JP2010210285A - Method and device for detecting concentration of mixed fluid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for detecting the concentration of a mixed fluid capable of accurately detecting the concentration of the mixed fluid constituted of three or more kinds of components, and a device for detecting the concentration of the mixed fluid. <P>SOLUTION: In the method for detecting the concentration of the mixed fluid constituted so as to detect the concentrations of the respective components of the mixed fluid constituted of N (an integer of ≥3) kinds of known components, the dielectric constant of the mixed fluid is measured at different temperatures of an (N-1) point and the concentrations of the respective components are calculated from the dielectric constants of the respective known components at the respective temperatures of the (N-1) point and the dielectric constants of the mixed fluid at the respective temperatures of the (N-1) point. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a mixed fluid concentration detection method and detection apparatus for detecting the concentration of a mixed fluid composed of three or more components.

  In recent years, alcohol has attracted attention as an alternative fuel to gasoline, and mixed fuels such as bio-mixed gasoline mainly composed of gasoline and ethanol and bio-mixed light oil mainly composed of light oil and fatty acid methyl ester have started to spread. ing. In order to be able to inject into the combustion chamber a fuel amount suitable for the operating state of the internal combustion engine using this kind of mixed fuel, it is necessary to detect the concentration of gasoline and alcohol as needed and constantly grasp the alcohol content. There is. Gasoline and alcohol concentration detection devices for this purpose are disclosed in, for example, Japanese Patent Application Laid-Open No. 5-87764 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2008-268169 (Patent Document 2).

  For example, the alcohol content detection device disclosed in Patent Document 1 introduces a mixed fuel (mixed fluid) composed of gasoline and alcohol to be measured between a pair of electrodes arranged in a casing, thereby statically mixing the mixed fuel. It is an apparatus that measures the concentration of alcohol by measuring the capacitance (dielectric constant). The liquid property sensor disclosed in Patent Document 2 includes a comb-like electrode provided on a semiconductor substrate immersed in a liquid fuel such as gasoline to measure capacitance (dielectric constant), and is included in gasoline. It is a sensor that detects the mixing ratio of alcohol.

JP-A-5-87764 JP 2008-268169 A

  Incidentally, in the above mixed fuel, it is known that, for example, water is mixed in addition to gasoline and ethanol which are the main components. Specifically, water is mixed into ethanol during the refining stage, water contained in the atmosphere dissolves into the mixed fuel when it comes into contact with the atmosphere, or water is artificially mixed when transporting the mixed fuel. It is known. When water is mixed in the mixed fuel in this way, the electrostatic capacity (dielectric constant) of the mixed fuel changes depending on the concentrations (existence ratios) of the three components of gasoline, ethanol and water. However, in the above-described prior art, the mixed fuel is considered to be composed of gasoline and alcohol, and only the concentration of two components can be measured.

  Therefore, an object of the present invention is to provide a mixed fluid concentration detection method and a detection device capable of accurately detecting the concentration of a mixed fluid composed of three or more components.

  The invention described in claim 1 is a mixed fluid concentration detection method for detecting the concentration of each component of a mixed fluid composed of N (> 3 integer) types of known components, wherein (N-1) The dielectric constant of the mixed fluid is measured at different temperatures, and the dielectric constant of each known component at each temperature at the (N-1) point and the temperature measured at each temperature at the (N-1) point. The concentration of each component is calculated from the dielectric constant of the mixed fluid.

In the mixed fluid concentration detection method, the concentration of each component of the mixed fluid composed of N (> 3 integers) known components is detected by utilizing the different dielectric constants and temperature characteristics. Is. If the concentration (abundance ratio) of each component is a ₁ , a ₂ ,..., A _N , one equation a ₁ + a ₂ +... + A _N = 1 holds. In the above mixed fluid concentration detection method, the dielectric constants of the mixed fluid are measured at different temperatures at (N-1) points, and the dielectric constants ε ₁ and ε _{2 of} (N-1) mixed fluids. ,..., Ε _N-1 is obtained. The measured dielectric constants ε ₁ , ε ₂ ,..., Ε _N-1 are obtained by multiplying the product of the dielectric constant and the concentration of each single component at the same temperature that has been previously grasped. Equal to the sum of Therefore, from this, (N-1) equations are established. Thus, according to the concentration detection method of the mixed fluid, simultaneous equations concentration a _1, a _2, · · ·, for N unknowns a _N, of N equations in total as described above , And by solving the simultaneous equations, the concentrations a ₁ , a ₂ ,..., A _N can be accurately determined.

  As described above, the mixed fluid concentration detection method is a mixed fluid concentration detection method for detecting the concentration of each component of a mixed fluid composed of N (≧ 3) kinds of known components. It can be set as the mixed fluid density | concentration detection method which can detect correctly the density | concentration of the mixed fluid comprised by 3 or more types of components.

In the mixed fluid concentration detection method, as described in claim 2, for example, when N is 3, the concentrations of the components are a, b, and c, respectively, and the two different temperatures are used. Are T ₁ and T ₂ , the dielectric constants of the respective components at the temperature T ₁ are respectively ε _a1 , ε _b1 and ε _c1, and the dielectric constants of the respective components at the temperature T ₂ are respectively ε _a2 , ε _b2 and ε and _c2, the temperatures _{T 1} and respectively epsilon ₁ of the dielectric constant of the mixed fluid at a temperature _{T 2,} when the epsilon _2,
(Formula 1) a + b + c = 1
(Equation 2) ε ₁ = ε _a1 · a + ε _b1 · b + ε _c1 · c
(Equation 3) ε ₂ = ε _a2 · a + ε _b2 · b + ε _c2 · c
From the above, the concentration of each component can be calculated.

  The concentration detection method of the mixed fluid can be applied to the detection of the concentration of the mixed fuel of the internal combustion engine in which water may be mixed. For example, as described in claim 3, the component includes ethanol, gasoline, and the like. And water. In addition, although gasoline is comprised by several hundred types of components, the dielectric constant of all the components is substantially the same, and it is possible to handle gasoline as one type of component. Moreover, the fatty acid methyl ester, light oil, and water may be sufficient as the said component as described in Claim 4.

  In the method for detecting the concentration of the mixed fluid, as described in claim 5, in measuring the dielectric constant at each temperature of the mixed fluid, two capacitance detection elements connected in series with a carrier wave having a reverse voltage of a predetermined voltage. The output from the connection point of the two capacitance detection elements is input to a C / V converter to which a feedback capacitance is added, and the dielectric fluid at each temperature of the mixed fluid is output from the output voltage of the C / V converter. It is preferable to measure the rate.

  According to this, since the influence of the parasitic capacitance due to the wiring can be canceled, the dielectric constant can be measured with higher accuracy than when one capacitance detection element is used, and the concentration of each component can be detected with higher accuracy. can do.

  The invention described in claims 6 to 17 is an invention relating to a mixed fluid concentration detection device for carrying out the mixed fluid concentration detection method described above.

  The invention according to claim 6 is a mixed fluid concentration detection device for detecting the concentration of each component of a mixed fluid composed of N (integer of 3) known components, the temperature of the mixed fluid A temperature measuring unit capable of measuring at a different (N-1) point, a dielectric constant measuring unit capable of measuring a dielectric constant of the mixed fluid at a different temperature at the (N-1) point, and the memory stored in a memory The concentration of each component is calculated from the dielectric constant of each known component at each temperature at point (N-1) and the dielectric constant of the mixed fluid measured at different temperatures at point (N-1). And a density calculation unit.

  Thus, the mixed fluid concentration detection method according to claim 1 can be implemented.

  In the mixed fluid concentration detection device, as described in claim 7, the concentration detection device has a heater unit for forming different temperatures of the (N-1) points of the mixed fluid. It is preferable to become.

  When measuring the dielectric constant of the fluid mixture at different temperatures at (N-1) points, it is also possible to wait for the temperature of the fluid mixture to change over time. However, with the configuration having the heater section, the temperature of the mixed fluid can be appropriately changed to a different (N-1) point temperature. Therefore, according to this, it is possible to appropriately detect the concentration of each component of the mixed fluid.

  In the mixed fluid concentration detection device, as described in claim 8, a temperature detection element that is a component of the temperature measurement unit and a capacitance detection element that is a component of the dielectric constant measurement unit are included in one chip. It is preferable to be formed. According to this, compared with the case where a temperature detection element and a capacity | capacitance detection element are each incorporated as a separate component in piping which flows mixed fluid, for example, size reduction and a cost reduction can be achieved.

  Furthermore, when it is set as the structure which has the above-mentioned heater part, as described in Claim 9, the temperature detection element which is a component of the said temperature measurement part, The capacity | capacitance detection element which is a component of the said dielectric constant measurement part And it is preferable for the heater element which is a component of the said heater part to be formed in one chip | tip for size reduction and a cost reduction.

  In this case, as described in claim 10, in the chip, a groove portion may be formed so as to thermally separate the heater element, the temperature detection element, and the capacitance detection element. preferable. According to this, since heat conduction from the heater element to the temperature detection element and the capacitance detection element through the chip can be suppressed, the temperature and dielectric constant of the mixed fluid can be more accurately compared to the case where the groove is not formed. The concentration of each component can be detected more accurately.

  When the capacitance detection element is formed on the chip, as described in claim 11, it is preferable that the capacitance detection element includes a pair of comb-like electrodes. According to this, the mixed fluid can be easily guided between the pair of comb-like electrodes formed on the chip, and the detection capacitance value is increased by increasing the comb-tooth density, thereby improving the dielectric constant measurement accuracy. Can be increased.

  Further, in the case of the configuration having the heater section described above, as described in claim 12, a heater element that is a component of the heater section disposed on the upstream side of the mixed fluid, and the mixed fluid A configuration in which stirring means for the mixed fluid is provided between a temperature detection element that is a component of the temperature measurement unit and a capacitance detection element that is a component of the dielectric constant measurement unit disposed on the downstream side; It is preferable to do.

  According to this, for example, by using the stirring means such as fins, meshes, filters, etc., temperature unevenness of the mixed fluid due to heating using the heater element can be eliminated, and the temperature and dielectric constant of the mixed fluid can be measured more accurately. it can. Therefore, the concentration of each component of the mixed fluid can be detected more accurately. In particular, in the case of a capacitance detection element having a large electrode size, since the volume of the fluid mixture between the electrodes is large, it is necessary to make the temperature of the fluid mixture between the electrodes uniform using the stirring means.

  In the mixed fluid concentration detection device, as described in claim 13, the capacitance detection element as a component of the dielectric constant measurement unit includes a pair of electrodes, and one of the electrodes is the temperature measurement unit. It can also be set as the structure which serves also as the temperature detection element which is a component of these. According to this, further downsizing and cost reduction are possible.

  In the mixed fluid concentration detection device, as described in claim 14, the dielectric constant measurement unit includes two capacitance detection elements connected in series and a C / V converter to which a feedback capacitance is added. In the measurement of the dielectric constant at each temperature of the mixed fluid, the two capacitance detection elements are driven by a carrier wave having a predetermined voltage, and an output from a connection point of the two capacitance detection elements is obtained. It is preferable to input to the C / V converter and measure the dielectric constant at each temperature of the mixed fluid from the output voltage of the C / V converter.

  According to the dielectric constant measurement unit, as described above, since the influence of the parasitic capacitance due to the wiring can be canceled, the dielectric constant can be measured with higher accuracy than when one capacitance detection element is used. The concentration of the component can also be detected with higher accuracy.

In the mixed fluid concentration detection apparatus, as described in claim 14, for example, when N is 3, the concentration calculation unit sets the concentration of each component to a, b, and c, respectively. The two different temperatures are T ₁ and T ₂ , the dielectric constants of the components at the temperature T ₁ are ε _a1 , ε _b1 , and ε _c1 , respectively, and the dielectric constants of the components at the temperature T ₂ are ε _a2 , ε _b2 , and ε _c2, and the dielectric constants of the mixed fluid at the temperature T ₁ and the temperature T ₂ are ε ₁ and ε ₂ , respectively.
(Formula 1) a + b + c = 1
(Equation 2) ε ₁ = ε _a1 · a + ε _b1 · b + ε _c1 · c
(Equation 3) ε ₂ = ε _a2 · a + ε _b2 · b + ε _c2 · c
From the above, the concentration of each component is calculated.

  The mixed fluid concentration detection device is suitable for detecting the concentration of a mixed fuel of an internal combustion engine in which water may be mixed as described above. For example, as described in claim 16, the component includes ethanol, It is suitable when it is gasoline and water, or when the components are fatty acid methyl ester, light oil and water as described in claim 17.

  As described above, the mixed fluid concentration detection method and the detection apparatus detect the concentration of each component of the mixed fluid composed of N (> 3 integer) types of known components. And it is a detection apparatus, It is the density | concentration detection method and detection apparatus of the mixed fluid which can detect correctly the density | concentration of the mixed fluid comprised by 3 or more types of components.

It is the figure which showed the temperature characteristic of the dielectric constant about each component of ethanol, gasoline, and water. It is the figure which showed an example of the density | concentration detection apparatus of mixed fluid. (A) is the figure which showed schematic structure of the density | concentration detection apparatus 100, (b) is an example of a structure of the sensor part in the density | concentration detection apparatus 100 of (a), and showed the sensor chip 50 typically. It is a top view. Further, (c) is a top view schematically showing a capacitance detection element 21a, which is an example of the capacitance detection element 21 of (b). FIG. 2A is another configuration example of the sensor unit in the concentration detection apparatus 100 of FIG. 2A, and FIG. 2A is a top view schematically showing the sensor chip 51. Further, (b) is a diagram showing the temperature distribution of the sensor chip 51 along the flow direction of the mixed fluid, and (c) schematically shows a cross section of the sensor chip 51 along the flow direction of the mixed fluid. FIG. It is the top view which showed another sensor chip 52 typically. FIG. 3 is a diagram showing a preferred configuration example of a dielectric constant measurement unit 20 in the concentration detection apparatus 100 of FIG. 2A, and is a circuit block diagram showing a configuration of each part of the dielectric constant measurement unit 24. FIG. 6 is a diagram illustrating a configuration example of two capacitance detection elements Cs1 and Cs2 illustrated in FIG. 5, and is a top view schematically illustrating a capacitance detection element 24b. (A), (b) is another example of a structure of the sensor part in the density | concentration detection apparatus 100 of Fig.2 (a), and is sectional drawing which each showed the sensor components 61 and 62 typically. It is a figure which shows a structural example suitable when using a capacitance detection element with a large electrode dimension like the sensor components 61 and 62 shown to Fig.7 (a), (b).

  The present invention relates to a mixed fluid concentration detection method and detection apparatus for detecting the concentration of a mixed fluid composed of three or more components.

  A concentration detection method for a mixed fluid according to the present invention is a mixed fluid concentration detection method for detecting the concentration of each component of a mixed fluid composed of N (> 3 integer) known components. -1) Measure the dielectric constant of the fluid mixture at different temperatures at the points, and measure the dielectric constant of each known component at each temperature at the (N-1) point and each temperature at the (N-1) point. The concentration of each component is calculated from the dielectric constant of the mixed fluid.

In the mixed fluid concentration detection method, the concentration of each component of the mixed fluid composed of N (> 3 integers) known components is detected by utilizing the different dielectric constants and temperature characteristics. Is. If the concentration (abundance ratio) of each component is a ₁ , a ₂ ,..., A _N , one equation a ₁ + a ₂ +... + A _N = 1 holds. In the above mixed fluid concentration detection method, the dielectric constants of the mixed fluid are measured at different temperatures at (N-1) points, and the dielectric constants ε ₁ and ε _{2 of} (N-1) mixed fluids. ,..., Ε _N-1 is obtained. The measured dielectric constants ε ₁ , ε ₂ ,..., Ε _N-1 are obtained by multiplying the product of the dielectric constant and the concentration of each single component at the same temperature that has been previously grasped. Equal to the sum of Therefore, from this, (N-1) equations are established. Thus, according to the concentration detection method of the mixed fluid, simultaneous equations concentration a _1, a _2, · · ·, for N unknowns a _N, of N equations in total as described above , And by solving the simultaneous equations, the concentrations a ₁ , a ₂ ,..., A _N can be accurately determined.

  As described above, the mixed fluid concentration detection method is a mixed fluid concentration detection method for detecting the concentration of each component of a mixed fluid composed of N (≧ 3) kinds of known components. It is a mixed fluid concentration detection method capable of accurately detecting the concentration of a mixed fluid composed of three or more components.

  For example, in the mixed fluid concentration detection method, a case is assumed where N is 3, that is, there are three types of components A, B, and C. For example, this is a case where component C is mixed as an impurity in a mixed fluid mainly composed of two types of components A and B. Components A, B, and C do not cause a chemical reaction or the like and are mixed uniformly.

  In the mixed fluid concentration detection method, the concentration of each component is detected by the following procedure. When there are three types of components A, B, and C, two different temperatures are set, and the dielectric constant of each single component A, B, and C at each temperature is grasped in advance. Next, the dielectric constant of the mixed fluid at each temperature is measured.

Here, the concentrations of the components A, B, and C are a, b, and c, the two different temperatures are T ₁ and T ₂ , respectively, and the single components A, B, and T at the temperature T ₁ are the same. The dielectric constants of C are ε _a1 , ε _b1 , and ε _c1 , respectively, and the dielectric constants of the single components A, B, and C at temperature T ₂ are ε _a2 , ε _b2 , and ε _c2 , respectively, and temperatures T ₁ , When the dielectric constants of the mixed fluid at T ₂ are ε ₁ and ε ₂ , respectively.
(Formula 1) a + b + c = 1
(Equation 2) ε ₁ = ε _a1 · a + ε _b1 · b + ε _c1 · c
(Equation 3) ε ₂ = ε _a2 · a + ε _b2 · b + ε _c2 · c
Is established. By solving the simultaneous equations of Formulas 1 to 3, the concentrations a, b, and c of the components A, B, and C can be calculated.

  The mixed fluid concentration detection method is suitable for detecting the concentration of mixed fuel in an internal combustion engine in which water may be mixed. For example, in the case of bio-mixed gasoline mainly composed of gasoline and ethanol, the components are ethanol, gasoline and water. In addition, although gasoline is comprised by several hundred types of components, the dielectric constant of all the components is substantially the same, and it is possible to handle gasoline as one type of component. In the case of bio-mixed light oil mainly composed of light oil and fatty acid methyl ester, the components are fatty acid methyl ester, light oil and water.

  Next, the concentration detection method for the mixed fluid will be specifically described with reference to the drawings.

  FIG. 1 is a graph showing temperature characteristics of relative permittivity for each component of ethanol, gasoline, and water.

When the main components (gasoline, ethanol) and mixed impurities (water) are known components as in bio-mixed gasoline, as shown in FIG. 1, the temperature dependence of the dielectric constant of each component is grasped in advance. deep. Thereby, ethanol, each component of the gasoline and water, for example, the dielectric constant epsilon _a1 at temperatures _{T 1} shown in FIG, epsilon _b1, and epsilon _c1, the dielectric constant epsilon _a2 at temperatures _{T 2,} epsilon _b2, the epsilon _c2 Know in advance. Note that the temperatures T ₁ and T ₂ set for measuring the dielectric constant of the mixed fluid do not necessarily coincide with the measured temperatures of the components shown in the data of FIG. Data at each measurement point in FIG. 1 may be stored in a memory described later, and linear interpolation may be performed for arbitrary set temperatures T ₁ and T ₂ to be used for the calculations of Equations 1 to 3.

  FIG. 2 is a view showing an example of a mixed fluid concentration detection device for carrying out the above-described mixed fluid concentration detection method. FIG. 2A is a diagram showing a schematic configuration of the concentration detection apparatus 100, and FIG. 2B is an example of a configuration of a sensor unit in the concentration detection apparatus 100 of FIG. It is the top view which showed typically. FIG. 2C is a top view schematically showing a capacitance detection element 21a, which is an example of the capacitance detection element 21 in FIG.

  A concentration detection apparatus 100 shown in FIG. 2A is a mixed fluid concentration detection apparatus that detects the concentration of each component of a mixed fluid including N (> 3 integer) types of known components. The concentration detection apparatus 100 includes a temperature measuring unit 10 that can measure the temperature of the mixed fluid at different (N-1) points, and a dielectric constant that can measure the dielectric constant of the mixed fluid at different temperatures of the (N-1) points. A fluid mixture measured at a temperature different from the (N-1) point and the dielectric constant of each known component at each temperature at the (N-1) point stored in the measurement unit 20 and a memory (not shown). And a concentration calculation unit 30 for calculating the concentration of each component from the dielectric constant of each.

  Moreover, the concentration detection apparatus 100 shown to Fig.2 (a) has the heater part 40 for forming the temperature from which the said (N-1) point of mixed fluid differs. When measuring the dielectric constant of the fluid mixture at different temperatures at (N-1) points, it is also possible to wait for the temperature of the fluid mixture to change over time. However, by adopting a configuration having a heater portion like the concentration detection device 100, the temperature of the mixed fluid can be appropriately changed to a different (N-1) point temperature in a short time. Therefore, the concentration detection apparatus 100 can appropriately detect the concentration of each component of the mixed fluid.

  Note that the concentration detection apparatus 100 in FIG. 2 (a) has a heater unit 40 and obtains a different (N-1) point temperature by heating, but conversely, by cooling it. You may make it obtain the temperature of a different (N-1) point. Heating and cooling can be performed directly or indirectly as long as the measurement target does not change irreversibly. In this case, as a heating means, a resistor heater heating, induction heating, electromagnetic wave heating, radiation heating, a Peltier element, an expansion valve or the like can be used. For cooling, refrigerant cooling, forced convection cooling, a Peltier element, a compression valve, or the like can be used.

  A sensor chip 50 shown in FIG. 2B is made of a semiconductor substrate, and a temperature detection element 11 that is a component of the temperature measurement unit 10 shown in FIG. 2A and a capacitance that is a component of the dielectric constant measurement unit 20. The detection element 21 and the heater element 41 which is a component of the heater unit 40 are formed. The sensor chip 50 is immersed in a mixed fluid, and the dielectric constant of the mixed fluid is measured at different temperatures at (N-1) points. Like the sensor chip 50, the temperature detection element 11, the capacitance detection element 21, and the heater element 41 are formed in one chip, so that, for example, the temperature detection element and the capacitance detection element are separately provided in a pipe through which a mixed fluid, which will be described later, flows. As compared with the case of incorporating as, it is possible to reduce the size and cost. In the case of the sensor chip 50 made of a semiconductor substrate, wiring on the order of micrometers can be formed, and the sensor chip 50 can be downsized to a size of several millimeters square.

  The sensor chip 50 shown in FIG. 2B is made of a semiconductor substrate, but is not limited to this. For example, the temperature detection element 11, the capacitance detection element 21, and the heater element 41 may be formed on a ceramic substrate. 2B, for example, the heater element 41 may be a separate component (separate chip), and the temperature detection element 11 and the capacitance detection element 21 may be formed on separate chips. May be.

  When the capacitance detection element is formed on the chip, it is preferable that the capacitance detection element is composed of a pair of comb-like electrodes 2a and 2b like a capacitance detection element 21a shown in FIG. According to this, the mixed fluid can be easily guided between the pair of comb-like electrodes 2a and 2b formed on the sensor chip 50 in FIG. 2B, and the detection capacitance can be increased by increasing the comb-tooth density. The value can be increased to increase the dielectric constant measurement accuracy.

  FIG. 3 is another configuration example of the sensor unit in the concentration detection apparatus 100 of FIG. 2A, and FIG. 3A is a top view schematically showing the sensor chip 51. 3B is a diagram showing the temperature distribution of the sensor chip 51 along the flow direction of the mixed fluid, and FIG. 3C is a cross-section of the sensor chip 51 along the flow direction of the mixed fluid. FIG.

In the sensor chip 51 shown in FIG. 3A, the heater element 42 is arranged at the center in the flow direction of the mixed fluid, the temperature detection element 12a and the capacitance detection element 22a on the upstream side, and the temperature detection element 12b on the downstream side. Capacitance detection elements 22b are respectively arranged. In the case of the sensor chip 51, as shown in the temperature distribution diagram of FIG. 3B, the dielectric constant measurement at different temperatures T ₁ and T ₂ can be simultaneously performed by heating the heater element 42.

  When a heater is provided on the sensor chip, the heater element 42 is thermally separated from the temperature detection elements 12a and 12b and the capacitance detection elements 22a and 22b as shown by the sensor chip 51 in FIG. Thus, it is preferable that the grooves 5a and 5b are formed. According to this, heat conduction through the chip from the heater element 42 to the temperature detection elements 12a and 12b and the capacitance detection elements 22a and 22b can be suppressed. For this reason, compared with the case where the groove parts 5a and 5b are not formed, the temperature and dielectric constant of the mixed fluid can be measured more accurately, and therefore the concentration of each component can be detected more accurately. The groove portions 5a and 5b can be easily formed by etching or the like in the sensor chip 51 made of a semiconductor substrate.

  FIG. 4 is a top view schematically showing another sensor chip 52.

In the sensor chip 52 shown in FIG. 4, the heater element 43a, a detection element portion 52a at temperatures _{T 1} surrounded by a broken line consisting of a temperature detecting element 13a and the capacitance detection element 23a, the heater element 43 b, the temperature detecting element 13b and the capacitance detection a detecting element section 52b at temperature T ₂ surrounded by the broken line consisting of elements 23b, are arranged in the same position in the flow direction of the mixed fluid. In the sensor chip 52 in FIG. 4, only one of the heater element 43a and the heater element 43b may be formed. In the sensor chip 52, the detection element unit 52a and the detection element unit 52b may be formed on the front side and the back side of the substrate, respectively.

  FIG. 5 is a diagram showing a preferred configuration example of the dielectric constant measurement unit 20 in the concentration detection apparatus 100 of FIG. 2A, and is a circuit block diagram showing the configuration of each part of the dielectric constant measurement unit 24.

The dielectric constant measuring unit 24 shown in FIG. 5 includes two capacitance detection elements Cs1 and Cs2 connected in series and a C / V converter 24a to which a feedback capacitance Cf is added. In the measurement of the dielectric constant at each temperature of the mixed fluid described above, the two capacitance detection elements Cs1 and Cs2 are respectively driven by carrier waves FE1 and FE2 having a predetermined voltage V shown in the drawing, and An output from the connection point of the capacitance detection elements Cs1, Cs2 is input to the C / V converter 24a. At this time, the output voltage Vs of the C / V converter 24a is
(Expression 4) Vs = V (Cs1-Cs2) / Cf
Thus, the difference between the two capacitance detection elements Cs1, Cs2 is C / V converted. From the output voltage Vs of Equation 4, the dielectric constant at each temperature of the mixed fluid can be measured. According to the dielectric constant measurement using the dielectric constant measurement unit 24 of FIG. 5, the influence of the parasitic capacitance Ce caused by the wiring can be canceled, so that the dielectric constant measurement can be performed with higher accuracy than when one capacitance detection element is used. It is possible, and the concentration of each component can be detected with higher accuracy.

  FIG. 6 is a diagram illustrating a configuration example of the two capacitance detection elements Cs1 and Cs2 illustrated in FIG. 5, and is a top view schematically illustrating the capacitance detection element 24b.

  6 includes a comb-like electrode 3a having a pad 4a, a comb-like electrode 3b having a pad 4b, and a comb-like electrode 3c having pads 4c and 4d. . In the capacitance detection element 24b of FIG. 6, the electrode 3a and the electrode 3c are paired, and the carrier wave FE1 is input to the pad 4a corresponding to the capacitance detection element Cs1 of FIG. The electrode 3b and the electrode 3c make a pair, and the carrier wave FE2 is input to the pad 4b corresponding to the capacitance detection element Cs2 of FIG. In the capacitance detection element 24b of FIG. 6, the output taken out from the pad 4c or the pad 4d is input to the output C / V converter 24a of FIG.

  In the capacitance detection element 24b of FIG. 6, the electrode 3c having the pads 4c and 4d may be formed of a resistance temperature detector, and the electrode 3c may also serve as the temperature detection element. As described above, when the capacitance detection element that is a component of the dielectric constant measurement unit includes a pair of electrodes, one of the electrodes also serves as a temperature detection element that is a component of the temperature measurement unit. Therefore, further downsizing and cost reduction are possible.

  FIGS. 7A and 7B are other configuration examples of the sensor unit in the concentration detection apparatus 100 of FIG. 2A and are sectional views schematically showing sensor components 61 and 62, respectively.

  The configuration example of the sensor unit in the concentration detection apparatus 100 of FIG. 2A described above is a sensor chip 50 to 52 that is used by being immersed in a mixed fluid. On the other hand, the sensor components 61 and 62 shown in FIGS. 7A and 7B are attached to the pipe 70 for use. The sensor component 61 shown in FIG. 7A includes a pair of flat plate electrodes 6a and 6b and a thermocouple 6c that is a temperature detection element. The sensor component 62 shown in FIG. 7B includes a pair of cylindrical electrodes 7a and 7b and a thermocouple 7c that is a temperature detection element.

  When measuring the dielectric constant of fuel in a vehicle, a heater can be installed outside or inside the pipe 70 to change the temperature of the fuel passing through the pipe 70. Sensor parts 61 and 62 as shown in FIGS. 7 (a) and 7 (b) are provided at any two locations immediately below the heating section by the heater, upstream of the flow from the heating section, or downstream of the flow from the heating section. By installing, the concentration of each component can be measured without changing the temperature setting of the heater as shown in FIG.

  FIG. 8 is a diagram showing a configuration example suitable for using a capacitance detection element having a large electrode size, such as the sensor parts 61 and 62 shown in FIGS. 7A and 7B.

  In the configuration shown in FIG. 8, the mixed fluid agitating means 80 is provided between the heater element 44 disposed on the upstream side of the mixed fluid and the temperature detecting element 14 and the capacity detecting element 25 disposed on the downstream side of the mixed fluid. Is provided. According to this, for example, by the stirring means 80 such as fins, meshes, filters, etc., temperature unevenness of the mixed fluid due to heating using the heater element 44 is eliminated, and the temperature and dielectric constant of the mixed fluid are measured more accurately. Can do. Therefore, in the configuration shown in FIG. 8, the concentration of each component of the mixed fluid can be detected more accurately. In particular, in the case of a capacitance detecting element having a large electrode size, such as the sensor parts 61 and 62 shown in FIGS. 7A and 7B, the volume of the mixed fluid between the electrodes is large. It is necessary to make the temperature of the mixed fluid between the electrodes uniform.

Using the sensor unit as described above, for example, the dielectric constant of a mixed fluid composed of three types of components A, B, and C is measured at two different temperatures, and the concentration calculation unit shown in FIG. By solving the simultaneous equations shown in Equations 1 to 3 at 30, the concentrations a, b, and c of the components A, B, and C can be calculated. In the case of a mixed fluid composed of N (≧ 3) types of components, the dielectric constant of the mixed fluid is measured at different temperatures at (N−1) points, and the equations 1 to 3 are generalized as described above. Thus, a ₁ , a ₂ ,..., A _N can be calculated for the concentrations (existence ratios) of the respective components.

  As described above, the above-described mixed fluid concentration detection method and detection device detect the concentration of each component of the mixed fluid composed of N (≧ 3) types of known components and detect the concentration of the mixed fluid. This is a method and a detection apparatus, which are a mixed fluid concentration detection method and a detection apparatus capable of accurately detecting the concentration of a mixed fluid composed of three or more components.

  Therefore, the above-described mixed fluid concentration detection method and concentration detection device are suitable for detecting the concentration of the mixed fuel of an internal combustion engine in which water may be mixed. For example, the components are ethanol, gasoline, and water. Alternatively, it is suitable when the components are fatty acid methyl ester, light oil and water.

DESCRIPTION OF SYMBOLS 100 Concentration detection apparatus 10 Temperature measurement part 11,12a, 12b, 13a, 13b Temperature detection element 20,24 Permittivity measurement part 21,21a, 22a, 22b, 23a, 23b Capacitance detection element 30 Concentration calculation part 40 Heater part 41, 42, 43a, 43b Heater element 50-52 Sensor chip 61, 62 Sensor component 70 Piping 80 Stirring means

Claims (17)

A mixed fluid concentration detection method for detecting the concentration of each component of a mixed fluid composed of N (> 3 integer) known components,
(N-1) Measure the dielectric constant of the mixed fluid at different temperatures.
The concentration of each component is calculated from the dielectric constant of each known component at each temperature at the (N-1) point and the dielectric constant of the mixed fluid measured at each temperature at the (N-1) point. A method for detecting the concentration of a mixed fluid, comprising: N is 3,
The concentrations of the components are a, b and c, the two different temperatures are T ₁ and T ₂ , respectively, and the dielectric constants of the components at the temperature T ₁ are ε _a1 , ε _b1 and ε _c1 , respectively. , When the dielectric constants of the components at the temperature T ₂ are ε _a2 , ε _b2 , and ε _c2 , respectively, and the dielectric constants of the mixed fluid at the temperature T ₁ and the temperature T ₂ are ε ₁ and ε ₂ , respectively.
(Formula 1) a + b + c = 1
(Equation 2) ε ₁ = ε _a1 · a + ε _b1 · b + ε _c1 · c
(Equation 3) ε ₂ = ε _a2 · a + ε _b2 · b + ε _c2 · c
The concentration detection method for a mixed fluid according to claim 1, wherein the concentration of each component is calculated from:   3. The mixed fluid concentration detection method according to claim 2, wherein the components are ethanol, gasoline, and water.   The mixed component concentration detection method according to claim 2, wherein the components are fatty acid methyl ester, light oil, and water. In measuring the dielectric constant at each temperature of the mixed fluid,
Two capacitance detection elements connected in series are driven by a carrier wave having a reverse voltage, and an output from a connection point of the two capacitance detection elements is input to a C / V converter to which a feedback capacitance is added. 5. The mixed fluid concentration detection method according to claim 1, wherein a dielectric constant at each temperature of the mixed fluid is measured from an output voltage of the C / V converter. A mixed fluid concentration detection device that detects the concentration of each component of a mixed fluid composed of N (> 3 integer) known components,
A temperature measuring unit capable of measuring the temperature of the mixed fluid at different (N-1) points;
A dielectric constant measuring unit capable of measuring the dielectric constant of the mixed fluid at different temperatures of the (N-1) points;
From the dielectric constant of each known component at each temperature of the (N-1) point stored in the memory and the dielectric constant of the mixed fluid measured at different temperatures of the (N-1) point, A mixed fluid concentration detection device comprising a concentration calculation unit for calculating a concentration of a component. The concentration detector is
The mixed fluid concentration detection device according to claim 6, further comprising a heater unit for forming different temperatures of the (N−1) points of the mixed fluid.   8. The mixing according to claim 6, wherein the temperature detection element that is a component of the temperature measurement unit and the capacitance detection element that is a component of the dielectric constant measurement unit are formed on one chip. Fluid concentration detection device.   A temperature detection element that is a component of the temperature measurement unit, a capacitance detection element that is a component of the dielectric constant measurement unit, and a heater element that is a component of the heater unit are formed on one chip. The mixed fluid concentration detection device according to claim 7. In the chip,
The mixed fluid concentration detection device according to claim 9, wherein a groove is formed so as to thermally separate the heater element, the temperature detection element, and the capacitance detection element.   The mixed fluid concentration detection device according to any one of claims 8 to 10, wherein the capacitance detection element includes a pair of comb-shaped electrodes. A heater element that is a component of the heater unit arranged on the upstream side of the mixed fluid, a temperature detection element that is a component of the temperature measuring unit arranged on the downstream side of the mixed fluid, and the dielectric constant measurement unit Between the capacitance detection element that is a component of
8. The mixed fluid concentration detection device according to claim 7, further comprising stirring means for the mixed fluid. The capacitance detection element that is a component of the dielectric constant measurement unit is composed of a pair of electrodes,
13. The mixed fluid concentration detection device according to claim 6, wherein one of the electrodes also serves as a temperature detection element that is a component of the temperature measurement unit. The dielectric constant measuring unit is
Comprising two capacitance detection elements connected in series and a C / V converter to which a feedback capacitance is added;
In measuring the dielectric constant at each temperature of the mixed fluid,
The two capacitance detection elements are driven by a carrier wave having a predetermined voltage and the output from the connection point of the two capacitance detection elements is input to the C / V converter. The output of the C / V converter 14. The mixed fluid concentration detection device according to claim 6, wherein a dielectric constant at each temperature of the mixed fluid is measured from a voltage. N is 3,
The concentration calculator is
The concentrations of the components are a, b and c, the two different temperatures are T ₁ and T ₂ , respectively, and the dielectric constants of the components at the temperature T ₁ are ε _a1 , ε _b1 and ε _c1 , respectively. , When the dielectric constants of the components at the temperature T ₂ are ε _a2 , ε _b2 , and ε _c2 , respectively, and the dielectric constants of the mixed fluid at the temperature T ₁ and the temperature T ₂ are ε ₁ and ε ₂ , respectively.
(Formula 1) a + b + c = 1
(Equation 2) ε ₁ = ε _a1 · a + ε _b1 · b + ε _c1 · c
(Equation 3) ε ₂ = ε _a2 · a + ε _b2 · b + ε _c2 · c
The concentration detection device for a mixed fluid according to claim 6, wherein the concentration of each component is calculated from the above.   The mixed fluid concentration detection device according to claim 15, wherein the components are ethanol, gasoline, and water.   The mixed fluid concentration detection device according to claim 15, wherein the components are fatty acid methyl ester, light oil, and water.

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