How is the bearing vibration generated?

    In general, the rolling bearings in SKF bearings do not generate noise by themselves. The "bearing noise" that is usually felt is in fact the acoustic effect of the SKF bearing directly or indirectly vibrating with the surrounding structure.

    This is why many times noise problems can be considered as vibration problems involving the entire bearing application. Excitation due to the change in the number of rolling elements. When a radial load is applied to a bearing, the number of rolling elements carrying the load will change slightly during operation, ie: 2-3-2-3... This causes a shift in the load direction. The resulting vibration is unavoidable, but can be mitigated by axial preloading and applied to all rolling elements (not suitable for cylindrical roller bearings in SKF bearings).

    When the waviness of the component is closely matched between the bearing ring and the bearing housing or the transmission shaft, the bearing ring may be deformed in cooperation with the shape of the adjacent component. If deformation occurs, vibration may occur during operation. Therefore, it is important to machine the housing and drive shaft to the required tolerances.

    Local damage A small number of bearing raceways and rolling elements may be damaged due to handling or installation errors. In operation, rolling a damaged bearing component produces a specific vibration frequency. Vibration frequency analysis identifies damaged bearing components. Vibration behavior in applications In many applications, the stiffness of the bearing is the same as the stiffness of the surrounding structure. Due to this feature, it is possible to reduce the vibration in the application as long as the bearings (including preload and clearance) are properly selected and their configuration in the application.

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Rolling bearing accuracy and grade

The accuracy of the rolling bearing is divided into (main) dimensional accuracy and rotation accuracy. The accuracy level has been standardized and is divided into five levels: P0, P6, P5, P4, and P2.
      The accuracy is increased from the 0th level in order, and is sufficient for the general purpose 0 level, but when used in the conditions or occasions shown in Table 1, an accuracy of 5 steps or higher is required.
      Although the above accuracy level is based on the ISO standard, its name is different in national standards.
      Table 2 lists the accuracy levels applicable to the various bearing types and the comparison between national standards.

      Dimensional accuracy (items related to shaft and housing installation)
      1. Allowable deviation of inner diameter, outer diameter, width and assembly width
      2. Allowable deviation of the diameter of the compound circle and the diameter of the outer complex circle in the roller group
      3, the allowable limit value of the chamfer size
      4, the allowable variation of the width

      Rotation accuracy (items related to the rotation of the rotating body)
      1. Allowable radial runout and axial runout of the inner and outer rings
      2, the inner ring allows lateral runout
      3. Allowable variation of the inclination of the outer diameter surface
      4. Allowable variation of the thickness of the thrust bearing raceway
      5. Allowable deviation and allowable variation of tapered bore

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Selection of sliding bearing grease

Core Tips: 1. Sliding bearings can also be lubricated with grease. The following points should be considered when selecting grease: 1) When the bearing load is large and the speed is low, the grease with a small cone penetration should be selected.
1. Sliding bearings can also be lubricated with grease. The following points should be considered when selecting grease:
1) When the bearing load is large and the speed is low, the grease with a small penetration degree should be selected, and vice versa. High-speed bearings use grease with a small degree of penetration and good mechanical stability. Special attention is paid to the lower viscosity of the base oil of the grease.
2) The dropping point of the selected grease is generally higher than the working temperature of 20-30 ° C. In the case of continuous operation at high temperature, be careful not to exceed the allowable operating temperature range of the grease.
3) When the sliding bearing works in water or humid environment, it should choose calcium-based, aluminum-based or lithium-based grease with good water resistance.
4) Select a grease with good adhesion.
2. Selection of grease for sliding bearings:
The load is <1MPa, the circumferential speed of the journal is less than 1m/s, the maximum working temperature is 75°C, and the calcium base grease No. 3 is used;
The load is 1-6.5MPa, the circumferential speed of the journal is 0.5-5m/s, the maximum working temperature is 55°C, and the calcium base grease No. 2 is used;
The load is >6.5MPa, the circumferential speed of the journal is less than 0.5m/s, the maximum working temperature is 75°C, and the calcium base grease No. 3 is used;
The load is <6.5MPa, the circumferential speed of the journal is 0.5-5m/s, the maximum working temperature is 120°C, and the No. 2 lithium grease is used;
The load is >6.5MPa, the circumferential speed of the journal is less than 0.5m/s, the maximum working temperature is 110°C, and the calcium-sodium grease of No. 2 is used;
The load is 1-6.5MPa, the circumferential speed of the journal is less than 1m/s, the maximum working temperature is 50-100°C, and the No. 2 lithium grease is used.
Load >5MPa The circumferential speed of the journal is 0.5m/s, the maximum working temperature is 60°C, and the No. 2 calendering grease is used;
Calcium-sodium based grease should be considered in a humid environment at temperatures between 75 and 120 °C. In a humid environment, the working temperature is below 75 ° C, there is no calcium base grease No. 3, and aluminum base grease can also be used. When the working temperature is 110-120 ° C, lithium base grease or sulfhydryl base grease can be used. When concentrated lubrication, the consistency is smaller.
3. Lubrication cycle of grease for sliding bearings:
Accidental work, unimportant parts: shaft speed <200r/min, lubrication cycle 5 days; shaft speed >200r/min, lubrication cycle 3 days.
Intermittent operation: shaft speed <200r/min, lubrication cycle once every 2 days; shaft speed>200r/min, lubrication cycle once every day.
Continuous operation, working temperature is less than 40 °C: shaft speed <200r/min, lubrication cycle once every day; shaft speed>200r/min, lubrication cycle once per shift.
Continuous operation, working temperature 40-100 °C: shaft speed <200r/min, lubrication cycle once per shift; shaft speed >200r/min, lubrication cycle twice per shift.

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Principle of self-lubricating bearings

Core Tip: At present, most of the bearings used in various machinery industries are still balls, needles and the like. Only a small part of the bearings have been self-lubricating bearings. It is believed that in the near future, the bearings will be adapted from the lubrication.
At present, most of the bearings used in various machinery industries are balls, needles and the like. Only a small part of them have adopted self-lubricating bearings. It is believed that in the near future, lubricating bearings will be incomprehensible, wear-resistant and economical. Advantages and become the leading product in the bearing industry. The following are the application characteristics and advantages of some self-lubricating bearings: oil-free lubrication bearing series
1. No oil lubrication or less oil lubrication. It is suitable for places that cannot be refueled or difficult to refuel. It can be used without maintenance or less maintenance.
2. Good wear resistance, small friction coefficient and long service life. 3. There is an appropriate amount of elastoplasticity, which can distribute the stress on the wider contact surface and improve the bearing capacity of the bearing.
4. The static friction coefficient is similar, which can eliminate the creep at low speed, thus ensuring the working precision of the machine.
5. It can reduce vibration, reduce noise, prevent pollution and improve working conditions.
6. The transfer film can be formed during the operation to protect the grinding shaft without biting.
7. The hardness requirement of the grinding shaft is low, and the shaft without the quenching and tempering can be used, thereby reducing the processing difficulty of the related parts.
8, thin wall structure, light weight, can reduce the mechanical volume.
9, the back of the steel can be electroplated with a variety of metals, can be used in corrosive media; has been widely used in various mechanical sliding parts, such as: printing presses, textile machines, tobacco machinery, micro-motors, automobiles, motorcycles and agricultural and forestry machinery and many more.
Introduction to boundary lubrication self-lubricating bearing series
1. Good load bearing and good wear resistance.
2. It is suitable for rotary motion, rocking motion under high load and low speed, and occasions that often open and close under load and are not easy to form hydrodynamic lubrication.
3. Under the condition of boundary lubrication, it can be maintained for a long time without oiling, and the oil is added in the overlayer to make the bearing last longer.
4. The surface plastic layer can leave a certain margin during processing and molding. After the assembly is pressed into the seat hole, it can be processed by itself to achieve a better assembly size.
5. The products are mainly used in automobile chassis, metallurgical machinery, mining machinery, hydraulic machinery, construction machinery, agricultural machinery, steel rolling equipment, etc. JDB solid inlaid bearing series JDB solid inlaid bearing series is a general-purpose basic product, which can adapt to high pressure, low pressure, high temperature, low temperature, oil lubrication, oil-free lubrication or water lubrication. The base of the product is high-strength brass, which doubles the hardness of the ordinary copper sleeve and more than doubles the wear resistance. Widely used in: light industrial machinery, heavy machinery, construction machinery, metallurgical machinery, conveying machinery, etc., such as: continuous casting machine, rolling mill, injection molding machine, paper machine, mold guide column, ship, machine tool and so on.

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