How should motor bearings be selected? How can the configuration be more reasonable?

 The rotor part of the motor product usually needs to be supported by two sets of bearings, and the rotor is radially and axially positioned relative to the stator. According to different use requirements, such as: load, required rotation accuracy, and manufacturing cost, etc., the bearing configuration of the motor generally adopts: one end fixed and one end floating; Floating "floating" configuration etc.

01 One end fixed and one end floating configuration

The fixed end bearing is fixed at the same time by the shaft and the bearing chamber of the end cover, which is radially supported at one end of the shaft and plays an axial positioning role in both axial directions. The bearing at the fixed end must be a radial bearing that can withstand combined radial and axial loads. The most commonly used deep groove ball bearings in motor products are double-row or paired single-row angular contact in some other equipment and machinery. Ball bearings and other bearings that can withstand combined loads.

For motors with three-bearing structure, the combination of bearings is used for positioning, that is, radial bearings that can only bear pure radial loads (cylindrical roller bearings with rings without ribs) and deep groove balls that can bear combined loads are used. Bearing combination. In this configuration, the other bearing, the deep groove ball bearing, is only used for axial positioning in two directions, and a certain degree of radial freedom must be left in the bearing chamber, that is, a clearance fit with the diameter direction of the bearing chamber.

The floating end bearing of the motor is on the other end of the shaft, and it is only radially supported, so the bearing of the floating end can be a deep groove ball bearing or a column bearing. Cylindrical roller bearings are used. In this configuration, the shaft must be allowed to have a certain axial displacement, so that there is no mutual force between the bearings. During the operation of the motor, when the shaft expands due to heat, axial displacement can be achieved inside some types of bearings (cylindrical roller bearings). Axial displacement can also occur between one of the bearing rings and the part to which it is connected, preferably between the bearing outer ring and the bearing chamber. In view of this, the choice of N-type or NU-type bearings requires the designer to carry out comparative analysis and demonstration.

There are many different combinations of fixed and floating bearing arrangements, the following are some of the more common combinations. For rigid bearing arrangements, combinations in which axial displacement can be achieved in the bearing should be used, such as: deep groove ball bearings combined with cylindrical roller bearings; double row angular contact ball bearings combined with cylindrical roller bearings; paired single row tapered rollers Bearings and cylindrical roller bearings are combined, and of course there are other combinations. For the design of this aspect, it is recommended to conduct joint analysis and selection with bearing manufacturers.

In the above combination, the angular error between the shaft and the housing must be minimized. If the application does not allow it, it is recommended to use a combination of self-aligning bearings that can withstand a larger angular error. These configurations can withstand a certain angular error and axial displacement, and can avoid internal axial forces in the shafting.

For the bearing configuration where the inner ring is subjected to rotational load, the length change of the shaft needs to be adjusted between the bearing and its mating surface, and the axial displacement should be between the outer ring and the bearing chamber. The most commonly used combination is deep groove ball bearing and deep groove ball bearing. Ball bearing; paired single row angular contact ball bearing and deep groove ball bearing combination, etc.

02Floating bearing configuration

The floating bearing arrangement is also a cross-positioning method, which is suitable for applications where only moderate axial positioning is required, or there are other components on the shaft for axial positioning. In this configuration, the most important thing is that each bearing can be displaced axially. It can be between one of the bearing rings and its mating surface, but preferably between the bearing outer ring and the bearing chamber.

03 Pre-adjusted bearing arrangements

In a pre-adjusted bearing arrangement, the shaft is axially positioned in one direction by one bearing and held by the other bearing in the other direction. This configuration is called "cross" positioning and is typically used for shafting of shorter lengths. All radial bearings capable of bearing axial loads (in one or both directions) are suitable for this configuration. In some cases, single row angular contact ball bearings or tapered roller bearings are used in cross-located arrangements, but some preload may be required.

The harmonic reducer is the knee of the robot. Where is the performance gap between domestic and foreign products?

 The so-called harmonic reducer is a reducer made of the principle of harmonics. Compared with other reducers, it has the characteristics of compact structure, large reduction ratio, high precision and low noise. The harmonic reducer is very suitable for the joints of various robots to adjust the movement speed and output torque of each arm of the robot.

Advantages of harmonic reducers

1. High bearing capacity In harmonic transmission, the meshing of teeth and teeth is surface contact, and the number of meshing teeth (overlap coefficient) is relatively large at the same time, so the load per unit area is small, and the bearing capacity is higher than other transmission forms.

2. Large transmission ratio The transmission ratio of single-stage harmonic gear transmission can reach i=70～500.

3. Small size and light weight.

4. High transmission efficiency and long service life.

5. Smooth transmission, no impact, no noise, and high movement precision.

Harmonic reducers, especially high-precision harmonic reducers, have always been a type of product that our country has been developing. It is a revolutionary product.

The harmonic reducer has a simple and compact structure and is mainly composed of three basic components: a flexible wheel, a rigid wheel and a wave generator. The failure of the harmonic reducer is largely caused by the fatigue fracture of the flexible wheel, which affects the service life. What causes the fatigue fracture of the flex wheel of the harmonic reducer, and what can be done to better solve this problem?

1. The main reason for the fatigue fracture of the flexible wheel

The fatigue fracture of the flex wheel of the harmonic reducer mainly goes through three stages: nucleation, expansion and fracture, and the cracks are generally formed on the surface and then expand to the inside. The rate is the lowest, and the final fracture occurs when the crack expands to a larger extent.

2. Solutions to Fatigue Fracture of Flexible Wheels

1. Select high-strength and high-impact toughness materials to increase the material strength and reduce the impact toughness.

2. Strengthen the flexible wheel through material surface treatment, reduce surface defects and improve surface stress state, and prevent fatigue cracks from nucleating on the surface.

3. Make the core of the part have a good combination of strength and impact toughness, and reduce the expansion rate of fatigue cracks.

Fatigue fracture of the flex wheel is one of the main reasons for the failure of the harmonic reducer. The quality of the flex wheel directly determines the service life of the harmonic reducer. Therefore, the choice of the material of the flex wheel is very important, and the surface treatment process of the flex wheel is also very important.

my country is a big manufacturing country and is currently developing towards a manufacturing power. According to relevant statistics, in 2014, the sales volume of robots in my country was 57,000 units, of which the number of domestic robots was about 18,000 units; The sales volume has reached 248,000 units, an increase of 12% over 2014, while the consumption of industrial robots in China is 67,000 units, making it the largest market in the world.

In order to keep up with the pace of global manufacturing upgrading, my country has successively released "Made in China 2025" and the robot industry development plan, proposing that by 2020, the annual output of self-owned brand industrial robots will reach 100,000 units, and the annual output of six-axis and above industrial robots will reach 100,000 units. More than 50,000 units, cultivate more than 3 leading enterprises with international competitiveness, and create more than 5 robot supporting industrial clusters. It can be seen from this that the development potential and market prospects of robots and even harmonic reducers.

However, at present, most of the high-end robots in industrial robots are imported robots. The harmonic reducers installed in these high-end robots basically come from the products produced by Japanese HD company. In today's world market, the harmonic reducers produced by the company Almost monopolized the entire industry, so the medium and high-grade harmonic reducer has also become a bottleneck restricting the development of my country's robots and related industries.

Comprehensive analysis, if the tooth shape can be reasonably designed according to the working principle of harmonics, so that the working life of the harmonic reducer can reach the level of Japanese HD company, and at the same time, it can maintain a good running accuracy, it can be applied to medium and high-grade robots. So as to open up domestic and foreign markets.

Break through the domestic robot industry development bottle

A complete robot mainly consists of a reducer, a controller and a servo motor. As one of the three core components, the harmonic reducer has particularly high requirements for technical content. However, at present, there are very few domestic manufacturers of harmonic reducers, and even fewer can mass-produce them, which is less than 5.

The products are not only used in industrial robots, but also in aerospace, ordnance, machine tools, medical equipment and other fields. Up to now, the company's annual production capacity has reached 20,000 sets, and it has 6 national invention patents and 20 utility model technology patents. There are five series of harmonic reducer products produced by the company, with a total of more than 100 specifications, and can also be developed and customized according to customer needs.

According to reports, the entire R&D process of this project is divided into the preliminary test stage and the pilot test stage. The preliminary test stage is centered on improving product quality, and the pilot test stage is centered on improving product quality stability.

The preliminary test stage includes the research and development of tooth profile, the research and development of materials and the research and development of lubricating grease. According to the introduction of scientific researchers, according to the working principle of harmonics, a suitable tooth profile is developed, which can better conform to the conjugate principle and has better anti-load capability; During the working process, it is constantly under the action of alternating stress, and at the same time it has to transmit the load. Therefore, the flexible wheel material should have good strength; during the working process of the harmonic reducer, its working cavity is a closed container. The requirements for the lubricating grease are very strict, and the grease is required to have good lubrication, extreme pressure and thermal conductivity. For this reason, it is necessary to start from the actual working conditions of the harmonic reducer. Lubricating grease.

The pilot test stage is based on the preliminary test stage to further stabilize and improve product quality by exploring the manufacturing process, mainly including exploring and stabilizing the manufacturing process and assembly process of key parts of the harmonic reducer, as well as the performance requirements for key parts, Explore a set of effective material heat treatment process. In addition, necessary post-processing should be performed on the key parts of the harmonic reducer to further improve the performance of the parts.

Comparison of performance indicators of domestic harmonic reducers VS foreign harmonic reducers

The harmonic reducer market has always been dominated by Japanese brands. The domestic harmonic reducer has gradually occupied the market share in recent years. However, in terms of performance indicators, the domestic harmonic reducer is compared with foreign harmonic reducers. There is still a big gap in the reducer. The important performance indicators for measuring the harmonic reducer mainly include: transmission accuracy, free travel, backlash, transmission efficiency, torsional stiffness, starting torque, service life, overload performance and so on. Where is the main gap between domestic harmonic reducers and foreign harmonic reducers?

1. Gap in the form of failure

The failure mode of domestic harmonic reducer is mainly the decrease of transmission accuracy caused by gear wear; the main failure mode of foreign harmonic reducer is the damage of flexible bearing.

2. Repeated positioning accuracy stability gap

The repeated positioning accuracy of the domestic harmonic reducer can be compared with that of foreign harmonic reducers in the initial stage of use, but with the passage of time, the increased wear and tear will cause the harmonic reducer to fail, thus affecting its repeatable positioning accuracy. .

3. Differences in materials used

The harmonic reducer relies on the elastic deformation of the flexible wheel for power transmission, which has high requirements on the wear resistance and fatigue resistance of the material.

4. Differences in processing technology

The processing technology of foreign harmonic reducer manufacturers has long been able to produce 2 steel parts per minute, while domestic harmonic reducer manufacturers still use traditional slow wire walking, gear hobbing and gear shaping processes.

At present, the domestic harmonic reducer has greatly improved in terms of transmission accuracy, transmission efficiency, service life, batch consistency and other important performance indicators, and has been rapidly approaching or even surpassing foreign harmonic reducers.

There is no lubricating oil in the car wheel bearing, why is it not burned out?

 The wheel bearings of the previous model were easily damaged because the ball bearings used could not be completely sealed and depended on lubricating oil to resist wear. After tens of thousands of kilometers, there will be shortages and cannot be repaired. The method of direct replacement is adopted, so the lubricating oil will not be repeatedly applied.

 

Now cars mostly use conical bearings and bearing units, which have been developed to four generations. This style can effectively disperse the axial force caused by wheel impact, but there is also lubricating oil, but it does not need to be applied regularly.

 

The reasons for not burning out are as follows:

 

After a certain mileage, the bearing rollers will be replaced directly after deformation, and will not be repeatedly smeared with lubricating oil.

 

It is not that there is no lubricating oil, but the maintenance-free bearing is used, so it will not burn out.

 

The vehicle has been fully coated with bearings before leaving the factory, so it will not burn out.

 

The road conditions are good, the bumps are reduced, and the damage to the bearing is reduced, so it is not easy to cause problems.

 

That is to say, what we can't see does not mean there is no, but the work has been done in advance.

 

What is the role of wheel hub bearings?

 

The wheel hub bearing is one of the components that make up the chassis (suspension) of the car. It is one of the parts that can only be seen after the brake disc is removed.

 

It is called a "hub bearing" because it is a bearing used in a part called a "hub".

 

The role of the hub is to connect the brake disc to the wheel and make it spin.

 

The hub is fitted with 4 to 5 bolts. These are called "hub bolts" because they are used in the hub and install the brake discs, wheels and spacers for custom users.

 

Hub bearings are used on the outside of the rotating shaft when the hub rotates.

 

For example, third-generation hubs have grooved "splines" for mounting the driveshaft. There are also splines on the drive shaft side, so by combining these along the splines, the driving force generated by the power train is transmitted to the hub.

 

Finally, the drive shaft is attached to the hub with a large nut called a "hub nut". This is a very important part, for example, the tightening torque for a small car is about 240 N m.

 

The development history of wheel hub bearings

 

Generation wheel bearing:

 

Using the combination of two angular contact ball bearings, the outer ring is integrated, and the working gap is adjusted for one-time lubrication, and the maintenance life is about 50,000 kilometers.

 

The second generation wheel hub bearing:

 

Using the same principle as the first-generation bearing, but adding a support seat to the outer ring, improving the rigidity and reducing the stress point of the bearing, the service life is about 100,000 kilometers.

 

Three generations of wheel hub bearings:

 

On the basis of the second generation, the flange connected to the universal joint is added to effectively improve the reliability, and the service life can be used for 150,000-200,000 kilometers.

 

Fourth-generation wheel hub bearings:

 

On the basis of the third generation, the ball head shell is added, and the accuracy of the wheel hub bearing is improved. The driving force of the axle shaft and the vibration force of the tire are more dispersed, and the bearing basically reduces the force to the greatest extent while rotating.

 

Some Suggestions for Extending the Service Life of Bearings

 

In the process of daily car use, when encountering speed bumps, bumpy and unequal road conditions, release the accelerator in advance to slow down and let the vehicle pass smoothly;

 

Avoid sudden acceleration and sudden braking. Yes, sudden acceleration and sudden braking will not only adversely affect the engine, but also the moment generated by this vehicle condition will form a reverse force with the body structure, which will damage the vehicle chassis, tires and avoidance for a long time. Vibrators and bearings;

 

When replacing bearings, even if only one side is damaged, it is recommended to replace them in pairs, because one new and one old, the new one will bear more weight and wear faster; like a half shaft ball bearing, this part is only simple with the bushing Sealed, easy to collect dust and particles, it is necessary to apply lubricating oil regularly, otherwise it will be more easily damaged.

My name is SH Lee from SO ELECTRONICS MALAYSIA SDN. BHD.. After check your company product catalogue we found may be your company can produce part that can use for our new project. WE ARE LOOKING FOR STAINLESS STEEL BALL, MATERIAL SS304 AND DIAMETER 2mm.

Hi, Please quote to me the pricing of the above bearing, qty 100pcs

Hello, Can you please send me an offer for the following parts: MGW12H 1 R 500 ZF H M-1 – Hiwin MGW12H 1 R 500 ZF H M-2 - Hiwin RNU 205 SKF And can you please let me know if you have also Liqui Moly? Thank you in advance, Best regards