A new energy vehicle electric drive reduction gearbox taper bearing pre-tightening amount calculation method

Abstract

The present application relates to the technical field of bearing parameter optimization, and particularly relates to a new energy automobile electric drive reduction gearbox taper bearing pre-tightening amount calculation method. In the new energy automobile electric drive reduction gearbox taper bearing pre-tightening amount calculation method, the total installation pre-tightening amount = working pre-tightening amount - shaft elongation - two bearing assembly height increase + bearing seat elongation. The axial elongation of the shaft, bearing and bearing seat after temperature rise is taken as input, only the influence of the axial elongation on the pre-tightening amount when the temperature rises is considered, the influence of the interference amount does not need to be considered, and the calculation model can be simplified. Moreover, the bearing assembly height and bearing spacing are used for simplified calculation of the span, the bearing radial size is divided into four equal parts to simplify the diameter of the circle where the bearing outer ring raceway contact midpoint is located, the input parameters are reduced, and the calculation process is simplified.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bearing parameter optimization, and particularly relates to a new energy automobile electric drive reduction gearbox tapered bearing pre-tightening amount calculation method. BACKGROUND

[0002] The tapered bearing is a tapered roller bearing, which is commonly used in the gearbox in the automobile field to support the rotating shaft and bear the axial and radial loads. In new energy vehicles, it is also commonly used on the differential shaft and intermediate shaft of the electric drive reduction gearbox. Generally, two tapered roller bearings are arranged at the left and right ends of a shaft, and the two bearings are installed face to face. The tapered bearing is a split bearing, and pre-tightening is required when the bearing is installed. A set size gasket is usually used to achieve the desired pre-tightening force. The gasket is installed between the stepped surface of the bearing outer ring end face and the bearing seat, and the bearing outer ring is subjected to axial pressure, so that the bearing outer ring has axial displacement relative to the bearing inner assembly, thereby maintaining good contact between the roller and the raceway.

[0003] When the pre-tightening amount is too small, the bearing may have the risk of internal disengagement, unable to normally contact and run, and premature failure when working. When the pre-tightening amount is too large, the bearing may have the risk of excessive axial force, increased internal friction and serious heating when working, and even the bearing may be stuck and unable to rotate, which seriously threatens the safe driving of the vehicle. Therefore, selecting an appropriate pre-tightening amount is crucial for the normal and long-life operation of the new energy automobile electric drive reduction gearbox. Moreover, after the bearing is installed at room temperature, the shaft, bearing and bearing seat will all be deformed due to thermal expansion when working, resulting in axial elongation, which is a major influencing factor of the contact force between the roller and the raceway when working. Therefore, the influence of the temperature rise of the shaft, bearing and bearing seat needs to be considered when calculating the pre-tightening amount.

[0004] Although there are some pre-tightening amount calculation methods in the prior art, such as the bearing assembly pre-tightening amount calculation method disclosed in the Chinese patent application with the application publication number CN115438432A and the bearing assembly pre-tightening force calculation method disclosed in the Chinese patent with the authorization announcement number CN107340091B, the existing calculation methods have many input parameters, redundant input parameters, complex calculation processes, large calculation amounts, and even need to use finite element methods / software for analysis, which is difficult for general engineering technicians to operate and is difficult to guide practical engineering applications. SUMMARY

[0005] The present application aims to provide a new energy automobile electric drive reduction gearbox tapered bearing pre-tightening amount calculation method to solve the problem of complex calculation process of the current calculation method.

[0006] The technical scheme of the new energy automobile electric drive reduction gearbox tapered bearing pre-tightening amount calculation method of the present application is as follows:

[0007] A new energy automobile electric drive reduction gearbox taper bearing pre-tightening amount calculation method, the calculation equation of bearing total installation pre-tightening amount is:

[0008]

[0009] Wherein: is the total installation pre-tightening amount, is the pre-tightening amount required when the bearing is installed;

[0010] Delta is the working pre-tightening amount, which is the pre-tightening amount required by the bearing at the corresponding working temperature when working;

[0011] is the elongation of the shaft at the working temperature;

[0012] And respectively, the assembly height increase of the two tapered roller bearings matched is at the working temperature;

[0013] is the elongation of the bearing seat at the working temperature.

[0014] Further, the calculation equation of the bearing assembly height increase is:

[0015]

[0016] Wherein, is the thermal expansion coefficient of the bearing, is the temperature difference between the inner and outer rings of the bearing when working, K is a parameter related to the contact angle of the bearing, K=0.389 / tan alpha, the contact angle alpha, is the diameter of the circle where the bearing outer ring raceway contact midpoint is located; And all apply to the equation.

[0017] Further, the following approximate equation is used to calculate :

[0018]

[0019] Wherein, D is the outer diameter of the bearing, d is the inner diameter of the bearing;

[0020] Further, it is

[0021]

[0022] The equation is brought into the bearing assembly height increase calculation equation, and the bearing assembly height increase is obtained

[0023]

[0024] The bearing assembly height increase is calculated in this way.

[0025] Further, the elongation calculation equation of the shaft is

[0026]

[0027] wherein γ1 is the thermal expansion coefficient of the shaft, L0 is the span of the shaft at normal temperature corresponding to the centers of the two bearings, T0 is the set normal temperature value, and T is the working temperature. g

[0028] Further, the distance L between the opposite end faces of the two bearing inner rings is obtained, and the assembly heights of the two bearings are T A and T B ,

[0029]

[0030] The elongation calculation equation of the shaft is changed to

[0031] .

[0032] Further, the elongation calculation equation of the bearing seat is

[0033]

[0034] wherein γ2 is the thermal expansion coefficient of the bearing seat, L1 is the span of the bearing seat at normal temperature corresponding to the end faces of the two bearing outer rings, T0 is the set normal temperature value, and T is the working temperature. g

[0035] Further, the distance L between the opposite end faces of the two bearing inner rings is obtained, and the assembly heights of the two bearings are T A and T B ,

[0036]

[0037] The elongation calculation equation of the bearing seat is changed to

[0038] .

[0039] Further, the working pre-tightening amount Δ is the numerical range obtained when the bearing service life is checked in advance, which is obtained through simulation analysis.

[0040] ​​Beneficial effects: the taper bearing pre-tightening amount calculation method of the application takes the axial elongation of the shaft, bearing and bearing seat after temperature rise as input, and only considers the influence of axial elongation on pre-tightening amount during temperature rise; since the inner ring and outer ring of the tapered roller bearing of the electric drive reduction gearbox of the new energy vehicle are assembled respectively, the deformation caused by the interference fit of the bearing ring is generated before the inner and outer rings are installed together, and the pre-tightening is started after the inner and outer rings are installed together, the deformation amount during interference fit is controlled by the product production and assembly process of the bearing, and has nothing to do with the determination of the required pre-tightening amount of the bearing itself. For the calculation of the required pre-tightening amount of the bearing itself, the influence of the interference amount does not need to be considered, the calculation model can be simplified, and the calculation process is easy to operate.

[0041] Moreover, in order to further reduce the input parameters, the bearing assembly height and bearing spacing are used to simplify the calculation of the span, and the parameters that need to be measured are reduced, only one measurement parameter of bearing spacing is needed, and other bearing parameters can be obtained from the relevant manual according to the bearing model.

[0042] According to the characteristics of the taper bearing used in the electric drive reduction gearbox of the new energy vehicle, the diameter of the contact point of the bearing outer ring raceway is simplified by four equal parts of the bearing radial size, and only the inner diameter, outer diameter and contact angle of the bearing need to be obtained for calculation, and these parameters can be obtained by querying the manual, so that the parameter values required for calculation are less and can be obtained from the manual. Without complex finite element calculation, it is easy for engineering and technical personnel to master, and it is a simple and efficient calculation method with wide application. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 It is the bearing and shaft installation schematic diagram of the embodiment of the taper bearing pre-tightening amount calculation method of the new energy vehicle electric drive reduction gearbox of the application.

[0044] Figure 2 It is the bearing assembly schematic diagram of the new energy vehicle electric drive reduction gearbox taper bearing pre-tightening amount calculation method of the application. Figure 1

[0045] Figure 3 It is the bearing, shaft and bearing seat installation structure schematic diagram of the new energy vehicle electric drive reduction gearbox taper bearing pre-tightening amount calculation method of the application. Figure 2

[0046] Figure 4 It is the bearing, shaft and bearing seat installation structure schematic diagram of the new energy vehicle electric drive reduction gearbox taper bearing pre-tightening amount calculation method of the application. Figure 2

[0047] Figure 5 It is the bearing calculation parameter schematic diagram of the new energy vehicle electric drive reduction gearbox taper bearing pre-tightening amount calculation method of the application. Figure 2

[0048] Figure 6 It is the bearing outer ring raceway contact point diameter schematic diagram of the new energy vehicle electric drive reduction gearbox taper bearing pre-tightening amount calculation method of the application. Figure 5 ​​​​​

[0049] Figure 7 For Figure 6 The schematic diagram of simplified calculation parameter of bearing outer ring raceway contact point diameter in the bearing outer ring raceway contact point diameter;

[0050] Figure 8 The schematic diagram of calculation process of the embodiment of the new energy automobile electric drive reduction gearbox tapered bearing pre-tightening amount calculation method.

[0051] In the figure: 1, bearing A; 2, bearing B; 3, shaft; 4, bearing seat;

[0052] 11, bearing A inner ring; 12, bearing A roller; 13, bearing A outer ring; 21, bearing B inner ring; 22, bearing B roller; 23, bearing B outer ring. DETAILED DESCRIPTION

[0053] The basic concept of the new energy automobile electric drive reduction gearbox tapered bearing pre-tightening amount calculation method is to take the axial elongation of the shaft, bearing and bearing seat after temperature rise as input, remove the redundant parameters of bearing interference amount, simplify the calculation model; at the same time, the bearing assembly height and the bearing spacing are used to simplify the calculation of the span to obtain the elongation of the shaft and the bearing seat, the bearing outer ring raceway contact point diameter is simplified by four equal parts of the bearing radial size to obtain the increase of the bearing assembly height, and the whole calculation process only needs to measure one parameter of the bearing spacing, and the rest of the parameters can be obtained by querying the manual, which is convenient for ordinary engineering and technical personnel to calculate.

[0054] The following will be specifically described with examples.

[0055] The embodiment of the new energy automobile electric drive reduction gearbox tapered bearing pre-tightening amount calculation method of the application:

[0056] As Figure 1 , Figure 2 , Figure 3 For the convenience of understanding, the basic installation structure of the new energy automobile electric drive reduction gearbox tapered bearing is introduced first, two bearings arranged face to face are adopted, the two bearings are bearing A1 and bearing B2 respectively, the bearing A1 comprises a bearing A inner ring 11, a bearing A roller 12, a bearing A outer ring 13 and a retainer, the bearing B2 comprises a bearing B inner ring 21, a bearing B roller 22, a bearing B outer ring 23 and a retainer, the inner ring, the roller and the retainer of the bearing are assembled to form an inner assembly of the bearing, and the inner assembly and the outer ring are in separable structure. The two bearings are installed between the shaft 3 and the bearing seat 4, the shaft 3 is fixed with the bearing inner ring, the shaft 3 rotates relative to the bearing seat 4, and the bearing seat 4 can be the box body of the reduction gearbox.

[0057] Bearing A1, bearing B2 are installed at both ends of the shaft 3, the shaft 3 is provided with a step for limiting the inner ring of the two bearings axially, the two end steps are opposite, the two end steps have opposite and perpendicular to the shaft center line step surface, the inner ring of the two bearings is respectively abutted with the two side step surfaces to limit the bearing from the inside. The bearing seat 4 is provided with a mounting cavity, the mounting cavity has two side limiting surfaces opposite in the axial direction, the two side limiting surfaces limit the bearing from the outside on the opposite sides of the two bearings, and the two side limiting surfaces of the bearing seat are used to cooperate with the opposite end surfaces of the outer rings of the two bearings to limit the bearing from the outside. The gasket of corresponding thickness is installed between the limiting surface of the bearing seat and the end surface of the outer ring of the bearing to achieve the pre-tightening amount, so that the outer ring raceway, the roller and the inner ring raceway maintain appropriate contact force.

[0058] When the new energy vehicle electric drive reduction gearbox conical roller bearing is installed, the inner assembly of the bearing A1 and the bearing B2 is first installed at both ends of the shaft 3, at this time, the bearing inner ring and the shaft 3 are installed with interference, and the bearing inner ring has been deformed. Then the outer rings of the bearing A1 and the bearing B2 are respectively pressed onto the bearing inner assembly, and the bearing seat 4 can be installed together with the outer ring. At this time, the bearing has been preliminarily installed. In this state, the interference fit of the bearing has caused the deformation of the bearing, and the pre-tightening operation starts in this state. Therefore, the interference amount does not need to be considered in the bearing pre-tightening process. Therefore, the interference amount will not be the input condition of the technical scheme of the application. The inner and outer rings of the bearing are installed separately during the installation process, and the interference amount does not need to be considered. Before the gasket is installed, the size relationship between the bearing and the shaft and the bearing seat is not controlled by the bearing itself, and should not be included in the calculation of the pre-tightening amount of the bearing. By default, the pre-tightening amount is 0, and the pre-tightening amount is calculated based on this. Under the condition of limited parameters, the calculation of the pre-tightening amount can be realized.

[0059] The bearing should reach the required pre-tightening amount during work, and the working temperature is high, the bearing is installed at room temperature, which can be considered as 25±5℃, and the temperature can be calculated at that time. After the temperature rises, the shaft, the bearing and the bearing seat will be deformed, which will affect the pre-tightening amount, so it is necessary to calculate it in order to adapt to the pre-tightening amount during installation.

[0060] The calculation equation of the total installation pre-tightening amount of the bearing is:

[0061]

[0062] Among them: is the total installation pre-tightening amount, which is the pre-tightening amount required when the bearing is installed;

[0063] Δ is the working pre-tightening amount, which is the pre-tightening amount required by the bearing at the corresponding working temperature during work, which can make the raceway and the roller maintain appropriate contact force;

[0064] elongation of the shaft at working temperature;

[0065] and respectively, the assembly height increase of the two paired tapered roller bearings at working temperature;

[0066] elongation of the bearing seat at working temperature.

[0067] combined Figure 3 and Figure 4 , after the bearing is installed at normal temperature, with the increase of working temperature, the shaft and the bearing seat will be deformed. As shown in the figure, the span of the shaft at the bearing center at normal temperature is L0, which is the midpoint of the axial dimension of the bearing, and the distance between the corresponding midpoints of the two bearings on the vertical surface perpendicular to the axial direction is L0, that is, the bearing support span, after the temperature rises, the span becomes L0'. Similarly, the span L1 of the bearing seat, that is, the axial distance between the two limiting surfaces of the bearing seat, after the temperature rises, the span becomes L1'. Therefore, the deformation of the shaft and the bearing seat can be calculated by multiplying the thermal expansion coefficient by the span by the temperature rise. Here, the span of the shaft is the bearing center, considering that the shaft drives the bearing to move, and it is more appropriate to calculate according to the midpoint. Therefore, the axial elongation after the temperature rises can be expressed as:

[0068] The elongation of the shaft δ1 is:

[0069] The elongation of the bearing seat δ2 is:

[0070] Here the symbol is the normal temperature value T0, the working temperature T g , the thermal expansion coefficient of the shaft γ1 and the thermal expansion coefficient of the bearing seat γ2. L0 is the span of the shaft, and L1 is the span of the bearing seat.

[0071] Since L0, L1 are related to the bearing assembly height (total width), the bearing assembly height is the overall axial dimension of the bearing, in order to reduce the input parameters, here the bearing width and the span are used for simplified calculation. As Figure 5 shown, the distance between the two bearing inner ring relative end faces is L, which is equal to the distance between the two step surfaces of the mating inner ring end face of the shaft, and the assembly heights of bearing A1 and bearing B2 are T A and T B ,

[0072]

[0073]

[0074] The elongation calculation equation changes to:

[0075] The elongation of the shaft δ1 is:

[0076] The bearing seat elongation δ2 is:

[0077] This reduces the need to measure parameters when obtaining input parameters, simplifies the measurement process, and only needs to measure one parameter of the bearing span L, and the bearing parameters can be obtained from the relevant manual according to the bearing model.

[0078] Considering the effect of temperature on the bearing, if the temperature of the inner and outer rings and the rollers of the bearing is the same when the temperature rises, the outer ring raceway will also expand when the inner ring expands, and the overall assembly height of the bearing will not affect the pre-tightening of the bearing. However, in reality, there is always a temperature difference between the inner and outer rings of the bearing. Since the inner ring is in a rotating state, the friction is greater, and the outer ring is in a stationary state and is closer to the external environment, the temperature will be lower. The temperature difference will cause the overall assembly height of the bearing to change. According to experience, the temperature difference between the inner and outer rings is generally 5-10℃.

[0079] The calculation equation for the change of the overall assembly height of the bearing caused by the temperature difference is:

[0080]

[0081] is the increase in the assembly height of bearing A1, is the increase in the assembly height of bearing B2, where the symbol is the temperature difference T between the inner and outer rings of the bearing c , the thermal expansion coefficient γ3 of the bearing, K is a parameter related to the contact angle of the bearing, K = 0.389 / tanα, D0 is the diameter of the circle where the contact point of the bearing outer ring raceway is located, the center of the circle is on the center line of the bearing, the plane where the circle is located is perpendicular to the center line of the bearing, and the contact point is the midpoint of the contact line between the outer ring raceway and the roller, as shown in Figure 6 The equation is applicable to both bearing A1 and bearing B2, and the parameters are the same when the specifications of the two bearings are the same, and the parameters are different when the specifications of the two bearings are different.

[0082] Obviously, this D0 parameter needs to be actually measured, or a 1:1 diagram needs to be drawn for measurement, which increases the workload. Moreover, when designing the initial design of the electric drive reduction gearbox of a new energy vehicle, the parameters inside the bearing cannot always be obtained to draw the drawing. Therefore, the present application proposes a simplified algorithm.

[0083] As shown in Figure 7 , the part between the outer periphery and the inner periphery of the tapered roller bearing is equally divided into four parts, that is, the overall radial wall thickness of the bearing is equally divided into four parts, so that the D0 value can be obtained by subtracting the length of the first division from the outer diameter of the bearing. Therefore, an approximate equation of D0 can be obtained.

[0084]

[0085] Wherein, D is the bearing outer diameter, d is the bearing inner diameter;

[0086] Further, namely

[0087]

[0088] The bearing assembly height change calculation equation caused by temperature difference is obtained by bringing the above equation into the assembly height increase calculation equation:

[0089]

[0090] Therefore, only the inner and outer diameters and the contact angle of the bearing need to be obtained for calculation, and these parameters can be obtained from the manual.

[0091] In summary, the bearing pre-tightening amount calculation equation is obtained as

[0092]

[0093] The working pre-tightening amount Δ is the numerical range obtained during the early bearing life check, which can be obtained through simulation analysis.

[0094] The calculation process is summarized to obtain the calculation steps as shown in Figure 8 .

[0095] Step 1, obtain the bearing spacing (the spacing between the inner end faces of the two bearing inner rings), which is the spacing between the opposite end faces of the two bearing inner rings, which can be measured or obtained from the drawing;

[0096] Step 2, obtain the bearing parameters, including the bearing inner diameter d, the bearing outer diameter D, the assembly height T and the contact angle α; the two bearings are represented by d A , D A , T A , α A and d B , D B , T B , α B . This part can be obtained by querying the relevant bearing samples or manual.

[0097] Step 3, obtain the material parameters of the shaft, the bearing seat and the bearing. The thermal expansion coefficients are γ1 for the shaft, γ2 for the bearing seat and γ3 for the bearing; this part can be obtained by querying the relevant material manual.

[0098] Step 4, set the normal temperature value T0, the working temperature T g , the temperature difference between the inner and outer rings of the bearing T c .

[0099] Step 5, calculate the shaft elongation δ1, the bearing seat elongation δ2 and the bearing assembly height increase δA / B ;

[0100] The shaft elongation amount δ1 is:

[0101] The bearing seat elongation amount δ2 is:

[0102] The bearing assembly height increase amount δ A / δ B is:

[0103] Step 6, the total installation pre-tightening amount δ = working pre-tightening amount Δ - shaft elongation amount δ1 - bearing assembly height increase amount δ A / δ B + bearing seat elongation amount δ2; the equation is

[0104]

[0105] The working pre-tightening amount Δ is a numerical range obtained when the bearing life is checked in the early stage.

[0106] Specifically, a certain reduction gearbox bearing selects a type 32011, and the bearing parameters can be obtained by consulting the manual as shown in the table

[0107]

[0108] The material thermal expansion coefficient is

[0109]

[0110] The bearing spacing is 119.6mm, and the working pre-tightening amount obtained when the bearing life is checked in the early stage is 0~0.07mm. After calculation, the installation pre-tightening amount is 0.08~0.15mm.

[0111] The new energy automobile electric drive reduction gearbox taper bearing pre-tightening amount calculation method, by analyzing the bearing pre-tightening process, simplifying the input parameters, using the bearing internal space equal division method, establishes a simplified pre-tightening amount calculation method. By calculating the shaft, bearing seat elongation amount, bearing deformation amount based on the temperature difference between the inner and outer rings, the bearing installation pre-tightening amount is calculated. The calculation method of the present application has few input parameters, and can be calculated in the early stage of design, so as to perfect the design. The algorithm is easy for engineering and technical personnel to master, and is also convenient for embedding into design program. The calculation process is simple, and the result is reliable. Through the above four equations, the installation pre-tightening amount of the bearing can be obtained, the calculation method is simple, and the parameter values needed for calculation are few, which can be obtained through the manual. Without complex finite element calculation, it is easy for engineering and technical personnel to master, and is a simple and efficient calculation method with wide application, especially suitable for calculation without detailed input parameters.

[0112] Finally, it should be noted that the above description is only the preferred embodiments of the present application, and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art will appreciate that modifications can be made to the technical solutions described in the foregoing embodiments without departing from the spirit and principle of the present application, or some technical features thereof can be replaced by equivalent features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for calculating the preload of a cone bearing in an electric drive gearbox for new energy vehicles, characterized in that, The equation for calculating the total bearing installation preload is as follows: ,in: This is the total installation preload, which is the preload required during bearing installation. Δ represents the working preload, which is the preload required for the bearing to operate at the corresponding operating temperature. This represents the elongation of the shaft at the operating temperature. and These represent the increase in assembly height for two paired tapered roller bearings at operating temperature; This represents the elongation of the bearing housing at the operating temperature. The equation for calculating the elongation of the bearing housing is as follows: Where γ2 is the thermal expansion coefficient of the bearing housing, L1 is the span between the two outer ring end faces of the bearing housing at room temperature, T0 is the set room temperature value, and T g Operating temperature; Obtain the distance L between the opposite end faces of the inner rings of the two bearings, and the assembly heights T of the two bearings are respectively. A and T B , The equation for calculating the elongation of the bearing housing changes to: 。 2. The method for calculating the preload of the cone bearing in the electric drive reduction gearbox of a new energy vehicle according to claim 1, characterized in that, The calculation equation for the increase in bearing assembly height is as follows: ,in, This is the coefficient of thermal expansion of the bearing. The bearing temperature difference between the inner and outer rings during operation is given by K, which is a parameter related to the bearing contact angle, K = 0.389 / tanα, where α is the contact angle. It is the diameter of the circle containing the midpoint of the contact point of the outer ring raceway of the bearing; and This equation applies to all cases.

3. The method for calculating the preload of the cone bearing in the electric drive reduction gearbox of a new energy vehicle according to claim 2, characterized in that, Calculate using the following approximate equation : Where D is the outer diameter of the bearing and d is the inner diameter of the bearing; Further is Substituting this equation into the equation for calculating the increase in bearing assembly height, we obtain... This is used to calculate the increase in bearing assembly height.

4. The method for calculating the preload of the cone bearing in the electric drive reduction gearbox of a new energy vehicle according to claim 1, 2, or 3, is characterized in that, The equation for calculating the elongation of the shaft is as follows: Where γ1 is the coefficient of thermal expansion of the shaft, L0 is the span between the two bearing centers at room temperature, T0 is the set room temperature value, and T g This refers to the operating temperature.

5. The method for calculating the preload of the cone bearing in the electric drive reduction gearbox of a new energy vehicle according to claim 4, characterized in that, The equation for calculating the elongation of the shaft changes to: 。 6. The method for calculating the preload of the cone bearing in the electric drive reduction gearbox of a new energy vehicle according to claim 1, 2, or 3, is characterized in that, The working preload Δ is a value range obtained during the prior bearing life verification, and is obtained through simulation analysis.

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