In the transmission, the role of rolling needle bearing is to support the swimming gear on the axis. Among them, the outer diameter of the shaft is equivalent to the inner rolling road of the rolling needle bearings. The inner hole of the gear is equivalent to the outer lane of the roller bearings. Essence
Micro -motion wear is one of the main forms of rolling needle bearings. Generally, the hardness of the rolling needle is slightly higher than the hardness of the inner ring and the inner hole of the gear. Or the outer circle of the shaft.
1. The mechanism of rolling needle bearing micro -dynamic wear
The swim gear in the transmission is usually a diagonal gear. During the turning operation, the force analysis is shown in Figure 3. Among them, the mana direction FN is the comprehensive force of the gear; the cut force FT transmits the torque of the gear; the radial force FR uses the inner hole of the gear to apply pressure on the roller; due to the existence of the gear axial and radial gaps, axial force FN tilted the gear along the axial direction, forming a swing during operation). During the swinging process of the gear, the inner holes of the gear have a small displacement axis of a small displacement under the action of radial pressure compared to the roller. Wear.
Movement wear is a molecular wear process, that is, the two contact surface performs the reciprocating movement of micro -displacement under vertical load, so that the contact surface is enough to approach Van Delleli, which causes the material to get out of the mother and be oxidized. It can be seen that micro -dynamic wear causes material loss is the result of the common effect of chemical (oxidation) and mechanical (loading movement). The mechanical effects scrape the oxidation layer and adsorption layer, exposing a clean and lively fresh metal surface. Fresh surfaces quickly adsorb the surrounding gases and oxidize reactions, which is chemical. Mechanical and chemicals alternately cause material losses.
2. The influencing factors and prevention of micro -dynamic wear
It can be seen from the analysis of the mechanism of rolling needle bearing micro -dynamic wear. They are: radial vertical load, displacement, and cycle times of movement. From the analysis of the friction mechanism, the degree of wear is also affected by factors such as material hardness, surface roughness, and lubrication.
2.1 radial vertical load
The radial vertical load of the rolling needle bearing is mainly derived from the radial force of the gear. The greater the radial force, the greater the pressure on the contact site (less than 4000MPa), the easier it is to exacerbate the wear during relative exercise. The radial force of the gear is determined by the torque transmitted, and it is usually not changed, and the pressure of the contact site can be reduced by the optimization of the rolling needle bearing. The optional optimization scheme is: to reduce local pressure, improve wear resistance, and prevent micro -dynamic wear by increasing methods such as increasing rolling needle length, rolling needle, and diameter of rolling needle.
2.2 Differential movement of reciprocity
The displacement of the reciprocating movement is caused by the axial gap (0.15 ～ 0.45mm) and the radial gap (0.015 ～ 0.058mm) of the roller bearing. The larger the gap, the greater the displacement of the reciprocating movement, the faster the speed, the higher the friction skills, the more likely it will cause local wear. There are two optional optimization schemes: one is to reduce the axial gap (0.1 ～ 0.35mm) by improving the axial positioning accuracy of the gear and shaft; The diameter tolerance packet matching to reduce the radial gap (0.009 ～ .048mm). Through the optimization of the gap, it can significantly reduce the displacement of the reciprocating movement, reduce the frictional skills, and play a role in preventing micro -moving wear.
2.3 Cycles
In the process of rolling needle bearings, the higher the number of cycles, the more obvious the degree of motion wear. The number of cycles is determined by the mileage of the vehicle (3 × 105 km) and the speed ratio (changes with the vehicle and gear). The longer the mileage of the driving, the more the cycle is; if the swimming gear is a active wheel, the mileage is certain, the smaller the speed is, the less the number of cycles. Both parameters are determined by the OEM. The mileage represents the life of the vehicle and usually cannot be changed. Speedfield is related to the power of the vehicle and the fuel consumption. Under the premise of obtaining the consent of the OEM, it can sometimes be used as a small adjustment to appropriately reduce the risk of micro -dynamic wear.
2. 4 Material surface hardness
Under the same conditions, the higher the surface hardness of the material, the higher the ability to prevent micro -wear. Most of the rolling needles are bearing steel, and the hardness is slightly higher than the gear and shaft, so micro -moving wear usually occurs on the outer diameter of the inner hole or shaft in the gear. The hard degrees of the material of the gear and shaft are determined by the material type (20CRMNTIH, 20CRMO, 18MNCR5, etc.) and thermal treatment conditions (usually carburizing quenching). The optional optimization scheme is: appropriately reduce the ignition temperature to obtain higher surface hardness (HV700 or more) to improve wear resistance.
2. 5 surface roughness
Increasing the surface roughness level, it can reduce the frictional factor and reduce frictional skills to achieve the role of inhibiting micro -dynamic wear. The roughness of the inner and outer rollers of grinding processing can reach RA0. 4 μm, which can basically meet the requirements of the use. When other influencing factors are not ideal, micro -wear is sometimes produced. The optional optimization scheme is to add fine grinding processes to the process. Properly increase the roughness level of the inner hole and the outer diameter of the gear (RA0. 2 μm), which can effectively reduce the risk of micro -wear wear.
2. 6 Lubrication
The lubrication of the roller bearing is usually achieved through the oil hole to guide the oil into the roller. A good lubrication can ensure that the oil film is formed between the rolling needle and the roller, reducing the friction factor, reducing friction, and preventing wear. The optional optimization scheme is: first, by improving the depth and angle of the oil guide slot, the sufficient lubricating oil is guided to the axis heart. Secondly, by expanding the diameter of the oil holes on the shaft or increased the number of oil holes, the sufficient amount of oil is guided from the axis to the bearing tract. Finally, through the adjustment of additives, the pole pressure performance of lubricating oil is improved, and the pressure stability of the oil membrane is improved. From the analysis of the occurrence of micro -dynamic wear during product development, the analysis of the results, and test results, fully lubricating is one of the most effective ways to avoid micro -wear wear.
3. Analysis of other factors that exacerbate micro -motion wear
3. 1 There is no relative rotation with the inside and outside trails
The micro -moving wear marks of the rolling needle bearing is usually an aperture indentation. This is because when the transmission is rolled with the inner holes and shafts of the gear, the roller is not rotated. The outer diameter of the shaft is not relative. At this time, the relative position of the relative position of the outer diameter of the inner hole or axis of the roller and the gear is unchanged, and only the axial movement moves, so the equivalent indentation occurs. The method of keeping the opening of the roller bearings or the cutting of the rack is divided into two halves to achieve the asymmetric force and gravity, and the imbalance of the centrifugal force of the radial radial, thereby forcing the relative rotation of the outer diameter of the inner pore or shaft of the roller and the inner hole of the gear or a shaft. Axial friction at the same position for a long time to form micro -dynamic wear. This method is also one of the measures that are often used in the project to solve the micro -wear of the rolling needle bearing.
3. 2 resonance with the shaft itself
Due to the processing error and assembly error, the shaft itself will cause eccentric vibration during the work. If the frequency of this vibration is the same or close to the vibration frequency of the micro -movement process, the two are prone to resonance. Once a resonance is generated, the micro -dynamic wear of the rolling needle bearing will be significantly exacerbated. By increasing the straight -line processing accuracy and assembly of the same axis accuracy of the axis can effectively reduce the amplitude of the axis itself, thereby achieving the purpose of weakening resonance.
Micro -motion wear is one of the common faults of rolling needle bearings. By analyzing the micro -wear mechanism of rolling needle bearing, the main influencing factor of micro -dynamic wear was found. By analyzing the principle of the influencing factors of micro -dynamic wear, a number of preventive measures to avoid micro -wear wear are proposed from the design aspect. Among these preventive measures, improving the lubrication structure to achieve fully lubrication and adopt opening or section to maintain the rack to achieve the relative rotation of the rolling needle and the internal and external rolling tract is the most commonly adopted and most effective measure in the project. The micro -dynamic displacement of reducing the rolling needle bearing is a new measure proposed on the basis of studying the micro -dynamic wear mechanism, which provides new ideas for subsequent design and market problems. With the more in -depth research on the micro -dynamic wear mechanism and more engineering practices, more and better optimization measures will be discovered and proposed, and the problem of avoiding micro -wear is completely avoided.