Mechanical transmission system: an important part of the machine tool, mainly composed ofBall screwThe ball screw is integrated with the moving shaft during transmission. The machine tool useselectric machineryAs transmission.The role of mechanical transmission is to transmit motion and force. Common types of mechanical transmission aregearDrive, worm gear drive, belt driveChain drive, gear train.
The role of mechanical transmission: the role of mechanical transmission is to transmit movement and force. The types of common mechanical transmission systems are gear transmissionWorm gearWorm drive, belt drive, chain drive, gear train, etc.[1]
Belt drive
According to thesectionDue to different shapes, belts can be divided into flat belts, V-belts and special belts (V-belts, circular belts, etc.). The belt drive is simple in structure, smooth in transmission, capable of buffering and vibration absorption, capable of transmitting power between large shaft spacing and multiple shafts, and cheap in costlubricationEasy maintenance.However, accurate transmission ratio cannot be guaranteed and transmission efficiency is low.The belt transmission is mainly used for the long-distance transmission occasions of medium and small power with stable transmission and less strict transmission ratio requirements.
Chain drive
Chain drive is a kind of meshing drive in which a chain is used as a flexible pulling element between two or more sprockets.Compared with belt drive, the main advantages of chain drive are: no sliding;High efficiency, η≈ 98%; no great tension is requiredloadSmaller;It can be used in the environment with high temperature and humidity.The main disadvantages are: it can only be used for transmission between parallel shafts;Instantaneous speed is uneven, and the belt transmission is not as smooth when running at high speed;Not suitable forloadApplication in transmission with great changes and rapid reverse;Noise during operation.Chain drive andgearCompared with transmission, its main characteristics are: lower requirements for manufacturing and installation accuracy;When the center distance is large, the transmission structure is simple;Instantaneous chain speed and instantaneous transmission ratio are not constant, and transmission smoothness is poor.In addition to being widely used as transmission with fixed transmission ratio, chain drive can also be made into stepped chain typeTransmissionAnd stepless chain transmission.[1]
worm drive
Mechanical transmission system
wormThe transmission is used to transmit the rotary motion between the staggered shafts.In most cases, the two axes are mutually perpendicular in space.worm driveIts main advantages are compact structure, smooth operation, no noise, small shock and vibration, and large single-stage transmission ratio.The disadvantage is thataccuracyUnder the same transmission ratio, the efficiency of worm transmission is lower than that of gear transmission. In addition, worm gears generally need expensiveAntifriction material(e.gbronze）Manufacturing.Worm drive is widely used in machinery and related industries, such as automobilesdriveAxle drive;Transmission of intersecting axes of machine tools, automobiles, tractors and other machines;For steel rolling machinery and minesMechanics、Lifting and transportation machineryEtc.
gear drive
Gear transmission has a wide range of applications. The transmission power can reach tens of thousands of kilowatts, and the single-stage transmission ratio can reach 8 or moremachineIt is widely used in.Compared with other mechanical transmission, the advantages of gear transmission are: reliable operation, long service life;The instantaneous transmission ratio is constant;High transmission efficiency;Compact structure;The power and application range are very wide.Disadvantages: gear manufacturing needs special purposeMachine toolAnd equipment, with high cost;Vibration andNoiseLarger;It is not suitable for transmission with large distance between shafts.There are many types of gear transmission. According to the relative motion of two gears transmission is plane motion or space motion, it can be divided into two categories: plane gear transmission and space gear transmission.
gear train
The transmission system composed of a series of gears is called gear train, which is widely used in various mechanical equipment.Gear trains are divided into fixed axle gear trains and epicyclic gear trains.The main features of the gear train: it is suitable for transmission between two shafts far apart;Can be used asTransmissionRealize variable speed transmission;Large transmission ratio can be obtained;Realize the synthesis and decomposition of motion.[2]
Application Introduction
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retarder
The reducer is an independent part composed of gear transmission, worm transmission or gear worm transmission enclosed in a rigid housing, which is often used between the power machine and the working machine as the transmission device for reducing speed;In a few cases, it is also used as the transmission device for speed increase, which is called the speed increaser.The reducer is widely used in modern machines due to its compact structure, high efficiency, accurate transmission, reliable use and simple maintenance, and mass production.There are many types of reducers, mainlyGear reducer、worm reducer, gear worm reducer andplanet gearReducer, etc.
differential mechanism
Automobile differentialThe left and right (or front and rear) drive wheels can rotate at different speedsmechanism。It is mainly composed of left and right half shaft gears, two planetary gears and gear carrier.The function is to make the left and right wheels roll at different speeds when the car turns or runs on uneven roads, that is, to ensure that the driving wheels on both sidesPure rollingExercise.The differential is installed to adjust the speed difference between left and right wheels.stay4WDIn order to drive the four wheels, all wheels must be connected. If the four wheels are mechanically connected togetherCurve drivingIn order to make the rotation speed of the car basically consistent in curve driving, the middle differential needs to be added to adjust the speed difference between the front and rear wheels.[2]
main features
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(1) Main features of meshing transmission
Advantages: reliable operation, long service life, accurate transmission ratio and transmissionpowerLarge, high efficiency (except worm drive), wide speed range.
Disadvantages: high precision requirements for processing, manufacturing and installation.
Disadvantages: large overall dimension, inaccurate transmission ratio, low transmission efficiency, short component life.
Classification Introduction
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1. Classification of gear transmission:
(1) According to the relative motion during transmission, it can be divided into plane motion or space motion: ① plane gear transmission (common with straight teethcylindrical gearTransmission, helical cylindrical gear transmissionherringbone gear , according to the tooth direction, it is also divided into externalmesh, internal engagement and engagement of gear and rack) ② spatial gear transmission (bevel gear transmission, staggered shaft gear transmission).
(2) According to the working conditions of gear transmission: closed transmission (enclosed in a rigid box), open transmission（gearIs exposed).
(2) According to the number of heads of the worm spiral line, it can be divided into single head, double head and multi head worm;
(3) According to the rotation direction of the helix, it can be divided into left and right rotation.[3]
3. Classification of chain drive:
(1) Active chain
(2) Driven chain
Mechanical transmission system
(3) Ring chain transmits motion and force by meshing the chain with sprocket teeth.It can be divided into roller chain and tooth chain according to different structures. Tooth chain is used for transmission with high speed or high kinematic accuracy.The transmission ratio of chain drive is not more than 8, the center distance is not more than 5~6M, the transmission power is not more than 100KW, and the peripheral speed is not more than 15M/s.
4、gear trainClassification (consisting of a series of gears):
(1) The gear train is divided into fixed axle gear train (the geometric axis of each gear is fixed) and epicyclic gear train (at least one gear's geometric axis rotates around the geometric axis of another gear).
(2) Between input shaft and output shaft in gear trainangular velocityThe ratio (or speed) is called the transmission ratio of the gear train.The transmission ratio of the fixed axle gear train is equal to all the gears in each pair of meshing gearsDriven gearThe ratio of the product of the number of teeth to the product of the number of teeth of all driving gears.
(3) In the epicyclic gear train, the gear whose axis position changes isrotationThe gear for revolution is called planetary gear, and the gear with fixed axis position is called central gear or sun gear.
(4) The transmission ratio of the epicyclic gear train cannot be calculated directly by solving the transmission ratio of the fixed axle gear trainrelative motionThe epicyclic gear train is transformed into an imaginary one by using the relative speed method (or the reverse method)Fixed axle gear trainCalculate.[1]
