Analysis of the Form Scheme of IKO Wind Power Main Bearing

Writer: Eric Bearing Limited

According to understanding, the main forms of IKO spindle bearings currently used for megawatt wind turbines include 3-point bearing design and 2-point bearing design. The 2-point bearing design scheme is mainly divided into IKO spherical roller bearings and IKO spherical roller bearing combination, IKO spherical roller bearing and cylindrical roller IKO bearing combination, double row tapered roller bearing and cylindrical roller bearing combination, 2 single row tapered roller bearing combination (also divided into long shaft and short shaft These two design options), face-to-face double-row tapered roller single bearings and integrated design.

1. IKO spherical roller bearings + IKO spherical roller bearings

(1) Structure

Generally, the main shaft is supported by two IKO bearings. The main bearing near the wind wheel is an IKO spherical roller bearing, and the main bearing near the gearbox side is an IKO spherical roller bearing. The connection between the gearbox and the main shaft is expanded. Tight sleeve or bolt connection.

(2) Advantages and disadvantages of structure

The advantages of this bearing structure are: no or less load acts on the gearbox, while relying on the torsion arm to withstand less deformation, and the assembly is relatively simple.

The disadvantages are as follows:

a. The axial clearance is relatively large, and the positioning of the hub in the axial direction is not good;

b. There is no pre-tightening force on the main bearing, and the axial displacement after load is relatively large. At the same time, because there is no pre-tightening force, a single roller may not rotate, resulting in sliding, which will generate a very large peak load. Affect the life of the bearing;

c. The size of the shaft is small, and the load has a great influence on the shaft.

2. IKO spherical roller bearings + IKO cylindrical roller bearings

(1) Structure

Generally, the main shaft is supported by two bearings. The main bearing near the wind wheel is an IKO spherical roller bearing, and the main bearing near the gearbox side is an IKO cylindrical roller bearing. The two main shaft bearings share a bearing chamber, and the gearbox The connection with the main shaft adopts expansion sleeve or bolt connection.

(2) Advantages and disadvantages of structure

The advantage of this kind of bearing structure is that no or less load acts on the gearbox, while relying on the torsion arm to withstand less deformation, and the assembly is relatively simple.

The disadvantages are as follows:

a. The axial clearance is relatively large, and the positioning of the hub in the axial direction is not good;

b. There is no pre-tightening force on the main bearing, and the axial displacement after load is relatively large. At the same time, because there is no pre-tightening force, a single roller may not rotate, resulting in sliding, which will generate a very large peak load. Affect the life of IKO bearings;  IKO GE 45 ES bearings online , pls click here : 

c. The size of the main frame is large or consists of multiple components, resulting in higher cost and difficult processing of the main frame;

d. Because cylindrical roller bearings are sensitive to the coaxiality and relative deflection of the inner and outer rings, they are poor in design or assembly;

In this case, the radial clearance of the spherical roller bearing will cause damage to the cylindrical roller;

e. Due to the relatively small size of the shaft and bearing, the overall stiffness of the shaft system is relatively low, and the load has a greater impact on the shaft.

3. IKO double row tapered roller bearing + IKO cylindrical roller bearing

(1) Structure

Generally, the main shaft is supported by two bearings. Usually the main bearing near the wind turbine side is IKO double-row tapered roller bearing, and the main bearing near the gearbox side is IKO cylindrical roller bearing. The two main shaft bearings share one bearing chamber. , The connection between the gearbox and the main shaft adopts expansion sleeve or bolt connection.

(2) Advantages and disadvantages of structure

The main advantages of this IKO bearing structure are:

a. There is no axial clearance, and the axial positioning is better;

b. The bearing capacity can be increased by increasing the distance between the bearings, and the applicable range of bearings is larger;

c. The diameter of the shaft and the bearing is smaller and the cost is lower;

d. Because the axial clearance is eliminated, the overall stiffness of the shaft system is relatively high, and the dynamic load has little effect on it.

The main disadvantages of this bearing structure are:

a. Cylindrical roller bearings

Because there is no preload, a single roller may not rotate, which will cause sliding, which will generate a very large peak load and affect the life of IKO bearings. For IKO cylindrical roller bearings used in units above 3MW, the rollers The mass and inertial force are large, and the cylindrical roller bearing has no pre-tightening force, which may cause the roller to slip and damage, and the possibility of micro-pitting is greater;

b. The size of the main frame is large, the machining accuracy of the bearing chamber is relatively high or consists of more parts, and the cost of the main frame is high;

c. The assembly is more complicated;

d. The geometric tolerance requirements such as concentricity of the bearing seat are relatively high.

4. Two small diameter IKO single row tapered roller bearings

(1) Structure

Generally, the main shaft is supported by two tapered roller bearings, and the two main shaft bearings share a bearing chamber. The main shaft is generally a structure with a small diameter and a long length. The connection between the gear box and the main shaft is connected by expansion sleeves or bolts. 

(2) Advantages and disadvantages of structure

The main advantages of this bearing structure are:

a. There is no axial clearance, and the axial positioning is better;

b. The bearing capacity can be increased by increasing the distance between the bearings, and the applicable range of IKO bearings is larger;

c. The diameter of IKO bearing is smaller than that of single bearing, easy to manufacture and low cost;

d. Because the length of the main shaft is relatively long, it is easy to obtain a larger tip safety distance (the distance between the tip and the tower wall);

e. Since the two bearings are generally in a preloaded state, the overall stiffness of the shafting system is relatively large. Under the action of a large dynamic load, the structural deformation of the shafting system is relatively small and can withstand large dynamic loads.

The main disadvantages of this bearing structure are:

a. The size of the main frame is large or consists of more parts, and the main frame cost is higher;

b. It is necessary to adjust the two bearings to a certain preload during assembly, so the assembly is more complicated;

c. The concentricity requirements of the two bearing seats are relatively high, and the processing cost is relatively high;

d. The overall length of the transmission chain is long, and the size of the cabin is not compact.

e. Two single row tapered roller bearings with large diameter

5. Single bearing

(1) Structure

Single bearing structure: Generally, the main shaft is supported by a large-diameter IKO tapered roller bearing. The main shaft is generally of a large diameter and relatively short structure. The connection between the gearbox and the main shaft adopts expansion sleeve or bolt connection.

(2) Advantages and disadvantages of structure

The main advantages of this bearing structure are:

a. There is no axial clearance, and the axial positioning is better;

b. The length of the main shaft is short, the transmission chain is compact, and the length of the nacelle can be designed to be relatively short;

c. IKO bearing rollers and raceways are larger in diameter, and the shaft length is shorter, so the overall rigidity of the shaft system is large, and the structural deformation caused by the load is small;

d. IKO bearings can be lubricated on both sides, so it is easy to lubricate.

The main disadvantages of this bearing structure are:

a. As the power level increases, the diameter of the bearing will become larger and larger. For example, the outer diameter of a single bearing of a 6 MW capacity class unit reaches 3.6 m. Few bearing manufacturers can process and manufacture, so the price is relatively high;

b. Due to the large diameter of the bearing, it is difficult to design the bearing seal. The conventional design cannot achieve better sealing effect, and the cost of bearing seal is higher;

c. The rollers of IKO bearings are relatively large, and there is a possibility of sliding, and the sliding of the rollers will affect the life of the bearing;

d. The roller is similar to a cylinder. When the preload is small, there will be torsion, which will cause all the load to act on a rotor unit and cause its damage.