Production characteristics of rolling bearing parts

Compared with general mechanical parts, the bearing parts are short and thin rotating surface bodies. The rotating body determines that the processing machine is relatively simple, most of them are lathes and grinding machines; short and thin determines the axial rigidity, axial deformation can be Neglected, the radial stiffness is poor, and the tightening method during processing should have special considerations.

Although the rolling bearing parts have a simple structure but high technical requirements, they have the following processing characteristics:

Precision machining

Most of the surface of the bearing parts is ground. The grinding dimensions and geometrical accuracy are in μm. In particular, the raceways and rolling elements of the ferrule are more precise and require super finishing or grinding.

2. Multi-process processing

The requirements for parts are high and the production process is inevitable. General bearing production requires 20 to 40 processes, and more than 70.

3. Forming processing

The working surface of the bearing parts is a rotary forming surface, which is suitable for processing by molding. For example, the forging and rolling of the ferrule raceway are processed by forming tools or anti-profile plates.

In addition, most of the bearings are standardized products. The bearings of the same type require a large amount. In order to improve productivity, reduce costs, ensure quality, and widely adopt new technologies and improve mechanization and automation, bearing companies generally follow bearing models and varieties. For mass production, even special automated lines or lines can be built for production.

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Detailed description of the bearing roller processing

1. Process history of cylindrical roller bearings

Blank forming→deburring or ring belt→soft grinding raceway surface→soft grinding double end face→heat solution→pre-grinding rolling surface→rough grinding double end face→fin rough grinding rolling surface→finishing grinding double end face→fine and final grinding rolling surface→ Super-finishing rolling surface → cleaning, boring → final inspection appearance, size grouping → oiling packaging.

2. Process history of tapered roller bearings

Blank forming → deburring or ring belt → soft grinding raceway surface → soft grinding double end face → heat solution → coarse grinding rolling surface → fine grinding rolling surface → grinding ball base surface → final grinding rolling surface → super finishing rolling surface → cleaning, boring → Final inspection appearance, size grouping → oiling packaging.

The above two types of rollers can be made into a convex shape busbar rolling surface. If the convexity measure is less than 0.005 mm, the individual can be indirectly performed in the superfinishing rolling surface process; if the convexity measure is larger than 0.005 mm, the individual can be rolled in the last final grinding. The surface process grinds the crown and then performs super finishing.

3. The process of needle roller

Blank forming → deburring → heat solving → coarse, fine, final grinding rolling surface → super finishing rolling surface or sawdust polishing.

For the flat head and the cone needle roller, if the blank forming is difficult to guarantee the length dimension tolerance, the grinding double end process can be added in the grinding and rolling. If a convex shaped busbar rolling surface is required, it can be carried out indirectly in the superfinishing rolling surface or the calendering process.

4. Process history of asymmetric spherical roller

Blank forming → deburring or ring belt → soft grinding raceway surface → soft grinding double end face → heat solution → grinding aspheric end face → grinding ball end face → coarse, fine, final grinding rolling surface → polishing → cleaning, boring → final inspection appearance, size Group → oiled packaging.

The process of symmetrical spherical roller is:

Blank forming→deburring or ring belt→soft grinding raceway surface→soft grinding double end face→heat solution→rough grinding rolling surface→coarse, final grinding double end face→fine, final grinding rolling surface→polishing→cleaning, boring→final inspection appearance, Dimensions grouped → oiled packaging.

If the final rolling surface process can reach the surface roughness request, polishing may not be performed.

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Transmission one-axis rear bearing damage inspection and troubleshooting

A CA6440 light passenger car, after driving for 40,000 kilometers, continuously showed the damage of the first axle rear bearing (50306#) of the transmission. In the process of sweeping this fault, several times the dismantling of the transmission, no abnormalities were found; the torsion bar spring adjustment screw was measured, the height was 42mm, and the rule of the rule was met; check the position of the spline groove between the torsion bar spring and the fixed arms at both ends. - All the two levers were crashed and checked, and no problems were found. Only the rubber pad between the torsion bar spring adjustment screw and the rear fixed arm on the left side is damaged. After changing the rubber pad, the problem is removed. It has been driving more than 5,000 kilometers so far, and the bearing work is still normal.

The CA6440 light passenger car, the front suspension uses a vertical torsion bar spring independent suspension, connected to the frame and steering knuckle through the connecting rod. The torsion bar spring is connected to the lower control arm through the twisting arm, and the lower control arm is connected with the frame through the front beam to form the front support. The torsion bar spring is connected to the transmission support beam via a fixed arm and an adjusting screw, and the transmission support beam is connected with the frame to form a rear support. The force and moment in all directions are transmitted by the connecting rod system, and the torsion bar spring receives the changing torque. During the driving process, when the front wheel encounters the impact force in the direction direction, the front wheel and the steering knuckle are transmitted to the transmission support beam and the frame through the torsion bar spring; when the front wheel encounters the impact force in the vertical direction, the front suspension The frame is transformed by the torsion bar spring into a changing torque that is transmitted to the transmission support beam and the frame. The energy of various impact forces and moments on the front wheels is gradually absorbed by the tires, shock absorbers, steering knuckles, tie rod springs, transmission beams and frame parts to ensure the smoothness and safety of the car. In order to make the front wheels on both sides encounter the forces and moments in all directions, it can be effectively absorbed and consumed. When the torsion bar spring is installed, a certain pre-torque force should be added. This pre-torque is equivalent to a large spring that cooperates with the damper to provide vibration damping while also effectively absorbing the energy generated by forces and moments from all directions of the front wheels. In order to make the two spring torsion bars have the same pre-torque force, the device and adjustment of the torsion bar spring must be strictly operated in accordance with the technical specifications, so as to ensure that the two front wheels reach equilibrium during the transmission force and torque and energy absorption.

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Cylinder bearing housing hole inspection and bearing matching

Bearings (tiles) must be replaced during engine overhaul. Replacing the bearing includes two stages: optional bearing and machined bearing.

1. Inspection of crankshaft bearing housing bore and matching of bearings

1. Before the bearing is matched, first check whether the bearing housing hole meets the standard. Clean the housing and cover, crankshaft and crankcase. Check whether the end face of the bearing cap is flat, and the flatness and the maximum depth of the bore should conform to the specified data.

2. As needed, place a number of gaskets (copper or steel) on both ends of the bearing cap to make the bearing seat hole cushion to a perfect circle, install the bearing cap, tighten the bolt, and measure the inner diameter of the bearing housing bore with the inner diameter gauge. And its roundness and cylindricity error. If the roundness and cylindricity error exceeds 0.05mm, the boring should be repaired according to the specified size.

3. Select the bearing according to the repair size of the crankshaft journal. The bearing thickness and its uniformity are measured by a special centimeter card. The outer diameter of the bearing should be adapted to the size of the bearing housing hole, and the thickness deviation should not exceed 0.03 mm. Tap the bearing with a metal object, such as a crisp sound, indicating that the alloy is well bonded to the bottom plate.

4. Insert the appropriate bearing into the bearing seat and cover to check whether the bearing is in close contact with the bearing seat (the degree of fit between the back of the bearing and the seat hole is not less than 85% of the contact area), whether the notch and the bearing seat are The groove of the cover is fitted, and the oil hole on the bearing is in communication with the oil passage on the seat.

5. After the bearing is in close contact with the seat hole, the edge of the two ends must be higher than the plane of the bearing seat by 0.04 to 0.06 mm, so that the fitting can be better sealed. The test method is as follows: the bearing and the bearing cover are installed, and the bolt is properly tightened until the bearing is in close contact with the base. The thickness gauge is inserted into the plane of the bearing cover, and the gap between the bearing cover and the contact surface of the cylinder seat hole is measured to 0.10. The mm thick gauge insert feels fit, and a 0.15mm thick gauge cannot be inserted as appropriate. If the clearance is too large, both ends of the bearing should be trimmed; if it is too small, a separate bearing is required.

6, the bearing matching requirements can be summarized in four sentences, namely: according to the journal selection of bearings; bearing length standards; good smooth back convex; elastic suitable without dumb sound.

7. The back of the bearing is generally marked with a reduced size (indicated by the “—” sign). If there is no mark or the thickness does not match, the bearing level can be checked by measuring the bearing thickness.

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How to choose bearings and precautions in use

With the progress and development of society, mechanization has been widely used in production and life. As an indispensable part of the machine, the range of use of the bearing will become wider and wider, as the bearing is used whenever there is a rotation.

Bearings mainly support and reduce friction in the machine, so the accuracy and noise of the bearings are directly related to the use and life of the machine. However, business people often encounter customers who use the best bearings or imported bearings, and the efficiency is not high, which is related to the use and selection of bearings. Some people may say that "the use and selection of bearings is the user's business, I only want what the user wants me to sell." However, as a qualified salesperson, besides mastering the knowledge of its own products, it must be proficient in the use of products, that is, doctor-type sales, and select the best matching bearings according to the performance and use conditions of the user's accessory products. This is the popular professional manufacturing and sales of major companies in the world. This method has also achieved good results since the implementation of the People's Group.

Because of the wide variety of bearing types, the following will focus on the use and selection of the most widely used deep groove ball bearings. Those who wish to know less about bearings can deepen their understanding of bearings.

First, the choice of bearings

1. Selection of bearing model: The bearing model is generally selected by the user's technical personnel according to the service conditions of the supporting product and the bearing load. The business personnel mainly understand whether the actual load of the user is consistent with the selected bearing. If the bearing does not meet the requirements for use, the customer should be advised to re-select the model as soon as possible, but unless the special product is selected on the model, there will be no problem.

2, the choice of bearing clearance: users generally only know what type and grade when buying bearings, rarely ask for the clearance of the bearing, the business personnel must ask about the conditions of use of the bearing, the speed and temperature of the bearing The tolerances are directly related to the choice of bearing clearance. Motors with a speed of 3,500 rpm or less generally use CM clearance. For example, high-temperature high-speed motors require relatively large clearance. After the assembly, the bearing clearance will be reduced due to the increase of the inner hole and the reduction of the outer circle. The reduction of the clearance = the interference amount × 60% (except for the bearing chamber is aluminum). For example, the clearance before the assembly of the bearing is 0.01 mm, and the interference at the time of assembly is 0.01 mm, and the clearance after the assembly of the bearing is 0.004 mm. In theory, the noise and life of the bearing are at the best state when the bearing is at zero clearance, but in the actual operation, considering the temperature rise and other problems, the clearance of the bearing after assembly is preferably 0.002mm-0.004mm.

3, the choice of grease: the choice of grease is generally based on the bearing speed, temperature resistance, noise requirements and starting torque, etc., requiring business personnel to understand the performance of various greases.

4, the choice of bearing seal type: bearing lubrication can be divided into oil lubrication and grease lubrication. Oil-lubricated bearings are generally selected form bearings, and grease-lubricated bearings are generally sealed with dust caps or rubber seals. The dust cover is suitable for high temperature or good environment. The seal is divided into contact seal and non-contact seal. The contact seal has good dustproof performance but large starting torque. The non-connected seal has small starting torque but sealing performance. No contact is good.

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6 features of sliding bearing damage

As the world's top bearing imported bearings, such as SKF, NSK and other bearing applications are very extensive. In every industry, the characteristics of its damage are also different. Today we look at the damage characteristics of the engine sliding bearing.

(1) Mechanical damage

The mechanical damage of the sliding bearing means that the alloy surface of the bearing bush has different degrees of groove marks. In severe cases, metal peeling occurs on the contact surface and a large area of ​​random scratches occurs; in general, the contact surface damage and ablation phenomenon exist simultaneously. The main cause of mechanical damage to the bearing is that it is difficult to form an oil film on the bearing surface or the oil film is seriously damaged.

(2), bearing cave erosion

Under the repeated action of the sliding bearing in the cylinder pressure impact load, the surface layer is plastically deformed and hardened by hardening, and the local deformation loss ability is gradually formed, and the grain is gradually formed and expanded continuously. Then, as the wear debris falls off, a hole is formed in the loaded surface layer. . Generally, when cavitation occurs in the bearing bush, the pit first appears, and then the pit gradually expands and causes cracking at the interface of the alloy layer, and the crack spreads in the parallel direction of the interface until peeling off. The main reason for the cavitation of the sliding bearing is that the oil flow is strongly disturbed due to the sudden change of the cross section of the structural elements such as the oil groove and the oil hole, and bubbles are formed in the vacuum region where the oil flow is disordered, and then the bubble collapses due to the pressure rise. eclipse. Cavitation is generally found in the high load area of ​​the bearing, such as the lower bearing of the main bearing of the crankshaft.

(3), fatigue pitting

Bearing fatigue pitting refers to the overheating of the bearing and the excessive bearing clearance due to over-loading of the engine, resulting in fatigue damage, fatigue pitting or fatigue shedding in the middle of the bearing. Most of this damage is caused by overload, excessive bearing clearance, or unclean lubricating oil and foreign matter mixed in the interior. Therefore, when using, care should be taken to avoid overloading the bearing. Do not operate at too low or too high speed; adjust the engine to a steady state when idling; ensure normal bearing clearance and prevent engine speed from being too high or too low; check and adjust cooling The working condition of the system ensures that the working temperature of the engine is suitable.

(4), bearing alloy corrosion

The bearing alloy corrosion is generally the area where the lubricating oil is not pure. The chemical impurities (acid oxides, etc.) in the lubricating oil cause the bearing alloy to oxidize to form an acidic substance, causing the bearing alloy to partially fall off and form irregular micro holes or small concaves. pit. The main reason for the corrosion of the bearing alloy is improper selection of lubricating oil, poor corrosion resistance of the bearing material, or rough engine operation and high temperature.

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Comparison of fluid-lubricated bearings and oil-impregnated bearings

First, the connected porosity is about 20% (volume fraction), and the effective gas permeability is about 10 x 10-1. m. Under the condition of low pressure and high speed of oil-containing imported bearings, the leakage of lubricating oil is very small, and the oil film does not become very thin, so it is mainly controlled by fluid lubrication. Under such low pressure and high speed conditions. Oil-impregnated bearings have a slightly lower coefficient of friction than fluid-lubricated bearings and conventional bearings that are constantly supplied with oil. This is because the air in the cavity formed in the upper portion of the inner diameter of the bearing forms bubbles in the lubricating oil, thereby lowering the apparent viscosity of the lubricating oil.

However, under high pressure and low speed conditions, the phenomenon of lubricating oil leakage is serious, the oil film is thinned, and boundary lubrication and solid contact friction are added in the fluid lubrication area, so that the friction coefficient sharply rises. Figure 6. The critical point for this phenomenon. This critical point is 6. Compared with the critical point c in a conventional bearing, it is more biased toward the low pressure, high speed side. This is because, in the case of a conventional imported bearing, the leakage of the lubricating oil only occurs at both ends of the bearing, and for the oil-impregnated bearing, in addition to the both ends, the lubricating oil leaks through the pores of the porous body. Next, the connectivity  gap is about 30% (volume fraction), and the effective gas permeability is about 100×10-1. m. Oil-bearing bearing II, the connected porosity is 1.5 times that of the oil-impregnated bearing I, and the oil content is also 1.5 times. However, the leakage of lubricating oil is related to the effective gas permeability, that is, the leakage amount of the lubricating oil of the oil bearing II is an order of magnitude higher than that of the oil bearing. That is to say, for the oil-impregnated bearing II, it is more difficult to maintain the thickness and lubrication performance of the oil film, so the critical point 6 is more biased toward the low pressure and high speed side.

However, since the oil-filled bearing in the inlet bearing body of the two oil-impregnated bearings contains lubricating oil, it does not enter a state in which the oil supply is completely stopped. Therefore, even if it exceeds the I critical point of 6. With 6. , with conventional inlet bearings exceeding the critical points ct and c. In comparison, the increase in the coefficient of friction is relatively flat, and it is not prone to "burning".

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Bearing box installation and precautions

Bearing housing installation:

1, standard type

Several methods of mounting the bearing housing with snap rings and retaining plates.

Mounting the bearing with the set screw will cause the bearing casing to deform and should be avoided as much as possible.

2, flange type

When installing a flange type linear bearing, the precision of the surface of the bearing housing must be accurate.

3, adjustable type (small opening type)

The bearing is perpendicular to the opening in the bearing housing to obtain a uniform preload in the circumferential direction.

4, large opening type

If used in conjunction with a suitable housing, large-open bearings can also be adjusted for clearance, even with light preload.

5, precautions during installation

When the linear bearing is installed in the bearing housing, auxiliary work should be used to avoid direct tapping of the end face or the sealing ring. The bearing should be evenly introduced, and the buffer plate should be used to load it with a gentle tap.

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Causes and prevention methods of corrosion of imported bearings

Causes and Prevention of Corrosion of Imported Bearings Corrosion of imported bearings is caused by various internal and external factors. The main ones are:
    1, metal surface finish (oxygen concentration difference battery corrosion).
    2. The chemical composition and structure of the metal material itself.
    3. The composition of the solution and the pH value in contact with the metal surface;
    4. Ambient temperature and humidity.
    5. Various environmental media in contact with the metal surface.
    6, other people's sweat is also the cause of bearing corrosion, its pH is 5 ~ 6. Therefore, in order to prevent rust caused by hand sweat, the installation and production personnel should wear gloves, do not touch the imported bearings by hand.

Apply anti-rust oil to prevent skf bearing from rusting
1. Immersion method: Some small imported bearings are immersed in anti-rust grease. The thickness of the oil film can be achieved by controlling the temperature or viscosity of the anti-rust grease. A method of adhering a layer of rust preventive grease to the surface.
    2, brushing method: pay attention to evenly spread on the surface of the imported bearing when brushing, do not produce accumulation, but also pay attention to prevent leakage coating.
    3. Spray method: Some large-scale anti-rust materials are not suitable for oiling by immersion method. Generally, the compressed air with a pressure of about 0.7Mpa is sprayed in the air cleaning place. The spray method is suitable for solvent-diluted rust preventive oil or thin layer rust preventive oil. This method must use sound fire protection and labor protection measures.

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Causes and prevention methods of corrosion of imported bearings

Causes and Prevention of Corrosion of Imported Bearings Corrosion of imported bearings is caused by various internal and external factors. The main ones are:
    1, metal surface finish (oxygen concentration difference battery corrosion).
    2. The chemical composition and structure of the metal material itself.
    3. The composition of the solution and the pH value in contact with the metal surface;
    4. Ambient temperature and humidity.
    5. Various environmental media in contact with the metal surface.
    6, other people's sweat is also the cause of bearing corrosion, its pH is 5 ~ 6. Therefore, in order to prevent rust caused by hand sweat, the installation and production personnel should wear gloves, do not touch the imported bearings by hand.

Apply anti-rust oil to prevent skf bearing from rusting
1. Immersion method: Some small imported bearings are immersed in anti-rust grease. The thickness of the oil film can be achieved by controlling the temperature or viscosity of the anti-rust grease. A method of adhering a layer of rust preventive grease to the surface.
    2, brushing method: pay attention to evenly spread on the surface of the imported bearing when brushing, do not produce accumulation, but also pay attention to prevent leakage coating.
    3. Spray method: Some large-scale anti-rust materials are not suitable for oiling by immersion method. Generally, the compressed air with a pressure of about 0.7Mpa is sprayed in the air cleaning place. The spray method is suitable for solvent-diluted rust preventive oil or thin layer rust preventive oil. This method must use sound fire protection and labor protection measures.

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