JP2009036746A - Fuel property detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel property detection device capable of detecting both of a degree of heaviness of gasoline and an alcohol concentration contained in the gasoline accurately, and reducing a size and the number of components of the device. <P>SOLUTION: The fuel property detection device includes a light emitting diode 2 and a PSD 3 as a set of detection means, and detects an ethanol concentration from correlationship between a received amount of light of the PSD 3, a measured light reduction degree when the fuel permeates, and the alcohol concentration, and detects the degree of the heaviness of the gasoline from correlationship between a gravity position of light quantity in the PSD 3, the degree of the heaviness of the gasoline, and a total reflection angle. Thereby, both of the degree of the heaviness of the gasoline and the alcohol concentration contained in the gasoline can be detected accurately, and the size and the number of components can be reduced. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a so-called optical fuel property detection device that includes a light source that emits measurement light and a light receiving device that receives the measurement light, and detects the property of the fuel.

As a conventional fuel property detection device, for example, the light emitted from the light emitting element is reflected on the boundary surface of the prism in contact with the gasoline, and the gasoline heavyness and the refractive index are correlated with each other. The configuration detects the alcohol concentration contained in gasoline by detecting the gasoline severity from the change and using the correlation between the concentration of alcohol contained in gasoline and the capacitance between the pair of electrodes. There is a thing (refer patent document 1).
JP-A-5-133886

  According to the above-described conventional fuel property detection device, it is possible to detect the severity of gasoline and the concentration of alcohol contained in the gasoline. However, according to such a configuration, the fuel property detection device includes a gasoline severity detection unit including a light emitting element and a light receiving element, and an alcohol concentration detection unit including a pair of electrode plates, and further includes detection by each detection unit. Since two electric circuits for controlling the operation are provided, the size of the fuel property detecting device is increased, and the electric circuit for controlling the fuel property detecting device is complicated.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a fuel property detection device that can accurately detect both the gasoline heavyness and the alcohol concentration contained in gasoline, can be downsized, and can reduce the number of parts. Is to provide.

  In order to achieve the above object, the present invention employs the following technical means.

  The fuel property detection device according to claim 1 of the present invention is arranged such that a light guide made of a light-transmitting material is arranged so that a part thereof is in close contact with the fuel, and light can be incident on the light guide. A light source and a light receiving device arranged to be able to receive measurement light, which is light emitted from the light source traveling in the light guide, and receives the measurement light and outputs fuel based on a detection signal output from the light receiving device. A fuel property detection device for detecting properties, wherein the light guide includes an exit surface, which is a surface from which the measurement light exits from the light guide into the fuel, and an exit surface facing the exit surface and exiting from the exit surface. An incident surface that is a surface on which the measurement light transmitted through the light guide is incident, and a reflective surface that is a surface that reflects the measurement light incident from the incident surface toward the light receiving device. The space between the two is filled with fuel and the reflective surface is in close contact with the fuel It is.

  According to the configuration described above, the measurement light emitted from the light source exits from the exit surface of the light guide into the fuel, passes through the fuel, and then enters the light guide again from the entrance surface. Then, the light is reflected by the reflecting surface serving as the interface between the light guide and the fuel and enters the light receiving device.

  Here, the fuel property detection principle by the fuel property detection device according to claim 1 of the present invention, that is, the detection principle of the gasoline heavyness and the alcohol concentration contained in the gasoline will be described.

  First, the principle of detecting the gasoline severity will be described. When the measurement light traveling in the light guide is incident on the reflective surface that is in close contact with the fuel, light that is incident on the reflective surface that is greater than the total reflection angle of the light guide is totally reflected on the reflective surface. Then, the light travels through the light guide and enters the light receiving device. On the other hand, light whose incident angle to the reflecting surface is less than the total reflection angle is emitted from the reflecting surface into the fuel and does not enter the light receiving device. The total reflection angle θ of the light guide is determined by the ratio between the refractive index N1 of the light guide and the refractive index N2 of gasoline, which is a medium in contact with the reflecting surface. That is, the magnitude of the total reflection angle θA is expressed by the following equation (1).

sin θA = N2 / N1 (1)
Furthermore, there is a relationship between the degree of gasoline and the refractive index that the higher the degree of weight, the higher the refractive index. Therefore, from this relationship and the equation (1), it can be seen that the total reflection angle on the reflection surface of the light guide increases as the gasoline is heavier.

  As described above, of the measurement light, only light whose incident angle to the reflecting surface is greater than or equal to the total reflection angle of the light guide is totally reflected by the reflecting surface, travels through the light guide, and enters the light receiving device. That is, the incident angle of the measurement light incident on the light receiving device is in a certain angle range. In other words, the incident area that is the part where the measurement light is incident in the light receiving amount area of the light receiving device is limited to a certain range. Then, when the degree of gasoline that is in close contact with the reflecting surface changes and the total reflection angle on the reflecting surface changes, the incident region of the measurement light in the light receiving amount region of the light receiving device changes accordingly. The light receiving device provided in the fuel property detecting device according to claim 1 of the present invention can detect the illuminance distribution in the light receiving region. Therefore, the gasoline severity can be detected based on the detection signal from the light receiving device, that is, the illuminance distribution detection signal in the light receiving region.

  Next, the detection principle of the alcohol concentration contained in gasoline will be described.

  The OH group in the alcohol has an action of absorbing light in a specific wavelength region, specifically, light in the infrared wavelength region. For this reason, when the light emitted from the light source passes through the alcohol, the amount of light after passing through the alcohol decreases with respect to the amount of light emitted from the light source. On the other hand, when the light emitted from the light source passes through gasoline, there is almost no light absorption, so there is no decrease in the amount of light after transmission. Therefore, the amount of transmitted light when light from a light source is transmitted through a liquid mixture of gasoline and alcohol reaches a maximum value when the gasoline concentration is 100%, that is, the alcohol concentration is 0%, and the alcohol concentration contained in the gasoline increases. As you do it will decrease. The amount of light emitted from the light source can be obtained in advance from the light emission characteristics of the light source, the drive current conditions, and the like. Therefore, if the light from the light source is transmitted through the mixed liquid of gasoline and alcohol filled in the space sandwiched between the exit surface and the entrance surface of the light guide and the amount of light after transmission is measured, The alcohol concentration of can be detected.

  The light receiving device included in the fuel property detecting device according to claim 1 of the present invention can detect the total amount of light received in the light receiving region. The amount of received light detected by the light receiving device is included in the fuel when the amount of light emitted from the light source passes through the fuel filled in the space sandwiched between the exit surface and the entrance surface of the light guide. Since the amount of light absorbed by the alcohol and the angle of incidence on the reflecting surface in close contact with the fuel is smaller than the total reflection angle, the amount of light emitted into the fuel is reduced. The illuminance distribution detection signal in the light receiving region of the light receiving device corresponding to the gasoline severity is constant regardless of the change in the amount of light received in the light receiving region if the severity is constant. Therefore, apart from the alcohol concentration in gasoline, the severity of gasoline can be detected based on the illuminance distribution detection signal in the light receiving region. Next, regarding the alcohol concentration in gasoline, the relationship between the total amount of light received in the light receiving area of the light receiving device and the alcohol concentration is prepared in advance as data for various gasoline heavinesses. It can be obtained by referring to the data. That is, first, the severity of gasoline is detected based on the illuminance distribution detection signal from the light receiving device, and then the total amount of light received in the light receiving region of the light receiving device in the detected liquid mixture of gasoline and alcohol of the heavy strength. The alcohol concentration can be detected based on the data indicating the relationship between the alcohol concentration and the total light reception amount detection signal in the light receiving device.

  The conventional fuel property detection device is provided with two detection means for detecting the severity of gasoline and for detecting the alcohol concentration in the gasoline. Therefore, the electric circuit for controlling the fuel property detecting device has been complicated.

  On the other hand, according to the fuel property detection device of the first aspect of the present invention, as described above, two pieces of information on the gasoline severity and the alcohol concentration in the gasoline are detected by one detection means. That is, it can measure simultaneously using one light source and one light receiving device. Therefore, it is possible to provide a fuel property detection device capable of accurately detecting both the gasoline heavyness and the alcohol concentration contained in the gasoline, miniaturizing, and reducing the number of parts.

  Here, as in the fuel property detection device according to claim 2 of the present invention, the measurement light is emitted from the light source and incident on the light guide, then passes through the fuel between the exit surface and the entrance surface, and thereafter Reflected by the reflecting surface and incident on the light receiving device, the light receiving device can detect the total received light amount and illuminance distribution in the light receiving area, and the light receiving device is arranged so that the measurement light reflected by the reflecting surface can enter In this configuration, first, the severity of gasoline is accurately detected based on the illuminance distribution in the light reception area, and then alcohol is detected based on the total light reception in the light reception area and the detected gasoline severity. The concentration can be accurately detected.

  The fuel property detection device according to claim 3 of the present invention is characterized in that the light receiving device is a PSD (Psition Sensitive Detector).

  The PSD can detect the illuminance distribution in the detection region with high accuracy and has a wide variety of sizes and characteristics. Therefore, it is possible to provide a fuel property detection device with high detection accuracy while suppressing an increase in cost.

  The fuel property detecting device according to claim 4 of the present invention is characterized in that the light receiving device is formed by arranging a plurality of phototransistors or photodiodes adjacent to each other on a straight line.

  In the above-described configuration, the light receiving region of the light receiving device includes a plurality of phototransistors or photodiodes. In this case, the illuminance distribution in the received light amount region can be detected with high accuracy based on the detection signal of each phototransistor or photodiode provided in the light receiving device. Therefore, the fuel property detection device according to claim 4 of the present invention can also provide a fuel property detection device capable of accurately detecting both the gasoline severity and the alcohol concentration, miniaturized, and reduced in the number of parts. .

  The fuel property detection apparatus according to claim 5 of the present invention is characterized in that the light source is a light emitting diode.

  Light emitting diodes have a wide variety of emission wavelength ranges and have a long lifetime. Therefore, it is possible to easily select a light emitting diode that is optimal for the concentration detection target component contained in the fuel, that is, a light emitting diode that emits light in a wavelength region that is selectively absorbed by the detection target component. Thereby, the fuel property detection apparatus which can detect the density | concentration of the detection target component contained in a fuel with high precision can be provided.

  The fuel property detection apparatus according to claim 6 of the present invention is characterized in that the fuel is a mixed liquid of different fuels and the wavelength range of the measurement light is in the near infrared region.

  As a mixed liquid of different fuels, for example, a mixed liquid of gasoline and alcohol is considered. Alcohol selectively absorbs light in the near infrared wavelength range, whereas gasoline completely transmits light in that wavelength range. Therefore, when the fuel is a mixed liquid of gasoline and alcohol, the alcohol concentration can be detected with high accuracy by applying light having a wavelength range in the near infrared region as measurement light.

  According to a seventh aspect of the present invention, there is provided a fuel property detection apparatus comprising a calculation means having a storage means for previously storing, as a first map, data on the relationship between the refractive index of the fuel and the reflectance at the reflecting surface. The means is characterized in that the refractive index of the fuel and the transmittance of the fuel are calculated based on the detection signal output from the light receiving device and the first map.

  The measurement light emitted from the light source passes through the fuel on the way and then enters the reflection surface of the light guide, where it is reflected and reaches the light receiving device. In this configuration, the measurement light quantity incident on the light receiving device is obtained by subtracting the light quantity emitted from the light source from the light quantity absorbed by the fuel during fuel permeation and the light quantity emitted into the fuel from the reflecting surface.

  The total reflection angle when the measurement light is incident on the reflecting surface is determined by the refractive index of the fuel. When the refractive index of the fuel changes, the total reflection angle also changes accordingly, and the amount of light emitted from the reflecting surface into the fuel changes. . In other words, the amount of light that travels toward the light receiving device after being totally reflected by the reflecting surface changes. As a result, the amount of light received by the light receiving device and the illuminance distribution of the amount of light received by the light receiving device change.

  When the refractive index of the fuel is constant and only the fuel transmittance changes, the amount of light received by the light receiving device changes, but the illuminance distribution of incident light to the light receiving device does not change. Therefore, the refractive index of the fuel can be calculated based on the illuminance distribution of the incident light to the light receiving device. If the calculated refractive index is referred to in the first map, the reflectance at the reflecting surface of the light guide is obtained. Based on this reflectance and the amount of light received by the light receiving device, the amount of light incident on the reflecting surface, that is, the amount of light measured after passing through the fuel is calculated. The fuel transmittance can be calculated based on the measured light quantity after fuel permeation and the measured light quantity before fuel permeation, that is, the light quantity emitted from the light source. The measured light quantity before fuel permeation can be obtained in advance from the light emission characteristics of the light source, the drive current conditions, and the like. Accordingly, the fuel transmittance can be calculated based on the amount of light incident on the reflecting surface calculated by the calculation means and the amount of light emitted from the light source. Based on the refractive index calculated as described above, the gasoline heavyness can be calculated, and the alcohol concentration can be calculated based on the transmittance. Therefore, it is possible to provide a fuel property detection device capable of accurately detecting both the gasoline heavyness and the alcohol concentration contained in the gasoline, miniaturizing, and reducing the number of parts.

  In this case, as in the fuel property detecting device according to claim 8 of the present invention, the calculating means includes a refractive index calculating means for calculating the refractive index of the fuel based on the detection signal from the light receiving device, and a refractive index calculating means. Based on the calculated refractive index and the first map, the reflectance calculating means for calculating the reflectance at the reflecting surface, the reflectance calculated by the reflectance calculating means, the light receiving device, the detection signal, and the amount of light emitted from the light source If the configuration includes the transmittance calculating means for calculating the fuel transmittance based on the calculation means, the refractive index and the transmittance of the fuel can be reliably and accurately calculated by the calculating means.

  According to a ninth aspect of the present invention, there is provided a fuel property detection device that stores in advance, as a second map, data relating to the total amount of light received by the light receiving device when the refractive index of the fuel and the transmittance of the fuel are known. The calculation means includes a storage means, and the calculation means calculates the refractive index of the fuel and the transmittance of the fuel based on the detection signal output from the light receiving device and the second map.

  The measurement light emitted from the light source passes through the fuel on the way and then enters the reflection surface of the light guide, where it is reflected and reaches the light receiving device. In this configuration, the measurement light quantity incident on the light receiving device is obtained by subtracting the light quantity emitted from the light source from the light quantity absorbed by the fuel during fuel permeation and the light quantity emitted into the fuel from the reflecting surface.

  The total reflection angle when the measurement light is incident on the reflecting surface is determined by the refractive index of the fuel. When the refractive index of the fuel changes, the total reflection angle also changes accordingly, and the amount of light emitted from the reflecting surface into the fuel changes. . In other words, the amount of light that travels toward the light receiving device after being totally reflected by the reflecting surface changes. As a result, the amount of light received by the light receiving device and the illuminance distribution of the amount of light received by the light receiving device change.

  When the refractive index of the fuel is constant and only the fuel transmittance changes, the amount of light received by the light receiving device changes, but the illuminance distribution of incident light to the light receiving device does not change. Therefore, the refractive index of the fuel can be calculated based on the illuminance distribution of the incident light to the light receiving device.

  In addition, when the refractive index of the fuel is constant, the amount of light incident on the light receiving device varies only depending on the amount of light absorbed by the fuel during fuel permeation, that is, the amount of absorbed light. In other words, it fluctuates only with the fuel permeability. Therefore, the amount of light incident on the light receiving device when the refractive index of the fuel is constant becomes maximum when the fuel transmittance is 100%, and decreases as the fuel transmittance decreases from 100%. That is, if the ratio between the amount of light actually received by the light receiving device and the amount of light incident on the light receiving device when the fuel transmittance at a refractive index calculated based on the illuminance distribution of incident light to the light receiving device is known, The fuel permeability can be calculated.

  Based on the refractive index calculated as described above, the gasoline heavyness can be calculated, and the alcohol concentration can be calculated based on the transmittance. Therefore, it is possible to provide a fuel property detection device capable of accurately detecting both the gasoline heavyness and the alcohol concentration contained in the gasoline, miniaturizing, and reducing the number of parts.

  In this case, as in the fuel property detection device according to claim 10 of the present invention, the calculation means includes a refractive index calculation means for calculating the refractive index of the fuel based on the detection signal from the light receiving device, and a refractive index calculation means. If the configuration includes the calculated refractive index, the second map, and the transmittance calculating means for calculating the fuel transmittance based on the detection signal from the light receiving device, the calculating means calculates the refractive index and the transmittance of the fuel. It can be calculated reliably and accurately.

  Hereinafter, an embodiment of a fuel property detection device according to the present invention will be described with reference to the drawings, taking as an example a case where the fuel property detection device is applied to a fuel property sensor 1 mounted on an automobile.

  As shown in FIG. 1, the fuel property sensor 1 is attached to a fuel pipe 100 that supplies fuel in a fuel tank (not shown) to an engine (not shown). That is, it is fixed to the boss portion 100 a provided in the fuel pipe 100 by screw fastening through the gasket 101. When the fuel F flows through the fuel pipe 100, the fuel F also flows into the fuel property sensor 1.

  Here, the fuel F will be described. As the fuel F, a mixture of gasoline and ethanol which is alcohol is used. The fuel F has a large variation in the content of heavy components (for example, aroma, olefin, etc.) of gasoline (hereinafter referred to as “heavyness”), and the concentration of ethanol contained also varies. For this reason, while using the fuel F whose component ratio varies widely as described above, the engine (not shown) is always in an appropriate state, for example, a desired torque is generated and the amount of harmful components in the exhaust gas is minimized. In order to operate in such a state, the fuel properties, that is, the gasoline heavyness and the ethanol concentration contained in the gasoline are detected by some means, and the fuel injection amount, the injection timing, etc. are appropriately controlled based on the detected fuel properties. There is a need. The fuel property sensor 1 is used for such a purpose.

  Below, the structure of the fuel property sensor 1 which concerns on this invention is demonstrated.

  The fuel property sensor 1 is roughly composed of a light guide 4 arranged so that a part thereof is immersed in the fuel F, a light emitting diode 2 arranged so that light can enter the light guide 4, and a light guide. 4 includes a PSD (Position Sensitive Detector) 3 that is arranged so that light from the light emitting diode 2 traveling in the light can enter, and a housing 7 that accommodates and holds these components.

  The light guide 4 is formed in a substantially block shape from glass which is a translucent material. The light guide 4 emits the measurement light, which is the light emitted from the light emitting diode 2 incident on the light guide 4, from the emission surface 41, which is the surface from which the measurement light is emitted into the fuel F, and the fuel F through the emission surface 41. An incident surface 42 that is a surface through which the transmitted measurement light is incident again into the light guide 4, and a reflection surface 43 that is a surface that reflects the measurement light incident from the incident surface 42 into the light guide 4 toward the PSD. ing. As shown in FIG. 1, the exit surface 41 and the entrance surface 42 are formed opposite to each other and in parallel. That is, the emission surface 41 and the incident surface 42 are formed as wall surfaces constituting the recess S by providing the light guide 4 with the recess S. In the state where the fuel property sensor 1 is attached to the fuel pipe 100, the recess S is filled with the fuel F, and at the same time, the fuel adheres to the reflecting surface 43.

  As the light-emitting diode 2 that is a light source, a light-emitting diode having a center wavelength of light emitted near 1600 nm is used. This is because light having a wavelength of around 1600 nm is not absorbed by gasoline, so the transmittance when passing through gasoline is almost 100%, whereas it is absorbed by ethanol, so it passes through ethanol. This is due to the low transmittance. When light of such a wavelength is used as measurement light, when the composition of the fuel F is 100% gasoline, the transmittance of the measurement light in the fuel F is maximum, that is, the amount of measurement light transmitted through the fuel F is maximum. Thus, as the concentration of ethanol contained in the fuel F increases, the transmittance of the measurement light in the fuel F decreases, that is, the amount of the measurement light transmitted through the fuel F decreases. For applications in which the ethanol concentration in a liquid mixture of gasoline and ethanol is detected, light with a wavelength such that the transmittance in gasoline is almost 100% and the transmittance in ethanol is as low as possible is suitable. The light emitting diode 2 is disposed with its light emitting surface in close contact with the light guide 4. Thereby, the light emitted from the light-emitting diode 2 can be incident into the 100% light guide 4, and the amount of measurement light can be increased to improve the fuel property detection accuracy. Light is emitted radially from the light emitting diode 2, but the light path having the maximum luminance is the optical axis P. In the fuel property sensor 1 according to the embodiment of the present invention, the light emitting diode 2 is installed such that the optical axis P of the light emitting diode 2 and the exit surface 41 and the entrance surface 42 of the light guide 4 are orthogonal to each other. Thereby, the light leakage loss at the time when the measurement light passes through the emission surface 41 and the incident surface 42 can be minimized.

  One-dimensional PSD is used as PSD3 which is a light receiving device. As shown in FIG. 2, the PSD 3 includes a strip-shaped detection surface 31. Here, the structure of the PSD 3 and the light detection operation will be described. As shown in FIG. 3, the PSD has the same structure as a PIN photodiode, and the P layer 32 forms a detection surface. A pair of output electrodes 33 and 34 are formed at both ends of the P layer 32. A common electrode 36 is formed on the N layer 35. Also, an I layer (Intrinsic semiconductor layer) 37 is provided between the P layer 32 and the N layer 35. As shown in FIG. 3, when the spot light S is incident on the detection surface 31 of the PSD 3, an electric charge proportional to the amount of light is generated at the incident position, and this electric charge reaches the P layer 32 as a photocurrent, and each output electrode It is divided in inverse proportion to the distance to 33 and 34 and taken out from the output electrodes 33 and 34. By measuring the output current I33 of the output electrode 33 and the output current I34 of the output electrode 34, the incident position of the spot light S, that is, the distance from the output electrode 33 or the output electrode 34 to the incident position can be calculated. Further, the total amount of light incident on the detection surface 31 can be calculated based on the total photocurrent I0 that is the sum of the output current I33 and the output current I34. When the light incident on the detection surface 31 is not the spot light S but enters a certain range of the detection surface 31, the incident position calculated based on the output current I33 and the output current I34 is the center of gravity of the incident light amount. Corresponds to position.

  The light guide 4, the light emitting diode 2, and the PSD 3 described above are integrally held and fixed via a holder 5 as shown in FIG. 1. The holder 5 is made of, for example, a resin material. A circuit board 6 is attached to the holder 5. The circuit board 6 is formed with an electric circuit (not shown) that performs lighting drive control of the light emitting diode 2, detection signal processing from the PSD 3, light incident position calculation processing, and the like.

  As shown in FIG. 1, the light guide 4, the holder 5 that integrally holds and fixes the light emitting diode 2 and the PSD 3, and the circuit board 6 are housed and fixed in the housing 7. The housing 7 is made of, for example, a metal material. The housing 7 is provided with a communication hole 71 that opens at one end thereof and faces the light guide 4. As shown in FIG. 1, a cover 8 is attached to the housing 7 at the end opposite to the communication hole 71. The cover 8 hermetically protects the light guide 4, the light emitting diode 2, the PSD 3, and the circuit board 6 in the housing 7. The cover 8 is provided with an electrical connector (not shown), and the electrical connector (not shown) is electrically connected to the circuit board 6. By connecting an external electrical wiring to the electrical connector (not shown), the fuel property sensor 1 is connected to an external electrical circuit.

  The fuel property sensor 1 is attached to the fuel pipe 100 via the housing 7. That is, as shown in FIG. 1, the fuel property sensor 1 is fixed to the boss portion 100 a of the fuel passage 100 via a gasket 101 by screwing. When the fuel property sensor 1 is fixed to the fuel pipe 100, the fuel F in the fuel pipe 100 reaches the light guide 3 through the communication hole 71, and the light guide 4 is immersed in the fuel F. That is, the fuel F fills the concave portion S of the light guide 3 and the fuel F adheres to the reflecting surface 43.

  Next, the operation of the fuel property sensor 1 according to the embodiment of the present invention configured as described above, that is, the fuel property detection operation will be described.

  In the fuel property sensor 1 according to the embodiment of the present invention, light emitted from the light emitting diode 2, that is, measurement light travels as indicated by an arrow in FIG. 1 and enters the PSD 3. That is, after traveling through the light guide 4, the light exits from the exit surface 41 into the fuel F, passes through the fuel F, and enters the light guide 4 again from the entrance surface 42. Then, the light travels through the light guide 4, is reflected by the reflecting surface 43, and enters the detection surface 31 of the PSD 3.

  In the path from the measurement light emitted from the light emitting diode 2 to the light received by the PSD 3, first, the measurement light transmitted through the fuel F is reflected by the reflection surface 43 and reflected to the PSD 3. Consider the state of reflection at the surface 43. When the measurement light is incident on the reflection surface 43, the light having an incident angle θ with respect to the reflection surface 43 that is equal to or greater than the total reflection angle of the reflection surface 43 among the measurement light is totally reflected by the reflection surface 43 and enters the PSD 3. On the other hand, light having an incident angle θ with respect to the reflection surface 43 that is less than the total reflection angle of the reflection surface 43 is emitted from the reflection surface 43 to the outside of the light guide 4, that is, into the fuel F.

  The total reflection angle θA at the reflection surface 43 that is an interface between the light guide 4 and the fuel F is determined by the refractive index of the medium in contact with the light guide 4, that is, the fuel F. When the refractive index of the fuel F changes, the total reflection angle θA on the reflecting surface 43 also changes accordingly. When the refractive index of the light guide 4 is N1 and the refractive index of gasoline is N2, the magnitude of the total reflection angle θA is expressed by the following equation (1).

sin θA = N2 / N1 (1)
Furthermore, there is a relationship between the gasoline heaviness and the gasoline refractive index N2 that the greater the heaviness, the greater the refractive index. From this relationship and the equation (1), it can be seen that the total reflection angle θA on the reflecting surface 43 of the light guide 4 increases as the gasoline becomes heavier.

  For this reason, when the severity of gasoline in the fuel F changes, the total reflection angle θA on the reflecting surface 43 changes. Along with this, the incident area and the amount of incident light on the detection surface 31 of the PSD 3 of the measurement light reflected by the reflection surface 43 and directed to the PSD 3 change. Hereinafter, this phenomenon will be described with reference to FIG.

  The measurement light is emitted radially around the light emitting diode 2, specifically in a conical shape. FIG. 4 shows a cross section including the optical axis of the light emitted from the light emitting diode 2, that is, the optical path of the light having the highest luminance. In FIG. 4, the optical paths forming both ends of the radial measurement light distribution range are indicated by alternate long and short dash lines. Here, let us consider a case where the gasoline severity decreases and the total reflection angle changes from the total reflection angle θA1 to the total reflection angle θA2. Note that θA1> θA2. In FIG. 4, the optical path of the total reflection angle θA1 is indicated by an optical path V, and the optical path of the total reflection angle θA2 is indicated by an optical path W. Of the measurement light incident on the reflective surface 43, light having an incident angle with respect to the reflective surface 43 equal to or greater than the total reflection angle θA is incident on the PSD 3. Therefore, the incident region of the measurement light on the detection surface 31 of the PSD 3 is the incident region X in the case of the total reflection angle θA1 and the incident region Y in the case of the total reflection angle θA2, as shown in FIG. Here, the light quantity centroid position in the incident area X is the light quantity centroid position Xg, and the light quantity centroid position in the incident area Y is the light quantity centroid position Yg. In the fuel property sensor 1, the light quantity centroid position Xg and the light quantity centroid position Yg are calculated based on the detection signal from the PSD 3. Since these light intensity barycentric positions Xg and Yg have a correlation with the severity of gasoline, the light intensity barycentric position of the measurement light is calculated based on the output signal from the PSD 3 when the measurement light is received. By referring to the relationship between the position and the previously measured gasoline severity, the gasoline severity can be detected. By the way, PSD3 is arrange | positioned so that measurement light can be reliably received even if the incident area | region of measurement light changes corresponding to the fluctuation | variation of the heavyness of gasoline. That is, in the fuel property sensor 1 according to one embodiment of the present invention, a one-dimensional PSD is used as the PSD 3 and the spreading direction (longitudinal direction) of the detection range is shown in the cross-sectional view shown in FIG. It is arranged along the cross section including the shaft.

  Next, consider a path through which the measurement light emitted from the light emitting diode 2 passes through the fuel F from the light guide 4, travels again through the light guide 4, and reaches the reflecting surface 43. When the measurement light travels through the light guide 4, there is almost no loss in the amount of light. On the other hand, when the light passes through the fuel F, the measurement light is absorbed by ethanol contained in the fuel F, and the amount of the measurement light is reduced. That is, as the concentration of ethanol contained in the fuel F increases, the degree of decrease in the measurement light after passing through the fuel F increases. Therefore, if the light quantity of the measurement light after passing through the fuel F is measured, the ethanol concentration can be detected based on the measurement light quantity. However, in the fuel property sensor 1 according to the embodiment of the present invention, a part of the measurement light transmitted through the fuel F is emitted from the reflection surface 43 to the outside even when the measurement light is subsequently reflected by the reflection surface 43. In order to reduce the amount of light. Therefore, even if the amount of decrease in the measurement light is calculated based on the amount of light received by the PSD 3, it is the sum of the amount of light absorbed by ethanol and the amount of light emitted from the reflecting surface 43 to the outside. It cannot be measured. Therefore, the relationship between the amount of received light detected by the PSD 3 and the ethanol concentration is measured in advance for each of the gasoline gasoline weights. First, based on the center of gravity of the light quantity of the measurement light detected by the PSD 3, The severity is detected, and then the ethanol concentration is calculated with reference to data on the relationship between the received light amount of PSD 3 and the ethanol concentration at the detected gasoline severity.

  According to the configuration of the fuel property sensor 1 according to the embodiment of the present invention described above, the light-emitting diode 2 and the PSD 3 which are a pair of detection means are provided, and the received light amount of the PSD 3 and the measurement light decrease at the time of fuel transmission. The ethanol concentration was detected from the correlation between the degree and the alcohol concentration, and the gasoline gravity was detected from the correlation between the light intensity gravity center position in PSD3 and the gasoline severity and the total reflection angle. Thereby, the heavyness and ethanol concentration of gasoline, which are two types of property data related to the fuel F, can be detected with high accuracy by using the light emitting diode 2 and PSD 3 which are a set of detection means.

  Since the conventional fuel property detection device is provided with two detection means for detecting the severity of gasoline and for detecting the alcohol concentration in gasoline, the body size is increased and signal processing of two systems must be performed. Therefore, the electric circuit for controlling the fuel property detecting device is complicated.

  On the other hand, according to the fuel property sensor 1 according to the embodiment of the present invention, two pieces of information on the gasoline heavyness and the alcohol concentration in the gasoline are obtained from the light emitting diode 2 and the PSD 3 as a set of detection means. Can be measured simultaneously. Therefore, it is possible to realize the fuel property sensor 1 capable of accurately detecting both the gasoline heavyness and the alcohol concentration contained in the gasoline, miniaturizing, and reducing the number of parts.

  Next, the fuel property detection operation according to a modification of the fuel property sensor 1 according to the embodiment of the present invention will be described. In this modified example, a microcomputer 9 is provided on the circuit board 6 as an electric circuit for performing lighting drive control of the light emitting diode 2, detection signal processing from the PSD 3, light incident position calculation processing, and the like, as shown in FIG. It is mounted on the base 6.

  As shown in the block diagram of FIG. 6, the microcomputer 9 includes a calculation unit 91. As shown in FIG. 6, the light emitting diode 2 is connected to the calculation means 91 so that the drive current can be detected, and the PSD 3 is connected so that the detection signal can be input. The production means 91 has a storage area 92. In the storage area 92, data as the first map, that is, data on the relationship between the refractive index of the fuel F and the reflectance at the reflecting surface 43 is stored in advance.

  Below, the fuel property detection process performed in the calculating means 91 is demonstrated based on the flowchart of FIG.

  When the ignition switch (switch) of the automobile 100 is turned on by the driver's operation, the fuel property sensor 1 starts operating, and the calculation means 91 of the microcomputer 9 starts the fuel property detection process. The computing unit 91 first performs initialization in step 201.

  Subsequently, in step 202, the calculation means 91 performs the received light amount measurement and the illuminance distribution (received light centroid) measurement of PSD3.

  Next, in step 203, the calculation means 91 calculates the refractive index of the fuel based on the light receiving gravity center position in the PSD 3 measured in step 202.

  Subsequently, in step 204, the calculation means 91 calculates the refractive index of the fuel calculated in step 203 and the first map stored in the storage area 92, that is, the refractive index of the fuel F and the reflectance on the reflecting surface 43. The reflectance of the reflecting surface 43 of the light guide 4 is calculated based on the relationship data.

  Next, in step 205, the calculation means 91 applies the reflection to the reflecting surface 43 based on the reflectance of the reflecting surface 43 of the light guide 4 calculated in step 204 and the received light amount of PSD 3 measured in step 202. The amount of incident light, that is, the amount of light after passing through the fuel F is calculated.

  Subsequently, in step 206, the calculation means 91 calculates the amount of light emitted from the light emitting diode 2, that is, the amount of light before passing through the fuel F, based on the drive current of the light emitting diode 2.

  Next, the calculation means 91 transmits the fuel F in step 207 based on the light amount after passing through the fuel F calculated in step 205 and the light amount before passing through the fuel F calculated in step 206. Calculate the rate.

  Subsequently, in step 208, the calculation unit 91 determines the fuel F, that is, the gasoline heaviness, based on the refractive index of the fuel F calculated in step 203.

  Next, in step 209, the calculation unit 91 determines the ethanol concentration of the fuel F based on the fuel F permeability calculated in step 207.

  The properties of the fuel F can be determined by the processing described above.

  Next, a fuel property detection operation according to another modification of the fuel property sensor 1 according to the embodiment of the present invention will be described. Other modification examples include a microcomputer 9 as an electric circuit for performing lighting drive control of the light emitting diode 2, detection signal processing from the PSD 3, light incident position calculation process, and the like, similarly to the above-described modification examples. In another modified example, the data stored in the storage unit 92 of the calculating unit 91 and the fuel property detection processing method executed in the calculating unit 91 are different from those in the above-described modified example. In another modification, the storage area 92 of the calculation means 91 stores the data as the second map, that is, the total received light amount of the PSD 3 when the refractive index of the fuel F and the transmittance of the fuel F are 100%. The relationship data is stored in advance.

  Below, the fuel property detection process performed in the calculating means 91 is demonstrated based on the flowchart of FIG.

  When the ignition switch (switch) of the automobile 100 is turned on by the driver's operation, the fuel property sensor 1 starts operating, and the calculation means 91 of the microcomputer 9 starts the fuel property detection process. The computing means 91 first performs initialization at step 211.

  Subsequently, in step 212, the calculation unit 91 performs the received light amount measurement and the illuminance distribution (received light center of gravity) of PSD3.

  Next, in step 213, the calculation means 91 calculates the refractive index of the fuel based on the light receiving barycenter position of the PSD 3 measured in step 212.

  Subsequently, in step 214, the calculation means 91 determines that the refractive index calculated in step 213 and the second map stored in the storage area 92, that is, the refractive index of the fuel F and the transmittance of the fuel F are 100%. The total received light amount of PSD3 when the transmittance of the fuel F is 100% is calculated based on the data of the relationship with the total received light amount of PSD3 when.

  Here, the total amount of light received by the PSD 3 when the transmittance of the fuel F is 100%, that is, the total amount of light received by the PSD 3 when the light emitted from the light emitting diode 2 is not in the middle of the optical path to the PSD 3. This is used as a reference light amount in the fuel F transmittance calculation process.

  Next, in step 215, the calculation means 91 is a reference that is the received light amount at PSD3 measured at step 212 and the total received light amount of PSD3 when the transmittance of fuel F calculated at step 214 is 100%. Based on the amount of light, the transmittance of the fuel F is calculated.

  Subsequently, in step 216, the calculation means 91 determines the severity of the fuel F, that is, the gasoline severity, based on the refractive index of the fuel F calculated in step 213.

  Next, in step 217, the calculation unit 91 determines the ethanol concentration of the fuel F based on the fuel F permeability calculated in step 215.

  The properties of the fuel F can be determined by the processing described above.

  In addition, in the fuel property sensor 1 according to the embodiment of the present invention described above, the modified example thereof, and the other modified examples, the light guide body 4 is formed of glass. Other materials such as a colorless and transparent resin material may be used as long as the materials are stable without being discolored or altered even when immersed in the target fuel F.

  Further, in the fuel property sensor 1 according to the embodiment of the present invention described above, the modified example and other modified examples, the one-dimensional PSD is adopted as the PSD 3, but instead, the two-dimensional PSD is used. Also good.

  Moreover, in the fuel property sensor 1 according to the embodiment of the present invention described above, the modified example thereof, and other modified examples employ the PSD 3 as the light receiving device, but the invention is not limited to the PSD 3, and the gasoline heavyness As long as it is possible to detect the change in the optical path of the measurement light caused by the change in the total reflection angle θA of the reflecting surface 43 in conjunction with the change in the other, another type of device may be used. As the light receiving device, for example, a plurality of photodiodes may be arranged adjacent to each other on a straight line.

  In each of the embodiments described above, the fuel property sensor 1 is attached to the fuel pipe 100 that supplies the fuel F in the fuel tank (not shown) to the engine (not shown). As long as the light guide 4 can be immersed in the fuel F, the installation place may be a place other than the fuel pipe 100. For example, it may be attached to a fuel rail or the like that is attached in the fuel tank or on the engine and supplies fuel to the injection valve of each cylinder.

  Moreover, in the fuel property sensor 1 according to the embodiment of the present invention described above, the modified example thereof, and other modified examples, the light emitting diode 2 having a central wavelength of emitted light in the vicinity of 1600 nm is used. However, the present invention is not limited to this, and when the detection target liquid is a liquid other than ethanol, the liquid is appropriately changed according to the type. That is, a light emitting diode of a type that emits light having a wavelength with a large difference between the transmittance in the liquid whose concentration is to be detected and the transmittance in gasoline may be selected. Furthermore, as long as the light source emits light having the wavelength described above, a light source of a type other than the light emitting diode may be used.

  Moreover, in the fuel property sensor 1 according to the embodiment of the present invention described above, the modified example thereof, and other modified examples, the fuel F is a mixed liquid of gasoline and ethanol. Also good. For example, a mixture of light oil and methanol, an emulsion of heavy oil and water, or the like may be used.

It is sectional drawing of the fuel property sensor 1 by one Embodiment of this invention. It is II arrow directional view in FIG. It is the III-III sectional view taken on the line in FIG. It is a schematic diagram explaining the optical path of the measurement light in the reflective surface 43, and the incident state to PSD3. It is sectional drawing of the modification of the fuel property sensor 1 by one Embodiment of this invention. 2 is a block diagram of a microcomputer 9. FIG. 6 is a flowchart of fuel property detection processing executed in the microcomputer 9; 6 is a flowchart of fuel property detection processing executed in the microcomputer 9;

Explanation of symbols

1 Fuel property sensor (Fuel property detection device)
2 Light emitting diode (light source)
3 PSD (light receiving device)
31 Detection surface 32 P layer 33, 34 Output electrode 35 N layer 36 Common electrode 37 I layer 4 Light guide 41 Outgoing surface 42 Incident surface 43 Reflecting surface 5 Holder 6 Circuit board 7 Housing 71 Communication hole 8 Cover 9 Microcomputer 91 Calculation Means 92 Storage means 100 Fuel piping 100a Boss part 101 Gasket F Fuel S Recessed part V, W Optical path X, Y Incident area Xg, Yg Light quantity center of gravity position θA1, θA2 Total reflection angle

Claims (10)

A light guide made of a translucent material disposed so that a part thereof is in close contact with the fuel;
A light source disposed so that light can be incident on the light guide;
A light receiving device arranged to be able to receive measurement light, which is light emitted from the light source traveling in the light guide, and
A fuel property detection device that receives the measurement light and detects the property of the fuel based on a detection signal output from the light receiving device,
The light guide includes an emission surface that is a surface from which the measurement light is emitted from the light guide into the fuel, and the measurement light that is opposed to the emission surface and is emitted from the emission surface and transmitted through the fuel. Comprises an incident surface that is incident on the light guide, and a reflective surface that is a surface that reflects the measurement light incident from the incident surface toward the light receiving device,
The fuel property detecting device, wherein a space between the exit surface and the entrance surface is filled with the fuel and the reflection surface is in close contact with the fuel. The measurement light is emitted from the light source and incident on a light guide, then passes through the fuel between the exit surface and the entrance surface, and then totally reflected by the reflection surface and enters the light receiving device.
The light receiving device can detect the total amount of received light and the illuminance distribution in the light receiving region,
2. The fuel property detection device according to claim 1, wherein the light receiving device is arranged so that the measurement light reflected by the reflecting surface can enter. 3.   3. The fuel property detection device according to claim 1, wherein the light receiving device is a PSD (Position Sensitive Detector).   3. The fuel property detection device according to claim 1, wherein the light receiving device is formed by arranging a plurality of phototransistors or photodiodes adjacent to each other on a straight line.   The fuel property detection device according to any one of claims 1 to 4, wherein the light source is a light emitting diode.   6. The fuel property detection device according to claim 1, wherein the fuel is a mixed liquid of different fuels, and the wavelength range of the measurement light is in the near infrared region. Computation means having storage means for preliminarily storing data on the relationship between the refractive index of the fuel and the reflectance at the reflecting surface as a first map;
7. The calculation unit according to claim 1, wherein the calculation unit calculates a refractive index of the fuel and a transmittance of the fuel based on a detection signal output from the light receiving device and the first map. The fuel property detection device according to any one of the above.   The calculating means calculates the refractive index of the fuel based on a detection signal from the light receiving device, and the reflective surface based on the refractive index calculated by the refractive index calculating means and the first map. A reflectance calculating means for calculating the reflectance in the light source; and a transmittance for calculating the transmittance of the fuel based on the reflectance calculated by the reflectance calculating means, the light receiving device, the detection signal, and the amount of light emitted from the light source. The fuel property detection device according to claim 7, further comprising a calculation unit. Computation means having storage means for preliminarily storing as a second map data on the relationship between the refractive index of the fuel and the total light reception amount of the light receiving device when the fuel transmittance is known;
7. The calculation unit according to claim 1, wherein the calculation unit calculates a refractive index of the fuel and a transmittance of the fuel based on a detection signal output from the light receiving device and the second map. The fuel property detection device according to any one of the above.   The calculating means includes a refractive index calculating means for calculating a refractive index of the fuel based on a detection signal from the light receiving device, a refractive index calculated by the refractive index calculating means, the second map, and the light receiving device. The fuel property detection device according to claim 9, further comprising: a transmittance calculation unit that calculates the transmittance of the fuel based on a detection signal.

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