Countermeasures for FYH Bearings with Pillow Blocks under Thermal Action

Generally, more than 2 FYH rolling bearings with block are used on one shaft. When the installation interval of the rolling bearing with house is small or the expansion and contraction of the shaft due to temperature is small, each bearing assembly can be installed as a fixed end. However, when the installation interval is large or the shaft is subjected to heat, one bearing with a house can be installed as a fixed end to determine the position of the shaft, and the other FYH bearing with a house can be installed as a free end. This is because the shaft will elongate in the axial direction when subjected to heat, so that a large axial load will act on the bearing, and there is a danger of early damage to the bearing. Therefore, the expansion and contraction of the shaft can be absorbed by the free end bearing block. The relationship between the temperature rise and the elongation of the shaft is shown in Equation (9.1). When the shaft expands and contracts greatly due to heat, the countermeasures are as follows. (1) The method of using a set screw with a pin at the top of the free end When the shaft is elongated due to thermal action, the shaft or the seated bearing must be installed so that it can move freely in the axial direction. When the rotation speed is low, the free end assembly adopts the method of machining a keyway on the shaft and installing a set screw (special symbol G6) with a pin on the top of the bearing. Insert the pin at the top of the set screw into the keyway of the shaft to guide the axial movement of the shaft. The free end assembly has a keyway machined on the shaft, using a set screw with a pin on the top as shown in Figure 9.1. Table 9.7 shows the keyway dimensions for the set screw with a pin at the tip. When using this method, h7 is recommended for the tolerance zone of the shaft used in the free end assembly. When the temperature of the shaft is higher than the temperature of the inner ring of the bearing, the shaft used should adopt a tolerance zone that can form a larger fitting clearance. In addition, for the free end assembly using this method, the mating surface of the bearing inner ring and the shaft may sometimes be eroded. In order to prevent the occurrence of abrasion, it is recommended to apply grease to the inner diameter of the bearing when mounting the bearing with a house. (2) In applications where the rotation speed is high or there is vibration, the method of using a ring seat bearing at the free end is recommended to use a ring seat bearing at the free end. The mechanical mounting hole and the outer diameter surface of the bearing housing can be placed between Axial relative movement. Figure 9.2 shows an example of a structure using an FYH ring housing bearing as a free end assembly. When a bearing with an annular seat is subjected to heat, it is necessary to take countermeasures against the axial expansion and contraction of the shaft, and at the same time, it is necessary to calculate the amount of reduction in the internal clearance of the bearing, and select the internal clearance of the bearing correctly (refer to 7 Operating Temperature and Bearing Specifications).