A device for electroerosion testing of rolling bearings

Abstract

The application discloses a device for rolling bearing electric erosion test, comprising a rack, a sleeve fixed on the rack along the vertical direction, a main shaft axially rotatable along the sleeve axis, a back nut, an upper supporting bearing, an annular sliding block, a test bearing, a test sliding seat, an annular force sensor, a compression spring and a lower supporting bearing sequentially sleeved along the main shaft from top to bottom; the rack is further provided with an electric signal measurement unit, and the electric signal measurement unit forms an electric erosion detection closed loop with the test bearing and the main shaft. The device uses a thrust ball bearing as the test bearing, is easy to disassemble and assemble, can be stopped at any time during the test, and can be disassembled to observe, analyze and measure the electric erosion of the raceway and the steel ball, so that the electric erosion mechanism of the bearing can be studied; the electric erosion parameters of the bearing under different rotating speeds, loads, temperatures and current intensities can be tested, short-time test under a single parameter can be carried out, the data acquisition rate is greatly improved, and the test results are convenient for analysis.

Description

Technical Field

[0001] This invention belongs to the technical field of bearing testing equipment, specifically relating to a device for testing the electrical erosion of rolling bearings. Background Technology

[0002] Rolling bearings are commonly used components in machinery and equipment. Generally, rolling bearings suffer from three main types of damage: force damage, thermal damage, and electrical damage. For motor bearings, electrical damage, specifically bearing electro-erosion (EEC), is the primary form. ECC refers to the phenomenon where current flowing through the contact area between the inner and outer raceways and rolling elements of a rotating bearing breaks down the lubricating oil film, causing spark discharge and resulting in damage to the metal surface. Grease forms a lubricating oil film between the inner and outer rings and rolling elements of the bearing. This film is typically very thin (0.1 to 1 micrometer). When a current is generated and exceeds the threshold voltage of the oil film, the bearing current breaks down the oil film, leading to damage to the surfaces of the rolling elements and raceways. This damage is characterized by streaks called ridges or pits with localized melting, causing vibration and noise, and reducing the bearing's lifespan. Furthermore, it also leads to grease deterioration. Therefore, research on bearing ECC has become indispensable.

[0003] Electrolytic corrosion of rolling bearings in electric motors has been a known phenomenon for a long time, but it has not received sufficient attention. In recent years, due to the rapid development of electric vehicles, especially with the increasing use of frequency converters for continuous speed control of motors in modern power transmission systems, the problem of bearing electrolytic corrosion will become increasingly prominent in the future. Moreover, the trend of using higher voltages in electric vehicle power systems will lead to higher energy discharge. With the popularization of variable frequency speed control technology, bearing electrolytic corrosion will occur more frequently.

[0004] Studies on motor reliability show that 40% of motor failures are due to bearing damage, and 25% of these bearing failures are caused by the PWM inverter. v / d t This is caused by the fact that the number of motor bearings damaged by PWM inverter power supply is increasing at an alarming rate with the widespread use of high-performance devices such as IGBTs, making it a hot research topic both domestically and internationally. Research indicates that the damage to motor bearings under PWM inverter power supply is due to the generation of so-called "shaft voltage" and "bearing current." The motor's shaft voltage is the voltage value from the rotor shaft to the stator, and the current generated by this voltage through the bearing forms the bearing current.

[0005] Most existing equipment for simulating bearing current is used to study bearing durability tests under conductive conditions. However, research on the electro-erosion mechanism of bearings, the influence of different current densities on the electro-erosion damage process of bearings, and the degradation of lubricating grease performance is still relatively limited. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention proposes a novel device for testing and studying the electrical erosion characteristics of rolling bearings. To achieve the above-mentioned technical objectives, the technical solution adopted by this invention is as follows: An apparatus for testing the electrical erosion of rolling bearings includes a frame, on which a cylindrical sleeve is fixed vertically. An axially rotatable main shaft is positioned along the sleeve's axis. Along the main shaft, from top to bottom, are sequentially fitted a backing nut, an upper support bearing, an annular slider, a bearing under test, a test slide, an annular force sensor, a compression spring, and a lower support bearing. The outer diameter of the backing nut is threaded into the inner wall of the sleeve, and the inner wall of the backing nut does not contact the surface of the main shaft. The upper support bearing and the test slide can slide up and down along the inner wall of the sleeve, and the annular slider can slide up and down along the main shaft and rotate synchronously with it. The lower support bearing is fixedly mounted on the frame and supports the main shaft. The test slide is supported by a compression spring whose lower end presses against the frame. An annular metal plate is located on the upper surface of the test slide. The bearing under test is a thrust ball bearing, and its lower surface presses against the annular metal plate. An electrical signal measurement unit is also located on the frame. This unit includes a DC power supply. A conductive carbon brush is located at the upper end of the sleeve and contacts the surface of the spindle. The electrical signal measurement unit is connected to the annular metal plate and the conductive carbon brush via wires. The DC current output by the electrical signal measurement unit passes through the annular metal plate, the bearing under test, the spindle, and the conductive carbon brush, and returns to the electrical signal measurement unit, forming a series closed loop. An adjustable resistor is provided on the loop circuit.

[0007] Preferably, the spindle is driven to rotate by a motor mounted on the frame via a multi-ribbed belt.

[0008] Preferably, the bearing under test has a separable structure, including a shaft ring, a housing ring, steel balls and a cage. The inner diameter of the shaft ring is in contact with the surface of the main shaft, while the inner diameter of the housing ring is not in contact with the surface of the main shaft. The lower surface of the housing ring is pressed against an annular metal plate.

[0009] Preferably, a temperature sensor is provided on the test slide, and the temperature sensor probe is in contact with the seat ring.

[0010] Furthermore, a miniature air pump is installed on the sleeve.

[0011] Preferably, a spline is provided between the spindle surface and the inner diameter of the annular slider in the vertical direction to cooperate with each other.

[0012] Preferably, a first bearing seat is provided between the upper support bearing and the inner wall of the sleeve, and the first bearing seat is made of insulating material.

[0013] Furthermore, the outer circumferential surface of the first bearing housing is provided with a vertical groove and is fixed by a set screw with a pin passing through the sleeve.

[0014] Preferably, the outer circumferential surface of the test slide is provided with a vertical groove and is fixed by a set screw with a pin passing through the sleeve, and the bottom of the test slide is provided with an oil seal.

[0015] Preferably, the lower support bearing is fixedly mounted on the frame via a second bearing seat, and a stepped portion supporting the lower support bearing is provided near the lower end of the main shaft. The lower section of the main shaft mates with the inner ring of the lower support bearing, and an insulating sleeve is provided between the outer circumferential surface of the lower support bearing and the second bearing seat.

[0016] Compared with the prior art, the beneficial effects of this invention are as follows: This device uses a thrust ball bearing as the test bearing, which is easy to disassemble and assemble. It can monitor the changes in bearing voltage in real time. The test load, current or voltage can be set before the test begins. The test can be stopped at any time during the test. The bearing can be disassembled to observe, analyze and measure the electro-erosion of the groove and steel balls. Disassembly will not damage the bearing. The test can be continued after reassembly. It is convenient to observe the bearing electro-erosion process during the test and study the bearing electro-erosion mechanism. The electro-erosion parameters of the bearing can be tested separately under different speeds, loads, temperatures and current intensities, which is convenient for the failure analysis of grease. Short-term tests can be performed under a single parameter, such as a few minutes to a few hours, and the changes in electrical signals during the test can be recorded with a high data acquisition rate, which is convenient for the analysis of test results. Attached Figure Description

[0017] Figure 1 : A schematic cross-sectional view of the present invention.

[0018] Figure 2 : A side view of the structure of the present invention.

[0019] Figure 3 : A cross-sectional view of the upper part of the present invention.

[0020] Figure 4 : A cross-sectional view of the lower half of the present invention.

[0021] Figure 5 : A three-dimensional structural diagram of the annular slider and the main shaft in this invention.

[0022] Figure 6 : A cross-sectional view of the bearing under test in this invention.

[0023] In each of the following diagrams: 1. Frame; 101. Motor; 102. Multi-ribbed belt; 2. Sleeve; 21. Miniature air pump; 3. Spindle; 4. Back tightening nut; 5. Upper support bearing; 51. First bearing housing; 6. Annular slider; 7. Bearing under test; 71. Shaft ring; 72. Seat ring; 73. Steel ball; 74. Cage; 8. Test slide; 81. Annular metal plate; 82. Oil seal; 83. Temperature sensor; 9. Annular force sensor; 10. Compression spring; 11. Lower support bearing; 111. Second bearing housing; 112. Insulating sleeve; 12. Electrical signal measurement unit; 121. DC power supply; 122. Conductive carbon brush; 123. Adjustable resistor. Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Terms such as "upper," "lower," "left," "right," and "middle" used in this specification are only for clarity of description and are not intended to limit the scope of the present invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] An apparatus for testing the electrical erosion of rolling bearings, referring to... Figures 1 to 4 As shown, the device includes a frame 1, on which a cylindrical sleeve 2 is fixed vertically. An axially rotatable main shaft 3 is mounted along the axis of the sleeve 2. The rotation of the main shaft 3 is driven by a motor 101 mounted on the frame 1 via a multi-wedge belt 102. Along the main shaft 3, from top to bottom, are sequentially mounted a back-tightening nut 4, an upper support bearing 5, an annular slider 6, a test bearing 7, a test slide 8, an annular force sensor 9, a compression spring 10, and a lower support bearing 11. The outer diameter of the back-tightening nut 4 is threaded into the inner wall of the sleeve 2, and the inner wall of the back-tightening nut 4 does not contact the surface of the main shaft 3. The upper support bearing 5 and the test slide 8 can slide up and down along the inner wall of the sleeve 2. The annular slider 6 can slide up and down along the main shaft 3 and rotates synchronously with the main shaft 3. In one specific structure, refer to... Figure 5As shown, a spline is provided vertically between the surface of the main shaft 3 and the inner diameter of the annular slider 6. The lower support bearing 11 is fixedly mounted on the frame 1 and supports the main shaft 3, and the lower end of the compression spring 10 presses against the frame 1. In one specific structure, the main shaft 3 has a stepped portion near its lower end, and the portion below the stepped portion mates with the inner ring of the lower support bearing 11. The stepped surface supports the lower support bearing 11, and the lower support bearing 11 limits the downward movement of the main shaft 3. The upper support bearing 5 and the lower support bearing 11 work together to limit the axial movement of the main shaft 3, ensuring that the main shaft 3 remains stable axially when rotating. The upper end face of the test slide 8 is provided with an annular metal plate 81, and the test bearing 7 is a thrust ball bearing. The lower surface of the test bearing 7 presses against the annular metal plate 81. Specifically, the test bearing 7 has a separable structure, as shown in the reference. Figure 6 As shown, the test bearing 7 includes a shaft ring 71, a seat ring 72, steel balls 73, and a cage 74. The inner diameter of the shaft ring 71 is in contact with the surface of the spindle 3, while the inner diameter of the seat ring 72 is not in contact with the surface of the spindle 3. The lower surface of the seat ring 72 is in contact with the annular metal plate 81. An electrical signal measurement unit 12 is also provided on the frame 1. The electrical signal measurement unit 12 includes a DC power supply 121. A conductive carbon brush 122 is provided at the upper end of the sleeve 2, which is in contact with the surface of the spindle 3. The electrical signal measurement unit 12 is connected to the annular metal plate 81 and the conductive carbon brush 122 respectively via wires. The DC current output by the electrical signal measurement unit 12 passes through the annular metal plate 81, the test bearing 7, the spindle 3, and the conductive carbon brush 122, and returns to the electrical signal measurement unit 12, forming a series closed loop. An adjustable resistor 123 is provided on the loop circuit. The output electrical signal can be set through the DC power supply 121, and the loop electrical signal can be adjusted through the adjustable resistor 123, thereby simulating the current and voltage conditions of the bearing more flexibly. The electrical signal measurement unit 12, DC power supply 121 and adjustable resistor 123 used in this device are all common instruments and equipment, so they will not be described in detail.

[0026] The working process and principle of the device are as follows: First, enter the adjustment state, install the main shaft 3 on the frame 1 through the lower support bearing 11, and ensure the upper end of the main shaft 3 is insulated. Install the compression spring 10 and the annular force sensor 9 on the main shaft 3 in sequence. Install the test bearing 7 on the test slide 8 with the annular metal plate 81 as a pad. Then, install the test slide 8 and the test bearing 7 on the main shaft 3. Connect the terminals and wires to the annular metal plate 81 in advance. Then, install the annular slider 6 and the upper support bearing 5 on the main shaft 3 in sequence. At this point, the main shaft unit is installed. Then, use the sleeve 2 to cover and fix the main shaft unit on the frame 1. The upper support bearing 5 and the test slide 8 cooperate with the inner wall of the sleeve 3 and can slide up and down along the inner wall of the sleeve 3. In a preferred embodiment, refer to Figure 3As shown, a first bearing seat 51 made of insulating material is provided between the upper support bearing 5 and the inner wall of the sleeve 2. The outer circumferential surface of the first bearing seat 51 has a vertical groove and is fixed by a set screw with a pin passing through the sleeve 2. The outer circumferential surface of the test slide 8 also has a vertical groove and is fixed by a set screw with a pin passing through the sleeve 2. When the upper support bearing 5 and the test slide 8 are installed on the main shaft 3, the angle is adjusted so that the vertical groove corresponds to the position of the set screw. After the sleeve 2 is installed, the upper support bearing 5 and the test slide 8 can slide up and down along the inner wall of the sleeve 2, but will not rotate in the circumferential direction. To prevent grease leakage and contamination in the test bearing 7, an oil seal 82 can be provided at the bottom of the test slide 8. A vertical opening is provided on one side of the sleeve 2 for the lead-out of the wire connected to the annular metal plate 81. A back-tightening nut 4 is installed above the main shaft 3, and the conductive carbon brush 122 and the wire are connected. After installing sleeve 2, connect the wires connected to the annular metal plate 81 and conductive carbon brush 122 to the output and input terminals of the electrical signal measurement unit 12, respectively, and connect the adjustable resistor 123 in series with the wires. After adjusting the electrical signal measurement unit 12 and the adjustable resistor 123 to the test state, rotate the back tightening nut 4 downward. The load on the test bearing 7 is applied by the back tightening nut 4 in conjunction with the compression spring 10. When rotating the back tightening nut 4 downward, pressure is applied to the annular slider 6 on the main shaft 3 via a spline engagement. The pressure is transmitted to the test bearing 7 through the annular slider 6, and the test bearing 7 is pressed against the test slide 8. The test slide 8 transmits the load downward to the annular force sensor 9, and the applied load is buffered by the compression spring 10 below. Observe the change of pressure value on the display screen connected to the annular force sensor 9 to achieve the purpose of applying a predetermined load to the test bearing 7. When the switch of the electrical signal measurement unit 12 is turned on, an electrical signal is emitted from the DC power supply 121, passing through the annular metal plate 81, the seat ring 72 of the test bearing 7, the steel ball 73, the shaft ring 71, the main shaft 3, the conductive carbon brush 122, and the adjustable resistor 123 before returning to the electrical signal measurement unit 12, forming a closed loop. Simultaneously, the main shaft 3 begins to rotate under the drive of the motor 101, and the rotational speed can be displayed and controlled in real time through the controller connected to the motor 101. The test bearing 7 is placed under the annular slider 6. During the experiment, a downward force along the axial direction of the main shaft 3 is applied by tightening the nut 4, causing the annular slider 6 to make close contact with the shaft ring 71 of the test bearing 7. Utilizing the friction between them, when the main shaft 3 drives the annular slider 6 to rotate synchronously, the annular slider 6 drives the shaft ring 71 of the test bearing 7 to rotate. At the same time, the seat ring 72 is pressed against the annular metal plate 81. The test slide 8 is limited by the pin-set screw and can only move up and down without rotation. Therefore, the rotational speed of the main shaft 3 is the relative rotational speed between the shaft ring 71 and the seat ring 72 of the test bearing 7. During the test, the changes in the signal are observed at any time. When a characteristic electrical signal related to bearing erosion is detected, the test can be paused at any time, the test bearing 7 can be removed, and the surface condition of the grooves and steel balls 73 of the test bearing 7, as well as the condition of the grease, can be observed. Then, the bearing can be reassembled and the test can continue.

[0027] In a preferred embodiment, a temperature sensor 83 is provided on the test slide 8. The probe of the temperature sensor 83 is in contact with the bearing race 72 and is used to monitor the temperature of the bearing under test 7. A miniature air pump 21 is provided on the sleeve 2 to cool down the bearing through air circulation, thereby achieving the purpose of controlling and regulating the test environment temperature inside the sleeve 2.

[0028] To better ensure the closure of the electro-erosion test circuit and prevent current leakage from the sleeve 2 and the frame 1, the device features a reasonable insulation design. The spindle 3 is driven to rotate by the multi-wedge belt 102, which effectively eliminates electrical conduction between the spindle 3 and the frame 1. The inner diameter of the tightening nut 4 does not contact the surface of the spindle 3. The first bearing seat 51 between the upper support bearing 5 and the sleeve 2 is made of insulating material. The inner diameter of the bearing ring 71 of the test bearing 7 contacts the surface of the spindle 3, while the inner diameter of the seat ring 72 does not contact the surface of the spindle 3. The test slide 8 is made of insulating material, and the seat ring 72 is connected to the external circuit through the annular metal plate 81 on the test slide 8. The lower support bearing 11 is fixedly mounted on the frame 1 through the second bearing seat 111, and an insulating sleeve 112 is provided between the outer circumferential surface of the lower support bearing 11 and the second bearing seat 111.

[0029] Compared to existing technologies, this device uses a thrust ball bearing as the test bearing 7, which is easy to disassemble and assemble. It can monitor the changes in bearing voltage in real time. The test load, current, or voltage can be set before the test begins. The test can be stopped at any time during the test, and the bearing can be disassembled to observe, analyze, and measure the electro-erosion of the raceway and steel balls. Disassembly will not damage the bearing, and the test can continue after reassembly. This facilitates observation of the bearing electro-erosion process during the test and the study of the bearing electro-erosion mechanism. The device can test the bearing electro-erosion parameters under different speeds, loads, temperatures, and current intensities, which is convenient for the failure analysis of grease. It can perform short-term tests under a single parameter, such as from a few minutes to a few hours, and record the changes in electrical signals during the test process with a high data acquisition rate, which is convenient for the analysis of test results.

[0030] In summary, the device for testing the electrical erosion of rolling bearings provided by this invention effectively solves the problems of the lack of means to detect the electrical erosion characteristics of bearings under different current, load, speed, temperature and other conditions and the low rate of test data acquisition in the prior art. It has high utilization value and application significance and can be widely promoted and applied.

[0031] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An apparatus for testing the electrical erosion of rolling bearings, comprising a frame (1), characterized in that: A cylindrical sleeve (2) is fixed vertically on the frame (1). A rotatable main shaft (3) is provided along the axis of the sleeve (2). A back-tightening nut (4), an upper support bearing (5), an annular slider (6), a test bearing (7), a test slide (8), an annular force sensor (9), a compression spring (10), and a lower support bearing (11) are sequentially mounted on the main shaft (3) from top to bottom. The outer diameter of the back-tightening nut (4) is threaded to the inner wall of the sleeve (2), and the inner wall of the back-tightening nut (4) does not contact the surface of the main shaft (3). The support bearing (5) and the test slide (8) can slide up and down along the inner wall of the sleeve (2), the annular slider (6) can slide up and down along the main shaft (3) and rotate synchronously with the main shaft (3); the lower support bearing (11) is fixedly installed on the frame (1) and supports the main shaft (3); the lower end of the compression spring (10) presses on the frame (1); the upper end face of the test slide (8) is provided with an annular metal plate (81), the test bearing (7) is a thrust ball bearing, and the lower surface of the test bearing (7) presses on the annular metal plate (81); The frame (1) is also provided with an electrical signal measurement unit (12), which includes a DC power supply (121). The upper end of the sleeve (2) is provided with a conductive carbon brush (122) that contacts the surface of the spindle (3). The electrical signal measurement unit (12) is connected to the annular metal plate (81) and the conductive carbon brush (122) respectively through wires. The DC current output by the electrical signal measurement unit (12) passes through the annular metal plate (81), the test bearing (7), the spindle (3) and the conductive carbon brush (122) and returns to the electrical signal measurement unit (12) to form a series closed loop. An adjustable resistor (123) is provided on the loop line.

2. The apparatus for testing the electrical erosion of rolling bearings as described in claim 1, characterized in that: The spindle (3) is driven to rotate by a motor (101) mounted on the frame (1) via a multi-ribbed belt (102).

3. The apparatus for testing the electrical erosion of rolling bearings as described in claim 1, characterized in that: The test bearing (7) is a separable structure, including a shaft ring (71), a seat ring (72), a steel ball (73) and a cage (74). The inner diameter of the shaft ring (71) is in contact with the surface of the main shaft (3), while the inner diameter of the seat ring (72) is not in contact with the surface of the main shaft (3). The lower surface of the seat ring (72) is pressed on the annular metal plate (81).

4. The apparatus for testing the electrical erosion of rolling bearings as described in claim 3, characterized in that: The test slide (8) is equipped with a temperature sensor (83), and the probe of the temperature sensor (83) is in contact with the seat ring (72).

5. The apparatus for testing the electrical erosion of rolling bearings as described in claim 4, characterized in that: The sleeve (2) is equipped with a miniature air pump (21).

6. The apparatus for testing the electrical erosion of rolling bearings as described in claim 1, characterized in that: The surface of the main shaft (3) and the inner diameter of the annular slider (6) are provided with mutually mating splines in the vertical direction.

7. The apparatus for testing the electrical erosion of rolling bearings as described in claim 1, characterized in that: A first bearing seat (51) is provided between the upper support bearing (5) and the inner wall of the sleeve (2), and the first bearing seat (51) is made of insulating material.

8. The apparatus for testing the electrical erosion of rolling bearings as described in claim 7, characterized in that: The outer circumferential surface of the first bearing seat (51) is provided with a vertical groove and is fixed by a set screw with a pin passing through the sleeve (2).

9. The apparatus for testing the electrical erosion of rolling bearings as described in claim 1, characterized in that: The test slide (8) has a vertical groove on its outer circumference and is fixed by a pin-type set screw that passes through the sleeve (2). The bottom of the test slide (8) is provided with an oil seal (82).

10. The apparatus for testing the electrical erosion of rolling bearings as described in claim 1, characterized in that: The lower support bearing (11) is fixedly mounted on the frame (1) via the second bearing seat (111). The main shaft (3) has a stepped portion near its lower end that supports the lower support bearing (11). The lower section of the main shaft (3) is engaged with the inner ring of the lower support bearing (11). An insulating sleeve (112) is provided between the outer circumferential surface of the lower support bearing (11) and the second bearing seat (111).

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