Man: I helped you find a little online you organize yourself on the line, I wish you success!
According to historical records, as far away as 400 ~ 200 years BC in ancient China has begun to use gears, the bronze gears unearthed in Shanxi, China is so far the oldest gears have been found, as a reflection of ancient scientific and technological achievements of the guide car is the core of the gear mechanism of mechanical devices. 17th century, people began to study the shape of the wheel gears to correctly transmit the movement. 18th century, after the industrial revolution in Europe, the application of gears became more and more widespread; first the development of cycloidal gears, the development of the gears of the wheel gear. After the industrial revolution in Europe, the application of gear transmission is becoming more and more widespread; first the development of cycloid gears, and then involute gears, has been to the early 20th century, involute gears have been in the application of the dominant.
As early as 1694, the French scholar Philippe?De?La?Hire first proposed that the involute can be used as a tooth curve. 1733, the French M. Camus proposed that the common normal of the contact point of the gear teeth must pass through the node on the center line. An auxiliary instantaneous center line respectively along the big wheel and small wheel instantaneous center line (node circle) pure rolling, and auxiliary instantaneous center line solid connection of auxiliary tooth shape in the big wheel and the small wheel on the formation of the envelope of the two tooth profile curve is with each other **** yoke, this is Camus theorem. It takes into account the meshing state of the two tooth surfaces; clearly established the modern concept of contact point trajectory. 1765, Switzerland's L. Euler put forward the mathematical basis of the analytical study of the involute tooth shape, clarified the meshing of a pair of gears, the curvature radius of the curve of the tooth shape and the curvature of the center of the position of the relationship. Later, Savary further completed this method, which became the present Eu-let-Savary equation. Contribute to the application of involute tooth shape is Roteft?WUlls, he proposed that the center distance change, involute gears have the advantage of the angular speed ratio is unchanged. 1873, the German engineer Hoppe proposed, for the different number of teeth in the pressure angle of the gear when the pressure angle change of the involute tooth shape, thus laying the basis for the idea of the modern variable displacement gears. At the end of the 19th century, the principle of spreading into the gear-cutting method and the use of this principle of cutting teeth of special machine tools and cutting tools appeared one after another, so that the gears and tools military more complete means, the involute tooth shape more show great advantages away from the nature. Cutting gears as long as the gear cutting tool from the normal mesh position slightly moved, you can use the standard tool in the machine tool to cut out the corresponding gear shift. 1908, Switzerland MAAG study the shift method and manufactured into the processing of gear inserting machine, and later, the British BSS, the United States AGMA, Germany DIN successively gear shift put forward a variety of methods of calculation. In order to improve the service life of power transmission gears and reduce its size, in addition to materials, heat treatment and structure and other aspects of the improvement, the arc gears have been developed. 1907, the British Frank Humphris first published the arc gears. 1926, Swiss-Turkish Eruest Wildhaber obtained the patent for the French arc gear helical gear. 1955, the Soviet Union M. Wildhaber, the Soviet Union, the Soviet Union, the Soviet Union, the Soviet Union, the Soviet Union, the Soviet Union, the Soviet Union, the Soviet Union, the Soviet Union, the Soviet Union, the Soviet Union, the Soviet Union, the Soviet Union, and other countries. In 1955, the Soviet Union's M. L. Novikov completed the practical research of the circular arc tooth gear and won the Order of Lenin. 1970, the British Rolh-Royce company engineer R. M. Studer obtained the double arc gears of the U.S. patent. This gear is now increasingly valued by people in the production has played a significant benefit. Gear is able to mesh with each other with teeth of mechanical parts, it is in the mechanical transmission and the entire mechanical field of application is extremely wide. Modern gear technology has reached: gear modulus O.004 ~ 100 mm; gear diameter from 1 mm to 150 meters; transfer power up to hundreds of thousands of kilowatts; speed up to hundreds of thousands of revolutions / min; the highest circumferential speed up to 300 m / sec. The application of gears in the transmission appeared very early. More than three hundred years BC, the ancient Greek philosopher Aristotle in the "Mechanical Problems", on the elaboration of the use of bronze or cast iron gears to transmit rotary motion. A complete wheel system was already applied in the compass car invented in ancient China. However, ancient gears were made of wood or cast in gold? Metal casting, can only pass the rotary motion between the shaft, can not guarantee the smoothness of the transmission, the bearing capacity of the gear is also very small. With the development of production, the smoothness of the gear operation was emphasized, and in 1674, the Danish astronomer R?mer proposed for the first time to use the external pendulum for the profile curve, in order to get a smooth running gear. In the 18th century, during the Industrial Revolution, gear technology developed at a high speed, and a great deal of research was done on gears. 1733, French mathematician Carmi published the basic law of tooth profile meshing; in 1765, Swiss mathematician Euler suggested the use of involute lines for the tooth profile curve. In the 19th century, the emergence of hobbing machine and gear shaping machine, to solve the problem of mass production of high-precision gears. 1900, Pfauter for the hobbing machine equipped with a differential device, can be processed in the hobbing machine helical gears, hobbing machine hobbing gears have been popularized, the spreading method of processing gears accounted for the overwhelming advantage of the gears, involute gears to become the most widely used gears. In 1899, Rasche was the first to implement the program of variable gears. Shift gear can not only avoid gear tooth root cut, but also can make up with the center distance and improve the bearing capacity of the gear. 1923 U.S. Wylde Harper was the first to put forward the gear arc tooth profile, 1955 Sunovikov arc gear in-depth research, arc gears can be applied to the production. The bearing capacity and efficiency of such gears are higher, but not as easy to manufacture as involute gears, to be further improved. The structure of the gear is generally composed of gear teeth, gear groove, end face, normal surface, top circle, root circle, base circle, indexing circle. The gear teeth, referred to as teeth, are on the gear? Each of the raised portion for meshing, these raised portions are generally arranged in a radial pattern, paired with the gear teeth on the gear in contact with each other, allowing the gear to continue to mesh operation; tooth groove is the space between the two adjacent gear teeth on the gear; the end face is a cylindrical gear or cylindrical worm on the ? , a plane perpendicular to the axis of the gear or worm; the normal plane refers to the plane perpendicular to the tooth line of the gear teeth; the top circle is the circle where the top of the tooth is located; the root circle is the circle where the bottom of the slot is located; the base circle is the circle that forms the incurved line of the occurrence of the pure roll; the indexing circle? is the reference circle for calculating the geometric dimensions of the gear in the end face. Gears can be categorized by tooth shape, gear profile, tooth line shape, the surface where the gear teeth are located and manufacturing methods. The tooth form of a gear includes the profile curve, pressure angle, tooth height, and variation. Involute gears are easier to manufacture, so of the gears in modern use? , involute gears account for the absolute majority, while cycloid and circular gears are less used. In terms of pressure angle, small pressure angle gears have a smaller carrying capacity; and large pressure angle gears, although the carrying capacity is higher, but in the case of transferring the same torque the load on the bearings increases, so it is only used in special cases. The tooth height of the gear has been standardized, generally using the standard tooth height. Shift gears have more advantages, has been all kinds of mechanical equipment. In addition, gears can also be divided into cylindrical gears, bevel gears, non-circular gears, racks, worm gears? ; according to the shape of the tooth line is divided into spur gears, helical gears, herringbone gears, curved gears; according to the surface where the gear teeth are divided into external gears, internal gears; according to the manufacturing method can be divided into casting gears, cut gears, rolled gears, sintered gears, and so on. Gear manufacturing materials and heat treatment process on the gear's load-bearing capacity and size of the weight has a great impact. 1950s ago, gears are mostly carbon steel, 60s changed to alloy steel, and more surface-hardened steel in the 70s. According to the hardness?The gear surface can be differentiated into two kinds of soft gear surface and hard gear surface.
The soft tooth surface of the gear bearing capacity is lower, but easier to manufacture, good running, ? More for transmission size and weight without strict limits, as well as small production of general machinery. Because of the paired gears, the small wheel burden is heavier, so in order to make the size of the working life of the gear is roughly equal, the small wheel surface hardness is generally higher than that of the wheel. The hardened gears have a high load carrying capacity, it is after the gear precision cutting? , and then quenching, surface quenching or carburizing quenching treatment to improve the hardness. However, in the heat treatment, the gear will inevitably produce deformation, so after the heat treatment shall be grinding, grinding or fine cutting? In order to eliminate errors due to deformation, and improve the accuracy of the gear. Steel commonly used in the manufacture of gears are tempered steel, quenched steel, carburized quenched steel and nitrided steel. The strength of cast steel is slightly lower than forged steel, commonly used in gears of larger sizes; gray cast iron has poor mechanical properties, can be used for light-duty open gear transmission; ductile iron can partially replace the steel manufacturing gears? ; plastic gears are mostly used for light loads and low noise requirements, and its paired gears are generally used with good thermal conductivity of steel gears. The future of gears is to heavy-duty, high-speed, high-precision and high-efficiency direction, and strive for small size, light weight, long life and economic and reliable. And the development of gear theory and manufacturing process will be to further study the mechanism of damage to the gear teeth, which is the basis for the establishment of a reliable strength calculation method, is to improve the gear load carrying capacity, extend the theoretical basis of gear life; the development of new tooth shape represented by the circular arc tooth profile; research on new types of gear materials and manufacture of gears and new processes; ? Research on the elastic deformation of the gear, manufacturing and installation errors and the distribution of the temperature field, gear tooth modification, in order to improve the smoothness of the gear operation, and increase the contact area of the gear teeth when fully loaded, so as to improve the gear's load-bearing capacity. Friction, lubrication theory and lubrication technology is ? Gear research in the basic work, the study of elastic fluid dynamic pressure lubrication theory, promote the use of synthetic lubricants and in the oil properly added to the extreme pressure additives, not only to improve the bearing capacity of the teeth, but also to improve transmission efficiency.Types of gear mechanism:
1, to the ratio classification?
Fixed transmission ratio? --? Circular gear mechanism (cylindrical, conical)?
Variable transmission ratio? --? Non-circular gear mechanism (elliptical gear)?
2, to the wheel axis relative position classification?
Plane gear mechanism?
Horizontal cylindrical gearing?
External gearing?
Internal gearing?
Rack and pinion drives?
Helical cylindrical gearing?
Hermaphroditic gearing?
Space gear mechanism?
Bevel gearing?
Staggered shaft helical gearing?
Worm gear transmission
Gear process:
Bevel gear?
Blank semifinished gears?
Helical gears?
Inner gear?
Spurface gears?
Worm gear
Helical cylindrical gear main parameters
Spiral angle: β?>?0 for left-hand rotation, and vice versa for right-hand rotation Tooth spacing: pn?=?ptcosβ, with the subscripts n and t denoting the normal and the end face Module: mn?=?mtcosβ Tooth width: Diameter of index circle: d?=?mtz Center distance: a=1.0mm. p> Center distance: a=1/2*m(z1+z2) Correct meshing conditions: m1?=?m2,α1?=?α2,β1?=β2 Degree of overlap: Equivalent number of teeth: Simple diagnostic method of gear vibration The purpose of simple diagnostic method is to determine whether the gears are in the normal working condition quickly, and to further carry out precise diagnostic analysis or take other measures for the gears in abnormal working condition. Further precision diagnostic analysis or other measures. Of course, in many cases, based on a simple analysis of vibration, can also diagnose some obvious faults. The simple diagnosis of the gear includes noise diagnostics, vibration level diagnostics and shock pulse (SPM) diagnostics, etc., the most commonly used is the vibration level diagnostics. The vibration level diagnostic method is to use the vibration intensity of the gear to determine whether the gear is in normal working condition diagnostic method. According to different judgment indicators and standards, can be divided into absolute value judgment method and relative value judgment method. 1. Absolute value determination method Absolute value determination method is the use of the same measurement point on the gear box parts measured amplitude value directly as an evaluation of the operating state of the index. Absolute value determination method for gear state identification, must be based on different gearboxes, different requirements for the use of the development of the corresponding judgment standards. The main basis for the development of absolute value determination of gear standards are as follows: 1) theoretical study of abnormal vibration phenomena; (2) according to the experimental analysis of the vibration phenomenon; (3) statistical evaluation of measured data; (4) reference to domestic and foreign standards. In fact, there is no absolute value determination standard that can be applied to all gears, when the size and type of gears are different at the same time, the determination standard is naturally different. When judging the vibration of a broadband by a measurement parameter, the standard value must be changed according to the frequency. Frequency below 1kHz, vibration according to the speed to determine; frequency above 1kHz, vibration according to the acceleration to determine. The actual standard also depends on the specific circumstances. 2. Phase time value determination method In practice, for the gear has not yet developed an absolute value determination standard, you can make full use of the field measurement data for statistical averaging, the development of appropriate relative determination standards, the use of such standards for the determination of the relative value of the determination method called. Relative judgment standards require the same part of the gear box measurement point in different moments measured amplitude and normal state amplitude comparison, when the measured value and the normal value compared to a certain extent, judged as a state. For example, the relative value judgment standard stipulates that attention should be paid when the actual value reaches 1.6~2 times the normal value, and danger is indicated when it reaches 2.56~4 times. As for the specific use is in accordance with 1.6 times for grading or 2 times for grading, depending on the use of gearbox requirements, more rough equipment (such as mining machinery) generally use a higher multiple of grading. In practice, in order to achieve the best results, you can use the above two methods at the same time, in order to compare and contrast, comprehensive evaluation.[edit]Gear - key terms
Gear teeth (teeth) - each raised portion of a gear used for meshing. Generally, these projections are arranged in a radial pattern. The gear teeth on paired gears are in contact with each other, resulting in continuous mesh operation of the gears.? Gear Groove - the space between two neighboring gear teeth on a gear.? Gear face - the plane perpendicular to the axis of the gear or worm on a cylindrical gear or cylindrical worm.? Normal face - On a gear, the normal face refers to the plane perpendicular to the tooth line of the gear teeth.? Top Circle - The circle where the top of the tooth is located.? Root circle - the circle where the bottom of the groove is located.? Base circle - the circle on which the line of generation forming the involute rolls purely.? Indexing circle - the reference circle for calculating the geometry of the gear in the end face, in the case of spur gears, the modulus and pressure angle are standardized on the indexing circle.? Tooth face - the side surface on the gear tooth between the top cylindrical surface and the root cylindrical surface.? Tooth profile - the intercept of the tooth surface by a specified surface (flat for cylindrical gears). Tooth line - the line of intersection between the tooth face and the indexing cylindrical surface. Face pitch pt - the length of the indexing arc between two neighboring end face profiles of the same side. Modulus m - the quotient in millimeters obtained by dividing the tooth pitch by the circumference π. The module m is the number of teeth in a circle. Pitch p - the reciprocal of the modulus, measured in inches.? Tooth thickness s?- the length of the indexing arc between the two side profiles of a gear tooth on the end face.? Slot width e?- the length of the indexing arc between the two side profiles of a tooth slot on the end face.? Tooth top height hɑ - the radial distance between the tooth top circle and the indexing circle.? Root height hf - the radial distance between the indexing circle and the root circle.? Full tooth height h - radial distance between the top circle and the root circle.? Tooth width b - the dimension of the gear tooth along the axial direction.? End face pressure angle ?ɑt-? The acute angle between the radial line past the point of intersection of the end face tooth profile and the index circle and the tangent line to the tooth profile past that point.? Standard rack: Only the size of the base circle, tooth shape, full tooth height, crown height and tooth thickness are in accordance with the standard spur gear specifications of the rack, according to the standard gear specifications of the cut out of the rack is called the standard rack. The reference pitch circle (Standard?Pitch?Circle): used to determine the size of the gear ministries reference circle. For? Number of teeth x module? Benchmark pitch line (Standard? Pitch? Line): a specific pitch line on the rack or along the line of the determination of the thickness of the teeth, for one-half of the pitch. Action Pitch Circle (Action?Pitch?Circle): a pair of spur gears bite the action, each has a tangent to do the rolling circle. Base pitch (Standard?Pitch): selected standard pitch as a reference, equal to the base rack pitch. Section circle (Pitch? Circle): two gears on the centerline of the bite contact points on the gears to leave a track called the section circle. Section diameter (Pitch? Diameter): the diameter of the pitch circle. Effective tooth height (Working?Depth): a pair of spur gear tooth crown height and. Also known as the height of the working gear. Crown height (Addendum): the difference between the crown circle and the pitch circle radius. Backlash: the gap between the tooth face and the tooth surface when the two teeth bite together. Clearance: the gap between the top of one gear and the bottom of the other gear when two teeth bite together. Pitch?Point: the point of tangency between a pair of gears and the pitch circle when the gears bite together. Pitch (Pitch): the distance between the two neighboring teeth corresponding to the arc of the point . Normal pitch (Normal?Pitch): involute gear along a specific section of the same vertical line measured pitch.? Introduction of plastic gears: With the development of science, gears have been slowly transformed from metal gears to plastic gears. Because plastic gears are more lubricating and wear-resistant.? It can reduce noise, reduce cost and reduce friction.