41results about How to "Improve driving efficiency" patented technology

The application discloses a single-shaft active and passive mixed driving intelligent artificial knee joint structure with energy recovery function, which comprises a joint rotating module, a gear transmission module, a hydraulic damping module, a rack and a motor. The gear transmission module comprises a primary bevel gear transmission system, a secondary gear transmission system, a synchronous belt wheel transmission assembly and a transmission rack. The motor is fixed on the transmission rack. In the active stage, the motor provides an active driving torque for the knee joint through the gear transmission module and the joint rotating module. In the passive stage, the joint rotating module transmits a passive torque of the knee joint to the motor through the gear transmission module, drives the motor to rotate, so that the motor generates electricity to recover energy, and the hydraulic damping module provides a damping torque to ensure the stability of the knee joint. In various use occasions, the required damping or driving torque can be obtained, the power consumption of the motor can be reduced by recovering the passive torque of the knee joint in the passive stage, and the working endurance of the intelligent artificial limb is improved.

The utility model provides a kind of annular cutting equipment, it is related to cutting field, including main support, rotary support, radial feed mechanism, it is characterized by: the main support is composed of base, linear motion mechanism, drive mechanism, gravity balance system, the drive mechanism is composed of rack, first speed reducer, gear and first servo motor, the rack is fixed on base by bolt, the first speed reducer is fixed on linear motion mechanism, the gear is fixed on the output shaft of first speed reducer and is engaged with rack, the first servo motor is installed in the input end of first speed reducer, drive gear linearly moves along rack by first speed reducer speed reduction and torque increase, in the utility model, each transmission part adopts speed reduction and torque increase mechanism, under the premise of guaranteeing output torque, the whole machine power is reduced, by adopting gravity balance mechanism, the load caused by further reducing gravity is reduced, to realize the maximization of whole machine driving efficiency.

This application discloses a tactile sensor and its fabrication method. The tactile sensor includes a tactile membrane, an optical window, a cavity, a deformation structure, and a capacitor structure. The cavity is enclosed by a cavity wall and two opposing openings at both ends. The two openings respectively house the tactile membrane and the optical window. The deformation structure is located within the cavity and is used to absorb energy from an external light source. Under photothermal action, it deforms, thereby displacing the tactile membrane to generate tactile stimulation that can act on a target object. The capacitor structure converts the tactile stimulation into an electrical signal for tactile information acquisition. This application utilizes the deformation structure to deform within a certain temperature range, thereby displacing the tactile membrane and converting light energy into tactile output. This avoids the dependence of traditional light-driven tactile devices on closed air cavities, gas expansion, and suspended light-absorbing sheets, improving the structural stability and driving efficiency of the tactile sensor and increasing its environmental adaptability.

The invention relates to an unmanned logistics vehicle steering control method and device, computer equipment and a storage medium. The method comprises the following steps: acquiring state information and environment information of a vehicle; respective steering cost of various preset steering modes is calculated according to the state information and the environment information, wherein the various preset steering modes comprise Ackerman steering, front and back double-steering and bidirectional driving; the steering mode of the current vehicle is obtained, if the steering mode with the minimum steering cost is different from the current steering mode and the cost difference between the steering mode with the minimum steering cost and the current steering mode is larger than a preset switching threshold value, the steering mode is determined as a target steering mode, and otherwise, the current steering mode is maintained; and controlling the vehicle to run in the target steering mode. By the adoption of the method, the unmanned logistics vehicle can autonomously select the optimal steering mode, frequent mode switching is avoided, and the driving efficiency and smoothness in different scenes are improved.

This invention relates to a tail fin structure with independent pitch and roll movements, comprising a pitch mechanism, a roll mechanism, and a connecting mechanism. The pitch mechanism includes a pitch servo and a pitch linkage, while the roll mechanism includes a roll servo and a transmission gear. The connecting mechanism includes a universal joint and a universal joint limiter. The pitch servo drives the tail fin to pitch movement via the pitch linkage. The roll servo drives the universal joint to rotate via the transmission gear, with the tail end of the universal joint connected to the tail fin to complete the roll movement. The rotation center of the pitch mechanism coincides with the center of the universal joint, and the left and right swing degrees of freedom of the universal joint are limited by the universal joint limiter, achieving independent control of pitch and roll movements. This invention allows for completely independent roll and pitch movements, significantly reducing the control precision requirements of the motor. The invention has a simple structure and reasonable design. The single-plane tail fin structure of this invention has strong wind resistance during flight and also has advantages such as low inertial load on the motor and high drive efficiency.

This invention provides a piezoelectrically driven pipe wall crawling robot and its control method, including an arc-shaped annular piezoelectric vibrator. The arc-shaped annular piezoelectric vibrator is a symmetrical, slightly curved annular structure. Two sliding drive teeth are arranged on the outer side of the annular segment, and crawling drive teeth are arranged at both ends on the inner side. Four arc-shaped annular piezoelectric ceramic plates are arranged on each of the upper and lower sides of the annular segment. The polarization direction of the eight arc-shaped annular piezoelectric ceramic plates is along the thickness direction and points to the same side. It also includes an arc-shaped annular slide rail, which is a semi-circular annular structure with a central angle of 180°. The sliding drive teeth of the arc-shaped annular piezoelectric vibrator are in close contact with the inner side of the arc-shaped annular slide rail. This invention simultaneously solves the problems that existing piezoelectrically driven robots are mostly focused on planar precision motion and micro-nano manipulation, and cannot adapt to the needs of curved pipe wall crawling, high-altitude hovering, energy-saving self-locking, and miniaturized high-efficiency operation.

The invention discloses an expressway vehicle lane change trajectory prediction method fused with dynamic teaching, which belongs to the technical field of expressway vehicle lane change trajectory prediction, and comprises the following steps: acquiring trajectory data of an expressway vehicle by adopting video acquisition equipment, and preprocessing the trajectory data; feature information of a target vehicle and surrounding vehicles during lane changing is extracted based on the trajectory data, a multi-dimensional feature trajectory data set is constructed, standardization processing is carried out on the multi-dimensional feature trajectory data, and dimensionality reduction is carried out on high-dimensional features by adopting a principal component analysis method. According to the method, a dynamic teaching mechanism is introduced in the training stage, the teaching rate is adjusted in a self-adaptive mode according to the training round and the average loss, input is switched between a real label and model prediction in a probability mode, the accuracy and efficiency of model prediction can be effectively improved, and the training efficiency is improved. The method can be used for a highway intelligent management and control system to predict the vehicle track in real time, so that the driving safety and efficiency are improved.

The utility model relates to the technical field of cleaning supplies, in particular to a portable water squeezing mop which comprises a main rod, a holding and pressing mechanism fixed on the main rod and a transmission mechanism located on the main rod, a sliding block is connected between the holding and pressing mechanism and the transmission mechanism in a pivoted mode, and the sliding block is connected to the main rod in a sliding mode. The holding and pressing mechanism comprises a positioning rod pivoted to the main rod, an auxiliary rod pivoted to the main rod, a horizontal grab handle pivoted between the positioning rod and the auxiliary rod and a first transmission rod pivoted to the end of the horizontal grab handle, and the end, away from the horizontal grab handle, of the first transmission rod is pivoted to the sliding block. The positioning rod, the auxiliary rod and the horizontal grab handle form a parallelogram relation relative to the main rod; the first transmission rod and the auxiliary rod form an axial symmetry relation. According to the portable water squeezing mop, the mechanism of the grab handle is optimized, the pressing distance is short, the squeezing force transmission effect is good, the overall structure is compact, the occupied space is small, storage is convenient, more labor is saved and comfort is achieved when the mop is used, and the water squeezing effect is effectively improved.

The application belongs to the field of underwater robot control, and provides an underwater robot based on a focused ultrasonic underwater propeller and a control method thereof, which comprises a main cabin body, a drive control circuit and at least four underwater drive units arranged in the main cabin body, each underwater drive unit comprising an ultrasonic underwater propeller, the ultrasonic underwater propeller adopts a focused component, the working surface of the component is arc-shaped and forms a focus point, the arc-shaped working surface has a focus radius R and a focus angle θ, and the arc-shaped working surface is used for focusing generated ultrasonic waves to enhance underwater driving force. The problems of traditional underwater robots, such as large operation noise and obvious operation disturbance, are solved.

This invention discloses a method for generating a safety constraint trajectory for an autonomous vehicle, belonging to the field of autonomous driving technology. The method includes the following steps: S1, acquiring environmental state information, sensor observation information, and the vehicle's current state information; S2, constructing a safety constraint topology based on the risk uncertainty state vector, wherein the safety constraint topology includes a set of safe state nodes and a set of safe reachable state transition edges; S3, dynamically evolving the safety constraint topology based on the risk uncertainty state vector to update the set of safe state nodes and the set of safe reachable state transition edges; S4, generating the trajectory of the autonomous vehicle within the dynamically evolved safety constraint topology. This invention can effectively address uncertainties in the traffic environment, such as changes in the behavior of surrounding traffic participants and changes in the reliability of sensor information, thereby improving the robustness of the system.

The utility model relates to the technical field of agricultural machinery, and discloses a multi-station lifting bar type hayrake which comprises a traction rotation support and a traction beam connected to the traction rotation support, a connecting support is arranged at the other end of the traction beam, telescopic frames are arranged at the two ends of the connecting support respectively, and positioning supports are arranged on the telescopic frames. A swing support is hinged to the positioning supports, a hay raking device is arranged on the swing support, a swing driving mechanism capable of driving the swing support to swing at the angle larger than or equal to 90 degrees is installed on the positioning support on at least one side, and the swing support can swing at the angle larger than or equal to 90 degrees by arranging the swing driving mechanism. The hay raking devices are controlled to break through the angle limitation (generally smaller than 90 degrees) of a traditional hay raking machine, the hay raking devices on the two sides can conduct tedding operation at the same time, the requirement for synchronous treatment of multi-ridge pasture is met, the operation efficiency is remarkably improved, meanwhile, the multi-station switching function adapts to different terrains and operation modes, and the equipment application range is further expanded.

The utility model relates to the field of photovoltaic cleaning devices, in particular to a mechanical linkage photovoltaic water cleaning device which comprises two water wheels, a linkage device and a driving module, each water wheel is provided with a rotating shaft, the bottom end of each rotating shaft is connected with a brush, and the linkage device is connected with the driving module. The linkage device comprises synchronous wheels arranged on the two rotating shafts and a synchronous belt connected with the two synchronous wheels, and the driving module is matched with the water wheels so as to provide high-pressure water flow driving for at least one water wheel. According to the scheme, synchronous rotation of the brushes is achieved through the linkage device, and synchronous rotation of the two brushes is achieved. The problem that the rotating speeds of the brushes on the two sides are inconsistent due to factors such as non-uniform water flow distribution and manufacturing process errors is effectively solved, the situation that the cleaning strength of all areas on the surface of the photovoltaic panel is uneven is solved, stubborn dirt can be better removed, photovoltaic panel abrasion caused by excessive cleaning is avoided, and the service life of the photovoltaic panel is prolonged. And the service life of the photovoltaic panel is prolonged while the cleaning effect is ensured.

This application discloses a palletizing device and a battery swapping station. The palletizing device includes a support frame and a transfer arm mounted on the support frame. The transfer arm is telescopic relative to the support frame to transfer battery packs. It also includes a drive unit and a support tray. The output shaft of the drive unit is connected to the support tray. The support tray is mounted on the support frame and spaced horizontally from the transfer arm. Driven by the drive unit, the support tray can move vertically and has a support position above the upper surface of the transfer arm and an initial position below the upper surface of the transfer arm, allowing the battery pack to be transferred onto the support tray or the transfer arm. The lifting device of this application increases the conveying stroke of the transfer arm, making it suitable for battery packs with different conveying stroke requirements, thus meeting the battery swapping needs of battery swapping vehicles with different battery pack sizes.

This invention provides an autonomous driving route planning system and method. The system includes: a data acquisition module for collecting real-world traffic data, the current location information of the autonomous vehicle, and current environmental information; a data modeling module for generating a digital twin model and constructing virtual sensor, virtual vehicle, and virtual environment information; a decision-making module for performing initial path planning; subsequent collision risk detection; and path information adjustment based on the detection results; a path optimization module for performing a second path planning; and a driving control module for controlling the autonomous vehicle. This invention enables the virtual vehicle to drive in a virtual environment by establishing a digital twin model, and can adaptively adjust the parameters of the virtual vehicle and the virtual environment.

The invention discloses a lateral air inlet air duct structure and a ventilation device applying the same, and relates to the technical field of ventilation electrical appliances, the lateral air inlet air duct structure comprises a machine shell, a volute is arranged in the machine shell, the volute is provided with an air inlet and an air outlet, the air inlet is formed in the bottom of the machine shell, the air outlet is formed in one side of the machine shell, and a flow collecting space is formed in the volute; the air inlet and the air outlet are both communicated with the flow collecting space, an impeller assembly is arranged in the flow collecting space, a motor is installed on the volute, a rotating shaft of the impeller assembly is connected with the output end of the motor, and the impeller assembly corresponds to the air inlet; a lamp cover is connected below the machine shell, and an air inlet channel is formed between the lamp cover and the machine shell. And a lateral air inlet duct is formed between the lamp cover below the shell and the shell, so that the air volume loss is reduced. The impeller assembly is arranged corresponding to the air inlet and guides air into the flow collecting space during rotation, and the lateral air inlet amount is increased. When passing through the air inlet duct, airflow can dissipate heat for electrical elements on the lamp cover, and the working state of the elements is prevented from being affected by too high temperature.

The embodiment of the invention provides a driving resistance adjusting method and device, electronic equipment and a storage medium, and relates to the technical field of vehicle control. The method comprises the following steps: acquiring working condition characteristic data; sudden change working condition prediction is carried out based on the working condition characteristic data, and a driving resistance adjusting amount required for coping with the sudden change working condition is obtained; and adjusting the driving resistor based on the driving resistor adjusting quantity so as to perform resistance value switching based on the driving resistor adjusting quantity before the sudden change working condition occurs. According to the method, the driving resistance adjusting quantity is obtained based on sudden change working condition prediction, so that the driving resistance is dynamically adjusted in advance, the circuit fault risk caused by sudden change of working conditions is effectively reduced, and the output efficiency of the motor is improved.

This application provides an aperture driving device, a photographic device, and an electronic device. The aperture driving device includes a stator providing a stator opening; a mover providing an aperture opening with a variable size, the aperture opening being within the range of the stator opening; and an SMA assembly connected to the mover to drive the mover to change the aperture opening size. The SMA assembly includes a first SMA wire portion and a second SMA wire portion disposed opposite to each other, with one end of the first SMA wire portion and the other end connected to a positive and negative electrode, respectively. The deformation of the first SMA wire portion and the second SMA wire portion after being energized jointly drives the mover to move.

This invention belongs to the field of automated mobile platform technology, specifically a wheeled-tracked composite omnidirectional mobile platform. Four swing arms are symmetrically mounted on the vehicle body, with the left and right swing arms structurally mirror-image. Four Mecanum wheels on the four swing arms are diagonally mounted. The rotation of the tracked drive wheels and Mecanum wheels, as well as the pitching motion of the swing arms, are achieved through a drive system mounted on them and a pitching system within the vehicle body. The mobile platform can switch between tracked, omnidirectional wheeled, and legged movement modes through the pitching motion of the four swing arms. The drive motors of the drive system are installed inside the Mecanum wheels, resulting in a relatively smaller vehicle body size and increased space utilization of the entire robotic mobile platform. This invention provides a mobile platform for robotic patrol and reconnaissance work, particularly suitable for various complex unstructured environments, and features modularity, compactness, flexible movement, and wide adaptability.

The application provides a parallel computing method for gas-solid simulation, which comprises the following steps: forming a geometric boundary as a solid by building a plurality of static geometric shape units according to a multiphase complex boundary condition; setting an initial state of a system to be simulated, and adopting a spherical or ellipsoidal particle model for a gas particle; performing spatial decomposition on the system to be simulated to obtain a plurality of sub-regions, each of which comprises an interior and a boundary, the interior is simulated by a hard sphere, and the boundary is simulated by a pseudo-particle, each of the sub-regions is divided into a plurality of grids, a mapping relationship between the particles and the grids is established, and the geometric boundary in each of the grids is calculated; within a set time step, updating particle information based on event driving and in view of particle collision in the interior of each of the sub-regions and particle collision between the particles and the geometric boundary; updating the particle information based on time driving and in view of particle collision on the boundary of each of the sub-regions and particle collision between the particles and the geometric boundary; and outputting a simulation result.

The application provides a radio frequency driving circuit and a radio frequency power supply, wherein the radio frequency driving circuit comprises a driving module and a control module; the driving module is used for providing a driving signal to the gate of a radio frequency transistor, so as to drive the radio frequency transistor to periodically turn on and turn off, and make the power amplifier circuit perform radio frequency output; and the control module is used for superimposing an amplified adjusting signal on the gate of the radio frequency transistor, so as to adjust the driving signal, and thus control the drain-source current of the radio frequency transistor. The scheme can effectively improve the driving efficiency of the power amplifier circuit.

The application specifically relates to the technical field of household appliances, and particularly relates to a sweeper, which comprises a base provided with a rolling brush cavity and a battery cavity on a side close to the ground, the rolling brush cavity and the battery cavity are adjacently arranged along a first direction; a rolling brush mechanism is movably installed in the rolling brush cavity; an installation cavity is arranged on a side of the base far from the ground and between the rolling brush cavity and the battery cavity; the installation cavity is in communication with the rolling brush cavity; a driving mechanism is arranged in the installation cavity; a driving end of the driving mechanism extends into the rolling brush cavity and is connected with the rolling brush mechanism; under the driving effect of the driving mechanism, the rolling brush mechanism moves along a third direction. The driving mechanism is directly arranged in the installation cavity, the space of the base is fully utilized, the space utilization rate is improved, and the overall volume of the transmission mechanism can be reduced. The volume of the driving motor and the transmission mechanism is large, the compact layout of the sweeper in the longitudinal height can be reduced, and the thickness of the sweeper can be controlled within a certain range.

The application relates to the electrical field and discloses an industrial vehicle lane driving safety control system and a control method thereof. The system comprises: a plurality of magnetic switch groups, which are installed side by side on a vehicle front cross beam; a plurality of ground magnetic nails, which are arranged on a lane ground and correspond to positions of the magnetic switch groups; and a controller, which is used for controlling a driving speed of the vehicle in the lane by using interaction between the magnetic switch groups and the ground magnetic nails during vehicle forward driving or backward driving. Thus, human factors can be avoided, the automation degree of the vehicle is improved, lane driving safety can be effectively improved, driving and carrying efficiency is improved, guide rails and auxiliary wheels on both sides of the vehicle are effectively protected, and personnel and goods on both sides are protected.

This invention discloses a dual-piezoelectric tube driven inertial motor and its control method, along with a scanning probe microscope, relating to the field of piezoelectric tube technology. The invention includes a base, a first piezoelectric tube, a second piezoelectric tube, and a U-shaped sliding body. The first and second piezoelectric tubes are parallel to each other along their axes, with one end fixed to the base and the other end free. The two parallel arms of the U-shaped sliding body, referred to as the left and right sliding rods, are elastically connected via a junction at the bottom of the U-shaped sliding body. The left and right sliding rods are coaxially inserted into the inner walls of the first and second piezoelectric tubes, respectively. This invention not only ensures that the two sliding rods consistently and stably abut against the inner cavities of their respective piezoelectric tubes, guaranteeing effective transmission of driving force, but also improves the overall mechanism's motion accuracy, load-bearing capacity, and anti-interference capability through the coordinated and alternating operation of the dual-drive piezoelectric tubes, laying a structural foundation for achieving high-precision and high-stability stepping motion.

The application provides a vehicle U-turn control method and device and a vehicle. The application relates to the technical field of automatic driving. When it is determined that a vehicle is in a driving-restricted area and a U-turn triggering condition is met, a target U-turn path and a U-turn inquiry request are generated. In response to a confirmation operation of a user on the U-turn inquiry request, the vehicle is controlled to U-turn according to the target U-turn path. The driving-restricted area refers to an area in which a road width of a current position is less than a preset width and a front area is impassable. The U-turn triggering condition is determined based on at least one of a vehicle speed, a gear shifting frequency and a parking waiting time. The method is used to reduce U-turn time and complexity and improve U-turn efficiency of the vehicle in the driving-restricted area.

The utility model discloses a kind of flapping-wing aircraft double-wing amplitude differential mechanisms, including motor, steering wheel, rack and two places rocker arm, the inside of each rocker arm is provided with swing straight slot;Limiting frame is provided on rack, and limiting frame is provided with amplitude modulation arc groove, corresponding swing straight slot and amplitude modulation arc groove are provided with amplitude modulation fixed pin, two places amplitude modulation fixed pin are fixedly connected with transmission connecting rod, the other end of each transmission connecting rod is rotatably connected with transmission gear, amplitude modulation arc groove is provided with swing shaft on each transmission gear, and two places transmission gear are engaged with output gear wheel. The utility model's limiting frame can change the power arm stress position of rocker arm by amplitude modulation fixed pin, to change the vibration amplitude of two places rocker arm;Motor drives two places transmission gear to rotate by output gear wheel, and transmission gear drives two places rocker arm to reciprocate by transmission connecting rod, ensure that the motion frequency of two places rocker arm is consistent, while realizing driving main wing to carry out fan operation.

A spatial 6R multiple metamorphic mechanism, comprising two connecting rods and two kinematic chains for connecting the front and rear ends of the two connecting rods. The two kinematic chains are respectively two triangular rods connected by revolute pairs B and E; the front kinematic chain is connected to the front ends of the two connecting rods by revolute pairs D and F; and the rear kinematic chain is connected to the rear ends of the two connecting rods by revolute pairs A and C. The two sides of the revolute pairs B, E, D and F are provided with mechanical limiters. When the mechanism is in the extension and retraction movement and the mechanical limiters on the two sides of the revolute pairs B, E and D are in contact, the mechanism is in the first position bifurcation point, at which time the mechanism has both extension and retraction and translation movement tendencies. When the driving θ is counterclockwise, the mechanism will enter the translation movement mode; until the revolute pair A is counterclockwise rotated to θ=180°, at which time the mechanism has both translation and rotation movement tendencies. Thus, the mechanism can realize three different movement modes of extension, translation and rotation and mode switching.

The application discloses a lower limb auxiliary driving mechanism and a robot, which comprises a thigh assembly and a lower leg assembly connected with the thigh assembly, and a connecting end of a thigh connecting piece two and the lower leg assembly forms a knee joint. In the application, a constant force load mechanism is arranged on the thigh assembly, constant tension of a spring is converted into a compensation torque acting on the knee joint, so that the compensation torque can directly offset part or all of the bending moment generated by the weight of the lower limb on the knee joint, thereby realizing accurate compensation of the static load of the knee joint, reducing the driving burden when the joint maintains a posture, and the constant force load spring serves as a parallel auxiliary execution mechanism and jointly bears the load of the knee joint with a motor driving system. Through the parallel sharing mode, the joint load originally borne by the motor can be reasonably distributed, the motor works in a relatively stable and high-efficiency interval more, peak load is reduced, current impact is reduced, and overall driving efficiency is improved.

The invention discloses a traffic light queuing waiting reminding system and method, and relates to the technical field of traffic guidance, and the method comprises the steps of S1, vehicle positioning and data acquisition, S2, dynamic parameter calculation, S3, intelligent pre-judgment, S4, layered reminding triggering, S5, feedback optimization, and S6, system collaboration. In combination with a layered reminding mechanism, the starting delay time of queuing vehicles is shortened, specifically, the system can dynamically adjust a reminding strategy according to a real-time traffic state to ensure that a motorcade quickly and orderly passes through an intersection in a green light period, and meanwhile, a vehicle-road cooperation mechanism feeds back the vehicle starting state to a signal control system in real time, so that the driving safety of the vehicles is improved. Intelligent optimization of the green light time is achieved, waste of the green light time is avoided, energy consumption and tail gas emission which are increased due to frequent starting and stopping of vehicles are avoided, the congestion time of a single intersection is shortened through the design, and the traffic capacity of the whole road network can be improved through chain reaction.

This invention provides a valve device that improves the driving efficiency of the valve core by suppressing the frictional resistance during rotor rotation. The driving part (5) of the valve device (1) includes: a cylindrical shell (50); an external thread (55) serving as a driving shaft; an internal thread component (56) engaging with the external thread; a guide component (54) fixedly disposed in the cylindrical shell and guiding the internal thread component forward and backward; and a bearing component (53) disposed inside the cylindrical shell and providing rotational support for the external thread. A cylindrical first shaft portion (55b) and a second shaft portion (55c) (shaft portion) are respectively provided at both ends of the external thread. A first bearing hole (53c1) and a second bearing hole (54a) (bottomed concave hole) are respectively provided at the shaft core position of the external thread on the guide component and the bearing component (53). The first shaft portion (55b) is inserted into the first bearing hole (53c1), and the second shaft portion (55c) is inserted into the second bearing hole (54a), thereby providing rotational support for the external thread.