47results about How to "Decrease the relative speed of motion" patented technology

The invention relates to the fields of gas compression, fluid conveyance and evacuation, in particular to a rotary compressor having a translational piston. The translational rotary compression device comprises a cylinder body, a translational piston and an eccentric rotor, wherein the eccentric rotor is arranged inside the cylinder body, the translational piston is arranged on the eccentric rotor, the translational piston is movably connected with the eccentric rotor, a rotating center of the eccentric rotor is concentric with the cylinder body, the outer lateral surface of the translational piston is tangential to the inner lateral surface of a round cylinder body, a crescent working chamber is formed inside the compressor, an inner wall of the cylinder body is articulated with a sliding plate, a sliding plate groove is arranged in a radial direction of the translational piston, the sliding plate is passed through the wording chamber to be extended into the sliding plate groove, the sliding plate is connected with the sliding plate groove in a sliding way, the sliding plate divides the working chamber into an expansion chamber and a compression chamber, and the expansion chamber and the compression chamber are respectively provided with a suction port and an exhaust port. The compressor has the advantages of obviously improving volumetric efficiency, improving reliability of the mechanism, reducing friction loss and improving mechanical efficiency.

The invention provides a magnetron sputtering coating method and system, belonging to the technical field of display. The magnetron sputtering coating system comprises a sputtering chamber, a target set, a substrate carrier and a transmission device, wherein the target set is arranged in the sputtering chamber and formed by splicing a plurality of targets; the substrate carrier is arranged opposite the target set and used for carrying a film-forming substrate; and the transmission device is used for driving the substrate carrier to reciprocate in the target arrangement direction. The technical scheme provided by the invention can effectively enhance the magnetron sputtering coating uniformity, thereby ensuring the performance and quality of the display substrate.

The invention relates to a method used for reducing oxygen content of czochralski silicon. The method comprises following steps: the power of a bottom auxiliary heater is adjusted in crystal pulling process, crucible rotating speed is adjusted, argon flow rate and furnace pressure are adjusted. According to the method, no new device is used, effects of thermal field existing parts are achieved fully via technological parameter adjustment and combination based on an original thermal field; the method is reasonable and simple compared with a conventional oxygen reducing method; no other impurity is introduced in the whole crystal pulling process, and the other performance of monocrystalline silicon is not influenced; cost is low; and effect is excellent.

The invention provides a refrigerator compressor with a filter, which comprises a housing, a core and a core support structure, wherein the core comprises a support, a cylinder body, a crank shaft, a motor stator and a motor rotor, the cylinder body is connected with the support, the core is installed in the housing through the core support structure, and an oil sump is arranged below the core; the crank shaft comprises a crank shaft part, a balance part and a main shaft part, and the crank shaft is provided with an oil supply channel which comprises an upper oil hole, an outer oil groove, a middle oil hole and an oil suction cavity; an oil suction pipe is connected with the lower end of the crank shaft, the filter which comprises an upper ring plate, a filter screen and a fixed frame is arranged in the oil sump, and the filter is connected with a lower housing through supporting legs so that the end of the oil suction pipe penetrates through the opening of the filter screen and extends into the filter screen. The refrigerator compressor with the filter has the characteristics that lubricating oil supplied to links, pistons and other moving parts from the oil suction pipe is filtered, which can greatly reduce damage of solid impurities in the lubricating oil to the moving parts and is favorable to prolonging the service life of the refrigerator compressor; the refrigerator compressor with the filter has a simple structure, can be installed easily and has good using effects.

The invention discloses a buffering despinning damping device for satellite docking, comprising a split buffering structure and a despinning damping structure; the split buffering structure comprises a buffering body, a linear spring damper, a split structure and an arrival sensor; the despinning damping structure comprises a despinning body, a rotary transmission disc and a rotary motor. The buffering despinning damper is applicable to satellite capture under weak impact condition, and high relative speed and large angular speed tolerance can be provided for a capturing mechanism; the split buffering structure arranged in the damping device experiences collision buffering with the inner wall of an engine nozzle of a target satellite, and relative movement speed in the collision process is reduced; the spinning damping structure that drives the split buffering structure in rotation is provided, and the relative angular speed of the split buffering structure to the inner wall of the engine nozzle of the target satellite is thus reduced.

The invention relates to the field of gas compression, fluid transportation and vacuum-pumping, in particular to a double-cylinder translational rotary compressor. The double-cylinder translational rotary compressor comprises a cylinder body, a crankshaft and two translational pistons, wherein an inner chamber of the cylinder body is divided into a left chamber and a right chamber the middle parts of which are communicated with each other; the crankshaft is provided with two eccentric structures which run through the left chamber and the right chamber; the two translational pistons are movably connected with the two eccentric structures of the crankshaft respectively; outer side faces of the two translational pistons are tangent with inner side faces of the left chamber and the right chamber respectively, so as to form a left crescent-shaped working chamber and a right crescent-shaped working chamber; sliding plates are hinged to insides of the left chamber and the right chamber respectively; sliding plate grooves are arranged on the two translational pistons respectively; two sliding plates are extended into the sliding plate grooves respectively, and divide the left working chamber and the right working chamber into an expansion chamber and a compression chamber respectively; and feed openings and discharge openings are arranged on the expansion chamber and the compression chamber respectively. The double-cylinder translational rotary compressor has the advantages of obviously improving the volumetric efficiency, improving the mechanical reliability and the mechanical efficiency, and reducing the friction loss.

The invention discloses a self-buffering-type gas-liquid mixing multi-stage ejection mechanism. Gas is taken as a power source; oil fluid is taken as a pressure transmission medium; the gas-liquid mixing multi-stage ejection mechanism is formed by combining a mode of mutual sliding friction match of multiple stages of piston cylinders; relative moving speed of stages of moving parts of the ejection mechanism is reduced; the sealing difficulty during high-speed ejection is effectively reduced, and high-speed ejection is realized in a limited moving journey; a throttling buffer structure, oil fluid buffering and an unloading groove are combined, so that a self-buffering function of the multi-stage ejection mechanism is realized; and an oil charging opening is formed so that oil charging and oil exchanging maintenance is facilitated. The self-buffering-type gas-liquid mixing multi-stage ejection mechanism can be applied to fields of military and civil ejection such as shipboard aircraft, missiles, unmanned planes and ejection experiment devices; the sealing performance is reliable; ejection capable of realizing a self-buffering function can be provided under a condition of limited assembly space; the efficiency is high; and the controllability is good.

The invention relates to the air compression, fluid conveying and the evacuation fields, in particular to a rotary compression machine with a translational piston; the integral translational rotary compression device comprises a cylinder body, a crankshaft, a crankcase, an electromotor component, a sliding plate, a translational piston; one end of the crankshaft is provided with an eccentric rotor; the rotary center of the eccentric rotor is concentric with the cylinder body and movably arranged on the eccentric rotor; the lateral surface of the eccentric rotor is tangent with the inner lateral surface of the cylinder body, so as to form a crescent-shaped operation cavity; one end of the sliding plate is hinged on the inner wall of the cylinder body; a sliding plate groove is arranged on the translational piston in the radial direction; the other end of the sliding plate is extended to the sliding plate groove through the operation cavity; the operation cavity is divided into an expansion cavity and a compression cavity by the sliding plate; a suction port and a discharge port are respectively on the expansion cavity and the compression cavity; the electromotor component is arranged on the right end of the cylinder body; the electromotor component includes a rotor and a stator; the other end of the crankshaft is threaded through the crankcase; the crankshaft is extended rightwards to be fixedly connected with the rotor. The rotary compression machine with a translational piston has the advantages of simple structure and high operation efficiency.

The invention relates to a translational rotor compressor, which comprises a rotor 1, a cylinder body 2, a sliding blade 3 and an end cover, and is characterized in that a flat rotor chute 4 is arranged on the rotor 1; a flat cylinder body chute 5 is arranged on the cylinder body 2; and the sliding blade 3 has a T-shaped structure or an L-shaped structure, and consists of a radial bluff body 3a and a tangent bluff body 3b which are perpendicular to each other, wherein the radial bluff body 3a is arranged inside the rotor chute 4 and is matched with the rotor chute 4 in a sliding way, and the tangent bluff body 3b is arranged inside the cylinder body chute 5 and is matched with the tangent bluff body 3b in a sliding way. The rotor 1 is limited by the sliding blade 3 and only performs translational rotation, and the swinging radius of each mass point on the rotor 1 is equal to the eccentric distance of the rotor 1 opposite to a cylinder hole on the cylinder body 2; and because the valueof the eccentric distance is small, the relative kinematic velocity of the rotor 1 relative to the end cover and the cylinder body 2 is small as well, namely the friction and the abrasion between therotor 1 and the end cover and between the rotor 1 and the cylinder body 2 are small. Moreover, the sliding blade 3 and the rotor 1 always adopt the means of surface contact, so that the sealing reliability of the translational rotor compressor is higher than that of line contact.

The invention belongs to the technical field of coating equipment and particularly relates to a high-speed coiled material powder spray device, a working method thereof, a power spray production lineand a power spray line applicable to rapid color change. The powder spray device comprises a power spray cavity with high-pressure static electricity. The power spray cavity is suitable for allowing airflow to pass through so that powder coating in the power spray cavity can be driven to move in the same direction as a moving workpiece. A corona space is suitable for being form in the power spraycavity so that the powder coating can adsorb to the surface of the workpiece through static electricity. By means of the powder spray device, the relative movement speed of the power coating and the workpiece is reduced; then, the powder coating is sprayed to the surface of the workpiece through the static electricity; the phenomenon that adsorption of the powder coating is influenced when the moving speed of the workpiece is high is avoided; and the powder application effect of the workpiece is improved.

The invention relates to the fields of gas compression, fluid conveyance and evacuation, in particular to a birotor translational rotary compressor. The birotor translational rotary compressor comprises a cylinder body, two translational pistons and two eccentric rotors, wherein the cylinder body comprises two round through holes, the joints of the two through holes are communicated with each other, the two translational pistons are respectively arranged on the eccentric rotors, the outer lateral surfaces of the translational pistons are tangential to the inner lateral surfaces of the through holes; the two translational pistons are further provided with a sliding plate groove respectively, the two sliding plate grooves face to the joints respectively, a sliding plate is arranged between the two sliding plate grooves, the two ends of the sliding plate are respectively arranged in the sliding plate grooves in a sliding way, the sliding plate divides two working chambers into an expansion chamber and a compression chamber, and the expansion chamber and the compression chamber are respectively provided with a suction port and an exhaust port. The compressor has the advantages of reducing leakage, obviously improving volumetric efficiency, and obtaining higher output pressure with fewer components and simple process, and having foundation for batch production.

The invention relates to a seedling feeding and fetching interlocking mechanism system for a high speed seedling transplanting machine, which belongs to the technology field of the seedling transplanting machine. The system comprises a seedling feeding mechanism, a seedling fetching mechanism and a transmission mechanic, wherein the transmission mechanism comprises a gear box connected with the seedling feeding mechanism and the seedling fetching mechanism, and a first output shaft, a second output shaft, a third output shaft and an input shaft are all arranged on the gear box; the middle part of the first output shaft, and the input shaft form a first kinematic pair, and the both ends thereof and the seedling fetching mechanism form a second kinematic pair; one end of the third output shaft, and the seedling feeding mechanism form a third kinematic pair; a first eccentric gear is arranged on the first output shaft, a second eccentric gear meshed with the first eccentric gear, and a first circular gear are arranged on the second output shaft, and a second circular gear meshed with the first circular gear is arranged on the third output shaft. The system can effectively reduce the speed of relative movement and the position error between the seedling feeding mechanism and the seedling fetching mechanism through speed changing seedling feeding and speed reducing seedling fetching, and thereby the quality and the precision for seedling fetching can be improved.

The invention relates to the air compression, fluid conveying and the evacuation fields, in particular to a rotary compression machine with a translational piston; the machine head device of the translational rotary compression device comprises a cylinder body, a crankshaft, a transmission wheel, a sliding plate, a translational piston; the transmission wheel is arranged on one end of the crankshaft; the middle part of the crankshaft is provided with an eccentric rotor; the rotary center of the eccentric rotor is concentric with the cylinder body; the translational piston is arranged on the eccentric rotor and is movably connected with the eccentric rotor; the lateral surface of the translational piston is tangent with the inner lateral surface of the cylinder body, so as to form a crescent-shaped operation cavity; one end of the sliding plate is hinged on the inner wall of the cylinder body; a sliding plate groove is arranged on the translational piston in the radial direction; the other end of the sliding plate is extended to the sliding plate groove through the operation cavity; the sliding plate is movably connected with the sliding plate groove the operation cavity is divided into an expansion cavity and a compression cavity by the sliding plate; a suction port and a discharge port are respectively on the expansion cavity and the compression cavity; The rotary compression machine with a translational piston has the advantages of simple structure and high operation efficiency.

The invention discloses a rotary compressor and an air conditioner with the same. The rotary compressor comprises a housing, a driver, an air cylinder, a main bearing, an auxiliary bearing, a crankshaft, a first slip sheet and a second slip sheet, wherein the driver is arranged in the housing; the air cylinder is arranged in the housing; a first slip sheet groove and a second slip sheet groove are formed in the air cylinder; the main bearing and the auxiliary bearing are arranged at the top and the bottom of the air cylinder respectively and define a chamber along with the air cylinder; the crankshaft is driven by the driver to rotate and penetrates through the main bearing and the auxiliary bearing; a piston is eccentrically sleeved on the crankshaft; the piston is rotatable relative to the crankshaft; the first slip sheet and the second slip sheet are movably arranged in the first slip sheet groove and the second slip sheet groove respectively; the inner end of the first slip sheet extends into the chamber and is connected with the piston to enable the first slip sheet to swing at a predefined angle alpha which is not smaller than -1.1*atan (e / R) and not greater than 1.1*atan (e / R); the inner end of the second slip sheet is separably matched with the outer circumferential surface of the piston. According to the rotary compressor, the efficiency of the rotary compressor is improved.

The invention relates to a translational rotor compressor, which comprises a rotor 1, a cylinder body 2, a sliding blade 3 and an end cover, and is characterized in that a flat rotor chute 4 is arranged on the rotor 1; a flat cylinder body chute 5 is arranged on the cylinder body 2; and the sliding blade 3 has a T-shaped structure or an L-shaped structure, and consists of a radial bluff body 3a and a tangent bluff body 3b which are perpendicular to each other, wherein the radial bluff body 3a is arranged inside the rotor chute 4 and is matched with the rotor chute 4 in a sliding way, and the tangent bluff body 3b is arranged inside the cylinder body chute 5 and is matched with the tangent bluff body 3b in a sliding way. The rotor 1 is limited by the sliding blade 3 and only performs translational rotation, and the swinging radius of each mass point on the rotor 1 is equal to the eccentric distance of the rotor 1 opposite to a cylinder hole on the cylinder body 2; and because the value of the eccentric distance is small, the relative kinematic velocity of the rotor 1 relative to the end cover and the cylinder body 2 is small as well, namely the friction and the abrasion between the rotor 1 and the end cover and between the rotor 1 and the cylinder body 2 are small. Moreover, the sliding blade 3 and the rotor 1 always adopt the means of surface contact, so that the sealing reliability of the translational rotor compressor is higher than that of line contact.

The invention discloses a device for reducing frictional resistance and a method for reducing viscous frictional resistance of fluid by means of the device. The device comprises rolling bodies and a rolling skin, and the rolling bodies are inlaid into the surface of the rolling skin. The method comprises the step that the surface of a moving object is covered with the rolling skin which is provided with the rolling bodies in an inlaid mode on the relative movement interface of the moving object and the fluid. Compared with the prior art, the device and the method have the advantages that the relative movement surface of the moving object and the fluid is covered with a layer of the rolling skin, relative movement of the fluid drives balls or rollers on the surface of the skin to rotate, therefore, the relative movement speed between the fluid and the object surface is decreased, and the viscous resistance of the fluid is decreased. The method is suitable for the surfaces of objects onwhich the fluid and a solid relatively move, such as the surfaces of all objects moving in the fluid or the inner surfaces of pipelines in which the fluid moves and has the wide application prospect in the fields of high-speed transportation and transportation.

The invention relates to a drivable rotary steel collar assembly of which the inside and outside are both supported by a spherical rolling path. The drivable rotary steel collar assembly comprises rotary steel collar assembly bodies and a steel collar plate, the rotary steel collar assembly bodies are sleeved with mounting holes, are then pressed on the steel collar plate through a pressing plateand comprise motor assemblies and steel collar assemblies, the motor assemblies are composed of motor stators, motor rotors, motor shells and motor lids, the steel collar assemblies are composed of steel wire ring running paths, steel collar outer rings, steel collar inner rings and balls, the steel collar outer rings are sleeved with the mounting holes, the balls are clamped between the steel collar outer rings and the steel collar inner rings to constitute steel collar bearings, the steel wire ring running paths are pressed in upper ports of the steel collar inner rings, lower ports of the steel collar inner rings are a certain distance away from lower ports of the steel collar outer rings, and the motor rotors sleeve outer circles of the lower ends of the steel collar inner rings. By means of the drivable rotary steel collar assembly of which the inside and outside are both supported by the spherical rolling path, the relative motion speed between steel wire rings and steel collarsis reduced so that the circular motion speed of the steel wire rings can satisfy high-speed running of a spindle, and meanwhile, the service life of the steel collars and the steel wire rings is alsoprolonged.

The invention relates to a totally-closed ink brush cleaning device. The totally-closed ink brush cleaning device comprises a clear water cylinder (1) and a dirty water cylinder (2). An ink brush cylinder (3) communicated with the clear water cylinder (1) is arranged in the clear water cylinder (1) in a sleeved mode, and the ink brush cylinder (3) is communicated with the dirty water cylinder (2). The ink brush cylinder (3) is provided with a fixer (5) used for clamping an ink brush (4). The clear water cylinder (1) is further provided with a controller used for making the ink brush cylinder (3) to rotate on the axis. The totally-closed ink brush cleaning device is simple in structure, the ink brush can be cleaned rapidly, and a good cleaning effect can be achieved.

The invention relates to a low-noise high-efficiency food processing machine, which comprises a machine base and a stirring cup, wherein a motor is arranged in the machine base; the stirring cup comprises a cup body and a crushing knife; the crushing knife comprises a crushing blade and a knife shaft; the crushing blade is positioned in a cup body; the knife shaft penetrates through the cup body and is driven to rotate by a motor; the crushing blade comprises a wing root and a blade wing; the blade wing comprises a crushing wing and an extension wing positioned at the tail end of the crushingwing; the extension wing extends backwards along the rotation direction of the blade wing; a cutting edge is formed on the outer side of the blade wing blade; a cutting point is formed on the tail endof the extension wing; and the radius from at least one point in the middle of cutting edge to the center of the wing root is the maximum radius from the cutting edge to the center of the wing root,and the radius from the cutting point to the center of the wing root is no larger than the maximum radius.. According to the machine, the extension wing is arranged, the space formed by the crushing wing can be occupied after the crushing blade performs cutting and rotating, so that the crushing blade is prevented from generating vortex, the kinetic energy release of food materials after being through the crushing blade is relieved, the noise pollution caused by the vortex generation is reduced, and at the same time, the crushing performance is improved.

The invention belongs to the field of water coolers, and particularly relates to an industrial water-cooled water chiller. The industrial water-cooled water chiller comprises a refrigeration cycle, acondenser water-cooled heat dissipation cycle and an evaporator cold water control cycle, and a thermostatic expansion valve in the refrigeration cycle comprises a valve shell, an ejector rod A, a diaphragm, a sealing cover, a spoiler, an ejector rod B, an adjusting tool and the like; a fixed block is mounted between an accommodating groove C for accommodating a refrigerant in the valve shell anda through groove for distribution of the refrigerant, and a circular groove A and a circular groove B for making the accommodating groove C communicate with the through groove are formed in the fixedblock; and two extendable rods always keep effective compression due to the self-locking function of the cooperation of two worms and worm wheels, so that the two extendable rods drive two pressing wheels to effectively limit the degree of freedom of the ejector rod B in the direction perpendicular to the movement direction of the ejector rod B, and the inherent frequency of the ejector rod B is increased, so that the ejector rod B is not prone to vibration on a plane perpendicular to the moving direction of the ejector rod B, and squeal is effectively avoided.

The invention relates to a steel collar assembly capable of being driven to rotate and supported by a roller. The steel collar assembly comprises a steel collar plate, a steel collar, a steel collar supporting part, roller combination parts and a driving motor assembly. The upper surface of the steel collar plate is provided with three roller combination parts which are on the same plane and are evenly distributed relative to a steel collar center line, the three roller combination parts and the steel collar supporting part disposed on the lower portion of the steel collar are supported through a roller path and matched to form a rotating assembly; the driving motor assembly includes a rotor and a stator assembly, and after the stator assembly and the rotor are fixed, the rotating assemblyis driven to rotate to drive the steel collar to rotate. According to the steel collar assembly, during spinning, since the rotation of the steel collar is the rotary movement in the same direction as a steel wire ring, the rotary movement of the steel collar replaces most of circular motion of the steel wire ring on the steel collar, so that the relative movement speed between the steel wire ring and the steel collar is reduced, and the circular motion speed of the steel wire ring can meet the high-speed operation of a spindle during the spinning process.

The invention relates to the air compression, fluid conveying and the evacuation fields, in particular to a rotary compression machine with a translational piston; the machine head device of the translational rotary compression device comprises a cylinder body, a crankshaft, a transmission wheel, a sliding plate, a translational piston; the transmission wheel is arranged on one end of the crankshaft; the middle part of the crankshaft is provided with an eccentric rotor; the rotary center of the eccentric rotor is concentric with the cylinder body; the translational piston is arranged on the eccentric rotor and is movably connected with the eccentric rotor; the lateral surface of the translational piston is tangent with the inner lateral surface of the cylinder body, so as to form a crescent-shaped operation cavity; one end of the sliding plate is hinged on the inner wall of the cylinder body; a sliding plate groove is arranged on the translational piston in the radial direction; the other end of the sliding plate is extended to the sliding plate groove through the operation cavity; the sliding plate is movably connected with the sliding plate groove the operation cavity is dividedinto an expansion cavity and a compression cavity by the sliding plate; a suction port and a discharge port are respectively on the expansion cavity and the compression cavity; The rotary compressionmachine with a translational piston has the advantages of simple structure and high operation efficiency.

The invention discloses a swash plate type hydraulic axial plunger pump / motor heavy-load sliding shoe pair friction-reducing disc in order to overcome technical defects of sliding shoe pairs. Slidingshoes slide freely on the outer surface of a rotating disc on the top of a friction-reducing disc body, or the sliding shoes are fixedly connected with the rotating disc; under driving of a friction force between the sliding shoes and the surface of the rotating disc, due to the support action of bottom balls and side balls, the rotating disc and an intermediate body rotate together with the sliding shoes, so that sliding movement between the sliding shoes in a sliding shoe pair and a swash plate surface is partially or completely converted into rolling movement between the side balls and thebottom balls, the relative movement speed between the sliding shoes and the rotating disc is also decreased at the same time, and thus the purpose of reducing the friction power loss of the sliding shoe pair is achieved. The friction-reducing disc is completely immersed in hydraulic oil during work for thorough lubrication and cooling, and since the bearing form of combined action of the balls andstatic pressure support is adopted, the friction-reducing disc can obtain a long service life through reasonable design and is also convenient to maintain and replace when worn.

The invention discloses a conveyor belt monitoring device based on image and photoelectric information fusion. The conveyor belt monitoring device comprises a conveyor belt body, a photoelectric emitter and a photoelectric receiver, and is characterized in that the conveyor belt body comprises a belt body and at least two rotating shafts, the rotating shafts are sleeved with the belt body, and the rotating shafts rotate under the action of an external power source; and the monitoring device further comprises a base plate, the base plate is fixedly arranged in the space defined by the belt body, the base plate is fixed to an external rack through a hard rod piece, a sliding groove is formed in the upper surface of the base plate and arranged in the conveying direction of the conveying belt, and an upper sliding block is slidably connected into the sliding groove. The conveyor belt monitoring device has the advantages that an upper limiting shaft and a lower limiting shaft are both fixedly connected with the external rack, the movement speed of the belt body on the side, close to the rotating shaft, of receding grooves is directly controlled by the rotating shaft and cannot be changed, but the movement speed of the belt body between the two receding grooves can be adjusted, so that the movement speed of workpieces is adjusted, and the aim of adjusting the distance between the multiple workpieces is achieved.

The new type compressor is constituted by a cylinder assembly, which consists of driving shaft, cylinder, front and back caps, servo ring and isolating blade, installed in the casing cavity. It features the concentric driving shaft steps, the servo ring inside the cylinder, the eccentric driving shaft and the silating blade with outer end hinged with the servo ring and inner end inserted inside the straight runner. During the rotation of the driving shaft, the isolating blade rotates the servo ring to suck in and extrude out cold medium. The compressor has no eccentric vibration, and thus good high speed performance.