Bearing friction torque measuring device

Abstract

To directly and highly accurately measure friction torque of a bearing single body while applying at least one of radial load and axial load of a magnitude corresponding to an actual operating condition of the bearing.SOLUTION: A device for measuring bearing friction torque comprises: an arm 7 which is fixed to an outer ring 1b of a bearing 1 under test in such a manner that the arm 7 does not contact a housing case 2 and a support bearing 4, and which extends in a direction intersecting an axial direction of a rotary shaft 3; a load cell 9 placed in a position to be pushed by an arm 7 by the rotation of the outer ring 1b of the bearing 1 under test; and a radial load loading mechanism 11 which can apply load to the outer ring 1b of the bearing 1 under test in a radial direction only and can adjust the magnitude of the load to be applied. The torque of arm 7 produced by rotating the rotary shaft 3 with a rotary electric machine 5 is measured with the load cell 9.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a measuring device for measuring friction torque of a bearing. [Background technology]

[0002] Patent Document 1 discloses a measuring device in which the inner ring of a test bearing is fixed to a rotating shaft and the outer ring is fixed to a bearing housing, and the rotating shaft is rotated while an axial load is applied to the test bearing by pressing the bearing housing axially with a hydrostatic air bearing, and the friction torque of the test bearing is measured with a strain gauge.

[0003] Non-Patent Document 1 discloses a measurement mechanism that measures the total friction torque of two test bearings by fixing the inner rings of two test bearings to a single rotating shaft, pressing the rotating shaft in the axial direction to apply an axial load to the two test bearings, and rotating the rotating shaft while bringing a bar attached to a floating housing fixed to the outer rings of the two test bearings into contact with a load cell fixed to the frame of the measurement device.

[0004] Non-Patent Document 2 discloses a method in which an apparatus is used in which the inner ring of a test bearing is fixed to a rotating shaft and both ends of the rotating shaft are rotatably supported by two support bearings, and the rotating shaft is rotated while only a radial load is applied to the test bearing, and the total friction torque of the test bearing and support bearings is measured with a torque meter, and then the friction torque of the test bearing is calculated by subtracting the friction torque of the support bearing alone. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 57-082729 [Non-patent literature]

[0006] [Non-Patent Document 1] Kyodo Yushi Co., Ltd., Kyodo Yushi Technical Bulletin No. 4, "Friction Torque of Rolling Bearings under Grease Lubrication", April 1, 2014<URL:https: / / www.kyodoyushi.co.jp / knowledge / technical_bulletin / > [Non-patent document 2] International Journal of Mechanical Engineering and Application,Volume4,Issue3,June 2016,Pages:130-135 Summary of the Invention [Problem to be solved by the invention]

[0007] Friction torque must be measured to understand the important characteristics of bearings such as ball bearings. It is desirable to measure the friction torque of a bearing under conditions where a radial load and an axial load that correspond to the actual conditions of use of the bearing are applied to the bearing.

[0008] The measuring device disclosed in Patent Document 1 requires the use of an aerostatic bearing to apply an axial load to the test bearing. However, aerostatic bearings have a small load capacity, and the upper limit of the axial load that can be applied is restricted by the aerostatic bearing. For this reason, it is difficult to use the measuring device disclosed in Patent Document 1 to measure friction torque under high-load conditions that correspond to the actual operating conditions of bearings.

[0009] Furthermore, the measurement mechanism disclosed in Non-Patent Document 1 uses two specimen bearings to measure the total friction torque of the two specimen bearings, and is unable to measure the friction torque of a single specimen bearing. Furthermore, Non-Patent Document 1 does not clearly state a structure for applying an axial load evenly to the two specimen bearings, so the axial loads applied to the two specimen bearings are not necessarily the same.

[0010] Furthermore, in the measurement method disclosed in Non-Patent Document 2, the total friction torque of the test bearing and the support bearing is measured, and then the friction torque of the test bearing is calculated by subtracting the friction torque of the support bearing alone, so it is not possible to directly measure the friction torque of the test bearing alone.

[0011] Therefore, an object of the present invention is to provide a measuring device that can directly measure the friction torque of a bearing alone with high precision while applying at least one of a radial load and an axial load of a magnitude that corresponds to the actual usage conditions of the bearing. [Means for solving the problem]

[0012] The bearing friction torque measuring device of the present invention comprises a storage case that houses a test bearing inside, a rotating shaft that is fixed to the inner ring of the test bearing and rotates integrally with the inner ring, a support bearing that rotatably supports the rotating shaft, a shaft drive unit that can rotate the rotating shaft, an arm that is fixed to the outer ring of the test bearing so as not to come into contact with the storage case or the support bearing and extends in a direction intersecting the axial direction of the rotating shaft, a load cell positioned in a position where it is pressed by the arm as the outer ring of the test bearing rotates, and a radial load application mechanism that can apply a load only in the radial direction to the outer ring of the test bearing and can adjust the magnitude of the load applied, and is characterized in that the load cell measures the torque of the arm generated by rotating the rotating shaft with the shaft drive unit.

[0013] In one aspect of the bearing friction torque measuring device according to the present invention, the arms may extend on both sides in a direction intersecting the axial direction of the rotating shaft, and the radial load application mechanism may be configured to apply a load to the outer ring of the test bearing only in the radial direction by applying a load evenly on both sides of the arms in the radial direction of the test bearing.

[0014] In one aspect of the bearing friction torque measuring device according to the present invention, the arm may be arranged so as to pass through holes formed in the storage case on both sides, and the radial load application mechanism may be configured to suspend radial load application weights on both sides of the arm that protrude outside the storage case.

[0015] In one aspect of the bearing friction torque measuring device according to the present invention, the device may comprise: a storage case that houses a test bearing therein; a rotating shaft that is fixed to the inner ring of the test bearing and rotates integrally with the inner ring; a support bearing that rotatably supports the rotating shaft; a shaft drive unit that can rotate the rotating shaft; an arm that is fixed to the outer ring of the test bearing so as not to come into contact with the storage case or the support bearing and extends in a direction intersecting the axial direction of the rotating shaft; a load cell that is positioned so that it is pressed by the arm when the outer ring of the test bearing rotates; and an axial load application mechanism that can apply a load to the outer ring of the test bearing only in the axial direction of the rotating shaft and can adjust the magnitude of the applied load, and the load cell may measure the torque of the arm generated when the rotating shaft is rotated by the shaft drive unit.

[0016] In one aspect of the bearing friction torque measuring device according to the present invention, the arms may extend on both sides in a direction intersecting the axial direction of the rotating shaft, and the axial load applying mechanism may be configured to apply a load to the outer ring of the test bearing only in the axial direction of the rotating shaft by applying a load evenly on both sides of the arms in the axial direction of the test bearing.

[0017] In one aspect of the bearing friction torque measuring device according to the present invention, the arm may be arranged so that it passes through holes formed in the storage case on both sides, and the axial load application mechanism may be configured such that axial load application weights are connected to both sides of the arm that protrude outside the storage case.

[0018] In one aspect of the bearing friction torque measuring device according to the present invention, the support bearing may be positioned at a distance from the sample bearing that is at least five times the axial width of the sample bearing.

[0019] According to this aspect, since the support bearing is separated from the test bearing, the influence of heat generated by friction torque generated in the support bearing being transmitted to the test bearing can be reduced.

[0020] In one aspect of the bearing friction torque measuring device according to the present invention, a lubricating oil supply means may be provided for supplying lubricating oil at an arbitrary flow rate to the test bearing.

[0021] In one aspect of the bearing friction torque measuring device according to the present invention, a flexible tube may be provided for supplying the lubricating oil to the test bearing, and an oil drain port for discharging the lubricating oil from the test bearing into the storage case may be provided in a position that does not come into contact with the storage case.

[0022] According to this aspect, lubricating oil can be supplied to and circulated through the test bearing without interfering with the rotation of the outer ring of the test bearing and the arm. [Effects of the Invention]

[0023] The present invention can provide a measuring device that can directly measure the friction torque of a bearing alone with high precision while applying at least one of a radial load and an axial load of a magnitude that corresponds to the actual usage conditions of the bearing. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a perspective view of a friction torque measuring device for a bearing according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a cross-sectional view taken along line AA in FIG. [Figure 3] FIG. 2 is a cross-sectional view taken along the line BB in FIG. [Figure 4] FIG. 2 is a top view of the friction torque measuring device for a bearing according to the present embodiment. [Figure 5] 10 is a graph showing the results of an evaluation test on the measurement error of a load cell using a testing machine of the friction torque measuring device for a bearing according to the present embodiment. [Figure 6] 10 is a graph showing the results of an evaluation test conducted on the reproducibility of measured values ​​of friction torque using a testing machine of the friction torque measuring device for a bearing of the present embodiment. [Figure 7] 10 is a graph showing the results of measurements of the effect of the amount of oil supplied on friction torque, using a testing machine of the friction torque measuring device for a bearing of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, a friction torque measuring device 10 for a bearing according to an embodiment of the present disclosure will be described with reference to the drawings. Fig. 1 is a perspective view of the friction torque measuring device 10. Fig. 2 is a diagram showing a cross section taken along line AA in Fig. 1. Fig. 3 is a diagram showing a cross section taken along line BB in Fig. 1. Fig. 4 is a top view of the friction torque measuring device 10.

[0026] 1 and 2, the friction torque measuring device 10 comprises a storage case 2 that houses a specimen bearing 1 for which friction torque is to be measured, and a rotating shaft 3 that is fixed to the inner ring 1a of the specimen bearing 1 and rotates integrally with the inner ring 1a. The rotating shaft 3 is arranged to extend horizontally, and is rotatably supported by two support bearings 4 provided in the storage case 2. It is preferable that both of the two support bearings 4 are positioned at positions away from the specimen bearing 1 by a distance of at least five times the axial width of the specimen bearing 1.

[0027] The friction torque measuring device 10 includes a bearing housing 6 that is fixed to the outer ring 1b of the test bearing 1 so as not to come into contact with the storage case 2 and the support bearing 4. The bearing housing 6 is provided inside the storage case 2, integral with the outer ring 1b, and is rotatable coaxially with the rotation axis 3. As shown in FIGS. 1 and 3, the friction torque measuring device 10 also includes an arm 7 that is fixed to the bearing housing 6 and extends in a direction intersecting the rotation axis 3. The arm 7 extends horizontally to both sides from a central portion that is fixed to the bearing housing 6, and is positioned so that it passes through holes 2a formed in the storage case 2 on both sides.

[0028] 3, the friction torque measuring device 10 includes a load cell 9 arranged in a position where it is pressed by an arm 7 that rotates and swings together with the outer ring 1b of the test bearing 1. For example, the load cell 9 is fixed to the storage case 2 and arranged below the arm 7.

[0029] 4, the friction torque measuring device 10 further includes a rotating electric machine 5 as a shaft drive unit that rotates the rotating shaft 3. The rotating electric machine 5 rotates the rotating shaft 3 by belt drive. The rotating electric machine 5 can adjust the rotation speed of the rotating shaft 3.

[0030] The bearing housing 6 is in contact only with the outer ring 1b, arm 7, and lubricant supply part 8 of the test bearing 1, and not with any other parts. The arm 7 is also arranged to pass through a hole 2a formed in the storage case 2. In other words, the bearing housing 6 and arm 7 are supported only via the test bearing 1 with respect to the rotating shaft 3, which is supported by the support bearing 4. Therefore, the outer ring 1b, bearing housing 6, and arm 7 of the test bearing 1 can rotate and oscillate together coaxially with the rotating shaft 3 due to the friction torque between the inner ring 1a and outer ring 1b that accompanies the rotation of the rotating shaft 3, within the range where the arm 7 does not come into contact with the upper and lower ends of the hole 2a.

[0031] To measure the friction torque of the bearing sample 1, the rotating shaft 3 is rotated in one direction by the rotating electric machine 5. As shown by the arrow in Figure 3, when the rotating shaft 3 is rotated clockwise by the rotating electric machine 5, the friction torque of the bearing sample 1 generates a torque that rotates the outer ring 1b, bearing housing 6, and arm 7 of the bearing sample 1 clockwise. As described above, the bearing housing 6 and arm 7 are capable of coaxial rotational and oscillating motion with respect to the rotating shaft 3 via only the inner ring 1a and outer ring 1b. By measuring the torque applied to the load cell 9 by the arm 7, which rotates and oscillates together with the outer ring 1b, the friction torque generated in the outer ring 1b of the bearing sample 1 due to the rotation of the inner ring 1a can be measured with high accuracy. In this case, the load cell 9 is only affected by the friction torque between the inner ring 1a and outer ring 1b of the bearing sample 1; the load cell 9 is not affected by the friction torque generated in the support bearing 4.

[0032] In addition, because the support bearing 4 is attached to the storage case 2 independently of the bearing housing 6, it is possible to directly measure the friction torque of the specimen bearing 1 alone. Furthermore, in an embodiment in which the two support bearings 4 are positioned at a distance from the specimen bearing 1 that is at least five times the axial width of the specimen bearing 1, it is possible to reduce the effect of heat generated by the friction torque in the support bearings 4 being transmitted to the specimen bearing 1, making it possible to measure the friction torque of the specimen bearing 1 with even greater accuracy.

[0033] The friction torque measuring device 10 further includes a radial load applying mechanism for applying a radial load to the outer ring 1b of the specimen bearing 1, and an axial load applying mechanism for applying an axial load to the outer ring 1b of the specimen bearing 1. Both the radial load and the axial load can be applied directly to the support portion of the outer ring 1b of the specimen bearing 1, or indirectly via a member such as a wire. Note that while this embodiment includes both a radial load applying mechanism and an axial load applying mechanism, embodiments including only one of them are also acceptable.

[0034] A radial load is applied to the outer ring 1b in the radial direction of the bearing sample 1. In this embodiment, the radial load application mechanism is configured to apply a radial load to the outer ring 1b by suspending radial load application weights 11 on both ends of the arm 7. As shown in FIG. 3 , the radial load application mechanism suspends radial load application weights 11 of the same mass at positions equidistant from the rotating shaft 3 on both sides of the arm 7 that protrude outward from the storage case 2. This allows a radial load to be applied to the outer ring 1b in the radial direction of the bearing sample 1, i.e., downward, in addition to the weight of the outer ring 1b, bearing housing 6, and arm 7 of the bearing sample 1. The weight of the suspended radial load application weight 11 can be selected arbitrarily, making it possible to apply a radial load of a magnitude that corresponds to the actual usage conditions of the bearing sample 1. This allows the radial load application weights 11 to be used to effectively apply a radial load to the outer ring 1b. At this time, in order to adjust the left-right imbalance of the arm 7 to zero, it is preferable to locate the load application point outside the load cell 9 in the radial direction of the test bearing 1 and at a position more than twice the outer diameter of the outer ring 1b.

[0035] However, the means for applying the radial load is not limited to this. For example, a configuration may be adopted in which a wire is connected to both sides of the arm 7 and the wire is pulled via a pulley or the like to apply an upward load to the arm 7, or a configuration may be adopted in which a load is directly applied to both sides of the arm 7 by an actuator or the like.

[0036] In addition, a preload weight 12 can be attached to the end of the arm 7 on the load cell 9 side. If radial load weights 11 of the same mass are hung from both ends of the arm 7, the arm 7 may become balanced and float up from the load cell 9 without contacting it. However, by attaching the preload weight 12 to the arm 7, the arm 7 can maintain contact with the load cell 9.

[0037] An axial load is applied to the outer ring 1b in the axial direction of the test bearing 1. In this embodiment, the axial load application mechanism is configured to connect axial load application weights 13 to both sides of the arm 7 via wires 14, thereby applying an axial load to the outer ring 1b. FIG. 4 is a top view of the friction torque measuring device 10. Although not shown in FIGS. 1 to 3, as shown in FIG. 4, wires 14 for suspending the axial load application weights 13 are connected to both sides of the arm 7. For example, one wire 14 is connected to each side of the arm 7 that protrudes outside the storage case 2. These two wires 14 each extend from the arm 7 to a pulley 15 in a direction parallel to the axial direction of the rotating shaft 3, then change direction at the pulley 15 to a vertical direction and extend downward. The axial load application weight 13 can then be suspended from the lower ends of the wires 14. By hanging an axial load weight 13 from the lower end of the wire 14, the arm 7 is pulled in the axial direction of the rotating shaft 3, making it possible to apply an axial load to the outer ring 1b of the specimen bearing 1. In particular, by hanging axial load weights 13 of the same mass from two wires 14 connected to the arm 7 so that they are the same height as the rotating shaft 3 and equidistant from the rotating shaft 3, it is possible to apply an axial load precisely to the outer ring 1b of the specimen bearing 1 without tilting the arm 7. Because the weight of the hanging axial load weight 13 can be selected arbitrarily, it is possible to apply an axial load of a magnitude that matches the actual usage conditions of the specimen bearing 1.

[0038] However, the means for applying the axial load is not limited to this. For example, a configuration may be adopted in which a load is directly applied to both sides of the arm 7 by an actuator or the like.

[0039] By performing measurements with the radial load weight 11 suspended from the arm 7, it is possible to measure the friction torque of the sample bearing 1 with a radial load applied to the sample bearing 1. Also, by performing measurements with the axial load weight 13 connected to the arm 7 via a wire 14, it is possible to measure the friction torque of the sample bearing 1 with an axial load applied to the sample bearing 1. In this case, it is preferable to apply a radial load or axial load to the sample bearing 1 without applying a rotational torque of at most 10% or more to the sample bearing 1.

[0040] The friction torque measuring device 10 also includes a lubricating oil supply means for supplying lubricating oil to the test bearing 1 at a desired flow rate. As shown in FIG. 2 , the bearing housing 6 is provided with a lubricating oil supply unit 8 and an oil drain port 16. Lubricating oil can be supplied to the test bearing 1 at a desired flow rate from the lubricating oil supply unit 8 and then discharged from the oil drain port 16 for circulation. A soft flexible tube is preferably used for the oil supply path connecting to the lubricating oil supply unit 8. The oil drain port 16, which discharges the lubricating oil into the storage case 2, is preferably located in a position that does not come into contact with the storage case 2. By using a soft flexible tube for the oil supply path and locating the oil drain port 16 in a position that does not come into contact with the storage case 2, the lubricating oil can be supplied to the test bearing 1 and circulated without interfering with the rotation of the outer ring 1b, bearing housing 6, and arm 7 of the test bearing 1.

[0041] The results of evaluation tests conducted using the friction torque measuring device 10 of this embodiment are described below. First, a test to evaluate the measurement error of the load cell 9 was conducted using this testing machine. This measurement error evaluation test and other evaluation tests described below both used a compression ultra-compact load cell (model: CLS-5NA-DS) manufactured by Tokyo Measuring Instruments Laboratory Co., Ltd. In the load cell 9 measurement error evaluation test, the arm 7 was balanced left and right, and a 12 g preload weight 12 was attached to the end of the load cell 9. A weight was then hung at the position where the radial load weight 11 was hung at the end of the load cell 9. The force applied to the load cell 9 was measured while changing the weight of the weight. The results of the load cell 9 measurement error evaluation test are shown in FIG. 5. The load cell 9 measurement error relative to the weight of the weight was less than 2.4%.

[0042] Next, this testing machine was used to evaluate the reproducibility of the friction torque measurements of test bearing 1. In this evaluation test, a ball bearing was used as test bearing 1, and commercially available ATF (Toyota Genuine Auto Fluid WS part number: 08886-02305) was used as the test oil supplied to test bearing 1. The friction torque of test bearing 1 was measured at a supply oil rate of 100 ml / min, a supply oil temperature of 60°C, a radial load of 300 N, and a shaft rotation speed range of 2000 to 20,000 r / min. The measurement results are shown in Figure 6. Comparing the friction torque measured initially (n1) with the friction torque measured six days later under the same conditions (n2), the difference at a shaft rotation speed of 20,000 r / min was 2.7%, indicating that the method can be used to evaluate friction torque in sliding parts with good reproducibility.

[0043] Next, we used this testing machine to evaluate the effect of oil supply volume on friction torque. In this evaluation test, a ball bearing was used as the test bearing 1, and the same test oil was used as in the evaluation test for the reproducibility of friction torque measurements for test bearing 1. The friction torque of test bearing 1 was measured under three conditions: oil supply temperature of 60°C, radial load of 300 N, oil supply volume of 40 ml / min, 70 ml / min, and 100 ml / min, and shaft rotation speeds ranging from 2000 to 20,000 r / min. The measurement results are shown in Figure 7. The friction torque under each oil supply volume condition was nearly equivalent from 2000 r / min to 10,000 r / min, demonstrating that this testing machine can measure friction torque with high accuracy and good reproducibility, as previously mentioned. However, at rotational speeds of 12,000 r / min and above, a tendency for friction torque to decrease with a decrease in oil supply volume was observed. For example, at a rotational speed of 20,000 r / min, it can be seen that compared to the condition where the oil supply amount is 100 ml / min, friction torque is reduced by 4.3% at 70 ml / min and 12.8% at 40 ml / min. One possible reason for this trend is that, under high rotational speed conditions where the rotation speed of the lubricant oil due to the rotating ball increases and the centrifugal force applied to the lubricant also increases, the reduced oil supply amount causes an oil shortage on the rolling surfaces, etc., and as a result, rolling viscous resistance and stirring resistance, which are factors in friction torque, are reduced. [Explanation of symbols]

[0044] 1 Test bearing, 1a inner ring, 1b outer ring, 2 storage case, 2a hole, 3 rotating shaft, 4 support bearing, 5 rotating electric machine, 6 bearing housing, 7 arm, 8 lubricating oil supply part, 9 load cell, 10 friction torque measuring device, 11 radial load weight, 12 preload weight, 13 axial load weight, 14 wire, 15 pulley, 16 oil drain port.

Claims

1. a storage case for storing the test bearing therein; a rotating shaft fixed to the inner ring of the test bearing and rotating integrally with the inner ring; a support bearing that rotatably supports the rotary shaft; a shaft drive unit that can rotate the rotation shaft; an arm fixed to the outer ring of the test bearing so as not to come into contact with the storage case and the support bearing, and extending in a direction intersecting the axial direction of the rotating shaft; a load cell disposed at a position where it is pressed by the arm as the outer ring of the bearing under test rotates; a radial load applying mechanism that can apply a load only in the radial direction to the outer ring of the test bearing and can adjust the magnitude of the load to be applied; A bearing friction torque measuring device, characterized in that the torque of the arm generated by rotating the rotation shaft with the shaft drive unit is measured with the load cell.

2. 2. The bearing friction torque measuring device according to claim 1, the arms extend on both sides in a direction intersecting the axial direction of the rotation shaft, The radial load application mechanism is configured to apply a load evenly in the radial direction of the test bearing on both sides of the arm, thereby applying a load only in the radial direction to the outer ring of the test bearing.

3. 3. The bearing friction torque measuring device according to claim 2, The arm is arranged to pass through holes formed in the storage case on both sides, The bearing friction torque measuring device is characterized in that the radial load application mechanism is configured to hang radial load application weights on both sides of the arm that protrude outside the storage case.

4. a storage case for storing the test bearing therein; a rotating shaft fixed to the inner ring of the test bearing and rotating integrally with the inner ring; a support bearing that rotatably supports the rotary shaft; a shaft drive unit that can rotate the rotation shaft; an arm fixed to the outer ring of the test bearing so as not to come into contact with the storage case and the support bearing, and extending in a direction intersecting the axial direction of the rotating shaft; a load cell disposed at a position where it is pressed by the arm as the outer ring of the bearing under test rotates; an axial load applying mechanism that can apply a load to the outer ring of the test bearing only in the axial direction of the rotating shaft and can adjust the magnitude of the applied load. A bearing friction torque measuring device, characterized in that the torque of the arm generated by rotating the rotation shaft with the shaft drive unit is measured with the load cell.

5. 5. The bearing friction torque measuring device according to claim 4, the arms extend on both sides in a direction intersecting the axial direction of the rotation shaft, The axial load application mechanism is configured to apply a load to the outer ring of the test bearing only in the axial direction of the rotating shaft by applying a load evenly in the axial direction of the test bearing on both sides of the arm.

6. 6. The bearing friction torque measuring device according to claim 5, The arm is arranged to pass through holes formed in the storage case on both sides, The axial load application mechanism is configured such that axial load application weights are connected to both ends of the arm that protrude outside the storage case.

7. The friction torque measuring device for a bearing according to any one of claims 1 to 6, A bearing friction torque measuring device characterized in that the support bearing is positioned at a distance from the test bearing that is at least five times the axial width of the test bearing.

8. The friction torque measuring device for a bearing according to any one of claims 1 to 7, A bearing friction torque measuring device characterized by comprising a lubricating oil supply means for supplying lubricating oil to the test bearing at an arbitrary flow rate.

9. 9. The bearing friction torque measuring device according to claim 8, a flexible tube for supplying the lubricating oil to the test bearing; A bearing friction torque measuring device characterized in that an oil drain port for discharging the lubricating oil from the test bearing into the storage case is located in a position that does not come into contact with the storage case.

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