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Analysis: Application technology of metallurgical gearbox bearings
Source: China Bearing Network Time: 2014-06-11
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Bearing selection 1. Selecting the right bearing type Metallurgical gearbox bearings generally use a double row roller bearing combination to meet the heavy-duty and high-power power transmission requirements. Roller bearings are mainly tapered roller bearings, cylindrical roller bearings and spherical roller bearings. The bearing type of metallurgical gear box should be determined by the force condition of the gear shaft and the characteristics of various bearings. The double row tapered roller bearing has outstanding radial and axial composite load; the internal clearance of the bearing can be Adjustment; and help to enhance the rigidity of the transmission; therefore, tapered roller bearings are the type of bearing that metallurgical gearboxes delineate. But tapered roller bearings also have shortcomings; for example, higher prices and no self-aligning and anti-migration Therefore, many types of bearings are also used in metallurgical gearboxes; such as self-aligning or cylindrical roller bearings.
Metallurgical gearboxes often use different types of bearings to achieve the best intention of depicting. Compared with tapered roller bearings; spherical roller bearings have lower cost; the bearings can also accept axial axial composite loads under specific stress conditions. The biggest advantage of spherical roller bearings is self-aligning ability; it can work normally under the condition of partial pain. When the bearing is near the outer dimension; double row cylindrical roller bearings can be used to obtain higher radial bearing capacity; This type of bearing can not accept the axial load. Generally, when the cylindrical roller bearing is used for the radial and axial composite load conditions, it is required to add a thrust bearing or other type of bearing to accept the axial load.
2. When the double row tapered roller bearing combination method adopts the double row tapered roller bearing combination, one end of the bearing is generally set as the "fixed end"; that is, the end faces of the inner and outer rings of the bearing are all tightly packed without leaving a gap; The load effect, the other end of the bearing is "floating end"; used to absorb the gear shaft thermal expansion and accumulation of public service. "Floating end" bearings only accept radial load; bearing outer ring end face and bearing end cover and shoulder Should meet the clearance; to offset the axial displacement of the gear shaft after the thermal expansion; the detailed layout is shown in Figure 1. The torque is transmitted for progress; many metallurgical gearboxes use the helical gear meshing method. Under heavy load conditions; The helical gear is not easy to attack shock oscillation noise, the operation is stable and the bearing capacity is large; therefore, the helical gear is superior to the spur gear transmission under heavy load transmission conditions.
Figure 1 The gearbox uses a double-row tapered roller bearing combination method. However, when the helical gear meshes, additional axial thrust will occur and the effect will be on the “fixed end†bearing. When the axial thrust is large, the double-row tapered roller bearing is selected as the double-row tapered roller bearing. "Fixed end"; perhaps adding a thrust bearing is a ambition solution. When the gear shaft is only a single helical gear meshing; and the gear shaft "fixed end" uses a spherical roller bearing; attention should be paid to the maximum axial bearing of the bearing The ratio of the radial force is related. The spherical roller bearing has its own layout characteristics; when the axial force of the bearing exceeds the radial force itself by 1/3 or 1/4 (depending on the detailed bearing series); The bearing will exhibit a single-sided roller force; the other side of the roller will be unloaded. The force-free roller cannot be guided and positioned in the raceway during the rotation; the roller is tilted, the slip and the impact cage are presented. Condition; can cause cracking of the cage when severe; bearing early failure. Double row tapered roller bearings are selected by pure tumbling and roller end ribs; after handling bearing device clearance; can be used for large axial force and single row rolling Sub-bearer The characteristics and differences of the two types of bearings can be seen in Figure 2. The "fixed end" bearing accepts the axial axial composite load; in order to divide the shaft receiving force and improve the service life; the "fixed end" is generally placed in the radial direction. The side with less force; the "floating end" is placed at the end of the radial force. Sometimes the spherical roller bearing is used to improve the axial bearing capacity of the bearing; the "fixed end" is also placed in the radial direction. The side with greater force; in this case; the "fixed end" spherical roller bearing bearing capacity should be higher than the "floating end" bearing.
Figure 2 Difference between spherical roller bearings and double row tapered roller bearings. Thinking practice conditions and axial load cone-type bevel gear transmission are similar to helical gears; large axial loads will also occur when gears mesh; bearing selection should also refer to practical conditions and axial load size. Herringbone gears The transmission can be used as a pair of bevel gears that are used in pairs but rotate in opposite directions; the axial thrust is not generated when the herringbone gears mesh; it is widely used in the gearbox of the rolling mill. When the gear is meshed with the herringbone gear; the input and output shafts only need to be Set a “fixed end†axial positioning gear; other orientations should be set to “floating endâ€. “Floating end†bearings can be used with cylindrical or spherical roller bearings; “fixed ends†should be axially loaded. Can be a strong double-row tapered roller bearing. Bearing optimization selection description is shown in Figure 3; "floating end" bearings are selected for single row cylindrical roller bearings. Other; in high-speed rod and wire mill gearbox operation; high speed The input shaft often uses specially-lined double-row tapered roller bearings to serve as harsh bearing conditions such as high speed, frequent acceleration, deceleration, forward rotation and rotation.
Figure 3 Optimized selection of herringbone gear transmission bearings 4. Considering the bearing capacity of the bearing, in addition to the correct selection of the bearing type; whether the selected bearing can meet the bearing capacity is also a key factor to consider. Calculating the bearing capacity of the bearing to obtain the theoretical life of the bearing is the most commonly used measure bearing bearing. The method of talent. Metallurgical gearboxes are used according to different requirements; generally there will be a minimum theoretical life expectancy of bearings; for example, some gearboxes require a bearing with a minimum life of not less than 50,000 h; some applications require no less than 30,000 h. Generally, when calculating the bearing life; in order to obtain the life of the bearing; the general bearing rotation speed is selected to replace the maximum rotation speed. The gearbox transmission is under power stability; the rotation speed will lead to torque improvement; Will lead to the acceptance of the shaft becomes larger. The bearing life is related to the rotation speed in a 1:1 inverse ratio; but it is related to the force 10 times; that is, the shaft receiving force is doubled; the bearing life will be reduced by 10 times. About some overloads And the use of lower speed; theoretical bearing life results can not really reflect the bearing function; generally the primary consideration is whether the ratio of bearing extra equivalent and shaft receiving force can be large The safety factor; a more accurate method is to calculate the maximum contact stress of the bearing roller through the analysis software.
Bearings for public service cooperation Metallurgical gearbox bearings are generally in the harsh working environment such as heavy load, impact load, high speed or low speed; correctly select the bearing public service cooperation not only for the bearing device; together can guarantee heavy load and impact load Under the condition, the bearing will not show the running condition. Generally speaking, the bearing rotating parts are selected for interference cooperation; the non-moving parts are selected to cooperate with the gap. The bearing practice cross-over cooperation scale is not only changed according to the bearing size; and in heavy load and high speed Under the application conditions, the interference cooperation should be selected more than the conventional application conditions. When the inch tapered roller bearing is used, the difference between the English bearing and the metric bearing itself should be paid attention to and the common shaft and the bearing seat should be adjusted accordingly. Scale. The size of the inner and outer ring diameter of the inch bearing is “plus public serviceâ€; it is the opposite of the metric bearing. If the shaft and the housing are still in accordance with the metric bearing, (18) Pu's heart and heart.æ¦è§¯ è´¾ è´¾ å²¢ å²¢ å²¢ 馊Π沧袄 è°Œ è°Œ è°Œ 英 英 英 英 英 英 英 英 英 英 英 英 英 英 英 英 英 英 英 英Scale. Compared with the British bearing; the metric large-scale bearing public service cooperation selection is relatively simple; the heavy load, the bearing inner ring rotating outer ring stop operating conditions; the inner diameter scale 320~500mm large-scale self-aligning or cylindrical roller bearing; The shaft can be used with r6 public service scale. For self-aligning or cylindrical roller bearings with an inner diameter scale exceeding 500mm; the shaft can be used with r7 public service scale. The aligning or cylindrical roller bearing housing can be selected for H7 or G7.
Bearing initial clearance Tapered roller bearing initial clearance is different from ball bearing, self-aligning and cylindrical roller bearing; it refers to axial clearance (BEP); other bearings are radial clearance (RIC). Bearing The initial clearance determines the bearing clearance after the bearing device and the operation. The clearance of the bearing determines the large bearing load bearing area. The å²¢ è· è· èœ— 蜗 蜗 蜗 å²¢ å²¢ å²¢ å²¢ å²¢ 闯惺 闯惺 闯惺 闯惺芰 Φ 墓 鲎 鲎 æ‹· ä¼² ä¼² ä¼² ä¼² è´¾ è´¾ è´¾ è´¾ è´¾
Tapered roller bearing clearance selection can also present roller wear or impact cage; incurs the crack of the cage. The initial clearance of the bearing is too small, which will cause the bearing to heat up severely; the bearing is locked and burned. .
The initial clearance of the metallurgical gearbox bearing should be calculated according to the interference cooperation of the shaft and the maximum rotational speed of the bearing. When the inner ring of the gearbox bearing cooperates with the shaft, the outer diameter of the inner ring of the bearing will swell and eat some initial Clearance; the initial clearance minus the interference lost by the interference cooperation is the bearing clearance (MEP) of the bearing. Generally speaking, the inch double-row tapered roller bearing does not exceed 400mm on the inner diameter scale; the clearance after the device should not be More than 0. 5mm. For large-scale bearings with an inner diameter exceeding 400mm; the maximum clearance after the device can be expanded to about 0.6 mm.
Metallurgical gearbox bearing initial clearance selection generally does not consider the ambient temperature; but only consider the difference between the inner and outer ring temperature of the bearing; because the ambient temperature will cause the shaft to swell; but the influence of the ambient temperature of the bearing seat will also cause thermal expansion. Bearing device After the clearance (MEP), the clearance between the inner and outer rings of the bearing is reduced; the end bearing bearing clearance (OPE) is obtained. The metallurgical gearbox large tapered roller bearing is for safety thinking; Negative clearance is not allowed. The selection of the initial clearance of metric cylindrical and spherical roller bearings is similar to that of tapered roller bearings, but it is more simple; generally speaking, for large scale, inner ring interference cooperation, outer ring clearance cooperation and heavy load Operating conditions; bearing initial clearance can be used to standardize the size of C3 clearance.
Bearing device scale bearing device size mainly includes the shoulder and bearing seat shoulder diameter scale; and the maximum chamfer radius of the shaft and bearing housing. About tapered roller bearings; device dimensions also include cage safety clearance dimensions. Shaft shoulder and housing The diameter of the shoulder should be strictly selected according to the bearing demand. Actually, a certain fan, a fan, a V, a 嗣嬗 嗣嬗 嗣嬗 愎 愎 哟ッ婊桓 齿轮 齿轮 齿轮 齿轮 齿轮 齿轮 齿轮. Gear shaft and bearing housing The maximum chamfer radius should be smaller than the inner and outer ring chamfering radius of the bearing itself; the chamfering radius of the shaft and the bearing seat may cause the bearing to be in place; the inner and outer rings are inclined; affecting the normal operation of the bearing. Totally; when depicting the metallurgical gearbox; Pay attention to the scale of the device; do not add or cut the rule scale.
The harsh working environment of the metallurgical gearbox puts more stringent demands on the bearing used. The selection of high-performance bearings and the correct use of the bearing are prerequisites for ensuring the safe operation of the gearbox. This paper has selected the bearing for the metallurgical gearbox. The key tasks of public service cooperation, initial clearance and device scale are briefly analyzed; for metallurgical gearbox depicting personnel and equipment protection personnel.
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