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Conditions and technical parameters required for cold and hot mounting of the shaft hole of the coupling

Publication time: November 2016, 11【L Small

  When selecting a standard coupling or designing a special coupling, first find out the torque that the coupling actually needs to transmit.For the standard coupling, the allowable torque value has been set for each model. Therefore, when selecting the model, the torque that the coupling actually needs to transmit should be less than the allowable torque of the selected coupling [T].The torque that the coupling actually needs to transmit is often used to calculate the torque T0.Indicates that it is equal to the theoretical torque T of the coupling multiplied by the working condition coefficient K.Therefore, the above condition can be expressed as: T0=KT.

  Most of the commonly used couplings have been standardized. Generally, they can be selected directly from the standard. The steps of the selection are: first select the type and model, and then perform the necessary strength check.Coupling temperature difference assembly method is to use heating method to make the coupling heat expansion or cooling method to make the shaft end cold and shrink, so that the wheel coupling can be easily installed on the shaft.This method has more advantages than the static press-in method and the dynamic press-in method. For the wheel hub made of brittle materials, the temperature difference assembly method is very suitable.The temperature difference assembly method mostly adopts heating method, and the cooling method is less used.There are many heating methods. Some put the wheel hub in high flash point oil for oil bath heating or welding torch baking, and some use an oven to heat it. The assembly site uses oil bath heating and welding torch baking.

  The high temperature that the oil bath can reach depends on the nature of the oil, and it is generally below 200°C.When other methods are used to heat the hub, the temperature of the coupling can be higher than 200°C, but from the perspective of metallography and heat treatment, the heating temperature of the coupling cannot be increased arbitrarily, and the recrystallization temperature of steel is 430°C.If the heating temperature exceeds 430°C, it will cause changes in the internal structure of the steel. Therefore, the upper limit of the heating temperature is less than 430°C.For insurance, the upper limit of heating temperature should be below 400℃.As for the actual heating temperature of the coupling, it can be calculated according to the interference value of the coupling and the shaft and the requirements when the coupling is heated on the shaft.

  Inspection after assembly: After the coupling is assembled on the shaft, the verticality and coaxiality of the coupling and the shaft should be carefully checked.Generally, two dial indicators are set on the end face and outer circle of the coupling. When the shaft is turned by the turning car, observe the value of the total runout (including end runout and radial runout) of the coupling to determine the coupling and the shaft. The verticality and concentricity of the situation.High-speed rotating machinery requires high coaxiality between the coupling and the shaft, and high coaxiality cannot be obtained with a single key connection, and the coaxiality of the two can be improved by using a double key connection or a spline connection.

Keywords of this article:Plum coupling | Oldham coupling | Pin coupling |