Ten misunderstandings in vehicle maintenance. Bearings for plain bearings must be scraped.

In recent years, there have been more and more car owners, and cars need regular maintenance. However, some limited-qualified repair centers often go into maintenance misunderstandings and affect the performance of vehicles. There are mainly 10 kinds of performances:

1. The bearing bush of the sliding bearing must be scraped. Modern cars, especially small engines, have thin wear-resistant alloy coatings on the crankshaft bearings and the connecting rod bearings. They are not allowed to be scraped and can only be selected according to the corresponding size. If there is no suitable size of the curved bearing, the crankshaft can be ground by the method of the base hole if necessary to obtain a suitable fit clearance.

2, the engine water temperature is not afraid of high. In fact, the low temperature of modern automobile engines is very harmful, which will cause insufficient combustion of the mixture, lower power, increased fuel consumption, and poor lubrication, which will cause excessive emissions.

3, the valve clearance is larger than the small point. In fact, the valve clearance is large, the valve lift filial degree is not enough, so that the intake air is insufficient or the exhaust is not smooth, which just reduces the engine power.

4. The more oil you add, the better. In fact, the addition of oil has caused damage to the engine, especially the inclined engine and the V-type engine. It increases the rotational resistance of the crankshaft and the connecting rod, and increases the amount of oil splashed onto the cylinder wall, resulting in an increase in carbon deposits in the combustion chamber. Therefore, if the engine oil is increased, it will reduce the engine power, increase the wear and tear, and cause the emission to exceed the standard.

5. Empty hub lubrication is not reliable. It is considered that the hub is filled with grease to ensure the lubrication of the hub bearing. The lubrication of the hollow hub coated with grease only on the bearing is not guaranteed, and the gap in the middle of the hub must be filled with grease. In fact, this not only wastes grease, but also affects the heat dissipation of the bearing, which is harmful to the lubrication of the bearing.

6, the brakes are good or bad, dragging the cherry blossoms and dragging the brakes to indicate that the wheels are already locked, and the modern cars just require the wheels to be locked, for which special anti-lock devices are installed. Once the wheel is locked, the car's steering is out of order, the wheel slips, and it is prone to failure, so the longer the trailer is, the better.

7. The gap between the breaker contacts is small. In fact, the contact gap is too large, the contact closing time is short, so that the primary side current of the ignition coil is reduced, causing the high-pressure spark to be weak, thereby causing the engine to be difficult to start.

8. Ignition advance angle or injection advance angle Ningda Do not ignite the ignition advance angle too large, easy to detonate. The engine produces a deflagration, which is extremely damaging to the piston, seriously affecting its service life, and the starting resistance of the engine is increased.

9. Fasten the bolts and keep them loose. In fact, the bolts of various parts of the car have corresponding values ​​according to the diameter, pitch and use. It is not good to loosen the bolts that do not reach the specified value, but blindly increasing the tightening torque will deform the fastened parts and cause the screw to elongate, the thread to deform or even break.

10, car maintenance, open the inspection before you rest assured. With the improvement of the manufacturing level, the life of modern auto parts has been greatly extended, and random dismantling will inevitably destroy the already mated state. In today's perfect vehicle failure detection technology, if there is no obvious fault in the component or assembly, it is generally not necessary to dismantle it.
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Hot Compression Recrystallization Behavior of Low Carbon CrNiMo Carburized Bearing Steel

Carburized bearing steel is a high quality low carbon or medium carbon alloy steel. After carburizing, the surface has high hardness, wear resistance and high fatigue strength and dimensional stability. At the same time, the core of the bearing material also requires high toughness and certain resistance. Thermal performance for the manufacture of bearings bearing large impact loads, such as rolling mills, heavy vehicles, and locomotive bearings. The author uses low carbon CrNiMo carburized bearing steel as test material, analyzes the nucleation, size and growth state of the crystal during hot compression, derives the deformation activation energy, and establishes the flow stress constitutive equation and thermal processing diagram. The critical static recrystallization time of the compression sample was tested to provide theoretical basis and experimental basis for the hot forming of low carbon CrNiMo carburized bearing steel.

In order to explore the hot compression recrystallization behavior of low carbon CrNiMo carburized bearing steel, the scholars of Kunming University of Science and Technology used the Gleeble 1500D thermal simulator to test the isothermal thermal compression test of the test steel. The deformation temperature was 900~1050 °C and the deformation rate was 0.1, 1, 10s-1, the deformation amount is 10%, 30%, 50%. The dynamic re-crystallization process of material thermal deformation was analyzed by the true stress-true strain curve and grain size change under different deformation conditions. The deformation activation energy and flow stress constitutive equation of the material were linearly regressed, and the material heat was drawn. The process map was processed and the critical time of hot pressing static recrystallization was tested. The results show that high deformation temperature, low strain rate and large deformation are beneficial to the dynamic recrystallization of the material. The test steel is finely recrystallized at a temperature of 1050 ° C, a deformation of 50% and a deformation rate of 1 s-1. The average grain size of the grain is 14.97μm; the deformation activation energy of the low carbon CrNiMo carburized bearing steel is slower than 30%, and the activation energy of 50% deformation is 436.016kJ/mol. The hot working process diagram and test results Consistent; 900 ° C, 1 s-1, 50% deformation, the material reached the dynamic recrystallization thermodynamic conditions, thermal recrystallization, static recrystallization time 5min.
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Deep groove ball bearing specification sheet

(1) New domestic model: 16001; domestic old model: 7000101; bearing type: 1600-1ZZ; inner diameter (mm): 12;

Outer diameter (mm): 28; width (mm): 7; Cr (kN): 5.1; Cor (kN): 2.4; weight (kg): 0.024;

(2) New domestic model: 16002; domestic old model: 7000102; bearing type: 1602-ZZ; inner diameter (mm): 15;

Outer diameter (mm): 32; width (mm): 8; Cr (kN): 5.6; Cor (kN): 2.8; weight (kg): 0.025;

(3) New domestic model: 16003; domestic old model: 7000103; bearing type: 1603-ZZ; inner diameter (mm): 17;

Outer diameter (mm): 35; width (mm): 8; Cr (kN): 6; Cor (kN): 3.3; weight (kg): 0.032;

(4) New domestic model: 16004; domestic old model: 7000104; bearing type: 1604-ZZ; inner diameter (mm): 20;

Outer diameter (mm): 42; width (mm): 8; Cr (kN): 7.9; Cor (kN): 4.5; weight (kg): 0.05;

(5) New domestic model: 16005; domestic old model: 7000105; bearing type: 16005-ZZ; inner diameter (mm): 25;

Outer diameter (mm): 47; width (mm): 8; Cr (kN): 8.5; Cor (kN): 5.6; weight (kg): 0.06;
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What is the tolerance of deep groove ball bearings?

What is the tolerance of deep groove ball bearings?

Bearing fit Tolerance Tolerance is the sum of the hole and shaft tolerances that make up the fit. It is the amount of variation that allows for gaps or interference. Hole and shaft tolerance band sizes and tolerance band positions make up the tolerances. The tolerance of the hole and shaft fit tolerance indicates the fit accuracy of the hole and the shaft. The size and position of the hole and shaft fit tolerance band indicate the fit and fit of the hole and the shaft. The size of the fit tolerance = the size of the tolerance band; the tolerance tolerance band size and position = fit properties.

Levels and tolerances for tolerances:

Choice of tolerance level

The tolerance level of the shaft or housing bore that mates with the bearing is related to bearing accuracy. For shafts that are matched with P0 precision bearings, the tolerance class is generally IT6, and the bearing housing hole is generally IT7. For applications where high precision of rotation and smoothness of operation (such as motors), the axis should be selected as IT5 and the bearing housing hole should be IT6.

Tolerance zone selection

The tolerance band of the shaft on which the radial and angular contact bearings are mounted is referred to the corresponding tolerance band table. For the most part, when the shaft rotates and the direction of the radial load does not change, that is, when the inner ring of the bearing rotates relative to the load direction, a transition or interference fit should generally be selected. The static axis and the radial load direction are the same, that is, when the inner ring of the bearing is stationary with respect to the load direction, a transition or a small clearance fit can be selected.

Bearing and shaft tolerance standards

1 When the inner diameter tolerance band of the bearing is matched with the shaft tolerance band, the tolerance code of the original transition fit in the general base hole system will become a win-win match, such as k5, k6, m5, m6, n6, etc., but the win is not Large; when the bearing inner diameter tolerance generation is combined with h5, h6, g5, g6, etc., it is not a gap and becomes a win-win match.

2 bearing outer diameter tolerance zone is a special tolerance zone because the tolerance value is different from the general reference axis. In most cases, the outer ring is fixed in the casing hole, and some bearing components require structural adjustment. Too tight, often with H6, H7, J6, J7, Js6, Js7 and so on.

Through the analysis of the tolerances of deep groove ball bearings, we can further understand the deep groove ball bearings. Nowadays, deep groove ball bearings play an important role in low noise motors, motorcycles, general machinery and precision instruments. Accelerating the research of deep groove ball bearings has become the focus of many experts and scholars.
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