A bearing tester

Abstract

The application relates to a bearing tester, and relates to a tester. The application is used to solve the problem that, when a large thrust bearing is tested, the axial loading force and the radial loading force interfere with each other, the hydraulic cylinder is easily stuck, and the outer ring of the test bearing is easily subjected to eccentric loading. The application realizes loading on the large thrust bearing through a plurality of axial force loading hydraulic cylinders, the force sensor at the head of each hydraulic cylinder is used to monitor the force at any time, so that the loading on the transmission shaft is uniform, the transmission shaft is used to realize the axial loading on the test bearing, the loading precision is high, the loading force can be directly measured, and the hydraulic cylinder that is stuck can be identified through the change of the force sensor value. The test bearing of the application is arranged on the two sides of the shaft, the loading bearing seat is arranged in the middle, different types of bearings can be tested by replacing the test bearing, and the application is used for bearing testing.

Description

Technical Field

[0001] This invention relates to a testing apparatus, particularly a testing apparatus for rolling bearings, and belongs to the field of bearing testing. Background Technology

[0002] Bearings are essential core components in mechanical transmission systems. Especially in specialized fields such as aviation and aerospace, bearings require performance evaluation to obtain their limiting performance and fundamental data. Therefore, bearing testing equipment is a crucial tool for acquiring bearing parameters.

[0003] Currently, there are many bearing testing machines in China, with varying structures and testing capabilities. Existing bearing testing machines often employ direct axial and radial force loading on the bearing for testing. For example, utility model patent document CN201555707U discloses a large bearing testing machine using this structure. This method suffers from mutual interference between axial and radial loading, easily causing the loading hydraulic cylinders to jam or leak seals. Furthermore, the axial force applied by multiple hydraulic cylinders can lead to uneven loading of the outer ring of the bearing due to jamming of one cylinder. Chinese invention patent application CN109141879A discloses a bearing testing machine that improves upon existing bearing testing equipment by adding a process bearing housing. This separates the axial and radial force loading on the test bearing and relies on a hydraulic loading cylinder at the shaft end. This solves the problem of uneven axial force loading under multi-cylinder loading and also solves the problem of hydraulic cylinder jamming or oil leakage caused by mutual interference of loading forces. However, it cannot determine whether the hydraulic cylinder is jammed or whether the axial and radial forces are applied to the bearing. Furthermore, the axial force loading error is relatively large. The bearing testing machine of this invention patent has a maximum testing speed of 20,000 rpm and a maximum axial force of 50,000 N.

[0004] All of the above bearing testers can perform rolling bearing tests, but high-speed bearing testers cannot test high-thrust bearings. Directly loading the test bearing will cause mutual interference of loading forces, which can easily lead to hydraulic cylinder jamming and failure, resulting in problems such as uneven loading on the outer ring of the test bearing.

[0005] In summary, during existing high-thrust bearing tests, the axial and radial loading forces interfere with each other, which can easily lead to hydraulic cylinder jamming and failure, and consequently cause uneven loading on the outer ring of the test bearing. Summary of the Invention

[0006] The purpose of this invention is to solve the problem that in existing high-thrust bearing tests, the axial and radial loading forces interfere with each other, easily leading to hydraulic cylinder jamming and failure, and consequently causing uneven loading on the outer ring of the test bearing. Therefore, this invention provides a bearing testing apparatus.

[0007] The technical solution of this invention is as follows: A bearing testing apparatus includes a housing, which further includes two housing bushings, a drive shaft, a transmission assembly, an axial force loading bearing housing, an axial force loading unit, an axial force bearing bushing, an axial force test bearing locking nut, a radial force loading bearing housing, a radial force locking nut, and a radial force loading unit; the two housing bushings are respectively installed on the left and right sides of the housing, and the drive shaft is rotatably mounted on the two housing bushings through the transmission assembly. The test bearing in the transmission assembly is fitted onto the drive shaft through the test bearing bushing; the axial force bearing bushing is fitted onto the drive shaft, one end of the axial force bearing bushing is positioned by a shoulder on the drive shaft, and the other end of the axial force bearing bushing is positioned by an axial force test bearing locking nut screwed onto the drive shaft, the axial force loading bearing housing is fitted onto the axial force bearing bushing, and the axial force bearing bushing is connected to the shaft... An axial force bearing is fitted between the axial force loading bearing housings. The axial force loading unit is connected to the axial force bearing bushing and applies axial force to the axial force bearing. The axial force is applied to the drive shaft through the axial force loading bearing housing and transmitted to the inner ring of the test bearing. A set of radial force bearings is fitted on the drive shaft, and one end of the radial force bearing is positioned by the shoulder of the drive shaft. The other end of the radial force bearing is positioned by a radial force locking nut screwed onto the drive shaft. The radial force loading bearing housing is fitted on the radial force bearing. The radial force loading unit passes vertically through the housing and connects to the radial force loading bearing housing, applying radial force to the radial force bearing. When axial and radial forces are applied to the test bearing, the radial force bearing in the radial force loading bearing housing will move axially, so that the radial force loading cylinder will not generate tangential force, and thus the hydraulic cylinder will not jam.

[0008] Furthermore, the transmission assembly includes a test bearing mounting base, a test bearing bushing, and a test bearing locking nut. The test bearing bushing is fitted onto the transmission shaft and is positioned by a shoulder on the transmission shaft. The test bearing is fitted onto the test bearing bushing. The test bearing locking nut is screwed onto the transmission shaft and limits the movement of the test bearing bushing. The test bearing mounting base is fitted onto the test bearing.

[0009] Furthermore, a lubrication return oil passage is provided on one of the housing bushings.

[0010] Furthermore, the axial force loading unit includes multiple sets of thrust components, which pass through the housing in a circular array along the axis of the drive shaft and are connected to the axial force loading bearing housing.

[0011] Furthermore, each thrust assembly includes an axial thrust pad, an axial force sensor, an axial extension rod, and an axial servo hydraulic cylinder, which are connected sequentially from left to right.

[0012] Furthermore, one end of the axial force-applying rod is provided with an internal thread for connection to the axial servo hydraulic cylinder, and the other end of the axial force-applying rod is provided with an external thread for connection to the axial force sensor.

[0013] Furthermore, the external thread end of the axial thrust pad is connected to the external thread section of the axial force-adding rod and the internal threads at both ends of the sensor.

[0014] Furthermore, the radial force loading unit includes a radial force thrust pad, a radial force sensor, a radial force applying rod, and a radial servo hydraulic cylinder, which are connected sequentially from top to bottom.

[0015] Furthermore, both the axial servo hydraulic cylinder and the radial servo hydraulic cylinder are low-friction dual-rod servo hydraulic cylinders.

[0016] Preferably, there is an interference fit between the test bearing and the test bearing bushing.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] 1. This invention uses several axial force loading hydraulic cylinders (i.e., axial servo hydraulic cylinders 8) to load a high-thrust bearing. The force sensor at the head of each hydraulic cylinder monitors the force in real time to ensure uniform loading of the transmission shaft. The axial loading of the test bearing is achieved by relying on the transmission shaft. The loading accuracy is high, the loading force can be directly measured, and the hydraulic cylinder that is stuck can be identified by the change in the force sensor value.

[0019] 2. In this invention, the test bearings are placed on both sides of the transmission shaft, and the load bearing housing is placed in the middle. By replacing the test bearings, different types of bearings can be tested.

[0020] 3. The test bearing bushing of the present invention can be replaced by an oil collection ring structure, which enables the measurement of the oil collection efficiency of the oil collection ring, and is of great significance for the test of the oil supply bearing under the ring. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall structure of the present invention. Detailed Implementation

[0022] Specific implementation method one: Combining Figure 1This embodiment describes a housing 1, which includes two housing bushings 2, a drive shaft 6, a transmission assembly, an axial force loading bearing housing 13, an axial force loading unit, an axial force bearing bushing 12, an axial force test bearing locking nut 16, a radial force loading bearing housing 14, a radial force locking nut 15, and a radial force loading unit. The two housing bushings 2 are respectively installed on the left and right sides of the housing 1. The drive shaft 6 is rotatably mounted on the two housing bushings 2 via the transmission assembly. The test bearing 4 in the transmission assembly is fitted onto the drive shaft 6 via a test bearing bushing 5. The axial force bearing bushing 12 is fitted onto the drive shaft 6. One end of the axial force bearing bushing 12 is positioned by a shoulder on the drive shaft 6, and the other end is positioned by the axial force test bearing locking nut 16 screwed onto the drive shaft 6. The axial force loading bearing housing 13 is fitted onto the axial force bearing bushing 12, and the axial force bearing... An axial force bearing is fitted between the bushing 12 and the axial force loading bearing housing 13. The axial force loading unit is connected to the axial force bearing bushing 12 and applies axial force to the axial force bearing. The axial force is applied to the drive shaft 6 through the axial force loading bearing housing 13 and transmitted to the inner ring of the test bearing 4. A set of radial force bearings is fitted on the drive shaft 6, and one end of the radial force bearing is positioned by the shoulder of the drive shaft 6. The other end of the radial force bearing is positioned by the radial force locking nut 15 screwed on the drive shaft 6. The radial force loading bearing housing 14 is fitted on the radial force bearing. The radial force loading unit passes vertically through the housing 1 and is connected to the radial force loading bearing housing 14 and applies radial force to the radial force bearing. When axial force and radial force are applied to the test bearing 4, the radial force bearing in the radial force loading bearing housing 14 will move axially, so that the radial force loading cylinder will not generate tangential force, and thus the hydraulic cylinder will not jam.

[0023] This invention addresses the problem of interference between axial and radial forces during high-thrust bearing testing, which can easily cause jamming in the hydraulic loading cylinders. A bearing testing apparatus is proposed to solve this issue. Relying on a force sensor mounted on the head of the hydraulic loading cylinder, the loading force on the test bearing can be directly and continuously measured. When a hydraulic cylinder jams, the sensor value at the cylinder head can be directly fed back, and even if a hydraulic cylinder jams, it will not cause unbalanced loading on the test bearing.

[0024] The housing bushing 2 of the present invention is installed at both ends of the housing 1, and the test bearing mounting seat 3 is installed on the housing bushing 2; the outer ring of the test bearing 4 is installed in the test bearing mounting seat 3, and the inner ring of the bearing is interference-fitted at both ends of the transmission shaft 6 through the test bearing bushing 5. The test bearing bushing 5 and the transmission shaft 6 are fixed by the shaft shoulder, and the test bearing locking nut 16 is axially locked; the axial force loading bearing seat 13 and the radial force loading bearing seat 14 are installed on the transmission shaft 6, between the test bearings 4, the outer ring of the bearing in the bearing seat is fixed, and the inner ring rotates, and the axial force and radial force are applied to the bearing seat by the low friction double-outlet axial servo hydraulic cylinder 8;

[0025] The axial force loading bearing housing 13 uses two sets of ball bearings that bear axial force, which are interference-fitted onto the axial force bearing bush 12. The axial force bearing bush 12 is interference-fitted onto the drive shaft 6 and fixed to the shoulder of the drive shaft 6. The test bearing lock nut 16 is tightened onto the drive shaft 6 and its end face is pressed against the rolling bearing. The outer ring of the bearing is installed in the bearing housing, and the end face of the bearing housing bears the axial force.

[0026] The radial force loading bearing housing 14 uses two sets of cylindrical roller bearings that bear radial force, which are interference-fitted onto the drive shaft 6 and fixed by the shaft shoulder; the radial force locking nut 15 is tightened onto the drive shaft 6, and its end face is pressed against the cylindrical roller bearing; the outer ring of the bearing is installed in the bearing housing, and the bearing housing bears the radial force.

[0027] There is a precise positional relationship between the radial force loading bearing housing 14 and the test bearing 4. The radial force of the test bearing is converted into the radial force applied to the radial loading bearing housing 14 through the principle of force balance, and the radial force can be accurately measured by the force sensor 10.

[0028] Specific Implementation Method Two: Combining Figure 1 This embodiment describes a transmission assembly including a test bearing mounting base 3, a test bearing bushing 5, and a test bearing locking nut 16. The test bearing bushing 5 is fitted onto the transmission shaft 6 and positioned by a shoulder on the transmission shaft 6. The test bearing 4 is fitted onto the test bearing bushing 5. The test bearing locking nut 16 is screwed onto the transmission shaft 6 and limits the position of the test bearing bushing 5. The test bearing mounting base 3 is fitted onto the test bearing 4. This configuration ensures that the test bearing 4 simulates actual usage conditions, providing the most accurate test results. Other components and connections are the same as in specific embodiment one.

[0029] Specific implementation method three: Combining Figure 1 This embodiment describes a method where one of the housing bushings 2 has a lubrication return oil passage. This arrangement facilitates cooling and lubrication of the transmission components. Other components and connections are the same as in specific embodiment two.

[0030] The test bearing bushing 5 can adopt an oil collection ring structure, which can measure the oil collection efficiency of the oil supply bearing under the ring.

[0031] Specific implementation method four: Combination Figure 1 This embodiment describes an axial force loading unit comprising multiple sets of thrust components. These thrust components are arranged in a circular array along the axis of the drive shaft 6, passing through the housing 1 and connecting to the axial force loading bearing seat 13. This arrangement facilitates the application of axial force to the test bearing 4. Other components and connections are the same as in specific embodiment three.

[0032] Specific Implementation Method Five: Combining Figure 1 This embodiment describes a thrust assembly that includes an axial thrust pad 11, an axial force sensor 10, an axial force-applying rod 9, and an axial servo hydraulic cylinder 8. These components are connected sequentially from left to right. This arrangement facilitates accurate application of axial force when force measurement is possible. Other components and connections are the same as in any of the first to fourth embodiments.

[0033] Specific Implementation Method Six: Combination Figure 1 In this embodiment, one end of the axial force-applying rod 9 has an internal thread and connects to the axial servo hydraulic cylinder 8, while the other end has an external thread and connects to the axial force sensor 10. With this configuration, the low-friction dual-output rod servo hydraulic cylinder 8 for axial force loading is mounted on the left-side housing bushing 2. Several hydraulic cylinders are inserted into holes on the distribution circle of the housing bushing and are connected to the housing bushing 2 by bolts on the hydraulic cylinder flanges. All oil inlets of the several hydraulic cylinders are connected in series via pipelines to ensure consistent pressure at the inlet ends of all hydraulic cylinders. All oil outlets of the several hydraulic cylinders are also connected in series via pipelines to ensure consistent pressure at the outlet ends of all hydraulic cylinders. Other components and connections are the same as in any of the specific embodiments one to five.

[0034] Specific implementation method seven: Combining Figure 1 In this embodiment, the external threaded end of the axial thrust pad 11 and the external threaded section of the axial force-applying rod 9 are connected to the internal threads at both ends of the sensor 10. This configuration provides a simple and reliable connection, and facilitates easy assembly and disassembly. Other components and connections are the same as in any of the specific embodiments one through six.

[0035] In this embodiment, one end of the axial thrust pad 11 is threadedly connected to the force sensor 9. One end of the axial thrust pad 11 has a spherical structure, which acts as an axial force and is applied to the bearing seat 13 to transmit the axial force.

[0036] Specific implementation method eight: Combination Figure 1This embodiment describes a radial force loading unit comprising a radial force thrust pad 17, a radial force sensor 18, a radial force applying rod 19, and a radial servo hydraulic cylinder 20. These components are connected sequentially from top to bottom. This configuration provides a simple and reliable connection method, facilitating assembly and disassembly. Other components and connections are identical to any one of embodiments one through seven.

[0037] Specific Implementation Method Nine: Combining Figure 1 In this embodiment, both the axial servo hydraulic cylinder 8 and the radial servo hydraulic cylinder 20 are low-friction dual-rod servo hydraulic cylinders. This configuration facilitates improved axial force loading accuracy, and the applied axial force is precisely adjustable. Other components and connections are the same as in any of the specific embodiments one through eight.

[0038] Specific Implementation Method Ten: Combining Figure 1 This embodiment describes an interference fit between the test bearing 4 and the test bearing bushing 5. This configuration ensures a stable and reliable connection. Other components and connections are the same as in any of the specific embodiments one through eight.

[0039] Combination Figure 1 Working principle of the invention:

[0040] The bearing testing apparatus comprises a housing, a drive shaft, test bearing mounting seats, housing bushings, a force-loading bearing housing, a hydraulic cylinder, a loading rod, a thrust pad, and a force sensor. The test bearings are respectively fixed to the test bearing mounting seats at both ends of the housing, and the test bearing mounting seats are respectively fixed to the housing bushings at both ends of the housing. The housing bushings are embedded in both ends of the housing and connected to the upper and lower housings. The two inner rings of the test bearings inside the test bearing housings are fixed to both ends of the drive shaft via inner ring bushings. The axial force loading device is located on the housing bushing on the left side, evenly distributed on a distribution circle. The axial force loading rod acts on the force-loading bearing housing at the left end and applies an axial load to the drive shaft, transferring the axial force of the drive shaft to the test bearings through the bearing inner ring bushings.

[0041] On the aforementioned drive shaft, the force-loaded bearing housing is divided into an axial force-loaded bearing housing and a radial force-loaded bearing housing, with the housing located between two experimental bearings; the inner ring of the ball bearing in the axial force-loaded bearing housing is interference-fitted onto the drive shaft through an inner ring bushing, and the end face of the inner ring bushing is locked with a nut; the roller bearing in the radial force-loaded bearing housing is interference-fitted onto the drive shaft, and the bearing end face is locked with a lock nut.

[0042] The axial force loading hydraulic cylinder is a low-friction double-rod servo hydraulic cylinder, which is installed on the housing bushing. The oil inlets of all axial force loading hydraulic cylinders are connected in series by pipelines, and the oil return ports are connected in series by pipelines. The radial force loading hydraulic cylinder is a double-rod hydraulic cylinder that acts on the radial force loading bearing seat.

[0043] The force-adding rod has a threaded structure at both ends, with one end connected to the hydraulic cylinder rod and the other end connected to the force sensor; the thrust pad has a threaded structure at one end connected to the force sensor, and a spherical surface at the other end that contacts the thrust bearing seat to transmit axial and radial forces.

[0044] like Figure 1 As shown, the axial force loading bearing housing 13 and the radial force loading bearing housing 14 of the present invention are disposed in the middle of the transmission shaft 6. The axial force loading bearing housing 13 is composed of two ball bearings that bear thrust, which are interference-fitted onto the transmission shaft 6 through an inner ring bushing 12. The shaft end is axially locked by the test bearing locking nut 16. The end face of the axial force loading bearing housing 13 is the working surface, and the thrust pad 11 acts on the end face of the bearing housing to transmit the axial force. The radial force loading bearing housing 14 is composed of two cylindrical roller bearings that are interference-fitted onto the transmission shaft 6. The shaft end is axially locked by the test bearing locking nut 16. A flat surface is machined on the outer circle of the bearing housing as the working surface, which contacts the thrust pad 11. The radial hydraulic loading force is transmitted to the radial bearing housing through the thrust pad 11. When axial force and radial force are applied to the test bearing 4, the cylindrical roller bearings in the radial force loading bearing housing will move axially, so that the radial force loading cylinder will not generate tangential force, and thus the hydraulic cylinder will not jam.

[0045] The axial force loading section, by controlling the pressure of the inlet and outlet oil chambers in the hydraulic cylinder, can achieve a wide range of loading forces with high loading accuracy. The head of the hydraulic cylinder 8 has an external thread structure and is threadedly connected to the force-applying rod 9; one end of the force-applying rod 9 has an internal thread and the other end has an external thread, and both ends are connected to the hydraulic cylinder 8 and the force sensor 10 respectively. One end of the thrust pad 11 has a threaded structure and is connected to the sensor 10, while the other end has a spherical structure that axially contacts the thrust bearing seat 13 to jointly transmit the axial force; the axial force is applied to the transmission shaft 6 through the axial force loading bearing seat 13, thereby transmitting it to the inner ring of the test bearing 4;

[0046] The axial force loading hydraulic cylinder 8 is a low-friction double-rod servo hydraulic cylinder, which is inserted into several holes on the distribution circle of the housing bushing 2. It is connected to the housing bushing 2 by bolts on the flange face of the hydraulic cylinder and tightened. The tightening bolts bear the reaction force generated by the load. All the oil inlets of the hydraulic cylinders are connected in series by pipelines to ensure that the pressure at the inlet end of all hydraulic cylinders is consistent. All the oil outlets of the hydraulic cylinders are connected in series by pipelines to ensure that the pressure at the outlet end of all hydraulic cylinders is consistent.

[0047] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A bearing tester comprising a housing (1), characterised in that: It also includes two housing bushings (2), a drive shaft (6), a transmission assembly, an axial force loading bearing housing (13), an axial force loading unit, an axial force bearing bushing (12), an axial force test bearing locking nut (16), a radial force loading bearing housing (14), a radial force locking nut (15), and a radial force loading unit; Two housing bushings (2) are installed on the left and right sides of the housing (1) respectively. The drive shaft (6) is rotatably installed on the two housing bushings (2) through the transmission assembly. The test bearing (4) in the transmission assembly is fitted onto the drive shaft (6) through the test bearing bushing (5). An axial force bearing bushing (12) is fitted onto a drive shaft (6). One end of the axial force bearing bushing (12) is positioned by a shoulder on the drive shaft (6), and the other end is positioned by an axial force test bearing locking nut (16) screwed onto the drive shaft (6). An axial force loading bearing housing (13) is fitted onto the axial force bearing bushing (12), and an axial force bearing is fitted between the axial force bearing bushing (12) and the axial force loading bearing housing (13). The axial force loading unit is connected to the axial force bearing bushing (12) and applies axial force to the axial force bearing. The axial force is applied to the drive shaft (6) through the axial force loading bearing housing (13) and transmitted to the inner ring of the test bearing (4). A set of radial force bearings is mounted on the drive shaft (6), and one end of the radial force bearing is positioned by the shoulder of the drive shaft (6), and the other end of the radial force bearing is positioned by the radial force locking nut (15) screwed on the drive shaft (6). The radial force loading bearing seat (14) is mounted on the radial force bearing. The radial force loading unit passes vertically through the housing (1) and is connected to the radial force loading bearing seat (14) and applies radial force to the radial force bearing. When axial force and radial force are applied to the test bearing (4), the radial force bearing in the radial force loading bearing housing (14) will move axially, so that the radial force loading cylinder will not generate tangential force, and thus the hydraulic cylinder will not jam. The axial force loading unit includes multiple sets of thrust components. The multiple sets of thrust components pass through the housing (1) in a ring array along the axis of the transmission shaft (6) and are connected to the axial force loading bearing seat (13). Each thrust assembly includes an axial thrust pad (11), an axial force sensor (10), an axial force rod (9), and an axial servo hydraulic cylinder (8), which are connected sequentially from left to right.

2. The bearing testing apparatus according to claim 1, characterized in that: The transmission assembly includes a test bearing mounting base (3), a test bearing bushing (5), and a test bearing locking nut (16). The test bearing bushing (5) is mounted on the transmission shaft (6) and is positioned by a shoulder on the transmission shaft (6). The test bearing (4) is mounted on the test bearing bushing (5). The test bearing locking nut (16) is screwed onto the transmission shaft (6) and limits the position of the test bearing bushing (5). The test bearing mounting base (3) is mounted on the test bearing (4).

3. The bearing testing apparatus according to claim 2, characterized in that: One of the housing bushings (2) has a lubrication return oil passage.

4. A bearing tester according to claim 3, wherein: One end of the axial force-adding rod (9) is provided with an internal thread and is connected to the axial servo hydraulic cylinder (8). The other end of the axial force-adding rod (9) is provided with an external thread and is connected to the axial force sensor (10).

5. A bearing tester according to claim 4, wherein: The external thread end of the axial thrust pad (11) is connected to the external thread section of the axial force rod (9) and the internal threads at both ends of the sensor (10).

6. A bearing testing apparatus according to claim 5, characterized in that: The radial force loading unit includes a radial force thrust pad (17), a radial force sensor (18), a radial force lever (19), and a radial servo hydraulic cylinder (20). The radial servo hydraulic cylinder (20), the radial force lever (19), the radial force sensor (18), and the radial force thrust pad (17) are connected sequentially from top to bottom.

7. A bearing testing apparatus according to claim 6, characterized in that: Both the axial servo hydraulic cylinder (8) and the radial servo hydraulic cylinder (20) are low-friction double-rod servo hydraulic cylinders.

8. A bearing tester according to claim 1, wherein: The test bearing (4) and the test bearing bush (5) are interference fit.

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