JP2006349634A - Method for detecting particle concentration - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a particle concentration detection method, capable of suppressing detection error resulted from the component ratio of particles in a liquid in detection of a particle concentration in the liquid based on a transmitted light quantity. <P>SOLUTION: Visible light is emitted from a visible light emission part 12a1 toward lubricating oil, and a visible light transmittance (visible light transmission quantity I1/visible light emission quantity Io1×100) at that time is calculated. Infrared light is emitted from an infrared light emitting part 12a2 toward the lubricating oil, and an infrared light transmittance (infrared light transmission quantity I2/infrared light emitting quantity Io2×100) at that time is calculated. Based on an equation showing the relation of the ratio of visible light transmittance to infrared light transmittance (visible light transmittance T1/ray transmittance T2) with the particle concentration of the lubricating oil, more specifically, based on an approximation of particle concentration using the logarithm of the ratio of transmittance as a variable, the particle concentration of the lubricating oil is detected. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a particle concentration detection method for detecting the particle concentration of the liquid based on the transmitted light quantity of the liquid.

  For example, a method is known in which the concentration of particles in a liquid, such as the concentration of soot mixed in engine lubricating oil, is detected based on the light transmission characteristics of the liquid, specifically, the amount of light transmitted through the liquid. Yes. In this detection method, light is emitted from the light emitting unit toward the liquid, and the amount of transmitted light that passes through the liquid is detected by the light receiving unit. A part of the light emitted from the light emitting part is absorbed and scattered by particles mixed in the liquid, so that the amount of transmitted light detected by the light receiving part corresponds to the amount of particles in the liquid. Therefore, the particle concentration can be detected based on the transmitted light amount.

  Here, the component ratio of the particles contained in the lubricating oil varies depending on the type of the lubricating oil, the operating state of the engine, the progress of deterioration of the lubricating oil, and the like. This particle component ratio affects the amount of light scattering and absorption in the lubricating oil, so even if the amount of particles contained in the lubricating oil is the same, that is, the particle concentration is the same, the component ratio of the same particle If they are different, the amount of transmitted light changes. Therefore, the particle concentration detection based on the amount of transmitted light can detect the particle concentration in a simpler mode compared to the particle concentration measurement method such as the centrifugal separation method. There is a problem that it is easily received and inferior in detection accuracy.

  Therefore, in the method described in Patent Document 1, when detecting the degree of deterioration of the lubricating oil having a correlation with the particle concentration or the like by using such light transmission characteristics, by detecting the deterioration in the following manner, The detection accuracy of the degree of deterioration is increased.

  In the method described in this document, light transmission characteristics (absorbance or transmitted light amount) of the lubricating oil at each wavelength are measured using light of short wavelength and long wavelength, respectively, and based on the light transmission characteristics measured at each wavelength. It is determined whether the progress of deterioration of the lubricating oil is initial deterioration, intermediate deterioration, or late deterioration. Then, select a calibration curve (a line indicating the correspondence between the absorbance and the degree of deterioration) optimized for the determined deterioration progress state, and use the calibration curve and the light transmission characteristics measured with light of a short wavelength. Therefore, the deterioration degree of the lubricating oil is obtained.

According to the method described in the document, a calibration curve for determining the degree of deterioration of the lubricating oil is selected according to the deterioration progress state that affects the component ratio of the particles in the lubricating oil. The influence of the ratio on the light transmission characteristics can be suppressed to some extent.
JP-A-8-62207

  Here, in the method described in Patent Document 1, the light transmission characteristic measured with light of a short wavelength is used when obtaining the degree of deterioration based on the calibration curve. Therefore, even if the influence of the particle component ratio on the calibration curve can be suppressed by switching the calibration curve according to the deterioration progress state, the light transmission characteristic as a reference value has an error caused by the particle component ratio. Will be included. For this reason, when the liquid particle concentration is detected in the same manner as in the same document, the detection error due to the component ratio of the particles in the liquid cannot be suppressed, and the detection accuracy is naturally limited.

  The present invention has been made in view of such circumstances, and an object thereof is to suppress detection errors caused by the component ratio of particles in the liquid when detecting the particle concentration in the liquid based on the amount of transmitted light. It is to provide a particle concentration detection method.

The means for achieving the above object and the effects thereof will be described below.
In the first aspect of the present invention, the amount of transmitted light transmitted through the liquid by irradiating the liquid from the light emitting unit is measured by the light receiving unit, and the concentration of particles mixed in the liquid based on the measured transmitted light amount In the particle concentration detection method for detecting the light, the transmitted light amount of the liquid at each wavelength is measured using light of different wavelengths, the transmittance is calculated for each measured transmitted light amount, and the ratio of the respective transmittances The gist of the present invention is to detect the particle concentration of the liquid based on a preset relational expression.

  When the present inventor detects the particle concentration in the liquid based on the transmitted light amount, the detection error due to the particle component ratio of the liquid can be suppressed by using the transmitted light amount respectively measured with light of different wavelengths. I found out.

  More specifically, the transmitted light amount of the liquid at each wavelength is measured using light of different wavelengths, and the transmittance is calculated for each measured transmitted light amount. The transmittance is a value defined by a ratio between the light emission amount of the light emitting unit and the light reception amount of the light receiving unit (light reception amount of the light receiving unit / light emission amount of the light emitting unit × 100 (%)). Then, the ratio of the respective transmittances calculated for each transmitted light amount is obtained, and is an expression showing the relationship between the transmittance ratio and the particle concentration, and the liquid particle concentration is calculated based on a preset relational expression. It has been found that detection error due to the component ratio of particles in the liquid can be suppressed when detecting the particle concentration.

  According to the above method for detecting the particle concentration in such a manner, when detecting the particle concentration in the liquid based on the amount of transmitted light, it is possible to suitably suppress the detection error due to the component ratio of the particles in the liquid. .

  The inventor has also confirmed that the relationship between the logarithm of the transmittance ratio and the particle concentration has a strong correlation. Therefore, according to the invention described in claim 2, an approximate expression of the particle concentration using the logarithm of the transmittance ratio as a variable is obtained, and the approximate expression as the above relational expression showing the relationship between the transmittance ratio and the particle concentration. By using this, it is possible to appropriately detect a highly accurate particle concentration in which detection errors due to the component ratio of particles in the liquid are suppressed.

  As in the third aspect of the present invention, a cubic function expression of the particle concentration using the transmittance ratio as a variable is obtained, and the function expression is used as the relational expression indicating the relationship between the transmittance ratio and the particle concentration. Even if it is used, it becomes possible to appropriately detect a highly accurate particle concentration in which detection errors due to the component ratio of particles in the liquid are suppressed.

  As the light of the different wavelengths, it is desirable to use short wavelength light scattered and absorbed by particles in the liquid and long wavelength light scattered by the particles. As described in the invention, by using visible light as short-wavelength light and using infrared light as long-wavelength light, detection errors due to the component ratio of particles in the liquid can be appropriately suppressed. It becomes like this.

  According to the invention described in claim 5, light having a wavelength of 600 nm to 700 nm is used as the visible light, and as the infrared light according to invention described in claim 6, 800 nm to By using light having a wavelength of 1100 nm, it is possible to suitably measure the respective transmitted light amounts respectively measured with light of different wavelengths.

Hereinafter, an embodiment embodying a particle concentration detection method according to the present invention will be described with reference to FIGS.
FIG. 1 shows the configuration of a particle concentration detection apparatus used in the particle concentration detection method of this embodiment. The particle concentration detection apparatus uses the lubricating oil of an internal combustion engine as a liquid to be inspected, and detects the concentration of particles (for example, soot) mixed in the lubricating oil based on the amount of light transmitted through the lubricating oil. The particle concentration detection apparatus includes a detection mechanism 10, a calculation unit 20, a display unit 30, and the like.

  FIG. 2 shows an external view of the detection mechanism 10. The detection mechanism 10 is a mechanism that measures the amount of light transmitted through the lubricating oil that is the liquid to be inspected, and is largely a body 11, a detection unit 12 that measures the amount of light transmitted through the lubricating oil, and a container that contains the lubricating oil. The detachable cell 13 includes a power supply to the detection unit 12, an input / output port 14 from which a measurement signal is output from the detection unit 12, and the like.

  FIG. 3 shows the structure of the cell 13. The cell 13 includes a bottomed case 13a having an opening surface and a plate 13b for closing the opening surface. And after lubricating oil which is a liquid for inspection is put into case 13a, the lubricating oil is sealed in case 13a by plate 13b. The cell 13 is made of a material having a low light attenuation rate, such as quartz glass.

  FIG. 4 is a partial cross-sectional view of the body 11 and shows a cross-sectional structure of a portion A shown in FIG. As shown in FIG. 4, an insertion hole 15 into which the cell 13 can be inserted is formed in the body 11, and the cell 13 can be attached to and detached from the detection mechanism 10.

  The detection unit 12 configured in the body 11 includes a light emitting unit 12a that emits light and a light receiving unit 12b that receives the light, and the light emitting unit 12a has a wavelength as shown in FIG. Is composed of a visible light emitting unit 12a1 that emits visible light having a wavelength of 670 nm and an infrared light emitting unit 12a2 that emits infrared light having a wavelength of 890 nm.

  In addition, as shown in FIG. 5, the light receiving unit 12b receives the light emitted from the visible light emitting unit 12a1 and the red light receiving the light emitted from the infrared light emitting unit 12a2. The external light receiving unit 12b2 is configured.

  The light emitting portion 12a and the light receiving portion 12b are disposed so as to face each other with the insertion hole 15 interposed therebetween as shown in FIG. Further, the light emitting unit 12a and the light receiving unit 12b are arranged so that the optical path between the light emitting unit 12a and the light receiving unit 12b is orthogonal to the insertion direction of the cell 13. With this configuration, the cell 13 is detachable between the light emitting unit 12a and the light receiving unit 12b.

  The visible light emitting portion 12a1 is a portion that irradiates the lubricating oil with visible light, and includes a light emitting element, a light emitting lens, and the like. This light emitting element is an element that emits inspection light having a wavelength of 670 nm, and emits a constant amount of visible light when a predetermined current flows. In the present embodiment, an LED (light emitting diode) is used as the light emitting element. The light emitting element is provided with the light emitting lens, and the inspection light is converted into parallel light by the lens. That is, most of the light emitted from the light emitting element by the light emitting lens is directed to the visible light receiving unit 12b1 without being diffused. The infrared light emitting section 12a2 is visible light except that the light emitting element is an element that emits inspection light having a wavelength of 890 nm and the inspection light is directed to the infrared light receiving section 12b2. It has the same structure as the light emitting part 12a1.

  The visible light receiving portion 12b1 is a portion that detects the amount of inspection light emitted from the visible light emitting portion 12a1, and includes a light receiving element or the like. The light receiving element is an element that receives inspection light from the visible light emitting unit 12a1 and detects the amount of light, and the output increases as the amount of received light increases. In the present embodiment, a photodiode is used as the light receiving element. The output of the light receiving element is appropriately amplified by an amplifier circuit. The infrared light receiving unit 12b2 has the same structure as the visible light receiving unit 12b1 except that the infrared light receiving unit 12b2 is a part that detects the amount of inspection light emitted from the infrared light emitting unit 12a2.

  When the light emitting unit 12a emits light when the cell 13 is not inserted into the insertion hole 15, that is, when the cell 13 is not mounted between the light emitting unit 12a and the light receiving unit 12b, visible light is emitted. The light emission amount of the unit 12a1 (hereinafter referred to as the visible light emission amount Io1) is measured by the visible light receiving unit 12b1. Similarly, the light emission amount of the infrared light emitting unit 12a2 (hereinafter referred to as infrared light emission amount Io2) is measured by the infrared light receiving unit 12b2.

  On the other hand, when the light emitting unit 12a emits light in a state where the cell 13 is inserted into the insertion hole 15, that is, in a state where the cell 13 is mounted between the light emitting unit 12a and the light receiving unit 12b, lubricating oil is used. The transmitted light amount of the transmitted visible light (hereinafter referred to as visible light transmission amount I1) is measured by the visible light receiving unit 12b1. Further, the amount of infrared light transmitted through the lubricating oil (hereinafter referred to as infrared light transmission amount I2) is measured by the infrared light receiving unit 12b2.

  Here, the amount of transmitted light measured by the light receiving unit 12b is not only due to the particle concentration, but also due to changes in the characteristics of the detection unit 12, such as temperature characteristics of the light emitting unit 12a, dirt attached to the detection unit 12, or changes over time of the detection unit 12. Also changes. Therefore, in order to increase the detection accuracy of the particle concentration, it is desirable to suppress as much as possible the influence of the error due to the characteristic change of the detection unit 12. Therefore, in this embodiment, the transmittance when the lubricating oil is irradiated with visible light (hereinafter referred to as visible light transmittance T1) is expressed by the following formula (1) based on the visible light emission amount Io1 and the visible light transmission amount I1. ). Further, the transmittance when the lubricating oil is irradiated with infrared light (hereinafter referred to as infrared light transmittance T2) is expressed by the following equation (2) based on the infrared light emission amount Io2 and the infrared light transmission amount I2. I want to ask from. As is well known, the transmittance is a value defined by the ratio of the amount of light emitted from the light emitting unit to the amount of received light from the light receiving unit (the amount of light received by the light receiving unit / the amount of light emitted from the light emitting unit × 100 (%)). As the particle concentration increases, the value decreases.

Visible light transmittance T1 = visible light transmission amount I1 / visible light emission amount Io1 × 100 (%) (1)

Infrared light transmittance T2 = Infrared light transmission amount I2 / Infrared light emission amount Io2 × 100 (%) (2)

The visible light emission amount Io1 indicates the light emission amount of the visible light emission unit 12a1, and includes changes in the light emission amount and the light reception amount due to the characteristic change of the detection unit 12. Further, the visible light transmission amount I1 reflects the change in the light emission amount and the light reception amount due to the characteristic change of the detection unit 12 and the particle concentration in the lubricating oil. And in the detection part 12 comprised from the visible light light emission part 12a1 and the visible light light-receiving part 12b1, the amount of change of the visible light emission amount Io1 caused by the characteristic change and the visible light transmission caused by the characteristic change The amount of change of the quantity I1 is almost the same. Therefore, if the ratio between the visible light emission amount Io1 and the visible light transmission amount I1 is obtained, the change in the visible light emission amount Io1 and the change in the visible light transmission amount I1 can be offset, that is, Only the particle concentration of the lubricating oil is reflected in the visible light transmittance T1. Therefore, by obtaining the transmittance in the above-described manner, it is possible to suppress the influence of errors caused by the characteristic change of the detection unit 12 when detecting the particle concentration. Similarly, only the particle concentration of the lubricating oil is reflected in the infrared light transmittance T2, so that it is possible to suppress the influence of errors caused by the characteristic change of the detection unit 12.

  In this embodiment, the influence of the error due to the characteristic change of the detection unit 12 is suppressed with such an aspect, but the influence of such an error may be suppressed with another aspect. For example, visible light based on preset initial values of visible light emission amount Io1 and infrared light emission amount Io2 (emission amount when incorporated in the device, etc.) and the visible light transmission amount I1 and infrared light transmission amount I2. The transmittance T1 and the infrared light transmittance T2 may be obtained, respectively, and the visible light transmittance T1 and the infrared light transmittance T2 may be corrected by appropriate coefficients. Further, in some cases, such a measure for suppressing errors may be omitted.

  On the other hand, FIG. 6 schematically shows the tendency when the distance between the light emitting part and the light receiving part, that is, the optical path length is variously changed, regarding the relationship between the particle concentration of the lubricating oil and the transmittance. In FIG. 6, the values indicated by L1 to L7 represent various values of the optical path length set.

  As shown in FIG. 6, as the optical path length becomes shorter, the transmittance with respect to the particle concentration tends to increase, and the detectable particle concentration range tends to widen toward the high concentration region. In other words, the upper limit value of the detectable particle concentration tends to increase. This is because as the optical path length becomes shorter, the attenuation amount in the transmitted light amount becomes smaller and the light amount received by the light receiving unit increases.

  On the other hand, as the optical path length increases, the amount of attenuation in the transmitted light amount increases. Therefore, the change in light transmittance due to the difference in particle concentration is small in the high concentration region. For this reason, as the optical path length becomes longer, it becomes more difficult to detect the particle concentration in the high concentration region, and the detectable particle concentration range becomes narrower. However, as shown in FIG. 6, in the low concentration region, the change in light transmittance tends to increase as the optical path length increases, so that a slight difference in particle concentration is detected. Will be able to. That is, as the optical path length becomes shorter, a higher concentration of particle concentration can be detected. On the other hand, as the optical path length becomes longer, the particle concentration detection accuracy in the low concentration region can be further improved. Therefore, the particle concentration can be appropriately detected by appropriately setting or varying the optical path length according to the particle concentration range of the lubricating oil to be measured.

  Therefore, in the present embodiment, there are a plurality of cases 13a having different depths D in the case 13a of the cell 13 shown in FIG. 3, and various optical path lengths L shown in FIG. A plurality of different cases 13a are prepared. In detecting the particle concentration of the lubricating oil, the case 13a having a depth D suitable for the particle concentration range of the lubricating oil to be measured is used, and thereby a wide range of particle concentrations can be detected with high accuracy. To be able to. Incidentally, it is desirable to use a case 13a which is a lubricating oil for a gasoline engine and has a depth D of 0.2 mm when detecting a particle concentration in a range of 0 to 10 wt%.

  The arithmetic unit 20 includes a central processing control device (CPU), a read-only memory (ROM) that stores various programs and maps in advance, a random access memory (RAM) that temporarily stores CPU calculation results, an input interface, and an output. It is mainly composed of a microcomputer equipped with an interface. The calculation unit 20 calculates a particle concentration of the lubricating oil by calculating a signal output from the input / output port 14 of the detection mechanism 10, and outputs the calculation result, for example, the detected particle concentration to the display unit 30. indicate.

Next, the particle concentration detection method of the lubricating oil performed by the calculation unit 20 and the particle concentration detection method in the present embodiment will be described with reference to FIGS.
In general, in the case of a lubricating oil for an internal combustion engine, the components of particles mixed in the oil as it deteriorates include carbonyl groups, nitro groups, benzene nuclei, sulfates, soot, and wear powder. The component ratio of such particles varies depending on the type of lubricating oil, the type of internal combustion engine, the operating state of the engine, the progress of deterioration of the lubricating oil, and the like. By the way, the carbonyl group and nitro group are brown, and the benzene nucleus, sulfate, soot, and wear powder are black. Therefore, if the composition ratio of such particles is different, the color of the lubricating oil will be different.

  The light incident on the lubricating oil passes through the liquid as it is without hitting particles in the liquid such as a sludge precursor, or passes through the liquid while being scattered multiple times. Visible light has the property of being absorbed by the color of the particles when multiple scattered, while infrared light has the property of not being absorbed by such multiple scattering.

  FIG. 7 shows the wavelength characteristics of the transmittances of two kinds of deteriorated oils having almost the same particle concentration and different particle component ratios. As shown in FIG. 7, for the deteriorated oil A and the deteriorated oil B having almost the same particle concentration, the transmittance of the deteriorated oil A is smaller than the transmittance of the deteriorated oil B in the visible light region. On the other hand, in the infrared light region, the transmittance of the deteriorated oil A is larger than the transmittance of the deteriorated oil B, and it can be seen that the magnitude relationship of the transmittance changes depending on the wavelength of the inspection light. Since the deteriorated oil A has a lower visible light transmittance than the deteriorated oil B, it is considered that there are many particles that serve as light absorbing components, for example, black particles.

  Thus, the component ratio of the particles in the lubricating oil affects the amount of light scattering and absorption in the lubricating oil. Accordingly, even if the amount of particles contained in the lubricating oil is the same, that is, the particle concentration is the same, the amount of transmitted light changes if the component ratio of the particles is different. Therefore, the particle concentration detection based on the amount of transmitted light can detect the particle concentration in a simpler mode compared to the particle concentration measurement method such as the centrifugal separation method. There is a problem that it is easily received and inferior in detection accuracy. Therefore, in this embodiment, when detecting the particle concentration in the lubricating oil based on the transmitted light amount, as described below, the transmitted light amount of the lubricating oil at each wavelength is measured using light of different wavelengths. ing. Then, by detecting each particle concentration using each transmittance calculated from each measured transmitted light amount, a detection error of the particle concentration due to the component ratio of the particles in the liquid is suppressed.

First, using the Lambert-Beer law, the transmittance of the liquid is expressed by the light absorption term and the scattering term as shown in the following equation (3).

Ln (1 / T) = {ε (λ) × C × L} + {G (λ) × C × L} (3)
Ln: natural logarithm
T: Liquid transmittance ε (λ): Absorption coefficient of particles at wavelength λ of light G (λ): Dimming coefficient of particles at wavelength λ of light
C: Particle concentration
L: Optical path length

In Equation 3, the term “{ε (λ) × C × L}” is an absorption term, and the term “{G (λ) × C × L}” is a scattering term.

  Visible light emitted toward the lubricating oil from the visible light emitting unit 12a1 is classified into a scattering component, an absorption component, and a transmission component. Therefore, the visible light transmittance T1 can be expressed by the following equation (4) from the above equation (3).

Ln (1 / T1) = {ε (670) × C × L} + {G (670) × C × L} (4)
T1: Transmittance when the lubricating oil is irradiated with light having a wavelength of 670 nm
(= Visible light transmission amount I1 / visible light emission amount Io1 × 100)
ε (670): Absorption coefficient of particle at light wavelength of 670 nm G (670): Light attenuation coefficient of particle at light wavelength of 670 nm

On the other hand, the infrared light irradiated toward the lubricating oil from the infrared light emitting unit 12a2 is classified into a scattering component and a transmission component. Therefore, the infrared light transmittance T2 can be expressed as the following equation (5) from the above equation (3).

Ln (1 / T2) = G (890) × C × L (5)
T2: Transmittance when the lubricating oil is irradiated with light having a wavelength of 890 nm
(= Infrared light transmission amount I2 / Infrared light emission amount Io2 × 100)
G (890): Particle extinction coefficient at light wavelength of 890 nm

Next, the difference between the above formula (4) and formula (5) is obtained, and the particle concentration C is summarized as the following formula (6).

この式（６）に示されるように、粒子濃度Ｃは、透過率の比と粒子濃度Ｃとの関係を示す式であって予め設定可能な関係式から求めることができる。より具体的には、可視光透過率Ｔ１と赤外光透過率Ｔ２と比の対数を変数とする近似式から粒子濃度Ｃを求めることができることを本発明者は見出した。

As shown in this equation (6), the particle concentration C is an equation showing the relationship between the transmittance ratio and the particle concentration C, and can be obtained from a relational equation that can be set in advance. More specifically, the present inventor has found that the particle concentration C can be obtained from an approximate expression using the logarithm of the ratio of the visible light transmittance T1 and the infrared light transmittance T2 as a variable.

  Therefore, the present inventor collects various lubricating oils having different particle component ratios and particle concentrations from the market, and measures the visible light transmittance T1 and the infrared light transmittance T2 for each of these lubricating oils to measure each of them. The logarithm of the transmittance ratio was calculated, and the actual particle concentration of the lubricating oil that was the calculation target of the logarithm of the transmittance ratio was measured by a centrifugal separation method. FIG. 8 is a scatter diagram showing the correspondence between the logarithm of the transmittance ratio and the actual particle concentration, which is the measurement result. In addition, the actual particle concentration here has shown the insoluble content concentration by n pentane insoluble content. As shown in FIG. 8, the logarithm of the transmittance ratio represented by “−Ln (T1 / T2)” and the actual particle concentration have a strong correlation, and the correlation coefficient is “0.99”. "Met. Moreover, the regression equation regarding the measurement result of FIG. 8 is shown in the following equation (7).

Particle concentration C = 54264 × {−Ln (T1 / T2)} (7)

This equation (7) matches the equation (6) in which the value of α is “54264”.

  Thus, even if the component ratio of particles is different, the logarithm of the transmittance ratio and the actual particle concentration are strongly correlated, and by detecting the particle concentration based on the logarithm of such a transmittance ratio, The present inventor confirmed that the detection error caused by the particle component ratio of the lubricating oil can be suppressed.

  That is, when detecting the particle concentration in the lubricating oil based on the transmitted light amount, the present inventor uses the transmitted light amount measured with light of different wavelengths to detect the particle component ratio of the lubricating oil. We found that the error can be suppressed.

  More specifically, the transmitted light amount of the lubricating oil at each wavelength is measured using light of different wavelengths, and the transmittance is calculated for each measured transmitted light amount. Then, the ratio of each transmittance calculated for each transmitted light amount is obtained, and the particle concentration C of the lubricating oil is detected based on the relational expression indicating the relationship between the transmittance ratio and the particle concentration. It has been found that when detecting the concentration C, detection errors due to the component ratio of the particles in the liquid can be suppressed.

  Therefore, in the particle concentration detection method according to the present embodiment, the correspondence relationship between the particle concentration C and the ratio of each transmittance shown by the equation (7) or the equation (6) is mapped and stored in the ROM. . Then, the visible light transmittance T1 and the infrared light transmittance T2 when the lubricating oil is irradiated with visible light and infrared light are respectively calculated, and the visible light transmittance T1 and the infrared light transmittance T2 are calculated. Based on the ratio, the particle concentration C is obtained by referring to the map stored in the ROM.

  FIG. 9 shows the detection result of the particle concentration C by the particle concentration detection method of the present embodiment. FIG. 9 shows the actual oil concentration measured by the centrifugal separation method and the particles detected by the present detection method for lubricating oils collected from the market and having different particle component ratios and particle concentrations. It is a scatter diagram showing the correspondence with density C. As shown in FIG. 9, the actual particle concentration and the particle concentration C detected by the present detection method have a strong correlation, and the correlation coefficient is “0.96”. From this result, it was confirmed that the detection error caused by the component ratio of the particles in the liquid can be suppressed by using this detection method when detecting the particle concentration C of the lubricating oil based on the transmitted light amount.

As described above, according to the present embodiment, the following effects can be obtained.
(1) The transmitted light amount of the lubricating oil at each wavelength is measured using light of different wavelengths, the transmittance is calculated for each measured transmitted light amount, and the ratio between the respective transmittances and the particle concentration C The particle concentration C is detected based on a relational expression that is a relational expression that is set in advance. Therefore, when detecting the particle concentration C of the lubricating oil based on the amount of transmitted light, it is possible to suitably suppress a detection error caused by the component ratio of the particles in the liquid.

  (2) The present inventor confirmed that the relationship between the logarithm of the transmittance ratio and the particle concentration C has a strong correlation. Therefore, an approximate expression of the particle concentration using the logarithm of the transmittance ratio as a variable is obtained, and the approximate expression is used as the relational expression indicating the relationship between the transmittance ratio and the particle concentration. Therefore, it is possible to appropriately detect a highly accurate particle concentration in which detection errors due to the component ratio of the particles in the liquid are suppressed.

  (3) As the light of the different wavelength, short wavelength light scattered and absorbed by particles in the liquid and long wavelength light scattered by the particles are used. More specifically, visible light is used as short-wavelength light, and infrared light is used as long-wavelength light, which results in the component ratio of particles in the liquid in this detection method. Detection error can be suppressed appropriately.

In addition, the said embodiment can also be changed and implemented as follows.
-Visible light and infrared light are emitted from two light emitting parts such as the visible light emitting part 12a1 and the infrared light emitting part 12a2, respectively, but the visible light emitting element and the infrared light emitting element are provided in one light emitting part. And visible light and infrared light may be emitted from the same light emitting unit.

  -Although light having a wavelength of 670 nm is used as visible light, even if light having a wavelength in the range of 600 nm to 700 nm is used as the visible light, each transmitted light amount measured with light of a different wavelength is used. Therefore, it is possible to appropriately measure, and the same effect as in the above embodiment can be obtained.

  Although light having a wavelength of 890 nm is used as infrared light, each of the transmissions measured with light having different wavelengths can be used even if light having a wavelength in the range of 800 nm to 1100 nm is used as the infrared light. The amount of light can be suitably measured, and the same effect as in the above embodiment can be obtained.

  In the above embodiment, light having two different wavelengths is used, but light having three or more different wavelengths may be used. In this case, for example, the particle concentration can be detected in the following manner. First, the amount of transmitted light at each wavelength is measured using light of three wavelengths such as A, B, and C, and the transmittance for each wavelength is determined from the measured amount of transmitted light. Then, the particle concentration C1 is obtained from the ratio of the transmittance corresponding to the light having the wavelengths A and B, and the particle concentration C2 is obtained from the ratio of the transmittance corresponding to the light having the wavelengths A and C. The average value of the concentration C2 may be the final particle concentration C.

  -Visible light and infrared light are used as light of different wavelengths, but when detecting the particle concentration in the detection mode described in the above embodiment, detection errors due to the component ratio of particles in the liquid are suppressed. If possible, light of other wavelengths may be used.

  The correspondence relationship between the particle concentration C and the ratio of each transmittance shown in the above equations (7) and (6) is mapped and stored in the ROM, and the particle concentration C is obtained based on the map. I did it. Instead of this, the particle concentration C may be obtained directly from the relational expression between the transmittance ratio and the particle concentration C shown in the equations (7) and (6).

  In the above embodiment, α in Equation (6) is “54264”. However, this value is only an example, and when the particle concentration C is obtained based on the logarithm of the transmittance ratio, other values may be used as long as the accuracy can be improved appropriately. .

  In the above embodiment, the relational expression indicating the relationship between the transmittance ratio and the particle concentration, which is a preset relational expression, is an approximate expression of the particle concentration using the logarithm of the transmittance ratio as a variable. However, other relational expressions may be used as the relational expression indicating the relation between the transmittance ratio and the particle concentration. For example, even when a cubic function expression of the particle concentration C using the transmittance ratio as a variable is obtained and the function expression is used as the relational expression indicating the relationship between the transmittance ratio and the particle concentration C, The present inventor has confirmed that the particle concentration C obtained from the functional equation is strongly correlated with the actual particle concentration. Therefore, even when such a cubic function equation is used, it is possible to appropriately detect a highly accurate particle concentration in which a detection error due to the component ratio of the particles in the liquid is suppressed. Incidentally, a cubic function formula in this case, an example of which is shown by the following formula (8).

・上記セル１３の構造は一例である。要は、発光部１２ａ及び受光部１２ｂの間を着脱可能であって、潤滑油を入れることができる構造を有しているものであればよい。

The structure of the cell 13 is an example. In short, what is necessary is just to have the structure which can attach or detach between the light emission part 12a and the light-receiving part 12b, and can put lubricating oil.

-You may make it make the detection part 10 incorporate the calculating part 20 and the display part 30. FIG.
-Moreover, the said particle | grain concentration detection apparatus is an example. In short, any particle concentration detection apparatus including a detection unit capable of measuring the amount of transmitted light of lubricating oil at each wavelength using light of different wavelengths and a configuration corresponding to the calculation unit 20 will be included in the present invention. Such a particle concentration detection method can be similarly applied.

  In the above embodiment, the particle concentration of the lubricating oil of the internal combustion engine is detected. However, the present invention can be similarly applied to the case of detecting the particle concentration of another liquid.

In one embodiment concerning the particle concentration detection method of the present invention, the schematic diagram showing the composition of the particle concentration detection device used for the method. FIG. 3 is an external view of a detection mechanism in the same embodiment. FIG. 3 is a structural diagram of a cell in the same embodiment. Sectional drawing of the A section shown in FIG. The schematic diagram which shows the structure of the detection part in the embodiment. The graph which shows the aspect at the time of changing various optical path lengths about the relationship between the particle | grain density | concentration of lubricating oil, and the transmittance | permeability. The graph which shows the wavelength characteristic of those transmittance | permeability about two types of deteriorated oil from which the component ratio of particle | grains differs. A scatter diagram showing the correspondence between the logarithm of the transmittance ratio and the actual particle concentration. The scatter diagram which shows the correspondence of the particle concentration C detected by this detection method, and an actual particle concentration.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Detection mechanism, 11 ... Body, 12 ... Detection part, 12a ... Light emission part (12a1 ... Visible light emission part, 12a2 ... Infrared light emission part, 12b ... Light reception part (12b1 ... Visible light reception part, 12b2 ... Infrared (Light receiving part), 13 ... cell, 13a ... case, 13b ... plate, 14 ... input / output port, 15 ... insertion hole, 20 ... calculation part, 30 ... display part.

Claims (6)

In the particle concentration detection method of irradiating the liquid from the light emitting unit and measuring the transmitted light amount transmitted through the liquid with the light receiving unit, and detecting the concentration of the particles mixed in the liquid based on the measured transmitted light amount,
The amount of transmitted light of the liquid at each wavelength is measured using light of different wavelengths, the transmittance is calculated for each measured amount of transmitted light, and the relationship between the ratio of each transmittance and the particle concentration is shown. A particle concentration detection method comprising: detecting a particle concentration of the liquid based on a relational expression set in advance. The particle concentration detection method according to claim 1, wherein the relational expression is an approximate expression of the particle concentration using a logarithm of the transmittance ratio as a variable. The particle concentration detection method according to claim 1, wherein the relational expression is a cubic function expression of the particle concentration using the transmittance ratio as a variable. The particle concentration detection method according to claim 1, wherein visible light and infrared light are used as the light having different wavelengths. The particle concentration detection method according to claim 4, wherein light having a wavelength of 600 nm to 700 nm is used as the visible light. The particle concentration detection method according to claim 4, wherein light having a wavelength of 800 nm to 1100 nm is used as the infrared light.

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