CN110208167A - A kind of lubricant oil metal wear particle detection device that can distinguish bubble and detection method - Google Patents

Abstract

The invention discloses a kind of lubricant oil metal wear particle detection devices that can distinguish bubble, including the three solenoid sensor being mounted on lubricating oil transmission pipeline and capacitance sensor；The central axis of lubricating oil conveyance conduit, three solenoid sensor and capacitance sensor three is conllinear；Three solenoid sensor is connected with for detecting the first signal conditioning module for incuding solenoidal induced electromotive force, and capacitance sensor is made of capacitor positive electrode, capacitor negative electrode and capacitor protective layer, when installation, capacitor negative electrode ground connection；Capacitance sensor is connected with the second signal conditioning module of the capacitance for detecting capacitance sensor by triaxial cable, voltage signal after conversion is exported and gives AD acquisition module by the first and second signal conditioning module, while then realizing accurate detection using size of the computing module to Metals In Lubricating abrasive grain, additionally it is possible to realize the differentiation of non-ferromagnetic abrasive grain and bubble.

Description

Lubricating oil metal abrasive particle detection device and detection method capable of distinguishing air bubbles

technical field

The invention relates to the field of detection of lubricating oil metal abrasive particles, in particular to a method and device for detecting lubricating oil metal abrasive particles capable of distinguishing air bubbles.

Background technique

Equipment lubricating oil often carries a large amount of equipment wear information. By detecting the lubricating oil flowing in the equipment, people can indirectly extract equipment wear information, diagnose wear faults, and provide a basis for predicting wear trends and identifying wear patterns. At present, the traditional detection methods of metal abrasive particles in lubricating oil are mainly ultrasonic detection method, capacitance detection method and inductance detection method.

Ultrasonic testing is to detect the size and distribution of abrasive particles by using the scattering characteristics that will occur when the ultrasonic waves emitted by the sensor are emitted to the abrasive particles. It can distinguish air bubbles and water droplets in lubricating oil, and has a certain resolution for abrasive particles of different components. At the same time, the lubricating oil does not need to be pretreated, so as to realize online detection; however, the ultrasonic detection method can only detect the abrasive particles with a size smaller than 100 μm in the oil, but cannot identify whether the abrasive particles are metal abrasive particles or non-metallic abrasive particles, thus It cannot provide more help for the analysis of the parts where the equipment fails and wears;

The capacitive detection method mainly uses a capacitive sensor to detect metal abrasive particles in the oil. The capacitive sensor is a sensor that converts the change of the measured non-electric quantity into the change of capacitance, but this method can only detect the change of iron powder content in the oil, and cannot detect the size of metal abrasive particles;

The inductance detection method mainly detects the size of the abrasive particles by detecting the change of the electric abrasive particles after the influence of the metal abrasive particles, but it is difficult to distinguish the ferromagnetic abrasive particles from the non-ferromagnetic abrasive particles, which is easy to cause misjudgment and "false alarm" .

Contents of the invention

Aiming at the above-mentioned prior art, the present invention designs a method and device for detecting metal abrasive particles in lubricating oil combined with capacitance detection technology and inductance detection technology. It is also possible to distinguish between non-ferromagnetic abrasive grains and air bubbles.

In order to solve the above technical problems and overcome the difficulty in distinguishing between air bubbles and non-ferromagnetic abrasive particles in the lubricating oil liquid in the prior art, a method and device based on combined measurement of a capacitance sensor and a three-solenoid sensor are provided, Realize the distinction between air bubbles and ferromagnetic abrasive particles.

A lubricating oil metal abrasive particle detection device capable of distinguishing air bubbles proposed by the present invention includes a three-solenoid sensor installed on a lubricating oil transmission pipeline, and a capacitive sensor is also installed on the lubricating oil transmission pipeline; the lubricating oil transmission pipeline The central axes of the oil delivery pipeline, the three-solenoid sensor and the capacitive sensor are collinear; the three-solenoid sensor is composed of a first excitation solenoid, a second excitation solenoid and an induction solenoid. The induction solenoid is connected with a first signal conditioning module, and the first signal conditioning module is used to detect the induced electromotive force of the induction solenoid, and convert it into a voltage signal and output it to an AD acquisition module; the capacitance sensor is composed of a capacitor The positive electrode, the negative electrode of the capacitor and the protective layer of the capacitor are composed. During installation, the negative electrode of the capacitor is grounded; the capacitive sensor is connected with a second signal conditioning module through a triaxial cable, and the second signal conditioning module is used to detect the capacitance the capacitance value of the sensor, and simultaneously convert the capacitance value into a voltage signal and output it to the AD acquisition module; air bubbles, and calculate the size of the metal abrasive grains; the calculation module transmits the calculation results to the host computer, and the host computer counts the metal abrasive grains according to the calculation results.

Further speaking, the present invention is capable of distinguishing the lubricating oil metal wear detection device for air bubbles, wherein the first excitation solenoid, the second excitation solenoid and the induction solenoid are along the three-solenoid sensor The position of the axis is placed; the number of turns of the first excitation solenoid and the second excitation solenoid are the same, the winding direction is opposite, and the coil axis length is the same, and the first excitation solenoid and the second excitation solenoid pass through alternating current Afterwards, they are connected in series and arranged symmetrically with the induction solenoid as the center.

Further speaking, the present invention is a lubricating oil metal abrasive detection device capable of distinguishing air bubbles, wherein, the capacitive protective layer and the capacitive negative electrode of the capacitive sensor surround the outer surface of the lubricating oil transmission pipeline, and the The capacitive protective layer is provided with a square hole axially arranged along the lubricating oil transmission pipeline, the axial length of the square hole in the lubricating oil transmission pipeline is equal to the length L of the positive electrode of the capacitor, and the positive electrode of the capacitor is embedded installed in the square hole.

The present invention prompts and proposes a detection method utilizing the above-mentioned lubricating oil metal abrasive particle detection device capable of distinguishing air bubbles, comprising the following steps:

The induction solenoid of the three-solenoid sensor is connected to the first signal conditioning module, and the first signal conditioning module detects the induced electromotive force of the induction solenoid, and converts it into a voltage signal and outputs it to the AD acquisition module ;

The capacitive sensor is connected to the second signal conditioning module through a triaxial cable, and the second signal conditioning module detects the capacitance value of the capacitive sensor, and at the same time, converts the capacitance value into a voltage signal and outputs it to the AD acquisition module;

The AD acquisition module transmits the acquisition result to the calculation module;

The calculation module distinguishes the metal abrasive grains and air bubbles in the lubricating oil transmission pipeline by detecting the capacitance change of the capacitive sensor and combining the inductance change of the three solenoid sensors, and calculates the size of the metal abrasive grains;

The calculation module transmits the calculation result to the host computer, and the host computer counts the metal abrasive particles according to the calculation result.

Further, in the lubricating oil metal abrasive particle detection method capable of distinguishing air bubbles of the present invention,

When metal abrasive grains enter the first excitation solenoid or the second excitation solenoid, assuming that the metal abrasive grains are all standard spherical, the number of turns of the first excitation solenoid and the second excitation solenoid are the same and The winding direction is opposite and the coil axis length is the same, the inductance variation of the first excitation solenoid or the second excitation solenoid is:

Among them, μ ₁ is the relative magnetic permeability of metal abrasive grains, r _d is the radius of metal abrasive grains, N ₁ is the number of turns of the first excitation solenoid or the second excitation solenoid coil, l ₁ is the first excitation solenoid The coil axis length of the tube or the second excitation solenoid, μ ₀ is the vacuum magnetic permeability; the inductance change rate is:

Among them, L _c is the original inductance of the induction solenoid, and L' _c is the inductance after the induction solenoid changes;

If the metal abrasive grains are ferromagnetic metal abrasive grains, the amplitude of the output signal of the induction solenoid is proportional to the size of the metal abrasive grains, the amplitude V _L of the output signal of the induction solenoid, and the expression of V _L is:

In the formula, M and B are constants, and then by measuring the size of V _L , the size of the ferromagnetic abrasive grain can be measured;

If the metal abrasive grains are non-ferromagnetic metal abrasive grains, the induced electromotive force expression of the induction solenoid (9) is:

Among them, K is a constant, v is the flow rate of lubricating oil; μ ₁ is the relative magnetic permeability of metal abrasive grains, r _d is the radius of metal abrasive grains.

Further, in the method for detecting metal abrasive particles in lubricating oil that can distinguish air bubbles in the present invention, the calculation module distinguishes metal abrasive particles and air bubbles in the lubricating oil transmission pipeline, and the specific process of calculating the size of the metal abrasive particles is as follows:

If the capacitance value of the capacitive sensor decreases, there are air bubbles passing through the lubricating oil transmission pipeline;

If the capacitance value of the capacitive sensor increases, and the output signal of the three-solenoid sensor first increases and then decreases, metal abrasive grains pass through the lubricating oil transmission pipeline, and the metal abrasive grains are ferromagnetic metal abrasive grains , calculate the diameter of this metal abrasive grain according to formula (2);

If the capacitance value of the capacitive sensor increases, and the output signal of the three-solenoid sensor first decreases and then increases, there are metal abrasive particles passing through the lubricating oil transmission pipeline, and the metal abrasive particles are non-ferromagnetic metal abrasive particles. Grains, according to the formula (3) to calculate the diameter of the metal abrasive grains.

Compared with prior art, the beneficial effect of the present invention is:

(1) The present invention and the device combine capacitance detection technology and inductance detection technology, which solves the difficult problem of distinguishing air bubbles and ferromagnetic abrasive particles by traditional methods, and makes the final detection result more accurate;

(2) The capacitive sensor designed by the present invention and device is different from the traditional sensor with only positive and negative electrodes, and is composed of positive electrode, negative electrode and protective layer; based on the special structure of the capacitive sensor in the inventive method and device, the capacitive The capacitance value of the sensor is only related to the length of the sensor electrode, which greatly reduces the error caused by sensor installation and production;

Description of drawings

Fig. 1 shows the main functional block diagram of lubricating oil metal abrasive particle detection method and device of the present invention;

Fig. 2-1 is the side view of capacitive sensor structure in the present invention;

Figure 2-2 is a schematic cross-sectional view of the capacitive sensor structure shown in Figure 2-1;

Fig. 2-3 is a schematic axial cross-sectional view of the capacitive sensor structure shown in Fig. 2-1.

In the figure: 1-capacitor positive electrode; 2-capacitor protective layer; 3-capacitor negative electrode; 4-capacitance sensor; 5-lubricating oil delivery pipeline; 6-metal abrasive particles; Tube; 9-induction solenoid; 10-first excitation solenoid; 11-three solenoid sensors; 12-triaxial cable; 13-second signal conditioning module; 14-first signal conditioning module; 15 -AD acquisition module; 16-calculation module; 17-host computer.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but the following embodiments in no way limit the present invention.

Generally, metal abrasive particles in lubricating oil delivery pipelines are divided into two types, namely metal ferromagnetic abrasive particles and metal non-ferromagnetic abrasive particles. In addition, there are air bubbles in the lubricating oil liquid, which will affect the detection results of metal abrasive particles.

As shown in Figure 1, a kind of lubricating oil metal abrasive particle detecting device that the present invention proposes can distinguish air bubbles, comprises three solenoid sensors 11 and a capacitive sensor 4 that are installed on the lubricating oil transmission pipeline 5; The central axes of the conveying pipeline 5 , the three solenoid sensors 11 and the capacitive sensor 4 are collinear.

The three-solenoid sensor 11 is composed of a first excitation solenoid 8, a second excitation solenoid 10 and an induction solenoid 9, and the first excitation solenoid 10, the second excitation solenoid 8 and the The induction solenoid 9 is placed along the axis position of the three solenoid sensor 11; the number of turns of the first excitation solenoid 8 and the second excitation solenoid 10 are the same and the winding direction is opposite, and the first The first excitation solenoid 10 and the second excitation solenoid 8 are connected in series after alternating current and placed symmetrically with the induction solenoid 9 as the center. The induction solenoid 9 is connected with a first signal conditioning module 14, the first signal conditioning module 14 is used to detect the induced electromotive force of the induction solenoid 9, and convert it into a voltage signal and output it to an AD acquisition module 15 .

As shown in Fig. 2-1, Fig. 2-2 and Fig. 2-3, the capacitive sensor 4 in the present invention is composed of a capacitive positive electrode 1, a capacitive negative electrode 3 and a capacitive protective layer 2, and the capacitive protective layer 2 and the capacitor negative electrode 3 surrounds the outer surface of the lubricating oil transmission pipeline 5, the capacitor protection layer 2 is provided with a square hole arranged axially along the lubricating oil transmission pipeline 5, and the square hole is located on the The axial length of the lubricating oil transmission pipeline 5 is equal to the length L of the capacitor positive electrode 1, and the capacitor positive electrode is embedded in the square hole. During installation, the capacitance negative electrode 3 is grounded; the capacitance sensor 4 is connected with a second signal conditioning module 13 through a triaxial cable 12, and the second signal conditioning module 13 is used to detect the capacitance value of the capacitance sensor 4, and simultaneously The capacitance value is converted into a voltage signal and output to the AD acquisition module 15; the AD acquisition module 15 transmits the acquisition result to the calculation module 16, and the calculation module 16 is used to distinguish the metal abrasive particles 6 and the bubbles 7, and calculate the size of the metal abrasive grains 6; the calculation module 16 transmits the calculation results to the host computer 17, and the host computer 17 counts the metal abrasive grains 6 according to the calculation results.

Utilize the detection method of the lubricating oil metal abrasive particle detecting device that can distinguish air bubble that the present invention proposes, comprise the following steps:

The induction solenoid 9 of the three-solenoid sensor 11 is connected with the first signal conditioning module 14, and the first signal conditioning module 14 detects the induced electromotive force of the induction solenoid 9 and converts it into a voltage signal Output to the AD acquisition module 15;

The capacitive sensor 4 is connected with the second signal conditioning module 13 through the triaxial cable 12, and the second signal conditioning module 13 detects the capacitance value of the capacitive sensor 4, and at the same time, converts the capacitance value into a voltage signal and outputs it to the AD acquisition module 15;

The AD acquisition module 15 transmits the acquisition result to the calculation module 16;

The calculation module 16 distinguishes the metal abrasive particles 6 and air bubbles 7 in the lubricating oil transmission pipeline 5 by detecting the capacitance change of the capacitive sensor 4 and combining the inductance change of the three-solenoid sensor 11, and calculates the metal abrasive particle 6 sizes;

The calculation module 16 transmits the calculation result to the host computer 17, and the host computer 17 counts the metal abrasive particles according to the calculation result.

When no metal abrasive particles pass through the three-solenoid sensor 11, assuming that the radius of the lubricating oil delivery pipeline 5 is far less than the length of all solenoid axes, the first excitation solenoid 10 and the second excitation solenoid 8 produce The magnetic field can be expressed as:

In the formula, μ ₀ is the vacuum magnetic permeability, and l ₁ is the axial length of the exciting solenoid. Therefore, the magnetic fields produced by the first excitation solenoid 10 and the second excitation solenoid 8 are equal in magnitude and reverse, and cancel each other at the induction solenoid 9 in the middle. At this time, the induction solenoid 9 in the middle is in the In zero magnetic field, the induced electromotive force is zero.

When the metal abrasive grain 6 enters the first excitation solenoid 10 or the second excitation solenoid 8, the entry of the metal abrasive grain 6 will cause a change in the magnetic induction intensity, thereby making the first excitation solenoid 10 or the second excitation solenoid 8 The local inductance of the solenoid 8 changes, assuming that the metal abrasive particles 6 are standard spherical, the number of coil turns of the first excitation solenoid 10 and the second excitation solenoid 8 are the same, and the coil axial lengths are the same, the first excitation The amount of inductance variation of the solenoid 10 or the second excitation solenoid 8 is:

Among them, μ ₁ is the relative magnetic permeability of metal abrasive grains, r _d is the radius of metal abrasive grains, N ₁ is the number of coil turns of the first excitation solenoid 10 or the second excitation solenoid 8, l ₁ is the first excitation The coil axis length of the solenoid 10 or the second excitation solenoid 8, μ ₀ is the vacuum magnetic permeability; then the rate of change of the inductance caused by the entry of the metal abrasive grain 6 or the air bubble 7 is:

Wherein, _{Lc is the original inductance of the induction solenoid (9), and L'c is} the changed inductance of the induction solenoid (9);

If the metal abrasive grains are ferromagnetic metal abrasive grains, the magnetic permeability is far greater than 1, the amplitude of the output signal of the induction solenoid 9 is proportional to the size of the metal abrasive grains, and the output signal of the induction solenoid 9 is proportional to the size of the metal abrasive grains. Amplitude V _L , the expression of V _L is:

In the formula, M and B are constants, and then by measuring the size of V _L , the size of the ferromagnetic abrasive grain can be measured;

For air bubbles, when air bubbles 7 enter the first excitation solenoid 10 or the second excitation solenoid 8, in addition to causing changes in inductance, capacitance will also be generated between the solenoid, and the transformation of capacitance and inductance will act on The first signal conditioning module 14 causes the signal conditioning module to output a pulse signal similar to that of ferromagnetic abrasive grains; thus making it difficult to distinguish ferromagnetic abrasive grains 6 from air bubbles 7 .

For non-ferromagnetic abrasive grains, in the present invention, the eddy current loss generated when the non-ferromagnetic metal abrasive grains 6 pass through the solenoid is used as the basis for determining the size of the abrasive grains, and the relationship between the output signal and the size of the abrasive grains is obtained. The metal abrasive grains 6 all have resistance, so when the eddy current phenomenon occurs, a part of the electromagnetic energy will be consumed. If the metal abrasive grains 6 are non-ferromagnetic metal abrasive grains, the expression of the induced electromotive force of the induction solenoid 9 is :

Among them, K is a constant, v is the flow rate of lubricating oil; μ ₁ is the relative magnetic permeability of metal abrasive particles, when the flow rate of lubricating oil v and the relative magnetic permeability μ ₁ of metal abrasive particles are known, it can be determined that the nonferrous The diameter r _d of magnetic metal abrasive grains.

In the present invention, the capacitance negative electrode 3 of the capacitance sensor 4 is grounded; when no metal abrasive particles 6 or bubbles 7 pass through the capacitance sensor 4, the capacitance value

In the formula, K is a constant, L is the length of the positive electrode of the capacitor, and ε is the dielectric constant; the gap between the positive electrode, the negative electrode and the protective layer of the capacitor can be considered to be infinitely small. At this time, according to the electrostatic principle of the calculation capacitor, the positive The capacitance between the electrode and the negative electrode has nothing to do with the electrode shape and the distance between the plates, and the capacitance is only related to the length L of the plates; therefore, the capacitance structure can effectively avoid the influence of installation errors and sensor processing errors on the measurement results.

For metal abrasive grains, whether they are ferromagnetic abrasive grains or non-ferromagnetic abrasive grains, after they enter the capacitive sensor 4, they will cause the increase of the dielectric constant ε, and then cause the increase of the capacitance value C of the capacitive sensor; while the air bubbles 7 The entry of , will cause the reduction of the dielectric constant ε, which in turn will cause the reduction of the capacitance C of the capacitive sensor.

In the present invention, the calculation module 16 can determine the metal abrasive particles 6 and air bubbles 7 in the lubricating oil transmission pipeline 5 by detecting the capacitance change of the capacitance sensor 4 and combining the inductance change of the three solenoid sensor 11, and The specific process of calculating the size of metal abrasive particles is as follows:

If the capacitance value of the capacitive sensor 4 decreases, the air bubbles 7 pass through the lubricating oil transmission pipeline 5, and no size calculation is required.

If the capacitance value of the capacitive sensor 4 increases, and the output signal of the three-solenoid sensor 11 first increases and then decreases, there are metal abrasive particles 6 passing through the lubricating oil transmission pipeline 5, and the metal abrasive particles are iron For magnetic metal abrasive grains, the diameter of the metal abrasive grains is calculated according to formula (2).

If the capacitance value of the capacitive sensor 4 increases, and the output signal of the three-solenoid sensor 11 first decreases and then increases, there are metal abrasive particles 6 passing through the lubricating oil transmission pipeline 5, and the metal abrasive particles are non-conductive. For ferromagnetic metal abrasive grains, the diameter of the metal abrasive grains is calculated according to formula (3).

Although the present invention has been described above in conjunction with the accompanying drawings, the present invention is not limited to the above-mentioned specific embodiments, and the above-mentioned specific embodiments are only illustrative, rather than restrictive. Under the enlightenment of the present invention, many modifications can be made without departing from the gist of the present invention, and these all belong to the protection of the present invention.

Claims (6)

1. a kind of lubricant oil metal wear particle detection device that can distinguish bubble, including being mounted on lubricating oil transmission pipeline (5) Three solenoid sensor (11), it is characterised in that:

A capacitance sensor (4) is also equipped on the lubricating oil transmission pipeline (5)；The lubricating oil conveyance conduit (5), three The central axis of solenoid sensor (11) and capacitance sensor (4) three are conllinear；

The three solenoid sensor (11) is by the first excitation solenoid (10), the second excitation solenoid (8) and induction solenoid (9) it forms, the induction solenoid (9) is connected with the first signal conditioning module (14), and the first signal conditioning module (14) is used for The induced electromotive force of induction solenoid (9) is detected, and is converted into voltage signal and exports to an AD acquisition module (15)；

The capacitance sensor (4) is made of capacitor positive electrode (1), capacitor negative electrode (3) and capacitor protective layer (2), when installation, Capacitor negative electrode (3) ground connection；The capacitance sensor (4) is connected with second signal by triaxial cable (12) and improves mould Block (13), the second signal conditioning module (13) are used to detect the capacitance of capacitance sensor (4), while capacitance being converted It exports for voltage signal to the AD acquisition module (15)；

Collection result is transferred to computing module (16) by the AD acquisition module (15), is distinguished and is moistened using the computing module (16) Metal worn particle and bubble in lubricating oil conveyance conduit (5), and calculate the size of metal worn particle；The computing module (16) will count It calculates result to be transferred to host computer (17), the host computer (17) counts metal worn particle according to calculated result.

2. the lubricant oil metal wear particle detection device of bubble can be distinguished according to claim 1, which is characterized in that described first It motivates solenoid (10), the second excitation solenoid (8) and incudes solenoid (9) along the three solenoid sensor (11) Axial location is placed；First excitation solenoid (10) and second motivates the number of turns of solenoid (8) identical and around to opposite, line It is identical to enclose axial length, connects after first excitation solenoid (10) and second excitation solenoid (8) indirect current and to incude spiral shell Spool is symmetrically placed centered on (9).

3. the lubricant oil metal wear particle detection device of bubble can be distinguished according to claim 1, which is characterized in that the capacitor Protective layer (2) and the capacitor negative electrode (3) are centered around on the outer surface of the lubricating oil transmission pipeline (5), and the capacitor is protected Sheath (2) is equipped with a square hole axially arranged along the lubricating oil transmission pipeline (5), and the square hole is in the lubricating oil transfer tube The axial length in road (5) is equal to the length L of the capacitor positive electrode (1), and the capacitor positive electrode is inlaid in the square hole.

4. a kind of lubricant oil metal wear particle detection method that can distinguish bubble, it is characterised in that: using as described in claim 1 It can distinguish the lubricant oil metal wear particle detection device of bubble, and the following steps are included:

The induction solenoid (9) of the three solenoid sensor (11) is connected with the first signal conditioning module (14), this first Signal conditioning module (14) detection it is described induction solenoid (9) induced electromotive force, and be converted into voltage signal export to AD acquisition module (15)；

The capacitance sensor (4) is connected by triaxial cable (12) with second signal conditioning module (13), second signal Conditioning module (13) detects the capacitance of the capacitance sensor (4), meanwhile, capacitance is converted into voltage signal and is exported to institute State AD acquisition module (15)；

Collection result is transferred to computing module (16) by the AD acquisition module (15)；

The computing module (16) passes through the capacitance variations of detection capacitance sensor (4), and in conjunction with the three solenoid sensor (11) inductance variation, distinguishes the metal worn particle and bubble in lubricating oil transmission pipeline (5), and calculate the big of metal worn particle It is small；

Calculated result is transferred to the host computer (17) by the computing module (16), and the host computer (17) is according to calculated result Metal worn particle is counted.

5. the lubricant oil metal wear particle detection method of bubble can be distinguished according to claim 4, it is characterised in that:

When metal worn particle enters in the first excitation solenoid (10) or the second excitation solenoid (8), it is assumed that metal worn particle is Standard is spherical, and first excitation solenoid (10) and second motivates the number of turns of solenoid (8) identical and around to opposite, coil axis Length is identical, the inductance variable quantity of first excitation solenoid (10) or the second excitation solenoid (8) are as follows:

Wherein, μ₁For the relative permeability of metal worn particle, r_dFor metal worn particle radius, N₁For the first excitation solenoid (10) or the Two excitation solenoid (8) coil turns, l₁For the coil axial length of the first excitation solenoid (10) or the second excitation solenoid (8), μ₀ For space permeability；Inductance change rate are as follows:

Wherein, L_cFor the former inductance of induction solenoid (9), L'_cFor the inductance after induction solenoid (9) variation；

If metal worn particle is feeromagnetic metal abrasive grain, the amplitude of described induction solenoid (9) output signal and the size of metal worn particle Size is directly proportional, incudes the amplitude V of solenoid (9) output signal_L, V_LExpression formula are as follows:

In formula, M, B are constant, and then pass through measurement V_LSize, the size of ferromagnetic grain can be measured；

If metal worn particle is non-ferromagnetic metal abrasive grain, the induced electromotive force expression formula of induction solenoid (9) are as follows:

Wherein, K is constant, and v is lubricating oil flow velocity；μ₁For the relative permeability of metal worn particle, r_dFor metal worn particle radius.

6. the lubricant oil metal wear particle detection method of bubble can be distinguished according to claim 5, it is characterised in that: the calculating Module (16) distinguishes the metal worn particle and bubble in lubricating oil transmission pipeline (5), and calculates the specific mistake of metal worn particle size Journey is as follows:

If capacitance sensor (4) capacitance reduces, there is bubble to pass through in lubricating oil transmission pipeline (5)；

If capacitance sensor (4) capacitance increases, and the output signal first increases and then decreases of the three solenoid sensor (11), Then there is metal worn particle to pass through in lubricating oil transmission pipeline (5), and the metal worn particle is feeromagnetic metal abrasive grain, according to formula (1) Calculate the diameter of the metal worn particle；

If capacitance sensor (4) capacitance increases, and the output signal of the three solenoid sensor (11) first reduces and increases afterwards, Then there is metal worn particle to pass through in lubricating oil transmission pipeline (5), and the metal worn particle is non-ferromagnetic metal abrasive grain, according to formula (2) diameter of the metal worn particle is calculated.