Oil concentration measuring device and oil concentration measuring method

Abstract

This invention provides an oil concentration measuring device and an oil concentration measuring method. An oil concentration measuring device for cleaning solutions is provided that does not require expensive spectroscopic elements, detection elements, etc. The oil concentration measuring device (10) comprises: a light irradiation unit (104) that irradiates the target liquid (cleaning solution) with irradiation light having a measurement wavelength, the measurement wavelength being a predetermined wavelength between 280 nm and 300 nm; a transmitted light detection unit (105) that measures the intensity of transmitted light obtained by the irradiation light passing through the target liquid; and an oil concentration determination unit (1061) that calculates the absorbance of the target liquid at the measurement wavelength based on the intensity of the transmitted light measured by the transmitted light detection unit (105), and determines the oil concentration in the target liquid based on the absorbance value and a calibration curve representing the relationship between the oil concentration at the measurement wavelength and the absorbance.

Description

[0001] This application is a divisional application of the invention patent application with application number 201780048765.4, application date July 31, 2017, entitled "Oil Concentration Measuring Device and Oil Concentration Measuring Method". Technical Field

[0002] This invention relates to an apparatus and method for measuring the concentration of oil in a cleaning fluid. The oil concentration measuring apparatus and method are preferably used in industrial cleaning machines to measure the concentration of oil contained in cleaning fluids in use, such as those used to remove cutting oil, pressurizing / stamping oil, machine oil, grease, flux, and other oils adhering to workpieces. Background Technology

[0003] Hydrocarbon cleaning fluids are the mainstream choice for industrial cleaning machines. Hydrocarbon cleaning fluids do not contain ozone-depleting substances or chlorine, thus having the advantage of minimal impact on the environment and human health. Furthermore, by utilizing the fact that the boiling point of hydrocarbons is lower than that of the aforementioned oil components, hydrocarbon cleaning fluids also have the advantage of being able to be regenerated by distillation after accumulating the hydrocarbon cleaning fluid containing used oil components in a distillation tank and heating it to a temperature higher than the boiling point of hydrocarbons but lower than the boiling point of the oil components. Hydrocarbon cleaning fluids also have the advantage of being able to use the clean steam generated during this distillation regeneration process for cleaning and drying workpieces (hereinafter referred to as "steam cleaning / drying"). In steam cleaning / drying, the workpiece is placed in a steam cleaning / drying tank, and the surface of the workpiece is cleaned by introducing steam into the tank. Then, the pressure in the tank is rapidly reduced, causing the boiling point of the cleaning agent to drop sharply. This causes the cleaning agent adhering to the workpiece surface to boil violently / vaporize, thereby drying the workpiece. In actual industrial cleaning machines, the workpiece is placed in a liquid cleaning tank containing hydrocarbon cleaning fluid for liquid cleaning, followed by meticulous steam cleaning / drying.

[0004] When industrial cleaning machines are operated continuously, the oil removed by distillation gradually accumulates in the distillation tank, causing oil to mix into the vapor of the hydrocarbon cleaning solution obtained from distillation regeneration (regenerated cleaning solution). This results in oil in the steam adhering to the surface of the workpiece during steam cleaning / drying, leading to a decrease in cleaning effectiveness. To prevent this decrease in cleaning effectiveness, the oil concentration in the regenerated cleaning solution needs to be suppressed to below a specified concentration. This specified concentration varies depending on the composition of the oil, but to prevent a decrease in cleaning effectiveness regardless of composition, it is desirable to set it below 50 ppm to 100 ppm. Previously, the residual liquid containing oil in the distillation tank was removed after the number of cleaning cycles determined by an empirical formula. However, by measuring the oil concentration in the regenerated cleaning solution, it is desirable to be able to remove this residual liquid at a more appropriate timing.

[0005] To measure the oil concentration in a cleaning fluid, a method described in, for example, Patent Document 1 is considered. Patent Document 1 describes a technique that uses ultraviolet light of a predetermined wavelength, determined according to the composition of each oil component in the cleaning fluid, to measure absorbance, and then calculates the concentration of the oil dissolved in the cleaning fluid based on a pre-prepared calibration curve of oil concentration versus absorbance for each oil component. For example, the measurement wavelength for each oil component is set to 259 nm for commercially available pressure oil, 234 nm for commercially available cutting oil, and 250 nm for commercially available flux.

[0006] Patent Document 1: Japanese Patent Application Publication No. 09-061349 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] In the oil concentration measuring apparatus and method described in Patent Document 1, since the measurement wavelength for each type of oil is different, it is necessary to detect multiple wavelengths of light corresponding to these measurement wavelengths. Therefore, for example, a light source is used to illuminate the sample (hydrocarbon cleaning solution) with light containing these multiple wavelengths, a spectrometer is used to spectrate the light passing through the sample according to each wavelength, and a detector is used to detect the light obtained by the spectrometer according to each wavelength. In this structure, a spectrometer, which is an expensive optical element, is required, and an expensive detector with multiple detection elements set according to each wavelength is also required. Furthermore, since data is acquired almost simultaneously for each wavelength, an expensive control device is needed to process and store large amounts of data in a short time.

[0009] The problem to be solved by the present invention is to provide a device and method for measuring the oil concentration in a cleaning solution without the need for expensive spectroscopic elements, detection elements and control equipment.

[0010] Solution for solving the problem

[0011] The oil concentration measuring device in the cleaning fluid according to the present invention, which was made to solve the above-mentioned problems, includes:

[0012] a) An irradiation unit that irradiates the liquid to be measured with irradiation light having a measurement wavelength, wherein the measurement wavelength is a specified wavelength between 280 nm and 300 nm;

[0013] b) A transmitted light detection unit that measures the intensity of the transmitted light obtained by the irradiating light passing through the liquid to be measured; and

[0014] c) An oil concentration determination unit calculates the absorbance of the target liquid at the measurement wavelength based on the intensity of transmitted light measured by the transmitted light detection unit, and determines the oil concentration in the target liquid based on the absorbance value and a calibration curve representing the relationship between the oil concentration and absorbance at the measurement wavelength.

[0015] As mentioned earlier, many cleaning fluids, such as hydrocarbon cleaning fluids and glycol ether-based cleaning fluids, which are currently the mainstream cleaning fluids used in industrial cleaning machines, are composed of molecules with multiple (double, triple) bonds that do not contain carbon atoms. These molecules with multiple bonds do not contain carbon atoms absorb light at wavelengths below 280 nm, but hardly absorb light at wavelengths above 280 nm. In contrast, most oils adhering to the workpiece being cleaned, such as cutting oil, pressurized / stamping oil, machine oil, grease, and flux mixed into the cleaning fluid, contain molecules with multiple bonds containing carbon atoms. Depending on their type, these molecules with multiple bonds have a wide range of wavelengths where absorbance peaks, but regardless of the type of oil, the absorbance in the 280 nm to 300 nm wavelength range is not zero and has a fixed value. Furthermore, when the wavelength exceeds 300 nm, it is difficult to detect low concentrations of oils around 50 ppm.

[0016] Therefore, in this invention, the intensity of transmitted light is measured at a measurement wavelength defined as between 280 nm and 300 nm, and the absorbance at that measurement wavelength is calculated based on the intensity. This suppresses the influence of the measured liquid (cleaning solution, cleaning solution of the measured object) on the absorbance, and the concentration of the oil is determined based on a calibration curve representing the relationship between the oil content of the measured object and the absorbance at that measurement wavelength.

[0017] According to the oil concentration measuring device of the present invention, only a single wavelength is used as the measuring wavelength, thus eliminating the need for a spectroscopic element and a detection element for each wavelength. Furthermore, the amount of data to be processed simultaneously is less compared to using multiple wavelengths, thus eliminating the need for expensive control equipment. For example, instead of a dedicated control device for the oil concentration measuring device of the present invention, the control device (programmable logic controller) found in industrial cleaning machines can be used to control the oil concentration measuring device. For these reasons, the oil concentration measuring device of the present invention can reduce costs.

[0018] The oil concentration measuring device according to the present invention is preferably used for measuring oil concentrations of 50 ppm to 2000 ppm. Furthermore, because it is suitable for measuring such low concentrations, the oil concentration measuring device according to the present invention is preferably used for measuring the oil concentration in the post-regeneration cleaning fluid used in steam cleaning / drying where the ability to detect oil concentrations as low as 50 ppm is required. Moreover, the oil concentration measuring device according to the present invention is not limited to measuring the post-regeneration cleaning fluid; for example, it can also be used to determine the timing of the end of cleaning (setting the end time as when the time change of oil concentration falls below a predetermined value) by measuring the change in oil concentration in the cleaning tank during workpiece cleaning.

[0019] The oil concentration measuring device involved in this invention may also further include:

[0020] The second light irradiation unit irradiates the liquid to be measured with a second irradiation light having a second measurement wavelength, which is a specified wavelength between 320 nm and 340 nm.

[0021] The second transmitted light detection unit measures the intensity of the second transmitted light obtained by the second irradiation light passing through the liquid to be measured; and

[0022] The second oil concentration determination unit calculates the absorbance of the target liquid at the second measurement wavelength based on the intensity of the second transmitted light measured by the second transmitted light detection unit, and determines the oil concentration in the target liquid based on the absorbance value and a calibration curve representing the relationship between the oil concentration at the second measurement wavelength and the absorbance.

[0023] In this way, in addition to using illumination light with a predetermined wavelength between 280 nm and 300 nm for measurement, a second illumination light with a predetermined wavelength between 320 nm and 340 nm is used to determine the concentration of oil in the target liquid (cleaning solution, target cleaning solution), thereby improving the accuracy of measuring the absorbance of oils with a larger wavelength at which the absorbance peaks. In this case, it is not necessary to use different wavelengths of light for each type of oil; only the aforementioned measurement wavelength and the second measurement wavelength are needed. Furthermore, it is not necessary to use a spectrophotometer or to set up multiple transmission light detection elements (transmission light detection unit and second transmission light detection unit). Moreover, if the illumination light and the second illumination light are irradiated onto the target liquid at different times, the detector for detecting the transmission light does not need to identify the wavelength; therefore, a single detector that is compatible with both wavelengths can be used. For such a detector, a photodiode is preferable.

[0024] In the method for measuring oil concentration in the cleaning fluid involved in this invention,

[0025] Irradiation light of a specified wavelength, between 280 nm and 300 nm, is irradiated onto the liquid being measured.

[0026] The intensity of the transmitted light obtained by the irradiated light passing through the liquid being measured is determined.

[0027] The absorbance of the measured liquid at the measured wavelength is calculated based on the intensity of the transmitted light. The concentration of oil in the measured liquid is then determined based on the absorbance value and a calibration curve representing the relationship between the oil concentration at the measured wavelength and the absorbance.

[0028] The effects of the invention

[0029] According to the present invention, an inexpensive device and method for measuring oil concentration in cleaning fluid can be obtained without the need for expensive spectroscopic elements, detection elements, and control equipment. Attached Figure Description

[0030] Figure 1 This is a schematic structural diagram of an industrial cleaning machine having an embodiment of the oil concentration measuring device involved in this invention as a structural element.

[0031] Figure 2 This is a graph showing the measured values ​​of transmitted light in four cleaning solutions composed of molecules with multiple bonds that do not have carbon atoms.

[0032] Figure 3 This is a functional block diagram illustrating the functions of the control unit in the oil concentration measuring device of this embodiment.

[0033] Figure 4 This is a graph showing the results obtained by measuring the transmitted light intensity of cleaning solutions containing one of four different oils.

[0034] Figure 5 It means from Figure 4 The graph shows the results obtained by calculating absorbance from transmitted light.

[0035] Figure 6 It means according to Figure 5 The graph shows the calibration curves for each oil component produced using the absorbance values ​​shown.

[0036] Figure 7 This is a graph showing the results obtained by measuring the oil concentration in the cleaning fluid using the oil concentration measuring device and method of this embodiment. Detailed Implementation

[0037] use Figures 1-7 The following describes the implementation of the oil concentration measuring device and method involved in the present invention.

[0038] Figure 1 The outline structure of an industrial cleaning machine 1, which includes the oil concentration measuring device 10 of this embodiment as a structural element, is shown. The industrial cleaning machine 1 is a device for removing oil adhering to workpieces. In addition to the oil concentration measuring device 10, it also includes a first cleaning tank 11, a second cleaning tank 12, a steam cleaning / drying tank 13, a temporary storage tank 14, a distillation tank 15, a heat exchanger 16, a discharge device 17, a regenerated cleaning solution storage tank 18, and a sample cleaning solution tank 19. Figure 1 The thick solid lines in the diagram represent the flow path of liquids, the thick dashed lines represent the flow path of gases, and the thin, straight dashed lines represent the path of electrical signals.

[0039] (1) Overall structure and operation of industrial cleaning machine 1

[0040] Before describing the oil concentration measuring device 10 of this embodiment, the overall structure of the industrial cleaning machine 1 and the cleaning operation of the workpiece will be explained first. Ultrasonic transducers are provided in the first cleaning tank 11 and the second cleaning tank 12 to apply ultrasonic vibrations to the cleaning fluid stored in the tanks. Furthermore, to facilitate the generation of ultrasonic cavitation, a vacuum pump is used to depressurize the first cleaning tank 11 and the second cleaning tank 12, thereby degassing the cleaning fluid. After the cleaning fluid is stored in these first cleaning tanks 11 and the second cleaning tank 12, the workpiece is immersed in the cleaning fluid and ultrasonic vibrations are applied, thereby cleaning the workpiece. Here, for reasons explained later, the cleaning fluid in the second cleaning tank 12 contains less oil than the cleaning fluid in the first cleaning tank 11. Therefore, by first cleaning the workpiece in the first cleaning tank 11 and then cleaning the workpiece in the second cleaning tank 12, the re-adhesion of oil from the cleaning fluid onto the workpiece can be minimized.

[0041] The steam cleaning / drying tank 13 is used for steam cleaning and drying of workpieces that have been cleaned in the second cleaning tank 12. The steam used in the steam cleaning / drying is supplied from the distillation tank 15 as described later. The steam in the steam cleaning / drying tank 13, as well as the cleaning liquid from which substances remaining on the surface of the workpiece have been removed, is returned to the second cleaning tank 12. In addition, the gas generated by the depressurization of the first cleaning tank 11 and the second cleaning tank 12 and the evaporation of the cleaning liquid is recovered to the temporary storage tank 14.

[0042] A float valve 151 is installed in the distillation tank 15. When the liquid in the distillation tank 15 is reduced to below a specified level through distillation, the cleaning solution is introduced into the distillation tank 15 from the temporary storage tank 14. Inside the distillation tank 15, the liquid is heated by a heater (not shown) and depressurized by a drain 17. Thus, the oil residue in the cleaning solution is evaporated in liquid form. A portion of the generated steam is supplied to the steam cleaning / drying tank 13 as described above, and the remainder is condensed by the heat exchanger 16 and stored in the regenerated cleaning solution storage tank 18.

[0043] The regenerated cleaning fluid, having undergone oil removal via distillation tank 15, flows from the regenerated cleaning fluid storage tank 18 into the second cleaning tank 12. The first cleaning tank 11 and the second cleaning tank 12 are connected by a second overflow pipe 122. The second overflow pipe 122 is positioned higher than its connection point with the first cleaning tank 11. When the regenerated cleaning fluid flows into the second cleaning tank 12, raising the level of the cleaning fluid in the second cleaning tank 12 above this connection point, a portion of the cleaning fluid in the second cleaning tank 12 naturally moves to the first cleaning tank 11. Therefore, the cleaning fluid in the second cleaning tank 12 contains less oil than the cleaning fluid in the first cleaning tank 11. Furthermore, the first cleaning tank 11 and the temporary storage tank 14 are connected by a first overflow pipe 112. When the cleaning fluid flows into the second cleaning tank 12, raising the level of the cleaning fluid in the first cleaning tank 11 above the connection point of the first overflow pipe 112, a portion of the cleaning fluid in the first cleaning tank 11 naturally moves to the temporary storage tank 14 via the first overflow pipe 112.

[0044] The first cleaning tank 11 has a first circulating filtration system 111, which takes out cleaning fluid from the tank and returns it to the tank through a filter. The second cleaning tank 12 is also equipped with the same second circulating filtration system 121. These circulating filtration systems remove particles with a diameter of about 10 μm or larger, but cannot remove oil.

[0045] (2) Structure of the oil concentration measuring device 10 in this embodiment

[0046] Next, the structure of the oil concentration measuring device 10 in the industrial cleaning machine 1 will be described in detail. As will be described later, the oil concentration measuring device 10 includes a flow path 101 connected to the first cleaning tank 11, the second cleaning tank 12, and the regenerated cleaning liquid storage tank 18; an inlet pump 102 provided in the flow path 101; a sample cell 103 provided downstream of the inlet pump 102 in the flow path 101; a reference cell 1031 for reference measurement; a light irradiation unit 104; a transmitted light detection unit 105; and a control unit 106 for controlling the entire device and performing data processing as described later.

[0047] The inflow section 1011 of flow path 101 is connected to the first cleaning tank 11 via the first relay pipe 113, to the second cleaning tank 12 via the second relay pipe 123, and to the regenerated cleaning fluid storage tank 18 via the third relay pipe 183. Furthermore, a first relay on / off valve 11V is provided in the first relay pipe 113, a second relay on / off valve 12V is provided in the second relay pipe 123, and a third relay on / off valve 18V is provided in the third relay pipe 183.

[0048] The outflow portion of flow path 101 is connected to temporary storage tank 14. Therefore, the cleaning solution used for measurement in oil concentration measuring device 10 is distilled by distillation tank 15 via temporary storage tank 14, and finally returned to second cleaning tank 12 in a state where oil has been removed. Alternatively, the cleaning solution used for measurement can be directly returned from the outflow portion to the tank containing the cleaning solution.

[0049] Both sample cell 103 and reference cell 1031 are quartz cells with low ultraviolet absorption. During normal measurements, flow path 101 is connected to sample cell 103, and during reference data measurements, flow path 101 is connected to reference cell 1031. Reference cell 1031 is filled with an oil-free cleaning solution, and reference data is measured after the oil concentration measurement is interrupted at predetermined time intervals under the control of control unit 106.

[0050] In this embodiment, the light irradiation unit 104 irradiates the cleaning solution (measurement liquid) in the sample cell 103 with a measurement wavelength specified between 280 nm and 300 nm, and is composed of an LED that emits light at that measurement wavelength. In this embodiment, the measurement wavelength is set to 290 nm.

[0051] Here, use Figure 2 This explains why the measurement wavelength was set to a wavelength between 280nm and 300nm. Figure 2 The transmitted light spectra of four cleaning solutions 1-4, composed of molecules without carbon atoms and multiple bonds, are shown. Cleaning solutions 1-3 are saturated aliphatic hydrocarbon-based cleaning solutions, while cleaning solution 4 is an ethylene glycol ether-based cleaning solution. Figure 2 The spectrum of incident light is shown together. For all four cleaning solutions, the amount of transmitted light is significantly less than the amount of incident light at wavelengths below 280 nm, indicating absorption of ultraviolet light by the cleaning solutions. Conversely, at wavelengths above 280 nm, the difference between transmitted and incident light becomes smaller, and absorption of ultraviolet light by the cleaning solutions is almost nonexistent. Therefore, if the measurement is performed at a wavelength of 280 nm, the influence of light absorption by the cleaning solutions can be suppressed, and the concentration of oil can be measured. On the other hand, when the measurement wavelength exceeds 300 nm, as described later... Figure 5 As shown, low concentration (in) Figure 5In the example shown, the absorbance is 100 ppm. Further, it's 50 ppm. The absorbance value of the oil becomes too low to be determined. Therefore, by setting a wavelength between 280 nm and 300 nm as the measurement wavelength, the influence of the cleaning solution's absorbance can be suppressed, and even at low concentrations of around 50 ppm, the oil concentration can be measured.

[0052] The transmitted light detection unit 105, which detects the intensity of transmitted light with the aforementioned measurement wavelength obtained through the cleaning liquid in the sample cell 103, is composed of a photodiode and a signal conversion unit. The photodiode detects the light with the aforementioned measurement wavelength and outputs its intensity as an analog signal. The signal conversion unit converts the analog signal output by the photodiode into a digital signal.

[0053] Control unit 106 has with Figure 3 The functions are shown in the functional block diagram. Regarding the control unit 106, a programmable logic controller or a personal computer can be used; either the control device present in an industrial cleaning machine can be directly applied, or the control device of the oil concentration measuring device 10 can be included. The control unit 106 includes an oil concentration determination unit 1061, a reference data recording unit 1062, a calibration curve recording unit 1063, a condition input unit 1064, and a measurement control unit 1065. The oil concentration determination unit 1061 is composed of an absorbance calculation unit 1061A, a calibration curve selection unit 1061B, and a calibration curve application unit 1061C. Details of the oil concentration determination unit 1061 will be described later along with the operation of the oil concentration measuring device 10 of this embodiment. The reference data recording unit 1062 records data (reference data) of the transmitted light quantity at the aforementioned measurement wavelength, which has been pre-measured for a cleaning agent that does not contain oil. In the calibration curve recording unit 1063, a calibration curve showing the relationship between the concentration of the oil and its absorbance at the measurement wavelength is recorded for each type of oil that can be used in the processing of the workpiece. This curve is based on data pre-measured from a sample with a known concentration of the oil used. Furthermore, when multiple processing oils from different manufacturers or of different models have similar compositions, calibration curves applicable to these multiple processing oils can also be used. The condition input unit 1064 is used by the measuring personnel to input the measurement conditions, which will be described later, using an input device such as a touchpad. The measurement control unit 1065 controls the start and end of light irradiation from the light source in the light irradiation unit 104, as well as the start and end of processing in each of the aforementioned units.

[0054] The sample cell cleaning solution tank 19 is a tank for storing cleaning solution (the same cleaning solution as that used for measuring oil concentration) for cleaning the sample cell 103.

[0055] (3) Operation of the oil concentration measuring device 10 in this embodiment

[0056] The operation of the oil concentration measuring device 10 in this embodiment will be explained. Here, we will mainly describe the case where the oil concentration of the post-regeneration cleaning fluid stored in the post-regeneration cleaning fluid storage tank 18 is set as the target for oil concentration measurement, and the oil concentration is close to that of the steam used in the steam cleaning / drying tank 13.

[0057] First, the measurement begins by the operator inputting the prescribed measurement conditions using the condition input unit 1064, followed by an instruction to start the measurement. The measurement conditions input here are information about the machining oil adhering to the workpiece, used to determine the type of cleaning fluid to be used to clean it (e.g., the manufacturer and model of the machining oil).

[0058] When the measurement begins, the relay valve corresponding to the cleaning tank or storage tank containing the cleaning solution for the test object is first opened. At this time, the third relay on / off valve 18V, which is connected to the third relay pipe 183 connected to the regenerated cleaning solution storage tank 18, is opened. Thus, the regenerated cleaning solution for the test object is introduced into the sample cell 103 through the flow path 101. Furthermore, if the cleaning solution for the test object is the cleaning solution in the first cleaning tank 11, the first relay on / off valve 11V is opened; if it is the cleaning solution in the second cleaning tank 12, the second relay on / off valve 12V is opened.

[0059] The light irradiation unit 104 irradiates the cleaning solution in the sample cell 103 with light of the measured wavelength (290 nm). The transmitted light detection unit 105 measures the intensity I of the transmitted light that passes through the cleaning solution and converts the intensity I into a digital signal for output.

[0060] Next, the control unit 106 receives a digital signal representing the intensity I of the transmitted light output from the transmitted light detection unit 105, and acquires reference data I0 from the reference data recording unit 1062. This reference data I0 represents the transmitted light intensity of the oil-free cleaning liquid at the aforementioned measurement wavelength. The absorbance calculation unit 1061A of the control unit 106 calculates the absorbance A of the cleaning liquid being measured based on the intensity I of the transmitted light of the cleaning liquid being measured and the reference data I0. 10 (I0 / I).

[0061] Next, the calibration curve selection unit 1061B of the control unit 106 obtains the calibration curve corresponding to the determined processing oil from the calibration curve recording unit 1063 based on the information used to determine the processing oil input by the condition input unit 1064. Furthermore, the calibration curve application unit 1061C applies the absorbance A of the cleaning fluid of the test object obtained by the absorbance calculation unit 1061A to the calibration curve selected by the calibration curve selection unit 1061B to calculate the concentration of the processing oil.

[0062] Subsequently, by continuously introducing the regenerated cleaning solution of the test object into the sample cell 103 and repeatedly measuring the intensity I of the transmitted light by the light irradiation unit 104, the concentration of the processing oil is repeatedly determined. Furthermore, when the concentration of the processing oil exceeds a predetermined value, the residual liquid remaining in the distillation tank 15 is treated. The residual liquid is treated by boiling the residual liquid to separate the cleaning solution and processing oil, thereby discarding the processing oil remaining in the distillation tank 15.

[0063] Furthermore, when the cleaning fluid for the test object is set to the cleaning fluid in the first cleaning tank 11 or the second cleaning tank 12, the concentration of the processing oil in the cleaning fluid can be repeatedly determined during the cleaning of the workpiece using the same method as described above. The measurement results can be used to determine the cleaning end time when the cleaning of the workpiece ends when the change in concentration over time becomes below a specified value.

[0064] (4) Examples of absorbance and calibration curves

[0065] Multiple samples were prepared by mixing four representative processing oils (Table 1) at different concentrations into the same cleaning solution. The absorbance was determined by measuring the transmitted light intensity for each oil and concentration. To verify the appropriateness of setting the measurement wavelength to 290 nm, the transmitted light intensity was measured in the range of 260 nm to 400 nm, instead of limiting the wavelength to 290 nm. The cleaning solution used was "NS100" (manufactured by JX Energy Co., Ltd.), a saturated aliphatic hydrocarbon system without carbon atoms. Figure 2 The cleaning solution 1). In addition, the concentrations of each oil component are set to 100ppm, 500ppm, 2000ppm and 10000ppm.

[0066] [Table 1]

[0067]

[0068] Figure 4 The amount of transmitted light obtained by measurement is shown for each type of oil contained in the cleaning solution. Additionally, Figure 5 According to Figure 4 The results shown are obtained by calculating absorbance from transmitted light. They are all in the wavelength range of 280nm to 300nm, and the absorbance varies depending on the oil concentration.

[0069] Based on the absorbance obtained in this way for each oil fraction and each concentration at a wavelength of 290 nm, a calibration curve representing the relationship between absorbance and concentration is prepared for each oil fraction. Figure 6The calibration curves produced are shown below. Furthermore, data at a concentration of 10,000 ppm for each oil fraction were not used because the calibration curves deviated from a linear path. Figure 6 As shown, the calibration curve can be represented as a straight line when the concentration is below 2000 ppm. Therefore, at concentrations of at least 2000 ppm, the oil concentration can be measured using the oil concentration measuring apparatus and method of this embodiment.

[0070] exist Figure 1 In the industrial cleaning machine shown, to maintain the quality of workpiece cleaning, it is important to measure / manage the oil concentration of the regenerated cleaning solution after distillation in the distillation tank 15. In particular, the regenerated cleaning solution is used for steam cleaning, where steam generated in the distillation tank 15 directly cleans the workpiece in the steam cleaning / drying tank 13. Therefore, it is crucial to measure / manage the oil concentration during continuous operation of the industrial cleaning machine. According to the present invention, it is possible to measure / manage the oil concentration during continuous operation of such an industrial cleaning machine.

[0071] An experiment was conducted to measure the oil concentration in the regenerated cleaning fluid using the obtained calibration curve. In this experiment, the cleaning fluid used was also either NS100 or NS200 (manufactured by JX Energy Co., Ltd.). Figure 2 The cleaning fluid 2) was used with five types of cutting oil and five types of pressurizing / stamping oil containing the additives shown in Table 1 above. In this experiment, a sample with a known concentration (referred to as the "original concentration") was prepared by weighing the cleaning fluid and the oil and then mixing them, and the original concentration was compared with the measured value.

[0072] Figure 7 The experimental results are shown in the graph. In this graph, the original concentration is set on the horizontal axis and the measured value is set on the vertical axis. If the measured value converges within ±10% of the original concentration, the data point converges between the two dashed lines in the graph. Additionally, in Figure 7 The data from all samples are plotted in a graph. As shown in the graph, all the measured values ​​obtained in this study converge to approximately ±10% of the original concentration. An accuracy of around ±10% is sufficient for use in industrial cleaning machines.

[0073] (5) Variations

[0074] In the oil concentration measuring device 10 of this embodiment, the light irradiation unit 104 may irradiate the cleaning liquid with light of a measurement wavelength between 280nm and 300nm (290nm in the above example), and also irradiate the cleaning liquid with a second measurement wavelength of a predetermined wavelength between 320nm and 340nm. It is desirable that these two different wavelengths of light are generated using two light sources that emit monochromatic light with different wavelengths. In this case, if the intensity of both the light of the above measurement wavelength and the light of the second measurement wavelength can be measured, then only one transmission light detection unit 105 is needed as a detector that can universally detect both wavelengths of light. Alternatively, a different transmission light detection unit may be used for each wavelength. At this second measurement wavelength, similar to the case of the above measurement wavelength (290nm), it is possible to... Figure 5 The absorbance data were used to create calibration curves for each oil fraction, showing the relationship between absorbance and concentration.

[0075] For example, Figure 6 Compared with the calibration curves in (a) to (c), the calibration curve shown in (d) has a slightly larger difference between the point where the absorbance is obtained and the calibration curve. Therefore, the accuracy can be improved by determining the oil concentration using two separate measurement wavelengths.

[0076] Explanation of reference numerals in the attached figures

[0077] 1: Industrial cleaning machine; 10: Oil concentration measuring device; 101: Flow path; 1011: Inlet; 102: Liquid inlet pump; 103: Sample cell; 1031: Reference cell; 104: Light irradiation unit; 105: Transmitted light detection unit; 106: Control unit; 1061: Oil concentration determination unit; 1061A: Absorbance calculation unit; 1061B: Calibration curve selection unit; 1061C: Calibration curve application unit; 1062: Reference data recording unit; 1063: Calibration curve recording unit; 1064: Condition input unit; 1065: Measurement control unit; 11: First cleaning Washing tank; 111: First circulating filtration system; 112: First overflow pipe; 113: First relay pipe; 11V: First relay on / off valve; 12: Second cleaning tank; 121: Second circulating filtration system; 122: Second overflow pipe; 123: Second relay pipe; 12V: Second relay on / off valve; 13: Steam cleaning / drying tank; 14: Temporary storage tank; 15: Distillation tank; 151: Float valve; 16: Heat exchanger; 17: Discharge device; 18: Regenerated cleaning solution storage tank; 183: Third relay pipe; 18V: Third relay on / off valve; 19: Sample cell cleaning solution tank.

Claims

1. An oil concentration measuring device for measuring the concentration of a measurement target oil in a measurement target liquid obtained by mixing an oil, which is a measurement target oil, containing a molecule having a multiple bond with a carbon atom into a cleaning liquid composed of molecules not having a multiple bond with a carbon atom, the oil concentration measuring device characterized by comprising: a) a light irradiation section that irradiates only an irradiation light having a measurement wavelength, which is only one wavelength set in advance in a range of 280 nm to 300 nm, to the measurement target liquid; b) a transmitted light detection section that measures the intensity of a transmitted light obtained by the irradiation light transmitted through the measurement target liquid; c) a condition input section for inputting information of the measurement target oil, which is only one of different kinds of oils containing a multiple bond molecule; and d) an oil concentration determination section that calculates the absorbance at the measurement wavelength of the measurement target liquid from the intensity of the transmitted light measured by the transmitted light detection section, selects a calibration curve for the measurement target oil from the values of the absorbance and calibration curves respectively prepared for the different kinds of oils containing a multiple bond molecule, which show the relationship between the concentration of the oil and the absorbance at the measurement wavelength, and calculates the concentration of the measurement target oil in the measurement target liquid based on the calibration curve. Further comprising: a second light irradiation section that irradiates only a second irradiation light having a second measurement wavelength, which is only one wavelength set in advance in a range of 320 nm to 340 nm, to the measurement target liquid; a second transmitted light detection section that measures the intensity of a second transmitted light obtained by the second irradiation light transmitted through the measurement target liquid; and a second oil concentration determination section that calculates the absorbance at the second measurement wavelength of the measurement target liquid from the intensity of the second transmitted light measured by the second transmitted light detection section, and calculates the concentration of the measurement target oil in the measurement target liquid from the value of the absorbance and a calibration curve showing the relationship between the concentration of the oil and the absorbance at the second measurement wavelength.

3. An oil concentration measuring method for measuring the concentration of a measurement target oil in a measurement target liquid obtained by mixing an oil, which is a measurement target oil, containing a molecule having a multiple bond with a carbon atom into a cleaning liquid composed of molecules not having a multiple bond with a carbon atom, the oil concentration measuring method characterized by comprising the steps of: irradiating only an irradiation light having a measurement wavelength, which is only one wavelength set in advance in the range of 280 nm to 300 nm, to the measurement target liquid, measuring the intensity of a transmitted light obtained by the irradiation light transmitted through the measurement target liquid, inputting information of the measurement target oil, which is only one of different kinds of oils containing multiple bond molecules, and selecting a calibration curve for the measurement target oil from the values of the absorbance and calibration curves respectively made for the different kinds of oils containing a multiple bond molecule, which show the relationship between the concentration and the absorbance of the oil at the measurement wavelength, and calculating the concentration of the measurement target oil in the measurement target liquid based on the calibration curve. ​ ​ 2. The oil concentration measuring device in a cleaning liquid according to claim 1, characterized by ​ ​ ​ ​ ​ ​ ​ ​ ​ The absorbance of the target liquid at the measurement wavelength is calculated based on the intensity of the transmitted light. Based on the absorbance value and calibration curves showing the relationship between the concentration of the oil and the absorbance at the measurement wavelength for different oils containing multiple bond molecules, a calibration curve for the target oil is selected, and the concentration of the target oil in the target liquid is determined based on the calibration curve.

4. The method according to claim 3, wherein It also includes the following steps: The liquid to be measured is irradiated only with a second irradiation light having a second measurement wavelength, which is a pre-set wavelength between 320 nm and 340 nm. The intensity of the second transmitted light obtained by the second irradiation light passing through the liquid being measured is determined. The absorbance of the target liquid at the second measurement wavelength is calculated based on the intensity of the second transmitted light. The concentration of the target oil in the target liquid is determined based on the absorbance value and a calibration curve representing the relationship between the oil concentration at the second measurement wavelength and the absorbance.

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