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Bearings when selecting and operating
Source: Bearing network time: 2014-06-13
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For the selection of bearings; demand analysis of many factors; research from various viewpoints, evaluation of procedures for the selection of bearings; no unique norms; but usually in the following order:
(1) Grasp the operating conditions of mechanical equipment and bearings, etc.
(2) Clear bearing requirements
(3) Type of selected bearing
(4) Selected bearing equipment measures
(5) Selected bearing scale
(6) Selected bearing specifications
(7) Equipment method for selecting the bearing The operating conditions and environmental conditions of the bearing are correctly grasped. The operating position, operating conditions and environmental conditions of the bearing in the mechanical equipment are the conditions for selecting the suitable bearing. For this, the following data are obtained and material:
(1) Function and layout of mechanical equipment
(2) The operating part of the bearing
(3) Bearing load (size, direction)
(4) Rotation speed
(5) Oscillation, shock
(6) Bearing temperature (ambient temperature, temperature rise)
(7) Ambient atmosphere (corrosive; hygienic; smooth)
The selection of bearing equipment is usually; the shaft is supported by two bearings in radial and axial directions; at this moment; the bearing on one side is called the fixed side bearing; it accepts both radial and axial loads; The effect of the relative axial displacement between the bearing housing. The other side is referred to as the free side; only the radial load is accepted; the axial direction can be relatively moved; to deal with the elastic portion of the shaft that occurs due to temperature changes and Equipment bearing spacing error.
For fixed-side bearings; it is necessary to select bearings that can be moved in the axial direction (such as cylindrical roller bearings) or moved on the surface of the equipment (such as radial ball bearings). On the shorter shaft; the fixed side and the free side are not In other conditions; use only one-way fixed axial displacement bearings (such as radial thrust ball bearings).
Bearing type of selected <br> the selection of the bearing type; grasp all the conditions of use of the bearing is critical following table lists the primary analysis of the project:
| Anatomy project | Selection method | |
| 1) Bearing equipment space | Bearing type that can be accommodated in the bearing equipment space | Because the shafting is focused on the rigidity and strength of the shaft; therefore, the shaft diameter is usually determined first; that is, the bearing inner diameter. However, there are various scale series and types of rolling bearings; the most suitable bearing type should be selected. |
| 2) Load | The size, direction and nature of the bearing load [bearing load can be indicated by the fundamental additional load; its value is shown in the bearing scale table] | Bearing load is subject to change; such as the size of the load, whether the radial load, the axial load is one-way, the degree of bidirectional, oscillating or impact, etc. After thinking about these factors; then pick the most suitable bearing type Generally speaking, the radial load of the bearing of the same inner diameter can be added in the following order: deep groove ball bearing < angular touch ball bearing < cylindrical roller bearing < tapered roller bearing < spherical roller bearing |
| 3) Speed | The type of bearing that can be used to the mechanical speed [the limit value of the bearing speed is indicated by the limit speed; its value is shown in the bearing scale table] | The limit speed of the bearing is not only determined by the bearing type but also the bearing scale, the bracket type, the accuracy grade, the load condition and the smooth method; therefore, it is necessary to consider these elements when selecting. The following bearings are mostly used for high-speed rotation: deep groove ball bearings , angular touch ball bearing, cylindrical roller bearing |
| 4) Rotation accuracy | Bearing type with the required rotation accuracy [Scale accuracy and rotation accuracy of bearings have been standardized by GB according to bearing type] | Machine tool spindles, gas turbines and control machines are required to have high rotational accuracy, high speed and low conflict; in this case, bearings with a precision of 5 or more should be used. The following bearings are usually used: deep groove ball bearings, touch ball bearings, cylindrical roller bearings |
| 5) Rigidity | Bearing type that satisfies the required rigidity of the mechanical shafting [When the bearing receives the load; the touch of the rolling body and the raceway may be elastically deformed. "High rigidity" means that the amount of deformation of the elastic deformation is small] | In the machine tool spindle and the final stage of the vehicle, etc.; in the rigidity of the progressive shaft; it is also necessary to improve the rigidity of the bearing. The roller bearing receives the load and the deformation is smaller than the ball bearing. Preloading the bearing (negative clearance) Can improve the rigidity. This method is suitable for angular touch ball bearings and tapered roller bearings. |
| 6) Relative skew of the inner and outer rings | Analyze the factors that make the inner and outer rings of the bearing relatively skewed (such as the deflection of the shaft caused by the load, the poor precision of the shaft and the casing, or the equipment error); and select the type of bearing that can be used to this condition. | If the relative skew between the inner and outer rings is too large; the bearing will be damaged by the internal load. Therefore, the type of bearing that can accept this skew should be selected. Generally speaking, the skew angle (or centering angle) is allowed to be delivered in the following order. Add: cylindrical roller bearing, tapered roller bearing, deep groove ball bearing (angular touch ball bearing), spherical roller (ball) bearing |
| 7) Equipment and disassembly | Frequency of assembly and disassembly, etc. | Cylindrical roller bearings that can be separated from the inner and outer rings; needle roller bearings and tapered roller bearings are more convenient. Conical bore spherical ball bearings and tapered bore spherical roller bearings have been fasteners or The withdrawal sleeve can be easily assembled and disassembled. |
And; in order to facilitate axial positioning; most of the bearings used as fixed end bearings; other used as free end bearings. The following table lists the choice of fixed end and free end bearing layout.
| content | Applicable bearing type | |
| Fixed end bearing | It is used for axial positioning and fixing of bearings. Bearings that can accept radial and axial loads are accepted for two-way axial load. The equipment also needs to consider the corresponding strength according to the axial load. | Deep groove ball bearing combination angle touch ball bearing double row angular touch ball bearing self-aligning ball bearing with rib cylindrical roller bearing (NUP type, NH type) Double row roller bearing spherical roller bearing |
| Free end bearing | Used to avoid the elasticity of the shaft caused by temperature changes during work; and to adjust the axial orientation of the bearing. It is advisable to use bearings that only accept radial loads and that can be separated from the outer and outer rings. When using non-detached bearings; the gap between the outer ring and the outer casing is usually used for cooperation; so that the shaft can be elastically evaded together with the bearing. | Used to avoid the elasticity of the shaft caused by temperature changes during work; and to adjust the axial orientation of the bearing. It is advisable to use bearings that only accept radial loads and that can be separated from the outer and outer rings. When using non-detached bearings; the gap between the outer ring and the outer casing is usually used for cooperation; so that the shaft can be elastically evaded together with the bearing. |
| Regardless of the fixed end and the free end | When the bearing spacing is small and the influence of shaft elasticity is not large; two angle touch ball bearings or tapered roller bearings that can accept axial load are used for front or back equipment. Adjust the axial clearance after the device with a nut or washer. | Deep groove ball bearing angle touch ball bearing self-aligning ball bearing cylindrical roller bearing (NJ type, NF type) Tapered roller bearing spherical roller bearing |
| For vertical axis | The fixed end is selected to be a bearing that can receive both radial and axial loads. When the axial load of the bearing is large, the thrust bearing and the radial bearing are used together. Bearings that can only accept radial loads are used at the same free end; to avoid the elasticity of the shaft. | Fixed end combined angular touch ball bearing (reverse combination) Double row tapered roller bearings (37000 type) Thrust bearing and radial bearing |
- Method
Pressing the inner ring of the cooperative bearing and the shaft to make a tight cooperation; when the outer ring and the bearing housing hole are loosely engaged; the bearing can be first pressed on the shaft by the press; then the shaft is loaded into the bearing housing hole together with the bearing; Mounted on the end face of the bearing inner ring; padded with a soft metal material equipment casing (copper or mild steel).
The outer ring of the bearing is tightly cooperated with the hole of the bearing seat; when the inner ring and the shaft are loosely engaged; the bearing can be first pressed into the hole of the bearing seat; at this time, the outer diameter of the casing of the device should be slightly smaller than the diameter of the seat hole.
If the bearing ring and the shaft and the seat hole are tightly cooperated; the inner and outer rings of the equipment should be pressed together into the shaft and the seat hole; the layout of the equipment casing should be able to hold the end faces of the inner and outer rings of the bearing together.
Heating cooperation through heated bearings or bearing housings; using thermal expansion to transform tight cooperation into loose cooperation equipment. It is a common and labor-saving equipment method. This method is suitable for equipment with large interference bearing; before hot loading The bearing or the ferrule of the separate bearing is placed in the fuel tank and heated evenly at 80-100 ° C; then it is taken out from the oil and quickly loaded onto the shaft; in order to avoid the cooling, the end face of the inner ring and the shoulder are not tight; after the bearing is cooled, Then the axial fastening is carried out. When the outer ring of the bearing is tightly cooperated with the bearing seat made of light metal; the hot-filling method of the heated bearing seat is adopted; the cooperating surface can be prevented from being scratched.
When heating the bearing with the oil tank; there should be a grid at a certain distance from the bottom of the box; the bearing should be hung with a hook; the bearing should not be placed on the bottom of the box; to prevent the sinking of impurities into the bearing or uneven heating; a thermometer is necessary in the fuel tank; Strictly control the oil temperature should not exceed 100 ° C; to avoid the tempering effect; the hardness of the ferrule is reduced.
Thrust bearing equipment The full cooperation of the thrust bearing with the shaft is usually a transitional cooperation; the cooperation between the seat and the bearing housing hole is usually the cooperation of the gap; therefore, the bearing is easier to install; the shaft spring of the bidirectional thrust bearing should be fixed on the shaft. ; to avoid correlation with the axis transformation.
The equipment method of the bearing; under normal conditions, the shaft rotation is mostly; therefore, the cooperation between the inner ring and the shaft is a win-win cooperation; the cooperation between the outer ring of the bearing and the bearing chamber is the cooperation of the gap.
- Bearing work view
Bearing use and storage
(1) When the bearing is used; adhere to the cleanliness of the surrounding environment; do not stick to the hand sweat and dirt. The rules are used by the personnel who understand the bearing; the unique requirements are careful injury, indentation, damage, etc. To ensure the function of the bearing; The operation specifications of the equipment are covered; the bearings are protected, protected and overhauled at regular intervals; the contents include monitoring the operation status, making up for the smoothing agent, and taking time to open and view.
(2) Bearings should not be stored directly on the ground (more than 30cm above the ground); avoid direct light and cold walls. To avoid rust; store in an environment with a temperature of about 20 ° C and a humidity of less than 65%; the bearings are placed in acid In the air; simple rust, discoloration; use gloves, kapok yarn to scrub the bearings, shafts, shells; waste into the bearing and cooperation is the cause of abnormalities; therefore demand attention.
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