Monitoring device and system for monitoring complex dielectric constant of lubricating oil based on impedance spectroscopy

Abstract

The utility model relates to the technical field of lubricating oil monitoring, in particular to a monitoring device for monitoring complex permittivity of lubricating oil based on impedance spectroscopy and a monitoring system for monitoring complex permittivity of lubricating oil based on impedance spectroscopy. A monitoring device for monitoring complex permittivity of lubricating oil based on impedance spectroscopy comprises a coaxial electrode sensor used for being in contact with the lubricating oil and converting electrical characteristics of the lubricating oil into electrical signals; the oscillating circuit is used for generating an alternating current signal within a specific frequency range for exciting the coaxial electrode sensor, and the oscillating circuit is provided with a coaxial electrode equivalent capacitor and a coaxial electrode equivalent resistor; the sampling circuit is used for collecting a signal output by the coaxial electrode sensor; and the signal processing circuit is used for calculating a real part and an imaginary part of the complex dielectric constant in the lubricating oil and judging the quality state of the lubricating oil according to a preset threshold value. According to the scheme, the monitoring sensitivity is high, and the quality change of the oil is reflected more comprehensively.

Description

Technical Field

[0001] The utility model relates to the technical field of lubricating oil monitoring, in particular to a monitoring device for monitoring the complex dielectric constant of lubricating oil based on impedance spectrum and a monitoring system for monitoring the complex dielectric constant of lubricating oil based on impedance spectrum. Background Art

[0002] The common dielectric constant sensor in the market is the real part of the complex dielectric constant, which is caused by various displacement polarizations inside the material and represents the energy storage term of the material. For example, the Chinese invention application with publication number CN109425557A discloses a system for monitoring the quality of cutting machine oil. The system monitors the oil quality by detecting the dielectric constant (real part of the complex dielectric constant). However, the sensors or detection elements involved in the system are insufficient in sensitivity and resolution, and cannot fully reflect the quality changes of the oil. Utility Model Content

[0003] The purpose of the utility model is to provide a monitoring device for monitoring the complex dielectric constant of lubricating oil based on impedance spectroscopy and a monitoring system for monitoring the complex dielectric constant of lubricating oil based on impedance spectroscopy in view of the shortcomings of the prior art, aiming to simultaneously monitor the real part and the imaginary part of the complex dielectric constant, that is, the dielectric constant and the dielectric loss, so as to have higher sensitivity than the prior art and more comprehensive reflection of the quality changes of the oil.

[0004] The utility model achieves the above-mentioned purpose through the following technical solutions: a monitoring device for monitoring the complex dielectric constant of lubricating oil based on impedance spectroscopy, comprising:

[0005] A coaxial electrode sensor, the coaxial electrode sensor is used to contact the lubricating oil and convert the electrical characteristics of the lubricating oil into an electrical signal;

[0006] An oscillating circuit, the oscillating circuit is used to generate an AC signal in a specific frequency range to excite the coaxial electrode sensor, the oscillating circuit having a coaxial electrode equivalent capacitance and a coaxial electrode equivalent resistance;

[0007] a sampling circuit, the sampling circuit being used to collect a signal output by the coaxial electrode sensor; and

[0008] A signal processing circuit is used to process the signal collected by the sampling circuit according to the impedance spectrum monitoring technology, calculate the real part of the complex dielectric constant matching the equivalent capacitance of the coaxial electrode and the imaginary part of the complex dielectric constant matching the equivalent resistance of the coaxial electrode in the lubricating oil, and judge the quality state of the lubricating oil according to a preset threshold value.

[0009] As a further solution of the utility model: the monitoring device for monitoring the complex dielectric constant of lubricating oil based on impedance spectroscopy also includes:

[0010] The temperature sensor is used to measure the temperature of the lubricating oil and perform temperature compensation on the measurement result.

[0011] As a further solution of the utility model: the coaxial electrode sensor comprises:

[0012] A coaxial electrode, wherein the coaxial electrode comprises an inner electrode and an outer electrode, wherein lubricating oil is filled between the inner electrode and the outer electrode; the inner electrode is a gold-plated electrode made of stainless steel, and the outer electrode comprises a stainless steel shell at the top and a mounting joint at the bottom, wherein the interior of the stainless steel shell is hollow with an inner cavity, and the inner electrode and the outer electrode constitute a coaxial electrode probe;

[0013] The monitoring device for monitoring the complex dielectric constant of lubricating oil based on impedance spectroscopy also includes:

[0014] A PCB board is arranged in the inner cavity, and the oscillation circuit and the sampling circuit are pre-placed on the PCB board;

[0015] an insulating bracket, disposed in the mounting joint; and

[0016] A sealing ring, sleeved on the insulating bracket;

[0017] Wherein, the temperature sensor is arranged in the mounting joint and is located on one side of the insulating bracket.

[0018] As a further solution of the utility model: the mounting joint comprises an integrally formed shell joint portion, a threaded connection portion and a probe shield portion, one end of the shell joint portion is coaxially connected to the bottom of the stainless steel shell, one end of the threaded connection portion is coaxially arranged at one end of the shell joint portion away from the stainless steel shell, and the probe shield portion is coaxially arranged at one end of the threaded connection portion away from the shell joint portion;

[0019] The inner electrode comprises a connecting rod portion and a probe portion which are coaxially integrally formed, wherein the probe portion is coaxially arranged in the probe shield portion, and an end of the connecting rod portion away from the probe portion extends close to the inner cavity;

[0020] The insulating bracket is sleeved on the connecting rod part, one end of the insulating bracket abuts against one end of the probe part close to the connecting rod part, and the other end of the insulating bracket abuts against the inner wall of the shell joint part; the sealing ring is tightened on one end of the insulating bracket close to the probe part;

[0021] An oil receiving space for receiving lubricating oil is formed between the probe shield portion, the probe portion and the insulating bracket.

[0022] As a further solution of the utility model: the monitoring device for monitoring the complex dielectric constant of lubricating oil based on impedance spectroscopy also includes a power supply circuit and a communication circuit, the PCB board includes a first board and a second board, the oscillation circuit and the sampling circuit are respectively pre-set on the first board, and the power supply circuit and the communication circuit are respectively pre-set on the second board;

[0023] The inner cavity is provided with fasteners connected to the first plate and the second plate respectively;

[0024] A cable connector connected to the communication circuit is arranged on the top of the stainless steel housing.

[0025] As a further solution of the utility model: the oscillation circuit adopts a Colpitts oscillation circuit, and the oscillation frequency range of the oscillation circuit is 1~10MHz.

[0026] As a further solution of the utility model: the oscillation circuit includes: a resistor R1, an inductor L, a capacitor C1, an equivalent capacitor C, an equivalent resistor ESR, a capacitor C2, a resistor R2, a VREF terminal, a VCC terminal, a first operational amplifier, a second operational amplifier, a resistor R3, and an output terminal OUT; wherein,

[0027] One end of the resistor R1 is connected to the +5V terminal, one end of the inductor L is connected to the other end of the resistor R1, one end of the capacitor C1 is connected to the other end of the inductor L, one end of the equivalent resistor ESR is connected to the other end of the capacitor C1, one end of the equivalent capacitor C is connected to the other end of the equivalent resistor ESR, and the other end of the equivalent capacitor C is grounded;

[0028] One end of the capacitor C2 is connected to the other end of the resistor R1, the other end of the capacitor C2 is connected to the first pin of the first operational amplifier, one end of the resistor R2 is connected to the VREF terminal, the other end of the resistor R2 is connected to the second pin of the first operational amplifier, the third pin of the first operational amplifier is connected to the other end of the inductor L, the fourth pin of the first operational amplifier is grounded, and the eighth pin of the first operational amplifier is connected to the VCC terminal;

[0029] The third pin of the second operational amplifier is connected to the other end of the inductor L, the second pin of the second operational amplifier is connected to one end of the resistor R3, the first pin of the second operational amplifier is respectively connected to the other end of the resistor R3 and the output end OUT, the fourth pin of the second operational amplifier is grounded, and the eighth pin of the second operational amplifier is connected to the VCC end;

[0030] The sampling circuit is used to collect the output signal of the output terminal OUT.

[0031] As a further solution of the utility model: the equivalent capacitor C is composed of the inner electrode and the outer electrode; the inductor L is a high-Q ceramic inductor;

[0032] The signal processing circuit is also used to calculate the lubricating oil impedance of the coaxial electrode according to the output signal of the sampling circuit.

[0033] As a further solution of the utility model: the signal processing circuit calculates the real part and the imaginary part of the complex dielectric constant of the lubricating oil and the lubricating oil impedance according to the following formula:

[0034] Formula 1: , where C is the equivalent capacitance of the coaxial electrode, Q is the charge, V is the voltage, ε0' is the vacuum dielectric constant, ε r ' is the relative dielectric constant of the lubricating oil, L is the height of the coaxial capacitor electrode, b is the radius of the coaxial capacitor outer electrode, and a is the outer diameter of the coaxial capacitor inner electrode;

[0035] Formula 2: ε r '= C / ε0', where ε r ' is the real part of the complex dielectric constant, C is the equivalent capacitance of the coaxial electrode, ε0' is the vacuum dielectric constant;

[0036] Formula 3: ε r '' = 1 / (2πfESR), where ε r '' is the imaginary part of the complex dielectric constant, f is the frequency of the oscillation circuit, and ESR is the equivalent resistance of the coaxial electrode;

[0037] Formula 4: , where tanδ is the dielectric loss tangent, ε r ' is the real part of the complex dielectric constant, ε r '' is the imaginary part of the complex dielectric constant;

[0038] Formula 5: , where Z is the lubricating oil impedance between the coaxial electrodes, L is the height of the coaxial capacitor electrode, b is the radius of the coaxial capacitor outer electrode, a is the outer diameter of the coaxial capacitor inner electrode, ε r ' is the real part of the complex dielectric constant, ε r '' is the imaginary part of the complex dielectric constant, tanδ is the dielectric loss tangent, ω is the resonant frequency, C is the equivalent capacitance of the coaxial electrode, and j is the imaginary number sign (indicating that when calculating impedance, the current of the capacitor element leads the voltage by 90 degrees in phase).

[0039] The utility model also provides another technical solution: a monitoring system for monitoring the complex dielectric constant of lubricating oil based on impedance spectroscopy, comprising a monitoring device for monitoring the complex dielectric constant of lubricating oil based on impedance spectroscopy as described in any of the above, and also comprising a host computer connected to a cable connector arranged on the top of the outer electrode.

[0040] Beneficial effects of the utility model:

[0041] This solution detects the complex dielectric constant. By using impedance spectrum monitoring technology, the coaxial electrode equivalent capacitance and coaxial electrode equivalent resistance are set in the oscillation circuit. Not only the dielectric constant (real part of the complex dielectric constant) but also the dielectric loss (imaginary part of the complex dielectric constant) is detected. The sensitivity is two orders of magnitude higher than the existing technology that simply detects the dielectric constant, and the resolution is also higher. Specifically, by simultaneously monitoring the real and imaginary parts of the complex dielectric constant, the monitoring sensitivity of the change in lubricating oil quality is improved, so that even in the case of oxidation and degradation after the oil is contaminated, the change in oil quality can be accurately reflected, thereby providing a more effective technical means for the maintenance of the lubricating oil. In detail, the lubricating oil between the inner and outer electrodes of the coaxial electrode sensor acts as a medium, and its dielectric properties will affect the oscillation frequency of the circuit. Therefore, by using circuits and signal processing circuits to collect and measure the changes in the oscillation frequency, the dielectric properties of the lubricating oil can be inferred, and then its quality can be monitored. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a schematic structural diagram of the monitoring device for monitoring the complex dielectric constant of lubricating oil based on impedance spectroscopy according to the utility model.

[0043] Figure 2 This is a block diagram of the monitoring system for monitoring the complex dielectric constant of lubricating oil based on impedance spectroscopy according to the utility model.

[0044] Figure 3 The dielectric loss tangent value tanδ and the complex dielectric constant ε of the utility model are r * The real part ε r ' and the imaginary part ε r ” is a schematic diagram of the coordinate relationship between .

[0045] Figure 4 It is a circuit diagram of the oscillation circuit of the utility model.

[0046] Figure 5 for Figure 4 Schematic diagram of the circuit structure in the dotted box.

[0047] Figure 6 It is a schematic diagram of the planar structure of the coaxial electrode of the utility model.

[0048] Reference numerals include:

[0049] 1—stainless steel shell, 10—external electrode,

[0050] 11—inner cavity, 12—cable connector,

[0051] 111 — first plate, 112 — second plate, 113 — fastener;

[0052] 2—Inner electrode,

[0053] 21—rod portion, 22—probe portion;

[0054] 3—Installation connector,

[0055] 31 - shell joint, 32 - threaded connection, 33 - probe shield,

[0056] 331—Oil storage space;

[0057] 4—Insulation bracket,

[0058] 41—sealing ring;

[0059] 5—Temperature probe. DETAILED DESCRIPTION

[0060] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0061] In the description of the present utility model, it should be noted that the orientation or position relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present utility model and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present utility model; the terms "first", "second", and "third" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance. In addition, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.

[0062] like Figure 1 to Figure 6 As shown, in an embodiment of the utility model, a monitoring device for monitoring the complex dielectric constant of lubricating oil based on impedance spectroscopy is provided, comprising: a coaxial electrode sensor, an oscillation circuit, a sampling circuit and a signal processing circuit. Among them:

[0063] The coaxial electrode sensor is used for contacting with the lubricating oil and converting the electrical characteristics of the lubricating oil into an electrical signal.

[0064] An oscillating circuit is used to generate an AC signal in a specific frequency range for exciting the coaxial electrode sensor, and the oscillating circuit has a coaxial electrode equivalent capacitance and a coaxial electrode equivalent resistance.

[0065] A sampling circuit is used to collect the signal output by the coaxial electrode sensor.

[0066] The signal processing circuit is used to process the signal collected by the sampling circuit according to the impedance spectrum monitoring technology, calculate the real part of the complex dielectric constant that matches the equivalent capacitance of the coaxial electrode and the imaginary part of the complex dielectric constant that matches the equivalent resistance of the coaxial electrode in the lubricating oil, and judge the quality state of the lubricating oil according to a preset threshold value. Specifically, the lubricating oil impedance Z is closely related to the dielectric loss tangent value tanδ. After the lubricating oil impedance Z is temperature compensated, the corresponding relationship between the lubricating oil impedance Z and the lubricating oil quality degradation and contamination can be established, thereby completing the monitoring of the lubricating oil quality. The signal processing circuit is arranged on the PCB board, including a signal processing unit, such as a microprocessor, a single-chip microcomputer, etc., which is arranged on the first board 111.

[0067] This solution detects the complex dielectric constant. By using impedance spectrum monitoring technology, the coaxial electrode equivalent capacitance and coaxial electrode equivalent resistance are set in the oscillation circuit. Not only the dielectric constant (real part of the complex dielectric constant) but also the dielectric loss (imaginary part of the complex dielectric constant) is detected. The sensitivity is two orders of magnitude higher than the existing technology that simply detects the dielectric constant, and the resolution is also higher. Specifically, by simultaneously monitoring the real and imaginary parts of the complex dielectric constant, the monitoring sensitivity of the change in lubricating oil quality is improved, so that even in the case of oxidation and degradation after the oil is contaminated, the change in oil quality can be accurately reflected, thereby providing a more effective technical means for the maintenance of the lubricating oil. In detail, the lubricating oil between the inner and outer electrodes 10 of the coaxial electrode sensor acts as a medium, and its dielectric properties will affect the oscillation frequency of the circuit. Therefore, by using circuits and signal processing circuits to collect and measure the changes in the oscillation frequency, the dielectric properties of the lubricating oil can be inferred, and then its quality can be monitored.

[0068] In one embodiment, Figure 1 As shown, the monitoring device for monitoring the complex dielectric constant of lubricating oil based on impedance spectroscopy also includes:

[0069] The temperature sensor is used to measure the temperature of the lubricating oil and perform temperature compensation on the measurement result. Specifically, the temperature sensor includes a temperature probe 5 .

[0070] In another embodiment, Figure 1 As shown, the coaxial electrode sensor includes: a coaxial electrode. The monitoring device for monitoring the complex dielectric constant of lubricating oil based on impedance spectroscopy also includes: a PCB board, a mounting connector 3, an insulating bracket 4 and a sealing ring 41. Among them:

[0071] The coaxial electrode comprises an inner electrode 2 and an outer electrode 10, and lubricating oil is filled between the inner electrode 2 and the outer electrode 10; the inner electrode 2 is a gold-plated electrode made of stainless steel, and the outer electrode 10 comprises a stainless steel shell 1 at the top and a mounting joint 3 at the bottom, and the interior of the stainless steel shell 1 is hollow with an inner cavity 11, and the inner electrode 2 and the outer electrode 10 form a coaxial electrode probe. Specifically, as Figure 6 As shown, the coaxial electrode probe has an inner electrode 2 and an outer electrode 10. The inner electrode 2 is a gold electrode (radius a), specifically made of 316 stainless steel, and gold-plated on the outside. The outer electrode 10 includes a stainless steel shell 1 (radius b) and a mounting joint 3, specifically made of 316 stainless steel. Lubricating oil is filled between the inner electrode 2 and the outer electrode 10, specifically the oil space 331 is filled with lubricating oil. The capacitance C between the inner electrode 2 and the outer electrode 10 is the equivalent capacitance of the coaxial electrode, which is calculated using formula 1. The equivalent circuit diagram of the coaxial electrode composed of the inner electrode 2 and the outer electrode 10 is shown in Figure 5 As shown. The equivalent capacitance C is composed of the inner electrode 2 and the outer electrode 10. The real part of the complex dielectric constant ε r ', which is equivalent to the equivalent capacitance C of the coaxial electrode in the parallel equivalent circuit model. ε r The larger the value of the capacitor is, the greater the energy storage caused by the same AC voltage. That is, the real part indicates the amount of energy storage. The imaginary part of the complex dielectric constant ε r '', which is equivalent to the equivalent resistance ESR of the coaxial electrode in the parallel equivalent circuit model. ε r The larger the value of '', the smaller the equivalent resistance value, indicating that the loss caused under the same AC voltage is greater. That is, the imaginary part indicates the magnitude of the dielectric loss.

[0072] A PCB board is arranged in the inner cavity 11, and the oscillation circuit and the sampling circuit are pre-placed on the PCB board.

[0073] The insulating bracket 4 is arranged in the mounting joint 3 .

[0074] The sealing ring 41 is sleeved on the insulating bracket 4 .

[0075] The temperature sensor is arranged in the mounting joint 3 and is located on one side of the insulating bracket 4 .

[0076] In yet another embodiment, Figure 1As shown, the mounting joint 3 comprises an integrally formed shell joint portion 31, a threaded connection portion 32 and a probe shield portion 33, one end of the shell joint portion 31 is coaxially connected to the bottom of the stainless steel shell 1, one end of the threaded connection portion 32 is coaxially arranged at an end of the shell joint portion 31 away from the stainless steel shell 1, and the probe shield portion 33 is coaxially arranged at an end of the threaded connection portion 32 away from the shell joint portion 31;

[0077] The inner electrode 2 comprises a coaxially integrally formed connecting rod portion 21 and a probe portion 22, wherein the probe portion 22 is coaxially disposed in the probe shield portion 33, and an end of the connecting rod portion 21 away from the probe portion 22 extends close to the inner cavity 11;

[0078] The insulating bracket 4 is sleeved on the connecting rod portion 21, one end of the insulating bracket 4 abuts against one end of the probe portion 22 close to the connecting rod portion 21, and the other end of the insulating bracket 4 abuts against the inner wall of the shell joint portion 31; the sealing ring 41 is clamped on one end of the insulating bracket 4 close to the probe portion 22;

[0079] An oil receiving space 331 for receiving lubricating oil is formed between the probe shield portion 33 , the probe portion 22 and the insulating bracket 4 .

[0080] In yet another embodiment, Figure 1 As shown, the monitoring device for monitoring the complex dielectric constant of lubricating oil based on impedance spectroscopy also includes a power supply circuit and a communication circuit, the PCB board includes a first board 111 and a second board 112, the oscillation circuit and the sampling circuit are respectively pre-set on the first board 111, and the power supply circuit and the communication circuit are respectively pre-set on the second board 112;

[0081] The inner cavity 11 is provided with fasteners 113 connected to the first plate 111 and the second plate 112 respectively;

[0082] A cable connector 12 connected to the communication circuit is disposed on the top of the stainless steel housing 1 .

[0083] In another embodiment, if Figure 1~Figure 4 As shown, the oscillation circuit adopts a Colpitts oscillation circuit, and the oscillation frequency range of the oscillation circuit is 1-10 MHz. Specifically, the oscillation circuit is a Colpitts resonant circuit.

[0084] Select the oscillation frequency of the oscillation circuit: In order to minimize the cost and maximize the sensitivity of the sensor and monitoring device, from the perspective of the practical application of lubricating oil quality monitoring, an appropriate oscillation frequency range should be selected to take into account the cost and detection accuracy of the impedance spectrum monitoring device. From the Nyquist plot, it can be seen that when measuring the impedance Z of the lubricating oil, the low frequency is most sensitive to the impedance change caused by the change in the dielectric constant of the measured lubricating oil. The disadvantage is that a small drift in the measurement frequency will cause a large change in the impedance measurement, resulting in inaccurate measurement. The measurement frequency drift of high frequency (1MHz ~ 100MHz) is not important because the impedance does not change significantly relative to the reference frequency of the oscillation, but too high a frequency has the disadvantage of low sensitivity to detect changes in the dielectric constant. After research and analysis by the inventor, it was found that the operating frequency range finally confirmed is 1~10MHz. Utilizing this feature, a monitoring device for monitoring the complex dielectric constant of lubricating oil based on impedance spectroscopy in this case provides real-time monitoring of oil quality at a lower cost and higher accuracy, including indicators such as oil oxidation, degradation, contamination, and water ingress.

[0085] Choose a reasonable oscillation circuit: Figure 1~Figure 4 As shown in Figure 1, the impedance spectroscopy measurement technique measures the dielectric loss tangent tanδ over a wide frequency range. , ε r ' is the real part of the complex dielectric constant, ε r '' is the imaginary part of the complex dielectric constant. For the quality monitoring of lubricating oil, we prefer to measure the dielectric loss tangent tanδ in a smaller frequency range (such as 1~10MHz) is the most cost-effective. For high frequency, that is, greater than 1MHz, the best measurement method is to use a Colpitts oscillator. In this case, we use a modified Colpitts oscillator circuit to complete the measurement of the dielectric loss tangent tanδ. Figure 4 In the circuit diagram of the oscillator circuit shown in the figure, the dotted box is Figure 5 As shown, ESR is the equivalent resistance of the coaxial electrode, which represents the dielectric loss and is the imaginary part of the complex dielectric constant ε r ''; C is the equivalent capacitance of the coaxial electrode, which represents the energy storage term and is the real part of the dielectric constant ε r '.

[0086] Specifically, the coaxial electrode is directly immersed in the lubricating oil so that it can sense changes in the electrical properties of the lubricating oil. The structure of the coaxial electrode can form a uniform electric field between the inner and outer electrodes 10, ensuring the accuracy and consistency of the measurement. When the oscillating circuit applies an AC electric field, the dielectric properties of the lubricating oil will cause the impedance of the lubricating oil between the coaxial electrodes to change. This impedance change will be converted into an electrical signal for subsequent circuits, namely signal processing circuits, to process and analyze.

[0087] This solution has a simple structure, is easy to process and install, has high measurement accuracy, and causes less pollution to the lubricating oil.

[0088] The real and imaginary parts of the complex dielectric constant can be monitored simultaneously, thus improving the monitoring sensitivity.

[0089] The cost of the monitoring device is reduced by selecting a suitable oscillation frequency range and a Colpitts oscillation circuit.

[0090] Realize real-time monitoring of lubricant quality and promptly detect lubricant deterioration and contamination.

[0091] In another embodiment, if Figure 4 As shown, the oscillation circuit includes: a resistor R1, an inductor L, a capacitor C1, an equivalent capacitor C, an equivalent resistor ESR, a capacitor C2, a resistor R2, a VREF terminal, a VCC terminal, a first operational amplifier, a second operational amplifier, a resistor R3, and an output terminal OUT; wherein,

[0092] One end of the resistor R1 is connected to the +5V terminal, one end of the inductor L is connected to the other end of the resistor R1, one end of the capacitor C1 is connected to the other end of the inductor L, one end of the equivalent resistor ESR is connected to the other end of the capacitor C1, one end of the equivalent capacitor C is connected to the other end of the equivalent resistor ESR, and the other end of the equivalent capacitor C is grounded;

[0093] One end of the capacitor C2 is connected to the other end of the resistor R1, the other end of the capacitor C2 is connected to the first pin of the first operational amplifier, one end of the resistor R2 is connected to the VREF terminal, the other end of the resistor R2 is connected to the second pin of the first operational amplifier, the third pin of the first operational amplifier is connected to the other end of the inductor L, the fourth pin of the first operational amplifier is grounded, and the eighth pin of the first operational amplifier is connected to the VCC terminal;

[0094] The third pin of the second operational amplifier is connected to the other end of the inductor L, the second pin of the second operational amplifier is connected to one end of the resistor R3, the first pin of the second operational amplifier is respectively connected to the other end of the resistor R3 and the output end OUT, the fourth pin of the second operational amplifier is grounded, and the eighth pin of the second operational amplifier is connected to the VCC end;

[0095] The sampling circuit is used to collect the output signal of the output terminal OUT. Specifically, the coaxial electrode equivalent capacitance is an equivalent capacitance C, and the coaxial electrode equivalent resistance is an equivalent resistance ESR.

[0096] In another embodiment, if Figure 1 , Figure 4 , Figure 5 and Figure 6 As shown, the equivalent capacitor C is composed of the inner electrode 2 and the outer electrode 10; the inductor L is a high-Q ceramic inductor;

[0097] The signal processing circuit is also used to calculate the lubricating oil impedance of the coaxial electrode according to the output signal of the sampling circuit.

[0098] In another embodiment, the signal processing circuit calculates the real part and the imaginary part of the complex dielectric constant of the lubricating oil and the lubricating oil impedance according to the following formula:

[0099] Formula 1: , where C is the equivalent capacitance of the coaxial electrode, Q is the charge, V is the voltage, ε0' is the vacuum dielectric constant, ε r ' is the relative dielectric constant of the lubricating oil, L is the height of the coaxial capacitor electrode, b is the radius of the coaxial capacitor outer electrode 10, and a is the outer diameter of the coaxial capacitor inner electrode 2;

[0100] Formula 2: ε r '= C / ε0', where ε r ' is the real part of the complex dielectric constant, C is the equivalent capacitance of the coaxial electrode, ε0' is the vacuum dielectric constant;

[0101] Formula 3: ε r '' = 1 / (2πfESR), where ε r '' is the imaginary part of the complex dielectric constant, f is the frequency of the oscillation circuit, and ESR is the equivalent resistance of the coaxial electrode;

[0102] Formula 4: , where tanδ is the dielectric loss tangent, ε r ' is the real part of the complex dielectric constant, ε r '' is the imaginary part of the complex dielectric constant;

[0103] Formula 5: , where Z is the lubricating oil impedance between the coaxial electrodes, L is the height of the coaxial capacitor electrode, b is the radius of the coaxial capacitor outer electrode 10, a is the outer diameter of the coaxial capacitor inner electrode 2, ε r ' is the real part of the complex dielectric constant, ε r '' is the imaginary part of the complex dielectric constant, tanδ is the dielectric loss tangent, ω is the resonant frequency, C is the equivalent capacitance of the coaxial electrode, and j is the imaginary number sign (indicating that when calculating impedance, the current of the capacitor element leads the voltage by 90 degrees in phase).

[0104] In this scheme, the imaginary part of the complex dielectric constant is caused by various relaxation polarizations caused by the inability of various steering polarizations inside the material to keep up with the changes in the external high-frequency electric field, and represents the loss term of the material. The real part of the complex dielectric constant (capacitance change) and the imaginary part of the complex dielectric constant (dielectric loss) are monitored at the same time. As a result, a higher sensitivity is obtained than the conventional monitoring of only the real part.

[0105] For example, the laboratory analyzed a new mineral oil, and the dielectric loss tangent value tanδ was 0.001. After a large amount of impurities were artificially added to the oil sample, the dielectric loss tangent value tanδ changed to 0.1. The corresponding real part of the common dielectric constant sensor on the market only changed from 2.25 to 2.45. It can be seen that measuring the ratio of the real part to the imaginary part of the complex dielectric constant, that is, the dielectric loss tangent value tanδ, is 2 orders of magnitude higher in sensitivity, about 100 times, than the method of measuring only the real part of the complex dielectric constant.

[0106] A coaxial electrode is used, embedded in the lubricating oil, and the dielectric loss tangent value tanδ of the oil between the inner and outer electrodes 10 of the coaxial electrode is measured. Specifically, a Colpitts resonant circuit is used to form an LC oscillation, where L is an inductor, and a high-Q ceramic inductor is used to form an LC resonance with the coaxial electrode, and the voltage output terminal OUT of the oscillation circuit is measured. After temperature compensation by the temperature probe 5, the output terminal OUT has a corresponding relationship with the dielectric loss tangent value tanδ, and thus has a corresponding relationship with the impedance Z of the sensor coaxial electrode, thereby realizing the judgment and online monitoring of the oil quality.

[0107] like Figure 1~Figure 4 As shown in the figure, a reasonable oscillation circuit and sampling circuit are used, and a suitable oscillation frequency is selected to complete the measurement of the impedance Z of the lubricating oil between the coaxial electrodes of the sensor. Since the lubricating oil impedance Z has a corresponding relationship with the dielectric loss tangent value tanδ, the complex dielectric constant ε is also related at the same time. r * The real part ε r ' and the imaginary part ε r '', thus forming an impedance spectrum sensor and monitoring device.

[0108] The equivalent circuit diagram of the coaxial electrode composed of the inner and outer electrodes 10 is shown in Figure 5 As shown. The equivalent capacitance C is composed of the inner electrode 2 and the outer electrode 10. The real part of the complex dielectric constant ε r ', which is equivalent to the equivalent capacitance C of the coaxial electrode in the parallel equivalent circuit model. ε r The larger the value of the capacitor is, the greater the energy storage caused by the same AC voltage. That is, the real part indicates the amount of energy storage. The imaginary part of the complex dielectric constant ε r '', which is equivalent to the equivalent resistance ESR of the coaxial electrode in the parallel equivalent circuit model. ε r The larger the value of '', the smaller the equivalent resistance value, indicating that the loss caused under the same AC voltage is greater. That is, the imaginary part indicates the magnitude of the dielectric loss.

[0109] Due to ε r '>>ε r", after simple conversion, we get formula 5. By measuring the output terminal OUT of the oscillation circuit, we can get the change of the lubricating oil impedance Z between the coaxial electrode sensors. The impedance Z is closely related to the dielectric loss tangent value tanδ. After completing the temperature compensation of the impedance Z, the corresponding relationship between the impedance Z and the deterioration and contamination of the lubricating oil quality can be established, thereby completing the monitoring of the lubricating oil quality.

[0110] A monitoring system for monitoring the complex dielectric constant of lubricating oil based on impedance spectroscopy, such as Figure 2 As shown, it includes a monitoring device for monitoring the complex dielectric constant of lubricating oil based on impedance spectroscopy as described in any one of the above, and also includes a host computer connected to the cable connector 12 arranged on the top of the outer electrode 10.

[0111] The coaxial electrode sensor is covered by a stainless steel shell 1 of an outer electrode 10. The entire monitoring device is embedded and installed on a lubricating oil pipeline or oil tank by installing a shell joint 31, a threaded connection 32, a probe shield 33 and a suitable seal (not shown in the figure). The threaded interface of the threaded connection 32 adopts thread specifications such as G1 / 2 or M20*1.5. The probe shield 33 is a part of the outer electrode 10 of the coaxial electrode, and the gold-plated inner electrode 2 is an inner electrode 2 of the coaxial electrode. The two together constitute a coaxial electrode probe. The space between the inner electrode 2 and the outer electrode 10 is filled with lubricating oil. The gold-plated inner electrode 2 is sealed by a sealing ring 41 and an insulating bracket 4 to isolate the lubricating oil from the internal PCB board of the monitoring device. At the same time, a temperature probe 5 is arranged to complete the temperature compensation of the measurement result. The gold-plated inner electrode 2 is electrically connected to the oscillation circuit and the sampling circuit. The oscillation circuit completes the oscillation excitation of the coaxial electrode, and the sampling circuit completes the signal acquisition of the output end OUT of the oscillation circuit. The power supply circuit supplies power to the monitoring device, and the communication circuit is connected to the host computer through the cable connector 12, specifically, the data of the monitoring device is sent to the host computer by using RS485 digital interface or 0-10V, 4-20mA analog interface. The fastener 113 fixes the first board 111 pre-installed with the oscillation circuit and the sampling circuit, and the second board 112 pre-installed with the power supply circuit and the communication circuit in the inner cavity 11 of the monitoring device.

[0112] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A monitoring device for monitoring the complex dielectric constant of lubricating oil based on impedance spectroscopy, characterized in that: include: A coaxial electrode sensor, the coaxial electrode sensor is used to contact the lubricating oil and convert the electrical characteristics of the lubricating oil into an electrical signal; An oscillating circuit, the oscillating circuit is used to generate an AC signal in a specific frequency range to excite the coaxial electrode sensor, the oscillating circuit having a coaxial electrode equivalent capacitance and a coaxial electrode equivalent resistance; A sampling circuit, the sampling circuit is used to collect the signal output by the coaxial electrode sensor; as well as A signal processing circuit is used to process the signal collected by the sampling circuit according to the impedance spectrum monitoring technology, calculate the real part of the complex dielectric constant matching the equivalent capacitance of the coaxial electrode and the imaginary part of the complex dielectric constant matching the equivalent resistance of the coaxial electrode, and judge the quality status of the lubricating oil according to a preset threshold value.

2. The monitoring device for monitoring the complex dielectric constant of lubricating oil based on impedance spectroscopy according to claim 1, characterized in that: The monitoring device for monitoring the complex dielectric constant of lubricating oil based on impedance spectroscopy also includes: The temperature sensor is used to measure the temperature of the lubricating oil and perform temperature compensation on the measurement result.

3. The monitoring device for monitoring the complex dielectric constant of lubricating oil based on impedance spectroscopy according to claim 2 is characterized in that: The coaxial electrode sensor comprises: A coaxial electrode, the coaxial electrode comprising an inner electrode (2) and an outer electrode (10), wherein lubricating oil is filled between the inner electrode (2) and the outer electrode (10); the inner electrode (2) is a gold-plated electrode made of stainless steel, the outer electrode (10) comprises a stainless steel shell (1) at the top and a mounting joint (3) at the bottom, the stainless steel shell (1) is hollow inside and has an inner cavity (11), and the inner electrode (2) and the outer electrode (10) form a coaxial electrode probe; The monitoring device for monitoring the complex dielectric constant of lubricating oil based on impedance spectroscopy also includes: A PCB board, arranged in the inner cavity (11), wherein the oscillation circuit and the sampling circuit are pre-placed on the PCB board; An insulating bracket (4) is arranged in the mounting joint (3); and A sealing ring (41) sleeved on the insulating support (4); Wherein, the temperature sensor is arranged in the mounting joint (3) and is located on one side of the insulating bracket (4).

4. The monitoring device for monitoring the complex dielectric constant of lubricating oil based on impedance spectroscopy according to claim 3 is characterized in that: The mounting joint (3) comprises an integrally formed shell joint portion (31), a threaded connection portion (32) and a probe shield portion (33); one end of the shell joint portion (31) is coaxially connected to the bottom of the stainless steel shell (1); one end of the threaded connection portion (32) is coaxially arranged at an end of the shell joint portion (31) away from the stainless steel shell (1); and the probe shield portion (33) is coaxially arranged at an end of the threaded connection portion (32) away from the shell joint portion (31); The inner electrode (2) comprises a connecting rod portion (21) and a probe portion (22) which are coaxially integrally formed, the probe portion (22) being coaxially arranged in the probe shield portion (33), and an end of the connecting rod portion (21) away from the probe portion (22) extending close to the inner cavity (11); The insulating bracket (4) is sleeved on the connecting rod portion (21), one end of the insulating bracket (4) abuts against an end of the probe portion (22) close to the connecting rod portion (21), and the other end of the insulating bracket (4) abuts against the inner wall of the shell joint portion (31); the sealing ring (41) is clamped on an end of the insulating bracket (4) close to the probe portion (22); An oil receiving space (331) for receiving lubricating oil is formed between the probe shield portion (33), the probe portion (22) and the insulating bracket (4).

5. The monitoring device for monitoring the complex dielectric constant of lubricating oil based on impedance spectroscopy according to claim 3, characterized in that: The monitoring device for monitoring the complex dielectric constant of lubricating oil based on impedance spectroscopy also includes a power supply circuit and a communication circuit, the PCB board includes a first board (111) and a second board (112), the oscillation circuit and the sampling circuit are respectively pre-set on the first board (111), and the power supply circuit and the communication circuit are respectively pre-set on the second board (112); The inner cavity (11) is provided with fasteners (113) respectively connected to the first plate (111) and the second plate (112); A cable connector (12) connected to the communication circuit is provided on the top of the stainless steel housing (1).

6. The monitoring device for monitoring the complex dielectric constant of lubricating oil based on impedance spectroscopy according to claim 1, characterized in that: The oscillation circuit adopts a Colpitts oscillation circuit, and the oscillation frequency range of the oscillation circuit is 1-10 MHz.

7. The monitoring device for monitoring the complex dielectric constant of lubricating oil based on impedance spectroscopy according to claim 1, characterized in that: The oscillation circuit includes: a resistor R1, an inductor L, a capacitor C1, an equivalent capacitor C, an equivalent resistor ESR, a capacitor C2, a resistor R2, a VREF terminal, a VCC terminal, a first operational amplifier, a second operational amplifier, a resistor R3, and an output terminal OUT; wherein, One end of the resistor R1 is connected to the +5V terminal, one end of the inductor L is connected to the other end of the resistor R1, one end of the capacitor C1 is connected to the other end of the inductor L, one end of the equivalent resistor ESR is connected to the other end of the capacitor C1, one end of the equivalent capacitor C is connected to the other end of the equivalent resistor ESR, and the other end of the equivalent capacitor C is grounded; One end of the capacitor C2 is connected to the other end of the resistor R1, the other end of the capacitor C2 is connected to the first pin of the first operational amplifier, one end of the resistor R2 is connected to the VREF terminal, the other end of the resistor R2 is connected to the second pin of the first operational amplifier, the third pin of the first operational amplifier is connected to the other end of the inductor L, the fourth pin of the first operational amplifier is grounded, and the eighth pin of the first operational amplifier is connected to the VCC terminal; The third pin of the second operational amplifier is connected to the other end of the inductor L, the second pin of the second operational amplifier is connected to one end of the resistor R3, the first pin of the second operational amplifier is respectively connected to the other end of the resistor R3 and the output end OUT, the fourth pin of the second operational amplifier is grounded, and the eighth pin of the second operational amplifier is connected to the VCC end; The sampling circuit is used to collect the output signal of the output terminal OUT.

8. The monitoring device for monitoring the complex dielectric constant of lubricating oil based on impedance spectroscopy according to claim 3, characterized in that: The oscillation circuit includes: a resistor R1, an inductor L, a capacitor C1, an equivalent capacitor C, an equivalent resistor ESR, a capacitor C2, a resistor R2, a VREF terminal, a VCC terminal, a first operational amplifier, a second operational amplifier, a resistor R3, and an output terminal OUT; wherein, One end of the resistor R1 is connected to the +5V terminal, one end of the inductor L is connected to the other end of the resistor R1, one end of the capacitor C1 is connected to the other end of the inductor L, one end of the equivalent resistor ESR is connected to the other end of the capacitor C1, one end of the equivalent capacitor C is connected to the other end of the equivalent resistor ESR, and the other end of the equivalent capacitor C is grounded; One end of the capacitor C2 is connected to the other end of the resistor R1, the other end of the capacitor C2 is connected to the first pin of the first operational amplifier, one end of the resistor R2 is connected to the VREF terminal, the other end of the resistor R2 is connected to the second pin of the first operational amplifier, the third pin of the first operational amplifier is connected to the other end of the inductor L, the fourth pin of the first operational amplifier is grounded, and the eighth pin of the first operational amplifier is connected to the VCC terminal; The third pin of the second operational amplifier is connected to the other end of the inductor L, the second pin of the second operational amplifier is connected to one end of the resistor R3, the first pin of the second operational amplifier is respectively connected to the other end of the resistor R3 and the output end OUT, the fourth pin of the second operational amplifier is grounded, and the eighth pin of the second operational amplifier is connected to the VCC end; The sampling circuit is used to collect the output signal of the output terminal OUT.

9. The monitoring device for monitoring the complex dielectric constant of lubricating oil based on impedance spectroscopy according to claim 8, characterized in that: The equivalent capacitor C is composed of the inner electrode (2) and the outer electrode (10); and the inductor L is a high-Q ceramic inductor.

10. A monitoring system for monitoring the complex dielectric constant of lubricating oil based on impedance spectroscopy, characterized in that: It comprises a monitoring device for monitoring the complex dielectric constant of lubricating oil based on impedance spectroscopy as described in any one of claims 1 to 9.

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