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Installation of rolling bearings - the matching of rolling bearings

Installation of rolling bearings - the matching of rolling bearings

2021-07-21

Bearing installation is good or bad, will affect the accuracy, life, and performance of bearings. Therefore, please fully study the installation of bearings, that is, please carry out the installation of bearings in accordance with the operating standards including the following items.1. Cleaning bearings and related parts. For bearings with grease lubrication and oil seals or dustproof caps on both sides, there is no need to clean the sealing ring bearings before installation. The installation of the bearing shall be determined according to the bearing structure, size, and matching nature of the bearing parts. The pressure shall be directly added to the end face of the tightly matched ring, and the pressure shall not be transmitted through the rolling body. 


The following methods are generally adopted for the installation of the bearing: a.Force fit tight fit bearing inner ring and the shaft, the outer ring and the bearing hole is a loose fit, press the bearing to be pressed on the shaft are available, and then put the shaft together with the bearing load bearing hole, when pressed on the bearing inner ring end face, cushion the assembling casing made of a soft metal material (copper or mild steel), the inner diameter of the casing assembly should be slightly larger than the diameter of a journal, The outer diameter should be slightly smaller than the bearing inner ring to avoid pressing on the retainer. 


The outer ring of the bearing is tightly matched with the bearing seat hole. When the inner ring and the shaft are loosely matched, the bearing can be pressed into the bearing seat hole first. At this time, the outer diameter of the assembly sleeve should be slightly less than the diameter of the seat hole. 


If the bearing ring is tightly matched with the shaft and the seat hole, the inner ring and the outer ring should be pressed into the shaft and the seat hole at the same time, and the structure of the assembly sleeve should be able to press the end face of the inner ring and the outer ring of the bearing at the same time.B. Heating fit An installation method that converts tight fit into a loose fit by heating the bearing or bearing seat and using thermal expansion.It is a common and labor-saving installation method. This method is suitable for the installation of bearings with a large interference amount. Before hot loading, put the rings of bearings or separable bearings into the oil tank for uniform heating of 80-100℃, and then take them out of the oil and install them on the shaft as soon as possible. 


In order to prevent the end face of the inner ring and the shaft shoulder from fitting tightly after cooling, the bearings can be tightened axially after cooling. When the outer ring of the bearing is tightly matched with the bearing seat made of light metal, the hot charging method of heating the bearing seat is adopted to avoid the scratch on the matching surface. Heating tank with bearing and should be at a certain distance from the bottom of a mesh, or hanging hooks in the bearings, bearing on the bottom, in case of heavy impurities into the bearing or uneven heating, the fuel tank must have a thermometer, strictly control the oil temperature shall not exceed 100 ℃, in order to prevent the tempering effect, reduce the hardness of the ring.C. the installation of the cone-bearing cone hole can be directly installed in a shaft with taper bearing neck, or load set of the cone, and the withdrawal of the tightness of cooperating bearing radial clearance reduction is available to measure, therefore, before installation should be measured bearing radial clearance, the installation process should often measure the clearance in order to meet the need of clearance reduction is so far, Locknut is generally used for installation, and heating can also be used for installation.D. 


Installation of thrust bearing The balance of thrust bearing and the shaft is generally transition fit, and the balance of seat ring and bearing seat hole is generally clearance fit, so this kind of bearing is easier to install. The central shaft spring of bidirectional thrust bearing should be fixed on the shaft to prevent rotation relative to the shaft. The installation method of bearings is generally shaft rotation, so the match between the inner ring and the shaft is overmatch, and the match between the outer ring and the bearing chamber is a clearance match.

Matching of rolling bearings

First, the choice of cooperation

The inside diameter size and outside diameter size of rolling bearings are manufactured according to standard tolerances. The tightness of the bearing inner ring and shaft, outer ring, and seat hole can only be realized by controlling the tolerance of the shaft journal and seat hole. Bearing inner ring and shaft with basic hole system, bearing outer ring and seat hole with machine shaft system. The common fit of rolling bearings. To correctly choose the match, we must know the actual load conditions, working temperature, and other requirements of the bearing, but in fact, it is very difficult. Therefore, in most cases, the match is chosen according to the use of refinement.

Second, the nature of the load

The rotation of the load vector relative to the ring should be considered in the selection of fit. According to the rotation of the synthetic radial load vector relative to the ring, the load borne by the ring can be divided into fixed load, rotating load and swinging load.A. Fixed load The composite radial load acting on the ring is borne by the local area of the ring raceway and transmitted to the corresponding local area of the shaft or bearing seat. This load is called the fixed load.Its characteristic is that the resultant radial load vector is relatively stationary with the ring. 


The ring bearing directional load can choose a looser fit.B. Rotating load acts on the composite radial load on the ring and rotates along the circumferential direction of the raceway and is borne by each part in sequence. This kind of load is called the rotational load, which is characterized by the composite radial load vector relative to the rotation of the ring. The ring bearing rotating load should be tightly matched. In special circumstances, such as the load is very light, or the ring only occasionally rotates at low speed under the action of heavy load. 


When the bearing is made of harder materials and the surface is rough, the ring bearing can also choose a looser match.C. oscillating load acting on the direction of the synthesis of radial load on the ring, the load case, called oscillating load or directional load, its characteristic is the synthesis of radial load vector acting ring in the ring groove in a certain area of swing, on certain areas for the raceway, or impact load is acting on the bearing load, vibration load, its direction, Frequent variation of the value of the load. The inner and outer ring of bearing under swing load should be tightly matched with shaft and bearing seat hole.

Three, the load size

The amount of overwin between the ring and the shaft or the housing depends on the size of the load. The heavier load uses the larger amount of overwin, and the lighter load uses the smaller amount of overwin. The equivalent radial load is usually divided into "light", "normal" and "heavy" loads.5. Roughness and shape and position tolerance of the matching surface directly affect the service performance of the product, such as wear resistance, corrosion resistance, and matching properties, etc. Therefore, it is very important to reasonably stipulate the shape and position tolerance of the shaft and shell holes and put forward the requirements for the roughness of the mating surface to stabilize the mating properties and improve the bonding strength of over-winning mating.

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