105results about "Ball and roller bearings" patented technology

The utility model provides a composite bearing with double rolling bodies, which can solve the problems that a transmission system is difficult to arrange and the structural coordination of the transmission system is influenced due to large local structure and large occupied design space when a radial bearing and a thrust bearing are combined to bear larger radial and axial loads. The bearing comprises an outer ring, an inner ring, a retainer, a first snap ring, a second snap ring and a plurality of composite rolling bodies, one end of the outer ring is provided with a first retaining shoulder, the inner side of the other end of the outer ring is provided with a first snap ring groove for mounting the first snap ring, one end of the inner ring is provided with a second retaining shoulder, and the outer side of the other end of the inner ring is provided with a second snap ring groove for mounting the second snap ring. A first cylindrical surface roller path, a second cylindrical surface roller path and a concave surface roller path are arranged between the inner side of the outer ring and the outer side of the inner ring, each composite rolling body is composed of two cylindrical rollers and a spherical roller, and the two cylindrical rollers and the two spherical rollers are matched with the first cylindrical surface roller path, the second cylindrical surface roller path and the concave surface roller path respectively; and the retainer is provided with a limiting hole for mounting the composite rolling body.

A method for manufacturing a transmission device that includes a casing, and a rotary part rotatably guided inside the casing by means of a first bearing and a second bearing. The method includes axially moving a preloading element in a first recess until it bears axially against the first bearing in the first direction, and then applying a force to the preloading element until the applied force reaches a set value and the preloading element reaches a preloading position in which a predetermined axial preloading force is applied by the preloading element and the axial bearing surface of the casing to the first bearing and the second bearing, respectively. The preloading element is attached to the casing in in the preloading position.

A rolling bearing includes a first ring and a second ring capable of rotating concentrically relative to each other, at least one row of rolling elements radially interposed between raceways of the rings, at least one row of rolling elements axially interposed between raceways of the rings, and at least one inner seal mounted on one of the first and second rings and coming into friction contact with the other ring of the first and second rings. The rolling bearing further includes at least one outer sealing assembly provided with a sealing shield mounted against the first ring and coming into friction contact with the second ring, the sealing shield being arranged outside the inner seal and defining together with the inner seal an annular sealed chamber.

A rotor assembly for a rotary wing aircraft includes a rotor hub, a rotor blade coupling coupled to the rotor hub, a hub extender coupled to the rotor hub, and a first bearing assembly. The first bearing assembly includes a clevis coupled to the hub extender and including two arms, each arm including a clevis opening, two cylindrical bearings, each cylindrical bearing extending through one of the clevis openings, a spherical bearing positioned between the two arms and coupled to the rotor blade coupling, and a first pin extending through the two cylindrical bearings and the spherical bearing.

The utility model relates to the technical field of bearings, and discloses a long-life conical bearing which comprises an inner ring mechanism and an outer ring mechanism, the inner ring mechanism comprises a bearing inner ring, a plurality of first ball rollers are connected in a roller slide way on the outer side of the bearing inner ring in an equal-angle rolling mode, and the outer ring mechanism comprises a conical outer ring. And a plurality of second ball rollers are in equal-angle rolling connection in the roller slide way on the inner side of the conical outer ring. The integral conical bearing adopts a double-rotation structural design and comprises the middle ring, the roller slideways are respectively arranged on the inner side and the outer side of the middle ring, and the ball rollers are assembled in the roller slideways and can be respectively matched with the roller slideways of the conical outer ring and the bearing inner ring. The middle ring rotates relative to the conical outer ring and the bearing inner ring, that is, the whole conical bearing is provided with two groups of independent auxiliary rotating structures, so that compared with a single group of auxiliary rotating structures, the abrasion of the conical bearing can be reduced, and the service life of the conical bearing is further prolonged.

A roller bearing (20) for a transmission assembly (3) for a helicopter (1) is described, comprising a first ring (51) extending around a first axis (A); a second ring (50) extending around the first axis (A) and radially external to the first ring (51); first roller bodies (55) shaped like conical rollers forming a single crown (54) coaxial to the first axis (A) and cooperating with the first and second rings (51, 50), so as to roll on respective first roller tracks (53, 52); and a third ring (70) that can rotate around the first axis (A) and defining a first shoulder (71) axially cooperating with the first roller bodies (55); a fourth ring (65) extending around the first axis (A) and radially spaced apart from the first shoulder (71); and multiple second roller bodies (66) interposed radially to the first axis (A) between the third ring (70) and fourth ring (65), and cooperating with the third and fourth rings (70, 65), so as to roll on them.

A low-friction high-bearing-capacity ball column composite turntable bearing comprises an inner ring and an outer ring, a row of rolling bodies are arranged between the two side faces of the outer ring and the inner ring, a plurality of radial rolling bodies are annularly distributed between the inner circumferential face of the outer ring and the inner ring, and each row of rolling bodies comprises three rows of rolling bodies. The three rows of rolling bodies are sequentially an inner side rolling body, a middle rolling body and an outer side rolling body which are annularly distributed, each row of rolling bodies is limited through the corresponding split type retainer, each split type retainer comprises an upper frame piece and a lower frame piece which are arranged in a stacked mode, the upper frame piece and the lower frame piece are provided with an upper pocket groove and a lower pocket groove respectively, and the upper pocket groove and the lower pocket groove form a pocket hole; the inner side rolling bodies and the outer side rolling bodies are spherical rollers, and the middle rolling bodies and the radial rolling bodies are cylindrical rollers. And retainer connecting balls are arranged between the adjacent split retainers. Sliding friction caused by different speeds of the inner side and the outer side of the roller is weakened, so that the friction torque of the bearing is reduced; and the rigidity and the bearing capacity of the bearing are improved.

To provide a manufacturing method of a hub unit bearing which can accurately measure a size of a negative clearance and strictly control the size of the negative clearance.SOLUTION: A hub unit bearing 10 includes: a ball bearing part in which rolling elements forming one of double rows are balls; and a conical roller bearing part in which rolling elements forming the other row are conical rollers. A manufacturing method of the hub unit bearing 10 includes: a step in which a measuring jig 60 corresponding to an inner ring 37 and conical rollers 52 is assembled to a hub ring 31 to measure an axial clearance S between the inner ring 37 and the measuring jig 60 in a state where the hub ring 31, an outer ring 20, and balls 42 are assembled; and a step in which the inner ring 37 is fixedly fitted in a small diameter step part 34 of the hub ring 31 by using an assembly 55 having the inner ring 37, the conical rollers 52, and a retainer 51 so that a space between the small diameter step part 34 of the hub ring 31 and the inner ring 37 is formed into a desired negative clearance based on the measured axial clearance S.SELECTED DRAWING: Figure 2

The positional relationship between the supply port for supplying lubricant to a bearing containing a nearly cylindrical rotating member and the discharge port for discharging lubricant, as well as the rotational motion of the bearing, are considered to suppress lubrication failure on the sliding surface of the rotating member. [Solution] The rotating mechanism 1 includes a bearing 10 which comprises a substantially cylindrical rotating member 11 consisting of a first bottom surface 111 and a second bottom surface 112 that slide against the inner ring 12, and a side surface 113 that is continuous therewith and rolls on the surface 121 of the inner ring 12 and the surface 131 of the outer ring 13; a supply port 14 for supplying lubricant located near the first bottom surface 111 which is further from the axis of the bearing 10 than the second bottom surface 112; and a discharge port 17 for discharging lubricant located near the second bottom surface 112 of the rotating member 11.

The utility model provides a multipurpose thin oil vibration exciter, and belongs to the technical field of vibration exciters. The multipurpose thin oil vibration exciter comprises a vibration exciter structure and a driving structure. The vibration exciter structure comprises a bearing cavity, an outer taper sleeve and a shaft rod, the bearing cavity is installed on the outer taper sleeve through a connecting piece, two cylindrical roller bearings are further connected to the shaft rod in an interference fit mode, and the one-way thrust ball bearing, the two cylindrical roller bearings and the blades are located in the bearing cavity. And the blades are positioned between the two cylindrical roller bearings. The driving structure comprises a driving motor and an eccentric block, and an auxiliary eccentric block is fixed to the surface of the eccentric block. According to the utility model, oil in the oil cavity is in a suspended rolling state by utilizing mutual matching of the blades without increasing other power, a flowing oil film is formed on the surface of the bearing, the lubricating effect and the cooling effect can be achieved, and meanwhile, the sealing mode is changed, so that the failure rate is reduced, and the service life is prolonged.

The invention relates to a bearing, in particular to a double-row roller bearing with a ball arranged in a crossed four-point contact ball-cut spherical rolling body, which comprises an outer ferrule, a ball-cut spherical rolling body, a double-half inner ferrule, a crossed rolling body retainer and a double-row cylindrical roller, and is characterized in that ball top surfaces, which are extremely easy to generate sliding friction, at two ends of an axial lead of the spherical rolling body are cut off; each ball-cutting-shaped spherical rolling body forms a crossed stress state in a good state of two-point contact, pure rolling and no rotary friction, and the axial clearance of each ball-cutting-shaped spherical rolling body is selected between zero axial clearance and negative axial clearance; the ball-cut spherical rolling bodies are arranged between the double-row rollers in a crisscross manner to independently bear the axial load of the bearing in a manner of replacing the sliding friction between the large ends of the rollers and the retaining shoulders with pure rolling friction, so that the pressure sliding friction between the ends of the double-row rollers and the retaining shoulders is almost zero, and the sliding friction between the large ends of the rollers and the retaining shoulders is greatly reduced; good oil films are formed between the two ends of the roller and the retaining shoulders.

The utility model discloses a combined bearing of an angular contact ball bearing and a cylindrical roller bearing, which is characterized in that a first groove group is arranged on the inner surface of an outer ring of the angular contact ball bearing, and first chamfers are arranged on two sides of the surface of the outer ring; a second groove group is formed in the surface of the inner ring of the angular contact ball bearing, and the oil inlet hole is communicated with the second groove group; the steel balls are in four-point contact with the first groove group and the second groove group; the angular contact ball bearing and the cylindrical roller bearing are sequentially arranged between the pump shaft and the bearing seat in a sleeving mode, and second chamfers are arranged on the two sides of the surface of the outer ring of the cylindrical roller bearing. The annular groove is formed by a first chamfer and a second chamfer in a contact mode, one face of the annular groove is communicated with the oil inlet hole, and the other face of the annular groove is communicated with the bearing seat oil filling hole. The utility model provides a combined bearing of an angular contact ball bearing and a cylindrical roller bearing, which solves the problems of poor lubrication, high temperature, easiness in abrasion and high maintenance cost of the existing positioning bearing.

The invention provides a combined bearing which comprises an outer ring, an inner ring, a plurality of first rollers, a second roller, a third roller, a first ferrule and a second ferrule, the inner ring is used for sleeving a mandrel, two rows of first raceways for filling the first rollers are formed between the outer ring and the inner ring, and the first ferrule and the second ferrule are arranged on the outer ring and the inner ring. The two axial sides, corresponding to the inner ring, of the mandrel are sleeved with the first ferrule and the second ferrule respectively, the first ferrule and the end face of one axial side of the outer ring form a second roller path for filling of a second roller, and the second ferrule and the end face of the other axial end of the outer ring form a third roller path for filling of a third roller. The second roller is a ball roller, and a dustproof cover is arranged between the first ferrule and the outer ring. Aiming at the defects in the prior art, the invention provides the combined bearing which can simultaneously bear multidirectional loads, is high in rotating speed and is good in sealing effect.

The application discloses a high-load-capacity needle bearing and relates to the technical field of bearings. The high-load-capacity needle bearing comprises a bearing ring assembly, a bearing retaining assembly and a guide assembly fixed on the surface of the bearing retaining assembly. The bearing retaining assembly comprises a retainer, the outer surface of the retainer is provided with an installation groove, and the inner wall of the installation groove is uniformly provided with a plurality of needle holes in the circumferential direction. When the ceramic material-made ball body is in contact with the outer ring side groove and the inner ring side groove, the rolling friction coefficient is significantly reduced, which helps to reduce energy loss and improve the rotating speed of the bearing during operation. The ball body can share part of the load borne by the retainer. During the operation of the bearing, especially when a large radial or axial load is borne, the ball body can uniformly transmit part of the load to the bearing outer ring and the bearing inner ring, thereby reducing the burden of the retainer and improving the overall load-carrying capacity of the bearing.

The utility model discloses a high bearing capacity conjoined bearing for limited space, which comprises a bearing outer ring, a bearing inner ring solid shaft and a rolling body, the inner side of the bearing outer ring is provided with a steel ball outer raceway and a cylindrical roller outer raceway, and the steel ball outer raceway and the cylindrical roller outer raceway are arranged in parallel; a steel ball inner raceway corresponding to the steel ball outer raceway is arranged on the outer side of the bearing inner ring solid shaft; cylindrical roller inner raceways corresponding to the cylindrical roller outer raceways are arranged on the outer side of the bearing inner ring solid shaft; the rolling bodies are positioned between the steel ball outer raceways and the steel ball inner raceways as well as between the cylindrical roller outer raceways and the cylindrical roller inner raceways; according to the ball bearing, the characteristics of high rotating speed and low friction torque of the ball bearing are reserved, large axial loads can be borne, accurate positioning can be achieved, and the radial bearing capacity is remarkably improved through the design of the full complement needle rollers; and meanwhile, due to the integrated structural design, the bearing has a compact radial size and is suitable for the requirement in a limited space.

A rolling bearing having an inner raceway and an outer raceway and a plurality of rolling elements arranged between the inner raceway and the outer raceway. The rolling bearing is medium-lubricated or oil-free lubricated. The lubricant forms an elastic hydrodynamic lubricant film between the rolling elements and the raceway. When the rolling bearing is used for the first time, at least one surface of the rolling bearing is coated with a protective fluid, preferably, the protective fluid is an oil-based anti-corrosion fluid. In addition, a refrigerant compressor having such a rolling bearing.

A leg assembly (102) of a tricone bit includes a cone and a leg fitting inside the cone. The leg includes an axis (232) defining an axial center of rotation of the cone, a first raceway for a first row of bearings (202), a second raceway for a second row of bearings (206), and a third raceway for a third row of bearings (210) disposed between the cone and the leg, at a distal end (204), at a middle section (208), and at a proximal end (212) of the leg. A first clearance for the first row of bearings for the first raceway is less than a second clearance for the second row of bearings for the second raceway, which is less than a third clearance for the third row of bearings for the third raceway, such that the first row of bearings initially supports most of the radial load applied to the tricone bit.

A leg assembly of a tricone bit includes a cone and a leg fitting inside the cone. The leg includes an axis defining an axial center of rotation of the cone, a first raceway for a first row of bearings, a second raceway for a second row of bearings, and a third raceway for a third row of bearings disposed between the cone and the leg, at a distal end, at a middle section, and at a proximal end of the leg. A first clearance for the first row of bearings for the first raceway is less than a second clearance for the second row of bearings for the second raceway, which is less than a third clearance for the third row of bearings for the third raceway, such that the first row of bearings initially supports most of the radial load applied to the tricone bit.

The utility model provides a combined bearing which comprises an outer ring and an inner ring, and the outer ring is arranged on the inner ring; a first roller path and a second roller path are arranged on the outer ring, a third roller path corresponding to the first roller path is arranged on the inner ring, and a fourth roller path corresponding to the second roller path is arranged on the inner ring; the first roller path and the third roller path form a straight roller path, and the second roller path and the fourth roller path form a groove R roller path; a cylindrical roller is arranged in the straight raceway, and an angular contact ball is arranged in the groove R raceway. The combined bearing provided by the utility model not only has the high-speed rotation capability of the cylindrical roller bearing and the angular contact ball bearing, but also has the capability that the cylindrical roller bearing can bear a large radial load and the angular contact ball bearing can bear a one-way axial load.

The rolling bearing comprises a first ring (10) and a second ring (12) which are suitable for rotating concentrically with each other, at least one row of rolling elements (16) arranged radially between the raceways of the rings, at least one row of rolling elements (14) arranged axially between the raceways of the rings, and at least one inner seal (28) which is fixed to one of the two rings (10, 12) and comes into frictional contact with the other of the first and second rings. The rolling bearing further comprises at least one outer seal assembly 32 provided with a seal shield 34 secured to the first ring 10 and in frictional contact with the second ring, the seal shield 32 being disposed outside the inner seal 28 and forming an annular seal chamber together with the inner seal 28.

To provide a linear guide which can maintain the stable operation performance of a ball with a hole diameter of a ball return path maximized.SOLUTION: When an opening part at a side at which the opening part is connected to a load rolling path 24 out of both opening parts of a direction conversion path 26 is defined to be a rail-side opening part 28, and an opening part at a side at which the opening part is connected to a ball return path 23 is defined to be a return-path side opening part 29, an inside recessed groove 41, which defines an internal peripheral face of the direction conversion path 26, has cross section shapes different between at the rail-side opening part 28 and at the return-path side opening part 29 on respective planes orthogonal to a center axial line CL of the direction conversion path 26, and in an arbitrary cross section parallel with a plane along the center axial line of the direction conversion path, points of the inside recessed groove at both of the opening parts are connected to each other by a single circular arc or a plurality of smoothly-continuing circular arcs.SELECTED DRAWING: Figure 6

The utility model discloses an integrated needle roller thrust bearing, and relates to the technical field of bearings, the integrated needle roller thrust bearing comprises an outer shaft sleeve, the side surface of the outer shaft sleeve is provided with a side surface stress groove for installing an axial limiting sleeve, the axial limiting sleeve is movably connected in the side surface stress groove, and the side surface of the axial limiting sleeve is also movably connected with a thrust sheet; the axial limiting sleeve comprises a ball retainer clamped and matched with the inner side of the side face stress groove, limiting holes are formed in the ball retainer in an annular array mode, and a spherical ball is placed in each limiting hole. According to the utility model, when the thrust sheet is subjected to circumferential rotating force, the thrust sheet can rotate on the side surface of the axial limiting sleeve, and meanwhile, the thrust sheet rotates to drive the spherical balls in the limiting holes to roll, so that the bearing not only can bear the axial force, but also can bear the radial force, and the use function of equipment is further increased.

The utility model relates to the technical field of encoders, in particular to a single-bearing type encoder shaft system structure, which is characterized in that a bearing inner ring is sleeved on a main shaft, the lower end of the main shaft is provided with a radial boss, and the radial boss is used for propping against the lower end surface of the bearing inner ring; the main shaft is provided with a thread matched with a locking nut above the radial boss, and the locking nut abuts against and is locked on the upper end face of the bearing inner ring; the rolling body abuts against the main body and the bearing inner ring. The rolling body comprises balls and pin rollers which are arranged alternately. According to the utility model, the bearing and the main body are integrated, and a traditional bearing outer ring is omitted; the design that the balls and the pin rollers are arranged alternately is adopted, a single-row bearing structure is achieved, and axial and radial gaps are effectively eliminated.

The utility model discloses a combined type bearing for an electric tool, which comprises a bearing outer ring, an inner cylinder is arranged in the bearing outer ring, a roller pin is connected in each vertical groove, first seat sleeves are arranged on the upper surface and the bottom surface of the inner cylinder, a second seat sleeve is sleeved in each first seat sleeve, and the second seat sleeve is connected with the first seat sleeve. Limiting grooves are formed in the upper surface of each first seat sleeve and the upper surface of each second seat sleeve, a retaining ring is connected to the interior of each limiting groove, the retaining rings are connected through connecting rods, and balls are placed in each retaining ring; according to the bearing, the first seat sleeve and the second seat sleeve are arranged, the balls are arranged in the first seat sleeve and the second seat sleeve, and the two groups of balls are rotationally matched with the roller pin, so that the friction between the bearing inner ring and the bearing outer ring is reduced, and lubricating oil is smeared on the surfaces of the balls and the roller pin through the oil inlet holes under the matching of the oil inlet holes; and the lubricity of the balls and the roller pins is improved, so that the abrasion degree of bearing parts is reduced.

The utility model relates to a connecting shaft type one-piece synchronous pulley, which aims at solving the technical problems of poor balance and stability, large noise, high production cost and inconvenience in installation and use due to the fact that few similar products adopt inner shafts as inner ring structural design of one-piece bearings. Equally-spaced teeth are arranged on the outer diameter of an outer ring wheel body of the conjoined synchronous belt wheel. The rolling wheel is characterized in that double rows of rolling needles, double rows of steel balls or a combination of one rolling needle and one steel ball are arranged between the inner diameter of the outer ring wheel body and the outer diameter of the inner shaft at equal intervals, the inner shaft is a connecting shaft concentric inner shaft or a connecting shaft eccentric inner shaft, and the centers of the two ends of the inner shaft extending out of the outer ring wheel body are provided with protruding installation columns with external threads respectively. Dustproof covers are respectively arranged at annular orifices formed by the two sides of the outer diameter of the inner shaft and the inner diameter of the outer ring wheel body in a flush manner; and the double rows of rolling needles, the double rows of steel balls or a combination of one rolling needle and one steel ball respectively correspond to two channels, two wide grooves or a combination of one channel and one wide groove of the inner diameter of the wheel body of the outer ring and the outer diameter of the inner shaft.

The utility model discloses a medical large-scale superfinishing pin shaft bearing which comprises an outer shaft washer, a sliding bead is embedded and installed on the outer wall of a pin shaft in a rolling mode, a limiting installation ring is installed on the inner wall of a threaded ring groove in an inserted mode, a rolling shaft and the sliding bead are connected with a sliding rail in a sliding mode, and a positioning inserting groove is formed in one end of the pin shaft. And a mounting block is inserted into the inner wall of the positioning slot, a positioning insertion block is fixedly connected to one end of the side face of the mounting block, and a second fixing bolt is inserted into the positioning insertion block. According to the medical large superfinishing pin shaft bearing, double sliding rotation can be conducted through the outer shaft ring, the inner shaft ring and the pin shaft through the rolling shaft and the sliding balls, the rotating effect is good, the outer shaft ring, the inner shaft ring and the pin shaft can be spirally disassembled and assembled through the threaded ring grooves and the limiting installation rings, the rolling shaft and the sliding balls can be rapidly disassembled, assembled and replaced conveniently, and the service life of the bearing is prolonged. And moreover, the mounting block can be quickly adapted and replaced through a positioning slot, a second fixing bolt and a positioning insertion block, so that the adaptive mounting is convenient, and the use is more convenient.

The invention discloses a three-row angular contact hub bearing assembly which comprises a flange inner ring and a flange outer ring, a ring body is arranged on the flange inner ring in a matched mode, a first roller path is arranged between the flange inner ring and the flange outer ring, and a second roller path and a third roller path are arranged between the flange outer ring and the ring body. A first rolling body is matched in the first raceway, a second rolling body is matched in the second raceway, a third rolling body is matched in the third raceway, the first rolling body is a tapered roller, and the second rolling body and the third rolling body are balls. The structure layout is compact, operation is more stable and reliable, the transmission efficiency and the bearing capacity are high, and the use requirement of an electric vehicle hub motor driving system is met.

This invention discloses a high-load-bearing ball-roller hybrid bearing structure, comprising an inner ring, an outer ring, a single row of steel balls, and a double row of cylindrical rollers. A first raceway is circumferentially formed on the outer peripheral wall of the inner ring and the inner peripheral wall of the outer ring. Two first raceways combine to form a central raceway for the movement of the single row of steel balls. Second raceways are formed at both ends of the outer peripheral wall of the inner ring and the inner peripheral wall of the outer ring. Two second raceways on the same side combine to form an outer raceway for the movement of the single row of cylindrical rollers. Two outer raceways are symmetrically positioned on either side of the central raceway. The central raceway is a four-point contact raceway. The single row of steel balls forms a four-point angular contact fit with the first raceways of the inner and outer rings, respectively. The double row of cylindrical rollers corresponds one-to-one with the two outer raceways, and each row of cylindrical rollers forms a line contact fit with its corresponding outer raceway. This invention solves the problems of existing cylindrical roller bearings being unable to withstand bidirectional axial loads and the insufficient radial load-bearing capacity of traditional four-point contact ball bearings.

The utility model relates to the field of bearings, and discloses a high-load-bearing tapered roller bearing which comprises an outer ring and an inner ring, the inner ring is arranged on the inner side of the outer ring, roller structures are arranged between the outer ring and the inner ring in an up-down arrangement mode, a rotation protection structure is arranged at the position, close to the lower portion of the center, between the outer ring and the inner ring, and a protection layer is arranged on the inner side wall of the inner ring. Compared with a traditional single-layer roller structure, the double-layer roller bearing has the advantages that the double-layer roller structure, namely the first roller and the second roller, is arranged up and down and is inclined, so that the double-layer roller bearing can bear loads from different directions and sizes more uniformly, and the bearing capacity of the bearing is remarkably improved; according to the design, the limitation of a traditional bearing in the aspect of bearing performance is broken through, the protection coating is made of a polytetrafluoroethylene material, the effects of protection and friction reduction can be achieved when the ball rotates, the friction coefficient between the ball and other parts is reduced, energy loss is reduced, and the working efficiency of the whole bearing is improved.