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The characteristics and maintenance methods of gear coupling

Constant force transmission
03-27
2019

Gear coupling is a kind of removable rigid coupling.It uses internal and external tooth meshing to realize the torque rotation and movement transmission between the two halves of the coupling. It is suitable for the transmission shaft system connecting two concentric shafts, and has the performance of relatively compensating the relative displacement of the two shafts.Its structure is shown in Figure XNUMX. It is composed of main parts such as inner gear ring, gear sleeve and end cover. Generally, small-sized gear coupling end cover and inner gear ring can be integrated.

Gear couplings are widely used in various machinery industries such as metallurgy, mining, lifting and transportation, petroleum and shipping due to their compact structure, large carrying capacity, wide operating speed range, and working characteristics.

Features of gear coupling:

Gear couplings have small radial dimensions, large carrying capacity, and are long used for shafting transmissions under low-speed and heavy-duty conditions. The dynamically balanced gear couplings can be used for high-speed transmissions, such as gas turbine shafting transmissions. .Because the angular compensation of drum gear couplings is greater than that of straight gear couplings, drum gear couplings are widely used. Straight gear couplings are obsolete products and should not be used as much as possible.

, The more common gear couplings in the market include general structure gear couplings, drum gear couplings, nylon gear couplings and so on.Among them, there are many types of drum gear couplings and they are widely used. 

Features and performance of gear coupling:

Gear couplings can be divided into three types according to the different axial tooth profiles of the outer gear bushings, namely straight gear couplings, drum gear couplings and drum gear couplings. No matter that One type, the ring gear and the involute spur internal gear are the same except for the difference in the selection of the head clearance coefficient of the gear teeth.

The axial gear blank of the external gear sleeve of the spur gear coupling can be machined into two kinds of linear and circular arc shapes, and the index circle and the tooth root circle are both straight lines. The meshing form of this coupling is gradually The internal and external teeth of the open cylindrical gear mesh with the whole.The relative displacement between the two shafts is compensated by increasing the flanks of the inner and outer teeth, but the amount of compensation is limited.

The tooth tip of the external gear sleeve of the drum-shaped gear coupling is processed into an arc, that is, the tooth blank is processed into a spherical surface. In the section of the tooth plane and tangent to the pitch cylinder surface, the teeth form a drum shape, which is the so-called drum-shaped coupling. Shaft.Its characteristics are:

15. High load-carrying capacity, calculated by bending strength, under the same conditions, the torque transmitted by the spur gear coupling is increased by 30-XNUMX%;

XNUMX. Reasonable structure and performance. Because the tooth side is drum-shaped, the contact of the axis under the condition of relative angle reduces the contact stress, and the load concentration at the tooth end of the spur coupling, that is, the edge is squeezed. Pressure, improve work performance.

6. Good compensation performance. The tooth profile of the outer gear sleeve is drum-shaped, which increases the allowable relative deviation of the two shafts connected. The allowable inclination angle can reach 1.5 degrees, and 2.5°~XNUMX° is generally recommended.  

Torsion and manufacturing process of gear coupling:

Coupling misalignment is divided into deflection misalignment, parallel misalignment and comprehensive misalignment.The misalignment of the deflection angle is the deflection of the end face of the coupling, and the axis lines of the two half couplings are at an angle, which generates an exciting force in the rotating state to induce a vibration response.Parallel misalignment means that the axis lines of the two half couplings are not on the same straight line, but are kept parallel to each other for a certain distance, which produces a vibration response in the rotating state.Comprehensive misalignment is a relatively common misalignment phenomenon in actual rotating machinery. It has both deflection misalignment and parallel misalignment, which is a combination of the two.

During the manufacturing process, the end face is not perpendicular to the axis line or the center line of the end face bolt hole is not concentric with the journal due to process or measurement.In the installation process, after tightening the connecting bolts (tooth sleeve bolts), the rotating shaft is deformed. At this time, there is a large sway in the journal.Sometimes, due to the difference in the tightening force of the connecting bolts in the circumferential direction of the coupling, it can also cause the same situation as the deflection of the end face of the coupling.During operation, if the working conditions change drastically, such as in the load process, when the load is brought to a certain value (that is, the shaft torque increases to a relative value), the coupling will be misaligned and the shaft alignment state will change , The vibration response of the rotor connected by the coupling will undergo abrupt changes.The shafting torque changes drastically in an instant, which has an impact on the torque-transmitting coupling, causing the couplings to be misaligned with each other, and the shafting centering state changes. 

The torsional vibration of the gear coupling is analyzed and studied, and the Fourier series solution is mainly used to analyze the torsional vibration of the gear coupling connecting shaft system with the parameters of, damping and excitation force; then A large number of tests have been carried out on the axial vibration of the gear coupling connecting shaft system, and the main reason for the axial vibration is qualitatively explained. It is pointed out that the axial vibration is mainly caused by the misalignment and the friction of the tooth surface. Larger axial movement will occur during axial restoring force or thrust bearing.

Vibration analysis is one of the techniques for predicting coupling misalignment. It can judge the gradual change trend of the equipment state, but when judging whether a piece of equipment is in a misalignment state, it needs to have a lot of past data and examples for reference, and there are differences. The problem is the bearing, lubricating oil, coupling, or the fixed connection, so there are relative limitations.Infrared photography technology can distinguish overheated parts such as bearings, motor housings, couplings, etc. when the equipment is in poor condition, and determine the alignment error of the coupling, and combine it with other prediction technologies such as vibration analysis. , Its effect will be relatively better.

The literature has conducted experiments on high-speed rotating turbine generators and blowers, and briefly explained the bending vibration caused by gear couplings; the literature has different parameter conditions such as unbalance, lubrication conditions, errors, and loads. The flexural vibration test of the gear coupling connecting shaft system was carried out in the following. In addition, Yamauchi and Someya et al. conducted a nonlinear analysis of the flexural vibration of the semi-coupling system under the action of dry friction on the tooth surface. The vibration of the coupling is mainly related to the misalignment of the internal and external gears and tooth surface friction. Special attention should be paid to the lubrication of the tooth surface in the case of high-speed rotation.

Maintenance method of gear coupling:

There are hundreds of types of gear couplings, but the basic forms are two types: 1. Combination of internal and external teeth; 2. Combination of end gears.The other forms are all deformations on these two foundations.The gear clutch with internal and external gears transmits a relatively large torque. The design takes into account the different needs of users and is deliberately designed so that the lengths of the shaft ends on both sides of the teeth are not consistent, so that users can choose the installation direction according to their needs.Therefore, there is no stipulation on which end faces where.Pay attention to the installation: 1. If it is replaced by the original equipment, it must be in the same direction as the original one. If it is a newly designed and manufactured equipment, it must be in accordance with the internal and external conditions without interference with other surrounding parts. The more the tooth surface, the more the principle of installation.

The maintenance of gear coupling is generally carried out as follows:

50. Check the gear tooth surface meshing condition of the coupling. The contact area is not less than 70% along the tooth height and not less than XNUMX% along the tooth width. There should be no severe corrosion, abrasion and cracks on the tooth surface.

0.03. The full circle runout of the outer gear ring of the coupling is not more than 0.02mm, and the end circle runout is not more than XNUMXmm.

200. If you need to remove the gear ring, you should use tools instead of knocking, so as not to bend or damage the shaft.When reinstalling, heat the ring gear to about 0.01°C before installing it on the shaft.The interference between the outer gear ring and the shaft is generally 0.03~XNUMXmm.

XNUMX. When reinstalling the intermediate tube or other parts, it should be assembled according to the original marks and data.

XNUMX. Tighten the bolts evenly with a torque wrench.


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