The advantages and disadvantages of elastic couplings and maintenance analysis

Elastic couplings are appliances used in mechanical equipment. Elastic couplings are widely used. Do you know the advantages and disadvantages of elastic couplings and how to maintain them? The following is the relevant content brought by the editor. I hope that we can have The harvest!

Defects and fault treatment of elastic couplings, error explanation

　　1. The elastic coupling can transmit torque and reverse the viewpoint, and together can absorb the device error of the shaft. When the device error exceeds the allowable value, it may oscillate or cause the life of the coupling to be shortened, so it is necessary to ensure the error adjustment appropriate.
　　 2. There are three types of axis errors: D1 is a radial error, that is, the two axes are parallel but the center line is no longer on the same straight line. The error that occurs at this time is called a radial error; the second is an angular error, that is, two axes The errors occur when the centers form one point of view; the third type is the axial error, that is, the error caused by the reciprocating micro-motion of the two axes.
　　 3. The error tolerance value listed in each product means that when only one error exists, when two or more errors exist together, the tolerance value should be less than 1/2 of the error in each specification table.
　　 4. The error does not only occur in the installation of the equipment, but also the vibration, thermal expansion, bearing wear and other factors in the operation process will cause the error.Therefore, it is advocated to adjust the axial error to less than 1/3 of the value.
　　 The most important defect of elastic couplings is poor elasticity (that is, poor cushioning function).Common problems are:
　　 (1) Oil leakage.In addition to the quality of the seals, the main reason is the selection of the type of lubricating oil. The thinner lubricating oil cannot be used. According to the requirements of the product specification, more lubricating grease should be selected.
　　 (2) During operation, the jitter and movement are large (especially used in the high-speed stage).During installation, the error between the two shafts is too large (axial, radial and viewpoint errors), and the unbalance of some rolling parts of the coupling must be strictly in accordance with the requirements of the planned installation to achieve the accuracy of the installation.
　　 (3) Gear wear.Larger wear is used at high-speed shafts, but there is also wear at low speeds.In some mines, not only the gap between the teeth is 3mm~5mm, but the most serious is that the teeth on the outer gear sleeve are sharpened, and even more so, the teeth on the outer gear sleeve are shaved, especially It is outstanding when operating under high-speed operating conditions.Solution: The first thing is to adjust the accuracy of the device, reduce the mutual movement of the coupling parts, control the load, and not overload.
　　 (4) The noise is large.This is also related to the accuracy of the device. Some meet the requirements when the device is installed, but some will change after some time.
　　 (5) Low life span.When used in high-speed grades, a complete set of couplings must be replaced within 3 years of pollution.
　　 (6) The tightening bolts used for the connection between the two external gear shaft sleeves are loosened (mainly present on the elastic coupling at the output shaft of the main shaft and the reducer).The main reason is overloading. The cooperation of the bolts is not tight or loose. Because the cooperation is not tight or loose, impact will occur. Soon after use, the bolts will be cut under repeated impacts.Therefore, it is necessary for the cooperation bolts to meet the cooperation requirements according to the planning requirements. If the above situation occurs, not only the bolts need to be replaced, but the bolt cooperation holes must be reamed from the beginning.When replacing some coal mines, the cooperative bolts here are changed to a conical shape. Practice indicates that the effect is very good.
　　 (7) The main shaft of the shaft is cracked due to the accumulation of stress at the keyway of the tangential key of the coupling, which has occurred in coal mines.The most important thing is that when the keyway is processed, the tip of the milling cutter for milling the keyway does not meet the fillet requirements, and some are even completely sharp. Therefore, the stress at the keyway will be too large and cracks will appear for a while. Under the effect of working load (especially the coal mine used for overload), fatigue cracks will appear. Under the continuous effect of the load during the forward and reverse rotation, the cracks will gradually expand until the main shaft is cracked.
　　 (8) The most serious incident is that the teeth of the outer gear sleeve of the coupling are cracked, which makes the lifting cage slip out of control, and the faster the speed, and the increased heat makes the conflict factor of the smelling tile greatly reduced, and it can’t be smelled. The truck and the cage quickly dropped and blocked the tank, causing a serious incident of casualties.The primary cause of the incident is that the length of the two outer gear sleeves of the selected gear coupling is less than the standard length, and the size of the inner gear sleeve is standardized, so there is a large gap formed on the end faces of the two outer gear sleeves. More importantly, when the device is installed, the teeth of the inner gear sleeve and the tooth surface of the outer gear sleeve do not touch, and the shaft moves greatly during operation, forming the teeth on the inner gear sleeve and the upper tooth surface of the outer gear sleeve. The stress is greatly increased. After using for a period of time, the teeth on the shaft sleeve are severely worn due to the large stress, and they are worn to a certain degree, appearing cracks, forming a coupling failure, and improving the machine out of control.At that time, there are people in the raised cage. The out-of-control raising machine slides under the effect of gravity, and the speed is getting faster and faster. When the driver finds it and chooses emergency braking, the speed is too high and the temperature of the smell is very high. The conflict factor is greatly reduced, and the braking force is not good enough to cause serious injury and increase the incident.
　　 Processing claims:
　　 (1) It is necessary to strictly adjust the azimuth and scale between the two axes as required.When installing, you must pay attention to the adjustment of the end face dimensions between the two shafts of the coupling and the touch requirements and installation dimensions of the internal gear and the external gear.
　　 (2) For elastic couplings used at higher speeds, pay attention to the hardness requirements of the tooth surface.
　　 (3) Pay attention to the type and quality requirements of smooth grease.
　　 (4) The joint bolts between the two inner gear sleeves must be hinged bolts and locked tightly. Always pay attention to whether there is any looseness during use. If there is any, it must be replaced in time, and the reaming holes of the bolts must also be used. Hinge from the head.
　　 (5) When the outer gear sleeve is sleeved on the spindle head, it is necessary to strictly check the chamfer of the coupling hole and the rounded corner of the spindle and the general matching part, in case i1=the occurrence of the shaft hole and the shaft being stuck in the part, which can not reach To the requirements of the touch surface.
　　 (6) Pay attention to the manufacturing quality of the tangential key (touch surface requirements).
　　 (7) The load must be controlled during use and not overloaded.

Analysis of Oscillation of Elastic Coupling

Because of the existence of the star-shaped elastic coupling, the vibration of the shafting is aggravated, so many professional technicians have conducted discussions on this.Because of the existence of the star-shaped elastic coupling, the vibration of the shafting is aggravated, so many professional technicians have conducted discussions on this.Oscillation analysis is one of the skills to guess the misalignment of the coupling. It can distinguish the gradual change trend of the equipment condition, but when judging whether a piece of equipment is in a misalignment condition, it is necessary to refer to many previous data and cases for reference. The main problem is bearings, lubricating oil, and couplings, which are still connected and fixed, so there are certain limitations.Infrared camera technology can distinguish overheated parts such as bearings, motor housings, couplings, etc. when the equipment is in poor condition, and determine the alignment errors of the coupling, combined with other guessing skills such as vibration analysis, The effect will be good.

　　The elastic coupling’s changing oscillation was analyzed and discussed. The Fourier series solution method was first used, and the gap, damping, and excitation force were used as parameters to analyze the changing oscillation of the elastic coupling with the shaft system. A lot of experiments have been carried out on the axial oscillation of the elastic coupling connecting the shaft system, and the primary reason for the axial oscillation has been qualitatively explained. It is pointed out that the axial oscillation is mainly caused by the misalignment and the conflicting force of the tooth surface. Larger axial movement will occur during axial recovery force or thrust bearing.The literature has conducted experiments on high-speed reversing turbine generators and blowers, and briefly clarified the tortuous oscillation caused by the elastic coupling; the literature has different parameters such as unbalance, smooth conditions, gaps, errors, and loads. Under the conditions, the tortuous oscillation experiment of the elastic coupling coupling shaft system was carried out; other people such as Yamauchi and Someya conducted a nonlinear analysis of the tortuous oscillation of the semi-coupling system under the effect of the dry conflict force on the tooth surface, and pointed out the elasticity in the article. The oscillation of the coupling is mainly related to the misalignment of the front and back gears and the tooth surface conflict. Special attention should be paid to the smoothness of the tooth surface in the case of high-speed reverse rotation.  

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