2.1 Precautions for use Rolling
bearings are precision parts. Therefore, it is required to be cautious when using them. Even if high-performance bearings are used, if they are not used properly, the expected performance effects will not be achieved. Therefore, the following matters should be noted when using bearings. :
2.1.1 Keep the bearings and their surroundings clean. Even if the smiling dust that is invisible to the naked eye enters the bearing, it will increase the wear, vibration and noise of the bearing.
2.1.2 Care should be taken when using the installation. Strong stamping is not allowed. It is not allowed to directly hit the bearing with a hammer. It is not allowed to transmit pressure through the rolling elements. 2.1.3 Use appropriate and accurate installation tools, try to use special tools, and try to avoid the use of cloth and short fibers.
2.1.4 Prevent the corrosion of the bearing. When taking the bearing directly by hand, wash off the sweat on the hand and apply it with high-quality mineral oil before handling. In the rainy season and summer, pay special attention to rust prevention.
2.2 Cooperation
2.2.1 Selection of the fit The inner diameter and outer diameter of the rolling
bearing are manufactured according to standard tolerances. The tightness of the inner ring of the bearing and the shaft and the outer ring and the seat hole can only be achieved by controlling the tolerance of the journal and the tolerance of the seat hole. achieve. The inner ring of the bearing and the shaft are matched by a base hole, and the outer ring of the bearing and the seat hole are made by a shaft. The common fit of rolling bearings is shown in Figure 2-1. The correct choice of fit, you must know the actual load conditions, operating temperature and other requirements of the bearing, but it is actually very difficult. Therefore, most of the cases are based on the use of lint selection.
2.2.2 Load properties The choice of coordination should first consider the rotation of the load vector relative to the ferrule. According to the rotation of the synthetic radial load vector with respect to the ferrule, the load on the ferrule can be divided into: fixed load, rotary load and oscillating load, as shown in Figure 2-2.
a. The combined radial load acting on the ferrule by the fixed load is carried by the local area of the ferrule raceway and transmitted to the corresponding local area of the shaft or housing. This load is called a fixed load. It is characterized by a synthetic radial load vector and a relatively stationary ferrule. The ferrules that are subjected to directional loads can be loosely fitted.
b. The combined radial load acting on the ferrule by the rotating load rotates in the circumferential direction of the raceway, which is sequentially carried by each part. This load is called the rotating load and is characterized by the synthetic radial load vector rotating relative to the ferrule. . The ferrules subjected to the rotating load should be tightly fitted. In special cases, such as the load is very light, or the ferrule only rotates at a low speed occasionally under heavy load. When the bearing is made of harder material and the surface roughness is higher, it is subjected to the rotating load. The ferrule can also be used with a loose fit.
c. The direction of the synthetic radial load acting on the ferrule is uncertain. This load condition is called oscillating load or non-directional load. It is characterized by the synthetic radial load vector on the ferrule being fixed in the ferrule raceway. The swing in the area is carried by a certain area of the raceway, or the load acting on the bearing is an impact load, a vibration load, a direction, and a load whose value frequently changes. The bearing in the bearing, the outer ring and the circumference, the bearing seat and the hole should be tightly matched by the oscillating load.
2.2.3 Load size The amount of over-win between the ferrule and the shaft or casing depends on the size of the load. The heavier load uses a larger over-win, and the lighter load uses a smaller over-win. The equivalent radial load p is usually divided into three cases of “light”, “normal” and “heavy” load, and its relationship with the rated dynamic load c of the bearing is listed in Table 2-1 for the selection of the shaft and the seat hole tolerance band. reference.
2.2.4 Shaft and Housing Hole Tolerance Band Selection Depending on the size and nature of the load, the tolerances for the shaft and control are specified in Table 2-2 - Table 2-4. 2.2.5 Surface roughness and shape tolerance The surface roughness and shape tolerance directly affect the product's performance, such as wear resistance, corrosion resistance and compounding properties. For this reason, it is important to reasonably specify the geometrical tolerances of the shaft and the housing hole and the roughness requirements of the mating surface. For the stable mating property, it is important to improve the joint strength of the over-winning fit.
See Table 2-5 - Table 2-6 and Figure 2-3 for the mating surface roughness and shape tolerance of the shaft and housing holes
2.3 Bearing installation Whether the bearing installation is good or bad will affect the accuracy, life and performance of the bearing. Therefore, please fully study the installation of the bearing, that is, install the bearing in accordance with the operating standards including the following items.
2.3.1 Cleaning the bearings and related parts. (For grease-lubricated bearings and double-sided oil seals or dust caps, seal bearings are not required to be cleaned before installation.) 2.3.2 Checking the dimensions and finishing of related parts
2.3.3 Installation method The installation of the bearing should be based on the bearing structure, size and the matching nature of the bearing components. The pressure should be directly applied to the end face of the tightly fitting ferrule. The pressure should not be transmitted through the rolling element. The bearing installation generally adopts the following method. :
a. The inner ring of the press-fit bearing is tightly fitted with the shaft. When the outer ring and the bearing housing hole are loosely fitted, the bearing can be press-fitted onto the shaft by a press, and then the shaft is fitted into the bearing housing hole together with the bearing. As shown in Figure 2-4, the mounting sleeve (copper or mild steel) made of soft metal material is placed on the end face of the inner ring of the bearing during press fitting. The inner diameter of the fitting sleeve should be slightly larger than the diameter of the journal, and the outer diameter should be slightly smaller than the inner ring of the bearing to prevent it from being pressed against the cage. The bearing outer ring is tightly matched with the bearing housing hole. When the inner ring and the shaft are loosely fitted, the bearing can be first pressed into the bearing housing hole. At this time, the outer diameter of the assembly sleeve should be slightly smaller than the diameter of the seat hole, as shown in FIG. 2 5 is shown. If the bearing ring and the shaft and the seat hole are tightly fitted, the inner ring and the outer ring should be pressed into the shaft and the seat hole at the same time. The structure of the assembly sleeve should be able to simultaneously tighten the end faces of the inner ring and the outer ring of the bearing, such as Figure 2-6 shows.
b. Heating and fitting The heating method is used to convert the tight fit into a loose fit by heating the bearing or the bearing housing. It is a common and labor-saving installation method. This method is suitable for the installation of bearings with large interference. Before the hot assembly, put the bearing or the ferrule of the separable bearing into the fuel tank and heat it evenly at 80-100 °C, then take it out of the oil and load it on the shaft as soon as possible. After the cooling is prevented, the inner ring end face and the shoulder are not tightly attached, and the bearing can be axially fastened after cooling. When the outer ring of the bearing is tightly fitted with the bearing seat made of light metal, the hot-filling method of the heated bearing seat can avoid the abrasion of the mating surface. When heating the bearing with the fuel tank, there should be a grid at a certain distance from the bottom of the box, as shown in Figure 2-7, or the bearing is hung with a hook. The bearing cannot be placed on the bottom of the box to prevent impurities from entering the bearing or uneven heating. There must be a thermometer in the fuel tank, and the oil temperature should not be strictly controlled to exceed 100 °C to prevent the tempering effect and reduce the hardness of the ferrule.
c. Installation of tapered bore bearing The tapered bore bearing can be mounted directly on the tapered journal or on the tapered surface of the adapter sleeve and the withdrawal sleeve. The tightness of the fit can be reduced by the radial clearance of the bearing. Measure, therefore, the radial clearance of the bearing should be measured before installation. The clearance should be measured frequently during the installation to achieve the required clearance reduction. The installation is usually done with a lock nut or a heating installation. .
d. Installation of thrust bearing The circumference of the thrust bearing and the shaft are generally matched. The fit between the race and the bearing bore is generally clearance fit. Therefore, the bearing is easier to install. The shaft spring of the double-way thrust bearing should be on the shaft. Fixed on top to prevent rotation relative to the shaft. The mounting method of the bearing is generally the case where the shaft rotates. Therefore, the cooperation between the inner ring and the shaft is a win-win cooperation, and the cooperation between the outer ring of the bearing and the bearing chamber is a clearance fit.
2.3.4 Inspection after bearing installation
2.3.5 Addition of lubricant
2.4 Bearing operation check After the installation of the bearing is completed, the operation check should be carried out immediately to determine whether the installation is normal.
