The selection of star coupling should consider the factors and the correct handling method of production problems

Published: 2018-09-06

The star coupling polyurethane plastic is an elastic element, which has the advantages of buffering, shock absorption, and convenient disassembly and assembly. The working temperature is -35~+80 degrees.The polyurethane elastomer is limited by the convex claw block, which can avoid the internal deformation caused by impact and the external deformation caused by centrifugal force; the large concave surface of the convex claw makes the surface pressure on the involute tooth very small, even if the tooth is overloaded , The teeth will not wear or deform.

The radial movement of the star coupling due to centrifugal force during high-speed operation will accelerate its wear, and a shell is added.In addition to the star coupling can prevent dust and oil storage, insufficient thinning may cause interference. Excessive thinning will weaken the strength of the tooth, and the backlash will be large.The contact condition of the external teeth avoids the disadvantages of squeezing the edge of the straight tooth and stress concentration under the condition of angular displacement. At the same time, the friction and wear of the tooth surface are reduced, the noise is reduced, and the maintenance cycle is long.The tooth end of the outer gear sleeve of the star coupling is in the shape of a horn, so it is not suitable for use under high speed and impact load conditions, nor for the connection of vertical shafts.When designing the overall structure of the star coupling, pay full attention to the lubrication and dust prevention between the tooth surface and the roller, as well as the protective effect.Because if the chain breaks, it may cause a personal accident.The radius of curvature of the bulge curve is proportional to the single-sided thinning of the internal teeth, that is, it is related to the meshing gap of the teeth, which makes the assembly and disassembly of the internal and external teeth easy.

When selecting a star coupling, the designer should choose the coupling based on the angle and needs of the slave shaft transmission, and should avoid simply considering the coupling of the main and driven ends.

XNUMX. Factors that should be considered when choosing a star coupling

(XNUMX) Mechanical characteristics of power machine

Between the power machine and the working machine, the main and driven ends are connected through one or several couplings of different types and specifications to form a shaft transmission system.In mechanical transmission, power machines are nothing more than electric motors, internal combustion engines and gas turbines.Due to the different working principles and mechanisms of the power machine, its mechanical characteristics are quite different. Some run smoothly, and some run with shocks, which have unequal effects on the transmission system.

(XNUMX) Load category

Due to different structures and materials, the load capacity of couplings used in the transmission system of various mechanical products varies greatly.The load category is mainly for the impact, vibration, forward and reverse rotation, braking, frequent start and other reasons of the working load of the working machine to form different types of loads.

(XNUMX) Allowable speed of star coupling

The allowable speed range of the coupling is determined by calculation according to the allowable linear speed and outer edge size of different materials of the coupling.The allowable speed range of couplings of different materials, varieties and specifications is different. Changing the material of the coupling can increase the allowable speed range of the coupling. The allowable speed for steel is greater than the allowable speed for cast iron.

For couplings used under working conditions of n>5000r/min, influencing factors such as the centrifugal force on the outer edge of the coupling and the deformation of elastic elements should be considered, and should be dynamically balanced.Non-metallic elastic element elastic couplings should not be used at high speeds. When the elastic elements are deformed at high speeds, flexible couplings should be selected. The couplings currently used for high speeds are nothing more thanDiaphragm couplingAnd drum gear coupling.

During the operation of the coupling, sometimes it will encounter problems such as damage to its parts. The reason for this problem may be that the maintenance of the equipment itself and the parts is not paid attention to in the later use, or it may be because There are some frictions during work, and there are many problems that cause parts damage. The key is to find the correct way to deal with it. The specific methods are as follows:

1. Due to the overheating and squeezing of its parts during operation, the mechanical properties of the surface change and damage: This type of damage is called files, abrasive blocks and other tools or other instruments to determine the hardness change of the surface. Use your eyes to observe the extrusion of parts. When there are these defects, even if the wear of the size and shape of the parts does not exceed the allowable range, depending on the impact of the mechanical properties of the surface on the coupling, sometimes the parts have to be deemed scrapped. .

2. Due to the external force acting on the parts of the coupling during operation, the parts are bent, twisted, elliptical or other abnormally shaped changes. This change is usually called the exact geometric shape loss of the parts: the measurement of this type of damage The method is basically the same as the similar measurement method. The deformation of parts such as bending can sometimes be checked with a dial indicator on a lathe.

3. Other surface damages, such as erosion, erosion, etc.: This type of damage can be observed with eyes.It is mainly to determine whether the degree of damage and the resulting dimensional changes are within the allowable range of the quality requirements, and then determine whether the part is scrapped or not.

4. Overall damage: The parts of the coupling have cracks, honeycombs, chipping, breakage and other phenomena, resulting in mechanical and chemical reasons for the overall damage. For the coupling, it is mainly caused by mechanical reasons. The parts are under cyclic loading. Under the action, especially under the action of variable load, the resulting material fatigue phenomenon is the main reason for the overall damage of the machine.Of course, the fatigue failure mechanism of materials is complicated. However, experience has shown that poor design of parts, poor manufacturing quality, improper installation or use are often specific reasons for mechanical overall damage.

Reasons for star coupling:

1. The quincunx-shaped elastic piece of the star coupling is generally made of polyester polyurethane (hardness code a) or cast nylon (hardness code b). The load capacity of the former is lower than the latter.The semi-coupling and flange connection materials are 45 steel or ZG70-500. In the chemical industry, this phenolic resin is often used to make semi-couplings.

2. The star coupling has torsion flexibility, vibration absorption, maintenance-free, compact design and low inertia.

3. The structure of the star coupling is simple, the number of parts is small, the radial dimension is small, and no lubrication is required; the elastic element has a high load bearing capacity under pressure.Except for the double-flange plum blossom elastic coupling, the half coupling must be moved axially when replacing the wearing parts plum blossom elastic parts.This coupling has the ability to compensate for the relative offset of the two shafts.

4. The cross-section of the plum petals of the star coupling is usually circular, which can improve the uniformity of the load distribution on the working surface, and can transmit larger torque, but the elasticity is slightly reduced.It can also be made into a rectangle or fan shape.When the coupling is working, the plum petals are squeezed, and only half of the plum petals carry work.

5. The star coupling has two structural forms: casting material and steel material.Steel material is suitable for high-load drive units, such as rolling mills, elevators, spline bushings, etc.Torque range: 5Nm--35000Nm.