CN113533858A - Oil film conductivity test bed for ball disc type grease lubrication ball bearing and test method thereof - Google Patents
Oil film conductivity test bed for ball disc type grease lubrication ball bearing and test method thereof Download PDFInfo
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- CN113533858A CN113533858A CN202110721117.9A CN202110721117A CN113533858A CN 113533858 A CN113533858 A CN 113533858A CN 202110721117 A CN202110721117 A CN 202110721117A CN 113533858 A CN113533858 A CN 113533858A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/22—Measuring resistance of fluids
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R1/00—Details of instruments or arrangements of the types included in groups G01R5/00 - G01R13/00 and G01R31/00
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Abstract
The invention discloses a ball disc type grease lubrication ball bearing oil film conductivity test bed and a test method thereof. The test bed comprises a driving mechanism, a loading module, a ball cover mechanism and a ball disc testing module; the ball disc testing module simulates the working condition of a grease lubrication ball bearing, the loading module loads the load of the ball cover mechanism, and the driving mechanism drives the ball disc testing module. The conductivity of the lubricating grease oil film is measured by introducing the resistivity of the oil film, so that the conductivity of the bearing lubricating grease is detected in real time; the oil film resistivity calculation principle of the lubricating grease oil film is as follows: under the condition of a certain rotating speed and a certain load of the steel ball, an oil film with a certain thickness is generated due to the dynamic pressure lubrication of the elastic fluid, the resistance of the oil film part is calculated by measuring the breakdown voltage and the current under the condition, and the resistivity of the oil film is the ratio of the resistance of the oil film part to the minimum thickness of the oil film.
Description
Technical Field
The invention belongs to the technical field of testing, and particularly relates to a ball disc type grease lubrication ball bearing test bed and a test method thereof.
Background
The rolling bearing is the most widely applied core component in the rotary machine, is an indispensable key component in various fields of aviation, heavy industry, advanced manufacturing equipment and the like, and is also an object which needs to pay attention and research in China manufacturing 2025 and is provided for the current situation that the core basic components (components), advanced basic processes, key basic materials, industrial technical foundations and other industrial basic capabilities of China are weak. The performance and the service life of the rolling bearing are improved, and the rolling bearing has great significance for the development of the mechanical industry and other related industries in China.
The electric erosion is a common failure mode of the rolling bearing, and means that when current flows in a contact part of a bearing raceway and a rolling body in rotation, sparks are emitted through a thin lubricating oil film, and local melting and concave-convex phenomena occur on the surface of the electric erosion. Such failure forms are frequently generated in motor bearings, wheel-rail bearings of subway trains, and the like. At present, in order to overcome the influence of bearing electric corrosion, an insulation method is generally adopted, for example, a ceramic ball bearing is adopted to insulate an inner ring and an outer ring of a bearing, but the bearing capacity and the material strength of the bearing are far lower than those of the bearing made of traditional GGr15 steel, for example, an insulation coating film coating method is adopted to treat a bearing raceway and a rolling body, but the insulation problem of the bearing with long service life and high reliability cannot be solved due to the peeling and friction consumption of a coating layer.
In recent years, the change of the conductivity of the bearing by means of grease is a new research direction. In order to research the influence of the lubricating grease with different components and additives on the conductivity of the rolling bearing and accurately simulate the insulating and conducting characteristics of the lubricating grease in a bearing rolling element/raceway contact mode in real time, a series of performance test benches and test methods aiming at the conductivity of the lubricating grease are urgently needed.
Disclosure of Invention
The invention provides a ball disc type grease lubrication ball bearing oil film conductivity test bed and a test method thereof aiming at the problem that the current lubricating grease conductivity test method can not accurately react the actual conductivity of a grease lubrication rolling ball bearing in operation, wherein a ball disc test module is used for simulating the working condition of a grease lubrication ball bearing, and the conductivity of a lubricating grease oil film is measured by introducing oil film resistivity, so that the real-time detection of the conductivity of the bearing lubricating grease is realized; the oil film resistivity calculation principle of the lubricating grease oil film is as follows: under the condition of a certain rotating speed and a certain load of the steel ball, an oil film with a certain thickness is generated due to the dynamic pressure lubrication of the elastic fluid, the resistance of the oil film part is calculated by measuring the breakdown voltage and the current under the condition, and the resistivity of the oil film is the ratio of the resistance of the oil film part to the minimum thickness of the oil film.
The invention relates to a ball disc type grease lubrication ball bearing oil film conductivity test bed, which comprises a driving mechanism, a loading module, a ball cover mechanism and a ball disc test module; the loading module comprises a load adjusting nut, a loading spring, a pressure sensor and a threaded rod; the threaded rod is vertically arranged and forms a sliding pair with the test bed rack; the top of the threaded rod is provided with a limiting convex ring which is limited by the test bed rack; the loading spring is sleeved on the threaded rod; the load adjusting nut and the threaded rod form a screw pair, and two ends of the loading spring are respectively contacted with the load adjusting nut and the test bed rack; and the central threaded hole of the pressure sensor is connected with the threaded rod.
The ball cover mechanism comprises a sleeve, a ball cover and a ball clamping box; the sleeve is fixed on the test bed rack; a pressure sensor of the loading module and the top hole section of the central hole of the sleeve form a sliding pair; the bottom of the threaded rod penetrates through a central threaded hole of the pressure sensor and is connected with a central threaded hole of the ball box cover; the ball box cover is arranged in the sleeve; the ball clamping box is fixed at the bottom end of the ball box cover; the bottom of the ball clamping box is provided with a hemispherical notch, and the center of the bottom of the hemispherical notch is provided with a vertically arranged slit; the outer side wall of the ball clamping box is provided with a conical surface and is matched with a conical hole section at the bottom of the central hole of the sleeve.
The ball disc testing module comprises a testing steel ball, a conductive slip ring main shaft, a rolling bearing, a bakelite plate, a disc, a fastening nut, a voltage-stabilized power supply, a voltage sensor and a current sensor; the test steel ball is embedded into the hemispherical notch of the ball clamping box; the outer ring of the conductive slip ring is fixed on the test bed rack; the main shaft of the conductive slip ring is fixed with the inner ring of the conductive slip ring and is driven by a driving mechanism; the bakelite plate is supported on a main shaft of the conductive slip ring through a rolling bearing; the disc is sleeved on the main shaft of the conductive slip ring and is positioned above the bakelite plate; the bottom surface of the disc is axially limited by a shaft shoulder of the main shaft of the conductive slip ring; the fastening nut is connected with the external thread on the top of the main shaft of the conductive slip ring and compresses the top surface of the disc; the fastening nut is made of insulating materials; the stabilized voltage power supply is connected with a lead interface of the outer ring of the conductive slip ring through a lead, a lead interface of the inner ring of the conductive slip ring is connected with a main shaft of the conductive slip ring through a lead, the main shaft of the conductive slip ring is connected with the disc through a lead, a raceway on the top surface of the disc is contacted with a test steel ball, and the ball clamping box is connected with the stabilized voltage power supply through a lead to form a closed passage; the voltage sensor measures the voltage of the voltage-stabilized power supply, the current sensor measures the current of the closed circuit, and the signal output ends of the voltage sensor and the current sensor are connected with the data acquisition card.
Preferably, the test bed rack comprises a test bed base and a test bed support; the test bed support consists of a vertical support, a transverse support and a baffle; the four vertical supports are arranged in an array and fixed on the base of the test bed, and every two adjacent vertical supports are fixed through a transverse support; the baffle is fixed with the tops of the four vertical supports. The threaded rod and the baffle form a sliding pair; the conductive slip ring is fixed with the vertical support.
Preferably, the driving mechanism comprises a stepping motor and a flexible coupling; the shell of the stepping motor is fixed on the test bed rack, and the output shaft of the stepping motor is connected with the conductive slip ring main shaft through a flexible coupling; the flexible coupling is made of insulating materials; the stepping motor is controlled by the control module.
More preferably, the control module comprises a main control chip, a stepping motor driver, an air switch and a switching power supply; the switch power supply is connected with alternating current through the air switch and converts the alternating current into direct current to supply power for the stepping motor driver and the stepping motor; the main control chip is connected with the stepping motor through the stepping motor driver and controls the rotation angle, the rotation direction and the enabling of the stepping motor.
Preferably, the radius of the test steel ball is calculated by the equivalent formula:
wherein R is1Radius of inner ring raceway of the measured bearing, r radius of ball of the measured bearing, D diameter of ball of the measured bearing, DmIs the pitch circle diameter of the measured bearing.
The method for testing the conductivity of the grease lubricating oil film by using the ball disc type grease lubricating ball bearing test bed comprises the following specific steps:
taking the test steel ball down from the ball clamping box, and cleaning the test steel ball, the hemispherical notch of the ball clamping box and the top surface of the disc by using petroleum ether so that no lubricating grease is left on the test steel ball, the hemispherical notch of the ball clamping box and the top surface of the disc; the test ball is then inserted into the hemispherical pocket of the cartridge and contacts the raceway on the top surface of the disk.
Secondly, applying force to the loading spring through the load adjusting nut, changing the elongation of the loading spring, and enabling the loading spring to apply load to the load adjusting nut downwards, so that the load adjusting nut drives the threaded rod to apply load to the pressure sensor and the ball box cover, and the load of the ball box cover is applied to the test steel ball and the disc through the ball clamping box; the pressure sensor detects the magnitude of the load Q applied by the threaded rod.
Step three, regulating the voltage of the stabilized voltage supply, starting the stabilized voltage supply, and measuring the voltage of the stabilized voltage supply to be U by the voltage sensor0The current sensor measures the current of the closed path as I0Calculating the total resistance R of the closed path according to ohm's lawi＝U0/I0。
And step four, closing the stabilized voltage supply, rotating the load adjusting nut, and removing the load applied to the test steel ball and the disc.
And step five, coating lubricating grease in the raceway of the disc and on the test steel ball, then rotating the load adjusting nut, and applying a load Q to the test steel ball and the disc again to enable the test steel ball to be in contact with the raceway on the top surface of the disc.
And step six, the driving mechanism drives the conductive slip ring main shaft to rotate, and the conductive slip ring main shaft drives the disc to rotate at a rotating speed n.
Step seven, starting the stabilized voltage supply, and then enabling the voltage of the stabilized voltage supply to be changed from U0And gradually increasing until the current sensor detects that the current of the closed path is not 0, the oil film is broken down, the closed path is conducted, and the breakdown voltage U of the oil film is kept unchanged.
Recording each current value of a closed path in a time period, and taking an average current I of each current value; then calculating the oil film resistance
Step nine, calculating the resistivity E of the oil film of the detected lubricating grease as R/H, wherein H is a dimensional form of the minimum oil film thickness;
the dimensional form of the minimum oil film thickness is:
wherein, λ is the ratio of the ball diameter and the pitch circle diameter of the tested bearing, α is the viscosity pressure coefficient of the tested grease, and η0The method comprises the steps that the viscosity of the grease to be detected under atmospheric pressure is measured, n is the relative rotating speed of an inner ring and an outer ring of a detected bearing, E' is the equivalent elastic modulus of the contact between balls of the detected bearing and a bearing channel, z is the number of the balls of the detected bearing, Q is a load, and a is the major axis of an elliptical contact area between the balls of the detected bearing and the inner ring; a ═ 6k2εRc/(πE′)]1/3Q1/3Where k is the ellipticity of the elliptical contact area, ε is the second-class elliptical integral of the elliptical contact area, RcThe radius of the track circle of the curvature center of the inner ring of the measured bearing is shown.
And step ten, closing the stabilized voltage supply, stopping driving the driving mechanism, then rotating the load adjusting nut, and removing the load applied to the test steel ball and the disc.
The invention has the following beneficial effects:
1. the invention realizes the working condition of simulating the grease lubrication ball bearing through the ball disc testing module, provides the calculation and measurement method of the oil film resistivity of the lubricating grease, can detect the conductivity of the oil film of the lubricating grease in real time, is more accurate compared with other methods for testing the conductivity of the lubricating grease, and has more practical significance.
2. The test bed of the invention uses a mode of loading the spring acting on the ball disc test module, and the principle is to change the compression length of the spring to control the loading amount. Compared with a lever loading mode, the loading mode has stronger loading stability, and compared with a hydraulic loading mode, the structure is simpler and smaller, is convenient to maintain, and more meets the design requirement of a small-sized tester.
3. The test bed provided by the invention is convenient to disassemble and operate, meets the requirements of repeated experiments, is small in structure, convenient to disassemble and assemble, low in cost, and beneficial to the experiment requirements of different occasions and the transfer and maintenance of the test bed, and is convenient for further refitting and lifting of the test bed.
Drawings
FIG. 1 is a schematic overall structure diagram of an oil film conductivity test bed of a ball disc type grease lubrication ball bearing of the invention;
FIG. 2 is a schematic structural view of a loading module and a ball cover mechanism according to the present invention;
fig. 3 is a schematic diagram of an electric control circuit of the control module of the present invention.
Detailed Description
The invention will be further explained with reference to the drawings.
As shown in fig. 1, the oil film conductivity test bed for the ball disc type grease lubricated ball bearing comprises a driving mechanism, a loading module, a ball cover mechanism 4 and a ball disc testing module; the loading module comprises a load adjusting nut 6, a loading spring 7, a pressure sensor 5 and a threaded rod 8; the threaded rod 8 is vertically arranged and forms a sliding pair with the test bed rack; the top of the threaded rod 8 is provided with a limiting convex ring which is limited by the test bed rack; the loading spring 7 is sleeved on the threaded rod 8; the load adjusting nut 6 and the threaded rod 8 form a screw pair, and two ends of the loading spring 7 are respectively contacted with the load adjusting nut 6 and the test bed rack; the central threaded hole of the pressure sensor 5 (a hollow force sensor is adopted, and the signal output ends of the pressure sensors are connected with the data acquisition card) is connected with the threaded rod 8.
As shown in fig. 2, the ball cover mechanism 4 includes a sleeve 20, a ball cover 21 and a ball catching box 22; the sleeve 20 is fixed on the test bed rack; the pressure sensor 5 of the loading module and the top hole section of the central hole of the sleeve 20 form a sliding pair; the bottom of the threaded rod 8 penetrates through a central threaded hole of the pressure sensor 5 and is connected with a central threaded hole of the ball box cover 21, so that the ball box cover 21 can be conveniently detached from the threaded rod 8, and the test steel ball 3 can be conveniently detached and replaced; the ball box cover 21 is arranged in the sleeve 20; the ball clamping box 22 is fixed at the bottom end of the ball box cover 21; the bottom of the ball clamping box 22 is provided with a hemispherical notch, and the center of the bottom of the hemispherical notch is provided with a vertically arranged slit; the outer side wall of the ball catching box 22 is provided with a conical surface and is matched with the conical hole section at the bottom of the central hole of the sleeve 20.
As shown in fig. 1, the ball disc testing module comprises a testing steel ball 3, a conductive slip ring 14, a conductive slip ring spindle 15, a rolling bearing 12, a bakelite plate 13, a disc 2, a fastening nut 11, a stabilized voltage power supply, a voltage sensor and a current sensor; the test steel ball 3 is embedded into the hemispherical notch of the ball clamping box 22; the outer ring of the conductive slip ring 14 is fixed on the test bed rack; the conductive slip ring main shaft 15 is fixed with the inner ring of the conductive slip ring 14 and is driven by a driving mechanism; the bakelite plate 13 is supported on a main shaft 15 of the conductive slip ring through a rolling bearing 12; the disc 2 is sleeved on the main shaft 15 of the conductive slip ring and is positioned above the bakelite plate 13; the bottom surface of the disc 2 is axially limited by a shaft shoulder of a main shaft 15 of the conductive slip ring; the bakelite plate 13 plays an insulating role to reduce systematic errors when reading voltage and current, and can balance the ball disc test module to prevent the disc 2 and the rolling bearing 12 from bearing overlarge overturning moment; the fastening nut 11 is connected with the external thread on the top of the conductive slip ring main shaft 15 and compresses the top surface of the disc 2; the fastening nut 11 is made of an insulating material; the stabilized voltage power supply is connected with a lead interface of the outer ring of the conductive slip ring 14 through a lead, a lead interface of the inner ring of the conductive slip ring 14 is connected with a conductive slip ring main shaft 15 through a lead, the conductive slip ring main shaft 15 is connected with the disc 2 through a lead, a raceway on the top surface of the disc 2 is contacted with the test steel ball 3, and the ball clamping box 22 is connected with the stabilized voltage power supply through a lead to form a closed path; the voltage stabilizing power supply provides required voltage for the closed path, the voltage sensor measures the voltage of the voltage stabilizing power supply, and the current sensor measures the current of the closed path; and the signal output ends of the voltage sensor and the current sensor are connected with a data acquisition card (the model NI PXI-6220 can be selected).
As a preferred embodiment, as shown in FIG. 1, the test stand comprises a test stand base 19 and a test stand support; the test bed support consists of a vertical support 1, a transverse support 9 and a baffle 10; the four vertical supports 1 are arranged in an array and fixed on a base 19 of the test bed, and every two adjacent vertical supports 1 are fixed through a transverse support 9; the baffle 10 is fixed with the tops of the four vertical supports 1. The threaded rod 8 and the baffle 10 form a sliding pair; the conductive slip ring 14 is fixed with the vertical support 1.
As a preferred embodiment, as shown in fig. 1, the drive mechanism includes a stepper motor 18 and a flexible coupling 16; a shell of a stepping motor 18 is fixed on a test bed rack, and an output shaft 17 of the stepping motor 18 is connected with a conductive slip ring spindle 15 through a flexible coupling 16; the flexible coupling 16 is made of insulating materials; the stepper motor 18 is controlled by the control module.
As a more preferred embodiment, as shown in fig. 3, the control module includes a main control chip U1 (model number STM32F103C8T6), a stepper motor driver U2 (model number DM542), an air switch U3 and a switching power supply U4(220VAC-24 VDC); the switching power supply U4 is connected with alternating current through the air switch U3, and the switching power supply U4 converts the alternating current into direct current to supply power for the stepping motor driver U2 and the stepping motor 18; the main control chip U1 is connected to the stepping motor via the stepping motor driver U2, and controls the rotation angle, rotation direction and enable of the stepping motor.
As a more preferred embodiment, the stepping motor adopts a model 57CM13 stepping motor of Shenzhen Renah Intelligent control Limited and the stepping angle is 1.8 degrees. And if the subdivision coefficient of the driver of the stepping motor is set to be 32, the stepping motor rotates for one circle after 6400 pulses. The rotating speed of the stepping motor is adjusted by adjusting the pulse frequency required by one rotation of the stepping motor, and the specific adjusting range is 100-600 revolutions/min.
As a preferred embodiment, since the contact manner of the test steel ball and the disc 2 is different from the contact manner of the balls of the tested bearing and the inner ring, it is necessary to make the elastic balls and the rigid inner ring raceway contact equivalently to make the rigid test steel ball and the elastic disc top surface raceway contact, and then the radius of the test steel ball is calculated by the following equivalent formula:
wherein R is1Radius of inner ring raceway of the measured bearing, r radius of ball of the measured bearing, D diameter of ball of the measured bearing, DmIs the pitch circle diameter of the measured bearing.
The bearing to be measured in the embodiment is a QJ304 bearing, D is 9.52mm, DmCalculated as R of 34.15mmeIs 3.43 mm.
The method for testing the conductivity of the grease lubricating oil film by using the ball disc type grease lubricating ball bearing test bed comprises the following specific steps:
taking the test steel ball 3 from the ball clamping box 22, and cleaning the test steel ball 3, the hemispherical notch of the ball clamping box 22 and the top surface of the disc 2 by using petroleum ether, so that no lubricating grease is left on the test steel ball 3, the hemispherical notch of the ball clamping box 22 and the top surface of the disc 2; the test ball 3 is then inserted into the hemispherical notch of the cartridge 22 and contacts the raceway on the top surface of the disc 2.
Secondly, applying force to a loading spring 7 through a load adjusting nut 6, changing the elongation of the loading spring 7, and enabling the loading spring 7 to apply load to the load adjusting nut 6 downwards, so that the load adjusting nut 6 drives a threaded rod 8 to apply load to a pressure sensor 5 and a ball box cover 21, and the load of the ball box cover 21 is applied to the test steel ball 3 and the disc 2 through a ball clamping box 22; the pressure sensor 5 detects the magnitude of the load Q applied by the threaded rod 8.
Step three, regulating the voltage of the stabilized voltage supply, starting the stabilized voltage supply, and measuring the voltage of the stabilized voltage supply to be U by the voltage sensor0Current sensorMeasuring the current of the closed circuit as I0Calculating the total resistance R of the closed path according to ohm's lawi＝U0/I0。
And step four, closing the stabilized voltage supply, rotating the load adjusting nut 6, and removing the load applied to the test steel ball 3 and the disc 2.
And step five, coating lubricating grease in the raceway of the disc 2 and on the test steel ball 3, then rotating the load adjusting nut 6, applying a load Q to the test steel ball 3 and the disc 2 again, and enabling the test steel ball 3 to be in contact with the raceway on the top surface of the disc 2.
And step six, the driving mechanism drives the conductive slip ring main shaft 15 to rotate, and the conductive slip ring main shaft 15 drives the disc 2 to rotate at the rotating speed n.
Step seven, starting the stabilized voltage supply, and then enabling the voltage of the stabilized voltage supply to be changed from U0And gradually increasing until the current sensor detects that the current of the closed path is not 0, which indicates that the oil film is broken down, and conducting the closed path (before the oil film is broken down, the resistance is 0, and the closed path cannot be conducted), and keeping the breakdown voltage U of the oil film unchanged.
Recording each current value of a closed path in a time period, and taking an average current I of each current value; then calculating the oil film resistance
In this example RiWhen U is 5V and the average current I is 0.2A, then R is 5V/0.2A-10 Ω -15 Ω.
Step nine, calculating the resistivity E of the oil film of the detected lubricating grease as R/H, wherein H is a dimensional form of the minimum oil film thickness;
the minimum oil film thickness is calculated by a Dowson-Higginson minimum film thickness formula, and the minimum oil film thickness is in a dimensional form:
wherein, λ is the ratio of the ball diameter and the pitch circle diameter of the tested bearing, α is the viscosity pressure coefficient of the tested grease, and η0The grease to be tested is at atmospheric pressureN is the relative rotating speed of the inner ring and the outer ring of the tested bearing (also is the rotating speed of the disc 2 arranged in the embodiment), E' is the equivalent elastic modulus of the contact between the balls of the tested bearing and the bearing channel, z is the number of the balls of the tested bearing, Q is the load, and a is the major axis of the elliptical contact area between the balls of the tested bearing and the inner ring; a is calculated by the Hertz elastic contact formula, i.e. a ═ 6k2εRc/(πE′)]1/3Q1/3Where k is the ellipticity of the elliptical contact area, ε is the second-class elliptical integral of the elliptical contact area, RcThe radius of the track circle of the curvature center of the inner ring of the measured bearing is shown.
The bearing to be measured in the embodiment is a QJ304 bearing, lambda is 0.2788, and alpha is 0.022mm2/N，λ＝2*10-8N*s/mm2，n＝100r/min，E′＝2.23*105MPa, z 9, Q100N, a 4.12mm, calculated H2.6 x 10-5mm，E＝5.77*105Ω/mm。
And step ten, closing the stabilized voltage supply, stopping driving the driving mechanism, then rotating the load adjusting nut 6, and removing the load applied to the test steel ball 3 and the disc 2.
Claims (6)
1. Ball disk grease lubrication ball bearing oil film conductivity test platform, including actuating mechanism and loading module, its characterized in that: the device also comprises a ball cover mechanism and a ball disc testing module; the loading module comprises a load adjusting nut, a loading spring, a pressure sensor and a threaded rod; the threaded rod is vertically arranged and forms a sliding pair with the test bed rack; the top of the threaded rod is provided with a limiting convex ring which is limited by the test bed rack; the loading spring is sleeved on the threaded rod; the load adjusting nut and the threaded rod form a screw pair, and two ends of the loading spring are respectively contacted with the load adjusting nut and the test bed rack; the central threaded hole of the pressure sensor is connected with the threaded rod;
the ball cover mechanism comprises a sleeve, a ball cover and a ball clamping box; the sleeve is fixed on the test bed rack; a pressure sensor of the loading module and the top hole section of the central hole of the sleeve form a sliding pair; the bottom of the threaded rod penetrates through a central threaded hole of the pressure sensor and is connected with a central threaded hole of the ball box cover; the ball box cover is arranged in the sleeve; the ball clamping box is fixed at the bottom end of the ball box cover; the bottom of the ball clamping box is provided with a hemispherical notch, and the center of the bottom of the hemispherical notch is provided with a vertically arranged slit; the outer side wall of the ball clamping box is provided with a conical surface and is matched with a conical hole section at the bottom of the central hole of the sleeve;
the ball disc testing module comprises a testing steel ball, a conductive slip ring main shaft, a rolling bearing, a bakelite plate, a disc, a fastening nut, a voltage-stabilized power supply, a voltage sensor and a current sensor; the test steel ball is embedded into the hemispherical notch of the ball clamping box; the outer ring of the conductive slip ring is fixed on the test bed rack; the main shaft of the conductive slip ring is fixed with the inner ring of the conductive slip ring and is driven by a driving mechanism; the bakelite plate is supported on a main shaft of the conductive slip ring through a rolling bearing; the disc is sleeved on the main shaft of the conductive slip ring and is positioned above the bakelite plate; the bottom surface of the disc is axially limited by a shaft shoulder of the main shaft of the conductive slip ring; the fastening nut is connected with the external thread on the top of the main shaft of the conductive slip ring and compresses the top surface of the disc; the fastening nut is made of insulating materials; the stabilized voltage power supply is connected with a lead interface of the outer ring of the conductive slip ring through a lead, a lead interface of the inner ring of the conductive slip ring is connected with a main shaft of the conductive slip ring through a lead, the main shaft of the conductive slip ring is connected with the disc through a lead, a raceway on the top surface of the disc is contacted with a test steel ball, and the ball clamping box is connected with the stabilized voltage power supply through a lead to form a closed passage; the voltage sensor measures the voltage of the voltage-stabilized power supply, the current sensor measures the current of the closed circuit, and the signal output ends of the voltage sensor and the current sensor are connected with the data acquisition card.
2. The oil film conductivity test stand of the ball disc type grease lubricated ball bearing according to claim 1, characterized in that: the test bed rack comprises a test bed base and a test bed support; the test bed support consists of a vertical support, a transverse support and a baffle; the four vertical supports are arranged in an array and fixed on the base of the test bed, and every two adjacent vertical supports are fixed through a transverse support; the baffle is fixed with the tops of the four vertical supports; the threaded rod and the baffle form a sliding pair; the conductive slip ring is fixed with the vertical support.
3. The oil film conductivity test stand of the ball disc type grease lubricated ball bearing according to claim 1, characterized in that: the driving mechanism comprises a stepping motor and a flexible coupling; the shell of the stepping motor is fixed on the test bed rack, and the output shaft of the stepping motor is connected with the conductive slip ring main shaft through a flexible coupling; the flexible coupling is made of insulating materials; the stepping motor is controlled by the control module.
4. The oil film conductivity test stand of the ball disc type grease lubricated ball bearing according to claim 3, characterized in that: the control module comprises a main control chip, a stepping motor driver, an air switch and a switching power supply; the switch power supply is connected with alternating current through the air switch and converts the alternating current into direct current to supply power for the stepping motor driver and the stepping motor; the main control chip is connected with the stepping motor through the stepping motor driver and controls the rotation angle, the rotation direction and the enabling of the stepping motor.
5. The oil film conductivity test stand of a ball-and-disc type grease lubricated ball bearing according to any one of claims 1 to 4, characterized in that: the radius of the test steel ball is calculated by the equivalent formula:
wherein R is1Radius of inner ring raceway of the measured bearing, r radius of ball of the measured bearing, D diameter of ball of the measured bearing, DmIs the pitch circle diameter of the measured bearing.
6. The method for testing the conductivity of a grease lubrication oil film by using the oil film conductivity test stand for the ball disc type grease lubricated ball bearing according to claim 5, wherein the method comprises the following steps: the method comprises the following specific steps:
taking the test steel ball down from the ball clamping box, and cleaning the test steel ball, the hemispherical notch of the ball clamping box and the top surface of the disc by using petroleum ether so that no lubricating grease is left on the test steel ball, the hemispherical notch of the ball clamping box and the top surface of the disc; then, embedding the test steel ball into the semi-spherical notch of the ball clamping box and contacting with the raceway on the top surface of the disc;
secondly, applying force to the loading spring through the load adjusting nut, changing the elongation of the loading spring, and enabling the loading spring to apply load to the load adjusting nut downwards, so that the load adjusting nut drives the threaded rod to apply load to the pressure sensor and the ball box cover, and the load of the ball box cover is applied to the test steel ball and the disc through the ball clamping box; the pressure sensor detects the size of a load Q applied by the threaded rod;
step three, regulating the voltage of the stabilized voltage supply, starting the stabilized voltage supply, and measuring the voltage of the stabilized voltage supply to be U by the voltage sensor0The current sensor measures the current of the closed path as I0Calculating the total resistance R of the closed path according to ohm's lawi＝U0/I0；
Step four, turning off the stabilized voltage supply, rotating the load adjusting nut, and removing the load applied to the test steel ball and the disc;
coating lubricating grease in the raceway of the disc and on the test steel ball, then rotating the load adjusting nut, and applying a load Q to the test steel ball and the disc again to enable the test steel ball to be in contact with the raceway on the top surface of the disc;
driving a conductive slip ring main shaft to rotate by a driving mechanism, and driving a disc to rotate at a rotating speed n by the conductive slip ring main shaft;
step seven, starting the stabilized voltage supply, and then enabling the voltage of the stabilized voltage supply to be changed from U0Gradually rising until the current sensor detects that the current of the closed path is not 0, the oil film is broken down, the closed path is conducted, and the breakdown voltage U of the oil film is kept unchanged;
recording each current value of a closed path in a time period, and taking an average current I of each current value; then calculateOil film resistance
Step nine, calculating the resistivity E of the oil film of the detected lubricating grease as R/H, wherein H is a dimensional form of the minimum oil film thickness;
the dimensional form of the minimum oil film thickness is:
wherein, λ is the ratio of the ball diameter and the pitch circle diameter of the tested bearing, α is the viscosity pressure coefficient of the tested grease, and η0The method comprises the steps that the viscosity of the grease to be detected under atmospheric pressure is measured, n is the relative rotating speed of an inner ring and an outer ring of a detected bearing, E' is the equivalent elastic modulus of the contact between balls of the detected bearing and a bearing channel, z is the number of the balls of the detected bearing, Q is a load, and a is the major axis of an elliptical contact area between the balls of the detected bearing and the inner ring; a ═ 6k2εRc/(πE′)]1/3Q1/3Where k is the ellipticity of the elliptical contact area, ε is the second-class elliptical integral of the elliptical contact area, RcThe radius of the track circle of the curvature center of the inner ring of the bearing to be measured;
and step ten, closing the stabilized voltage supply, stopping driving the driving mechanism, then rotating the load adjusting nut, and removing the load applied to the test steel ball and the disc.
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