153results about How to "Eliminate axial force" patented technology

The invention provides a full-pose-and-position active-passive compliant robot and a valve screwing-twisting method utilizing the robot, and relates to a robot and a valve screwing-twisting method utilizing the robot. The full-pose-and-position active-passive compliant robot and the valve screwing-twisting method utilizing the robot aim to solve the problems that an industrial robot cannot conductlarge overall motion, and the operating range is narrow; rigid collision and radial contact force are generated between an end actuator and a valve handwheel; damage of operating devices is possiblycaused due to the fact that screwing-twisting resistance torques of different valves are different; and the valve handwheel can produce axial displacement while rotating, and axial contact force of the tail end is brought. The full-pose-and-position active-passive compliant robot comprises a wheel type moving platform, a four-degree-of-freedom manipulator and a compliant end actuator, the four-degree-of-freedom manipulator is mounted on the wheel type moving platform, and a six-axis force sensor is mounted between the four-degree-of-freedom manipulator and the wheel type moving platform; the compliant end actuator is mounted at the tail end of the four-degree-of-freedom manipulator, and a six-axis force sensor is mounted between the compliant end actuator and the four-degree-of-freedom manipulator; and through information of the two sensors, impedance control can be conducted on the wheel type moving platform and the four-degree-of-freedom manipulator. The full-pose-and-position active-passive compliant robot and the valve screwing-twisting method utilizing the robot are suitable for robot remote operation, robot compliant control and valve screwing-twisting operation.

The invention discloses a method for manufacturing an outer ring of a tapered roller bearing, comprising the following steps of: a: taking a material: setting the quality of the finished product outer ring as M, setting the outer diameter as D, taking a bearing steel pipe with the outer diameter of D1 as the raw material, taking the bearing steel pipe with the quality of M1 and meeting the condition that one half of D is less than or equal to D1 which is less than D, and M1 is equal to 2M plus M2 plus 2M3, wherein M2 is the margin of quality by cutting, and M3 is the margin of quality of single outer ring by grinding process; b: cold rolling: rolling on the bearing steel pipe taken in the step a for obtaining a combined blank of the outer ring; c. cutting: cutting the combined blank at the connecting ring for obtaining a single blank of the two outer rings; d: thermal processing; and e: finish machining: grinding the single blank of the outer ring. The proposal leads the outer ring of the tapered roller bearing to realize the cold rolling for shaping, has the advantages of small material loss, saved energy consumption, simple process, high production efficiency and the like, and simultaneously ensures the product quality.

The invention relates to a high speed bearing tester, wherein the tester is provided with test accompany bearings on the left and right sides of a bearing seat provided with a test bearing, and a bridging frame is arranged between the two test accompany bearings, the bridging frame is pushed and pulled by a radial force applying mechanism to drive a test main shaft to apply a radial load on the test bearing, the axial acting force of the test accompany bearings acting on the bearing seat and the test bearing during the radial loading process is reduced by radial guide mechanisms arranged between the outer rings of the test accompany bearings and the bearing seat so as to act the counterforce of the acting force of the radial force applying mechanism on the test bearing by means of the action of the bearing seat, the radial loading force loaded by the test main shaft on the test bearing is consistently equal to a radial external force applied by the force applying mechanism on the bridging frame, and the radial guide mechanisms eliminate the axial acting force of the test accompany bearings acting on the bearing seat during the radial loading process so as to guarantee more accurate radial load measurement in the invention.

An actuator is disclosed. The actuator includes two main assemblies: (1) a motor assembly; and (2) a gearbox assembly. The gearbox assembly includes multiple stages of gear reduction and a dividing plate. In some embodiments, the gearbox assembly has a single-lead worm, a worm gear with a right-hand helix tooth direction, and a worm gear with a left-hand helix tooth direction. The worm gears are driven by the single-lead worm. The single-lead worm has two ends, one end has a right-hand tooth helix direction, and the other end has a left hand helix direction.

The invention discloses curve conjugation based symmetrical cambered surface conjugate curve gears and an engagement pair thereof. The engagement pair comprises a gear I and a gear II, wherein the gear I and the gear II are engaged with each other in a point contact mode, and a contact curve gamma 1 which is composed of engagement points on a tooth profile cambered surface of the gear I and a contact curve gamma 2 which is composed of engagement points on a tooth profile cambered surface of the gear II are conjugate curves. According to the engagement pair of the curve conjugation based symmetrical cambered surface conjugate curve gears, the contact curve gamma 1 of the gear I and the contact curve gamma 2 of the gear II which form the engagement pair are conjugate curves, and engagement points between the gear I and the gear II move along contact curves; the engagement pair has the advantages of point contact engagement, tooth profiles of point contact have the high contact strength, the contact transmission process is close to pure rolling along the axial direction, and the transmission efficiency is high; and the selection and the determination of the small tooth number and the large modulus can be achieved on the conditions of the same transmission ratio and the same center-to-center distance, the transmission requirements of high speed, heavy load, high power and high efficiency can be met, and the engagement pair has broad application prospects.

An actuator for an automotive seat that includes two main assemblies: (1) a motor assembly; and (2) a gearbox assembly. The gearbox assembly includes multiple stages of gear reduction and a dividing plate. In some embodiments, the gearbox assembly has a single-lead worm, a worm gear with a right-hand helix tooth direction, and a worm gear with a left-hand helix tooth direction. The worm gears are driven by the single-lead worm. The single-lead worm has two ends, one end has a right-hand tooth helix direction, and the other end has a left hand helix direction.

The invention discloses a test stand for testing the performance of a dynamic directional rotary steering drilling tool. The test stand comprises a frame body, a rotating device, a clamping device and a loading device, can simulate the steering process of the directional rotary steering drilling tool in actual well conditions, and can realize random adjustment for the angle of a controllable bent joint within an operating range thereof while the directional rotary steering drilling tool bear the axial pressure torque at the same time. Experimental research on the aspects such as verification for the steering performance, the reliability and a control principle of the directional rotary steering drilling tool through loading the axial pressure and torque, and research on simulated well drilling can also be carried out. The test stand can be used for performance testing and principle verification for the directional rotary steering tool.

The invention relates to a mechanical seal test device for a nuclear main pump, which is characterized by adopting a vertical structure of bottom transmission, which is driven by a motor; a speed-torque sensor is connected between a motor shaft and a main shaft through a flexible coupling; the main shaft is supported by a lower support and an upper support which are installed in an upper stand; the main shaft extends upward, and the extending part of the main shaft is sleeved with a testing shaft sleeve for installing a bench seal and a mechanical seal used in the tested nuclear main pump; thebench seal is arranged at the bottom of a lower seal cavity, and the mechanical seal for the tested nuclear main pump is arranged at the top of an upper cavity; the testing shaft sleeve is replaceable; a flow guiding sleeve is arranged in the lower seal cavity; a long tube throttling cooler and a back pressure valve are arranged at the position of the seal liquid outlet of the lower seal cavity;and an auxiliary support is matched at the top end of the main shaft. The mechanical seal test device can simulate hydrostatic mechanical seal tests for the nuclear main pump, can simulate hydrodynamic mechanical seal tests for the nuclear main pump and can simulate hydrostatic and hydrodynamic combined type mechanical seal tests for the nuclear main pump.

The invention provides a main shaft knife loosening and unloading mechanism. The mechanism is characterized in that a gland is coaxially fixed on the rear end face of a main shaft; a nut is fixed on a broach rod; a thrust bearing of a knife loosening structure is fixed at the front end of a piston; the piston is arranged in a cylinder body; an unloading disc fixed together with the cylinder body is arranged on the upper surface of the boss of the gland to form an overlap joint; a cylinder sleeve is fixed on a headstock, and is arranged in the same mounting hole together with the cylinder body; a spring is arranged between the periphery of the tail end of the piston and the cylinder body; the cylinder body, the cylinder sleeve and an unloading mechanism installation hole on the headstock jointly form a negative closed oil cavity; an axial oil injection port is processed on the rear part of the cylinder body, and forms a positive closed oil cavity together with the piston; and a radial oil injection port is processes at the tail end of the cylinder sleeve. By utilizing the main shaft knife loosening and unloading mechanism, the main shaft bearing is protected from axial force impact during knife loosening, so that the stress condition of the main shaft bearing is improved, the maintenance of rotation accuracy of the main shaft bearing is improved, and the service life of the bearing is prolonged.

The invention discloses a novel 16-gear speed changing box with oblique gears, double middle shafts and lock ring type synchronizers. The speed changing box comprises a main box part and an auxiliary box part, wherein an input shaft and a main shaft connected with the input shaft are arranged in the main box part; the main shaft is connected with a sun wheel in the auxiliary box part through a spline transition sleeve; front and rear ends of the main shaft are respectively provided with a main shaft front positioning mechanism and a main shaft rear positioning mechanism; a plurality of oblique gears are arranged on the main shaft; an input differential mechanism is arranged on the input shaft in the main box part; two lock ring type synchronizers are respectively arranged between the first gear and the second gear as well as between the third gear and the fourth gear which are arranged on the main shaft in the main box part; and a planetary gear train mechanism is arranged in the auxiliary box part. The speed changing box is operated in a labor-saving mode, gears can be shifted stably, stable transmission is performed, the noise is low, and the actual service life of the speed changing box can be prolonged.

The invention relates to the technical field of magnetic coupling and discloses a planar magnetic drive coupler. The coupler comprises a driving magnetic disc and a driven magnetic disc, which are oppositely arranged, wherein the driving disc is radially provided with driving levitated magnetic circuits and driving circumferential torsion magnetic circuits from inside to outside in sequence; the driven disc is radially provided with driven levitated magnetic circuits and driven circumferential torsion magnetic circuits from inside to outside in sequence; the driving levitated magnetic circuits align at the driven levitated magnetic circuits; and the driving circumferential torsion magnetic circuits align at the driven circumferential torsion magnetic circuits. The planar magnetic drive coupler with such a structure has the following beneficial effects that: as the levitated magnetic circuits arranged in close push-pull combination are arranged on the driving magnetic disc and the driven magnetic disc respectively, when the driving magnetic disc carries out translation, the levitated magnetic circuits can overcome the harmful axial forces generated by the circumferential torsion magnetic circuits axially so that torsion and forces can be stably driven between the driving magnetic disc and the driven magnetic disc in a contactless manner.

The invention relates to a double-vane hydraulic self-servo oscillating cylinder. According to the technical scheme, two fixed stoppers (9) are symmetrically fixed on the inner wall of a cylinder body (7). Two vanes (25) are symmetrically fixed on an oscillating output shaft (10). The two vanes (25) and the two fixed stoppers (9) are in staggered arrangement. The valve body (6) and the oil distribution disc (17) are used for oil distribution for end faces. High-pressure oil enters two corresponding work cavities through a high-pressure oil way (16), a radial high-pressure oil way of the cylinder (7), a high-pressure annular oil groove (27) and a high-pressure radial oil passage (23) and a high-pressure radial oil passage (19). Low-pressure oil of the other two work cavities returns through a low-pressure oil distribution oil way (18), a low-pressure radial oil passage (19), a low-pressure annular oil groove (26), a radial low-pressure oil way of the cylinder body (7) and a low-pressure oil way (8). The double-vane hydraulic self-servo oscillating cylinder is small in radial size, good in dynamic property, simple in oil ways, convenient to machine and easy to produce, and stress of the valve body (6) and the oscillating output shaft (10) is balanced.

A magnetic-levitation motor pure air-cooling heat dissipation structure with two impellers comprises a front axial bearing, a front impeller thrust disc, a front radial bearing, a main case, stators, a rotor, a rear radial bearing, a front impeller thrust disc and a rear axial bearing. The main case is provided with a radiating fin and a main case air hole structure; each stator is provided with a stator main case air flue, an axial stator air hole, a radial stator air hole and a stator and rotor air-gap structure. Air pressure is formed by operation of the front impeller thrust disc and the rear impeller thrust disc, cooling air enters the radial stator air flue from the main case air flue with one part flowing via stator and rotor air gap and one part flowing via the axial stator air hole and the rest flowing the stator and main case air flue, and air flow confluence is pumped to be discharged from a motor via the front impeller thrust disc and the rear impeller trust disc. A corresponding draught fan is omitted by the adoption of the impeller thrust discs, cooling structure of the motor is simplified, advantages of axial air flow and radio air flow are combined, and cooling efficiency is improved.

The invention discloses a control system and method for an ultra-supercritical secondary reheating unit to participate in power grid primary frequency modulation. The system comprises an ultrahigh-pressure cylinder regulation valve, a high-pressure cylinder regulation valve, a medium-pressure cylinder regulation valve, a first steam supplementing valve and a second steam supplementing valve; ultrahigh-pressure cylinder regulation valve, the high-pressure cylinder regulation valve and the medium-pressure cylinder regulation valve of a secondary reheating unit can be controlled to simultaneouslyparticipate in power grid primary frequency modulation in a steam supplementing regulation mode. When the practical load of a power grid is higher or lower than a rated load, the frequency of the power grid deflects for 50 HZ; the deflection change of the frequency of the power grid is received by the control system; the opening amplitudes of the ultrahigh-pressure cylinder regulation valve, thehigh-pressure cylinder regulation valve and the medium-pressure cylinder regulation valve are controlled, and the steam inlet flow of each cylinder is changed, so that the mechanical power output of asecondary reheating turbine is changed; and practical power output is matched with the load of the power grid, so that primary frequency modulation of the power grid is realized.

The oil-submersible screw-pump oil production system includes from-bollom-to-top distributed oil-submersible motor, reducer, reducer, protecting device, screw-pump and oil-production system protection device positioned over the screw-pump. The described reducer includes difference planetary cone gear transmission mechanism and hoop rotation limiting mechanism, the straight internal bevel gear in the hoop rotation limting mechanism is meshed with straight external bevel gear on the output mechanism. The protection device of the reducer includes first pressure regulating mechanism and movement converting mechanism, and its system protection device includes second sealing mechanism, second translation slide mechanism and second pressure regulating mechanism.

Disclosed a bidirectional driving disc brake comprises a disc-brake disc and a brake clamper. Wherein, the two sides of jaw of brake clamper have left and right friction plates while one friction plate is inside the clamp arm, and another one is connected to the driving device; a fixed support holder is mounted on the jaw which is on the side of driving device, and its has a projected table for supporting the inner chamber of casing of driving device and sliding matched with said casing; the driving device has three driving discs and one driving shaft while the driving shaft is drawn by the brake tight-wire to rotate the static disc or rotate two movable discs at one time; the discs can realize axial driving via the spiral surface or spiral slots arranged on disc surface and the relative rotation of steel ball; and said two movable discs are individually rigidly connected to the casing of driving device and friction plates. The invention utilizes the bidirectional driving theory of driving disc to make said two friction plates close to the disc at one time in the brake process of disc brake and clamp the disc.

The invention discloses a portable wearable upper limb rehabilitation robot. The robot comprises a tailor-made garment module and a wearable flexible actuator module. A driving system fixed to the waist of a double-layer clothes mechanism of the tailor-made clothes module rotates a line wheel, the line wheel rotates to pull a Bowden line core, and therefore the upper limbs of a human body are driven to do rehabilitation training exercise. Motion signals of subjective intention of a patient and IMU signals of an affected side oversleeve are obtained through IMU motion signals of the healthy side oversleeve and EMG physiological signals to serve as affected limb motion feedback signals, so that the pull force and the moving speed of the Bowden cable core are better controlled, and the rehabilitation efficiency is improved; meanwhile, a gravity balance mechanism is adopted in the whole device, and the energy consumption is reduced to a certain extent. The rehabilitation robot can realizemulti-joint rehabilitation exercise, is not limited by environmental conditions, reduces the working intensity of rehabilitation doctors and improves the working efficiency.

The invention discloses a micro-turbojet engine for a novel double-face compound impeller. The micro-turbojet engine comprises a starting part, a rotary part, a casing part and a rectification part. The starting part is arranged in front of the casing part. The rotary part is arranged behind the starting part. The rectification part is arranged behind the casing part. The rotary part comprises the novel double-face compound impeller, a spindle and a bearing. The spindle and the novel double-face compound impeller are connected seamlessly fixedly. The novel double-face compound impeller comprises a double-face centrifugal gas compressor. A hollow axial flow turbine is arranged in the outer extending position of a rim of the double-face centrifugal gas compressor. The double-face centrifugal gas compressor comprises two single centrifugal gas compressors which are fixedly connected back to back. The micro-turbojet engine has the advantages that heat efficiency is improved, and the oil consumption rate is lowered; the axial dimension of the micro-turbojet engine is reduced, the vibration degree is lowered, and stability is improved; and turbine front temperature can be increased with hollow turbine cooling design.

The invention relates to a method and a rod magazine for handling elongated rods in a rock drilling unit, and to a bolting unit. Elongated rods (9), such as drill rods and rock bolts, are stored into a linear rod magazine (13) provided with feed members (19) for transferring the rods upward and downward in the magazine. The feed members (19) comprise screw surfaces (25) by which the rods are supported in the magazine. The required feeding movement is produced by rotating the feed members about their rotation axis. In addition, the rod magazine comprises transfer means that allow the rods to be transferred from the magazine to a drilling line or bolting line, i.e. to a centre (K), and vice versa. The transfer means are provided with gripping means (34) for gripping the rods.

The invention discloses a herringbone tooth surface gear transmission mechanism. The herringbone tooth surface gear transmission mechanism comprises a herringbone tooth surface gear and a herringbone tooth cylindrical gear. The herringbone tooth surface gear comprises a disc gear body and a gear shaft. First herringbone teeth annually distributed are arranged on the surface of one side of the disc gear body. Second herringbone teeth are arranged on the periphery of a gear body of the herringbone tooth cylindrical gear. Each first herringbone tooth is composed of a first right-handed gear tooth and a first left-handed gear tooth which are connected to be herringbone in a butt joint manner. Each second herringbone tooth is composed of a second left-handed gear tooth and a second right-handed gear tooth which are connected to be herringbone in a butt joint manner. The second left-handed gear teeth are meshed with the first right-handed gear teeth. The second right-handed gear teeth are meshed with the first left-handed gear teeth. The invention further discloses a tooth milling method for the herringbone tooth surface gear in the herringbone tooth surface gear transmission mechanism. The herringbone tooth surface gear transmission mechanism is high in bearing capacity, good in meshing performance, stable in transmission, low in noise and high in practicability. By means of the tooth milling method for the herringbone tooth surface gear, the tooth width of the herringbone tooth surface gear can be utilized to the maximum extent.

The invention discloses a planetary gear power-distributing-type steering mechanism which comprises a box. A middle power transmitting part, a steering control part, a steering planetary transmission part, a left external driving gear and a right external driving gear are installed on the box. The box is connected with a gearbox, a power output shaft of the gearbox is connected with the steering planetary transmission part, the steering planetary transmission part is respectively connected with the left external driving gear and the right external driving gear, and the steering control part is connected with the steering planetary transmission part through the middle power transmitting part to achieve steering control. According to the planetary gear power-distributing-type steering mechanism, steering power is input from gear rings of a planetary gear transmission mechanism in a distributed mode to a traveling transmission mechanism through steering bevel gears to achieve steering, power failures do not exist during steering, and the transmission efficiency is high; indirect control is adopted for steering control, and on the premise that the steering control characteristic is guaranteed, the structure of the steering planetary transmission part is effectively simplified; the planetary gear power-distributing-type steering mechanism is easy and convenient to operate, driving is easily carried out, and convenience is brought to achieving high-accuracy steering wheel steering of a caterpillar tractor.

The invention discloses a composite propulsion helicopter transmission system which comprises a main rotor transmission system and a two-wing propeller transmission system in transmission connection with the main rotor transmission system, and further comprises a belt transmission system in transmission connection with the main rotor transmission system. The problems that an aviation piston engine is large in vibration, low in reliability, poor in transmission performance and the like during non-load starting in the prior art are solved.

The invention discloses a centrifugal water pump provided with two impellers. The water pump comprises a pump body (1); a water inlet (11) and a water outlet (12) are formed in two ends of the pump body (1); a water inlet partition (2) is arranged at the water inlet (11) to divide a water inlet channel into a first water inlet channel (21) and a second water inlet channel (22); a water outlet partition (3) is arranged at the water outlet (12) to divide a water outlet channel into a first water outlet channel (31) and a second water outlet channel (32); a motor assembly comprising a spindle (8) is arranged in the pump body (1); two ends of the spindle (8) are connected with a first impeller (41) and a second impeller (42); the first water inlet channel (21) and the second water inlet channel (22) are led into an inlet of the first impeller (41) and an inlet of the second impeller (42) from two sides of the pump body (1); and a liquid enters via the water inlet (11), enters the first impeller (41) and the second impeller (42) from two sides of the pump body (1) after being divided by the first water inlet channel (21) and the second water inlet channel (22), is collected in the first water outlet channel (31) and the second water outlet channel (32) after flowing out of the first impeller (41) and the second impeller (42) and flows out of the water outlet (12). The invention can be applied to the field of water pumps.

The invention discloses a device and method for measuring the friction moment of a deep groove ball bearing under gravity or microgravity, and relates to the field of bearing friction force measurement. The device comprises a mounting plate, and is characterized in that a torque sensor and an eccentric block are coaxially mounted on the mounting plate; a to-be-tested deep groove ball bearing sleeves a transmission shaft between the torque sensor and the eccentric block; a driving device is mounted on the mounting plate so as to drive the torque sensor to rotate, and the eccentric block is driven to rotate. Accordingly, gravity disturbance of a load is eliminated, the problem that the friction force of the deep groove ball bearing under the microgravity has difficulty in direct measurementis solved, and measurement of the friction force of the deep groove ball bearing under the microgravity is more convenient and accurate.

A transmission has a rotatable differential cage (74) and two output shafts (64). In order to distribute a torque between the output shafts (64), at least one balancing wheel (76) is rotatably mounted on the differential cage (74), which balancing wheel (76) is drive-coupled to a respective drive wheel (78) of the output shafts (64). The gearing also has at least one concavely curved coupling wheel (80) which is drive-coupled firstly to at least one of the drive wheels (78) and secondly to at least one hollow shaft (82). The hollow shaft (82) surrounds one of the output shafts (64). The hollow shaft (82) can be braked or driven relative to a part of the gearing.

Disclosed is an adjustable thrust structure for balancing axial force of a gear. An oil groove is arranged on a thrust washer (2), a supporting seat (6) is fixed on a box (3) through a screw (5), the thrust washer (2) is installed over the supporting seat (6), an accessory pump drive shaft (1) is connected with a helical gear (7), a gland nut (4) is connected with a tapered shaft of the accessory pump drive shaft (1), and the other end of the accessory pump drive shaft (1) is connected with a pump body. According to the adjustable thrust structure, thrust positions of the axial force can be adjusted flexibly through adjustment of the thickness of the thrust washer (2), therefore the axial force is balanced at different positions, poor phenomena on an accessory pump due to the present of the axial force are eliminated, using requirement for the complete machine are met, and the cost is reduced.

The invention discloses a single downdraft electric driving pump structure capable of automatically balancing an axial force, which comprises a motor, impellers, a pump body water inlet and a water outlet, wherein the water inlet is formed at the lower end of a pump body, has a downdraft structure and comprises a water intake section, a middle water distribution section and an upper discharge section from bottom to top; the motor is arranged at the position of the water intake section; the impellers are arranged in the middle water distribution section which consists of a multi-stage pump; forward guide vanes are arranged in a lower-stage pump body; backward guide vanes are arranged in an upper-stage pump body; and the forward guide vanes and the backward guide vanes have opposite rotating directions and symmetrical structures. The single downdraft electric driving pump structure capable of automatically balancing the axial force adopts the structure with one-way water intake and oppositely arranged impellers and also adopts a mode of symmetrically arranging the forward guide vanes and the backward guide vanes so as to completely eliminate the coaxial force; and a difference between forward and backward rotation stages of the forward guide vanes and the backward guide vanes can be one stage so as to control the direction of the coaxial force, make the motor run in an optimal functional mode, and greatly prolong the service life of the electric pump.

The invention provides a main rotor hub mechanism for an unmanned helicopter. The main rotor hub mechanism comprises a main hub head, wherein the main hub head is connected with a connecting shaft; the connecting shaft is connected with a main rotor hub; the connecting shaft penetrates through a grease pocket inside the main rotor hub; a thrust bearing II and a ball bearing II are sequentially arranged on the left side of the grease pocket from the right to the left; a spacer sleeve II is arranged between the thrust bearing II and the ball bearing II; a thrust bearing I and a ball bearing I are sequentially arranged on the right side of the grease pocket from the right to the left; a spacer sleeve I is arranged between the thrust bearing I and the ball bearing I; a grease filling port communicated with the grease pocket is formed in the main rotor hub; the main rotor hub is connected with a main rotor blade; and rotor blade limiting screws are arranged on the main rotor hub. The main rotor hub mechanism disclosed by the invention has the advantages that axial force stressed by the ball bearing can be eliminated by changing a layout manner of the bearings in the hub, and the servicelife of the main rotor hub is prolonged; and moreover, the grease pocket is formed inside the hub, and the grease filling port is increased on the hub, so that convenience is brought to lubrication of the bearings in the hub.