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Bearing has become the main supporting form of modern mechanical vehicles and has been widely used. Due to the wide application range, the types and complexity of bearings are determined. Due to strict requirements, the importance of bearing quality and performance is determined.

Functions and types of bearings

The function of bearing is to support the shaft and the rotating parts on the shaft, so that it can maintain a certain rotation accuracy and bear the load, and at the same time reduce the friction and wear caused by the relative rotating parts.

According to the working nature of bearings, they can be divided into sliding bearings and rolling bearings. Rolling bearing is a widely used supporting component in various machinery. Sliding bearings are mostly used in high-speed, heavy-load, large impact load or mechanical equipment with particularly high requirements for shaft rotation accuracy, especially when split structures are needed.

(1) rolling bearing

① Single-row radial ball bearing (radial bearing, deep groove ball bearing) features: it mainly bears radial load and requires high shaft stiffness. Application: gearbox and spindle. Model name: Example 6305.

② Double-row radial ball bearing (self-aligning ball bearing)

Features: it mainly bears radial load, double-row steel balls and spherical raceway in the outer ring, which has self-aligning performance and can automatically compensate the coaxiality error caused by deflection and shell deformation.

Application: in the parts where the bearing seat hole can not ensure strict coaxiality. Model name: example 1207 and 3303 (imported)

③ Self-aligning roller bearing (radial short cylindrical roller bearing)

Features: it mainly bears radial load, but it can also bear axial load in one direction, with high radial load bearing capacity.

Application: Work under heavy load or vibration load. Model name: model 2000.

④ Cylindrical roller bearing

Features: The inner and outer rings of the bearing can be separated, belonging to a separable bearing, and the inner ring can move freely in the axial direction. Application: The bearing is used to bear radial load.

Model name: Nj202E (imported model, inner ring with flange) NU206EC (inner ring without flange)

⑤ Centripetal thrust ball bearing (angular contact ball bearing)

Features: It can bear both radial load and axial load, and can also bear pure axial load. The limit speed is high. The ability of bearing to bear axial load is determined by contact angle. The greater α is, the greater its ability to bear axial load (α =15alpha = 25alpha = 40).

Application: Angular contact ball bearings can only bear axial force in one direction, so these bearings should be used in pairs, such as machine tool spindles.

Installation method: (1) Method 1: The narrow sides of the outer rings of the bearings at both ends are opposite, which is called face to face. When assembling, the bearing outer ring is pushed out, the gap is reduced and the bearing outer ring is ground.

(2) Method 2: The outer ring widths of the bearings at both ends are opposite, which is called reverse installation (commonly known as back-to-back), which can improve the stiffness of the bracket and improve the stress on the shaft. When assembling, mix the bearing inner ring, reduce the gap and grind the bearing inner ring.

(3) Method 3: Assemble two groups in the same direction, the assembly accuracy is 0.006 ~ 0.00/~ 0.004 mm, the pre-tightening is adjusted to 0.006 mm, and the fit clearance is 0.00 1 ~ 0.004 mm.

⑥ Single row tapered roller bearing

Features: it is mainly suitable for bearing radial and axial composite loads (mainly radial loads), and the large cone angle can also bear radial and axial composite loads mainly axial loads. The bearing is a separate bearing, and the radial clearance and axial clearance of the bearing can be adjusted during installation and use, or can be pre-interference installed.

Application: the rotating speed is not too high, the rigidity is good, and the axial and radial loads are heavy, such as bevel gear shaft. Model name: Example 30202 (imported).

⑦ Needle roller bearing:

It is divided into needle bearing with inner ring (model 74000) and needle bearing without inner ring (model 84000).

Model name: sample ina. Zarn2572-tu-ana Germany 02/b07 → Match the inner hole φ25 and the outer circle φ72 of the shaft.

8 One-way thrust ball bearing (type 8000) Two-way thrust ball bearing (type 38000) is commonly known as plane bearing.

(2) Sliding bearing: copper shaft sleeve is usually the main bearing (hydrostatic bearing, commonly known as floating bearing).

Application of bearing in gearbox of suspension motor;

Selection of bearing type

(1) Bearing load:

① Ball bearings should be the first choice for small or medium-sized loads (because the main parts of ball bearings are point contact).

② Roller bearing should be selected for heavy load (it can bear heavy load and impact load with small deformation after bearing).

(2) Select the bearing type according to the load direction.

① Only bear axial load: angular contact bearing (one-way thrust ball bearing) is selected.

② Only bear radial load: select single row radial ball bearing (deep groove ball bearing) or tapered roller bearing.

③ Bearing radial and axial alternating loads: tapered roller bearings, angular contact bearings and deep groove ball bearings are selected.

(3) Axial fixation of rolling bearings (inner ring fixation method) One end of the inner ring of a bearing is usually located by a shoulder or sleeve.

① The shaft is fixed with elastic retaining ring: it is mainly used in situations with low rotating speed and small axial load.

② Fixation of shaft end retaining ring: it can be used for high-speed and large axial load, only applicable to shaft end.

③ Fixation of round nut and brake washer: mainly used in situations with high rotating speed and large axial load.

④ Fixed bush and round nut structure: used to fasten the self-aligning bearing with small axial force and rotation speed on the long shaft.

Rolling bearing code

The code of rolling bearing consists of seven digits:

(2) Bearing inner diameter representation method:

(3) Postal code

(1) internal structure code:

This code is followed by letters after the basic generation, reflecting the different internal structures of similar bearings, such as angular contact bearings C, AC and B, which respectively represent the nominal contact angles α of 15, 25 and 40.

(2) Code for sealing, dustproof and shape change of external structure:

For example, RS, RZ, Z and FS respectively indicate that one side of the bearing has a skeleton rubber sealing ring, while R, N and NR respectively indicate that the outer ring of the bearing has a stop plate and a stop groove.

③ Tolerance grade code:

P2, P4, P5, P6, P6x and P0 are in order from high to low.

④ Representation of cage:

A: It means outer loop guidance.

B: it means inner ring guidance.

J: stands for steel plate stamping cage.

Q: bronze solid cage

M: brass solid cage

TN: engineering plastic cage

axis

(1) Crankshaft: a special part used in reciprocating machinery.

(2) Hollow shaft: used to reduce the weight of the axle while ensuring the strength and rigidity of the axle. It can also be used for conveying lubricating oil and coolant, or installing other parts and passing through the bar to be processed (such as lathe spindle hole, etc.). ).

(3) Flexible shaft: Also known as flexible shaft, it is composed of multiple layers of steel wires (such as snakeskin tube), which can flexibly transmit rotary motion and torque to any required position.

Assembly technology of spindle and bearing

(1) Check the internal control of rolling bearing and sleeve (or box hole).

Clean, trim, deburr and chamfer all parts.

(3) Measure the radial runout value of the inner and outer rings of the rolling bearing and mark the maximum value.

(4) Adjust the thickness of the washer (gasket) by grinding (high-speed grease should be added during installation, accounting for 30% of the volume of the bearing raceway cavity).

(5) After installation, check whether the radial runout of the spindle meets the requirements of the drawings.

Anti-extrusion ring

Elastic retaining ring used for (1) hole, also known as inner circlip.

(2) Elastic retaining ring for shaft, also known as outer circlip.

Sealing of shaft

Shaft seals can be divided into static seals and dynamic seals:

（ 1）

① O-ring seal (metal copper washer seal, rubber ring seal)

② Sealants (dry, non-dry and semi-dry)

③ Rubber gasket seal

② Dynamic sealing:

(1) lip seal ring of rotating shaft (secondary lip is skeleton-shaped, also called skeleton seal)

② Reciprocating lip seal (Y-shaped seal, U-shaped seal and combined seal)

Practice the installation requirements of skeleton seal:

Lubrication of bearings

Lubricants are divided into lubricating oil and lubricating grease:

Lubricating oil (1)-The greater the viscosity, the greater the internal friction resistance. Commonly used are N 10, N46 and N65.

(2) Grease-also known as cream and butter.

Note: In mechanical systems, low-viscosity lubricating oil is used in high-speed light-load environment, and high-viscosity lubricating oil is used in low-speed heavy-load environment.