Question 1

NMRV reducer selection and use instructions

Accepted Answer

1. Formal description

NMRV reducer input form is divided into: hole input, shaft input, extended worm shaft type;Reducer output type form is divided into: hole output, one-way shaft output, two-way shaft output.

Second, basic performance

1, The worm speed is less than or equal to 1400rpm;

2, The center distance is nmrv25, nmrv30, nmrv40, nmrv50, nmrv63, nmrv75, nmrv90, nmrv110, nmrv130 a total of 9 kinds;

3, The single speed ratio of 7.5, 10, 15, 20, 25,30, 40,50, 60, 80, 100 a total of 11 kinds of speed ratio;

4, Reducer can be positive, reverse direction of operation.

Third, installation

1, According to the actual requirements of a variety of installation forms, sixsurfaces can be installed;

2, The installation must be firm and reliable;

3, Prime mover, reducer between the working mechanism must be carefully aligned, the error should not be greater than the allowable compensation of the coupling used;

4, After installation by hand rotation, must be flexible, no stuck phenomenon.

Four, the use of lubricating oil replacement

1, The first use or replacement of worm gear reducer running 150-400 hours after the replacement of lubricating oil, after the oil change cycle is less than or equal to 4000 hours;

2, Regularly check the amount and quality of oil, retain enough lubricating oil, timely replacement of oil mixed with impurities or deterioration;

3, The amount of oil must be according to the requirements of the table, different grades of oil prohibited mixing, the same grade and different viscosity of the oil allowed mixing;

4, The amount of oil injection schedule l,oil according to the second schedule;

5,The working environment temperature of the reducer is -40" c -+40 C, when the ambient temperature is lower than or C, the lubrication must be heated to or before starting C or above the use of low freezing point lubricating oil.

Five, precautions

1, Not gravity hammer reducer shell, so as not to damage;

2, Regular maintenance of the installation base, seals, drive shaft, etc., is normal;

3, Such as normal use, the high temperature of the lubricating oil should be less than 85C. When the oil temperature change is abnormal and abnormal noise is generated, the machine should be shut down immediately for inspection.After exclusive failure, the main machine can continue to use;

4, The replacement of new spare parts must be run and load test before formal use.

Schedule 1: amount of oil injection

Schedule 2: Recommended lubricant grades

Question 2

What is single and multi-oil wedge bearing?

Accepted Answer

What is a single oil wedge bearing?

Single oil wedge plain bearing refers to a bearing with only one oil wedge to produce oil film pressure.

When the bearing works, if the journal is deviated from the balance position by some small interference, so that it is difficult to automatically restore to the original balance position, the journal will make a new regular or irregular movement, which is called bearing instability.

In order to improve the working stability and rotation accuracy of the bearing, the bearing is often made into a multi-oil wedge shape. Compared with the single oil wedge bearing, the multi-oil wedge bearing has good stability and high rotation accuracy, but the bearing capacity is low and the friction loss is large. Its bearing capacity is equal to the vector sum of the oil film forces in each oil wedge.

Features of single oil wedge plain bearing:

The bearing capacity is large, but the stability is poor (the journal is easy to deviate from the balance position under the action of external interference forces), so the characteristics of the multi-wedge plain bearing are: good stability, slightly lower bearing capacity, and the bearing capacity is equal to the bearing capacity vector of each oil wedge.

What is multi-oil wedge bearing?

The supporting bearing has three or more tiles with Bar-type alloy on the inner surface, which are evenly distributed along the outer circumference of the shaft diameter, and can swing locally in the structure. Multiple oil wedges can be formed in the work, and such bearings are called multi-oil wedge bearings.

Multi-oil wedge bearing has the following characteristics:

(1) Good vibration resistance, stable operation, can reduce the rotor due to unbalance or processing and installation error caused by vibration hazards;

(2) Under different loads, the eccentricity of the journal in the multi-oil wedge bearing is much smaller than that of ordinary bearings, ensuring the neutrality of the rotor;

(3) When the load and speed change, the tile can automatically adjust the position to ensure the best lubricating oil wedge, so the temperature rise is not high.

Multi-oil wedge plain bearing type:

Multi-oil wedge plain bearings are divided into elliptical bearings, fixed three-oil wedge bearings and tilting wedge bearings according to whether the tile surface is adjustable. The fixed tile bearing and elliptical bearing are bidirectional rotation, the double oil wedge, and the misaligned bearing are unidirectional rotation; Tilting tile bearings are used to adjust the clearance between the bearing bush and the shaft neck, and have good stability, but the bearing capacity is lower than that of fixed tile bearings.

(a)For the elliptical bearing, when working, can form two dynamic pressure oil film, help to improve stability. The processing of this kind of bearing is also relatively easy, the spacer of a certain thickness on the bearing's split surface, according to the circular boring, and then remove the spacer, the upper and lower close is an elliptical bearing.

For the fixed three-oil wedge bearing, when working, can form three dynamic pressure oil film, improve the rotation accuracy and stability. Fixed three-oil wedge bearings only allow the journal to rotate in a fixed direction.

(c)Tilting wedge bearing. Bearing shell by more than three pieces (usually odd) of the fan block, bearing shell supported by the screw with the ball end, one-way rotation, pivot point is not placed in the middle of the bearing and are biased to the same side of the NSK bearing, with the change of operating conditions, the tilt of the bearing can be automatically adjusted to adapt to different loads, speed, elastic deformation and deflection of the shaft, the establishment of liquid friction state.
WPS图片(1)

Question 3

What are the common wear states of bearings?

Accepted Answer

Bearing failure is a common problem in the process of bearing operation, in which the wear form is a type of bearing failure, and the wear also has great harm to the bearing, such as not a few pieces of repair will directly lead to bearing damage and break. According to the understanding of bearings, China bearing network shares several common forms of bearing wear, and hopes that when you encounter wear in the process of using bearings, you can carry out good repair according to the specific wear form.

1.Oxidative wear. The small peaks and valleys on the surface of the relative movement of the bearing are synthesized with the oxidation in the air to produce a brittle oxide that is not strongly bonded with the base metal. The oxide is easy to fall off in friction, and the wear is called oxidative wear.

2.Friction heat wear. When the bearing works under the condition of high speed heavy load and poor lubrication, high temperature, contact point hardness and wear resistance are caused by friction at the surface peak and valley, and even adhesion and tearing occur. This wear is called frictional thermal wear.

3. Abrasive wear. If the bearing is in relative motion. The bearing movement surface organization is uneven, there are hard particles, or the bearing movement surface between the sand, friction, chips and other impurities, bearing in relative movement, hard particles or impurities will make the bearing surface abrasion or even form grooves, this wear is called hard wear.

4.Pitting wear. For example, the rolling contact surface of the gear bearing is periodically subjected to great contact pressure in the relative process, and the fatigue phenomenon occurs on the metal surface for a long time, making small cracks and denuding occur on the bearing surface, which is called pitting wear.

Question 4

Seven measures to improve engine spindle bearing reliability

Accepted Answer

The main shaft bearing is the most important part of the engine, once the main shaft bearing failure will directly lead to the engine stop running, in order to improve the reliability of the engine, we must take certain measures to improve the efficiency of the bearing. According to the understanding of all aspects of bearing knowledge to share with you, we can consider from seven aspects, can improve the reliability of engine spindle bearings.

1. Improve the processing accuracy. Improve the processing accuracy of bearing components, should not be less than 4 levels of accuracy, the correct selection of reasonable clearance and the matching value of assembly. During assembly, bearings should be checked according to the contents specified in special technical conditions, such as appearance inspection, check whether there are surface defects and rust beyond the specified requirements, and check the size and original clearance of the mating place.

2.Bearing ring and axis deflection can not be large. For long-life bearings to have high reliability, the bearing ring and axis deflection under working conditions can not exceed the allowable standard (bearing life greater than 1000h, the deflection shall not exceed 0.5 ').

3.With 3-point contact ball bearings. Replacing 4-point ball bearings with 3-point contact radial thrust ball bearings can improve bearing reliability.

4.Steel cage. Replace the bronze cage with a steel cage (mostly used in Russian engines), and the cage surface is preferably silver plated.

5.The temperature difference between the inner and outer rings is less than 5℃. If the heat of the bearing can be effectively taken away and maintained on the bearing width and there is a more uniform temperature field between the outer rings, and the temperature difference between the inner and outer rings is not more than 5 ° C, the reliability of the bearing can be improved.

6.Reasonable selection of the clearance between the end face of the roller rod and the rib. In the roller bearing, the axial clearance between the end face of the roller and the rib should be between 0.04 and 0.06mm. If the clearance is greater than or less than this value, the reliability of the roller bearing will be reduced.

7.Using fine oil filter. The oil filter with high filtration degree (the filtration degree is preferably 5~15μm) is used to filter the oil.

Tips: In the engine spindle bearing, the roller bearing only bears the radial load of the rotor, while the ball bearing in addition to bear the radial load, but also bear the axial load, the working conditions are much worse than the roller bearing. In order to reduce the load of the ball bearing and improve the reliability of the engine, a roller bearing can be placed on one side of the ball bearing. Roller bearing bear radial load, ball bearing only bear axial load, so that greatly reduce the load of ball bearing, improve its working conditions.

Question 5

Bearing cage type, function and damage reasons

Accepted Answer

Although the bearing is composed of many parts, the cage can also be said to be the bearing blood vessel, so the performance of the bearing in the use of the cage material is directly related to the efficiency of bearing use, according to the summary, the following overall to share the main types of bearing cages, the main role of the cage on the bearing, and the reasons for the cage damage.

What is a bearing cage?

Bearing retainer (also known as bearing retainer) refers to a bearing part that partially wraps all or part of the rolling element and moves with it to isolate the rolling element, usually guiding the rolling element and keeping it in the bearing.

The main types of bearing cages are mainly divided into three types: nylon cages, window stamped steel cages and window brass cages. The following are the advantages and disadvantages of different types of bearing maintenance introduced by China Bearing Network.

Nylon cage: the advantages are light weight, strong elasticity, good sliding performance, good marginal lubrication performance, the disadvantage is that the operating temperature should be used below 120 degrees Celsius.

Window stamping steel cage: the advantages are light weight, high strength, no operating temperature limit, high-end shock resistance and acceleration resistance, the disadvantage is sensitive to poor lubrication.

Window brass cage: The advantages are very high strength, very high shock resistance and acceleration resistance, suitable for ultra-high speed operation associated with circulating oil lubrication. Cons: Relatively (very) expensive.

The main role of the bearing cage is:

1. The cage separates the rolling body equidistant and is distributed on the circumference of the raceway to prevent collision and friction between the rolling bodies during work;

2. Guide and drive the rolling element to roll on the correct raceway;

3. In the separation type bearing, the rolling body and a ring are combined to prevent the rolling body from falling off;

Bearing cage damage causes are:

1, Bearing lubrication is insufficient. The lubricating oil or grease is dried out, not added in time (maintenance), the lubricating oil or grease is not labeled correctly.

2, Bearing impact load. The intense vibration in the impact load produces the impact of the rolling element on the cage.

3, Bearing cleanliness. Bearings are not well sealed in the bearing box, dust enters, and friction between the rolling element and the cage is required, thus damaging the cage.

4, In the bearing cage material selection error. Various cage materials have certain requirements of temperature resistance and speed, and if the material selection is not correct, it is also the cause of cage damage.

5. Installation problems. Bearings are not installed correctly and damage the cage during installation.

6. Other reasons. If the coupling is not correct, the bearing is skewed and the force is uneven. Belt installation is too tight; Environmental problems and so on May damage the bearing or cage.

Question 6

NSK anti-creep bearing, anti-creep bearing characteristics and installation matters

Accepted Answer

NSK creep bearing, with two 0 rings on the outer ring, prevents creep by limiting the amount of clearance between the outer ring and the bearing seat. No special processing required; Bearings can use the same bearing housing as standard bearings.

In the creep limit load test, under the tension of the 0 ring installed in the outer ring, the more the bearing seat clearance is reduced, the better the anti-creep effect.

Creep bearing service characteristics:

1. Prevent creep

The O-ring prevents creep.

2, Easy to assemble

The installation can be fitted with a loose fit, so it is easy to assemble.

3. Reusable bearing seat

Bearing housing bore surface wear is minimal, so it can be reused.

4, No special processing of the bearing seat.

Since the dimensions are the same as standard bearings, the bearings can be replaced. No special treatment is required for the bearing housing.

Things to pay attention to when installing creep resistant bearings:

1, When the outer diameter of the bearing is oiled or greased, mineral oil or synthetic hydrocarbon oil (NSK EA2, etc.) can be used.

2, Standard specification of 0-ring material is nitrile rubber (applicable temperature range :-30 ~ 120°C). If it is to be used in special environments such as high temperature.

Common creep bearing application range is, as shown in the figure:

Question 7

What does rolling bearing creep refer to, bearing creep influencing factors

Accepted Answer

Creep is a common form of damage to rolling bearings, we need to distinguish the damage of bearings according to the specific damage of the bearing and then determine how to deal with the bearing, China bearing network Xiaobian according to the understanding of bearing knowledge, today to share the relevant detailed knowledge of bearing creep.

What is bearing creep?

Bearing creep refers to the relative sliding between the mating surfaces when there is a clearance on the mating surface of the bearing. The matching surfaces with creep appear to be specular bright or dark, and sometimes also have stuck wear.

There are two main types of creep of rolling bearing: inner ring creep and outer ring creep.

The creep of the inner ring of rolling bearing means that the inner ring of the bearing and the axle are fixed by interference fit to prevent the inner ring from sliding relative to the axle. However, once the appropriate amount of interference cannot be maintained, the mating surface of the inner ring and the axle will have a gap, and the inner ring will slide relative to the axle, which is called the inner ring creep.

The creep of the outer ring of the rolling bearing refers to the phenomenon that the outer ring occurs slowly rotating movement relative to the bearing seat during the use of the rolling bearing, which is called the creep of the outer ring. The outer ring creep will cause the bearing seat or outer ring wear and wear particles into the bearing, resulting in bad bearing.

Factors affecting creep of inner ring of rolling bearing:

In the early stage of the creep of the inner ring, no sharp temperature rise of the bearing was found, and the bearing temperature rise was not directly related to the creep speed of the inner ring. At the same time, when the creep speed of the inner ring increases to the rotating state, the wear of the inner ring mating surface of the shaft will be aggravated. It is clear that the bearing rotating in this state will cause the bearing temperature to rise due to the internal damage of the bearing, the aging of the lubrication state and the non-coincidence of the bearing center line.

Although the bearing temperature does not rise rapidly in the initial stage of the inner ring creep, with the development of creep, the data may be burned when the inner ring reaches the rotating state. Therefore, to prevent creep, it is very important to maintain an appropriate amount of interference between the bearing inner ring and the shaft. At the same time, in order to prevent the heat damage of the bearing, it is also crucial to equip the bearing temperature monitoring system with high reliability.

Factors affecting creep:

1, temperature, temperature increase, steady state creep rate increases

2, stress, steady creep rate increases with the increase of stress

3, the influence of microstructure, creep is a more sensitive to the microstructure of the performance index. The porosity grain size of glass has a great influence on the creep properties.

Factors affecting the creep of the outer ring of rolling bearing:

1, The impact of the coordination gap

The calculation results of the creep torque in the range of -30um-+30μm with the fit clearance are shown in Figure 1. When the fit clearance is reduced, the dawn torque decreases and the creep becomes difficult.

2. The influence of the number of rolling elements

The influence of the number of rolling elements is shown in Figure 2, and the creep torque decreases with the increase of the number of rolling elements. This is because the increase in the number of rolling elements makes the rolling element load smaller, thus restraining the local deformation of the outer ring.

3, The influence of the outer ring wall thickness

Considering increasing the rigidity of the outer ring to restrain the creep, the influence of the outer ring wall thickness (ratio to the diameter of the rolling element) is shown in Figure 3. With the increase of the outer ring wall thickness, the creep torque decreases, and the creep becomes difficult.

The continuation of bearing creep with time is roughly divided into three stages:

1, Initial creep or transitional creep, the strain increases with time, but the rate of increase gradually slows down;

2, Steady state creep or steady creep, the strain increases uniformly with the continuation of time, this stage is longer;

3, Accelerated creep, strain with the continuation of time to accelerate the increase, to the point of rupture. The greater the stress, the shorter the total creep time. The lower the stress, the longer the total creep time.

However, each material has a minimum stress value, stress below this value no matter how long it will not break, or creep time is infinite, this stress value is called the long-term strength of the material.