JP2017090167A - Oil physical property sensor - Google Patents

Abstract

An oil property sensor capable of detecting a change in physical properties of oil by detecting a change in dielectric constant of the oil. An oil property sensor (1) has a cylindrical outer conductor (5) and a rod-shaped inner conductor (4) disposed on the axis (L1) of the outer conductor inside the outer conductor, and between the outer conductor and the inner conductor. Coaxial resonator 2 including an oil reservoir that can store oil, a transmitter that transmits microwave MW that is incident on the oil via the internal conductor, and propagated through the oil and reflected by the upper end 4a of the internal conductor The microwave reflected wave W2 is reflected by the receiving unit that receives the reflected wave W2 through the inner conductor, the microwave incident wave W1 incident from the bottom 6 of the oil reservoir and the upper end of the inner conductor, and is reflected on the bottom of the oil reservoir. A measurement unit that measures at least one of a phase difference or an amplitude difference from the reflected wave that has arrived. [Selection] Figure 1

Description

  The present invention relates to an oil property sensor.

  2. Description of the Related Art Conventionally, for example, as an apparatus for determining deterioration of engine oil, there is an apparatus equipped with an optical sensor for evaluating the amount of carbon particles (residual carbon content) contained in engine oil (for example, see Patent Document 1). In the deterioration diagnosis 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 diagnosis device measures the transmitted light intensity of received light, and refers to a map showing the relationship between the light transmission loss difference between two wavelengths and the light transmission loss stored in advance and the degree of deterioration of oil. Determine the degree of oil degradation.

Japanese Patent Laid-Open No. 11-235097

  In the above prior art, it is essential that oil is present in the light receiving slit, and since there is always oil with viscosity between the slits, the light projecting surface and the light receiving surface become dirty, so the light loss changes. This may cause an error in the determination of the degree of deterioration.

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

  The oil 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. A coaxial resonator including an oil reservoir, a transmitter for transmitting the microwave incident on the oil through the inner conductor, and a reflection of the microwave propagating through the oil and reflected at a position corresponding to the tip of the inner conductor The receiving part that receives the wave through the base end part of the inner conductor and the incident wave of the microwave incident from the bottom part of the oil storing part and the position corresponding to the tip of the inner conductor are reflected on the bottom part of the oil storing part. A measurement unit that measures at least one of a phase difference or an amplitude difference from the reflected wave that has arrived.

In this oil property sensor, the microwave propagates in the oil stored in the oil reservoir in the axial direction of the coaxial resonator, and receives the reflected microwave reflected at the position corresponding to the tip of the internal conductor. The microwave propagates through a dielectric (complex dielectric constant: ε = ε _r + jε _i ), so that the phase and amplitude of the microwave change. For example, when the physical properties of oil including impurities change due to use, the dielectric constant of oil, which is a dielectric, changes, and phase shift and amplitude attenuation occur in the microwave propagated in the oil. The phase shift and amplitude attenuation of the microwave propagated in the oil depend on the amount of impurities contained in the oil. The deteriorated oil contains impurities such as metal powder, PM (particulate matter such as soot), and organic matter (eg oil decomposition product).

  In the oil property sensor, by measuring at least one of the phase difference or amplitude difference between the incident wave and the reflected wave of the microwave, it is possible to detect an increase in impurities contained in the oil and grasp the oil property. . For example, the deterioration of oil can be determined by comparing data actually measured with data measured in the past. This oil physical property sensor can receive microwaves even when impurities are contained in the oil, so that it can be used for oil that cannot be measured by a conventional optical sensor.

  Further, since the microwave phase difference and the amplitude difference increase as the propagation length of the microwave increases, the measurement accuracy can be improved by increasing the propagation length of the microwave. In the oil property sensor, the phase difference or amplitude between the incident wave incident from the bottom of the oil reservoir and the reflected wave that propagates through the oil and reflects at the position corresponding to the tip of the internal conductor and reaches 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 length of propagation of the microwave. Thereby, the enlargement of the coaxial resonator is suppressed and the measurement accuracy is improved. By reducing the size of the coaxial resonator, it can be easily mounted on a device (for example, a vehicle) in which oil is used.

  Further, in the direction in which the axis extends, the outer conductor may protrude to the opposite side of the bottom from the inner conductor, and the inner diameter of the outer conductor may be ½ or less of the wavelength of the microwave. Thereby, the microwave which leaks outside from an external conductor can be reduced, and the influence of the microwave on an external apparatus can be suppressed. Further, it is possible to reduce the loss of microwaves and improve the measurement accuracy.

  Moreover, the frequency of the microwave transmitted from a transmission part can be 0.1 GHz or more and 25 GHz or less. Thereby, the influence on the measurement by the soot contained in the oil can be suppressed, the sensitivity to the increase in the residual carbon content in the oil can be improved, and the deterioration of the oil can be detected with high accuracy.

  Moreover, the structure further provided with the residual carbon content calculation part which calculates the residual carbon content contained in oil based on the phase difference or amplitude difference of the microwave measured by the measurement part may be sufficient. Thereby, deterioration of an engine oil can be determined using the residual carbon content calculated by the residual carbon content calculation part.

  Moreover, the structure further provided with the metal powder concentration calculation part which calculates the density | concentration of the metal powder contained in oil based on the residual carbon content calculated by the residual carbon content calculation part may be sufficient. Thereby, the density | concentration of the metal powder contained in oil can also be grasped | ascertained.

  In addition, the oil physical property sensor includes a storage unit that stores a reference value that is information on at least one of a phase difference or an amplitude difference of a microwave propagated through a reference oil, and a phase difference or an amplitude difference measured by the measurement unit. The structure provided with the determination part which compares at least one and the corresponding reference value stored in the memory | storage part and determines deterioration of oil may be sufficient. Thereby, it is possible to determine the deterioration of the oil simply by measuring at least one of the phase difference or the amplitude difference and comparing it with the reference value, and the calculation load in the determination unit can be reduced.

  According to the oil property sensor of the present invention, it is possible to measure the physical property of the oil by detecting a change in the dielectric constant of the oil.

It is sectional drawing which shows the oil physical property sensor of one Embodiment of this 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 | damping 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.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the same part or an equivalent part, and the overlapping description is abbreviate | omitted.

  An oil property sensor (for example, engine oil deterioration sensor) 1 shown in FIG. 1 is a sensor used when determining deterioration of engine oil (lubricating oil) 100 used in a diesel engine (hereinafter referred to as “engine”). It is. The oil property sensor 1 may be used by being mounted on a vehicle, or may be used at the time of vehicle maintenance without being mounted on a vehicle.

  The engine is used as a driving source of the vehicle, and the vehicle on which the engine is mounted is not particularly limited. For example, the vehicle is a large vehicle such as a truck, a bus, or a heavy machine, a medium-sized vehicle, a normal passenger car, a small vehicle, or a light vehicle. Etc. Further, the engine may be applied to, for example, a ship, a railway, other power generation facilities, and the like.

  The oil property sensor 1 includes a coaxial resonator 2 and measures the concentration of residual carbon contained in the engine oil 100 from a microwave MW (hereinafter referred to as “microwave”) that has propagated through the engine oil 100. . The coaxial resonator 2 includes an inner conductor 4, an outer conductor 5, and a bottom portion 6. In the coaxial resonator 2, engine oil 100 is stored in a 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 a bottom surface of the oil reservoir. The inner conductor 4 is disposed in the outer conductor 5 and makes microwaves enter the engine oil 100.

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

  The bottom 6 is a disc-shaped bottom plate that covers the lower opening (the other opening) of the outer conductor 5. The bottom 6 is formed integrally with the outer conductor 5, for example. The outer conductor 5 and the bottom portion 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 for inserting the internal conductor 4 is formed.

  The inner conductor 4 has a cylindrical shape (bar shape), and is disposed along the axis L <b> 1 of the outer conductor 5 inside the outer conductor 5. The material of the inner conductor 4 is made of the same metal (duralumin, aluminum, etc.) as the outer conductor 5, for example. The outer diameter of the inner conductor 4 is, for example, 5.1 mm. The outer diameter of the inner conductor 4 is set so that the characteristic impedance of the coaxial resonator 2 and the characteristic impedance of a coaxial cable 15 to be described later match. The characteristic impedance of the coaxial cable 15 is 50Ω, for example. The characteristic impedance is not limited to 50Ω, and may be 75Ω or other values.

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

  The upper end portion 5 b of the outer conductor 5 is disposed above the upper end portion 4 a of the inner conductor 4. In the direction of the axis L1, the protruding length L2 of the upper end portion of the outer conductor 5 protruding upward from the upper end portion 4a of the inner conductor 4 is, for example, 20 mm. If the protruding length L2 is 20 mm, the coaxial resonator 2 can function as a cylindrical waveguide. If the inner diameter Da of the outer conductor 5 is made equal to or less than ½ of the wavelength of the microwave, the coaxial resonator Microwave leakage from 2 to the outside can be prevented. The protruding length L2 is, for example, the 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. The inner diameter Da of the outer conductor 5 is a distance between the inner peripheral surfaces 5a facing each other across the axis L1.

  In the present embodiment, the inner diameter Da of the outer conductor 5 is 16.6 mm, for example. The inner diameter Da of the outer conductor 5 has a length of ½ or less of the wavelength of the microwave. When the cutoff wavelength λ of the microwave 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. May be 16.6 mm. In order to reflect microwaves at a height corresponding to the upper end portion 4a of the inner conductor 4, it is necessary to satisfy the condition of λ / 2 ≧ Da.

  The other end 4 b of the inner conductor 4 penetrates the bottom 6 of the coaxial resonator 2 and protrudes outward (downward). The support portion 8 that supports the lower side of the inner conductor 4 includes a cylindrical body 9 that is smaller in diameter than the outer conductor 5 and a bottom lid body 10 that covers an opening on the lower end side of the cylindrical body 9.

  The axis of the cylinder 9 is disposed along the axis L <b> 1 of the outer conductor 5. An upper end portion (one end portion) 9 a of the cylindrical body 9 is connected to the periphery of the opening of the bottom portion 6 of the coaxial resonator 2. The cylindrical body 9 protrudes downward from the bottom portion 6. The bottom cover body 10 has a disk shape (plate shape), and is integrally formed with respect to the lower end portion (the other end portion) 9 b of the cylindrical body 9. The cylinder body 9 and the bottom cover body 10 are integrally formed, for example, by cutting a cylindrical body.

  A male screw portion is formed on the outer peripheral surface of the upper end portion 9 a of the cylindrical body 9, and a female screw portion is formed on the inner peripheral surface of the opening of the bottom portion 6. The upper end portion 9 a of the cylindrical body 9 is joined to the bottom portion 6 by being screwed into the opening portion of the bottom portion 6. The method for joining the cylindrical body 9 to the bottom 6 is not limited to screwing, but may be welding or other joining methods such as bolt joining.

  Further, for example, a cylindrical insulator 13 is filled in the support portion 8. A hole 13 a for inserting the inner conductor 4 passes through the center of the cylinder of the insulator 13. The inner conductor 4 is inserted into the hole 13 a of the insulator 13 and is held by the support portion 8. The inner conductor 4 is held by an insulator 13 and is insulated from the outer conductor 5 of the coaxial resonator 2, the bottom portion 6, the cylindrical body 9 of the support portion 8, and the bottom lid body 10. As the insulator 13, for example, Teflon (registered trademark) is used. The insulator 13 is not limited to Teflon, and may be another insulator having a small dielectric loss.

  The oil property sensor 1 includes a connector 14, a coaxial cable 15, and an analyzer 16 connected to the coaxial resonator 2. The connector 14 is provided on one end side of the coaxial cable 15. The connector 14 is connected to an end 4 b of the inner conductor 4 that protrudes outward from the bottom lid 10. An analyzer 16 is connected to the other end of the coaxial cable 15. The analyzer 16 includes a CPU that performs arithmetic processing, a ROM and a RAM that are 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 transmission unit (microwave oscillation unit) that oscillates and transmits microwaves, and also functions as a reception unit that receives microwaves. The high frequency circuit 17 transmits a microwave having a frequency of 2.45 GHz, for example. The high frequency circuit 17 may have a frequency variable function for changing the frequency of the microwave. The frequency of the microwave 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 other frequencies. A microwave having a frequency of 0.1 GHz or more and 25 GHz or less can be used. 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.

  The analyzer 16 further includes a determination unit 18 that determines deterioration of the engine oil 100 based on the phase difference or amplitude attenuation 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 phase difference or amplitude attenuation of the microwave. The determination unit 18 determines that the engine oil 100 has deteriorated when the calculated residual carbon content is equal to or greater than the determination threshold.

  The storage unit 19 stores a determination threshold for determining deterioration of the engine oil 100, a mathematical formula, a map, data, and the like for calculating a residual carbon content contained in the engine oil 100. The storage unit 19 is, for example, information related to at least one of the phase difference or amplitude difference of the microwave propagated through the reference engine oil (virgin oil) that is not used as a determination threshold value for determining the deterioration of the engine oil 100. Is stored as a reference value. Moreover, you may memorize | store the other value in the memory | storage part 19 as a determination threshold value.

Next, the measurement principle in the oil property sensor 1 will be described. Microwave propagates through a dielectric (complex dielectric constant: ε = ε _r + jε _i ), and thus changes in phase and amplitude. By detecting at least one of the phase difference or amplitude difference of the microwave propagated through the propagation distance Lw, the change in the real part ε _r or the imaginary part ε _i of the dielectric can be measured. The amount of impurities contained in the engine oil 100 used in the diesel engine increases, 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, a phase shift and an amplitude attenuation occur in the microwave propagated through the engine oil 100.

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

For example, in the direction of the axis L 1, the microwave incident on the engine oil 100 from the incident point P 1 is propagated from the bottom 6 side to the upper end 4 a side of the inner conductor 4 and reflected at a position corresponding to the tip of the inner conductor 4. Then, it propagates in the opposite direction toward the bottom 6 side and reaches the incident point P1. In the present embodiment, since the tip of the inner conductor 4 and the liquid level 100a of the engine oil 100 coincide with each other in the axial direction of the inner conductor 4, the liquid level 100a of the engine oil 100 becomes the reflection position. The oil 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 W2, and the imaginary part ε _i of the complex dielectric constant ε depends on the amplitude of the reflected wave W2.

  In the oil property sensor 1, a reference value that is at least one of a phase difference or an amplitude difference of a microwave propagated through a reference engine oil (virgin oil) that is not used, and a used engine oil 100 that is actually measured. The deterioration of the engine oil 100 is determined by comparing the measured value (phase difference or amplitude difference) of the microwave propagated through the. The oil property sensor 1 compares the phase differences and the amplitude differences. Note that 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 in the measurement of the reference engine oil and the measurement of the engine oil 100 that is determined to be deteriorated.

  FIG. 2 is a graph showing the relationship between the residual carbon content contained in the engine oil 100 and the phase difference between the microwaves. The horizontal axis represents the concentration [%] of the residual carbon contained in the engine oil 100, and the vertical axis represents the microwave phase difference (phase change) [deg]. This graph is based on experimental results. A microwave having a frequency of 2.45 GHz is incident on the engine oil 100 and propagates from the bottom 6 to a position corresponding to the tip of the inner conductor 4. The phase difference is measured by receiving the microwave reflected at the liquid surface 100a, which is the position corresponding to, and reaching the bottom 6. This phase difference is the 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 makes one round trip between the incident point P1 and the liquid surface 100a. This is a phase shift when traveling by the propagation distance Lw.

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

  FIG. 3 is a graph showing the relationship between the residual carbon content contained in the engine oil 100 and the attenuation of the amplitude of the microwave. The horizontal axis represents the concentration [%] of the residual carbon contained in the engine oil 100, and the vertical axis represents the attenuation [dB] of the microwave amplitude. This graph is based on experimental results, and a microwave having a frequency of 2.45 GHz is incident on the engine oil 100, propagates from the bottom 6 to the liquid level 100a, is reflected by the liquid level 100a, and reaches the bottom 6 The amplitude difference is measured by receiving a microwave. This amplitude difference is the 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 makes one round trip between the incident point P1 and the liquid surface 100a. Attenuation of amplitude when traveling 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 a graph G <b> 2 indicated by a straight line. Contribution R ² at this time is 0.9 or more, there is a strong correlation. The determination unit 18 can grasp the residual carbon content contained in the engine oil 100 using a mathematical formula indicating the relationship between the residual carbon content and the attenuation of the amplitude of the microwave.

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 grasped increase in the residual 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 shows the increase [points] of the residual carbon contained in the engine oil 100, and the vertical axis shows 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 being used for a certain period. ₁ [%] (ΔC = C ₁ −C ₀ ).

Concentrations C ₀ and C ₁ of the residual carbon content at this time are such that a microwave having a frequency of 2.45 GHz is 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. The difference (phase difference) with respect to the above is measured, and the concentrations C ₀ and C ₁ of the residual carbon content are calculated using a mathematical formula based on the graph G1 shown in FIG.

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

  First, the engine oil is filled into the coaxial resonator 2. For example, the engine oil 100 is filled up to the upper end portion 4 a of the inner conductor 4, and the upper end surface of the inner conductor 4 and the liquid level 100 a of the engine oil 100 coincide with each other. As a result, the outer peripheral surface of the inner conductor 4 is all in contact with the engine oil 100.

  Next, a microwave is transmitted from the analyzer 16. At this time, for example, a microwave having a frequency of 2.45 GHz is transmitted. The microwave transmitted from the analyzer 16 is transmitted to the inner conductor 4 through the coaxial cable 15. The microwave transmitted to the inner conductor 4 enters the engine oil 100 from the bottom 6 of the engine oil reservoir.

  The microwave is propagated through the engine oil 100 in the direction of the axis L1, reflected by the liquid level 100a of the engine oil 100 corresponding to the tip of the inner conductor 4, and opposite to the direction of the axis L1 in the engine oil 100. , Reaches the bottom 6 of the engine oil reservoir, and is received by the inner conductor 4. When the microwave propagates through the engine oil 100, the phase is shifted (delayed) or the amplitude is attenuated. The reflected wave W <b> 2 reaching the bottom 6 is received by the inner conductor 4 and is received by the analyzer 16 through the coaxial cable 15.

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

  Subsequently, the determination unit 18 determines whether or not the engine oil 100 has deteriorated based on the phase difference or amplitude difference of the microwaves. The determination unit 18 uses the graph G1 shown in FIG. 2 to grasp the concentration of the residual carbon contained in the engine oil 100, and the engine oil 100 is deteriorated when the concentration of the residual carbon is equal to or higher than the determination threshold. It is determined that Or the determination part 18 grasps | ascertains the density | concentration of the residual carbon content contained in the engine oil 100 using the graph G2 shown in FIG. 3, and when the density | concentration of a residual carbon content is more than a determination threshold value, the engine oil 100 Is determined to be deteriorated. The determination threshold is a value that serves as an index when determining the replacement time of the engine oil 100, and is determined by comparison with a reference unused engine oil (virgin oil), past results, experiments, and the like. Can do.

  Moreover, the determination part 18 measures the metal powder (Fe) density | concentration [ppm] contained in the engine oil 100 based on the density | concentration of the grasped residual carbon content. The metal powder contained in the engine oil 100 is generated by wear of metal parts (for example, piston, cylinder, connecting rod, crankshaft, pin, gear, etc.) when the engine is driven. is there. The determination unit 18 calculates the metal powder concentration using the graph G3 that shows the relationship between the increase in residual carbon content and the metal powder concentration shown in FIG. Moreover, the determination part 18 may determine with the engine oil 100 having deteriorated, when a metal powder density | concentration is more than a determination threshold value.

  When the oil property sensor 1 determines that the engine oil 100 has deteriorated, the oil property sensor 1 notifies the determination result. For example, the warning lamp is turned on to notify that the engine oil 100 has deteriorated. Or you may alert | report a determination result, for example using a liquid crystal display device. The oil 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 property sensor 1 of the present embodiment, the deterioration of the engine oil 100 can be determined by measuring the phase difference or the attenuation of the amplitude of the microwave propagated through the engine oil 100. The oil property sensor 1 can measure the phase difference or amplitude difference of the microwave even when the engine oil contains impurities. The oil physical property sensor 1 can measure the residual carbon content of the engine oil 100 and can improve the determination accuracy of the deterioration of the engine oil 100.

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

  In the oil property sensor 1, the incident wave W1 incident from the bottom 6 of the oil reservoir and the reflection that has propagated through the engine oil 100 and reflected at the liquid level 100a corresponding to the tip of the internal conductor and reached the bottom 6 Since the phase difference or 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 ensure the length of propagation of the microwave. Thereby, the coaxial resonator 2 is prevented from being enlarged and the measurement accuracy is improved. According to the oil property sensor 1, the coaxial resonator 2 can be easily mounted on the vehicle by downsizing the coaxial resonator 2.

  In the oil property sensor 1, the upper end portion 5b of the outer conductor 5 protrudes upward from the upper end portion 4a of the inner conductor 4, and the inner diameter Da of the outer conductor is a length of 1/2 or less of the wavelength of the microwave. Therefore, the microwave leaking to the outside of the external conductor 5 can be reduced, and the influence of the microwave on the external device can be suppressed.

  The present invention is not limited to the above-described embodiments, and various modifications as described below are possible without departing from the gist of the present invention.

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

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

  Further, in the above embodiment, the engine oil 100 is filled up to the height of the upper end portion 4a of the inner conductor 4, but the engine oil 100 is injected to a position lower than the upper end portion 4a and the oil property sensor 1 is used. Alternatively, the engine oil 100 may be injected up to a position higher than the upper end portion 4a. In addition, if the liquid level 100a of the engine oil 100 and the upper end part 4a of the internal conductor 4 coincide, the measurement accuracy of the residual carbon content can be improved.

  When the “oil level” is lower than the “upper end portion 4a of the inner conductor 4”, the distance that the inner conductor is in contact with the oil becomes shorter. There will be a part. On the other hand, when the “oil level” is higher than “the upper end 4a of the inner conductor 4”, there is oil that is not subjected to dielectric constant measurement.

  Further, in the above embodiment, the phase difference of the microwave is calculated by comparing the phase of the microwave transmitted from the transmission unit and the phase of the microwave received by the reception unit. Or the previous value) is stored in the storage unit, and the microwave phase (initial value or previous value) stored in the storage unit, and the microwave phase received by the receiving unit in the subsequent measurement, , 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 value (initial value or previous value) stored in the storage unit is compared with the amplitude of the microwave received by the reception 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 the oil.

  In the above embodiment, the case where the deterioration of the engine oil 100 is determined has been described. However, 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 ... Cylindrical body of support part, 10 ... Bottom cover, 13 ... insulator, 14 ... connector, 15 ... coaxial cable, 16 ... analyzer, 17 ... high frequency circuit (transmitter (microwave oscillator), receiver, measuring unit), 18 ... determining part (residual) Carbon component calculation unit, metal powder concentration calculation unit), 19: storage unit, 100: engine oil, Da: outer conductor inner diameter, L1: outer conductor axis, L2: length of upper end portion of outer conductor, W: micro Wave, W1... Microwave incident wave, W2... Microwave reflected wave.

Claims (6)

An oil storage section having a cylindrical outer conductor and a rod-shaped inner conductor disposed on the axis of the outer conductor inside the outer conductor and capable of storing oil between the outer conductor and the inner conductor Including a coaxial resonator,
A transmitter for transmitting the microwave incident on the oil via the inner conductor;
A receiving unit that receives the reflected wave of the microwave that has propagated through the oil and reflected at a position corresponding to the tip of the inner conductor via the base 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 reflected at the position and reaching the bottom of the oil reservoir. And an oil property sensor. In the direction in which the axis extends, the outer conductor projects to the opposite side of the bottom from the inner conductor,
2. The oil physical property sensor according to claim 1, wherein an inner diameter of the outer conductor is a length of ½ or less of a wavelength of the microwave.   3. The oil 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 oil based on at least one of the phase difference or the amplitude difference of the microwave measured by the measurement part. The oil 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 a 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 that stores a reference value that is information related to at least one of the phase difference or the amplitude difference of the microwave that has propagated the reference oil;
A determination unit that compares at least one of the phase difference or the amplitude difference measured by the measurement unit and the corresponding reference value stored in the storage unit to determine deterioration of the oil; The oil property sensor according to any one of claims 1 to 5.

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