A modification method for improving the edge wear of planetary gear bearings in fan gearboxes

Abstract

The present invention provides a reshaping method for improving edge wear of planetary gear bearings in wind turbine gearboxes. This method reshapes the planetary gear bearings in wind turbine gearboxes using a multi-point fitting quartic curve. Numerical calculations are then performed to obtain an expanded diagram of the oil film thickness distribution during bearing operation. The quartic reshaping curve is then adjusted based on the oil film shape in the expanded diagram to ensure a uniform axial oil film thickness in the bearing's load-bearing zone during operation, thereby evenly distributing the load. This method effectively addresses the edge load and wear issues associated with planetary gear bearings in wind turbine gearboxes, improving the bearing's operational stability and lifespan. The method also offers the advantages of intuitive and convenient reshaping curve adjustment, enabling the rapid acquisition of a suitable quartic reshaping curve.

Description

Technical Field

[0001] The invention belongs to the field of sliding bearings, and in particular relates to a shaping method for improving edge wear of a planetary gear bearing of a fan gearbox. Background Art

[0002] Wind turbine gearbox planetary gear bearings have traditionally used rolling bearings. However, rolling bearings are susceptible to damage from factors such as gear mesh vibration, accounting for 10%-20% of total wind turbine failures. Furthermore, with the development of wind turbines, high-power wind turbines are becoming a trend. Their increasing size poses significant challenges in transportation and installation, making compact wind turbine structures of great research value. Compared to rolling bearings, sliding bearings are less susceptible to gear mesh vibration, which improves gearbox life and requires less space, significantly reducing wind turbine gearbox size. However, the vertical bending moment M causes misalignment of the bearing journals during operation of the gearbox planetary gear bearings, resulting in edge loads and wear.

[0003] Relevant research shows that axial shaping is an effective method to improve the edge load and wear of the planetary gear bearings in wind turbine gearboxes. However, there is currently no effective shaping method for this purpose, which hinders the application of sliding bearings in the planetary gears of wind turbine gearboxes. Summary of the Invention

[0004] The purpose of the present invention is to provide a shaping method for improving the edge wear of the planetary gear bearings in the wind turbine gearbox. In view of the edge load and wear phenomenon caused by the misalignment of the bearing journal under low-speed and heavy-load conditions in the planetary gear sliding bearings in the wind turbine gearbox, a shaping method is proposed to evenly distribute the load and eliminate wear under rated conditions.

[0005] The present invention is achieved through the following technical solutions:

[0006] A modification method for improving the edge wear of a planetary gear bearing in a wind turbine gearbox is proposed. The method uses a quartic curve to modify the inner surface of the bearing. The quartic curve is adjusted according to the side view of the oil film after modification, and finally a quartic modification curve suitable for the bearing is obtained.

[0007] A further improvement of the present invention is that the modification curve is guessed according to the bearing load condition and a quartic modification curve f(z) is fitted through multiple reference points as follows:

[0008] f(z)=a k z k +a3z 3 +a2z 2 +a1z+a0 (1)

[0009] A further improvement of the present invention is that the oil film thickness takes into account the alignment angle between the bearing and the journal. Considering the influence of the elastic deformation of the bearing journal, the guessed quartic modification curve f(z) is brought into the oil film calculation formula, which is as follows:

[0010]

[0011] Where c is the bearing radius clearance, e is the eccentricity between the bearing and the journal, φ is the circumferential angle, γ is the attitude angle, and Δh is the difference in elastic deformation between the bearing and the journal, which is obtained by the finite element method.

[0012] A further improvement of the present invention is that the oil film pressure distribution required for the finite element calculation of the difference in elastic deformation of the bearing journal is solved by a numerical calculation method to solve the generalized Reynolds equation and energy equation that take into account the influence of surface roughness on the oil film fluid flow.

[0013] A further improvement of the present invention is that the generalized Reynolds equation is as follows:

[0014]

[0015] In the formula R is the bearing radius, φ is the circumferential angle; y is the axial coordinate; U is the journal linear velocity; ρ is the lubricating oil density; p is the oil film pressure; A is the lubricating oil density ratio; R q is the root mean square surface roughness; h is the oil film thickness; is the pressure flow factor, which represents the ratio of the average pressure flow of the oil film on the rough surface to the pressure flow on the smooth surface; is the shear flow factor, which indicates the additional transport flow carried away by the valley peaks of the roughness due to the relative sliding of the surface; η is the viscosity of the lubricating oil.

[0016] A further improvement of the present invention is that the oil film energy equation is as follows:

[0017]

[0018] Where C p is the specific heat capacity of lubricating oil, k is the thermal conductivity of lubricating oil;

[0019] A further improvement of the present invention is that the viscosity-temperature relationship is as follows:

[0020]

[0021] Where η0 is the reference viscosity at the reference temperature T0.

[0022] A further improvement of the present invention is to obtain an oil film thickness distribution expansion diagram, observe the side view of the oil film thickness distribution expansion diagram, and if the oil film shape is convex, increase the modification amount of the part with smaller oil film thickness; if the oil film shape is concave, reduce the modification amount of the part with larger oil film thickness.

[0023] A further improvement of the present invention is that the calculation is performed again after adjusting the four-times modification curve until the oil film shape approaches a straight line.

[0024] The present invention has at least the following beneficial technical effects:

[0025] 1) The present invention provides a reshaping method for improving the edge wear of the planetary gear bearings in a wind turbine gearbox. By performing four reshaping operations on the bearing surface, the edge load problem during operation of the planetary gear bearings in the wind turbine gearbox is solved, the load distribution during operation of the bearings is uniformed, the bearing wear problem is effectively reduced, and the bearing life is significantly improved.

[0026] 2) The shaping method of the present invention has the advantages of being simple and efficient. It only requires simple adjustments to the reference points through calculation to quickly and intuitively obtain an effective shaping curve, eliminating tedious calculation steps and being more efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of bearing journal misalignment.

[0028] Figure 2 Schematic diagram of bearing modification.

[0029] Figure 3 It is a modified curve diagram.

[0030] Figure 4 This is the expanded diagram of the oil film thickness distribution after f1(z) modification.

[0031] Figure 5 This is the expanded diagram of the oil film thickness distribution after f2(z) modification.

[0032] Figure 6 The expanded diagram of the oil film thickness distribution after f3(z) modification. DETAILED DESCRIPTION

[0033] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art. It should be noted that, unless there is a conflict, the embodiments of the present disclosure and the features described in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0034] Since the gears in the fan gearbox are helical gears, the planetary gears are not only subjected to vertical loads but also vertical bending moments during operation, which causes misalignment of the bearing journals, such as Figure 1As shown in the figure, high edge load is generated, which is prone to wear. Figure 2 As shown, by increasing the radial clearance of the outer edge of the bearing through modification, the load can be evenly distributed and wear can be prevented. The present invention provides a modification method for improving the edge wear of the planetary gear bearing of a wind turbine gearbox.

[0035] The quartic modification curve is guessed based on the bearing load conditions, and the quartic modification curve f(z) is fitted by adjusting the reference point.

[0036] f(z)=a4z 4 +a3z 3 +a2z 2 +a1z+a0 (1)

[0037] Substitute the modified curve into the oil film thickness equation, where the calculation of the oil film thickness takes into account the alignment angle between the bearing and the journal Considering the influence of the elastic deformation of the bearing journal, the guessed quartic modification curve f(z) is brought into the oil film calculation formula, which is as follows:

[0038]

[0039] Where c is the bearing radius clearance, e is the eccentricity between the bearing and the journal, φ is the circumferential angle, γ is the attitude angle, and Δh is the difference in elastic deformation between the bearing and the journal, which is obtained by the finite element method.

[0040] The oil film pressure distribution required for finite element calculation of the difference in elastic deformation of the bearing journal is calculated, and the generalized Reynolds equation and energy equation considering the influence of surface roughness on the oil film fluid flow are solved by numerical calculation method.

[0041] The generalized Reynolds equation is shown below:

[0042]

[0043] In the formula R is the bearing radius, φ is the circumferential angle; y is the axial coordinate; U is the journal linear velocity; ρ is the lubricating oil density; p is the oil film pressure; A is the lubricating oil density ratio; R q is the root mean square surface roughness; h is the oil film thickness; is the pressure flow factor, which represents the ratio of the average pressure flow of the oil film on the rough surface to the pressure flow on the smooth surface; is the shear flow factor, which indicates the additional transport flow carried away by the valley peaks of the roughness due to the relative sliding of the surface; η is the viscosity of the lubricating oil.

[0044] The oil film energy equation is as follows:

[0045]

[0046] Where C pis the specific heat capacity of lubricating oil, and k is the thermal conductivity of lubricating oil.

[0047] The viscosity-temperature relationship is shown below:

[0048]

[0049] Where η0 is the reference viscosity at the reference temperature T0.

[0050] Example:

[0051] In this embodiment, the operating conditions of load 900KN and speed 30r / min are selected. The specific parameters of the planetary gear bearing are as follows: nominal diameter 250mm, pitch diameter 499mm, bearing width 300mm, pad angle 340°, radial clearance 0.069mm, and the root mean square roughness value of the journal surface R q1 =0.4μm, the root mean square roughness value of the bearing surface is R q2 = 1 μm. Lubricant type VG320, oil supply temperature 60°C. Bearing material is copper alloy, journal and planetary gear material is structural steel.

[0052] First, guess the fourth-order modification curve based on the bearing parameters and working conditions, such as Figure 3 As shown in curve I, the figure only shows half of the modified curve, and the modified curve is symmetrical about the x-axis.

[0053] According to the bearing load conditions, the fourth-order modification curve f1(z) is guessed and fitted.

[0054] f1(z)=2.59×10 -12 z 4 -2.35×10 -9 z 3 +1.28×10 -6 z 2 +2.02×10 -6 z

[0055] Substitute the modified curve into the oil film thickness equation, where the calculation of the oil film thickness takes into account the alignment angle between the bearing and the journal Considering the influence of the elastic deformation of the bearing journal, the guessed quartic modification curve f1(z) is substituted into the oil film calculation formula, which is as follows:

[0056]

[0057] Where c is the bearing radius clearance, e is the eccentricity between the bearing and the journal, φ is the circumferential angle, γ is the attitude angle, and Δh is the difference in elastic deformation between the bearing and the journal, which is obtained by the finite element method.

[0058] The oil film pressure distribution required for finite element calculation of the difference in elastic deformation of the bearing journal is calculated, and the generalized Reynolds equation and energy equation considering the influence of surface roughness on the oil film fluid flow are solved by numerical calculation method.

[0059] The generalized Reynolds equation is shown below:

[0060]

[0061] In the formula R is the bearing radius, φ is the circumferential angle; y is the axial coordinate; U is the journal linear velocity; ρ is the lubricating oil density; p is the oil film pressure; A is the lubricating oil density ratio; R q is the root mean square surface roughness; h is the oil film thickness; is the pressure flow factor, which represents the ratio of the average pressure flow of the oil film on the rough surface to the pressure flow on the smooth surface; is the shear flow factor, which indicates the additional transport flow carried away by the valley peaks of the roughness due to the relative sliding of the surface; η is the viscosity of the lubricating oil.

[0062] The oil film energy equation is as follows:

[0063]

[0064] Where C p is the specific heat capacity of lubricating oil, and k is the thermal conductivity of lubricating oil.

[0065] The viscosity-temperature relationship is shown below:

[0066]

[0067] Where η0 is the reference viscosity at the reference temperature T0.

[0068] The oil film thickness distribution diagram is obtained by solving Figure 4 As shown, the oil film shape is convex. The reference point is adjusted appropriately, the outer edge modification depth is increased, and a new quartic modification curve f2(z) is obtained, as shown in Figure 3 As shown in curve II.

[0069] f2(z)=7.21×10 -11 z 4 -5.58×10 -9 z 3 +2.21×10 -6 z 2 +2.17×10 -5 z

[0070] Repeat the above calculation steps to obtain a new oil film thickness distribution diagram, such as Figure 5As shown in the figure, the oil film shape is convex. By properly adjusting the reference point and reducing the outer edge modification depth, a new fourth-order modification curve f3(z) is obtained, as shown in Figure 3 As shown in curve III.

[0071] f3(z)=-2.36×10 -11 z 4 +9.49×10 -9 z 3 +1.61×10 -6 z 2 +2.59×10 -5 z

[0072] Repeat the above calculation steps, and the new oil film thickness distribution diagram is as follows: Figure 6 As shown, the shape of the oil film is approximately a straight line, indicating that the load is evenly distributed. The quartic curve is suitable for this bearing.

[0073] Although the present invention has been described in detail above using general descriptions and specific embodiments, it will be apparent to those skilled in the art that modifications and improvements may be made based on the present invention. Therefore, such modifications and improvements, which do not depart from the spirit of the present invention, are intended to be within the scope of protection claimed herein.

Claims

1. A method for improving the edge wear of the planetary gear bearing of a fan gearbox, characterized in that: This method uses a quartic curve to modify the inner surface of the bearing, adjusts the quartic curve according to the side view of the oil film after modification, and finally obtains a quartic modification curve suitable for the bearing. The modification curve is guessed based on the bearing load conditions and fitted into a quartic modification curve f(z) through multiple reference points, as follows: <h2 style=";text-align:left;direction:ltr">f(z) = a4z<h2 style=";text-align:left;direction:ltr"> 4 <h2 style=";text-align:left;direction:ltr"> +a3z<h2 style=";text-align:left;direction:ltr"> 3 <h2 style=";text-align:left;direction:ltr"> +as2z<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> +a1z+a0 (1) The oil film thickness takes into account the bearing and journal alignment angle Considering the influence of the elastic deformation of the bearing journal, the guessed quartic modification curve f(z) is brought into the oil film calculation formula, which is as follows: Where c is the bearing radius clearance, e is the eccentricity between the bearing and the journal, φ is the circumferential angle, γ is the attitude angle, and Δh is the difference in elastic deformation of the bearing journal, which is obtained by the finite element method; The difference in elastic deformation of the bearing journal is used to calculate the required oil film pressure distribution by finite element method, and the generalized Reynolds equation and energy equation that take into account the effect of surface roughness on the oil film fluid flow are solved by numerical calculation method. The generalized Reynolds equation is shown below: In the formula R is the bearing radius, φ is the circumferential angle; y is the axial coordinate; U is the journal linear velocity; ρ is the lubricating oil density; p is the oil film pressure; A is the lubricating oil density ratio; R q is the root mean square surface roughness; h is the oil film thickness; is the pressure flow factor, which represents the ratio of the average pressure flow of the oil film on the rough surface to the pressure flow on the smooth surface; is the shear flow factor, which indicates the additional transport flow carried away by the valley peaks of the roughness due to the relative sliding of the surface; η is the viscosity of the lubricating oil.

2. A method for improving the edge wear of a planetary gear bearing in a wind turbine gearbox according to claim 1, characterized in that: The oil film energy equation is as follows: Where C p is the specific heat capacity of lubricating oil, and k is the thermal conductivity of lubricating oil.

3. A method for improving the edge wear of a planetary gear bearing in a wind turbine gearbox according to claim 2, characterized in that: The viscosity-temperature relationship is shown below: Where η0 is the reference viscosity at the reference temperature T0.

4. A method for improving the edge wear of a planetary gear bearing in a fan gearbox according to claim 3, characterized in that: Obtain the oil film thickness distribution expansion diagram and observe the side view of the oil film thickness distribution expansion diagram. If the oil film shape is convex, increase the modification amount of the part with smaller oil film thickness; if the oil film shape is concave, reduce the modification amount of the part with larger oil film thickness.

5. A method for improving the edge wear of a planetary gear bearing in a wind turbine gearbox according to claim 4, characterized in that: After adjusting the four-times reshaping curve, perform the calculation again until the oil film shape is close to a straight line.

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