AU2016100959A4

AU2016100959A4 - Rolling bearing

Info

Publication number: AU2016100959A4
Application number: AU2016100959A
Authority: AU
Inventors: Yoji Horii; Masayuki Itou; Tsuyoshi Okunaga
Original assignee: NSK Ltd
Current assignee: NSK Ltd
Priority date: 2014-01-07
Filing date: 2016-06-29
Publication date: 2016-07-28
Anticipated expiration: 2022-12-10
Also published as: JP2015129547A; DE212014000240U1; JP6307883B2; CN206072111U; WO2015104943A1

Abstract

ROLLING BEARING Abstract A rolling bearing (100) comprising: an outer ring (1); an inner ring (6); and a holder (10) that holds each of a plurality of cylindrical rollers (9) inserted between the outer ring (1) and the inner ring (6), by a plurality of pockets (14) provided at even intervals in the circumferential direction. The inner circumferential surface of the holder (10) has a notched section (15) formed therein. The bearing internal dimension ratio a, indicated by formula 1 is 1.4a<2. 1, said formula using the radial direction dimension h of the notched section (15), the inside diameter dimension D1 of the outer ring, the outside diameter dimension D 2 of the holder (10), the pitch circle diameter dm of the rolling bearing (100), the number z of cylindrical rollers (9), the outer diameter dimension Da of the cylindrical rollers (9), and the axial direction dimension L of the cylindrical rollers (9). Da7 / dm

Description

ROLLING BEARING

TECHNICAL FIELD

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

BACKGROUND

[0002] In a rolling bearing, heat is generated by rolling resistance due to rotations of a rolling element and a bearing ring, sliding resistance on a guide surface of a holder and the like, and stirring resistance of lubricant oil. The stirring resistance is resistance that is to be generated when the rolling element pushes through lubricant oil in a bearing inside. Particularly, in a rolling bearing in which oil bath lubrication is to be made, a ratio of heat generation due to the stirring resistance of the lubricant oil is large.

[0003] On the other hand, the lubricant oil has a cooling function, too. A rolling bearing in which oil lubrication for forcibly circulating the lubricant oil is to be made is cooled by heat exchange when the supplied lubricant oil passes through the bearing inside. The cooling effect is determined in accordance with a speed of the oil upon the passing of the lubricant oil through the bearing inside, an amount of supplied oil, and the like. Further, the rolling bearing in which the oil bath lubrication is to be made is cooled by the heat exchange between the supplied lubricant oil and the bearing. This cooling effect is determined in accordance with the oil flowing (circulation) in the bearing inside and an amount of the lubricant oil. In any lubrication method, the cooling effect is determined by balance with the heat generation.

[0004] Here, the heat generation of a so-called NU-type cylindrical roller bearing is considered in which flanges are provided at both axial end portions of an outer ring. Since the outer ring having the flanges is configured to store the lubricant oil therein, when a revolving rolling element passes, the rolling element should push through the lubricant oil, so that the stirring resistance increases and the heat is generated. For this reason, a method of decreasing the heat generation by not storing the lubricant oil in the bearing inside has been suggested (for example, refer to Patent Document 1).

[0005] In a cylindrical roller bearing device disclosed in Patent Document 1, radial dimensions of both axial end portions of a rotation member such as a holder, a bearing ring and the like are made to be different and a communication path configured to communicate with an oil reservoir is formed in a housing. The radial dimensions of both axial end portions of the rotation member are made to be different, so that it is possible to axially transport the lubricant oil by a size of the centrifugal force. Therefore, the heat exchange between the bearing and the lubricant oil is promoted by the axial circulation of the lubricant oil, so that it is possible to expect the cooling effect.

[0006] In Japanese Patent Application Publication No. HI 1-230178A, (Patent Document 1), a structure of the housing is complicated and becomes larger. In addition, a shape of the rotation member such as a holder, a bearing ring and the like is complex. As a result, the manufacturing cost increases and an assembling property is lowered.

[0007] There is a need to provide a rolling bearing capable of improving a cooling capability without increasing the manufacturing cost.

OBJECT OF THE INVENTION

[0008] It is an object of the present invention to substantially overcome or at least ameliorate one or more of the disadvantages of the prior art, or to at least provide a useful alternative.

SUMMARY OF THE INVENTION

[0009] The present invention at least in an aspect has following features.

[1] A rolling bearing including: an outer ring, an inner ring, and a holder configured to hold each of a plurality of rolling elements provided between the outer ring and the inner ring by a plurality of pockets provided at equal intervals in a circumferential direction, wherein an inner peripheral surface of the holder is formed with a notched portion, and wherein a bearing inside dimension ratio a, which is indicated by a formula (1), satisfies 1.4<a<2.1.

[formula 1]

CD

where h: a radial dimension of the notched portion, D1: an inner diameter dimension of the outer ring, D2: an outer diameter dimension of the holder, dm: a bearing pitch circle diameter, z: the number of the rolling elements,

Da: an outer diameter dimension of the rolling element, and L: an axial dimension of the rolling element.

[2] In the rolling bearing of [1], the rolling bearing is used under oil lubrication.

[3] In the rolling bearing of [2], the oil lubrication is selected from jet lubrication, oil-air lubrication, splash lubrication and oil bath lubrication.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 is a sectional view of a rolling bearing in accordance with a first embodiment of the present invention. FIG. 2 is a side view of the rolling bearing. FIG. 3 is a perspective view of a holder of the rolling bearing shown in FIG. 1. FIG. 4 illustrates circulation of lubricant oil in the rolling bearing shown in FIG. 1. FIG. 5 illustrates heat generation and cooling mechanisms in the rolling bearing. FIG. 6 illustrates Bernoulli’s theorem. FIG. 7 illustrates a structure of a test bearing for performing circulating oiling. FIG. 8 shows a test result. FIG. 9 shows a test result. FIG. 10 is a sectional view of a rolling bearing in accordance with a modified embodiment of the first embodiment of the present invention. FIG. 11 is a perspective view of a holder of the rolling bearing shown in FIG. 10. FIG. 12 illustrates a shape of a notched portion of a holder of a rolling bearing in accordance with a second embodiment of the present invention. FIG. 13 is a perspective view of the holder of the rolling bearing shown in FIG. 12. FIG. 14 is a side view of a rolling bearing in accordance with a third embodiment of the present invention. FIG. 15 is a perspective view of a holder of the rolling bearing shown in FIG. 14.

DETAILED DESCRIPTION OF EMBODIMENTS

[0011] (First Embodiment)

Hereinafter, a first embodiment of the rolling bearing of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a rolling bearing 100 in accordance with a first embodiment of the present invention, FIG. 2 is a side view of the rolling bearing 100, FIG. 3 is a perspective view of a holder 10 of the rolling bearing 100, and FIG. 4 illustrates circulation of lubricant oil in the rolling bearing 100.

[0012] The rolling bearing 100 has a plurality of cylindrical rollers 9 (rolling elements) between an outer ring raceway surface 2 formed on an inner peripheral surface of an outer ring 1 and an inner ring raceway surface 7 formed on an outer peripheral surface of an inner ring 6. The rolling bearing 100 is a so-called NU-type cylindrical roller bearing having flanges 3 formed at both axial end portions of the outer ring 1. The rolling bearing 100 is used under oil lubrication.

[0013] The holder 10 has a pair of circular ring parts 11, 12 arranged axially side by side, a plurality of column parts 13 configured to axially connect the pair of circular ring parts 11, 12, and a plurality of pockets 14 configured to accommodate therein the cylindrical rollers 9 one by one by the pair of circular ring parts 11, 12 and the column parts 13. In this way, the holder 10 is configured to hold each of the plurality of cylindrical rollers 9 (rolling elements) by using the plurality of pockets 14 provided at equal intervals in a circumferential direction.

[0014] An outer peripheral surface of the holder 10 is axially straight. An inner peripheral surface of the column part 13 of the holder 10 is formed with a notched portion 15. The notched portion 15 is formed to have a rectangular section.

[0015] Heat generation and cooling mechanisms in the rolling bearing 100 are described in detail with reference to FIGS. 5 and 6. As shown in FIG. 4, when the lubricant oil is introduced into the rolling bearing 100, the lubricant oil is stored in the notched portions 15 provided on the inner peripheral surface of the holder 10. The lubricant oil stored in the notched portions 15 is applied with a pressure of pushing out the lubricant oil by a centrifugal force associated with rotation of the holder 10. The pressure and the centrifugal force overcome a flow path resistance in a gap between the pockets 14 of the holder 10 and the cylindrical rollers 9, so that the lubricant oil is introduced into the pockets 14. In the pockets 14, heat is generated due to stirring resistance.

[0016] Further, the lubricant oil is enabled to pass through the pockets 14 and to flow out to the outer peripheral surface of the holder 10 and to the outer ring raceway surface 2 by the pressure and the centrifugal force. Also on the outer ring raceway surface 2, the heat is generated due to the stirring resistance. In this way, the lubricant oil having flown out to the outer peripheral surface of the holder 10 and to the outer ring raceway surface 2 pushes out the lubricant oil stored therebetween. This pressure overcomes the flow path resistance in the gap between the outer peripheral surface of the holder 10 being rotating and the inner peripheral surface of the outer ring 1, which is a stationary ring, so that the lubricant oil is discharged (flows out) to a bearing outside.

[0017] By the lubricant oil passing through the rolling bearing 100 in this way, the heat is exchanged between the rolling bearing 100 and the lubricant oil, so that the rolling bearing 100 is cooled. Also, an amount of the lubricant oil stored in the rolling bearing 100 acts on both the cooling and the stirring resistance. For this reason, an inflow amount of the lubricant oil, an amount of the lubricant oil stored in the rolling bearing 100 and an outflow amount of the lubricant oil highly influence a bearing temperature. Therefore, in order to accomplish a sufficient temperature lowering effect, a balancing between the inflow amount and the outflow amount of the lubricant oil is required.

[0018] Herein, the gap between the outer peripheral surface of the holder 10 and the inner peripheral surface of the outer ring 1 (the inner peripheral surface of the flange 3) acts as a throttle configured to adjust a discharge amount of the lubricant oil. Also, a size of the notched portion 15 of the holder 10 influences the inflow amount of the lubricant oil into the rolling bearing 100. Therefore, in the first embodiment, the bearing temperature lowering effect is improved not only by forming the notched portions 15 on the inner peripheral surface of the holder 10 but also by appropriately setting parameters of a radial dimension of the notched portion 15 (hereinafter, referred to as a notched amount), a dimension of the gap between the inner peripheral surface of the outer ring 1 and the outer peripheral surface of the holder 10 and the other bearing specifications.

[0019] First, the inflow amount of the lubricant oil is denoted as Qin, the outflow amount is denoted as Qout, and a balancing condition (Qm=Qout) between the inflow amount Qin and the outflow amount Qout is considered. The inflow amount Qm is expressed by a flow rate v of the lubricant oil by the centrifugal force and a sectional area Ain of an inlet part, as follows.

[0020] [formula 2]

[0021] The centrifugal force applied to the lubricant oil stored in the notched portions 15 is represented by the centrifugal force that is to be applied to a pitch circle diameter dm of the rolling bearing 100. The flow rate v of the lubricant oil by the centrifugal force is expressed by an energy formula using the pitch circle diameter dm of the rolling bearing 100, a revolution speed ω of the holder 10, a notched amount h of the notched portion 15 and mass m of the lubricant oil, as follows.

[0022] [formula 3]

[0023] [formula 4]

[0024] Also, the sectional area Ain of the inlet part can be expressed by an outer diameter dimension Da of the cylindrical roller 9, a length (axial dimension) L of the cylindrical roller 9 and the number z of the cylindrical rollers 9, as follows.

[0025] [formula 5]

[0026] Herein, when the length L of the cylindrical roller 9 is the same as a length (axial dimension) Lp of the pocket 14 (L=Lp), the sectional area Sin of the notched portion 15, the notched amount h and the length L of the cylindrical roller 9 satisfy a following formula.

[0027] [formula 6]

[0028] The outflow amount Qout is limited by a throttling effect due to the gap between the outer peripheral surface of the holder 10 and the inner peripheral surface of the outer ring 1 and resistance due to the rotation. Therefore, the outflow amount Qout is expressed by a sectional area Sout of an outlet part, a head (liquid level height) H of the lubricant oil (refer to FIG. 6), an oil drain resistance R and a coefficient B, as follows.

[0029] [formula 7]

[0030] Also, the sectional area Sout of the outlet part can be expressed by an inner diameter (an inner diameter of the flange 3) Di of the outer ring 1, an outer diameter D2 of the holder 10 and the pitch circle diameter dm of the rolling bearing 100, as follows.

[0031] [formula 8]

[0032] Also, the oil drain resistance R can be expressed, as follows.

[0033] [formula 9]

[0034] Herein, as described above, in order to accomplish the sufficient temperature lowering effect, the balancing between the inflow amount Qin and the outflow amount Qout is required (Qin=Qout)· Therefore, the above formulas can be modified as follows.

[0035] [formula 10]

[0036] The above formula can be modified using the head H, as follows.

[0037] [formula 11]

[0038] In the first embodiment, as a representative of the size effect of the rolling bearing 100, the head H is divided by the pitch circle diameter dm of the rolling bearing 100, and a resultant value is set as a bearing inside dimension ratio a.

[0039] [formula 12]

[0040] (Tests) A test structure shown in FIG. 7 was used, the rolling bearing 100 was inserted into a shaft S, and a rotation test was then performed. The rotation test was performed by changing the bearing inside dimension ratio a of the rolling bearing 100 and using the two numbers of rotations n, m. FIG. 8 is a graph depicting a result of the rotation test, showing a relation between the bearing inside dimension ratio a and the temperature lowering effect in the rolling bearing 100. From FIG. 8, it can be seen that even though the number of rotations is changed to n and m, when the bearing inside dimension ratio a satisfies a relation of 1.4<a<2.1, the sufficient temperature lowering effect is accomplished.

[0041] Also, for comparison, a rolling bearing (conventional specification) of the related art where a holder is not formed with a notched portion or a taper and a rolling bearing (taper specification) where radial dimensions of both axial end portions of a holder are different, as disclosed in Patent Document 1, were prepared and the rotation test was performed. FIG. 9 is a graph depicting a result of the rotation test. From FIG. 9, according to the rolling bearing of the present specification where the inner peripheral surface of the holder 10 is formed with the notched portions 15 and the bearing inside dimension ratio a satisfies the relation of 1.4<a<2.1, it can be seen that the temperature lowering effect is clearly accomplished, as compared to the conventional specification and the taper specification.

[0042] As described above, according to the rolling bearing 100 of the first embodiment, the inner peripheral surface of the holder 10 is formed with the notched portions 15 and the bearing inside dimension ratio a satisfies the relation of 1 4<α<2.1, so that the lubricant oil does not stay in the rolling bearing 100. As a result, it is possible to obtain the efficient cooling effect without increasing the manufacturing cost. Thereby, even when the oil lubrication, particularly, the oil bath lubrication is used, it is possible to secure the cooling capability equivalent to the jet lubrication and to obtain the sufficient temperature lowering effect. Further, the rolling bearing 100 can accomplish the sufficient temperature lowering effect even when it is used under jet lubrication, oil-air lubrication or splash lubrication.

[0043] (Modified Embodiment) FIGS. 10 and 11 depict a rolling bearing 100' in accordance with a modified embodiment of the first embodiment and a holder 10' that is to be used for the rolling bearing 100'. An inner peripheral surface of the holder 10' is also formed with the notched portions 15 having a rectangular section. Moreover, both axial end portions of the holder 10', i.e., the outer peripheral surfaces of the circular ring parts 11, 12 are formed with annular notched portions 16, 17 notched in correspondence to the flanges 3 of the outer ring 1. Even when the outer peripheral surface of the holder 10' has such a shape, the temperature lowering effect can be accomplished inasmuch as the bearing inside dimension ratio a satisfies the above relation (1.4<a<2.1).

[0044] (Second Embodiment)

Subsequently, a rolling bearing in accordance with a second embodiment of the present invention is described with reference to FIGS. 12 and 13. The same or equivalent parts as or to the first embodiment are denoted with the same or equivalent reference numerals, and the descriptions thereof are simplified or omitted.

[0045] As shown in FIGS. 12 and 13, in a rolling bearing 200 of the second embodiment, inner peripheral surfaces of column parts 213 of a holder 210 are formed with notched portions 215. The notched portion 215 is formed to have an arc section, unlike the notched portion 15 of the first embodiment.

[0046] Also in the notched portion 215 formed to have an arc section, if a sectional area Sm thereof can be equivalently replaced with the sectional area Sin of the notched portion 15 of the first embodiment, it is thought that the temperature lowering effect can be accomplished inasmuch as the bearing inside dimension ratio a satisfies the above relation (1.4<a<2.1), like the first embodiment.

[0047] Herein, when the sectional area of one notched portion corresponding to one pocket is denoted as Sm, a total sum ESm of the sectional areas of the notched portions is expressed by a notched amount h of the notched portion 215, a notch length (axial dimension) M of the notched portion 215 (refer to FIG. 12) and the number of the cylindrical rollers 9 (the number of the pockets) z, as follows.

[0048] [formula 13]

[0049] Therefore, in order to make the sectional areas of the notched portions equivalent, which are formed on the inner peripheral surface of the holder, the notched amount h preferably satisfies a following formula.

[0050] [formula 14]

[0051] In this way, even when the notched portion 215 is formed to have an arc section, the sufficient temperature lowering effect can be accomplished inasmuch as the total sum ZSm of the sectional areas of the notched portions is equivalently replaced and the bearing inside dimension ratio a satisfies the above relation (1.4<a<2.1).

[0052] (Third Embodiment)

Subsequently, a rolling bearing in accordance with a third embodiment of the present invention is described with reference to FIGS. 14 and 15. The same or equivalent parts as or to the first embodiment are denoted with the same or equivalent reference numerals, and the descriptions thereof are simplified or omitted.

[0053] As shown in FIGS. 14 and 15, in a rolling bearing 300 of the third embodiment, outer peripheral surfaces of circular ring parts 311, 312 of a holder 310 are formed with arc-shaped recess portions 316 at locations axially adjacent to pockets 314. For this reason, an outlet part of the rolling bearing 300 through which the lubricant oil is to be discharged has a non-uniform section on a circumference.

[0054] Herein, when the outlet part has a uniform section on a circumference, a sectional area S0ut of the outlet part can be expressed by the inner diameter (the inner diameter of the flange 3) Di of the outer ring 1 and the outer diameter D2 of the holder 310, as follows.

[0055] [formula 15]

[0056] When the outlet part has a non-uniform section on a circumference, a difference (D1-D2) between the inner diameter Di of the outer ring 1 and the outer diameter D2 of the holder 310, which are parameters of the sectional area Sout of the outlet part, can be equivalently replaced, as follows.

[0057] [formula 16]

[0058] Like this, even when the outlet part has a non-uniform section on a circumference, the sufficient temperature lowering effect can be accomplished inasmuch as the sectional area Sout of the outlet part is equivalently replaced and the bearing inside dimension ratio a satisfies the above relation.

[0059] In the meantime, the present invention is not limited to the above embodiments, and can be appropriately modified and improved. In the above embodiments, the rolling bearing is the cylindrical roller bearing but may be the other rolling bearing. Also, the sectional shape of the notched portion formed on the inner peripheral surface of the holder is not limited to the rectangular shape described in the first embodiment and the arc shape described in the second embodiment, and may be an arbitrary shape inasmuch as the sectional area of the notched portion can be equivalently replaced.

[0060] Also, in the above embodiments, the column parts are formed with the notched portions in correspondence to all the pockets. However, the column parts may be formed with the notched portions in correspondence to only some pockets inasmuch as the total sum ESm of the sectional areas of the notched portions can be equivalently replaced with the notched amount h.

Also, the recess portions that can be formed on the outer peripheral surface of the holder may be formed in correspondence to only some pockets.

[0061] The subject application is based on a Japanese Patent Application No. 2014-001139 filed on January 7, 2014, which is herein incorporated for reference.

Description of Reference Numerals [0062] 100, 100', 200, 300: rolling bearing 1: outer ring 6: inner ring 9: cylindrical roller (rolling element) 10, 10', 210, 310: holder 15, 215, 315: notched portion Z: number of cylindrical rollers 19 L: length (axial dimension) of cylindrical roller

Da: outer diameter dimension of cylindrical roller dm: bearing pitch circle diameter

Dl: inner diameter dimension of outer ring D2: outer diameter dimension of holder h: notched amount (radial dimension of notched portion).

Claims

1. A rolling bearing comprising: an outer ring, an inner ring, and a holder configured to hold each of a plurality of rolling elements provided between the outer ring and the inner ring by a plurality of pockets provided at equal intervals in a circumferential direction, wherein an inner peripheral surface of the holder is formed with a notched portion, and wherein a bearing inside dimension ratio a, which is indicated by a formula (1), satisfies 1.4<a<2.1. [formula 1]

(I) where h: a radial dimension of the notched portion, D1: an inner diameter dimension of the outer ring, D2: an outer diameter dimension of the holder, dm: a bearing pitch circle diameter, z: the number of the rolling elements, Da: an outer diameter dimension of the rolling element, and L: an axial dimension of the rolling element.

2. The rolling bearing according to claim 1, the rolling bearing is used under oil lubrication.

3. The rolling bearing according to claim 2, the oil lubrication is selected from jet lubrication, oil-air lubrication, splash lubrication and oil bath lubrication.