Grease lubrication friction electricity passive wireless rotating speed sensor for bearing slip monitoring

Abstract

The invention discloses a grease lubrication friction electricity passive wireless rotating speed sensor for bearing slip monitoring, which comprises two bearing seat cover bodies for mounting a bearing body, a friction nanometer generator, a signal processing module and a power supply management module, and is characterized in that the friction nanometer generator consists of a rotor unit and a stator unit; the inner ring surface of the bearing body is fixedly connected with a rotating shaft, and the rotating shaft can sequentially drive the bearing retainer and the rotor unit to rotate so as to output electric energy. The rotor unit and the stator unit are arranged, an interface grease lubrication strategy is utilized, the energy supply level and durability of the friction nanometer generator are improved at the same time, and wireless real-time monitoring of the slipping state of the bearing body in a compact space in a transmission system can be achieved without the help of an external power source; the working reliability and the intelligent operation and maintenance level of mechanical equipment are improved, and high-performance operation of high-end equipment is further guaranteed.

Description

Technical Field

[0001] This application relates to the technical field of self-powered and self-sensing of intelligent bearings, and particularly to a grease-lubricated triboelectric passive wireless rotational speed sensor for bearing slip monitoring. Background Art

[0002] Rolling bearings are one of the most critical basic components in rotating machinery systems. Effective condition monitoring of the operating state of bearings is of great significance for ensuring the safe and stable operation of mechanical equipment. Slip, that is, the unexpected relative movement between the inner and outer rings of the bearing and the rolling elements due to reasons such as excessive lubrication, insufficient load, or improper assembly, may lead to local overheating, surface damage, and even the rapid failure of the entire bearing system. It is one of the failure forms during the operation of rolling bearings and is particularly common in high-speed and light-load working conditions involved in aerospace and other fields. Once slip occurs, it will pose a great threat to the stable operation of the bearing. By real-time monitoring of bearing slip, potential fault points can be detected in time, preventive measures can be taken, and equipment shutdown, production line interruption, and even more serious safety accidents caused by bearing failure can be avoided.

[0003] After retrieval, the Chinese patent with publication number CN117572015A also discloses an electromagnetic rotational speed sensor. Based on the principle of electromagnetic induction, it is powered by an internal power supply and can wirelessly transmit data through a signal transmission circuit to achieve the purpose of real-time obtaining the rotational speed of measured parts such as wheels. However, compared with traditional electromagnetic power generation, triboelectric nanogenerators have the advantages of wide material sources, simple manufacturing processes, compact structures, high energy density, etc. Triboelectric rotational speed sensors of triboelectric nanogenerators have extensive applications in the field of bearing slip monitoring. There are still the following problems in traditional triboelectric sensors for monitoring bearing slip: (1) The continuous dry friction between the friction pairs of the sensor will cause a decrease in the durability and stability of the TENG, directly affecting the signal-to-noise ratio and service life of the sensor; (2) For traditional triboelectric sensors, due to the internal installation of corresponding functional modules such as signal processing circuits, these functional modules need to be powered separately, usually by built-in button batteries or other power supply devices. However, traditional battery power supply has the disadvantages of limited service life and large volume, which is not conducive to integration; while external power supply requires transmitting signals from rotating components such as bearings to the host computer through wires, which will affect the reliability of the bearing system. Summary of the Invention

[0004] The purpose of the present invention is to provide a grease-lubricated triboelectric passive wireless rotational speed sensor for bearing slip monitoring to solve the problems raised in the above background art.

[0005] The embodiments of this application adopt the following technical solutions:

[0006] A grease-lubricated triboelectric passive wireless speed sensor for bearing slip monitoring, comprising a bearing housing cover, a bearing cage, a triboelectric nanogenerator, a signal processing module, and a power management module. Among them, there are two bearing housing covers for installing the bearing body. The inner ring of the bearing body is sleeved with a rotating shaft, and the triboelectric nanogenerator is composed of a rotor unit and a stator unit.

[0007] Further, the rotor unit includes a connecting piece. A boss is provided on one side of the connecting piece close to the bearing, and a rotor body is provided on the side of the connecting piece away from the bearing. The rotor unit is engaged with the bearing cage through the boss, and the two achieve an interference fit.

[0008] Further, the stator unit includes a stator end cover. A stator body is fixedly connected inside the stator end cover through a high-temperature adhesive. The stator body is a metal electrode with a rotating array staggered distribution. A polymer film is spin-coated on the stator body.

[0009] Further, the rotor body and the stator body have the same structure, both including an inner ring electrode and an outer ring electrode. The inner ring electrode serves as the signal source of the sensor itself, and the outer ring electrode serves as the energy source for sensor signal processing.

[0010] Further, a grease with a low dielectric constant and low consistency is added between the rotor body and the polymer film.

[0011] Further, a sealing end cover is fixedly connected to the outer ring of the bearing body. The stator end cover is fixedly connected to the sealing end cover through screws, and a rubber gasket is provided between the sealing end cover and the stator end cover.

[0012] Further, a sealing groove is machined on the inner circumferential surface of the sealing end cover. Multiple sealing grooves form a labyrinth sealing structure. The radius of the sealing groove is 0.8 mm, and the unilateral gap with the connecting piece is 0.5 mm.

[0013] Further, the signal processing module is integrated on the back of the stator body; the power management module is integrated on the back of the stator body.

[0014] Further, a method for detecting bearing slip using the sensor specifically includes the following steps:

[0015] S1, the triboelectric signal generated by the mutual friction of the stator unit and the rotor unit under the action of grease lubrication;

[0016] S2, the signal processing module calculates the actual speed of the cage according to the characteristic frequency of the extracted triboelectric signal; the calculation is as follows:

[0017] n c =60f sig / N

[0018] Where, n c is the actual speed of the cage, fsig f is the frequency of the triboelectric signal, and N is the number of groups of staggered metal electrodes of the triboelectric nanogenerator.

[0019] S3. The signal processing module calculates the theoretical rotational speed of the cage according to the calculation formulas of the rotational speed of the inner ring and the rotational speed of the cage of the rolling bearing:

[0020]

[0021] where n 0 is the theoretical rotational speed of the cage, n i is the rotational speed of the inner ring of the bearing, D w is the diameter of the ball, D pw is the pitch diameter of the bearing, α b is the contact angle of the bearing.

[0022] S4. Using the single-chip microcomputer minimum system in the signal processing module, calculate the slip rate of the cage according to the actual rotational speed and the theoretical rotational speed of the cage:

[0023]

[0024] where, n 0 and n c are respectively the theoretical rotational speed and the actual rotational speed of the cage under pure rolling conditions.

[0025] The above at least one technical solution adopted in the embodiments of the present application can achieve the following beneficial effects:

[0026] 1. By setting the rotor unit and the stator unit, and using the rotating shaft to drive the rotor unit to rotate, it is possible to realize wireless real-time monitoring of the slip state of the bearing body in the compact space inside the transmission system without relying on an external power source, improving the working reliability and intelligent operation and maintenance level of the mechanical equipment, and further ensuring the high-performance operation of the high-end equipment.

[0027] 2. By adding a lubricating grease with a low dielectric constant and a low consistency between the friction interfaces of the stator unit and the rotor unit, it is possible to reduce the wear of the triboelectric nanogenerator while further increasing the output charge of the triboelectric nanogenerator, ensuring the stability of the cage slip state monitoring under passive conditions.

[0028] 3. Since the signal processing modules all require an external power supply, two triboelectric nanogenerator units are designed, one as a sensor and the other as an energy source. Additionally, two regions, an inner ring and an outer ring, are separated in the circular staggered distributed electrodes. Since the sensor only requires an electrical signal input and has relatively low requirements for parameters such as voltage and power, while the energy source needs a higher output power to supply the energy storage capacitor. Considering that the output voltage and power of the triboelectric nanogenerator have a linear proportional relationship with the electrode area, the inner ring electrodes are designed as the signal source of the sensor itself, and the outer ring electrodes are designed as the energy source for sensor signal processing. The power supply obtained through the outer ring electrodes is used to supply power to components such as the minimum system of the single-chip microcomputer and the 2.4G wireless transceiver module, which can effectively reduce the volume of the sensor and improve the integration of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The schematic embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation of the present application. In the drawings:

[0030] Figure 1 is a three-dimensional structural schematic diagram of the present invention;

[0031] Figure 2 is an exploded structural schematic diagram of the present invention;

[0032] Figure 3 is an exploded structural schematic diagram of the invention

[0033] Figure 4 is a cross-sectional view of the present invention;

[0034] Figure 5 is an enlarged view of this cross-sectional view;

[0035] Figure 6 is a front view of the electrode;

[0036] Figure 7 is a signal processing flow chart of the triboelectric passive wireless rotational speed sensor;

[0037] Figure 8 is a working principle schematic diagram of the grease-lubricated triboelectric passive wireless rotational speed sensor according to an embodiment of the present invention;

[0038] Figure 9 is a signal time-domain waveform diagram of the output voltage of the triboelectric rotational speed sensor under grease lubrication and dry friction conditions;

[0039] Figure 10 is a circuit schematic diagram including a signal processing circuit and a power management circuit;

[0040] Figure 11 is a schematic diagram of the slip rate of a rolling bearing under different rotational speed and load conditions. Specific Embodiments

[0041] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments of this application and the corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts belong to the scope of protection of this application.

[0042] The following will detail the technical solutions provided by each embodiment of this application with reference to the drawings.

[0043] Please refer to Figures 1-11 , the present invention provides a technical solution for a grease-lubricated triboelectric passive wireless rotational speed sensor for bearing slip monitoring:

[0044] A grease-lubricated triboelectric passive wireless rotational speed sensor for bearing slip monitoring includes two bearing housing covers 2, a bearing cage 9, a triboelectric nanogenerator, a signal processing module, and a power management module. Among them, there are two bearing housing covers 2 for installing a bearing body 1. A rotating shaft 5 is sleeved on the inner ring of the bearing body 1. The triboelectric nanogenerator is composed of a rotor unit 3 and a stator unit 4.

[0045] The rotor unit 3 includes a connecting member 31. A boss 33 is provided on the side of the connecting member 31 close to the bearing, and a rotor body 32 is provided on the side of the connecting member 31 away from the bearing. The rotor unit 3 is snap-fitted with the bearing cage 9 through the boss 33, and the two achieve an interference fit. A positioning boss 33 is machined on the connecting member 31 to ensure the concentricity of the rotor unit 3 and the rotating shaft 5, and it can also achieve the consistency of the movement of the rotor unit 3 and the bearing cage 9 without damaging the structure of the cage 9. The rotating shaft 5 can drive the cage and the rotor unit 3 to rotate in sequence to output electrical energy. The rotor body 32 is a rotationally arrayed distribution of metal electrodes.

[0046] The stator unit 4 includes a stator end cover 41. A stator body 42 is fixedly connected inside the stator end cover 41 through a high-temperature adhesive. The stator body 42 is a rotationally arrayed and staggered distribution of metal electrodes. A polymer film 6 is spin-coated on the stator body 42. When the rotor unit 3 starts, the metal electrodes on its end face contact and rub against the polytetrafluoroethylene to generate an electrical signal, thereby inducing a potential difference between the staggered metal electrodes on the end face of the stator unit.

[0047] Specifically, by setting the rotor unit 3 and the stator unit 4 and using the bearing cage to drive the rotation of the rotor unit 3, wireless real-time monitoring of the slipping state of the bearing body 1 in the compact space inside the transmission system can be achieved without relying on an external power source, improving the working reliability of the mechanical equipment and the intelligent operation and maintenance level, and further ensuring the high-performance operation of the high-end equipment.

[0048] As Figure 6 shown, the rotor body 32 and the stator body 42 have the same structure, both including an inner ring electrode and an outer ring electrode. The inner ring electrode serves as the signal source of the sensor itself, and the outer ring electrode serves as the energy source for sensor signal processing.

[0049] A grease with a low dielectric constant and low consistency is added between the rotor body 32 and the polymer film 6. The grease can reduce the wear of the triboelectric nanogenerator while further increasing the output charge of the triboelectric nanogenerator, ensuring the stability of the cage slipping state monitoring under passive conditions. Furthermore, the service life of the sensor and the power supply level are synchronously improved under passive conditions. As Figure 9 shown, the time-domain waveforms of the open-circuit voltages of the triboelectric nanogenerators for sensing and power supply under dry friction and grease lubrication conditions are respectively tested. It can be seen that after adding the grease with a low dielectric constant, the electrical output of the triboelectric nanogenerator can be increased by about 2 times at most; the open-circuit voltage of the triboelectric nanogenerator for power supply is 2.5 times that of the triboelectric nanogenerator for sensing.

[0050] A sealing end cover 7 is fixedly connected to the outer ring of the bearing body 1. The stator end cover 41 is fixedly connected to the sealing end cover 7 by screws. A rubber gasket 8 is arranged between the sealing end cover 7 and the stator end cover 41. By adjusting the screwing length of the screws, the contact pressure between the stator unit 4 and the rotor unit 3 can be changed.

[0051] A sealing groove 71 is machined on the inner circumferential surface of the sealing end cover 7. Multiple sealing grooves form a labyrinth sealing structure. The sealing structure is suitable for non-contact sealing in a high-speed environment. The radius of the sealing groove is 0.8 mm, and the unilateral clearance from the connecting part 31 is 0.5 mm. The selected model of the bearing body 1 is a cylindrical roller bearing NUP2207 ECP, the outer diameter of the outer ring is 72 mm, and the outer diameter dimension of the sealing end cover 7 is the same as the outer diameter of the outer ring. The axial dimension of the entire sensor is 25.5 mm.

[0052] The signal processing module is integrated on the back of the stator body 42. The signal processing module is mainly composed of a waveform conversion circuit, a minimum single-chip microcomputer system, and a 2.4G wireless transceiver module. Among them, the schematic diagram of the waveform conversion circuit is as Figure 10As shown, the main function is to convert the triboelectric signal into a square wave signal. The specific signal processing flow is as follows: The hysteresis comparator in the waveform conversion circuit is used to convert the triboelectric signal into a square wave signal; then the single-chip microcomputer records a series of discrete time sequences corresponding to the pulse falling edge, and calculates the actual rotational speed of the cage according to the characteristic frequency of the discrete time sequence, and calculates the slip rate of the cage through the rotational speed of the bearing. Finally, the wireless transmission module is used to send the slip rate to the host computer. The function of the minimum system of the single-chip microcomputer is mainly to calculate the instantaneous angular velocity of the square wave signal; considering that most of the components in the bearing-rotor system are rotating parts, if the angular velocity signal is transmitted through wired connection, it is easy to cause potential safety hazards to the system. Therefore, the instantaneous angular velocity calculated by the microprocessor is transmitted through the 2.4G wireless module transceiver.

[0053] Specifically, the power management module is integrated on the back of the stator body 42, as Figure 7 shown, the power management module is designed based on voltage division comparison. Its function is to temporarily store the electrical energy generated by the triboelectric nanogenerator in the energy storage capacitor, and set the high and low threshold voltages when the switching MOS transistor conducts and cuts off through the voltage division circuit and hysteresis comparison. When the voltage across the energy storage capacitor is less than the high threshold voltage, the comparator outputs a high level, controlling the MOS transistor to cut off, and the load is not powered. When the voltage across the energy storage capacitor is greater than the high threshold voltage, the comparator outputs a low level, the MOS transistor conducts, and the energy storage capacitor supplies power to the rear-end load. When the load completes one operation, the energy of the energy storage capacitor is consumed. When the voltage across it is lower than the low threshold voltage, the comparator outputs a high level again, the MOS transistor cuts off, and the load is powered off. After multiple cycles, the load is powered on when the MOS transistor conducts and powered off when it cuts off, consuming the energy of the energy storage capacitor to complete a wireless transmission. Thus, on the premise of no external power supply, the sensor can continuously and stably monitor the slip of the bearing cage for a long time.

[0054] The power generation principle of the triboelectric rotational speed sensor proposed by the present invention is to convert the rotational energy of the bearing into electrical energy, as Figure 8 shown is the power generation principle diagram of the sensor for one operating cycle. When the bearing rotates, the cage drives the rotor unit to rotate, and relative movement occurs with the stator unit. The continuous friction between the metal electrodes of the rotor unit and the metal electrodes of the stator unit will generate triboelectric charges, and then induced charges will be generated on the staggered distributed metal electrodes of the stator unit. As the bearing continues to rotate, the induced charges alternate between the two electrodes, thus generating a periodic alternating current.

[0055] To implement the above embodiments, this embodiment also provides a method for detecting the slip of a bearing using a sensor, which specifically includes the following steps:

[0056] S1, the triboelectric signal generated by the mutual friction of the stator unit and the rotor unit under the action of grease lubrication;

[0057] S2. The signal processing module calculates the actual rotational speed of the cage according to the characteristic frequency of the extracted triboelectric signal. The calculation is as follows:

[0058] n c = 60f sig / N

[0059] where n c is the actual rotational speed of the cage, f sig is the frequency of the triboelectric signal, and N is the number of groups of interleaved metal electrodes of the triboelectric nanogenerator.

[0060] S3. The signal processing module calculates the theoretical rotational speed of the cage according to the rotational speed formula of the inner ring of the rolling bearing and the rotational speed of the cage:

[0061]

[0062] where n 0 is the theoretical rotational speed of the cage, n i is the rotational speed of the inner ring of the bearing, D w is the diameter of the ball, D pw is the pitch diameter of the bearing, and α b is the contact angle of the bearing.

[0063] S4. Using the single-chip microcomputer minimum system in the signal processing module, calculate the slip rate of the cage according to the actual rotational speed and the theoretical rotational speed of the cage:

[0064]

[0065] where n 0 and n c are respectively the theoretical rotational speed and the actual rotational speed of the cage under pure rolling conditions.

[0066] As Figure 11 shown in the overall slip rate of the bearing measured by the triboelectric sensor in this embodiment under different rotational speed and load conditions, it can be seen that the slip rate is higher under high-speed and light-load conditions.

[0067] The resistance value of the load resistor in the waveform conversion circuit is 20 MΩ. The basis for the value is that when the load resistor is greater than 20 MΩ, the output voltage of the triboelectric nanogenerator basically remains unchanged.

[0068] The fixed-angle timing method is used to extract the frequency of the analog signal, that is, the rising edge of the square wave signal is counted within a specified time, and the signal frequency is obtained through the count value and the set time, and then the instantaneous rotational speed of the cage is calculated.

[0069] The 0 Ω resistor is used to complete the jumper so that all wiring is implemented on the top layer. Since the pin-type components will generate vias that affect the bottom layer, all components are of the surface-mount type.

[0070] It should also be noted that the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, such that a process, method, commodity or device comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or further includes elements inherent to such process, method, commodity or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, commodity or device comprising the said element.

[0071] The above description is only for the embodiments of the present application and is not intended to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the scope of the claims of the present application.

Claims

1. A grease-lubricated triboelectric passive wireless speed sensor for bearing slip monitoring, characterized in that: The invention comprises a bearing seat cover (2), a bearing retainer (9), a friction nanogenerator, a signal processing module and a power management module, wherein the bearing seat cover (2) has two parts and is used to install a bearing body (1); the inner ring of the bearing body (1) is sleeved with a rotating shaft (5); and the friction nanogenerator is composed of a rotor unit (3) and a stator unit (4).

2. The sensor according to claim 1, characterized in that The rotor unit (3) comprises a connecting piece (31), a boss (33) is arranged on the side of the connecting piece (31) close to the bearing, and a rotor body (32) is arranged on the side of the connecting piece (31) away from the bearing. The rotor unit (3) is engaged with the bearing retainer (9) via the boss (33), and the two achieve interference fit.

3. The sensor according to claim 1, characterized in that The stator unit (4) comprises a stator end cover (41), a stator body (42) is fixedly connected to the stator end cover (41) by means of high temperature glue, the stator body (42) is a rotating array of staggered metal electrodes, and a polymer film (6) is spin-coated on the stator body (42).

4. The sensor according to claim 3, characterized in that The rotor body (32) and the stator body (42) have the same structure, and both include an inner ring electrode and an outer ring electrode. The inner ring electrode serves as a signal source of the sensor itself, and the outer ring electrode serves as an energy source for sensor signal processing.

5. The sensor according to claim 3, characterized in that Lubricating grease with low dielectric constant and low viscosity is added between the rotor body (32) and the polymer film (6).

6. The sensor according to claim 1, characterized in that The outer ring of the bearing body (1) is fixedly connected to a sealing end cover (7), the stator end cover (41) is fixedly connected to the sealing end cover (7) by means of screws, and a rubber gasket (8) is provided between the sealing end cover (7) and the stator end cover (41).

7. The sensor according to claim 1, characterized in that The signal processing module is integrated on the back side of the stator body (42); and the power management module is integrated on the back side of the stator body (42).

8. A method for detecting bearing slippage using a sensor as claimed in any one of claims 1 to 7, characterized in that: The specific steps include: S1, a triboelectric signal generated by the friction between the stator unit and the rotor unit under grease lubrication; S2, the signal processing module calculates the actual rotation speed of the cage according to the characteristic frequency of the extracted triboelectric signal; S3, the signal processing module calculates the theoretical rotation speed of the cage according to the inner ring rotation speed of the rolling bearing and the cage rotation speed calculation formula; S4, using the single chip microcomputer minimum system in the signal processing module to calculate the slip rate of the cage according to the actual rotation speed of the cage and the theoretical rotation speed of the cage.

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