Abrasion prevention structure for bearing

Abstract

To provide an abrasion prevention structure for a bearing that can reduce abrasion of a holder by reducing the weight of a roller of the bearing.SOLUTION: An abrasion prevention structure 14 prevents abrasion of a holder 12 which holds a rolling element 13 of a bearing. The rolling element 13 includes a closing part 16 which closes a hollow part 15a of a cylinder part 15 of the rolling element 13, and the closing part 16 has a smaller weight than that of the cylinder part 15. A ratio of an inner diameter φ2 of the cylinder part 15 to its outer diameter φ1 is 60% or more to 90% or less. The closing part 16 is a lightweight member that closes the whole or a part of the hollow part 15a of the cylinder part 15. The closing part 16 is made of a resin material or a porous material. The bearing is a rolling bearing that rotationally supports a rotor shaft 6 of a main motor.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a wear prevention structure for a bearing that prevents wear of a cage that holds rollers in the bearing. [Background technology]

[0002] For example, rolling bearings used under light loads and at high rotational speeds, such as cylindrical roller bearings used in traction motors for railway vehicles, can experience cage wear, which can cause bearing temperatures to rise and lead to seizure.To solve this problem, there are cases where the cage is made lighter or its structure is changed.

[0003] In a cylindrical roller bearing (hereinafter referred to as Prior Art 1), the inner diameter opening dimension of a pocket formed by adjacent column portions and a pair of annular portions of an one-piece machined cage is smaller than the outer diameter opening dimension of this pocket, and is also smaller than the width of this pocket at the pitch circle diameter position (see, for example, Patent Document 1). In Prior Art 1, the weight of the cage is reduced, and in the non-load zone of the cylindrical roller bearing, the pocket supports the cylindrical rollers at the outer diameter side edge, thereby suppressing the progression of cage wear.

[0004] In a conventional rolling bearing (hereinafter referred to as Prior Art 2), the surface that forms the multiple pockets of the cage that holds the multiple rolling elements is crowned to form a convex curved surface relative to the rolling elements (see, for example, Patent Document 2). In Prior Art 2, by changing the shape of the cage, even if the cylindrical rollers are skewed, the contact pressure between the axial end faces or chamfered portions of the cylindrical rollers and the axial side faces is prevented from concentrating and becoming excessive.

[0005] In a conventional cylindrical roller bearing (hereinafter referred to as Prior Art 3), the circumferential side surface of the column portion of the cage is formed into an arcuate surface that follows the rolling surfaces of the cylindrical rollers, and is equipped with a guide portion that guides the rolling surface when the column portion elastically deforms toward the outer diameter due to centrifugal force, and a relief portion that does not generate contact pressure in the radial direction with the rolling surfaces of the cylindrical rollers when the column portion elastically deforms toward the outer diameter due to centrifugal force (see, for example, Patent Document 3). In Prior Art 3, the guide portion guides the rolling surfaces of the cylindrical rollers when the column portion elastically deforms, reducing non-repetitive runout during high-speed rotation and resulting in light contact between the contact surfaces of the cylindrical rollers and the relief portion, preventing abnormal wear. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-070346

[0007] [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-079706

[0008] [Patent Document 3] Japanese Patent Application Laid-Open No. 2005-127493 Summary of the Invention [Problem to be solved by the invention]

[0009] Generally, rolling bearings become unusable due to flaking on the raceway surface, but bearings like the cylindrical roller bearings mentioned above, which support extremely low loads relative to the load (basic dynamic load rating) that is applied to the bearing in a constant direction and magnitude, and which are operated at high rotational speeds, become unusable in a relatively short period of time due to cage wear. Prior arts 1 to 3 all require a change to the cage, which requires a redesign, raising concerns that this could affect the cage strength. Furthermore, in rolling bearings used under light loads, the narrow load zone is one factor that accelerates cage wear (since the rollers repeatedly collide with the cage in the non-load zone, a narrow non-load zone (wide load zone) is advantageous), but prior arts 1 to 3 do not allow the load zone to be widened.

[0010] An object of the present invention is to provide a wear prevention structure for a bearing that can reduce wear on the cage by reducing the weight of the rollers of the bearing. [Means for solving the problem]

[0011] The present invention solves the above problems by the means described below. Although the description will be given with reference numerals corresponding to the embodiments of the present invention, the present invention is not limited to these embodiments. The invention of claim 1 is a bearing wear prevention structure (14) that prevents wear of a retainer (12) that holds rollers (13) of a bearing (9), as shown in Figures 2 to 8, wherein the rollers have a blocking portion (16) that blocks a hollow portion (15a) of a cylindrical portion (15) of the roller, and the blocking portion is lighter than the cylindrical portion.

[0012] The invention of claim 2 is a wear prevention structure for a bearing described in claim 1, characterized in that the ratio of the inner diameter (φ1) to the outer diameter (φ2) of the cylindrical portion is 60% or more and 90% or less.

[0013] The invention of claim 3 is a wear prevention structure for a bearing according to claim 1, characterized in that the blocking portion is a lightweight member that blocks all or part of the hollow portion of the cylindrical portion, as shown in Figures 4 to 8.

[0014] The invention of claim 4 is a wear prevention structure for a bearing according to claim 1, characterized in that the blocking portion is made of a resin material or a porous material, as shown in Figures 4 to 8.

[0015] The invention of claim 5 is a wear prevention structure for a bearing according to claim 1, characterized in that the blocking portion is a porous material impregnated with a lubricant (M), as shown in FIG.

[0016] The invention of claim 6 is a wear prevention structure for a bearing according to claim 1, characterized in that, as shown in FIG. 8, the blocking portion is a porous material that blocks the hollow portion of the cylindrical portion in which the lubricant (M) is contained.

[0017] The invention of claim 7 is a wear prevention structure for a bearing according to claim 1, characterized in that, as shown in FIG. 1, the bearing is a roller bearing that rotatably supports the rotor shaft (6) of an electric motor (4). [Effects of the Invention]

[0018] According to the present invention, the weight of the rollers in the bearing can be reduced, thereby reducing the wear on the cage. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a schematic diagram showing an example in which a bearing equipped with a wear prevention structure for a bearing according to a first embodiment of the present invention is applied to a driving device for a railway vehicle. [Figure 2] 1A and 1B are schematic diagrams of a bearing equipped with a wear prevention structure for a bearing according to a first embodiment of the present invention, in which (A) is a front view and (B) is a longitudinal cross-sectional view showing an enlarged view of part IIB of (A). [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. [Figure 4] 1A and 1B are external views of a bearing equipped with a wear prevention structure for a bearing according to a first embodiment of the present invention, where (A) is a front view, (B) is a side view, (C) is a cross-sectional view taken along line IV-IVC in (A), and (D) is a cross-sectional view taken along line IV-IVD in (B). [Figure 5] 10A and 10B are external views of a bearing equipped with a wear prevention structure for a bearing according to a second embodiment of the present invention, where (A) is a front view, (B) is a side view, (C) is a cross-sectional view taken along line V-VC in (A), and (D) is a cross-sectional view taken along line V-VD in (B). [Figure 6] 6A and 6B are external views of a bearing equipped with a wear prevention structure for a bearing according to a third embodiment of the present invention, where (A) is a front view, (B) is a side view, (C) is a cross-sectional view taken along line VI-VIC in (A), and (D) is a cross-sectional view taken along line VI-VID in (B). [Figure 7] 7A and 7B are external views of a bearing equipped with a wear prevention structure for a bearing according to a fourth embodiment of the present invention, in which (A) is a front view, (B) is a side view, (C) is a cross-sectional view taken along line VII-VIIC in (A), and (D) is a cross-sectional view taken along line VII-VIID in (B). [Figure 8] 8A and 8B are external views of a bearing equipped with a wear prevention structure for a bearing according to a fifth embodiment of the present invention, in which (A) is a front view, (B) is a side view, (C) is a cross-sectional view taken along line VIII-VIIIC in (A), and (D) is a cross-sectional view taken along line VIII-VIIID in (B). [Figure 9] 1 is a photograph showing an example of a rolling element of a bearing equipped with a wear prevention structure for a bearing according to an embodiment of the present invention. [Figure 10] 10 is a graph showing, as an example, the results of an analysis of the change in width of the load zone when the inner diameter of the rolling elements of a bearing equipped with a wear prevention structure for a bearing according to an embodiment of the present invention is changed. [Figure 11] 6 is a graph showing the results of a life test of a bearing equipped with a wear prevention structure for a bearing according to an embodiment of the present invention. [Figure 12]1 is a graph showing, as an example, the results of trial calculations of the life extension effect of the wear prevention structure of the bearing according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] (First embodiment) A first embodiment of the present invention will be described in detail below with reference to the drawings. The track 1 shown in Figure 1 is a track (passageway) on which a vehicle 2 travels. The track 1 is equipped with left and right rails 1a that support and guide left and right wheels 3a of the vehicle 2, allowing the vehicle 2 to travel. The vehicle 2 is a moving object that travels along the track 1. The vehicle 2 is, for example, a railway vehicle such as a train or an electric locomotive. The wheel set 3 is a member assembled from a wheel 3a and an axle 3b. The wheel 3a is a member that comes into rolling contact with the rail 1a. The axle 3b is a member that rotates integrally with the wheel 3a. A pair of left and right wheels 3a are press-fitted and attached to both ends of the axle 3b.

[0021] The traction motor 4 is a prime mover that generates power to run the rolling stock 2. The traction motor 4 is an electric device (motor) that uses, as driving force, an electromagnetic force generated by the interaction of a magnetic field and an electric current, and is attached to the bogie frame of the bogie. The traction motor 4 includes a stator (main pole) 4a supported by a frame body 5, and a rotor (armature) 4b that generates an electromagnetic force between itself and the stator 4a. The frame body (housing) 5 is a member that houses and supports the traction motor 4. The rotor shaft (armature shaft) 6 is a member to which the rotor 4b of the traction motor 4 is attached and which rotates integrally with the rotor 4b. The drive unit 7 is a device that transmits the rotational force of the traction motor 4 to the axle 3b. The drive unit 7 includes a cardan shaft 7a that rotates integrally with the rotor shaft 6, a universal joint 7b that rotatably connects the rotor shaft 6 and the cardan shaft 7a, a pinion gear 7c attached to the cardan shaft 7a, and a large gear 7d that is attached to the axle 3b and meshes with the pinion gear 7c. The drive unit 7 reduces the driving force of the main motor 4 by a reduction gear device consisting of the pinion gear 7c and the large gear 7d, and transmits it to the axle 3b via the rotor shaft 6, cardan shaft 7a, and universal joint 7b. The bearing 8 is a rolling bearing that rotatably supports the rotor shaft 6. The bearing 8 supports the rotor shaft 6 by the rolling motion of the rolling elements, and is a ball bearing that uses balls as the rolling elements.

[0022] The bearing 9 shown in Figures 1 to 3 is a rolling bearing that rotatably supports the rotor shaft 6. The bearing 9 supports the rotor shaft 6 by the rolling motion of the rolling elements and is a roller bearing that uses rollers as the rolling elements. The bearing 9 shown in Figures 1 to 3 is a cylindrical roller bearing that uses cylindrical rollers as the rolling elements. The bearing 9 comprises an outer ring 10, an inner ring 11, a cage 12, and rolling elements 13. The outer ring 10 is an outer cylindrical member with which the rolling elements 13 come into contact. The outer ring 10 has raceway surfaces 10a that are the paths along which the rolling elements 13 roll. The inner ring 11 is an inner cylindrical member with which the rolling elements 13 come into contact. The inner ring 11 has raceway surfaces 11a that are the paths along which the rolling elements 13 roll. The cage 12 is a member that holds the rolling elements 13. The cage 12 holds the rolling elements 13 at equal intervals.

[0023] 2 to 4 is a member that rolls between the outer ring 10 and the inner ring 11. The rolling element 13 is manufactured, for example, through a process that includes forming bearing steel into a cylindrical shape, removing burrs by rough grinding, a heat treatment process, a grinding process, and a lapping process, in that order. As shown in FIGS. 3 and 4, the rolling element 13 includes a wear prevention structure 14, a cylindrical portion 15, and a closing portion 16.

[0024] The wear prevention structure 14 is a structure that prevents wear of the cage 12 of the bearing 9. By reducing the weight and rigidity of the rolling elements 13, the wear prevention structure 14 widens the loaded zone and narrows the unloaded zone shown in Fig. 2(A) and reduces the impulse generated by contact between the cage 12 and the rolling elements 13 shown in Fig. 2(B), thereby reducing wear of the cage 12. Here, the impulse is the product of the contact force and contact time between the cage 12 and the rolling elements 13, as shown in Fig. 2(B).

[0025] The cylindrical portion 15 constitutes the main body of the rolling element 13. Like the outer ring 10 and the inner ring 11, the cylindrical portion 15 is made of, for example, high-carbon chromium bearing steel, case-hardened steel (carburizing steel), heat-resistant bearing steel, corrosion-resistant bearing steel, induction-hardened steel, or ceramic material. The cylindrical portion 15 is formed into a hollow roller by machining, such as boring, to further enlarge the diameter of a through hole drilled in a solid roller of a cylindrical roller bearing. The cylindrical portion 15 has a hollow portion 15a inside. The cylindrical portion 15 is an outer component that constitutes the outer portion of the rolling element 13. The hollow structure reduces weight and rigidity, widens the loaded area and narrows the unloaded area shown in FIG. 2(A), and reduces wear on the cage 12. As shown in Fig. 4(C), the cylindrical portion 15 has a cross-sectional shape that is circular, and is formed so as to have a uniform thickness from one end to the other end with a predetermined inner diameter φ1 and outer diameter φ2 as shown in Fig. 4(D). If the ratio of the inner diameter φ1 to the outer diameter φ2 of the cylindrical portion 15 is less than 60%, the degree of weight reduction and the effect of extending the lifespan will be reduced, and if it exceeds 90%, problems will arise in terms of strength, so it is preferable to set the ratio between 60% and 90%.

[0026] The blocking portion 16 is a portion that blocks the hollow portion 15a of the cylindrical portion 15 of the rolling element 13. The blocking portion 16 is a lightweight member that is lighter than the cylindrical portion 15 and completely blocks the hollow portion 15a of the cylindrical portion 15. The outer periphery of the blocking portion 16 is fitted into the inner periphery of the cylindrical portion 15. The blocking portion 16 is an internal component that forms the inner portion of the rolling element 13 and fills the entire hollow portion 15a of the cylindrical portion 15 as shown in FIG. 4(D). The blocking portion 16 is a cylindrical member as shown in FIGS. 4(C) and (D) and is formed to the same length as the length L of the cylindrical portion 15 as shown in FIGS. 4(A) and (D). The blocking portion 16 is made of a resin material such as engineering plastic that has excellent mechanical strength and heat resistance. As shown in Figure 4(D), the outer periphery of blocking portion 16 is fixed to the inner periphery of tubular portion 15 with an adhesive or the like so that both ends of blocking portion 16 are at the same height (flush) as both ends of tubular portion 15.

[0027] Next, the operation of the wear prevention structure for the bearing according to the first embodiment of the present invention will be described. When the rotor shaft 6 of the traction motor 4 shown in FIG. 1 rotates, the rolling elements 13 of the bearing 9 shown in FIG. 2(A) rotate on their own axes while revolving between the outer ring 10 and the inner ring 11. As shown in FIG. 2(B), when the bearing 9 receives a load from the rotor shaft 6, this load is borne in a loaded zone, which is a partial area of ​​the raceway surface 10a of the outer ring 10. In the loaded zone, the rolling elements 13 are constrained between the outer ring 10 and the inner ring 11, so collisions between the rolling elements 13 and the cage 12 are reduced, and the wider the loaded zone, the more wear on the cage 12 is prevented. On the other hand, if the loaded zone in which the rolling elements 13 receive a load from the rotor shaft 6 shown in FIG. 2(A) is narrow and the non-loaded zone in which the rolling elements 13 do not receive a load from the rotor shaft 6 is wide, the impulse in the non-loaded zone becomes large, as shown in FIG. 2(B). Therefore, as shown in FIG. 2(B), the rolling elements 13 repeatedly collide with the cage 12 in the non-load zone, accelerating wear of the cage 12.

[0028] The traction motor 4 of a railway vehicle as shown in FIG. 1 is relatively small and lightweight, and the load that the rolling elements 13 receive from the rotor shaft 6 is relatively small. As a result, the loaded zone shown in FIG. 2(A) is relatively narrow, and the non-loaded zone is relatively wide. In this embodiment, a hollow portion 15a is formed inside the rolling elements 13, and a lightweight blocking portion 16 is fitted inside the hollow portion 15a. If the rolling elements 13 are hollow and have low rigidity, they will be more likely to elastically deform when subjected to a load in the loaded zone, and the amount of displacement of the inner ring 11 relative to the outer ring 10 will increase, so that more rolling elements 13 will support the load. As a result, the rolling elements 13 will be lighter and have lower rigidity, resulting in a relatively wide loaded zone and a relatively narrow non-loaded zone. As a result, as shown in Figure 2(B), even if the rolling elements 13 repeatedly collide with the retainer 12 in a relatively narrow non-load zone, the sum of the impulses between the retainer 12 and the rolling elements 13 in the non-load zone is reduced, and wear of the retainer 12 is suppressed.

[0029] The wear prevention structure for a bearing according to the first embodiment of the present invention has the following effects. (1) In this first embodiment, the hollow portion 15a of the cylindrical portion 15 of the rolling element 13 is blocked by the blocking portion 16, and the blocking portion 16 is lighter than the cylindrical portion 15. Therefore, by incorporating low-rigidity hollow rollers into the bearing 9, the loaded zone can be widened and the non-loaded zone can be narrowed. As a result, even if the rolling element 13 repeatedly collides with the cage 12 in the non-loaded zone, the lightweight hollow rollers incorporated into the bearing 9 can reduce the impulse in the non-loaded zone, thereby reducing wear of the cage 12. Furthermore, by changing the rollers of the cylindrical roller bearing from solid to hollow, wear of the cage 12 can be reduced without changing the design of the cage 12. Furthermore, by inserting the lightweight blocking portion 16 into the cylindrical portion 15, it is possible to prevent grease and the like from entering the hollow portion 15a of the cylindrical portion 15.

[0030] (2) In the first embodiment, the ratio of the inner diameter φ1 of the cylindrical portion 15 to the outer diameter φ2 is 60% or more and 90% or less. Therefore, the life of the bearing 9 can be extended by reducing the weight as much as possible while maintaining sufficient mechanical strength of the rolling elements 13.

[0031] (3) In the first embodiment, the closing portion 16 that completely closes the hollow portion 15a of the cylindrical portion 15 is made of a lightweight member. Therefore, by configuring the rolling elements 13 as lightweight, low-rigidity hollow rollers and incorporating them into the bearing 9, it is possible to reduce the impulse in the non-load zone.

[0032] (4) In the first embodiment, the blocking portion 16 is made of a resin material. Therefore, for example, by forming the blocking portion 16 from a synthetic resin such as engineering plastic, the weight of the rolling elements 13 can be reduced and wear of the cage 12 can be reduced.

[0033] (5) In this first embodiment, the bearing 9 that rotatably supports the rotor shaft 6 of the traction motor 4 is a roller bearing. For example, in the case of a bearing for a traction motor of a railway vehicle, the load that the rolling elements 13 receive from the rotor shaft 6 is relatively small. However, because the rotor shaft 6 rotates at a relatively high speed, unlike a bearing in which the rolling elements receive a relatively large load, damage to the cage is more severe than damage to the rolling surfaces. In this embodiment, the rolling elements 13 have a hollow structure, reducing their rigidity and achieving weight reduction. As a result, the loaded area is relatively narrow and the unloaded area is relatively wide, so that wear on the cage 12 can be suppressed even if the rolling elements 13 repeatedly collide with the cage 12 in the unloaded area.

[0034] (Second embodiment) In the following, the same parts as those shown in FIGS. 1 to 5 are denoted by the same reference numerals and detailed description thereof will be omitted. The cylindrical portion 15 shown in Fig. 5 has mounting portions 15b to which the blocking portion 16 is attached. As shown in Fig. 5(D), the mounting portions 15b are recesses formed at both ends of the cylindrical portion 15. The mounting portions 15b are formed to a depth D that is slightly larger than the thickness of the blocking portion 16, and to an inner diameter φ3 that is larger than the inner diameter φ1 of the cylindrical portion 15. The mounting portions 15b are formed by machining, such as countersinking, to prevent the blocking portion 16 from protruding from both ends of the cylindrical portion 15 when the blocking portion 16 is attached.

[0035] The blocking portion 16 is a lightweight member that blocks a portion of the hollow portion 15a of the tubular portion 15. As shown in FIGS. 5(A) and 5(C), the blocking portion 16 is a disc-shaped member made of a resin material such as engineering plastic. As shown in FIG. 5(D), the blocking portion 16 blocks both ends of the tubular portion 15 so that the interior of the tubular portion 15 is hollow, and fills a portion of the hollow portion 15a of the tubular portion 15. The outer periphery of the blocking portion 16 is fixed to the mounting portion 15b of the tubular portion 15 with an adhesive or the like so that the surface of the blocking portion 16 is at the same height (flush) as both ends of the tubular portion 15.

[0036] The wear prevention structure for a bearing according to the second embodiment of the present invention has the following advantages in addition to the advantages of the first embodiment. In the second embodiment, the closing portion 16 that closes a part of the hollow portion 15a of the cylindrical portion 15 is made of a lightweight material. Therefore, the rolling elements 13 can be made even lighter than in the first embodiment, and wear of the cage 12 can be further reduced.

[0037] (Third embodiment) The blocking portion 16 shown in FIG. 6 is a lightweight member that completely blocks the hollow portion 15a of the tubular portion 15, as shown in FIG. 6(D). The blocking portion 16 is a cylindrical member as shown in FIGS. 6(B) to 6(D), and is formed to have the same length as the length L of the tubular portion 15 as shown in FIG. 4(D). The blocking portion 16 is made of, for example, a metal material such as aluminum, a resin material such as polyurethane, or a natural polymer material such as natural rubber. As shown in FIGS. 6(B) to 6(D), the blocking portion 16 has a three-dimensional skeletal network structure similar to that of a porous material with isolated pores, in which the pores are isolated and not connected to each other. The blocking portion 16 is manufactured, for example, by foam molding a synthetic resin such as polyurethane, kneading a foaming agent and a softener into rubber and vulcanizing it, or sintering and molding metal powder such as foamed aluminum. 6(D), the outer periphery of the blocking portion 16 is fixed to the inner periphery of the cylindrical portion 15 with an adhesive or the like so that both ends of the blocking portion 16 are at the same height (flush) as both ends of the cylindrical portion 15. The third embodiment has the same effects as the first and second embodiments.

[0038] (Fourth embodiment) The blocking portion 16 shown in FIG. 7 is a lightweight member that blocks the entire hollow portion 15a of the tubular portion 15, similar to the blocking portion 16 shown in FIG. 6. The blocking portion 16 is a cylindrical member as shown in FIGS. 7(B) to 7(D) and is made of a metal material, a resin material, a natural polymer material, or the like, and is formed to the same length as the length L of the tubular portion 15 as shown in FIG. 7(D). Unlike the blocking portion 16 shown in FIG. 6, the blocking portion 16 is made of a porous material impregnated with a lubricant M as shown in FIGS. 7(B) to 7(D). The blocking portion 16 has a three-dimensional skeletal network structure similar to that of a porous material with interconnected pores, with minute pores formed in the walls between the pores. As shown in FIG. 7(D), the outer periphery of the blocking portion 16 is fixed to the inner periphery of the tubular portion 15 with an adhesive or the like so that both ends of the blocking portion 16 are at the same height (flush) with both ends of the tubular portion 15.

[0039] 7(B) to 7(D) is a substance used to lubricate the bearing 9. The lubricant M is, for example, grease, which is a semi-solid lubricant made by dispersing a thickener, which is a fine solid, in a base oil and adding an additive, or a lubricant oil used to reduce friction acting between the components that make up the bearing 9.

[0040] The wear prevention structure for a bearing according to the fourth embodiment of the present invention has the same effects as the first to third embodiments. In the third embodiment, the blocking portion 16 is a porous material impregnated with the lubricant M. This reduces the weight of the rolling elements 13, thereby reducing the wear of the cage 12. Furthermore, the lubricant M impregnated in the porous material can be supplied from this porous material to the bearing 9 while the bearing 9 is in use, thereby lubricating the bearing 9.

[0041] (Fifth embodiment) The cylindrical portion 15 shown in FIG. 8 has a hollow portion 15a into which lubricant M is accommodated. As shown in FIGS. 8(A) to 8(D), the blocking portion 16 is a porous material that blocks the hollow portion 15a of the cylindrical portion 15 in which the lubricant M is accommodated. Similar to the blocking portion 16 shown in FIG. 5, the blocking portion 16 shown in FIG. 8 is a lightweight member that blocks a portion of the hollow portion 15a of the cylindrical portion 15. Similar to the blocking portion 16 shown in FIG. 7, the blocking portion 16 shown in FIG. 8 has a three-dimensional skeletal network structure such as a porous material with continuous pores. The blocking portion 16 shown in FIG. 8 blocks both ends of the cylindrical portion 15 so that the lubricant M seeps out from the inside of the hollow portion 15a to the outside. The lubricant M is filled into the hollow portion 15a from the outside of the blocking portion 16 through the blocking portion 16.

[0042] The wear prevention structure for a bearing according to the fifth embodiment of the present invention has the following effects in addition to the effects of the first to fourth embodiments. In the fifth embodiment, the closing portion 16 that closes the hollow portion 15a of the cylindrical portion 15 in which the lubricant M is accommodated is made of a porous material. Therefore, while the bearing 9 is being used, the lubricant M seeps out from the inside of the hollow portion 15a to the outside, and the bearing 9 can be lubricated by the lubricant M. [Example]

[0043] Next, an embodiment of the present invention will be described. Figure 9 is a photograph showing an example of the appearance of a hollow roller corresponding to the cylindrical portion 15 shown in Figures 3 to 7. The hollow roller shown in Figure 9 is in a state before the closing portion 16 shown in Figures 3 to 7 is inserted. By forming a hollow roller with a through hole with an inner diameter of φ9 mm in comparison with a solid roller with an outer diameter of φ13 mm, the weight has been reduced from 13 g to 6.9 g.

[0044] Figure 10 is a graph showing, as an example, the analysis results of the change in the width of the loaded zone when the inner diameter φ1 of the hollow roller corresponding to the cylindrical portion 15 shown in Figures 4 to 8 is changed. The vertical axis in Figure 6 represents the rolling element load [N], and the horizontal axis represents the roller position [deg]. The roller position 0 [deg] corresponds to the lowest point shown in Figure 2(A). The width of the loaded zone was analyzed for solid rollers with an outer diameter φ13 mm and hollow rollers with through holes of inner diameters φ8 mm, 9 mm, and 10 mm formed in solid rollers with an outer diameter φ13 mm. The analysis was performed using a finite element method (FEM) that approximates the contact between the rollers and the inner and outer rings with a linear spring. As shown in Figure 10, the load acting on the rollers decreases as the inner diameter φ1 increases, widening the loaded zone shown in Figure 2(B). Therefore, it was confirmed that hollow rollers can narrow the unloaded zone, reducing the impulse in the unloaded zone and reducing cage wear.

[0045] Figure 11 is a graph showing, as an example, the results of life tests for solid rollers and hollow rollers. The vertical axis in Figure 11 is the total number of rotations until seizure, and the horizontal axis is for solid rollers with an outer diameter of φ13 mm and hollow rollers with an outer diameter of φ13 mm and an inner diameter of 10 mm. The life tests were conducted using a traction motor bearing vibration rotation test machine at the Railway Technical Research Institute, a public interest incorporated foundation, with a load of 922 N and an inner ring rotation speed of 6000 min -1 The test was carried out under the above test conditions on a specimen with bearing nominal number: NU214, roller dimensions: outer diameter 13 mm x length 13 mm, roller material: SUJ2, and hollow diameter: 9 mm. As a result, as shown in Figures 3 to 8, it was confirmed that by configuring the rolling elements 13 as hollow rollers, it is possible to reduce the weight of the rolling elements 13, as well as widening the loaded area and narrowing the unloaded area, thereby reducing the impulse in the unloaded area and reducing wear on the cage 12.

[0046] Figure 12 is a graph showing, as an example, the results of trial calculations of the life extension effect of a wear prevention structure for a bearing according to an embodiment of the present invention. The vertical axis in Figure 12 represents the life extension effect (%) due to the hollow rollers, and the horizontal axis represents the ratio of the inner diameter φ1 to the outer diameter φ2 of the hollow rollers. As shown in Figure 12, when the ratio of the inner diameter φ1 to the outer diameter φ2 of the hollow rollers is less than 60%, the degree of weight reduction decreases and the life extension effect also decreases, and when it exceeds 90%, strength problems arise, so it has been confirmed that the optimal ratio is between 60% and 90%.

[0047] (Other embodiments) The present invention is not limited to the above-described embodiment, and various modifications and alterations are possible as described below, and these are also within the scope of the present invention. (1) In this embodiment, the bearing 9 for a traction motor of a railway vehicle has been described as an example, but the present invention can also be applied to bearings for electric motors of electric vehicles and the like, bearings for turbines in power plants, etc. Also, in this embodiment, the bearing 9 supporting the rotor shaft 6 has been described as an example, but the present invention can also be applied to bearings supporting axles, gear shafts, etc. Furthermore, in this embodiment, the rolling elements 13 have been described as cylindrical rollers as an example, but the present invention can also be applied to rolling elements 13 that are tapered rollers, spherical rollers, rod rollers, needle rollers, etc.

[0048] (2) In this embodiment, the bearing 9 is a single-row bearing, but the present invention can also be applied to a double-row bearing. Furthermore, in this embodiment, the closing portion 16 is made of a resin material, but the present invention can also be applied to a case where the closing portion 16 is made of a metal material that is lighter than the cylindrical portion 15. In this case, the closing portion 16, which has a linear expansion coefficient similar to that of the cylindrical portion 15, can be press-fitted into the cylindrical portion 15 by an interference fit or fixed with an adhesive. [Explanation of symbols]

[0049] 1 track 2 vehicles 3 wheelset 4 Main motor (electric motor) 5 Frame 6 Rotor shaft 7. Drive unit 8,9 Bearings 10 outer ring 11 Inner Circle 12 Cage 13 Rolling elements (rollers) 14 Anti-wear structure 15 Cylinder 15a Hollow part 16 Blocking section φ1,φ3 inner diameter φ2 outer diameter M Lubricant

Claims

1. A bearing wear prevention structure that prevents wear of a cage that holds rollers in a bearing, comprising: the roller is provided with a closing portion that closes a hollow portion of a cylindrical portion of the roller, the blocking portion is lighter than the cylindrical portion; A bearing wear prevention structure characterized by the above.

2. 2. The bearing wear prevention structure according to claim 1, The ratio of the inner diameter to the outer diameter of the cylindrical portion is 60% or more and 90% or less. A bearing wear prevention structure characterized by the above.

3. 2. The bearing wear prevention structure according to claim 1, the blocking portion is a lightweight member that blocks all or part of the hollow portion of the cylindrical portion; A bearing wear prevention structure characterized by the above.

4. 2. The bearing wear prevention structure according to claim 1, the blocking portion is made of a resin material or a porous material; A bearing wear prevention structure characterized by the above.

5. 2. The bearing wear prevention structure according to claim 1, the plugging portion is made of a porous material impregnated with a lubricant; A bearing wear prevention structure characterized by the above.

6. 2. The bearing wear prevention structure according to claim 1, the closing portion is made of a porous material that closes a hollow portion of the cylindrical portion in which a lubricant is accommodated; A bearing wear prevention structure characterized by the above.

7. 2. The bearing wear prevention structure according to claim 1, the bearing is a roller bearing that rotatably supports a rotor shaft of an electric motor; A bearing wear prevention structure characterized by the above.

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