JP6504504B2 - Oil physical property sensor - Google Patents

Description

  The present invention relates to an oil physical property sensor.

  Conventionally, as an apparatus for determining deterioration of engine oil, for example, there is one having an optical sensor in order to evaluate the amount of carbon particles (remaining carbon content) contained in engine oil (for example, see Patent Document 1). In the deterioration diagnostic device of Patent Document 1, light emitted from a light source is guided into engine oil, and light transmitted through the engine oil is received. This degradation diagnostic device measures the transmitted light intensity of the received light, and refers to a map showing the relationship between the light transmission loss difference between the two wavelengths and the light transmission loss stored in advance and the degree of deterioration of the oil. , Determine the degree of deterioration of the oil.

Japanese Patent Application Laid-Open No. 11-235097

  In the above-mentioned prior art, it is essential that there is oil in the light receiving slit, and the light emitting surface changes because the light emitting surface and the light receiving surface are contaminated due to the presence of oil with viscosity always between the slits. Errors in the determination of the degree of deterioration.

  An object of the present invention is to provide an oil physical property sensor capable of detecting a change in dielectric constant of oil and detecting a change in physical property of oil.

  The oil physical property sensor of the present invention has a cylindrical outer conductor and a rod-shaped inner conductor disposed on the axis of the outer conductor inside the outer conductor, and can store oil between the outer conductor and the inner conductor. Coaxial resonator including various oil reservoirs, a transmitter for transmitting microwaves incident on the oil through the inner conductor, reflection of microwaves propagating in the oil and reflected at a position corresponding to the tip of the inner conductor The receiver reflects the wave through the base end of the inner conductor, reflects the incident wave of the microwave incident from the bottom of the oil reservoir and the tip of the inner conductor, and reflects it on the bottom of the oil reservoir And a measuring unit that measures at least one of a phase difference or an amplitude difference with the reflected wave that has arrived.

In this oil physical property sensor, the microwaves propagate in the oil stored in the oil reservoir in the axial direction of the coaxial resonator, and receive the reflected microwaves reflected at the position corresponding to the tip of the inner conductor. The microwaves propagate in the dielectric (complex dielectric constant: ε = ε _r + jε _i ) to change the phase and amplitude of the microwaves. For example, when the physical properties of the oil change due to the use of impurities, the dielectric constant of the oil, which is a dielectric, changes, and the microwaves propagated in the oil cause a phase shift and an amplitude attenuation. And the phase shift and the attenuation of the amplitude of the microwaves propagating in the oil depend on the amount of impurities contained in the oil. The degraded oil contains impurities such as, for example, metal powder, PM (particulate matter, for example, soot), organic matter (for example, oil decomposition products).

  By measuring at least one of the phase difference or the amplitude difference between the microwave incident wave and the reflected wave, the oil physical property sensor can detect the increase in impurities contained in the oil and can grasp the physical property of the oil. . For example, the deterioration of the oil can be determined by comparing actually measured data with data measured in the past. Since this oil physical property sensor can receive microwaves even when the oil contains impurities, it can be used for oil which can not be measured by the conventional optical sensor.

  In addition, since the phase difference and the amplitude difference of the microwaves increase as the propagation length of the microwaves increases, the measurement accuracy can be improved by lengthening the propagation length of the microwaves. In the oil physical property sensor, the phase difference or amplitude between the incident wave incident from the bottom of the oil reservoir and the reflected wave propagating in the oil and reflected at a position corresponding to the tip of the inner conductor to reach the bottom of the oil reservoir Since the difference is measured, the microwave is reciprocated in the axial direction of the coaxial resonator to ensure the propagation length of the microwave. As a result, while the enlargement of the coaxial resonator is suppressed, the measurement accuracy is improved. By reducing the size of the coaxial resonator, it is easy to mount it on a device (for example, a vehicle) in which oil is used.

  In the direction in which the axis extends, the outer conductor may project beyond the inner conductor to the opposite side to the bottom, and the inner diameter of the outer conductor may be a half or less of the wavelength of the microwave. Thus, microwaves leaking from the outer conductor to the outside can be reduced, and the influence of microwaves on external devices can be suppressed. In addition, the loss of microwaves can be reduced to improve the measurement accuracy.

  Further, the frequency of the microwaves transmitted from the transmission unit can be 0.1 GHz or more and 25 GHz or less. As a result, the influence of the soot contained in the oil on the measurement can be suppressed, the sensitivity to the increase of the residual carbon component in the oil can be improved, and the deterioration of the oil can be detected accurately.

  In addition, the configuration may further include a residual carbon content calculation unit that calculates the residual carbon content contained in the oil based on the phase difference or the amplitude difference of the microwaves measured by the measurement unit. Thus, deterioration of the engine oil can be determined using the residual carbon content calculated by the residual carbon content calculation unit.

  In addition, a metal powder concentration calculation unit may be further provided which calculates the concentration of the metal powder contained in the oil based on the residual carbon content calculated by the residual carbon content calculation unit. Thereby, the concentration of the metal powder contained in the oil can also be grasped.

  In the oil physical property sensor, a storage unit for storing a reference value which is information on at least one of a phase difference or an amplitude difference of microwaves propagating through the oil serving as a reference, and a phase difference or an amplitude difference measured by the measuring unit. A configuration may be provided that includes a determination unit that determines deterioration of the oil by comparing at least one with a corresponding reference value stored in the storage unit. Accordingly, the deterioration of the oil can be determined only by measuring at least one of the phase difference and the amplitude difference and comparing with the reference value, and the calculation load in the determination unit can be reduced.

  According to the oil physical property sensor according to the present invention, it is possible to detect the change of the dielectric constant of the oil and measure the physical property of the oil.

It is a sectional view showing the oil physical property sensor of one embodiment of the present invention. It is a graph which shows the relationship between the residual carbon content contained in engine oil, and the change of the phase of a microwave. It is a graph which shows the relationship between the residual carbon content contained in engine oil, and attenuation of the amplitude of a microwave. It is a graph which shows the relationship between the increase amount of residual carbon content, and metal powder (Fe) density | concentration.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same parts or corresponding parts are denoted by the same reference numerals, and redundant description will be omitted.

  An oil physical property sensor (for example, an engine oil deterioration sensor) 1 shown in FIG. 1 is a sensor used to determine deterioration of an engine oil (lubricating oil) 100 used in a diesel engine (hereinafter referred to as "engine"). It is. The oil physical property sensor 1 may be mounted on a vehicle and used, or may not be mounted on a vehicle and may be used at the time of vehicle maintenance and the like.

  The engine is used as a drive source of the vehicle, and the vehicle on which the engine is mounted is not particularly limited. For example, a large vehicle such as a truck, a bus or a heavy machine or a medium vehicle, a general passenger car, a small vehicle or a light vehicle Or the like. In addition, the engine may be applied to, for example, a ship, a railway, or other power generation equipment.

  The oil physical property sensor 1 includes a coaxial resonator 2, and measures the concentration of residual carbon contained in the engine oil 100 from microwave MW (hereinafter referred to as "microwave") propagated in the engine oil 100. . The coaxial resonator 2 comprises an inner conductor 4, an outer conductor 5 and a bottom 6. In the coaxial resonator 2, engine oil 100 is stored in the region between the inner conductor 4 and the outer conductor 5. The outer conductor 5 has a cylindrical shape and constitutes a side wall of the oil reservoir, and the bottom 6 constitutes the bottom of the oil reservoir. The inner conductor 4 is disposed in the outer conductor 5 to inject microwaves into the engine oil 100.

  The outer conductor 5 and the bottom 6 are made of, for example, a metal (duralumin, aluminum or the like). The upper end (one end in the direction of the axis L1) 5b of the outer conductor 5 is an end on the opening (one opening) 7 side, and the lower end (the other end in the direction of the axis L1) 5c of the outer conductor 5 Is the end on the bottom 6 side. The opening 7 is used when injecting the engine oil 100 into the inside of the coaxial resonator 2 or when discharging the engine oil 100 stored inside the coaxial resonator 2 to the outside.

  The bottom portion 6 is a disk-like bottom plate that covers the lower opening (the other opening) of the outer conductor 5. The bottom 6 is, for example, integrally formed with the outer conductor 5. The outer conductor 5 and the bottom 6 are integrally formed, for example, by cutting a cylindrical body. At the center of the bottom portion 6 in the radial direction, an opening portion for inserting the internal conductor 4 is formed.

  The inner conductor 4 has a cylindrical shape (rod shape), and is disposed inside the outer conductor 5 along the axis L1 of the outer conductor 5. The material of the inner conductor 4 is made of, for example, the same metal (duralmin, aluminum, etc.) as the outer conductor 5. The outer diameter of the inner conductor 4 is, for example, 5.1 mm. The outer diameter of the internal conductor 4 is set such that the characteristic impedance of the coaxial resonator 2 matches the characteristic impedance of the coaxial cable 15 described later. The characteristic impedance of the coaxial cable 15 is, for example, 50Ω. The characteristic impedance is not limited to 50Ω, and may be 75Ω or another value.

  The proximal end of the inner conductor 4 is supported by a support 8 connected to the bottom 6 of the coaxial resonator 2. The upper end (one end, tip) 4a of the internal conductor 4 is disposed on the upper end (one end) 5b side of the outer conductor 5 in the direction of the axis L1.

  The upper end 5 b of the outer conductor 5 is disposed above the upper end 4 a of the inner conductor 4. The protruding length L2 of the upper end portion of the outer conductor 5 protruding upward from the upper end 4a of the inner conductor 4 in the direction of the axis L1 is, for example, 20 mm. If the protrusion length L2 is 20 mm, the coaxial resonator 2 can function as a cylindrical waveguide, and if the inner diameter Da of the outer conductor 5 is 1⁄2 or less of the wavelength of the microwave, the coaxial resonator It is possible to prevent the leakage of microwaves from 2 to the outside. The protruding length L2 is, for example, a length from the upper end surface of the inner conductor 4 to the upper end surface of the outer conductor 5 in the direction of the axis L1. Further, the inner diameter Da of the outer conductor 5 is a distance between the inner peripheral surfaces 5a opposed to each other with the axis L1 interposed therebetween.

  In the present embodiment, the inner diameter Da of the outer conductor 5 is, for example, 16.6 mm. The inner diameter Da of the outer conductor 5 is a half or less of the wavelength of the microwave. When the cutoff wavelength λ of microwaves in the oil physical property sensor 1 is 8.3 mm, the relationship between the inner diameter Da of the outer conductor 5 and the cutoff wavelength λ is λ = Da / 2, so the inner diameter Da of the outer conductor 5 is Should be 16.6 mm. In order to reflect microwaves at a height corresponding to the upper end 4a of the internal conductor 4, the condition of λ / 2 ≧ Da needs to be satisfied.

  The other end 4 b of the inner conductor 4 protrudes through the bottom 6 of the coaxial resonator 2 to the outside (downward). The support portion 8 for supporting the lower side of the inner conductor 4 includes a cylindrical body 9 having a smaller diameter than the outer conductor 5 and a bottom lid 10 covering an opening at the lower end side of the cylindrical body 9.

  The axis of the cylindrical body 9 is disposed along the axis L1 of the outer conductor 5. The upper end (one end) 9 a of the cylindrical body 9 is connected to the periphery of the opening of the bottom 6 of the coaxial resonator 2. The cylindrical body 9 protrudes downward from the bottom portion 6. The bottom lid 10 has a disk shape (plate shape), and is integrally formed with the lower end (the other end) 9 b of the cylindrical body 9. The cylindrical body 9 and the bottom lid 10 are integrally formed, for example, by cutting a cylindrical body.

  An external thread is formed on the outer peripheral surface of the upper end 9 a of the cylindrical body 9, and an internal thread is formed on the inner peripheral surface of the opening of the bottom 6. The upper end 9 a of the cylindrical body 9 is joined to the bottom 6 by being screwed into the opening of the bottom 6. The method of joining the cylindrical body 9 to the bottom portion 6 is not limited to screwing, but may be welding or other joining method such as bolt joining.

  Further, a cylindrical insulator 13 is filled in the inside of the support portion 8, for example. A hole 13 a for inserting the internal conductor 4 penetrates along the center of the column of the insulator 13. The internal conductor 4 is inserted into the hole 13 a of the insulator 13 and held by the support 8. The inner conductor 4 is held by the insulator 13 and insulated with respect to the outer conductor 5 of the coaxial resonator 2, the bottom 6, the cylindrical body 9 of the support 8, and the bottom lid 10. For example, Teflon (registered trademark) is used as the insulator 13. The insulator 13 is not limited to Teflon, and may be another insulator with small dielectric loss.

  The oil physical property sensor 1 includes a connector 14 connected to the coaxial resonator 2, a coaxial cable 15, and an analyzer 16. The connector 14 is provided at one end of the coaxial cable 15. The connector 14 is connected to an end 4 b of the inner conductor 4 projecting outward from the bottom lid 10. An analyzer 16 is connected to the other end of the coaxial cable 15. The analyzer 16 has a CPU that performs arithmetic processing, a ROM and a RAM as storage units, an input signal circuit, an output signal circuit, a power supply circuit, and the like.

  The analyzer 16 includes a high frequency circuit 17. The high frequency circuit 17 functions as a transmitting unit (microwave oscillating unit) that oscillates and transmits microwaves, and also functions as a receiving unit that receives microwaves. The high frequency circuit 17 transmits, for example, microwaves having a frequency of 2.45 GHz. The high frequency circuit 17 may have a frequency variable function of changing the frequency of the microwave. The frequency of the microwaves transmitted by the high frequency circuit 17 is not limited to 2.45 GHz, and may be, for example, 2.9 GHz, 5.8 GHz, 24.125 GHz, or any other frequency. As the microwave, one having a frequency of 0.1 GHz or more and 25 GHz or less can be used. In addition, the high frequency circuit 17 functions as an analysis unit (measurement unit) that analyzes the frequency characteristics of the microwave based on the received signal related to the microwave.

  Furthermore, the analyzer 16 includes a determination unit 18 that determines deterioration of the engine oil 100 based on attenuation of the phase difference or amplitude of the microwave received by the high frequency circuit 17, and a storage unit 19 that stores various data. ing. The determination unit 18 functions as a residual carbon content calculation unit that calculates the residual carbon content contained in the engine oil 100 based on the attenuation of the phase difference or the amplitude of the microwaves. The determination unit 18 determines that the engine oil 100 is degraded when the calculated residual carbon content is equal to or greater than the determination threshold.

  The storage unit 19 stores a determination threshold value for determining deterioration of the engine oil 100, a mathematical expression for calculating a residual carbon content contained in the engine oil 100, a map, data, and the like. The storage unit 19 is, for example, information on at least one of a phase difference or an amplitude difference of microwaves transmitted through a non-used reference engine oil (virgin oil) as a determination threshold value for determining deterioration of the engine oil 100. The reference value which is In addition, other values may be stored in the storage unit 19 as the determination threshold.

Next, the measurement principle in the oil physical property sensor 1 will be described. The microwaves change in phase and amplitude by propagating in a dielectric (complex dielectric constant: ε = ε _r + jε _i ). By detecting at least one of the phase difference and the amplitude difference of the microwaves propagating the propagation distance Lw, it is possible to measure the change of the real part ε _r or the imaginary part ε _i of the dielectric. The amount of impurities contained in the engine oil 100 used for the diesel engine increases due to the use thereof, and the physical properties of the engine oil 100 change to change the dielectric constant. When the dielectric constant of the engine oil 100 changes, the microwaves propagated through the engine oil 100 suffer from phase shift and amplitude attenuation.

  The phase shift and the amplitude attenuation of the microwaves propagated in the engine oil 100 depend on the amount of impurities contained in the engine oil 100. The engine oil 100 used for the diesel engine contains, for example, impurities such as soot (residual carbon content) and metal powder.

For example, in the direction of the axis L1, microwaves incident on the engine oil 100 from the incident point P1 are propagated from the bottom 6 side to the upper end 4a side of the inner conductor 4 and reflected at a position corresponding to the tip of the inner conductor 4 , And propagate in the opposite direction toward the bottom 6 side to reach the incident point P1. In the present embodiment, in the axial direction of the internal conductor 4, the tip of the internal conductor 4 and the liquid level 100a of the engine oil 100 coincide with each other, so the liquid level 100a of the engine oil 100 becomes a reflection position. The oil physical property sensor 1 measures at least one of the phase difference or the amplitude difference between the microwave incident wave W1 at the incident point P1 and the microwave reflected wave W2 at the incident point P1, and detects the deterioration of the engine oil 100. The real part ε _r of the complex dielectric constant ε depends on the phase of the reflected wave W 2, and the imaginary part ε _i of the complex dielectric constant ε depends on the amplitude of the reflected wave W 2.

  In the oil physical property sensor 1, a reference value which is at least one of a phase difference or an amplitude difference of microwaves which propagates an engine oil (virgin oil) which is not used and which is used, and a used engine oil 100 actually measured. Are compared with corresponding measured values (phase difference or amplitude difference) of the microwaves having propagated through to determine the deterioration of the engine oil 100. The oil physical property sensor 1 compares phase differences with each other and compares amplitude differences with each other. The liquid level 100a of the engine oil 100 is measured to be the same so that the microwave propagation distance Lw is the same between the measurement for the reference engine oil and the measurement for the engine oil 100 that is judged to be deteriorated.

  FIG. 2 is a graph showing the relationship between the residual carbon content contained in engine oil 100 and the phase difference of microwaves. The horizontal axis indicates the concentration [%] of residual carbon contained in engine oil 100, and the vertical axis indicates the phase difference (change in phase) [deg] of the microwave. This graph is based on experimental results, and microwaves with a frequency of 2.45 GHz are incident on the engine oil 100 and propagate from the bottom 6 to a position corresponding to the tip of the inner conductor 4, and the tip of the inner conductor 4 The phase difference is measured by receiving the microwave that has been reflected by the liquid surface 100a, which is the position corresponding to the, and has reached the bottom portion 6. The phase difference is a difference between the phase of the incident wave W1 at the incident point P1 and the phase of the reflected wave W2 at the incident point P1, and the microwave reciprocates between the incident point P1 and the liquid surface 100a. It is a phase shift when advancing by the propagation distance Lw.

In FIG. 2, the relationship between the residual carbon content and the phase difference of microwaves is shown by a graph G1 indicated by a straight line. The contribution ratio R ^{2 at} this time was 0.9 or more, and there was a strong correlation. The determination unit 18 can grasp the residual carbon content contained in the engine oil 100 using a mathematical expression indicating the relationship between the residual carbon content and the phase difference of the microwaves.

  FIG. 3 is a graph showing the relationship between the residual carbon content contained in engine oil 100 and the attenuation of the microwave amplitude. The horizontal axis indicates the concentration [%] of residual carbon contained in engine oil 100, and the vertical axis indicates the attenuation [dB] of the amplitude of the microwave. This graph is based on experimental results, and microwaves with a frequency of 2.45 GHz are incident on the engine oil 100, propagate from the bottom 6 to the liquid surface 100a, reflect on the liquid surface 100a, and reach the bottom 6 The microwave is received and the amplitude difference is measured. The amplitude difference is a difference between the amplitude of the incident wave W1 at the incident point P1 and the amplitude of the reflected wave W2 at the incident point P1, and the microwave reciprocates between the incident point P1 and the liquid surface 100a. It is the attenuation of the amplitude when advancing by the propagation distance Lw.

In FIG. 3, the relationship between the residual carbon content and the attenuation of the microwave amplitude is shown by the graph G2 indicated by a straight line. The contribution ratio R ^{2 at} this time was 0.9 or more, and there was a strong correlation. The determination unit 18 can grasp the residual carbon content contained in the engine oil 100 using a mathematical expression indicating the relationship between the residual carbon content and the attenuation of the amplitude of the microwave.

In addition, the determination unit 18 also functions as a metal powder concentration calculation unit that calculates the metal powder (Fe) concentration [ppm] contained in the engine oil 100 based on the increase amount of the remaining carbon content. FIG. 4 is a graph showing the relationship between the amount of increase in residual carbon content and the metal powder (Fe) concentration. The horizontal axis indicates the increase amount [points] of residual carbon contained in engine oil 100, and the vertical axis indicates the metal powder (Fe) concentration [ppm]. This graph is based on experimental results. The increase amount ΔC of the residual carbon content is, for example, the concentration C ₀ [%] of the residual carbon content contained in the engine oil 100 before use and the concentration C of the residual carbon content contained in the engine oil 100 after use for a fixed period ₁ is the difference between the _{[%] (ΔC = C 1} -C 0).

At this time, the concentration C ₀ , C ₁ of the residual carbon component causes the microwave having a frequency of 2.45 GHz to be incident on the engine oil 100, and the phase of the incident wave W1 at the incident point P1 and the reflected wave W2 at the incident point P1. of measuring the difference (phase difference) between the phase, using the formula based on the graph G1 shown in FIG. 2, it is obtained by calculating the concentration C _0, C ₁ of carbon residue.

  Next, the operation of the oil physical property sensor 1 will be described.

  First, engine oil is filled into the coaxial resonator 2. The engine oil 100 is, for example, filled up to the upper end portion 4 a of the inner conductor 4, and the upper end surface of the inner conductor 4 matches the liquid surface 100 a of the engine oil 100. Thus, the outer peripheral surface of the inner conductor 4 is in contact with the engine oil 100 entirely.

  Next, microwaves are transmitted from the analyzer 16. At this time, for example, microwaves with a frequency of 2.45 GHz are transmitted. The microwaves transmitted from the analyzer 16 are transmitted to the inner conductor 4 through the coaxial cable 15. The microwaves transmitted to the inner conductor 4 are incident on the engine oil 100 from the bottom 6 of the engine oil reservoir.

  The microwaves propagate in the engine oil 100 in the direction of the axis L1, are reflected by the fluid surface 100a of the engine oil 100 at a position corresponding to the tip of the inner conductor 4, and opposite in the direction of the axis L1 in the engine oil 100. To the bottom 6 of the engine oil reservoir and received by the inner conductor 4. The microwaves are out of phase (delayed) or attenuated in amplitude when propagating through the engine oil 100. The reflected wave W2 reaching the bottom portion 6 is received by the inner conductor 4 and received by the analyzer 16 through the coaxial cable 15.

  The microwaves received by the analyzer 16 are analyzed by the high frequency circuit 17. Then, the phase difference and the amplitude difference of the microwaves are measured. The high frequency circuit 17 may measure at least one of the phase difference or the amplitude difference of the microwaves.

  Subsequently, the determination unit 18 determines whether the engine oil 100 is deteriorated based on the phase difference or the amplitude difference of the microwaves. The determination unit 18 grasps the concentration of residual carbon contained in the engine oil 100 using the graph G1 shown in FIG. 2, and when the concentration of residual carbon is equal to or higher than the determination threshold, the engine oil 100 is degraded. It is determined that Alternatively, the determination unit 18 uses the graph G2 illustrated in FIG. 3 to grasp the concentration of residual carbon contained in the engine oil 100, and when the concentration of residual carbon is equal to or higher than the determination threshold, the engine oil 100 Is determined to be degraded. The judgment threshold is a value that serves as an index for determining when the engine oil 100 should be replaced, and should be determined by comparison with unused standard engine oil (virgin oil), past results, experiments, etc. Can.

  Further, the determination unit 18 measures the metal powder (Fe) concentration [ppm] contained in the engine oil 100 based on the detected concentration of residual carbon content. The metal powder contained in the engine oil 100 is generated by the wear of metal parts (for example, a piston, a cylinder, a connecting rod, a crankshaft, a pin, a gear, etc.) when the engine is driven. is there. The determination unit 18 calculates the metal powder concentration using the graph G3 indicating the relationship between the increase amount of the residual carbon content and the metal powder concentration shown in FIG. 4. In addition, when the metal powder concentration is equal to or higher than the determination threshold value, the determination unit 18 may determine that the engine oil 100 is deteriorated.

  Then, when it is determined that the engine oil 100 is deteriorated, the oil physical property sensor 1 reports the determination result. For example, the warning lamp is turned on to notify that the engine oil 100 is deteriorated. Alternatively, for example, a liquid crystal display device may be used to notify the determination result. The oil physical property sensor 1 may notify that the engine oil 100 is in a normal state when the engine oil 100 is not deteriorated.

  As described above, according to the oil physical property sensor 1 of the present embodiment, the deterioration of the engine oil 100 can be determined by measuring the attenuation of the phase difference or the amplitude of the microwaves propagating through the engine oil 100. The oil physical property sensor 1 can measure the phase difference or the amplitude difference of the microwaves even when the engine oil contains an impurity. The oil physical property sensor 1 can measure the residual carbon content of the engine oil 100, and the determination accuracy of the deterioration of the engine oil 100 can be improved.

  The oil physical property sensor 1 transmits microwaves with a frequency of 2.45 GHz to detect an increase in residual carbon content. When the frequency of the microwaves is 0.1 GHz or more and 25 GHz or less, the sensitivity to the increase of the residual carbon content in the engine oil can be improved, and the deterioration of the engine oil can be detected with high accuracy.

  In the oil physical property sensor 1, the incident wave W 1 incident from the bottom 6 of the oil reservoir and the reflection that has been propagated in the engine oil 100 and reflected by the liquid surface 100 a corresponding to the tip of the internal conductor and reached the bottom 6 Since the phase difference or the amplitude difference with the wave W2 is measured, the microwave is reciprocated in the direction of the axis L1 of the coaxial resonator 2 to secure the length of propagation of the microwave. As a result, the enlargement of the coaxial resonator 2 is suppressed, and the measurement accuracy is improved. According to the oil physical property sensor 1, by achieving the miniaturization of the coaxial resonator 2, mounting on a vehicle becomes easy.

  Further, in the oil physical property sensor 1, the upper end 5b of the outer conductor 5 protrudes above the upper end 4a of the inner conductor 4, and the inner diameter Da of the outer conductor is a half or less of the wavelength of the microwave Therefore, the microwaves leaking to the outside of the outer conductor 5 can be reduced, and the influence of the microwaves on external equipment can be suppressed.

  The present invention is not limited to the embodiment described above, and various modifications can be made as described below without departing from the scope of the present invention.

  In the above embodiment, the residual carbon content contained in the engine oil 100 is calculated based on the attenuation of the microwave phase difference or amplitude, and it is determined whether the calculated residual carbon content is equal to or greater than the determination threshold value. However, the deterioration of the engine oil 100 may be determined by determining whether or not the attenuation of the microwave phase difference or the amplitude is equal to or greater than the determination threshold.

  Further, in the above embodiment, the residual carbon component contained in the engine oil 100 is calculated based on the attenuation of the phase difference or the amplitude of the microwaves. Further, the oil physical property sensor 1 can also calculate the amount of water contained in the engine oil 100 based on the attenuation of the phase difference or the amplitude of the microwave (water content calculation unit), and the calculated water amount is When it is equal to or higher than the determination threshold value, it may be determined that the engine oil is deteriorated.

  In the above embodiment, although the engine oil 100 is filled up to the height of the upper end 4a of the internal conductor 4, the engine oil 100 is injected to a position lower than the upper end 4a, and the oil physical property sensor 1 is used The engine oil 100 may be injected to a position higher than the upper end 4a. When the liquid surface 100a of the engine oil 100 and the upper end 4a of the internal conductor 4 coincide with each other, the measurement accuracy of the residual carbon can be improved.

  When the "liquid level of oil" is lower than "the upper end 4a of the internal conductor 4", the distance at which the internal conductor is in contact with the oil becomes short, so the internal conductor 4 not used for measuring the dielectric constant of oil. The part will be present. On the other hand, when the "liquid level of the oil" is higher than the "upper end 4a of the inner conductor 4", the oil which is not used for the dielectric constant measurement is present.

  In the above embodiment, the phase difference of the microwaves is calculated by comparing the phase of the microwaves transmitted from the transmitter with the phase of the microwaves received by the receiver. Alternatively, the previous value is stored in the storage unit, and the phase of the microwave (initial value or previous value) stored in the storage unit and the phase of the microwave received by the receiving unit in the subsequent measurement And the phase difference may be calculated to detect a change in the physical properties of the oil. For the calculation of the attenuation of the microwave amplitude, the microwaves are compared by comparing the value (initial value or previous value) stored in the storage unit with the amplitude of the microwave received by the receiving unit at the time of measurement. The change in the physical properties of the oil may be detected by calculating the attenuation of the amplitude of.

  In the above embodiment, the case of judging deterioration of the engine oil 100 is described, but the oil applied to the oil physical property sensor is not limited to the engine oil, and other lubricating oil, insulating oil, hydraulic operation Other oils such as oil and fuel oil may be used.

  DESCRIPTION OF SYMBOLS 1 ... oil physical property sensor, 2 ... coaxial resonator (oil storage part), 4 ... internal conductor, 5 ... external conductor, 6 ... bottom part, 7 ... opening, 8 ... support part, 9 ... cylinder of a support part, 10 ... 10 Bottom cover, 13: insulator, 14: connector, 15: coaxial cable, 16: analyzer, 17: high frequency circuit (transmission unit (microwave oscillation unit), reception unit, measurement unit), 18: determination unit (residue Carbon content calculation unit, metal powder concentration calculation unit) 19 Storage unit 100 Engine oil Da Inner diameter of outer conductor L1 Axis of outer conductor L2 Length of upper end of outer conductor W Micro Wave, W1 ... incident wave of microwave, W2 ... reflected wave of microwave.

Claims (6)

An oil reservoir capable of storing oil between the outer conductor and the inner conductor, which has a cylindrical outer conductor and a rod-shaped inner conductor disposed on the axis of the outer conductor inside the outer conductor. A coaxial resonator,
A transmitter configured to transmit microwaves incident on the oil through the internal conductor;
A receiver configured to receive the reflected wave of the microwave, which is propagated in the oil and reflected at a position corresponding to the tip of the inner conductor, through the proximal end of the inner conductor;
A measuring unit that measures at least one of a phase difference or an amplitude difference between the incident wave of the microwave incident from the bottom of the oil reservoir and the reflected wave that is reflected at the position and reaches the bottom of the oil reservoir And an oil physical property sensor. In the direction in which the axis extends, the outer conductor projects beyond the inner conductor on the opposite side of the bottom,
The oil physical property sensor according to claim 1, wherein the inner diameter of the outer conductor is a half or less of the wavelength of the microwave.   The oil physical property sensor according to claim 1, wherein a frequency of the microwave transmitted from the transmission unit is 0.1 GHz or more and 25 GHz or less.   The residual carbon content calculation part which measures the residual carbon content contained in the said oil based on at least one of the said phase difference of the said microwave measured by the said measurement part or the said amplitude difference is further provided. The oil physical property sensor according to any one of the above.   The oil physical property sensor according to claim 4, further comprising a metal powder concentration calculation unit that calculates the concentration of metal powder contained in the oil based on the residual carbon content calculated by the residual carbon content calculation unit. A storage unit for storing a reference value which is information on at least one of the phase difference or the amplitude difference of the microwaves having propagated the oil serving as a reference;
A determination unit that determines deterioration of the oil by comparing at least one of the phase difference or the amplitude difference measured by the measurement unit with the corresponding reference value stored in the storage unit; The oil physical property sensor as described in any one of Claims 1-5 provided.

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