CN113533858B - 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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- CN113533858B CN113533858B CN202110721117.9A CN202110721117A CN113533858B CN 113533858 B CN113533858 B CN 113533858B CN 202110721117 A CN202110721117 A CN 202110721117A CN 113533858 B CN113533858 B CN 113533858B
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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
- G01R1/02—General constructional details
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- G01R1/0408—Test fixtures or contact fields; Connectors or connecting adaptors; Test clips; Test sockets
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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 the grease lubrication ball bearing, the loading module loads the ball cover mechanism, and the driving mechanism drives the ball disc testing module. According to the invention, the conductivity of the lubricating grease 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, the steel ball generates an oil film with a certain thickness due to dynamic pressure lubrication of elastic fluid, the resistance of the oil film part is calculated by measuring the breakdown voltage and the current under the condition, and the specific resistance 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 rotary machinery, is an indispensable key component in the fields of various aviation, reworking, advanced manufacturing equipment and the like, and is also an object which is provided by China's manufacture 2025' and needs to be focused and researched aiming at the current situation of weak industrial basic capacities of core basic components (components), advanced basic processes, key basic materials, industrial technical foundations and the like. The performance and the service life of the rolling bearing are improved, and the rolling bearing has great significance for the development of mechanical industry and other related industries in China.
Electrolytic corrosion is a common failure form of a rolling bearing, and means that when current flows in a contact portion of a bearing raceway and a rolling element in rotation, spark is generated through a thin lubricating oil film, and local melting and concave-convex phenomena occur on the surface. Such failure modes are frequent in motor bearings, rail bearings of subway trains, and the like. At present, in order to overcome the influence of bearing electric erosion, an insulating method is generally adopted, for example, a ceramic ball bearing is adopted to insulate the inner ring and the outer ring of the bearing, but the bearing capacity and the material strength of the bearing are far lower than those of the bearing manufactured by the traditional GGr15 steel, for example, an insulating coating method is adopted to treat a bearing raceway and a rolling body, but the problem of long-life high-reliability bearing insulation cannot be solved due to peeling and friction consumption of a pattern layer.
In recent years, the change of the electrical conductivity of bearings by means of grease is a new research direction. In order to study the influence of lubricating grease and additives with different components on the conductivity of a rolling bearing, the insulation and conductivity characteristics of the lubricating grease in the contact form of a rolling body/a raceway of the bearing are accurately simulated in real time, and a series of performance test benches and test methods aiming at the conductivity of the lubricating grease are needed.
Disclosure of Invention
Aiming at the problem that the conventional grease conductivity test method cannot accurately reflect the actual conductivity of a grease lubrication rolling ball bearing in operation, the invention provides a ball disc type grease lubrication ball bearing oil film conductivity test bed and a test method thereof, wherein a ball disc test module is utilized to simulate the working condition of the grease lubrication ball bearing, and the conductivity of a grease film is measured by introducing the oil film resistivity, so that the real-time detection of the bearing grease conductivity 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, the steel ball generates an oil film with a certain thickness due to dynamic pressure lubrication of elastic fluid, the resistance of the oil film part is calculated by measuring the breakdown voltage and the current under the condition, and the specific resistance 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, wherein the loading module is arranged on the driving mechanism; 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 frame; the top of the threaded rod is provided with a limiting convex ring, and the limiting convex ring is limited by the test bench; 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 bench; 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 bench; the 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 passes 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 a slit which is vertically arranged is arranged at the center of the bottom of the hemispherical notch; the outer side wall of the ball clamping box is provided with a conical surface and is matched with the 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 stabilized voltage 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 bench; the conductive slip ring main shaft is fixed with the inner ring of the conductive slip ring and is driven by the driving mechanism; the bakelite plate is supported on the 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 the shaft shoulder of the conductive slip ring main shaft; the fastening nut is connected with the external thread at 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 ball clamping box is connected with the constant voltage power supply through a wire, so as to form a closed passage; the voltage sensor measures the voltage of the regulated power supply, 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 the data acquisition card.
Preferably, the test bed stand 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 and fixed on the base of the test bed in an array manner, and every two adjacent vertical supports are fixed through one transverse support; the baffle plate 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 bench, and an output shaft of the stepping motor is connected with the main shaft of the conductive slip ring 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 rotating angle, the rotating direction and the enabling of the stepping motor.
Preferably, the radius of the test steel ball is calculated by the following equivalent formula:
wherein R is 1 The radius of the inner ring raceway of the measured bearing is r is the radius of the ball of the measured bearing, D is the diameter of the ball of the measured bearing, and D m The pitch diameter of the measured bearing.
The test method of the ball-disc type grease lubrication ball bearing test bed for the conductivity of the grease lubrication film comprises the following specific steps:
step one, taking down the test steel ball 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 remains on the test steel ball, the hemispherical notch of the ball clamping box and the top surface of the disc; then, the test steel ball is inserted into the hemispherical notch of the cartridge and contacts the raceway on the top surface of the disk.
The second step, the loading spring is forced by the load adjusting nut, the elongation of the loading spring is changed, the loading spring applies load downwards to the load adjusting nut, 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 regulated power supply, starting the regulated power supply, and measuring the voltage of the regulated power supply as U by a voltage sensor 0 The current sensor measures the current of the closed path as I 0 The total resistance R of the closed path is calculated according to ohm's law i ＝U 0 /I 0 。
And fourthly, turning off the stabilized voltage power supply, rotating the load adjusting nut, and relieving the load applied to the test steel ball and the disc.
And fifthly, coating lubricating grease in the rollaway nest of the disc and on the test steel ball, then rotating the load adjusting nut, and applying load Q to the test steel ball and the disc again to enable the test steel ball to be in contact with the rollaway nest of 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 regulated power supply, and then enabling the voltage of the regulated power supply to be equal to the voltage of the U 0 And gradually rising until the current sensor detects that the current of the closed path is not 0, and breaking down the oil film, wherein the closed path is conducted, so that the breakdown voltage U of the oil film is kept unchanged.
Step eight, recording all current values of a closed path in a time period, and taking the average current I of all the current values; then calculate the oil film resistance
Step nine, calculating the resistivity E=R/H of the measured lubricating grease film, wherein H is in a dimensional form of the minimum oil film thickness;
the minimum oil film thickness has the dimensional form:
wherein lambda is the ratio of the ball diameter to the pitch diameter of the bearing to be measured, alpha is the viscosity-pressure coefficient of the grease to be measured, eta 0 The viscosity of the measured lubricating grease under the atmospheric pressure is n, the relative rotational speeds of the inner ring and the outer ring of the measured bearing are n, E' is the equivalent elastic modulus of contact between the balls of the measured bearing and a bearing channel, z is the number of the balls of the measured bearing, Q is the load, and a is the long axis of an elliptical contact area between the balls of the measured bearing and the inner ring; a= [6k 2 εR c /(πE′)] 1/3 Q 1/3 Where k is the ellipticity of the elliptical contact area, ε is the second type of ellipse integral of the elliptical contact area, R c The radius of the track circle is the radius of the curvature center of the inner ring of the bearing to be measured.
And step ten, switching off the stabilized voltage power supply, stopping driving the driving mechanism, and then rotating the load adjusting nut to release the load applied to the test steel ball and the disc.
The invention has the beneficial effects that:
1. according to the invention, the working condition of the grease lubrication ball bearing is simulated through the ball disc test module, and the calculation and measurement method of the resistivity of the grease film is provided, so that the conductivity of the grease film can be detected in real time, and compared with other grease conductivity test methods, the method is more accurate and has more practical significance.
2. The test bed of the invention uses a mode of loading the spring on the ball disc test module, and the principle is that the compression length of the spring is changed 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 meets the design requirement of a small-sized tester.
3. The test bed is convenient to detach and operate, meets the requirement of repeated experiments, is small in structure, convenient to assemble and disassemble, low in cost, and convenient to refit and lift, and is favorable for the experiment requirements of different occasions and the transfer and maintenance of the test bed.
Drawings
FIG. 1 is a schematic diagram of the overall structure of a ball-and-disc type grease lubrication ball bearing oil film conductivity test bed;
FIG. 2 is a schematic view of the loading module and the ball cover mechanism according to the present invention;
fig. 3 is a schematic diagram of an electric control circuit of the control module in the present invention.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
As shown in fig. 1, the ball-disc type grease lubrication ball bearing oil film conductivity test bed 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 frame; the top of the threaded rod 8 is provided with a limiting convex ring, and the limiting convex ring is limited by a test bench; 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; the center screw hole of the pressure sensor 5 (a hollow force sensor is adopted, and the signal output ends of the pressure sensor are all connected with a 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 stand; 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 passes through the central threaded hole of the pressure sensor 5 and is connected with the central threaded hole of the ball box cover 21, so that the ball box cover 21 is convenient to detach from the threaded rod 8, and the test steel ball 3 is convenient to detach and replace; 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 a slit which is vertically arranged is arranged at the center of the bottom of the hemispherical notch; the outer side wall of the ball clamping 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-and-disc test module comprises a test steel ball 3, a conductive slip ring 14, a conductive slip ring main shaft 15, a rolling bearing 12, an bakelite plate 13, a disc 2, a fastening nut 11, a stabilized voltage 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 bench; the conductive slip ring main shaft 15 is fixed with the inner ring of the conductive slip ring 14 and driven by a driving mechanism; the bakelite plate 13 is supported on a conductive slip ring main shaft 15 through a rolling bearing 12; the disc 2 is sleeved on the conductive slip ring main shaft 15 and is positioned above the bakelite plate 13; the bottom surface of the disc 2 is axially limited by the shaft shoulder of the conductive slip ring main shaft 15; the bakelite plate 13 plays an insulating role to reduce systematic errors when voltage and current are read, 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 external threads 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 insulating materials; the constant voltage power supply is connected with a wire interface of the outer ring of the conductive slip ring 14 through a wire, the wire interface of the inner ring of the conductive slip ring 14 is connected with the conductive slip ring main shaft 15 through a wire, the conductive slip ring main shaft 15 is connected with the disc 2 through a wire, the 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 constant voltage power supply through a wire to form a closed path; the voltage-stabilized power supply provides required voltage for the closed path, the voltage sensor measures the voltage of the voltage-stabilized power supply, and the current sensor measures the current of the closed path; the signal output ends of the voltage sensor and the current sensor are connected with a data acquisition card (model NI PXI-6220 can be selected).
As a preferred embodiment, as shown in fig. 1, the test stand includes 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 and fixed on the test bed base 19 in an array manner, and every two adjacent vertical supports 1 are fixed through one transverse support 9; the baffle 10 is fixed with the tops of the four vertical brackets 1. The threaded rod 8 and the baffle 10 form a sliding pair; the conductive slip ring 14 is fixed with the vertical bracket 1.
As a preferred embodiment, as shown in fig. 1, the drive mechanism includes a stepper motor 18 and a flexible coupling 16; the shell of the stepping motor 18 is fixed on the test bed frame, and an output shaft 17 of the stepping motor 18 is connected with the conductive slip ring main shaft 15 through a flexible coupling 16; the flexible coupling 16 is made of insulating materials; the stepper motor 18 is controlled by a control module.
As a more preferred embodiment, as shown in FIG. 3, the control module includes a main control chip U1 (model STM32F103C8T 6), a stepper motor driver U2 (model DM 542), an air switch U3, and a switching power supply U4 (220 VAC-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 with a stepping motor through a stepping motor driver U2 and controls the rotating angle, the rotating direction and the enabling of the stepping motor.
As a more preferred embodiment, the stepping motor is a type 57CM13 stepping motor of Shenzhen Racing Intelligent control Co., ltd, and the stepping angle is 1.8 °. Setting the stepper motor driver subdivision coefficient to 32, the stepper motor rotates one revolution over 6400 pulses. The rotating speed of the stepping motor is regulated by regulating the pulse frequency required by one rotation of the stepping motor, and the specific regulating range is 100-600 revolutions/min.
As a preferred embodiment, since the contact mode of the test steel ball with the disc 2 is different from the contact mode of the ball of the bearing to be tested with the inner ring, the contact between the elastic ball and the rigid inner ring raceway is equivalent to the contact between the rigid test steel ball and the elastic disc top surface raceway, and then the radius of the test steel ball is calculated by the following equivalent formula:
wherein R is 1 The radius of the inner ring raceway of the measured bearing is r is the radius of the ball of the measured bearing, D is the diameter of the ball of the measured bearing, and D m The pitch diameter of the measured bearing.
The embodiment is covered byThe measuring bearing is a QJ304 bearing, d=9.52 mm, D m =34.15 mm, calculated as R e Is 3.43mm.
The test method of the ball-disc type grease lubrication ball bearing test bed for the conductivity of the grease lubrication film comprises the following specific steps:
step one, taking the test steel ball 3 out of 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 remains on the test steel ball 3, the hemispherical notch of the ball clamping box 22 and the top surface of the disc 2; then, the test steel ball 3 is inserted into the hemispherical notch of the cartridge 22 and is in contact with the raceway of the top surface of the disc 2.
Step two, the loading spring 7 is forced through the load adjusting nut 6, the elongation of the loading spring 7 is changed, so that the loading spring 7 applies load to the load adjusting nut 6 downwards, the load adjusting nut 6 drives the threaded rod 8 to apply load to the pressure sensor 5 and the 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 the 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 regulated power supply, starting the regulated power supply, and measuring the voltage of the regulated power supply as U by a voltage sensor 0 The current sensor measures the current of the closed path as I 0 The total resistance R of the closed path is calculated according to ohm's law i ＝U 0 /I 0 。
And fourthly, switching off the stabilized voltage power supply, rotating the load adjusting nut 6, and relieving the load applied to the test steel ball 3 and the disc 2.
Fifthly, lubricating grease is smeared in the rollaway nest of the disc 2 and on the test steel ball 3, then the load adjusting nut 6 is rotated, and a load Q is applied to the test steel ball 3 and the disc 2 again, wherein the test steel ball 3 is in contact with the rollaway nest of the top surface of the disc 2.
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 a rotating speed n.
Step seven, starting the regulated power supply, and then enabling the voltage of the regulated power supply to be equal to the voltage of the U 0 Step up until the current sensor detects closureWhen the current of the passage is not 0, the oil film is broken down, the closed passage is conducted (the resistance is 0 before the oil film is broken down, and the closed passage cannot be conducted), so that the breakdown voltage U of the oil film is kept unchanged.
Step eight, recording all current values of a closed path in a time period, and taking the average current I of all the current values; then calculate the oil film resistanceR in the present embodiment i =10Ω, U is 5V, the average current i=0.2a, then r=5v/0.2a-10Ω=15Ω.
Step nine, calculating the resistivity E=R/H of the measured lubricating grease film, wherein H is in a dimensional form of the minimum oil film thickness;
the minimum oil film thickness is calculated by a minimum film thickness formula of Dowson-Higginson, and has the dimensional form:
wherein lambda is the ratio of the ball diameter to the pitch diameter of the bearing to be measured, alpha is the viscosity-pressure coefficient of the grease to be measured, eta 0 For the viscosity of the measured grease under the atmospheric pressure, n is the relative rotation speed of the inner ring and the outer ring of the measured bearing (also the rotation speed of the disc 2 arranged in the embodiment), E' is the equivalent elastic modulus of the contact between the ball of the measured bearing and the bearing channel, z is the number of the ball of the measured bearing, Q is the load, and a is the long axis of the elliptical contact area between the ball of the measured bearing and the inner ring; a is calculated by the Hertz elastic contact formula, i.e. a= [6k 2 εR c /(πE′)] 1/3 Q 1/3 Where k is the ellipticity of the elliptical contact area, ε is the second type of ellipse integral of the elliptical contact area, R c The radius of the track circle is the radius of the curvature center of the inner ring of the bearing to be measured.
The tested bearing of the embodiment selects a QJ304 bearing, lambda= 0.2788, alpha=0.022 mm 2 /N，λ＝2*10 -8 N*s/mm 2 ，n＝100r/min，E′＝2.23*10 5 MPa, z=9, q=100n, a=4.12 mm, calculated to be H2.6x10 -5 mm，E＝5.77*10 5 Ω/mm。
And step ten, switching off the stabilized voltage power supply, stopping driving the driving mechanism, and then rotating the load adjusting nut 6 to release the load applied to the test steel ball 3 and the disc 2.
Claims (6)
1. The utility model provides a ball dish formula fat lubrication ball bearing oil film conductivity test bench, includes 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 frame; the top of the threaded rod is provided with a limiting convex ring, and the limiting convex ring is limited by the test bench; 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 bench; the center 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 bench; the 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 passes 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 a slit which is vertically arranged is arranged at the center of the bottom of the hemispherical notch; 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 stabilized voltage 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 bench; the conductive slip ring main shaft is fixed with the inner ring of the conductive slip ring and is driven by the driving mechanism; the bakelite plate is supported on the 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 the shaft shoulder of the conductive slip ring main shaft; the fastening nut is connected with the external thread at 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 ball clamping box is connected with the constant voltage power supply through a wire, so as to form a closed passage; the voltage sensor measures the voltage of the regulated power supply, 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 the data acquisition card.
2. The ball-and-disc type grease-lubricated ball bearing oil film conductivity test stand according to claim 1, wherein: the test bed stand 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 and fixed on the base of the test bed in an array manner, and every two adjacent vertical supports are fixed through one transverse support; the baffle is fixed with the tops of the four vertical brackets; the threaded rod and the baffle form a sliding pair; the conductive slip ring is fixed with the vertical support.
3. The ball-and-disc type grease-lubricated ball bearing oil film conductivity test stand according to claim 1, wherein: the driving mechanism comprises a stepping motor and a flexible coupling; the shell of the stepping motor is fixed on the test bench, and an output shaft of the stepping motor is connected with the main shaft of the conductive slip ring through a flexible coupling; the flexible coupling is made of insulating materials; the stepping motor is controlled by the control module.
4. A ball-and-disc type grease-lubricated ball bearing oil film conductivity test stand according to claim 3, wherein: 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 rotating angle, the rotating direction and the enabling of the stepping motor.
5. The ball-and-disc type grease-lubricated ball bearing oil film conductivity test stand according to any one of claims 1 to 4, wherein: the radius of the test steel ball is calculated by the following equivalent formula:
wherein R is 1 The radius of the inner ring raceway of the measured bearing is r is the radius of the ball of the measured bearing, D is the diameter of the ball of the measured bearing, and D m The pitch diameter of the measured bearing.
6. A method for testing the conductivity of a grease lubricating oil film by using the ball-and-disc grease lubricating ball bearing oil film conductivity test bed according to claim 5, which is characterized in that: the method comprises the following steps:
step one, taking down the test steel ball 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 remains on the test steel ball, the hemispherical notch of the ball clamping box and the top surface of the disc; then, the test steel ball is embedded into a hemispherical notch of the ball clamping box and is contacted with a raceway on the top surface of the disc;
the second step, the loading spring is forced by the load adjusting nut, the elongation of the loading spring is changed, the loading spring applies load downwards to the load adjusting nut, 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 load Q applied by the threaded rod;
step three, adjustingVoltage of the stabilized power supply is regulated, the stabilized power supply is started, and the voltage sensor detects that the voltage of the stabilized power supply is U 0 The current sensor measures the current of the closed path as I 0 The total resistance R of the closed path is calculated according to ohm's law i ＝U 0 /I 0 ；
Turning off the stabilized voltage power supply, rotating the load adjusting nut, and relieving the load applied to the test steel ball and the disc;
fifthly, grease is smeared in the rollaway nest of the disc and on the test steel ball, then the load adjusting nut is rotated, and a load Q is applied to the test steel ball and the disc again, so that the test steel ball is contacted with the rollaway nest of the top surface of the disc;
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 regulated power supply, and then enabling the voltage of the regulated power supply to be equal to the voltage of the U 0 Gradually rising until the current sensor detects that the current of the closed path is not 0, and breakdown of the oil film is carried out, wherein the closed path is conducted, and the breakdown voltage U of the oil film is kept unchanged;
step eight, recording all current values of a closed path in a time period, and taking the average current I of all the current values; then calculate the oil film resistance
Step nine, calculating the resistivity E=R/H of the measured lubricating grease film, wherein H is in a dimensional form of the minimum oil film thickness;
the minimum oil film thickness has the dimensional form:
wherein lambda is the ratio of the ball diameter to the pitch diameter of the bearing to be measured, alpha is the viscosity-pressure coefficient of the grease to be measured, eta 0 The viscosity of the measured grease under the atmospheric pressure is n is the relative rotation speed of the inner ring and the outer ring of the measured bearing, E' is the equivalent of the contact between the ball of the measured bearing and a bearing channelThe elastic modulus, z is the number of balls of the bearing to be tested, Q is the load, and a is the major axis of the elliptical contact area between the balls of the bearing to be tested and the inner ring; a= [6k 2 εR c /(πE′)] 1/3 Q 1/3 Where k is the ellipticity of the elliptical contact area, ε is the second type of ellipse integral of the elliptical contact area, R c The radius of the track circle is the radius of the curvature center of the inner ring of the bearing to be measured;
and step ten, switching off the stabilized voltage power supply, stopping driving the driving mechanism, and then rotating the load adjusting nut to release the load applied to the test steel ball and the disc.
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| CN112255144A (en) * | 2020-09-30 | 2021-01-22 | 杭州电子科技大学 | Rolling bearing lubricating grease rolling deposition film wetting characteristic test bed and test method thereof |
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| US6300701B1 (en) * | 1999-02-23 | 2001-10-09 | General Electric Canada Inc. | Rogowski coil method of determination of bearing lubrication in dynamoelectric machines |
| JP2006317273A (en) * | 2005-05-12 | 2006-11-24 | Ntn Corp | Bearing testing device and method thereof |
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| CN206906026U (en) * | 2017-07-15 | 2018-01-19 | 华东交通大学 | A kind of electrodynamic type bearing test-bed varying load loading unit |
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