A device and method for measuring the overturning stiffness of a rolling bearing

Abstract

The present application belongs to the technical field of measuring rolling bearing, and particularly relates to a kind of measuring device and method of rolling bearing overturning stiffness, including upper pressing washer, loading device, torque sensor, motor, bearing, lower supporting washer, bearing support seat, sensor support seat, platform, control box, measuring table, nut A;The motor, sensor support seat and bearing support seat are fixed on the platform respectively;Torque sensor is fixed on sensor support seat, and one end of torque sensor is connected with the output shaft of motor through a high-rigidity coupling, and the other end of torque sensor is connected with loading device through a flange and bolt;The method is through high-rigidity, coaxial driving and measuring system, to bearing outer ring accurate application controllable overturning torque, and synchronous measurement its produced small overturning angular displacement, obtains the overturning stiffness of bearing by calculating the slope of moment-angular displacement relationship curve.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of measuring rolling bearings, and particularly relates to a measuring device and method for the overturning stiffness of a rolling bearing. BACKGROUND

[0002] Rolling bearings are core basic components in the mechanical industry, and their performance directly affects the precision, service life and reliability of main equipment. In high-end equipment such as precision machine tool spindles, wind power gearboxes, industrial robot joints and heavy machinery rotary supports, the rolling bearings used not only need to have high precision, but also need to withstand complex combined loads such as radial, axial and overturning moments. Under such working conditions, the overturning stiffness of the bearing is one of the key parameters for measuring its performance and ensuring system stability.

[0003] At present, there is no public and unified standard method for measuring the overturning stiffness of bearings in the rolling bearing industry, and there is a lack of special measuring devices, which leads to a lack of key data support in the design, manufacture and selection of bearings. Therefore, developing a precise, reliable and adaptable measuring device and method for the overturning stiffness of rolling bearings is a necessary and urgent task in the field. SUMMARY

[0004] The purpose of the application is to provide a measuring device and method for the overturning stiffness of a rolling bearing. The method precisely applies a controllable overturning moment to the outer ring of the bearing through a high-rigidity, coaxial driving and measuring system, and simultaneously measures the small overturning angular displacement generated thereby. The overturning stiffness of the bearing is obtained by calculating the slope of the moment-angular displacement relationship curve.

[0005] In order to achieve the above-mentioned purpose, the application adopts the following technical solutions:

[0006] A measuring device for the overturning stiffness of a rolling bearing, comprising an upper pressing washer, a loading device, a torque sensor, a motor, a bearing, a lower supporting washer, a bearing support seat, a sensor support seat, a platform, a control box, a measuring table and a nut A;

[0007] The motor, sensor support seat and bearing support seat are respectively fixed on the platform. The torque sensor is fixed on the sensor support seat, and one end of the torque sensor is connected to the output shaft of the motor through a high-rigidity coupling. The other end of the torque sensor is connected to the loading device through a flange and bolts. The inner ring of the bearing is fixed on the bearing support seat through the lower supporting washer, the upper pressing washer and the nut A. The loading device is in contact with the end face of the outer ring of the bearing and applies a torsional moment to the outer ring of the bearing, so that the outer ring of the bearing produces an inclination moment relative to the inner ring of the bearing. The measuring table is installed on the end face of the outer ring of the bearing.

[0008] The loading device comprises a loading rod, a loading bar, a nut B and a rubber sleeve; the loading rod is in the shape of "⊥", the "I" structure of which is connected with a torque sensor, the middle of the "-" structure is provided with a straight-through groove connected with the loading bar, and one side is marked with a scale, and the "0" scale is in the middle; the loading bar is provided with two, one side of the loading bar is in the form of a thread structure, is fixed on the loading rod through the nut B, the other side of the loading bar is provided with a rubber sleeve, the two loading bars are symmetrically installed on the loading rod with the "0" scale as the center, the spacing between the two loading bars is determined by the diameter of the bearing outer ring, so that the rubber sleeve can be applied to the end face of the bearing outer ring during loading, and does not interfere with the retainer and the bearing inner ring.

[0009] Further, the bearing support seat is in the shape of "convex" as a whole, and a threaded rod is arranged on the upper part of the bearing support seat, the threaded rod being used for mounting a lower supporting washer, a bearing, an upper pressing washer and a nut A.

[0010] Further, the outer diameter of the upper pressing washer is smaller than the outer diameter of the bearing inner ring and larger than the inner diameter of the bearing inner ring; the inner diameter of the upper pressing washer is larger than the diameter of the threaded rod of the bearing support seat, and is used for pressing the bearing inner ring.

[0011] Further, the known outer diameter surface of the bearing has a radius R; the measuring table is arranged at a position at a distance H from the outer diameter of the end face of the bearing outer ring, and the line connecting the measuring table and the center of the bearing is perpendicular to the loading bar.

[0012] Further, the rubber sleeve is in the shape of a circular ring as a whole, the rubber sleeve is respectively installed on one side of the two loading bars and at the same position away from the loading rod, and is used for directly contacting the end face of the bearing; the line connecting the centers of the two rubber sleeves intersects with the axis of the bearing, so as to ensure that the inclined torque applied to the bearing can directly act on the center line of the bearing, the contact between the bearing outer ring and the loading bar during loading can be surface contact, the loading force can be accurately controlled in this area, the uncertainty of the contact position between the loading bar and the surface of the bearing caused by the machining precision of the tooling is avoided, and the damage to the surface of the bearing caused by the direct contact between the loading bar and the surface of the bearing is also avoided.

[0013] Further, the lower supporting washer is in the shape of a circular ring with a boss, the outer diameter of the boss is the same as the inner diameter of the bearing, and the two are in clearance fit; the outer diameter of the lower supporting washer is smaller than the outer diameter of the bearing inner ring; the inner diameter of the lower supporting washer is the same as the diameter of the threaded rod on the bearing support seat, and the two are in clearance fit; the width of the lower supporting washer is adjusted so that the center of the bearing width and the center of the torque sensor are on the same horizontal plane.

[0014] Further, the control box is electrically connected with the motor and the torque sensor, and is used for controlling the start and stop of the motor, setting the target torque value, collecting the torque data and realizing the function of automatically stopping after reaching the preset torque.

[0015] Further, the motor stably drives the torque sensor to rotate, the torque sensor drives the loading device to act on the bearing outer ring, so that a torque is generated, when the torque sensor reaches a specified torque, a signal is transmitted to the control box, and then the control box issues an instruction to stop the motor from running, at this time, the bearing is subjected to an overturning torque.

[0016] An operation method of a rolling bearing overturning stiffness measuring device, comprising the following steps:

[0017] S1, fixing the bearing inner ring on the bearing support seat, and the bearing outer ring is in a free state;

[0018] S2, installing a measuring meter at the position of the end face of the bearing outer ring, ensuring that the bearing outer ring is in a horizontal state, and the radial center of the bearing outer ring and the radial center of the bearing inner ring are in the same plane, at this time, the indication value of the measuring meter is adjusted to zero;

[0019] S3, driving the torque sensor by the motor, and applying a pre-tightening torque M0 to the bearing outer ring through the loading device to eliminate the internal clearance of the bearing, and maintaining the torque state;

[0020] S4, sequentially applying a series of increasing test torques Mi, and Mi>M0, recording the actual torque value Mx and the measured value Sx each time; according to the formula θx=arctan(Sx / (R-H)), the overturning angle θx corresponding to each loading is calculated, wherein R is the radius of the bearing outer ring, and H is the distance from the contact point of the measuring meter to the outer diameter of the bearing; a torque M and overturning angle θ relationship curve is drawn, a linear region is selected, and the slope of the linear region is calculated as the overturning stiffness K of the bearing, K=(Mx-My) / (θx-θy), wherein (Mx, θx) and (My, θy) are two data points in the linear region.

[0021] The rolling bearing overturning stiffness measuring device and method provided by the application adopts motor and high-precision torque sensor closed-loop control, torque is accurately applied, pre-tightening torque is used to eliminate clearance, and it can be ensured that data is collected from the real elastic deformation area; by setting the zero point of the measuring meter, the influence of the bearing axial clearance on the overturning torque measurement is avoided; the spacing of the loading rods in the loading device is adjustable, and it can be adapted to bearings of different outer diameter sizes; a rubber sleeve is used at the end of the loading rod to form a surface contact with the bearing end face, which not only protects the bearing surface, but also avoids stress concentration and position uncertainty caused by point contact, and in general, the rolling bearing overturning stiffness measuring device and method of the application fills the gap of quantitative measurement of rolling bearing overturning stiffness in the industry, and meets the measurement needs of the rolling bearing industry for the overturning stiffness of the bearing. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is the overall schematic diagram of the device and method of the application;

[0023] Figure 2 is a top view of the device and method of the present invention;

[0024] Figure 3 is a schematic view of the bearing installation, loading and gauge installation of the present invention;

[0025] Figure 4 is a schematic view of the loading mechanism of the present invention;

[0026] Figure 5 is a schematic view of the loading rod of the present invention;

[0027] Figure 6 is a schematic view of the loading rod of the present invention;

[0028] Figure 7 is a schematic view of the loading rod of the present invention;

[0029] Figure 8 is a schematic view of the loading rod of the present invention;

[0030] Figure reference: 1, upper pressing washer, 2, loading device, 3, torque sensor, 4, motor, 5, bearing, 6, lower supporting washer, 7, bearing supporting seat, 8, sensor supporting seat, 9, platform, 10, control box, 11, gauge, 12, nut A, 21, loading rod, 22, loading rod, 23, nut B, 24, rubber sleeve. DETAILED DESCRIPTION

[0031] Specific embodiments 1: The technical solutions of the present invention will be described below in conjunction with examples. Obviously, the described examples are part of the embodiments of the present invention, rather than all the embodiments. Based on the examples in the present invention, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present invention. It should be noted that: in the present invention, if not specifically stated, all the embodiments and preferred implementation methods mentioned in this paper can be combined to form new technical solutions. In the present invention, if not specifically stated, all the technical features and preferred features mentioned in this paper can be combined to form new technical solutions. The "range" disclosed in the present invention in the form of lower limit and upper limit can be one or more lower limits, and one or more upper limits, respectively.

[0032] Firstly, the basic idea of the present application is that, through a high-rigidity coaxial driving and measuring system, a controllable overturning torque is accurately applied to the outer ring of the bearing 5, and the generated small overturning angular displacement is measured synchronously, the slope of the torque-angular displacement relationship curve is calculated to obtain the overturning stiffness of the bearing 5. Specifically, the inner ring of the bearing 5 is fixed, and the outer ring of the bearing 5 is in a free state. Through the loading system composed of the motor 4 and the torque sensor 3, a pure torque is applied to the end face of the outer ring of the bearing 5 through a special loading device 2 which can adapt to different sizes of the bearing 5. The displacement change of the end face of the outer ring of the bearing 5 is monitored through the measuring table 11 and converted into an overturning angle. The overturning stiffness is calculated by analyzing the relationship between the applied torque and the generated overturning angle.

[0033] Specifically, as shown in the drawings Figure 1 , the drawings Figure 2 , the drawings Figure 3 and the drawings Figure 4The application discloses a rolling bearing 5 overturning stiffness measuring device, which comprises an upper pressing washer 1, a loading device 2, a torque sensor 3, a motor 4, a bearing 5, a lower supporting washer 6, a bearing supporting seat 7, a sensor supporting seat 8, a platform 9, a control box 10, a measuring table 11 and a nut A 12. The motor 4, the sensor supporting seat 8 and the bearing supporting seat 7 are fixed on the platform 9 respectively. The torque sensor 3 is fixed on the sensor supporting seat 8, and one end of the torque sensor 3 is connected with an output shaft of the motor 4 through a high-rigidity coupling, and the other end of the torque sensor 3 is connected with the loading device 2 through a flange plate and bolts. The inner ring of the bearing 5 is fixed on the bearing supporting seat 7 through the lower supporting washer 6, the upper pressing washer 1 and the nut A 12. The loading device 2 is in contact with an outer ring end surface of the bearing 5, and a torsional moment is applied to the outer ring of the bearing 5, so that an inclination moment is generated between the outer ring of the bearing 5 and the inner ring of the bearing 5. The measuring table 11 is installed on the end surface of the outer ring of the bearing 5. The loading device 2 comprises a loading rod 21, a loading rod 22, a nut B 23 and a rubber sleeve 24. The loading rod 21 is in a whole "⊥" type, the " " structure is connected with the torque sensor 3, a straight-through groove is formed in the middle of the "—" structure and connected with the loading rod 22, and a scale is marked on one side of the "—" structure, and the "0" scale is in the middle. The loading rod 22 is provided with two loading rods 22, one side of the loading rod 22 is in a threaded structure, the loading rod 22 is fixed on the loading rod 21 through the nut B 23, the other side of the loading rod 22 is provided with the rubber sleeve 24, the two loading rods 22 are symmetrically installed on the loading rod 21 with the "0" scale as the center, the spacing between the two loading rods 22 is determined according to the diameter of the outer ring of the bearing 5, so that the rubber sleeve 24 can be applied to the end surface of the outer ring of the bearing 5 and does not interfere with the retainer and the inner ring during loading. The rubber sleeve 24 in the application is in a whole ring type, the rubber sleeve 24 is installed on one side of the two loading rods 22 and is located at the same position away from the loading rod 21, and is used for directly contacting the end surface of the bearing 5. The center line of the two rubber sleeves 24 intersects with the axis of the bearing 5, so that the inclination moment applied to the bearing 5 can directly act on the center line of the bearing 5 during loading, the contact between the outer ring of the bearing 5 and the loading rod 22 is face contact during loading, the loading force is accurately controlled in the area, the uncertainty of the contact position between the loading rod 22 and the surface of the bearing 5 caused by the machining precision of the tool is avoided, and the surface damage of the bearing 5 caused by the direct contact between the loading rod 22 and the surface of the bearing 5 is avoided.

[0034] The application is further described below in combination with the drawings and specific embodiments.

[0035] First, the radius R of the outer diameter surface of the bearing 5 is determined in combination with the theoretical drawing of the measured rolling bearing 5. The bearing support 7, the sensor support 8 and the motor 4 are installed and fixed on the platform 9. The bearing 5 is fixed on the bearing support 7 by the upper pressing washer 1, the lower supporting washer 6 and the nut A 12. The torque sensor 3 is connected with the motor 4 and fixed on the sensor support 8. One side of the loading rod 21 is connected to the torque sensor 3, and the other side is used for installing and fixing two loading rods 22. The loading rods 22 are symmetrically installed on the loading rod 21 through the nut B 23. The loading rods 22 are above and below the two ends of the outer ring of the bearing 5 respectively. Two rubber sleeves 24 are installed on the loading rods 22 respectively, and the positions are the same away from the loading rod 21. At this time, the state of the loading rods 22 is shown in the accompanying drawings. Figure 7 The measuring table 11 is placed on the outer ring end surface of the bearing 5 away from the side of the loading rod 22, and the distance from the outer diameter H of the bearing 5 is measured. At the same time, the contact points of the measuring table 11, the loading rod 22 and the bearing 5 are in the same vertical plane. The flexibility of the loading structure can adjust the distance between the loading rods 22 to adapt to bearings 5 of different outer diameter sizes. The rotation centers of the motor 4, the torque sensor 3 and the bearing 5 are coaxial. Through the design and planning of the installation and fixation of the motor 4, the torque sensor 3 and the bearing support 7, the rotation centers of the motor 4 and the torque sensor 3 are coaxial, and are in the same vertical plane with the center of the threaded rod of the bearing support 7. According to the inner diameter and width size of the bearing 5, the size of the lower supporting washer 6 is adjusted to make the center of the bearing 5 coaxial with the rotation centers of the motor 4 and the torque sensor 3. Before measurement, the outer ring of the bearing 5 should be in a horizontal state. With the help of tools, the radial center of the outer ring of the bearing 5 is in the same plane with the radial center of the inner ring of the bearing 5, and at this time the indication of the measuring table 11 is adjusted to zero. This action can avoid the influence of the axial runout of the bearing 5 on the inclination torque measurement.

[0036] The feedback value of the torque sensor 3 is set to M0 by the control box 10, so that the motor 4 runs smoothly, and the rotation speed is set to 1~3 revolutions per minute. The motor 4 drives the torque sensor 3 to rotate, and the torque sensor 3 drives the loading device 2 to act on the outer ring of the bearing 5, thereby generating torque. At this time, the state of the loading rod 22 is shown in the accompanying drawings. Figure 8The torque sensor 3 transmits a signal to the control box 10 when reaching a specified torque M0, and then the control box 10 issues an instruction to stop the motor 4 from running and lock. M0 is a pre-tightening torque, and its specific value needs to be determined according to the model and size of the bearing 5 to be measured, and needs to be sufficient to eliminate the gap but avoid causing any plastic deformation. It needs to be pointed out that the control box is a common measurement and control system in the field, which is integrated by using an industrial standard programmable logic controller (PLC), a human-machine interface (HMI), and a data acquisition module. Such a system is widely used in closed-loop control and data acquisition of physical quantities such as torque and displacement, and belongs to the prior art. For example, by using a Siemens S7-1200 series PLC, a Welling MT8102IE touch screen, and a matching analog input module, a control system with motor start-stop control, torque value setting and acquisition, and automatic shutdown function after reaching the preset value can be constructed. Therefore, the present application directly applies the prior art to realize its control and data acquisition functions.

[0037] When the pre-tightening torque M0 is applied and stabilized, a series of incremental test torque target values Mi, Mi > M0, i = 1, 2, 3... are set in the control box 10. For each Mi, the loading process is repeated, and after the torque is stabilized, the actual torque value Mx fed back by the torque sensor 3 and the indication value Sx of the measuring table 11 are recorded. The calculation formula of the overturning angle θx is as follows:

[0038] θx = arctan (Sx / (R - H)) (1)

[0039] According to the above formula, the overturning angle θx corresponding to each loading is calculated, where R is the radius of the outer ring of the bearing 5. The relationship curve between torque M and overturning angle θ is drawn, which is the M-θ curve. The linear region of the curve is selected, and the slope of the region is the overturning stiffness K of the bearing 5. The calculation formula of the stiffness K is as follows:

[0040] K = (Mx - My) / (θx - θy) (2)

[0041] Where (Mx, θx) and (My, θy) are any two data points in the linear region;

[0042] Substituting formula (1) into formula (2), the calculation formula of the overturning stiffness of the bearing 5 is as follows:

[0043] K = (Mx - My) / (arctan (Sx / (R - H)) - arctan (Sy / (R - H))) (3)

[0044] In formula (3), (Mx, Sx) and (My, Sy) are the indication values Sx and Sy of the measuring table 11 when the test torques are Mx and My, respectively. R is the radius of the outer ring of the bearing 5, and H is the distance from the measuring table 11 to the outer diameter of the bearing 5.

[0045] The above merely describes preferred embodiments of the present application, and is not intended to limit the present application in any form. Although the present application has been disclosed with preferred embodiments as above, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical contents to obtain equivalent embodiments with equivalent changes, without departing from the technical solution of the present application. Any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present application, without departing from the technical solution of the present application, still belongs to the scope of the technical solution of the present application.

Claims

1. A measuring device for the overturning stiffness of a rolling bearing, characterized in that, It includes an upper pressure washer (1), a loading device (2), a torque sensor (3), a motor (4), a bearing (5), a lower support washer (6), a bearing support seat (7), a sensor support seat (8), a platform (9), a control box (10), a measuring gauge (11), and a nut A (12); The motor (4), the sensor support seat (8), and the bearing support seat (7) are respectively fixed on the platform (9); the torque sensor (3) is fixed on the sensor support seat (8), and one end of the torque sensor (3) is connected to the output shaft of the motor (4) through a high-rigidity coupling, and the other end of the torque sensor (3) is connected to the loading device (2) through a flange and bolts; the inner ring of the bearing (5) is fixed on the bearing support seat (7) through the lower support washer (6), the upper pressure washer (1), and the nut A (12); the loading device (2) contacts the end face of the outer ring of the bearing (5) and applies a torsional moment to the outer ring of the bearing (5), causing the outer ring of the bearing (5) to generate an inclined moment relative to the inner ring of the bearing (5); the measuring gauge (11) is installed on the end face of the outer ring of the bearing (5). The loading device (2) includes a loading rod (21), a loading bar (22), a nut B (23), and a rubber sleeve (24); the loading rod (21) is integrally in an "⊥" shape, its "丨" structure is connected to the torque sensor (3), a through groove is opened in the middle of the "—" structure to connect the loading bar (22), and a scale is marked on one side, with the "0" scale in the middle; two loading bars (22) are provided, one side of the loading bar (22) is a threaded structure and is fixed on the loading rod (21) through the nut B (23), the other side of the loading bar (22) is installed with a rubber sleeve (24), and the two loading bars (22) are symmetrically installed on the loading rod (21) with the "0" scale as the center, and the distance between the two loading bars (22) is determined by the outer diameter of the outer ring of the bearing (5) to ensure that the rubber sleeve (24) can apply to the end face of the outer ring of the bearing (5) during loading and does not interfere with the cage and the inner ring of the bearing (5).

2. The measuring device for the overturning stiffness of a rolling bearing according to claim 1, characterized in that, The bearing support seat (7) is integrally in a "convex" shape, and a threaded rod is provided on the upper part of the bearing support seat (7), and the threaded rod is used to install the lower support washer (6), the bearing (5), the upper pressure washer (1), and the nut A (12).

3. The measuring device for the overturning stiffness of a rolling bearing according to claim 2, characterized in that, The outer diameter of the upper pressure washer (1) is smaller than the outer diameter of the inner ring of the bearing (5) and larger than the inner diameter of the inner ring of the bearing (5); the inner diameter of the upper pressure washer (1) is larger than the diameter of the threaded rod of the bearing support seat (7) and is used to compress the inner ring of the bearing (5).

4. The measuring device for the overturning stiffness of a rolling bearing according to claim 3, characterized in that, The measuring gauge (11) is set at a position H away from the outer diameter on the end face of the outer ring of the bearing (5), and the connection line with the center of the bearing (5) is perpendicular to the loading bar (22).

5. The measuring device for the overturning stiffness of a rolling bearing according to claim 1, characterized in that, The rubber sleeve (24) is generally circular. The rubber sleeve (24) is installed on one side of the two loading rods (22) and at the same distance from the loading rod (21) for direct contact with the end face of the bearing (5). The center line of the two rubber sleeves (24) intersects the axis of the bearing (5) to ensure that when the tilting torque is applied to the bearing (5), it can directly act on the center line of the bearing (5). This allows the outer ring of the bearing (5) to be in surface contact when loaded, and the loading force is precisely controlled within this area. This avoids the uncertainty of the contact point between the loading rod (22) and the bearing (5) surface caused by the tooling machining accuracy. It also avoids the loading rod (22) directly contacting the bearing (5) surface and causing damage to the bearing (5) surface.

6. The measuring device for the overturning stiffness of a rolling bearing according to claim 1, characterized in that, The lower support washer (6) is a ring with a boss. The outer diameter of the boss is the same as the inner diameter of the bearing (5), and the two are fitted with a clearance. The outer diameter of the lower support washer (6) is smaller than the outer diameter of the inner ring of the bearing (5). The inner diameter of the lower support washer (6) is the same as the diameter of the threaded rod on the bearing support seat (7), and the two are fitted with a clearance. The width of the lower support washer (6) is adjusted so that the center of the width of the bearing (5) and the center of the torque sensor (3) are on the same horizontal plane.

7. The measuring device for the overturning stiffness of a rolling bearing according to claim 1, characterized in that, The control box (10) is electrically connected to the motor (4) and the torque sensor (3). The control box (10) is used to control the start and stop of the motor (4), set the target torque value, collect torque data, and realize the function of automatically stopping after reaching the preset torque.

8. The measuring device for the overturning stiffness of a rolling bearing according to claim 7, characterized in that, The motor (4) drives the torque sensor (3) to rotate smoothly. The torque sensor (3) drives the loading device (2) to act on the outer ring of the bearing (5), thereby generating torque. When the torque sensor (3) reaches the specified torque, it transmits the signal to the control box (10). Then the control box (10) issues a command to stop the motor (4) from running. At this time, the bearing (5) bears the overturning torque.

9. The method of operating the measuring device for the overturning stiffness of a rolling bearing as described in any one of claims 1-8, characterized in that, Includes the following steps: S1. Fix the inner ring of the bearing (5) to the bearing support (7), and leave the outer ring of the bearing (5) in a free state. S2. Install a measuring instrument (11) on the end face of the outer ring of the bearing (5) to ensure that the outer ring of the bearing (5) is horizontal and that the radial center of the outer ring of the bearing (5) and the radial center of the inner ring are in the same plane. At this time, zero the reading of the measuring instrument (11). S3. The torque sensor (3) is driven by the motor (4) to apply a preload torque M0 to the outer ring of the bearing (5) via the loading device (2) to eliminate the internal clearance of the bearing (5) and maintain the torque state. S4. Apply a series of increasing test torques Mi in sequence, where Mi>M0, and record the actual torque value Mx and the reading Sx of the measuring instrument (11) each time; calculate the overturning angle θx corresponding to each loading according to the formula θx= arctan(Sx / (RH)), where R is the outer ring radius of the bearing (5) and H is the distance from the contact point of the measuring instrument (11) to the outer diameter of the bearing (5); plot the relationship curve between torque M and overturning angle θ, select the linear region, and calculate the slope of the region as the overturning stiffness K of the bearing (5), K=(Mx-My) / (θx-θy), where (Mx,θx) and (My,θy) are two sets of data points in the linear region.

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