and the circumscribing circle is arc-shaped with a length in the circumscribing circle's circumferential direction, and a plurality of such arc-shaped contact areas are provided at intervals in the circumscribing circle's circumscribing direction.

3. A rolling bearing according to claim 2, wherein three or more of the arc-shaped contact portions are provided at equal intervals in the circumferential direction of the circumscribing circle.

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