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Bearing working speed
Source: China Bearing Network Time: 2014-08-27
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The speed at which the extreme operating temperature is reached depends on the heat of conflict (including any external heat) that occurs during bearing operation; and the amount of heat that can be emitted from the bearing.
The variety and dimensions of the bearing, internal depiction, load, smoothing and cooling conditions, as well as cage depiction, accuracy and internal clearance, etc., all affect the determination of the speed.
In the product table; two speeds are usually listed: (hot) see speed and (motion) limit speed; the values ​​of these two speeds depend on the specification being considered.
See speed (heat) listed in the product table. Speed ​​is a speed reference; used to determine the allowable speed of the bearing under conditions of constant load and smoother viscosity.
The listed speed values ​​are in accordance with the ISO 15312 specification (this specification does not include thrust ball bearings). This ISO specification is formulated for oil smoothing; but it is equally useful for grease smoothing.
The reference speed of a given bearing represents its speed under certain operating conditions. At this speed, the heat generated by the bearing is roughly balanced with the heat emitted from the bearing to the shaft, housing and smoothing agent.
According to the ISO 15312 specification; the conditions for reaching this heat balance are:
Add 50 degrees to the ambient temperature of 20 degrees Celsius; that is, the bearing temperature is 70 degrees Celsius; the measuring point is the fixed outer ring of the bearing or the bearing seat washer;
Radial bearing: a stable radial load; 5% of C0, which accounts for the extra value of the fundamental static load
Thrust bearing: a stable axial load; 2% of C0, which accounts for the extra value of the fundamental static load
Open bearings with conventional clearance for oil smooth bearings:
Smoothing agent: mineral oil without EP additive; kinematic viscosity at 70 degrees Celsius ν = 12mm2/s (ISO VG 32) (for radial bearings)
ν = 24mm2/s (ISO VG 68) for (for thrust roller bearings)
Smooth method: oil. è ¡ é” é” é” é¾†å®• 谧畹 谧畹 谧畹 æ¢ æ¢ æ¢ æ¢ æ¢ æ¢ æ¢ æ¢.
For grease smooth bearings:
Smoothing agent: Lithium soap soap rich in mineral base oil is smooth; viscosity from 100 to 200mm2/s at 40 degrees Celsius (eg ISO VG 150)
The amount of grease: about 30% of the free space inside the bearing.
When the grease smooth bearing is started; it can present a temperature peak. Therefore, the bearing can work for 10 to 20 hours to reach the normal working temperature.
Under these specific conditions; the oil is smooth and the grease is smooth and the reference speed is flat.
In the case of rotation of the outer ring of the bearing; it is necessary to reduce the extra value.
For some bearings; their speed limit is not determined by the roll/bearing raceway touch surface; the bearing table only supplies their speed limit values. These bearings include bearings with touch seals.
Constrained speed and speed constraints are determined by certain specifications. These specifications include the dimensional stability and consolidation of the bearing cage, the smoothness of the cage rail surface, the centrifugal and gyroscopic forces received by the tumbling body, and other constraints speed elements.
Laboratory tests and practical application experience indicate that the bearing should have the highest working speed that cannot be exceeded, which is due to technical thinking; otherwise, it is necessary to keep the working temperature at an acceptable level; the cost of the touch is very high. high.
Please refer to the bearing table for the constrained speed value; it is based on the various requirements for high-speed operation. The bearing and cage depictions shown in this catalogue have been considered.
Bearings are capable of operating at speeds higher than those listed in the table; however, it is necessary to think about the accuracy of the work; and the problems of cage depiction, smoothness and heat dissipation.
Special circumstances are in some applications; there are more important factors that are more important than the limit speed.
Low speed at very low speeds; elastic fluid dynamic smooth film can not be formed on the touch surface of the roll and raceway. In these applications; smoothing agents including EP additives should generally be used.
The reciprocating sway is in this working state; the direction of rotation is changed when the bearing is not fully rotated. Since the rotation speed is zero when the rotation direction is just turned; therefore, the smooth fluid is completely fluid and the smooth film cannot be maintained. In the case; in order to obtain a smooth oil film that can accept the load; it is very important to use a smoothing agent rich in EP additives.
It is not possible to set a limit speed or extra speed for this reciprocating sway; since its upper speed limit is not subject to heat balance; it is determined by the relevant inertial force. In each direction, there is a The risk is presented; that is, the inertial force causes the rolling element to slide at a small interval; and the raceway is dirty. The allowable acceleration and deceleration depend on the shape of the roll and cage, the variety and dosage of the smoothing agent, and the working clearance. And the bearing load. For example; in the connecting rod bearing equipment; the use of the relatively small, lightweight preload bearing of the rolling element. Can not supply the usual strategy; but to align the situation; to make a more accurate motion analysis .
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