Preloading methods are divided into two categories: radial preloading method and axial preloading method. A brief introduction is as follows:
1. Radial preloading method. The radial tightening method is mostly used in tapered bore bearings that bear radial loads. A typical example is a double row precision short cylindrical roller bearing. A nut is used to adjust the bearing relative to the tapered journal. The axial position of the inner ring allows the inner ring to have an appropriate amount of expansion to obtain radial negative clearance. This method is mostly used in machine tool spindles and jet engines.
3. Axial preloading method Axial preloading method can be roughly divided into two types: positioning preloading and constant pressure preloading.
In positioning preloading, the appropriate preloading amount can be obtained by adjusting the size of the bushing or gasket; the appropriate preloading amount can also be adjusted by measuring or controlling the starting friction torque; the preloading amount can also be directly adjusted using Pairs of double bearings are used to achieve the purpose of preloading. At this time, the user generally does not need to adjust. In short, the relative position of any bearing that has been axially preloaded will definitely not change during use.
Constant pressure preloading is a method of using coil springs, disc springs, etc. to ensure that bearings are properly preloaded. The rigidity of the preload spring is generally much smaller than the rigidity of the bearing, so the relative position of the constant pressure preloaded bearing will change during use, but the preload amount will remain roughly unchanged.
The comparison between positioning preload and constant pressure preload is as follows:
(1) When the preload amounts are equal, positioning preload has a greater effect on increasing the bearing rigidity, and the impact of rigidity changes on the bearing load during positioning preload is much smaller.
(2) During use of positioning preload, the axial length difference caused by the temperature difference between the shaft and the bearing seat, the radial expansion caused by the temperature difference between the inner and outer rings, and the displacement caused by the load will cause the preload to The amount changes; while the constant pressure preload is in use, the change in preload can be ignored.
Bearing torque, load and life
1. Starting torque startingtorque is the torque required to cause a bearing ring or washer to start rotating relative to another fixed ring or washer.
2. Rotational torque runningtorque When one bearing ring or washer rotates, the torque required to prevent the movement of another ring or washer.
3. Radial load radial load acts on the load perpendicular to the axis of the bearing.
4. Axial load Axial load acts on the load in the direction parallel to the axis of the bearing.
5. Static load static load is the load acting on the bearing when the relative rotation speed of the bearing ring or washer is zero (radial or thrust bearing) or when the rolling elements have no movement in the rolling direction (linear bearing).
6. Dynamic load dynamic load is the load acting on the bearing when the bearing rings or washers rotate relative to each other (radial or thrust bearings) or when the rolling elements move in the rolling direction (linear bearings).
7. Equivalent load is a general term used to calculate the theoretical load. In a specific situation, the bearing acts as if it bears the actual load under the theoretical load.
8. Basic static radial (axial) loadrating is the radial static load (center axial static load) corresponding to the total permanent deformation of the rolling elements and raceways. If under zero load, the roller and the raceway (roller bearing) are or are assumed to be normal busbars (full line contact), under the maximum contact stress, the total permanent deformation produced at the contact point between the rolling element and the raceway is the rolling element 0.0001 times the diameter. For single row angular contact bearings, the radial load rating is the radial component of the load that causes pure radial displacement of the bearing rings relative to each other.
9. Basic dynamic radial (axial) load rating is a constant radial load (constant central axial load). Under this load, the rolling bearing can theoretically withstand a basic rated life of 1 million revolutions. For single row angular contact bearings, the radial load rating is the component of the load that causes pure radial displacement of the bearing rings relative to each other.
10. Life (referring to a set of bearings) life refers to the number of revolutions of a ring or a washer relative to another ring or a washer before the material of a bearing ring or a washer or a rolling element first exhibits fatigue expansion. Life can also be expressed in hours of operation at a given constant speed.
11. Reliability (referring to bearing life) reliability refers to the percentage of bearings that are expected to reach or exceed a certain specified life of a group of nearly identical rolling bearings operating under the same conditions. The reliability of a set of bearings is the probability that the bearings will meet or exceed the specified life.
12. Rating life rating life is the predicted value of life based on the basic radial dynamic load rating or the basic axial dynamic load rating.
13.Basic rating life basic rating life is the rating life associated with 90% reliability.
14. Life factor lifefactor is a correction factor applicable to the equivalent dynamic load in order to obtain the basic rated radial dynamic load or the basic rated axial dynamic load corresponding to the given rated life.
15. Plummerblock bearing is an assembly that combines the radial bearing and the seat. There is a bottom plate for mounting screws on the support surface parallel to the axis of the bearing.
16. Vertical plummer block housing is used for mounting rolling bearings.
17. Flangedhousing is a seat that has a radial flange and a screw hole for its installation on the support surface perpendicular to the axis of the bearing.
18. The adapter sleeve has an axially opening sleeve with a cylindrical inner hole. Its outer surface is conical and the small end has an external thread. For mounting bearings with tapered bores (using lock nuts and lock washers) on shafts with cylindrical outer surfaces.
19. The withdrawal sleeve has a cylindrical inner hole with an axial opening. Its outer surface is conical and the big end has external threads. Used to install or disassemble bearings with tapered bores on shafts with cylindrical outer surfaces (using nuts).
20. Locknut The locknut is a screw nut with a cylindrical outer surface and an axial groove. Use an outer claw of the lock washer and an annular wrench to lock the nut. Used for axial positioning of rolling bearings.
21. Lockwasher A lockwasher is a thin steel plate washer with many outer claws. An outer claw is used to lock the nut, and an inner claw is inserted into the axial groove of the adapter sleeve or shaft.
22. One end of the eccentric locking collar has a grooved steel ring that is eccentric with respect to the inner hole, and is installed at the equally eccentric extended end of the inner ring of the outer spherical bearing. Rotate the eccentric sleeve relative to the inner ring to tighten the inner ring, and then tighten the jackscrew to tighten it on the shaft.
23. The concentric locking collar is a steel ring installed on the wide inner ring of an outer spherical bearing. The top screw is screwed into the hole in the inner ring and contacts the shaft.
You can judge the abnormal noise fault of power and transmission system by yourself
The sound produced by the vibration of various systems when the car is working is collectively called the sound of the car, and is also called noise in some books. These sounds can be divided into normal sounds and abnormal sounds. Many car faults are manifested through abnormal noises. Abnormal noises are phenomena, while faults are the essence. If the fault is not eliminated in time, it can easily cause a major mechanical accident. Common abnormal noises in automobiles can be mainly divided into several categories: abnormal noises from the powertrain, abnormal noises from the transmission system, abnormal noises from the driving system, and abnormal noises from the wind resistance.
Abnormal noise from powertrain
The fault mainly occurs in the engine and its related components. The abnormal noise changes with the engine speed and the frequency is relatively high.
1. Engine cylinder failure and misfire. This kind of abnormal sound is easier to identify. The abnormal sound is accompanied by strong engine vibration, and the sound frequency is the same as the vibration frequency. If you encounter this situation, don't panic. Find a nearby service station to check the engine's fuel supply, ignition, air supply, and engine computer to troubleshoot.
2. The working efficiency of the engine lubrication system decreases, causing excessive friction of the machine parts. Perhaps the engine lubricating oil has deteriorated and failed due to long-term failure to perform oil changes and maintenance, or the engine oil pressure has been insufficient due to reduced sealing of the lubrication system. This will reduce the engine lubrication effect, leading to excessive damage to the friction parts and abnormal noise. The vibration frequency of this mechanical abnormal sound is directly related to the engine speed (excitation frequency). The normal operating speed of the engine is 800-5000r/min. The frequency of the noise is very high, and the human ear can only hear continuous or short-term sounds. As the engine speed increases, the abnormal sound increases in volume and frequency. If your car has the above-mentioned abnormality, you should be mentally prepared. At the very least, disassemble the engine and perform maintenance to check the wear and tear.
3. Belts and bearings wear and produce abnormal noise. Family cars usually use a belt drive to transmit the engine's power to the generator, air conditioning compressor, power steering pump, water pump and other components. However, quality problems or poor working environment may cause belt slippage due to early wear. The same problem often occurs in air conditioning bearings, water pump bearings, generator bearings and other bearings. This kind of abnormal noise is often harsh, loud and obvious. The judgment method is relatively simple. Use a wooden stick (or metal rod, long-handled screwdriver, etc.) against a certain part of the car. The sound will change significantly when it is close to the source of the abnormal noise. This fault can be eliminated by replacing excessively worn parts.
Abnormal noise in the drive train
Abnormal noises in the transmission system often originate from components such as gearboxes, differentials, clutches, etc. Abnormal noises change significantly with changes in gear position and clutch status.
There are many parts in the transmission and clutch, and the causes of the noise are also complex. When analyzing and judging, you should pay attention to whether it is related to specific situations. Some planetary gears make obvious noise when the vehicle speed is about 60Km/h. Abnormalities in the shift cable and shift fork may cause abnormal noises when certain gears are engaged. The wear of the clutch release bearing causes noise when cutting the clutch.
There was such a car that was repairing an accident. It felt strong vibrations when traveling at 110Km/h. After repeated test runs, it was found that there was noise at the engine speed of 3000r/min, but as the gears were lowered, the noise and vibration decreased, and the noise in the second gear and below was normal. Disassemble and repair the gearbox assembly and troubleshoot. This is a fault that is obviously caused by improper matching of the gearbox and the engine. The abnormal noise and vibration are obviously different with the change of gear. Clutch failure has similar performance to gearbox failure, and abnormal noise changes with the separation and coupling state of the clutch. As long as they understand the basic principles, even non-professionals can make simple judgments on abnormal noise in the drive train.
Abnormal noise in driving system
Abnormal noises in the driving system are directly related to the vehicle's driving status (vehicle speed, steering).
Failures in the driving system are often concentrated in components such as wheel bearings, inner and outer ball cages, tie rod heads, and control arms. Early wear of wheel bearings will cause harsh noises, with obvious characteristics: as the vehicle speed increases, the frequency of abnormal noises increases; it has nothing to do with engine speed, gearbox gear, and clutch status. Abnormal noises from the ball cage and control arms are more obvious when the vehicle is turning. If the sound source is difficult to find, you can use the above characteristics to determine the abnormal sound. Having a general understanding of the fault before carrying out repairs will be of great help in protecting your own interests, and can reduce the probability of being scammed by an irregular repair shop.
Wind noise
When the vehicle speed reaches a fixed value, the abnormal noise is obvious, and when the speed decreases, the abnormal noise disappears. What is mentioned here is the abnormal noise caused by abnormal wind resistance. This type of abnormal noise is caused by pressure changes caused by the separation of airflow around the vehicle body. Specifically, it includes cavity resonance, duct pipe noise, and vibration of accessories such as antennas, wipers, rearview mirrors, and spoilers. Opening of sealing strips and rupture of plastic parts will cause changes in the external curve of the car body, causing air turbulence and abnormal noise when driving at high speeds.
