Worm gearwormstructureIt is often used to transmit the motion and power between two staggered axes.Worm gear and worm are equivalent togearIt is similar to rack and worm in shape to screw.
Modulus mpressure angle, worm diameter coefficient q, lead angle, number of worm heads, number of worm gear teethAddendum height coefficient(1) and top clearance coefficient (0.2).Wherein, module m and pressure angle refer to module sum of worm shaft surfacepressure angle, that is, the modulus and pressure angle of the worm gear end face, both of which are standard values;The worm diameter coefficient q is the worm reference circlediameterRatio to its modulus m.[1]
Classification and conditions
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classification
Worm gear and worm basically have these series: 1. WH seriesWorm gear reducerWHT/WHX/WHS/WHC2, CW series worm gear reducer: CWU/CWS/CWO3, WP series worm gear reducer: WPA/WPS/WPW/WPE/WPZ/WPD4, TP series enveloping worm gear reducer: TPU/TPS/TPA/TPG5, PW type planeQuadratic envelopeIn addition, according to the different shapes of the worm, the worm drive can be divided into cylindrical worm driveenveloping worm drive andspiroid gearing 。[1]
Characteristics of the mechanism
1. Large transmission ratio can be obtainedhelical gearCompact mechanism.2. The meshing tooth surfaces of two wheels are in line contact with each other, and their bearing capacity is much higher than that of the staggered shaftGear unit。threeworm driveamount toScrew driveIt is a multi tooth meshing transmission, so the transmission is stable and the noise is very low.4. It is self-locking.When the lead angle of the worm is smaller than theequivalent friction angle The mechanism is self-locking and can realize reverse self-locking, that is, only the worm can drive the worm gear, but not the worm gear.For example, the reverse self-locking of the self-locking worm mechanism used in lifting machinery can play a role in safety protection.5. Low transmission efficiency and serious wear.When worm gear and worm are engaged, the relative sliding speed between the meshing gear teeth is large, so the friction loss is large and the efficiency is low.On the other hand, the relative sliding speed causes serious wear and heat on the tooth surface. In order to dissipate heat and reduce wear, more expensive materials with good friction and wear resistance and good lubrication devices are often used, so the cost is high.6. The axial force of worm is large.[1]
application
Worm gear and worm mechanism are often used in situations where two shafts are staggered, transmission ratio is large, transmission power is small or intermittent work.[1]
common problem
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Worm gear
1、 Common problems and their causes
1. The reducer is heated and leaks oil.To improve efficiency,Worm gear reducerGenerally, non-ferrous metal is used as the worm gear, and the worm is made of hard steel.Due to the sliding friction drive, more heat will be generated during operation, which will cause the difference in thermal expansion between all parts and seals of the reducer, thus forming gaps on all mating surfaces. The lubricating oil will become thinner due to the temperature rise, which is easy to cause leakage.There are four main reasons for this situation. First, the materials are not matched properly;Second, the surface quality of the meshing friction surface is poor;Third, the selection of lubricating oil dosage is incorrect;Fourth, poor assembly quality and use environment.Worm gear is worn.The worm gear is generally made of tin bronze, and the paired worm material is hardened to HRC45~55 with 45 steel, or HRC50~55 with 40Cr, and then ground to Ra0.8 μ m by the worm grinder.Reducers wear slowly during normal operation, and some reducers can be used for more than 10 years.If the wear speed is fast, it is necessary to consider whether the model selection is correct, whether the operation is overloaded, and the material, assembly quality or use environment of the worm gear and worm.3. The transmission pinion is worn.Generally, it occurs on the reducer installed vertically, which is mainly related to the amount of lubricating oil added and the type of oil.During vertical installation, it is easy to cause insufficient lubricating oil. When the reducer stops running, the transmission gear oil between the motor and the reducer will be lost, and the gear will not receive the proper lubrication protection.When the reducer is started, the gear will be worn or even damaged due to lack of effective lubrication.4. Worm bearing is damaged.In case of failure, even if the gearbox is well sealed, it is often found that the gear oil in the reducer is emulsified, and the bearing is rusted, corroded and damaged.This is because after the reducer has been running for a period of time, the condensate produced by the gear oil temperature rising and cooling is mixed with the oil.Of course, it is also closely related to bearing quality and assembly process.[1]
2、 Solution
1. Ensure the assembly quality.Some special tools can be purchased or self-made. When disassembling and installing reducer components, try to avoid knocking with hammer and other tools;When replacing gears and worm gears, try to use original accessories and replace them in pairs;When assembling the output shaft, pay attention to the tolerance fit;Anti sticking agent or red lead oil shall be used to protect the hollow shaft to prevent wear and rust or scale on the matching area, which is difficult to disassemble during maintenance.2. Selection of lubricating oil and additives.The worm gear reducer generally uses 220 # gear oil. For the reducer with heavy load, frequent startup and poor service environment, some gears can be selectedLubricant additivesWhen the reducer stops running, the gear oil will still adhere to the gear surface, forming a protective film to prevent heavy load, low speed, high torque and direct contact between metals during startup.The additives contain sealing ring regulator and anti leakage agent to keep the sealing ring soft and elastic and effectively reduce the leakage of lubricating oil.3. Selection of reducer installation position.If the position allows, vertical installation shall not be adopted as far as possible.During vertical installation, the amount of lubricating oil added is much more than that of horizontal installation, which is easy to cause heat and oil leakage of the reducer.4. Establish lubrication maintenance system.The reducer can be maintained according to the principle of "five fixations" for lubrication, so that each reducer is regularly inspected by the responsible persontemperature riseObviously, when the temperature exceeds 40 ℃ or the oil temperature exceeds 80 ℃, the quality of the oil drops, or more copper powder is found in the oil, and abnormal noise is generated, the oil shall be stopped immediately, and it shall be overhauled in time to eliminate the fault and replace the lubricating oil.When refueling, pay attention to the amount of oil to ensure that the reducer is properly lubricated.[1]
