CouplingThe assembly on the shaft is one of the keys to the installation of the coupling.Most of the couplings and shafts are fitted with interference fits. The couplings are divided into keyed and non-keyed connections. The shaft holes of the coupling are divided into cylindrical shaft holes and tapered shaft holes.The assembly methods are: static press-in method, dynamic press-in method, temperature difference assembly method and hydraulic assembly method.
1. The static press-in method is carried out with clamps, jacks, manual or motorized presses according to the required press-in force during assembly. The static press-in method is generally used for tapered shaft holes.Because the static press-in method is restricted by the force machine, it is difficult to apply a large force when the interference is large. At the same time, the small unevenness between the coupling and the shaft will be cut off during the press-in process. The convex peaks cause damage to the fit. Therefore, this method is generally not used much.
2. The power press-in method refers to the use of impact tools or machinery to complete the assembly process. It is generally used in situations where the coupling and shaft fit is transitional or has little interference. The assembly site is usually hammered. .The method is to put wooden blocks or other soft materials on the end surface of the hub as a buffer, and rely on the impact force of the hand hammer to knock the coupling in.This method has the risk of local damage to couplings made of brittle materials such as cast iron, quenched steel, and cast alloys.Should not be used.This method will also damage the mating surface, so it is often used for the assembly of low-speed and small couplings.
3. Temperature difference assembly method: The coupling is heated and expanded by heating or the shaft end is cold and contracted by cooling, so that the wheel coupling can be easily installed on the shaft.This method has more advantages than static press-in method and dynamic press-in method.For hubs made of brittle materials, the use of temperature difference assembly method is very suitable, the temperature difference assembly method mostly uses heating methods, cooling methods are less used, there are many heating methods, and some put the hub into high flash Oil bath heating or welding torch baking is performed in the spot oil, and some are heated in an oven. Oil bath heating and welding torch baking are often used in the assembly site.The maximum temperature that the oil bath can reach depends on the nature of the oil, generally below 200°C. When other methods are used to add the hub, the temperature of the coupling can be higher than 200°C, but from the perspective of metallography and heat Considering that the heating temperature of the coupling cannot be increased arbitrarily. The recrystallization temperature of steel is 430℃, which will cause changes in the internal structure of the steel. Therefore, the upper limit of the heating temperature must be less than 430℃, which will cause changes in the internal structure of the steel. The upper limit of the heating temperature must be 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 and fitted onto the shaft.