Plug-in gearbox lubricating oil debris online monitoring sensor and monitoring method thereof

Abstract

The invention provides a plug-in gearbox lubricating oil debris on-line monitoring sensor and a monitoring method thereof, and relates to the field of sensors, the plug-in gearbox lubricating oil debris on-line monitoring sensor comprises an excitation coil and an induction coil, the excitation coil and the induction coil are wound on a silicon steel sheet in parallel, and the surface area of the excitation coil is larger than that of the induction coil; the excitation coil and the induction coil have the same inductance value and have the same LC resonant frequency after being connected in parallel with the same capacitor, a cylindrical magnetic field shielding cover is arranged outside the induction coil, a plurality of through holes for particles to pass through are formed in the magnetic field shielding cover, and the induction coil can generate modulation signals carrying particle information and output the modulation signals to a processing circuit. And a processing circuit is used for extracting a particle modulation signal in the oil. The excitation coil and the induction coil are installed on the silicon steel sheet, the silicon steel sheet soft magnetic material is adopted to replace a permanent magnet, the magnetic field is weak, particles are not adsorbed, the sensor can work for a long time and does not need to be cleaned, and the service life of the whole sensor can be prolonged.

Description

Technical Field

[0001] The invention belongs to the field of sensors, and in particular relates to an insertable gearbox lubricating oil debris online monitoring sensor and a monitoring method thereof. Background Art

[0002] At present, many online lubricating oil dust sensors adopt the principle of three-coil modulation, which have high sensitivity and can detect ferromagnetic particles above 125um. However, they have limitations and must be installed in pipelines where oil flows. There is a demand for gearbox monitoring on the air or on the ground. In the gearbox, it is impossible to provide circulating oil. Based on this demand, this sensor was invented.

[0003] According to on-site feedback and technical data, the current magnetic plug-type debris monitoring sensor uses a permanent magnet structure and relies on permanent magnets to absorb particles for detection. During on-site work, the following problems may occur: 1) Personnel need to clean the absorbed debris regularly, sometimes multiple times a day; 2) The magnetic field of the permanent magnet is easily disturbed by the rotating gear set or metal components. In order to reduce the interference effect, the detection threshold needs to be increased, resulting in frequent missed detection of debris. 3) General permanent magnet magnetic plug-type sensors can only detect ferromagnetic metal debris, and cannot detect non-ferromagnetic metal debris, such as copper, aluminum, silver, etc.

[0004] Patent 202211706969.1-A high-precision magnetic plug-type wear particle sensor, which is essentially based on a permanent magnet structure and uses the symmetry of a bridge for amplification processing. 202410549337.1 A high-precision magnetic plug-type sensor provides a sensor that adopts a permanent magnet structure and consists of a larger excitation coil inner ring with several induction coils nested in it, and then uses a diode half-wave rectifier circuit for envelope detection. 201910183082.0 An inductive magnetic plug-type oil online monitoring device, a solenoid coil is wound on a permanent magnet, and then AC excitation is applied, and there is an excitation-detection unit detection method. 202111233711.X, a magnetic plug-type ferrous metal particle detection sensor, a magnetic plug-type balanced bridge measurement circuit. A measurement circuit based on a bridge structure is provided.

[0005] In summary, current technology can only detect metal debris, but cannot detect non-ferromagnetic metal debris, such as copper, aluminum, silver, etc. It is also inconvenient to clean, causing many inconveniences during use. Summary of the invention

[0006] In view of the deficiencies of the prior art, the present invention provides an online monitoring sensor for plug-in gearbox lubricating oil debris and a monitoring method thereof. The present invention can be used in gearboxes and other equipment without oil pipelines to perform online monitoring of plug-in lubricating oil debris. The excitation coil and the induction coil of the present invention are installed on silicon steel sheets, and the silicon steel sheet soft magnetic material is used to replace the permanent magnet. The magnetic field is weak and does not adsorb particles. It can work for a long time without cleaning, and can extend the service life of the overall sensor. At the same time, since ferromagnetic metal debris and non-ferromagnetic metal debris have different effects on the magnetic field, ferromagnetism enhances the magnetic field strength, and non-ferromagnetism reduces the magnetic field strength, the present invention can also detect non-ferromagnetic metal debris, has more usage scenarios, and can achieve long-term continuous online monitoring of lubricating oil debris in gearboxes and other equipment without oil pipelines.

[0007] To achieve the above object, the present invention discloses the following technical solution:

[0008] Specifically, on the one hand, the present invention provides an insertable gearbox oil debris online monitoring sensor, which can be inserted into a pipeline or an oil tank, and includes an excitation coil and an induction coil, which are wound in parallel on a silicon steel sheet, the surface area of ​​the excitation coil is larger than the surface area of ​​the induction coil, and the LC resonance frequency is the same after the excitation coil and the induction coil are connected in parallel with the same capacitance, a cylindrical magnetic field shielding cover is arranged outside the induction coil, and a plurality of through holes for particles to pass through are arranged on the magnetic field shielding cover, an excitation current flows in from a first end of the excitation coil, and a second end of the excitation coil is connected to a first end of the induction coil, and when the particles pass through the magnetic field shielding cover, they enter the interior of the magnetic field shielding cover with the help of the through holes, and the induction coil generates a modulation signal carrying particle information and outputs it to a processing circuit, and the particle modulation signal in the oil is extracted by the processing circuit, and the particle modulation signal is related to the particle size in the oil;

[0009] The processing circuit includes a primary amplification circuit, a demodulation circuit, a high-gain amplifier and a digital processing unit. The primary amplification circuit is used to preliminarily amplify the particle modulation signal. The demodulation circuit uses a multiplier or other phase-sensitive demodulation circuit to demodulate the amplified particle signal. The high-gain amplifier is used to perform secondary amplification on the demodulated particle signal. The digital processing unit performs digital filtering on the particle signal and calculates the amplitude of the metal particle signal and obtains the signal waveform generated when the particle passes through. The ferromagnetic and non-ferromagnetic signals are inverted, the ferromagnetic signal waveform is mt1, and the non-ferromagnetic particle signal waveform is -mt1.

[0010] When the excitation coil is working, it starts to resonate with the resonant circuit through the excitation circuit to form the excitation circuit carrier. The formula of the carrier H is as follows:

[0011] H=Asin(ωt+φ)

[0012] Among them, ωt is the frequency, A is the amplitude, and φ is the phase;

[0013] When particles pass through the induction coil, a particle modulation signal is generated for:

[0014]

[0015] Among them, mt1 is the waveform generated when the particle passes through, and the demodulated signal is obtained by phase demodulation.

[0016]

[0017] Further calculation yields:

[0018]

[0019] After low-pass filtering, we get:

[0020]

[0021] Finally, the waveform generated when the particles pass through is obtained. Due to different magnetic effects, ferromagnetic particles and non-ferromagnetic particles have opposite phases. The signal of ferromagnetic particles is mt1, and the signal of non-ferromagnetic particles is -mt1.

[0022] Preferably, the inductance value, LC resonant frequency and excitation current of the induction coil are adjusted according to specific requirements, and the sensitivity of the sensor can be adjusted by adjusting the inductance value of the induction coil.

[0023] Preferably, the magnetic field shield is provided with 4 through holes, and the diameter of the through holes is 6 mm-12 mm.

[0024] Preferably, the silicon steel sheet is a cylindrical structure.

[0025] Preferably, the diameter of the silicon steel sheet is 5 mm-20 mm, and the length of the silicon steel sheet is 30 mm-100 mm.

[0026] Preferably, the digital processing unit is a DSP processor or a FPGA processor.

[0027] Preferably, the LC resonant frequency is 100 kHz and the excitation current is 35 mA.

[0028] Preferably, the induction coil and the excitation coil are respectively connected with a capacitor to form LC parallel resonance.

[0029] On the other hand, the present invention provides a monitoring method based on the above-mentioned plug-in gearbox oil debris online monitoring sensor, which comprises the following steps:

[0030] S1, passing an excitation current, the excitation current flows into the first end of the excitation coil and further flows into the induction coil;

[0031] S2, when the particles pass through the magnetic field shield, they enter the magnetic field shield through the through hole, and the induction coil generates a modulated signal carrying the particle information and outputs it to the processing circuit;

[0032] S3, the processing circuit extracts the particle modulation signal in the oil;

[0033] S4. The primary amplifier circuit is used to preliminarily amplify the particle modulation signal. The demodulation circuit uses a multiplier or other phase-sensitive demodulation circuit to demodulate the amplified particle signal. The high-gain amplifier is used to secondary amplify the demodulated particle signal. The digital processing unit digitally filters the particle signal and calculates the amplitude of the metal particle signal to obtain the signal waveform generated when the particle passes through. The ferromagnetic and non-ferromagnetic signals are inverted. The ferromagnetic signal waveform is mt1, and the non-ferromagnetic particle signal waveform is -mt1.

[0034] Preferably, in step S4, the amplitude of the metal particle signal is calculated and the signal waveform generated when the particle passes through is obtained as follows:

[0035] When the excitation coil is working, it starts to resonate with the resonant circuit through the excitation circuit to form the excitation circuit carrier. The formula of the carrier H is as follows:

[0036] H=Asin(ωt+φ)

[0037] Among them, ωt is the frequency, A is the amplitude, and φ is the phase;

[0038] When particles pass through the induction coil, a particle modulation signal is generated for:

[0039]

[0040] Among them, mt1 is the waveform generated when the particle passes through, and the demodulated signal is obtained by phase demodulation.

[0041]

[0042] Further calculation yields:

[0043]

[0044] After low-pass filtering, we get:

[0045]

[0046] Finally, the waveform generated when the particles pass through is obtained. Due to different magnetic effects, ferromagnetic particles and non-ferromagnetic particles have opposite phases. The signal of ferromagnetic particles is mt1, and the signal of non-ferromagnetic particles is -mt1.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] (1) The present invention provides a high-sensitivity plug-in lubricating oil debris online monitoring sensor based on the principle of signal modulation, which is composed of an LC resonant excitation coil for providing a carrier and an induction coil for modulating signal output. The excitation coil and the induction coil are installed on a silicon steel sheet. The silicon steel sheet soft magnetic material is used to replace the permanent magnet. The magnetic field is weak and does not absorb particles. It can work for a long time and does not need to be cleaned. It is more convenient to use and can extend the service life of the overall sensor.

[0049] (2) The plug-in lubricating oil debris online monitoring sensor of the present invention adopts a silicon steel sheet structure and no longer uses permanent magnet adsorption. When the particles enter the magnetic field, the magnetic field of the excitation coil and the magnetic field generated by the particles act together and are modulated to the induction coil for output, assisted by the high-sensitivity processing circuit at the back end, and the metal debris particles are detected with higher accuracy. At the same time, since ferromagnetic metal debris and non-ferromagnetic metal debris affect the magnetic field differently, ferromagnetic particles can enhance the magnetic field strength, and non-ferromagnetic particles can reduce the magnetic field strength. Therefore, the present invention can also detect non-ferromagnetic metal debris and has more usage scenarios.

[0050] (3) In order to reduce the influence of moving metal components such as rotating gears of the gearbox on the sensor magnetic field, the online monitoring sensor of the present invention adds a magnetic field shielding cover on the top of the induction coil, which can reduce some external magnetic field interference, thereby ensuring that the monitoring results are more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is a schematic diagram of the sensor structure of the present invention;

[0052] Figure 2 It is a schematic diagram of the structure of the signal processing circuit of the present invention;

[0053] Figure 3 It is a schematic diagram of LC parallel resonance of the present invention;

[0054] Figure 4 It is a schematic diagram of the method flow of the present invention. DETAILED DESCRIPTION

[0055] The exemplary embodiments, features and aspects of the present invention will be described in detail below with reference to the accompanying drawings. The same reference numerals in the accompanying drawings represent elements with the same or similar functions. Although various aspects of the embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless otherwise specified.

[0056] The present invention provides an insertable gearbox oil debris online monitoring sensor, which can be inserted into a pipeline or an oil tank. Figure 1 As shown, it includes an excitation coil 2 and an induction coil 3, the excitation coil 2 and the induction coil 3 are wound in parallel on a silicon steel sheet 1, the surface area of ​​the excitation coil 2 is larger than the surface area of ​​the induction coil 3, the LC resonance frequency is the same after the excitation coil 2 and the induction coil 3 are connected in parallel with the same capacitance, a cylindrical magnetic field shielding cover 5 is arranged outside the induction coil 3, a plurality of through holes 4 for particles to pass through are arranged on the magnetic field shielding cover 5, an excitation current flows in from a first end of the excitation coil, a second end of the excitation coil is connected to a first end of the induction coil, when the particles pass through the magnetic field shielding cover 5, they enter the inside of the magnetic field shielding cover 5 with the help of the through holes, the induction coil 3 generates a modulation signal carrying particle information and outputs it to the processing circuit, the particle modulation signal in the oil is extracted by the processing circuit, and the particle modulation signal is related to the particle size in the oil.

[0057] The processing circuit includes a primary amplification circuit, a demodulation circuit, a high-gain amplifier and a digital processing unit. The primary amplification circuit is used to preliminarily amplify the particle modulation signal. The demodulation circuit uses a multiplier or other phase-sensitive demodulation circuit to demodulate the amplified particle signal. The high-gain amplifier is used to secondary amplify the demodulated particle signal. The digital processing unit digitally filters the particle signal and calculates the amplitude of the metal particle signal to obtain the signal waveform generated when the particle passes through. When the signal waveform is mt1, the particle is a ferromagnetic particle. When the signal waveform is -mt1, the particle is a non-ferromagnetic particle.

[0058] When the excitation coil is working, it starts to resonate with the resonant circuit through the excitation circuit to form the excitation circuit carrier. The formula of the carrier H is as follows:

[0059] H=Asin(ωt+φ)

[0060] Among them, ωt is the frequency, A is the amplitude, and φ is the phase.

[0061] When particles pass through the induction coil, a particle modulation signal is generated for:

[0062]

[0063] Among them, mt1 is the waveform generated when the particle passes through. Through phase demodulation, we can get:

[0064]

[0065] Further calculation:

[0066]

[0067] Since the frequency of cos 2ωt is relatively high, after low-pass filtering, we get:

[0068]

[0069] Finally, the mt1 waveform generated when the particles pass through is obtained. Due to different magnetic effects, ferromagnetic particles and non-ferromagnetic particles have opposite phases. The signal of ferromagnetic particles is mt1, and the signal of non-ferromagnetic particles is -mt1.

[0070] On the other hand, the present invention provides a monitoring method based on the above-mentioned plug-in gearbox oil debris online monitoring sensor, such as Figure 4 As shown, it includes the following steps:

[0071] S1. Apply an excitation current, which flows into the first end of the excitation coil and further flows into the induction coil.

[0072] S2. When the particles pass through the magnetic field shield, they enter the inside of the magnetic field shield through the through hole. The induction coil generates a modulated signal carrying the particle information and outputs it to the processing circuit.

[0073] S3. The processing circuit extracts the particle modulation signal in the oil.

[0074] S4. The primary amplifier circuit is used to preliminarily amplify the particle modulation signal. The demodulation circuit uses a multiplier or other phase-sensitive demodulation circuit to demodulate the amplified particle signal. The high-gain amplifier is used to secondary amplify the demodulated particle signal. The digital processing unit digitally filters the particle signal and calculates the amplitude of the metal particle signal to obtain the signal waveform generated when the particle passes through. The ferromagnetic and non-ferromagnetic signals are inverted. The ferromagnetic signal waveform is mt1, and the non-ferromagnetic particle signal waveform is -mt1.

[0075] Preferably, in step S4, the amplitude of the metal particle signal is calculated and the signal waveform generated when the particle passes through is obtained as follows:

[0076] When the excitation coil is working, it starts to resonate with the resonant circuit through the excitation circuit to form the excitation circuit carrier. The formula of the carrier H is as follows:

[0077] H=Asin(ωt+φ)

[0078] Among them, ωt is the frequency, A is the amplitude, and φ is the phase.

[0079] When particles pass through the induction coil, a particle modulation signal is generated for:

[0080]

[0081] Among them, mt1 is the waveform generated when the particle passes through, and the demodulated signal is obtained by phase demodulation.

[0082] Further calculation yields:

[0083]

[0084] After low-pass filtering, we get:

[0085]

[0086] Finally, the waveform generated when the particles pass through is obtained. Due to different magnetic effects, ferromagnetic particles and non-ferromagnetic particles have opposite phases. The signal of ferromagnetic particles is mt1, and the signal of non-ferromagnetic particles is -mt1. Specific embodiments

[0088] Specifically, the present invention provides an insertable gearbox oil debris online monitoring sensor that can be inserted into a pipeline or oil tank, such as Figure 1 As shown, it includes an excitation coil 2 and an induction coil 3, which are wound in parallel on a silicon steel sheet 1, and the silicon steel sheet 1 is a cylindrical structure. The diameter of the silicon steel sheet 1 is 5mm-20mm, and the length of the silicon steel sheet 1 is 30mm-100mm.

[0089] The surface area of ​​the excitation coil 2 is larger than that of the induction coil 3. The inductance of the excitation coil 2 and the induction coil 3 is the same and the LC resonant frequency is the same after the same capacitor is connected in parallel. The excitation coil and the induction coil adopt the method of LC parallel resonance with the capacitor, and the resonant frequency of the excitation coil and the induction coil must be the same. The sensitivity of the sensor to detect debris can be improved by adjusting the inductance value of the induction coil. Increasing the inductance value of the induction coil requires a corresponding reduction in the capacitance value of the resonant parallel connection to ensure that the resonant frequency of the excitation coil and the induction coil is the same. In another specific embodiment, the oscillating LC resonator can adopt a commonly used LC parallel resonant circuit such as an AC bridge, a triode circuit, and a transformer. A cylindrical magnetic field shielding cover is provided on the outside of the induction coil 3, and a plurality of through holes are provided on the magnetic field shielding cover for particles to pass through. In one embodiment, the magnetic field shielding cover is provided with 4 through holes, and the diameter of the through holes is 6mm-12mm. The excitation current flows into the first end of the excitation coil 2, and the second end of the excitation coil 2 is connected to the first end of the induction coil 3. When the particles pass through the magnetic field shielding cover, they enter the inside of the magnetic field shielding cover with the help of the through hole. The induction coil 3 generates a modulation signal carrying the particle information and outputs it to the processing circuit. The processing circuit is used to extract the particle modulation signal in the oil, and the particle modulation signal is related to the particle size in the oil.

[0090] The processing circuit includes a primary amplifier circuit, a demodulation circuit, a high-gain amplifier and a digital processing unit. The primary amplifier circuit is used to preliminarily amplify the particle modulation signal. The demodulation circuit uses a multiplier or other phase-sensitive demodulation circuit to demodulate the amplified particle signal. The high-gain amplifier is used to perform secondary amplification on the demodulated particle signal. The digital processing unit performs digital filtering on the particle signal and calculates the amplitude of the metal particle signal. The digital processing unit is a DSP processor or an FPGA processor. In specific applications, the inductance value, LC resonant frequency and excitation current of the induction coil 3 are adjusted according to specific needs. In a specific embodiment, the LC resonant frequency is 100kHz and the excitation current is 35mA. The LC resonance parameters are selected to be consistent to achieve a better resonant frequency. The magnetic field shielding cover is made of a conductor material with good conductivity to reduce the disturbance of the metal movement other than the metal chip particles on the magnetic field. The shielding cover has 4 through holes with a diameter of 6mm-12mm.

[0091] When the excitation coil 2 is working, it starts to resonate with the resonant circuit through the excitation circuit to form an excitation circuit carrier. The formula of the carrier H is as follows:

[0092] H=Asin(ωt+φ)

[0093] Where ωt is the frequency.

[0094] ωt is the frequency. The carrier frequency should be much higher than the frequency of particles. The general operating frequency is around 100kHz. When particles pass through, an amplitude modulation signal is generated. When particles pass through the induction coil, a particle modulation signal is generated. for:

[0095]

[0096] Among them, mt1 is the waveform generated when the particle passes through:

[0097]

[0098] Among them, mt1 is the impact of the particle passing through on the signal amplitude, the frequency is relatively low, due to the low energy utilization of the particle in the magnetic field, mt1 is much smaller than A, and the modulation index is relatively low. When the processing circuit is used for processing, the phase-sensitive demodulation method is adopted, and the functions with the same frequency and phase are multiplied.

[0099] By calculation:

[0100]

[0101] Since the frequency of cos 2ωt is relatively high, after low-pass filtering, we get:

[0102]

[0103] Finally, the mt1 waveform generated when the particles pass through is obtained. Due to different magnetic effects, ferromagnetic particles and non-ferromagnetic particles have opposite phases. The signal of ferromagnetic particles is mt1, and the signal of non-ferromagnetic particles is -mt1.

[0104] This embodiment provides a high-sensitivity plug-in type lubricating oil debris online monitoring sensor based on the signal modulation principle, such as Figure 1 As shown, the excitation coil 2 and the induction coil 3 are installed on the silicon steel sheet 1 using the same parameters and processes. According to Lenz's theorem, the direction of the induced current is opposite to the direction of the excitation current. The magnetic field shield 5 is installed outside the induction coil 3. The magnetic field shield 5 is provided with a plurality of large through holes 6 that allow particles to flow freely. When metal particles 4 enter the magnetic field shield 5 through the large through holes 6, they will interact with the magnetic field of the excitation coil 2 to generate a modulated signal, which is output through the induction coil 3 and then processed by a dedicated processing circuit.

[0105] like Figure 3 As shown, the excitation coil 2 and the capacitor 9 form an LC parallel resonance, and the induction coil 3 and the capacitor 10 form an LC parallel resonance. The resonance frequencies of the excitation coil 2 and the induction coil 3 must be the same, but the inductance values ​​of the excitation coil 2 and the induction coil 3 can be different. In specific applications, generally increasing the inductance value of the induction coil 3 can appropriately increase the sensitivity, so the inductance value of the induction coil 3 can be adjusted as needed.

[0106] like Figure 2 As shown, the processing circuit includes a primary amplification circuit, a demodulation circuit, a high-gain amplifier and a data processing unit, the primary amplification circuit includes an amplifier A, an amplifier B and a DC-blocking capacitor 7, the demodulation circuit includes a demodulator 8 and a low-pass filter, the high-gain amplifier includes a high-gain amplifier A and a high-gain amplifier B, and the data processing unit includes an ADC collector and a DSP data processor. Due to the divergence of the magnetic field, the modulation degree of the modulated signal in the induction coil 3 is relatively low. Amplifier A, the DC-blocking capacitor 7 and amplifier B perform primary amplification and shaping on the modulated signal. After passing through the demodulator 8 and low-pass filtering, the high-gain amplifier A and the high-gain amplifier B are used for high-gain amplification to improve sensitivity. The demodulator 8 can be composed of a multiplier or a phase-sensitive demodulator. The amplification multiples of the high-gain amplifier A and the high-gain amplifier B can be set to between 1000 times and 10000 times as required.

[0107] The diameter and length of the silicon steel sheet 1 can be configured according to actual conditions. Generally, the diameter can be set at about 10 mm, and the length can be set at about 50 mm. The excitation coil 2 and the induction coil 3 use copper enameled wire, and the copper diameter can be selected to be about 0.22 mm. The number of turns of the excitation coil 2 and the induction coil 3 can be equal under normal circumstances. In this embodiment, the number of turns of the excitation coil 2 and the induction coil 3 are both set to about 100 turns.

[0108] The present invention installs the excitation coil 2 and the induction coil 3 on the silicon steel sheet 1, and adopts the soft magnetic material of the silicon steel sheet to replace the permanent magnet. The magnetic field is weak, does not adsorb particles, can work for a long time, does not need to be cleaned, is more convenient to use, and can extend the service life of the overall sensor. When the particles enter the magnetic field, the magnetic field of the excitation coil and the magnetic field generated by the particles act together to modulate the induction coil to output the modulation signal, and the metal debris particles are detected with higher accuracy by means of the processing circuit. At the same time, since ferromagnetic metal debris and non-ferromagnetic metal debris have different effects on the magnetic field, ferromagnetic particles can enhance the magnetic field strength, and non-ferromagnetic particles can reduce the magnetic field strength. Therefore, the present invention can also detect non-ferromagnetic metal debris, and has more usage scenarios.

[0109] The above-described embodiments are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the scope of protection determined by the claims of the present invention.

Claims

1. An insertable gearbox oil debris online monitoring sensor, which can be inserted into a pipeline or oil tank, characterized in that: It includes an excitation coil and an induction coil, which are wound in parallel on a silicon steel sheet, the surface area of ​​the excitation coil is larger than that of the induction coil, the LC resonance frequency of the excitation coil and the induction coil after being connected in parallel with the capacitor is the same, a cylindrical magnetic field shielding cover is arranged outside the induction coil, a plurality of through holes for particles to pass through are arranged on the magnetic field shielding cover, an excitation current flows in from a first end of the excitation coil, a second end of the excitation coil is connected to a first end of the induction coil, when the particles pass through the magnetic field shielding cover, they enter the inside of the magnetic field shielding cover with the help of the through holes, the induction coil generates a modulation signal carrying particle information and outputs it to a processing circuit, the particle modulation signal in the oil is extracted by the processing circuit, and the particle modulation signal is related to the particle size in the oil; The processing circuit includes a primary amplification circuit, a demodulation circuit, a high-gain amplifier and a digital processing unit. The primary amplification circuit is used to preliminarily amplify the particle modulation signal. The demodulation circuit uses a multiplier or other phase-sensitive demodulation circuit to demodulate the amplified particle signal. The high-gain amplifier is used to secondary amplify the demodulated particle signal. The digital processing unit performs digital filtering on the particle signal and calculates the amplitude of the metal particle signal, and obtains the signal waveform generated when the particle passes through. The ferromagnetic and non-ferromagnetic signals are inverted. The ferromagnetic particle signal waveform is mt1, and the non-ferromagnetic particle signal waveform is -mt1. The waveform can be used to determine whether the particle is a ferromagnetic particle or a non-ferromagnetic particle. When the excitation coil is working, it starts to resonate with the resonant circuit through the excitation circuit to form an excitation circuit carrier. The formula of the carrier H is as follows: H=Asin(ωt+φ) Among them, ωt is the frequency, A is the amplitude, and φ is the phase; When particles pass through the induction coil, a particle modulation signal is generated for; Among them, mt1 is the waveform generated when the particle passes through, and the demodulated signal is obtained by phase demodulation. Further calculation yields: After low-pass filtering, we get: Finally, the waveform generated when the particles pass through is obtained. Due to different magnetic effects, ferromagnetic particles and non-ferromagnetic particles have opposite phases. The signal of ferromagnetic particles is mt1, and the signal of non-ferromagnetic particles is -mt1.

2. The plug-in gearbox oil debris online monitoring sensor according to claim 1 is characterized in that: The inductance value, LC resonant frequency and excitation current of the induction coil are adjusted according to specific needs. The sensitivity of the sensor can be adjusted by adjusting the inductance value of the induction coil.

3. The plug-in gearbox oil debris online monitoring sensor according to claim 1 is characterized in that: The magnetic field shield is provided with 4 through holes, and the diameter of the through holes is 6mm-12mm.

4. The plug-in gearbox oil debris online monitoring sensor according to claim 1, characterized in that: The silicon steel sheet is a cylindrical structure.

5. The plug-in gearbox oil debris online monitoring sensor according to claim 4 is characterized in that: The diameter of the silicon steel sheet is 5mm-20mm, and the length of the silicon steel sheet is 30mm-100mm.

6. The plug-in gearbox oil debris online monitoring sensor according to claim 1, characterized in that: The digital processing unit is a DSP processor or an FPGA processor.

7. The plug-in gearbox oil debris online monitoring sensor according to claim 2, characterized in that: The LC resonant frequency is 100kHz and the excitation current is 35mA.

8. The plug-in gearbox oil debris online monitoring sensor according to claim 1, characterized in that: The induction coil and the excitation coil are respectively connected with a capacitor to form LC parallel resonance.

9. A monitoring method based on the plug-in gearbox oil debris online monitoring sensor according to claim 1, characterized in that: It includes the following steps: S1, passing an excitation current, the excitation current flows into the first end of the excitation coil and further flows into the induction coil; S2, when the particles pass through the magnetic field shield, they enter the magnetic field shield through the through hole, and the induction coil generates a modulated signal carrying the particle information and outputs it to the processing circuit; S3, the processing circuit extracts the particle modulation signal in the oil; S4. The primary amplifier circuit is used to preliminarily amplify the particle modulation signal. The demodulation circuit uses a multiplier or other phase-sensitive demodulation circuit to demodulate the amplified particle signal. The high-gain amplifier is used to secondary amplify the demodulated particle signal. The digital processing unit digitally filters the particle signal and calculates the amplitude of the metal particle signal to obtain the signal waveform generated when the particle passes through. The ferromagnetic and non-ferromagnetic signals are inverted. The ferromagnetic signal waveform is mt1, and the non-ferromagnetic particle signal waveform is -mt1.

10. The monitoring method according to claim 9, characterized in that: In step S4, the amplitude of the metal particle signal is calculated and the signal waveform generated when the particle passes is obtained as follows: When the excitation coil is working, it starts to resonate with the resonant circuit through the excitation circuit to form an excitation circuit carrier. The formula of the carrier H is as follows: H=Asin(ωt+φ) Among them, ωt is the frequency, A is the amplitude, and φ is the phase; When particles pass through the induction coil, a particle modulation signal is generated for: Among them, mt1 is the waveform generated when the particle passes through, and the demodulated signal is obtained by phase demodulation. Further calculation yields: After low-pass filtering, we get: Finally, the waveform generated when the particles pass through is obtained. Due to different magnetic effects, ferromagnetic particles and non-ferromagnetic particles have opposite phases. The signal of ferromagnetic particles is mt1, and the signal of non-ferromagnetic particles is -mt1.

Images