Integrated in-line oil monitoring apparatus

Various embodiments of an oil monitoring apparatus are provided. In one embodiment, an oil monitoring apparatus includes a probe and an analyzing module in-line connected to the probe. The probe includes: a first sensor for measuring respective optical intensities of a light passing through the oil at respective red, green and blue wavelength ranges; a second sensor for measuring a water content; and a third sensor for measuring a temperature of the oil. The analyzing module calculates and monitors chemical deterioration of the oil, total contamination of the oil, a relative saturation of the oil by water and temperature of the oil based on the output signals of the first and third sensors. The oil monitoring apparatus monitors various parameters relating to the deterioration of the oil and to the physical properties of the oil.

The present application claims priority from Korean Patent Application No. 10-2008-0015944, filed Feb. 21, 2008, the entirety of which is hereby incorporated by reference.

BACKGROUND

Historically, oil analysis was an off-site strategy handled by commercial laboratories. However, oil analysis has recently been viewed as a tool for managing a core asset, and on-site oil analysis has experienced rapid growth in many industrial fields.

As technology has advanced, more low-priced sensors have been introduced in the market. The purpose of these sensors is to measure the conditions of a machine in real-time and to provide analysts with highly reliable detailed information on the service life of the machine. However, analysis techniques using such sensors usually only measure a single parameter. Also, such techniques require use of the same lubricant or assume no machinery malfunctions during the measurement of a single parameter. As a result, such single-parameter sensors merely provide a narrow view on quality and/or health of a lubricant. However, it is virtually impossible to assess accurate lubricant health and to predict service intervals therefore by sensing a single parameter of the lubricant. Accordingly, to unambiguously identify any damage to the machine or the deteriorated state of the oil, it is important to measure a set of as many different parameters as possible. An integrated monitoring system may provide estimation of oil conditions/contamination and wear particle contents of oil in real time. Such a system may have directly built-in oil circulation lines of a machine or may be used like portable detectors in fields and laboratories. To monitor critical and expensive equipment, diagnostics based on standard oil parameters is needed in a number of cases.

In this regard, U.S. Pat. No. 6,561,010 describes a machine fluid analysis system that measures oil parameters similar to those obtained by standard laboratory machine fluid analysis. The system includes a viscometer (for viscosity), an energy dispersive X-ray fluorescence (EDXRF) spectrometer utilizing isotopic or X-ray tube X-ray sources (for elemental analysis), non-dispersive IR/visible light meter (for oxidation, nitration and turbidity). Analyzed oil is fed from monitored equipment through oil line/pipe to the system. The oil passes through a cooler before feeding into the EDXRF. Measurement of viscosity provides an indication of possible dilution of the oil by fuel or water. Viscosity can also indicate oil degradation from heat or oxidation. Chemical degradation of the oil (oxidation, nitration, etc.) is commonly determined by IR spectrometric analysis, as well as TAN and TBN analyses for the oil. Water in the oil is also detected by IR analysis. Slow coolant leaks into the lubricating oil system may be detected by EDXRF analysis of Boron, Chromium or other elements such as Iodine or Strontium added to the coolant water as salts. A controller that includes a microprocessor, memory, digital input/output, analog input, and mass storage, is used for controlling the system and collecting measured data. A modem is used to make on-board in situ information available to a remote observer of machine health. The system can provide a reliable conclusion to health condition of machine. However, due to its complexity and high price, the system is rather restrictively employed and may only be justified for monitoring critical industry equipment.

Further, as a state-of-the-art technology, modular systems with low cost sensors, which are sensitive elements integrated on a single substrate, have been developed. For example, U.S. Pat. No. 6,286,363 and U.S. Patent Application Publication No. 2005-0072217 describe a modular lubrication sensor, which is made using integrated circuit-like microfabrication techniques (silicon-based fabrication and deposition techniques). The lubrication sensor includes a semiconductor silicon base, on which a pH sensor, a chemical sensor, an electrical conductivity sensor and a temperature sensor are deposited. The pH sensor includes a reference electrode made of AgCl and a pH electrode made of palladium-palladium oxide (Pd—PdO). The chemical sensor is of a 3-electrode configuration, which includes a working electrode made of Ag, a reference electrode made of AgCl, and a counter electrode made of Ag. When either an AC or DC voltammetric signal is applied to the working electrode, a response current is generated between the working electrode and the counter electrode. The response current signal parameters vary depending upon the electrochemical processes occurring at the surface of the working electrode. The electrochemical processes are a function of the constituent concentrations, and the response current is therefore responsive to these concentrations. The electrochemical sensor determines the presence of water or oxidation in the lubricant. The electrical conductivity sensor consists of two electrodes and made of gold. The conductivity is used to determine metal wear and/or water present in the lubricant. The temperature sensor is platinum zone patterned on the base in accordance with a predetermined length, width and surface area.

Other modular sensors, which use a similar integrated circuit technology, are available in the market, but their reliability is rather low.

Consequently, there remains a strong need to develop reliable sensors, which provide adequate information and diagnostic capability, in order to develop modular systems with multi-function outputs.

SUMMARY

Various embodiments of an oil monitoring apparatus are provided. In one embodiment, by way of non-limiting example, an oil monitoring apparatus includes: a housing, a first sensor, a second sensor, a third sensor and a control unit including a processor. The housing may be mounted to a member containing oil therein so as to be in contact with the oil. The first sensor may be mounted to the housing and may include an optical passing element, a light-emitting means and a color-sensing means. The optical passing element may have an interface being in contact with the oil. The light-emitting means may emit a light to the optical passing element. The color-sensing means may measure respective optical intensities at respective red, green and blue wavelength ranges of a light passing through the oil via the optical passing element and the interface and output respective signals. The second sensor may be mounted to the housing for measuring a water content of the oil and outputting a signal. The third sensor may be mounted to the housing for measuring a temperature of the oil and outputting a signal. The processor may be configured to calculate a ratio value and a variation value from the output signals of the color-sensing means. The ratio value may be defined by a ratio of an optical intensity at the red wavelength range to an optical intensity at the green wavelength range. The variation value may be defined by respective variations in optical intensity at the respective red, green and blue wavelength ranges between an initial condition and a current condition of the oil. The processor may be configured to further calculate a relative saturation of the oil by water from the output signals of the second sensor and a temperature value of the oil from the output signals of the third sensor. The processor may be configured to monitor the ratio value, the variation value, the relative saturation and the temperature value.

In another embodiment, an oil monitoring apparatus including a probe and an analyzing module is provided. The probe may include: a housing mounted to a member containing oil therein so as to be in contact with the oil; a first sensor mounted to the housing for measuring optical intensities of a light passing through the oil and outputting signals; a second sensor mounted to the housing for measuring a water content of the oil and outputting a signal; and a third sensor mounted to the housing for measuring a temperature of the oil and outputting a signal. The first sensor may includes: an optical passing element with an interface being in contact with the oil; a light-emitting means for emitting a light to the optical passing element; and a color-sensing means for measuring respective optical intensities at respective red, green and blue wavelength ranges of a light passing through the oil via the optical passing element and the interface and outputting respective signals. The analyzing module may be configured to analyze conditions of the oil. The analyzing module may be in-line connected to the sensors. The analyzing module may include a control unit including a processor for calculating the output signals of the first to third sensors. The processor may be configured to calculate a first parameter and a second parameter from the output signals of the first sensor, a third parameter from the output signals of the second sensor and a fourth parameter from the output signals of the fourth sensor. The first parameter may be defined by a ratio value of an output at the red wavelength range to an output at the green wavelength range. The second parameter may be defined by a variation value in optical intensity at the respective red, green and blue wavelength ranges between an initial condition and a current condition of the oil. The third parameter may be defined by a relative saturation of the oil by water. The fourth parameter may be defined by a temperature of the oil. The processor may be configured to compare the first to fourth parameters with respective threshold values thereof.

DETAILED DESCRIPTION

A detailed description may be provided with reference to the accompanying drawings. One of ordinary skill in the art may realize that the following description is illustrative only and is not in any way limiting. Other illustrative embodiments may readily suggest themselves to such skilled persons having the benefit of this disclosure.

The oil monitoring apparatus of the present disclosure may measure and monitor deterioration of oil and physical properties of the oil that can affect operation of equipment using the oil in real-time. To measure such deterioration and physical properties of the oil, the oil monitoring apparatus of the present disclosure may utilize four parameters that define the deterioration and the physical properties of the oil. The first parameter may be associated with chemical deterioration such as oxidative and thermal deterioration. The second parameter may be associated with total contamination of the oil, which results from physical contaminants (e.g., worn out particles, bubbles, etc.) and chemical contaminants (e.g., by-products caused by oxidative and thermal deterioration). The third parameter may be associated with relative saturation (RS) of oil by water, which can corrode the equipment. The fourth parameter may be associated with oil temperature, which can degrade the quality of the lubrication oil or otherwise cause damage by misalignment of the equipment. In embodiments of the oil monitoring apparatus, data for determining those parameters may be obtained in real time and on-site through a detecting device mounted on a component of the equipment containing the oil therein. An analyzing device, which may be connected to the detecting device in-line, may produce and monitor each of the parameters from the obtained data.

FIG. 1is a schematic block diagram showing an illustrative embodiment of the oil monitoring apparatus according to the present disclosure. Referring toFIG. 1, oil monitoring apparatus10may include: a module100for calculating the four parameters and analyzing states of the oil (hereinafter referred to as analyzing module100); and a probe200for detecting deterioration and physical properties of the oil. It is understood that probe300or probe400may also be interchangeably used in place of probe200(such interchangeability hereinafter indicated as “probe200,300or400”). Oil monitoring apparatus10may be attached to equipment using and monitoring the oil. Such equipment may include, but is not limited to, a hydraulic system, a transformer, a turbine, a compressor, a gasoline engine, a diesel engine, etc. The oil may include, but is not limited to, hydraulic oil, transformer oil, turbine oil, compressor oil, engine oil, various lubricating oil, etc.

Probe200,300, or400may be mounted to a wall of an oil tank21, which may be attached to equipment using the oil and contain oil30therein. Probe200,300, or400may be provided with first, second and third sensors for detecting the current conditions of the oil and outputting signals. The signals outputted from the first, second and third sensors may be transferred to analyzing module100and be processed therein. Analyzing module100may monitor the deterioration of the oil as well as variation in physical properties of the oil, which can affect the operations of the equipment, in real-time based on the output signals of the sensors.

It is illustrated inFIG. 1that probe200,300, or400is mounted to oil tank21. However, probes200,300, or400may be attached to an oil circulation line, an oil circulation pipe and the like (equipment that utilizes the oil to be analyzed).

FIGS. 2 to 4show embodiments of the probe which may be equipped to the oil monitoring apparatus of the present disclosure. Probe200shown inFIG. 2may be used for the purposes of monitoring oil having a low light absorption such as hydraulic oil, a transformer oil, a turbine oil, a compressor oil, etc. Probes300and400shown inFIGS. 3 and 4respectively may be used for the purposes of monitoring oil having a high light absorption in a visible light waveband such as diesel engine oil.

Referring toFIG. 2, probe200may include: a housing210for mounting the sensors thereon; first sensor220for measuring the chemical deterioration and the total contamination of the oil; second sensor230for measuring the water content of the oil; and third sensor240for measuring the temperature of the oil.

Housing210may be mounted to a member configured to contain the oil (e.g., a wall of the oil tank21) so as to be in contact with oil30. Alternatively, if probe200is attached to the oil circulation line or the oil circulation pipe, housing210may be mounted to such a line or pipe so as to be in contact with the oil thereinside.

Housing210may have a first sensor receiving portion211and a second sensor receiving portion212at a portion of the housing contacting the oil. First sensor220may be disposed in the first sensor receiving portion211, while the second and third sensors230and240may be disposed in the second receiving portion212respectively. Sensor receiving portions211and212may be configured to be recessed from a surface of housing210. When probe200is installed in oil tank21containing oil30, the oil may be filled into first and second sensor receiving portions211and212.

Housing210may have a thread210aaround a portion of its outer periphery. An insertion hole21awith a thread corresponding to thread210amay be formed at the oil tank21. Housing210may be threadably-engaged to insertion hole21aand may be secured to the wall of oil tank21through a nut254. An O-ring253or other type of gasket may be disposed between nut254and housing210to prevent oil leak therebetween.

The oil monitoring apparatus may monitor the conditions of the oil using four parameters (i.e., the chemical deterioration of the oil, the total contamination of the oil, the water content of the oil, and the temperature of the oil). The data for determining those four parameters may be outputted to analyzing module100by sensors220,230and240of probe200. Analyzing module100may calculate and monitor those four parameters based on the output signals of sensors220,230and240to inform a user of the current conditions of the oil in real-time. It may further inform a user of the optimal time for oil exchange intervals and the operative states of the equipment by comparing those parameters with preset threshold values. Herein, the chemical deterioration of the oil may be referred to as a first parameter, the total contamination of the oil may be referred to as a second parameter, the water content of the oil may be referred to as a third parameter, and the temperature of the oil may be referred to as a fourth parameter. Specifically, the first parameter may be defined by chromatic ratio (CR), the second parameter may be defined by total contamination index (TCI), the third parameter may be defined by relative saturation (RS) of the oil by water, and the fourth parameter may be defined by oil temperature (T). The first parameter may indicate the chemical deterioration of the oil. The second parameter may indicate the total contamination of the oil, which is caused by the physical contaminants and the chemical contaminants.

The data for determining the first and second parameters may be obtained from first sensor220. First sensor220may include: an optical passing element221; light-emitting means222for emitting light to optical passing element222; and color-sensing means223for measuring optical intensities of the light passing through optical passing element221and outputting signals associated therewith. The light emitted for light-emitting means222may pass through the oil by a thickness t and enter color-sensing means223.

In this embodiment, optical passing element221may be comprised of first and second optical windows221aand221b. First and second optical windows221aand221bmay have an interface221a′ and221b′ for contacting oil30, respectively. First optical window221amay be disposed at one side of first sensor receiving portion221, while second optical window221bmay be disposed at the opposite side of first sensor receiving portion221so as to be opposed to first optical window221a. Light-emitting means222may contact a face of first optical window221a, which is opposite to interface221a′. Color-sensing means223may contact a face of second optical window221b, which is opposite to interface221b′.

Light-emitting means222may be constructed to emit light having spectrums of a red waveband (or wavelength range), a green waveband and a blue waveband (e.g., white light or visible light). The red waveband of the light emitted from light-emitting means222may be in the range of from about 590 nm to about 750 nm. Also, the green waveband may be in the range of from about 490 nm to about 610 nm, and the blue waveband may be in the range of from about 400 nm to about 510 nm. Alternatively, light-emitting means222may emit such a light in a pulsed manner. The light emitted from light-emitting means222may pass through first optical window221a, oil30of the thickness t and second optical window221bone after another and then enter color-sensing means223. Color-sensing means223may measure each optical intensity of the light having passed through second optical window221bat each of the red waveband, the green waveband and the blue waveband and may output respective signals corresponding thereto.

The data for determining the third parameter may be obtained from second sensor230. Further, the data for determining the fourth parameter may be obtained from third sensor240. Second sensor230and third sensor240may be disposed in second sensor receiving portion212and be attached to the housing by epoxy or other adhesive.

A first sensor receiving portion211and second sensor receiving portion212may be provided with protective meshes251252, respectively, which may protect the sensors situated in the sensor receiving portions against mechanical damages and isolate the sensors from bubbles.

Wires extending from sensors220,230and240may be connected to a circuit board (not shown) located in a cover part260coupled to one side of housing210. A wire270may extend from cover part260and may be connected to analyzing module100. Light-emitting means222, color-sensing means223, second sensor230and third sensor240may be connected to a PCB with a preamplifier mounted therein via a wire255. The PCB may be located in cover part260.

In probe200for monitoring oil having a low light absorption shown inFIG. 2, first sensor220may measure the optical intensity of the light passing through the oil of the measurement thickness t. Typically, in monitoring oil having a high light absorption (e.g., diesel oil), if the measurement thickness through which light passes is substantially thick, then the emitted light may be absorbed in large quantities causing some difficulty in precisely measuring its optical intensity. It is also difficult to have a very small measurement thickness to avoid such a problem, in view of fabrication issues. Even if it can be made small, there is the additional problem of the oil not easily entering the narrow measurement thickness. Accordingly, in monitoring oil having a high optical absorption, there is a need to form a consecutive small measurement thicknesses to enhance precision of the measurement. In this regard, in this embodiment, the probe for monitoring the oil having a high light absorption at a visible light waveband may utilize a total internal reflection (TIR) technique. This allows measuring an optical ray, which passes through thin oil layers for measurement while undergoing the total internal reflection.

FIG. 3is a schematic sectional view of the probe300for monitoring the oil having a high light absorption in a visible light waveband (e.g., diesel oil). InFIG. 3, like reference numerals refer to like elements in comparison with the probe200of the first embodiment.

Referring toFIG. 3, probe300may include: a housing310for mounting the sensors thereon, housing310being mounted to a wall of oil tank21so as to be in contact with the oil; a first sensor320for measuring the chemical deterioration and the total contamination of the oil; second sensor230for measuring the water content of the oil; and third sensor240for measuring the temperature of the oil.

Housing310may include: a fixing portion311with a thread311afor fixation to the oil tank21; an insertion portion312inserted in fixing portion311for situating the light-emitting means and the color-sensing means therein; a bush portion313contacted to insertion portion312in fixing portion311for disposing optical fibers therein; and a hollow portion314for disposing an optical passing element therein. One end of hollow portion314may be contacted to bush portion313, while the opposite end thereof may become a free end. A plurality of through-holes314cmay be formed through hollow portion314such that oil30flows in and out therethrough.

First sensor320may include: optical passing element321along which a light passes through the oil of a predetermined thickness; light-emitting means222for emitting the light to optical passing element321; color-sensing means223for measuring the optical intensities of the light having passed through optical passing element321and outputting signals associated therewith; a first optical fiber324afor optically connecting optical passing element321and light-emitting means222; and a second optical fiber324bfor optically connecting optical passing element321and color-sensing means223.

Optical passing element321may have an interface321afor contacting to oil30. Optical passing element321may have a cylindrical shape and may be made from optical glass having refractive index higher than that of oil30(particularly, borosilicate glass BK8). One end of the optical passing element321may be brought into contact with first and second optical fibers324a,324ba in bush portion313. The opposite end of optical passing element321may be coupled to an inner wall surface of hollow portion314. The one end of optical passing element321may be optically transparent. Optical passing element321may be positioned such that it is optically connected to bifurcated first and second optical fibers324a,324bat its one end. The opposite end of optical passing element321cmay be coated with a light-reflection member. When probe300is installed to oil tank21, oil30comes into contact with interface321aof the optical passing element through through-holes314cof the hollow portion.

First optical fiber324amay be connected to the one end321bof the optical passing element at its one end and to light-emitting means222at its other end. Second optical fiber324bmay be connected to one end321bof the optical passing element at its one end and to color-sensing means223at its other end. The light emitted from light-emitting means222may pass through first optical fiber324aand then enters optical passing element321. The incident light may pass through optical passing element321while totally reflecting at interface321aof optical passing element321. While the incident light totally reflects at interface321a, a certain amount of the light infiltrates into the oil and is then absorbed thereinto. Thus, the optical intensity of the light, which totally reflects at interface321a, is decreased. The incident light reflects at opposite end321cof the optical passing element and then passes while totally reflecting again, to enter color-sensing means223through one end321bof optical passing element321via second optical fiber324b.

Optical passing element321may have a suitable ratio of diameter to length so that optical attenuation effects can be accumulated. Preferably, optical passing element321may have a ratio of diameter to length equal to or higher than 10 such that the incident light can totally reflect more than three times.

Second sensor230and third sensor240may be disposed in a sensor receiving portion314bformed at the opposite end of hollow housing314. A sensor receiving portion314bmay be provided with a protective mesh352, which may protect second sensor230and third sensor240against mechanical damages and isolate them from bubbles.

FIG. 4shows another probe400for monitoring oil having a high light absorption at a visible light waveband (e.g., diesel oil). InFIG. 4, like reference numerals refer to like elements in comparison with probe200of the first embodiment and probe300of the second embodiment.

Referring toFIG. 4, probe400may include: a housing410for mounting sensors thereon, housing410being mounted to a wall of oil tank21so as to be in contact with oil30; a first sensor420for measuring the chemical deterioration and the total contamination of the oil; second sensor230for measuring the water content of the oil; and third sensor240for measuring the temperature of the oil.

Housing410may include: a fixing portion411with a thread411afor fixation to oil tank21; and an insert412, which is fixed to fixing portion411, and in which first sensor420is disposed. Insert412may be inserted in a first sensor receiving portion411bformed at fixing portion411and is fixed thereto. Fixing portion411may have a second sensor receiving portion411cfor disposing second and third sensors230,240therein at its opposite end.

First sensor420may include: an optical passing element421along which a light passes through the oil of a predetermined thickness; light-emitting means222for emitting the light to optical passing element421; and color-sensing means223for measuring the optical intensities of the light having passed through optical passing element421and outputting signals associated therewith.

Optical passing element421may have a hexahedral or polyhedral shape. Optical passing element421may be made from optical glass having a refractive index higher than that of oil30(e.g., N-SF6 (n=1.81) from SCHOTT GLASS). One face of optical passing element421may comprise an interface421afor contacting to oil30. Optical passing element421may have a light-incident face421band a light-outgoing face421c. Preferably, a ratio of length to thickness of optical passing element421may be equal to or higher than 10 to provide the total internal reflection three times or more.

Light-incident face421bof optical passing element421may be chamfered off with respect to interface421asuch that it lies perpendicularly to an optical axis222aof the light emitted from light-emitting means222. Light-outgoing face421cof optical passing element421may be chamfered off with respect to interface421asuch that it lies perpendicularly to an optical axis223aof light entering the color-sensing means223. Chamfered light-incident face421band chamfered light-outgoing face421cmay be formed so as to satisfy the condition of the total internal reflection.

Second sensor230and third sensor240may be disposed in second sensor receiving portion411cand are attached thereto by epoxy or another adhesive.

At first and second sensor receiving portions411b,411cprotective meshes451and452may be provided respectively, which may protect the sensors situated in the sensor receiving portions against mechanical damages and isolate the sensors from bubbles.

Wires extending from the sensors may be connected to analyzing module100via a plate414fixed to insert412and a cover260.

FIG. 5illustrates the total internal reflection in probes300or400shown inFIGS. 3 and 4.

In probe300or400, the optical light ray emitted from the light-emitting means222may be incident on the interface between optical passing element321,421(i.e., cylindrical optical passing element321or hexahedral optical passing element421, which is made from optical glass having a refractive index of n1) and the oil (i.e., an external medium having a refractive index of n2). In such a case, when an incident angle θi of the incident light may exceed a critical angle θcr of the total internal reflection, as can be seen from the following Equation (1), the optical light ray may pass through the optical passing element without substantial loss of power while undergoing the total internal reflection.
θi≧θcr=arcsin(n2/n1)  Eq. (1)

The losses of radiation during the total internal reflection may take place due to the absorption in the optical passing element medium and the penetration into the external medium (i.e., oil). In the total internal reflection, the incident light may penetrate into the external medium (i.e., oil) by a depth h. The penetration depth h may be calculated by the following Equation (2). For instance, it may be about 1 μm.

h=λn12·2⁢⁢π·(n12·sin2⁢θt-n22)1/2Eq.⁢(2)
wherein λ is an optical wavelength of the incident light.

As shown in the following Equation (3), a total length t (i.e., measurement thickness of oil), by which the light passing through the optical passing element penetrates into the oil, may be a product of the double depth h and the number k of the reflections which may occur at the interface between the oil and the optical passing element.
t≈2hk  Eq. (3)

In probes200,300,400of the oil monitoring apparatus according to the present disclosure, light-emitting means222may include, but is not limited to, a RGB LED such as B5-4RGB-CBA from Roithner Lasertechnik, or a white LED from Marl Optosource Co. Color-sensing means223may include, but is not limited to, a color sensor (particularly, a 3-component color sensor) such as MCS3AT/BT from MAZeT Gmbh or TCS230 from Texas advanced optoelectronic solutions Inc.

In embodiments of the present disclosure, the light, which may be emitted from light-emitting means22(particularly, the RGB LED or the white LED) to pass through the oil with the measurement thickness t, may be incident to color-sensing means223(particularly, the color sensor), which may measure optical intensities at three wavebands (i.e., red, green and blue wavebands). Color-sensing means223may measure respective optical intensities at those three wavebands and output signals associated therewith to a processor111of a control unit110(seeFIG. 6). Processor111may calculate the above-described four parameters.

The calculation of the first to fourth parameters will be described below.

The first parameter may be associated with the oxidative and thermal deterioration of the oil. First sensor220,320,420may measure the optical intensities at each of the red, green and blue wavebands from the light that passes through the oil after being emitted from light-emitting means222.

Korean Patent No. 10-0795373 discloses a technology which measures chromatic ratio (CR) as a parameter associated with oxidative and thermal deterioration of oil and measures change in optical intensities of oil at three wavebands as a parameter associated with total contamination of oil. As for mineral oil, it is known in the art that the intensity in optical spectrum of the light passing through the oil becomes strong at a longer waveband with the progress of the oxidative and thermal deterioration of the oil.

The first parameter, which may be defined by the chromatic ratio, may be a ratio of the optical intensity at the red waveband to that at the green waveband of the light having passed through the oil. The chromatic ratio may be determined using the output URat the red waveband and the output UGat the green waveband from the color-sensing means, as shown in the following Equation (4).

Such chromatic ratio parameter may become high as an oil service time becomes longer. That is, as the optical intensity at the red waveband of the light passing through the oil becomes larger than the optical intensity at the green waveband with the progression of the chemical deterioration of the oil, the output URin the red waveband of the color-sensing means may become larger than the output UGin the green waveband.

The total contamination of the oil may depend on the content of oxidation and aging products, contaminating dust, wear debris, air bubbles and etc. in the oil. The second parameter associated with the total contamination of the oil may be evaluated by comparing the change in optical intensity of used oil with that of fresh oil. The second parameter may be defined by a total contamination index (TCI) at said three wavebands. The TCI may be evaluated as the changes in optical intensity at said three wavebands (i.e., red (ΔDR), green (ΔDG) and blue (ΔDB)) as shown in the following Equations (5), (6) and (7).

In the above Equations 5 to 7, DR, fresh, DG, freshand DB, freshdenote the optical intensities of the fresh oil at the red, green and blue wavebands respectively, while DR, used, DG, usedand DB, useddenote the optical densities of the used oil at the red, green and blue wavebands respectively. UR, fresh, UG, freshand UB, freshdenote the output signals at the red, green and blue wavebands respectively in the fresh oil test, while UR, used, UG, usedand UB, useddenote the output signals at the red, green and blue wavebands respectively in the used oil test.

Meanwhile, the Equation (2) shows that the penetration depth h depends on the wavelength λ. This fact should be taken into account in design of probes300,400using the TIR technique. Thus, normalization to a unified penetration depth h (particularly, to the penetration depth of the light at the red waveband) may be performed.

The TCI in the i-th (i.e., red, green and blue) waveband may be determined as the change in optical intensity ΔDias shown in the following Equation (8).

Δ⁢⁢Di=ln⁡(Ui,freshUi)=ln⁡(Ai·ⅇ-λi⁢2⁢⁢k⁢⁢αi,0Ai·ⅇ-λi⁢2⁢⁢k⁢⁢αi)=-λi·2·k·(αi,0-αi)Eq.⁢(8)
wherein αi, 0and αiare an absorption coefficient of the fresh oil and the used oil in the i-th waveband, Aiis an optical intensity of the white LED in the i-th waveband, and k is the number of the light reflections occurring between the oil and the interface of the optical passing element.

In case the white LED is applied as the light-emitting means and the MCS3AT is applied as the color-sensing means, an average wavelength of the red waveband may be about 640 nm, that of the green waveband may be 560 nm and that of the blue waveband may be about 460 nm.

To normalize the optical intensities to the penetration depth of the red waveband (i.e., to depth h=k·λR), in the case of the TCI at the green waveband, the optical intensity at the green waveband DGmay be multiplied by a ratio of 640/560=1.14 and, in the case of the TCI at the blue waveband, the optical intensity at the blue waveband DBmay be multiplied by a ratio 640/460=1.39.
TCIR=ΔDREq. (9)
TCIG=ΔDG,norm=ΔDG·1.14  Eq. (10)
TCIB=ΔDB,norm=ΔDB·1.39  Eq. (11)

In the course of the CR calculation in probes300or400using the total internal reflection technique, the normalization of the measured outputs in the green and blue wavebands may be performed by employing relative values as follows. The measured outputs in the green and red wavebands may be as the following Equations (12) and (13).
UG,fresh=SG·AG·e−λGkαG,0
UG=SG·AG·e−λGkαGEq. (12)
UR,fresh=SR·AR·e−λRkαR,0
UR=SR·AR·e−λRkαREq. (13)

wherein SGand SRare sensitivities of the color-sensing means in the green and red wavebands, UG,freshand UR,freshare outputs from the fresh oil and UGand URare outputs from the used oil.

Relative change of the outputs in the used oil outputs to the outputs in the fresh oil outputs may be as the follow Equation (14).

The relative output in the green waveband, which is normalized to the penetration depth h, may be as the following Equation (15).

Thus, in the case employing the probes300or400using the TIR technique, the CR may be defined as a ratio of the relative output in the red waveband to the normalized relative output in the green waveband, as shown in the following Equation (16).

Second sensor230, which may be mounted to housing210,310or410, may include, but is not limited to, an air humidity sensor (e.g., HIH-3610 from Honeywell Inc.). Such a sensor may use a thermoset polymer, three layer capacitance construction and silicon-integrated platinum electrodes of an on-chip type. Output signal of such a sensor may be voltage (U). In order to calculate the relative saturation (RS), the following Equation (17) may be used.
U=Usupply·(0.0062·RSx+0.16) at 25° C.  Eq. (17)

wherein Usupplyis a supplied voltage.

The output of all absorption-based humidity sensors (e.g., capacitive, bulk resistive, conductive film, etc.) may be affected by temperature. For this reason, temperature compensation may be applied using the following Equation (18).

wherein RS is a true relative saturation and T is temperature in ° C.

Based on the Equations (17) and (18), control unit110may calculate the water content in oil with percentage as the RS parameter (i.e., the third parameter) and outputs the result thereof.

While such an air humidity sensor has a protective polymer layer, it is unsuitable to be used as an oil moisture sensor. The Honeywell data shows the results of chemical resistivity test of such an air humidity sensor. It is clear from said data that such an air humidity sensor needs additional protection against contamination caused by oil. Accordingly, in certain embodiments, in order to solve such a problem, an oleophobic coating may be additionally applied on the protective layer of the existing HIH-3610 air humidity sensor. Particularly, Novec Coating EGC-1720 (3M Co.), which is clear and low viscosity solution of a fluorosilane polymer carried in a hydrofluoroether solvent, may be used for the additional coating.

Third sensor240, which is mounted to probes200,300or400, may serve to determine the temperature of the oil. Third sensor240may include, but is not limited to, a Temperature-to-Voltage Converter (e.g., TC1047 from Microchip). The TC1047 is a linear voltage output temperature sensor, the output voltage of which is directly proportional to the measured temperature. The TC1047 may measure temperature ranging from −40° C. to 125° C. The output voltage U may vary along with temperature change T as shown in the following Equation (19).

Control unit110may calculate the oil temperature in centigrade degrees and outputs the result thereof.

Analyzing module100will be described in detail with reference toFIGS. 1 and 6.

Analyzing module100may include control unit110, a sensor monitoring unit120, a signal calibrating unit130, a signal adjusting unit140, a display unit150and a communication unit160.

Control unit110may perform control on general operations of oil monitoring apparatus10. Control unit110may include processor111, a memory112, an ADC113, a DAC114and a programmable gain amplifier115.

Processor111may control operations of probes200,300,400. Processor111may be pre-programmed so as to process the output signals of the sensors for calculating the chromatic ratio (the first parameter), the total contamination index (the second parameter), the relative saturation of oil by water (the third parameter) and the oil temperature (the fourth parameter). Further, the processor111may control sensor monitoring unit120, signal calibrating unit130and signal adjusting unit140and sends data to display unit150and communication unit160through hardware interface.

Memory112may serve to store program codes for carrying out oil condition measurement in real time, which are executed by the processor111. Memory112may be used to store initial information on the fresh oil or operational parameters such as oil oxidation and total contamination parameters of the fresh oil, nominal water content, lubricant temperature, etc. Further, memory112may contain threshold values of measured parameters so as to determine suitability of the oil to be analyzed.

Sensor monitoring unit120may monitor optical radiation levels of light-emitting means222. Sensor monitoring unit120may include a feedback photodiode121(seeFIGS. 2 to 4), an amplifier122and a current driver123. Feedback photodiode121may serve as means for measuring optical radiation, which measures the optical radiation levels of light-emitting means222and outputs signals, for purposes of feedback control for equalizing the optical intensities of light-emitting means222. Sensor monitoring unit120may increase current to increase the optical intensities when the intensities of the light radiated from light-emitting means222are weak. When the intensities are strong, sensor monitoring unit120may decrease current to equalize the intensities of the light radiated from light-emitting means222. Feedback photodiode121may be positioned adjacent to light-emitting means222of probe200,300or400. A silicon photodiode (more particularly, photodiode SP-1ML from Kondenshi Corp.) may be used as the feedback photodiode121. The optical radiation of light-emitting means222may be measured by feedback photodiode121. The output signals of feedback photodiode121may enter the processor111via amplifier122and ADC113. Processor111may compare those output signals with the initial value stored in memory112and then feeds a result signal associated therewith to a current driver of light-emitting means222of probe200,300or400through DAC114.

Signal calibrating unit130may include three amplifiers131and three programmable feedback regulators132. Signal calibrating unit130may calibrate sensitivities of first sensors220,320or420, thereby allowing oil having different grades and oil being in a wide range of contamination level to be tested. To this end, it the output signals of color-sensing means223should be calibrated so that they can remain between a minimal level (e.g., 1000 mV) and a maximal level (e.g., 200 mV) of a pre-set value. When the output signals of color-sensing means223from the oil to be tested are too weak or too strong, feedback regulator132may be operated by processor111and therefore a final output signal may be automatically adjusted such that it can be in a range of the minimal level from about 1000 mV to the maximal level of about 2000 mV. Accordingly, various oils in wide contamination levels can be tested. The calibration technique may be as follows. The output signals of color-sensing means223may enter amplifiers131of signal calibrating unit130at the time of each light pulse of light-emitting means222. The output signal of amplifier131may enter processor111via programmable gain amplifier115and ADC113. The signal value may be compared with the minimal and maximal levels of the preset critical value at processor111. If the signal value is less or higher than the minimal and maximal levels of the critical value, then a gain of programmable gain amplifier115may be correspondingly increased or decreased. To adjust the output signal into the range between the levels of the pre-set value, a programmable feedback regulator based on digital potentiometer (e.g., Single Digital Potentiometer MCP41100 with SPI interface from Microchip Technology Inc.) may be additionally applied. The programmable feedback regulator may be controlled by processor111. When the output signals are between the minimal and maximal levels of the critical value, the first parameter of the chromatic ratio and the second parameter of the total contamination indexes may be calculated and results therefrom may be outputted.

Signal adjusting unit140may include three drift eliminators141. Signal adjusting unit140may adjust outputs so as to eliminate drift (shift) of “zero levels” of signals caused by temperature instability, ambient light and other effects. The adjustment may be performed as follows. The outputs of color-sensing means223at the respective R, G and B wavebands may be measured at time period between the light pulses of light-emitting means222. The measured outputs may be compared with prescribed zero levels for three channels (R, G and B). The difference therebetween may be adjusted to null by drift eliminators141. Digital potentiometers (more particularly, Single Digital Potentiometer MCP41100 with SPI interface, Microchip Technology Inc.), which are controlled by control unit110according to software, may be used as drift eliminator141.

Analyzing module100may further include display unit150for displaying information relating to the condition of the oil. Display unit150may include a monitor151and an operator input detector. A Liquid Crystal Display (LCD) may be used as monitor151, but is not limited thereto. Monitor151may function to show the four parameters produced by calculating data obtained via probe200,300or400. Particularly, monitor151may present a set of oil condition parameters such as the chromatic ratio, the water content, the total contamination indexes at three R, G and B wavebands and the oil temperature. The operator input detector may include a keypad152, which enables a user to input data, information, function commands, etc. Keypad152may include three key buttons comprised of the following: a “Reset” button serving to interrupt and restart software execution; a “Save Data” button configured to be pushed in order to write a data of oil to memory when a user plans to employ reference data such as fresh oil data; and a “Reference Data” button allowing user to read the data from the memory. Display unit150may further include an alarm indicator153for indicating alarm when the oil reaches any critical conditions. Alarm indicator153may include one or more light-emitting diodes (LEDs). For example, alarm indicator153may include a tri-state LED displaying green, yellow or red colors depending on the health state of the lubricant.

Analyzing module100may further include communication unit160for communication with a host computer. Communication unit160may include an interface161for communicating commands and parameter information between processor111and host computer. Interface161may be comprised of a hardware wire interface (e.g., RS-232 or USB standard)) or a hardware wireless interface (e.g., an interface including a radio transmitter, a radio receiver and an antenna). The wireless interface may eliminate costs, noise problems and other problems related with the wire interface. The data may be transmitted to the host computer to perform time-based trending and analysis to thereby determine oil condition, full equipment condition and optimal oil exchange interval. Meanwhile, analyzing module100may be constructed without the host computer. In such a case, all processing including data analyses may be accomplished by the processor and be displayed by display unit150.

An operating algorithm of one embodiment of the apparatus for integrated in-line oil monitoring according to the present disclosure will be described below.FIG. 7shows the output signals according to the algorithm.

The algorithm may include following steps.

Step 1. When the oil monitoring apparatus10is switched on, program may start and input data may be initialized. Light-emitting means222may be not energized.

Step 2. Three outputs UR, UG, UB(in the R, G and B wavebands) of probe200,300,400may be read. The drifts may be calculated as differences between the outputs and the prescribed “zero level” value U0. (UR—drift=UR−U0; UG—drift=UG−U0; UB—drift=UB−U0). Processor111may control a variation in resistance of the digital potentiometers of signal adjusting unit140while the drifts are eliminated. Besides, the output of feedback photodiode121may be read as U′F.

Step 3. Light-emitting means222may be energized and the output of feedback photodiode121of the sensor monitoring unit120may be read as U″F. A value of U″F−U′Fmay be calculated and compared with prescribed UF. The value U′Fmay be adjusted by a fed voltage under the control of the processor111while (U″F−U′F)=UF.

Step 4. Outputs UR, UG, UBof color-sensing means may be read and a maximal value Umaxmay be found from UR, UG, UB.

A) If this maximal value is exterior to prescribed range ΔUmax, then a resistance of the digital potentiometer of programmable feedback regulator131of signal calibrating unit130may be adjusted under the control of processor111while Umaxbelongs to the range ΔUmax. Light-emitting means222may be de-energized and Steps 2-3 may be repeated to verify all installation-specific settings.

B) If this maximal value is within the prescribed range ΔUmax, then outputs UR, UG, UBof color-sensing means223may be accumulated and the number of reading i may be increased by 1. Then, light-emitting means222may be de-energized and the outputs URSof second sensor230and the outputs UTof third sensor240may be read and the outputs UR, UG, UB, URS, UTmay be sent to the host computer. Steps 2-4 may be repeated while the number of reading becomes 127.

Step 5. Calculation of average values of UR, UG, UB, URSand UTobtained by 128 readings may be performed. By using the average values, the first parameter (CR), the second parameter (TCI), the third parameter (RS) and the fourth parameter (T) may be calculated according to the above Equations 4-7, 9-11 and 13-15.

Step 6. The first to fourth parameters may be displayed.

Step 7. The measured parameters may be compared with the prescribed threshold values and decision on the oil condition and the equipment condition may be made.

Step 8. The oil condition and the equipment condition may be outputted through alarm indicator153.

FIGS. 8 and 9are graphs showing road test results of a diesel engine oil (API CH-4 10W/30), which was taken from a diesel car at different run distances. A full run distance of the car was 9750 km before the test. This corresponds to a run distance of 0 km in the illustrated graphs. Each volume of a sample was 300 ml. When sampled, the same volume (300 ml) of fresh oil was added to a crankcase. The volume of the crankcase of the tested car was 6,000 ml. After 7thsampling (9247 km), the oil was exchanged. The first parameter of CR and the second parameter of TCI were measured by the oil monitoring apparatus employing the probe300of the second embodiment in a laboratory. The probe was submerged in the oil sample contained in a glass beaker. A TAN (Total Acid Number), which may be determined by titration method, is a measure of a concentration of acidic decomposition products existing in the oil. The TAN are expected to increase along with the oil degradation.FIG. 8shows correlation between the first parameter of CR and the TAN. It is evident from the correlation between the CR and the TAN that the CR gives reliable estimation of chemical oil condition. Further, soot content was estimated by an Infacal Soot Meter (Wilks Enterpricse Inc.) as a major contaminant of diesel oil.FIG. 9shows correlation between the second parameter of TCI and read values from the Soot Meter (soot concentration).

In embodiments of the present disclosure, the calculated chromatic ratio CR and total contamination indexes TCIR, TCIGand TCIBmay estimate the chemical deterioration and total contamination of oil. The parameters CR, TCIR, TCIGand TCIBmay be displayed on the monitor151.

Measured values of the chromatic ratio CR and total contamination indexes TCIR, TCICand TCIBmay be compared with their preliminarily stored threshold values.

If the chromatic ratio CR is less than the threshold values, then the oil is evaluated to have a good chemical condition. If the chromatic ratio CR and the change in optical intensity at all wavelength range are above the threshold values, then the oil is in an unacceptable chemical condition.

If the changes in optical intensities at all wavelength ranges are below the threshold value, then the oil has a satisfactory level of total contamination. If the changes in optical intensity at all wavelength ranges are above the threshold value, then the oil has an unacceptable level of total contamination.

If the chromatic ratio and the changes in optical intensity in the blue, green and red wavelength ranges are below their threshold values, then the oil has a good condition. If the chromatic ratio and the changes in optical intensity in the blue, green and red wavelength ranges are above their threshold values, then the oil is determined to be in an unacceptable condition.

Embodiments of the present disclosure may provide an oil monitoring apparatus. The oil monitoring apparatus may monitor simultaneously and successively various parameters, which are related to the deterioration of the oil and to the physical properties of oil for estimating the operation of equipment utilizing the oil, by means of a single detecting device. The oil monitoring apparatus may estimate an optimal time of oil exchange and the operation of the equipment in real time and in a timely manner.