JP2016217745A - Device for measuring fuel concentration - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide device for measuring a fuel concentration in which measurement errors are reduced and the device is miniaturized to facilitate the arrangement.SOLUTION: A device for measuring a fuel concentration irradiates a measuring optical path LP in a combustion chamber C of an internal combustion engine with a measuring light ML, and measures the fuel concentration of a combustion chamber C from the intensity of a signal light SL transmitting a measuring optical path LP, and includes a half-mirror 25a as a branching part for branching reference light RL from the measuring light ML before incident to the measuring optical path LP. The half-mirror 25a which is the branching part is arranged inside the internal combustion engine.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a fuel concentration measuring device for measuring a fuel concentration in a combustion chamber of an internal combustion engine.

  2. Description of the Related Art Conventionally, an apparatus for measuring a fuel concentration in a combustion chamber in an internal combustion engine such as an automobile engine is known (see Patent Documents 1 and 2 below). An engine fuel concentration measuring device described in Patent Document 1 guides measurement light having a specific wavelength to a measurement optical path inside a combustion chamber by a measurement light introduction optical path, and transmits measurement light transmitted through the measurement optical path by a measurement light extraction optical path to the combustion chamber. A light intensity detector outputs a signal corresponding to the intensity of the measurement light led to the outside and led to the outside of the combustion chamber.

  Further, the fuel concentration measuring device of Patent Document 1 blocks the derivation of the measurement light to the light intensity detector by the light blocking means. Then, the transmission measurement light intensity calculation means corrects the output signal of the light intensity detector when the measurement light is derived with the output signal of the light intensity detector when the measurement light is derived, and the measurement optical path The intensity of the measurement light that has passed through is calculated. Then, the fuel concentration calculation means calculates the fuel concentration of the air-fuel mixture in the measurement optical path based on the intensity of the measurement light incident on the measurement optical path and the intensity of the transmission measurement light calculated by the transmission measurement light intensity calculation means.

  According to Patent Document 1, the fuel concentration measurement device detects the drift amount of the light intensity detector when the measurement light is blocked by the light blocking means and corrects the intensity of the measurement light, thereby correcting the intensity of the detector. It is said that the fuel concentration in the combustion chamber, that is, the air-fuel ratio can be accurately measured regardless of drift. Similarly to the fuel concentration measurement device described in Patent Document 1, the engine fuel concentration measurement device described in Patent Document 2 includes a measurement light introduction optical path, a measurement light extraction optical path, and a light intensity detector. Yes.

  In the fuel concentration measuring device of Patent Document 2, the intensity of the measurement light detected at the crank angle at which no fuel is present in the measurement optical path is set to the reference intensity of the measurement light by the fuel concentration calculation means. The fuel concentration calculation means sets a reference intensity, and measures in the measurement optical path at the crank angle for measuring the fuel concentration based on the reference intensity and the intensity of the measurement light detected at the crank angle for measuring the fuel concentration. The light transmittance is calculated. Further, the fuel concentration calculation means calculates the fuel concentration of the mixer in the measurement optical path based on the calculated transmittance.

  Patent Document 2 describes that there is attenuation due to vibration or the like in the optical path from the measurement unit to the detector until it enters the measurement unit in addition to fuel, and attenuation due to contamination of optical system elements constituting the measurement optical path. . Further, even if the above-described attenuation is present in Patent Document 2, since these attenuations occur at the same ratio with respect to the light transmission intensity and the incident light intensity, they are canceled out in the division in the formula for calculating the light transmittance. It can be calculated accurately without being affected by these.

JP 2002-340800 JP JP 2003-014640 A

  In the fuel concentration measuring devices described in Patent Documents 1 and 2, a part of the light emitted from the light source (3) is branched and incident on the second detector (5) for output monitoring. ) Is provided in the middle of the optical fiber (6) connecting the light source and the spark plug. As described above, when the beam splitter is provided outside the engine, it is not possible to accurately detect the light amount fluctuation caused by the vibration of the engine in the optical path inside the engine, and there is a possibility that the error of the measured fuel concentration becomes large. . Moreover, there exists a subject that an apparatus will enlarge and handling will become difficult.

  The present invention has been made in view of the above problems, and irradiates measurement light to a measurement optical path of a combustion chamber of an internal combustion engine, and measures the fuel concentration in the combustion chamber from the intensity of signal light transmitted through the measurement optical path. An object of the fuel concentration measuring device is to reduce measurement errors and reduce the size of the device to facilitate handling.

  In order to achieve the above object, the fuel concentration measuring device of the present invention irradiates the measurement light path of the combustion chamber of the internal combustion engine with the measurement light, and measures the fuel concentration in the combustion chamber from the intensity of the signal light transmitted through the measurement light path. A fuel concentration measuring apparatus comprising: a branching portion for branching reference light from the measurement light before entering the measurement optical path, wherein the branching portion is disposed inside the internal combustion engine. .

  The fuel concentration measuring apparatus according to the present invention is an apparatus that irradiates measurement light to a measurement optical path of a combustion chamber of an internal combustion engine and measures the fuel concentration in the combustion chamber from the intensity of signal light transmitted through the measurement optical path. More specifically, the fuel concentration measuring apparatus of the present invention branches the reference light from the measurement light before entering the measurement optical path inside the combustion chamber by the branching unit, and the intensity of the reference light and the intensity of the signal light Based on the above, the fuel concentration in the combustion chamber is measured.

  If the concentration of the fuel contained in the air in the combustion chamber is high, the attenuation of the measurement light incident on the measurement optical path of the combustion chamber increases, and the intensity of the signal light transmitted through the measurement optical path decreases. On the other hand, if the concentration of the fuel contained in the air in the combustion chamber is low, the attenuation of the measurement light incident on the measurement optical path of the combustion chamber decreases and the intensity of the signal light transmitted through the measurement optical path increases. Therefore, the fuel concentration in the combustion chamber can be measured based on the intensity of the reference light branched from the measurement light before entering the measurement optical path of the combustion chamber and the intensity of the signal light transmitted through the measurement optical path.

  The fuel concentration measuring devices described in Patent Documents 1 and 2 described above can measure the fuel concentration in the combustion chamber, similarly to the fuel concentration measuring device of the present invention. However, in these conventional fuel concentration measuring apparatuses, a beam splitter is provided outside the engine to split a part of the light emitted from the light source and to enter the second detector for monitoring the output. For this reason, in the optical path inside the engine, fluctuations in the amount of light caused by engine vibration or the like cannot be accurately detected, and there is a risk that fuel concentration measurement errors will increase. Moreover, there exists a subject that an apparatus will enlarge and handling will become difficult.

  On the other hand, in the fuel concentration measuring device of the present invention, a branching portion for branching the reference light from the measuring light is arranged inside the internal combustion engine. Therefore, according to the fuel concentration measuring apparatus of the present invention, it is possible to accurately detect the light amount fluctuation caused by the vibration of the engine or the like in the optical path inside the internal combustion engine and reduce the fuel concentration measurement error. Further, the fuel concentration measuring device can be reduced in size, and the handling of the device can be facilitated.

  Further, the fuel concentration measuring apparatus of the present invention includes a reference light measurement unit that measures the intensity of the reference light, a signal light measurement unit that measures the intensity of the signal light, the intensity of the reference light, and the intensity of the signal light. And a calculation unit for calculating the fuel concentration based on the above. Thereby, the intensity of the reference light is measured by the reference light measuring unit, the intensity of the signal light is measured by the signal light measuring unit, and the fuel concentration in the combustion chamber is calculated by the arithmetic unit based on the intensity of the reference light and the signal light. Can be calculated.

  The fuel concentration measuring device of the present invention includes a light source that irradiates the measurement light, a light transmission path that transmits the measurement light from the light source to the branching unit, and the signal from the measurement light path to the signal light measurement unit. A signal light transmission path for transmitting light. As a result, the measurement light can be irradiated from the light source, the measurement light can be transmitted from the light source to the branch portion by the light transmission path, and the measurement light having the reference light branched by the branch portion can be irradiated to the measurement light path of the combustion chamber. Further, the signal light transmitted through the measurement optical path of the combustion chamber can be transmitted from the measurement optical path to the signal light measurement unit through the signal light transmission path, and the intensity of the signal light can be measured.

  In addition, the fuel concentration measuring device of the present invention can include a reference light transmission path for transmitting the reference light from the branching unit to the reference light measuring unit. In this case, the reference light branched from the measurement light by the branching unit can be transmitted from the branching unit to the reference light measuring unit through the reference light transmission path, and the intensity of the reference light can be measured.

  Moreover, the fuel concentration measuring apparatus of this invention can be equipped with a glass mirror between the said light source and the said light transmission path instead of the said reference light transmission path. In this case, the glass mirror transmits all of the measurement light incident on the light transmission path from the light source, transmits a part of the reference light branched from the light branching path and exiting the light transmission path, and remains. Can be reflected so as to be incident on the reference light measurement unit. As a result, the measurement light is emitted from the light source, is transmitted through the glass mirror, is incident on the light transmission path, the reference light is branched by the internal branching portion of the internal combustion engine, and the remaining measurement light is irradiated on the measurement optical path of the combustion chamber. can do. Further, the reference light branched by the branching portion is led out of the internal combustion engine by a light transmission path through a path opposite to the measurement light, and the reference light emitted from the light transmission path is reflected by the glass mirror to be referred to as the reference light measuring section. The intensity of the reference light can be measured.

  Further, in the fuel concentration measuring device of the present invention, the branch portion may be provided at a combustion chamber side tip portion of a spark plug provided in the internal combustion engine. As a result, the branch portion can be arranged inside the internal combustion engine by using the plug hole that the internal combustion engine normally has, and a measurement optical path is provided at the tip of the spark plug so that the discharge gap at the tip of the spark plug can be reduced. The fuel concentration in the vicinity can be measured.

  As can be understood from the above description, according to the fuel concentration measuring apparatus of the present invention, it is possible to accurately detect the light amount fluctuation occurring outside the combustion chamber inside the internal combustion engine and reduce the fuel concentration measurement error. Further, the fuel concentration measuring device can be reduced in size, and the handling of the device can be facilitated.

1 is a schematic configuration diagram of a fuel concentration measurement device according to Embodiment 1 of the present invention. 1 is a schematic configuration diagram of a fuel concentration measurement device according to Embodiment 1 of the present invention. The expanded sectional view which shows schematic structure of the ignition plug shown to FIG. 1B. The expanded sectional view which shows schematic structure of the signal light acquisition part of the ignition plug shown in FIG. The schematic block diagram of the fuel concentration measuring apparatus which concerns on Embodiment 2 of this invention. The expanded sectional view which shows schematic structure of the signal light acquisition part which concerns on Embodiment 2 of this invention. The expanded sectional view which shows the modification of the signal light acquisition part shown in FIG.

  Embodiments of a fuel concentration measuring apparatus according to the present invention will be described below with reference to the drawings.

[Embodiment 1]
1A and 1B are schematic configuration diagrams of a fuel concentration measurement apparatus 100 according to Embodiment 1 of the present invention. FIG. 2 is a schematic enlarged cross-sectional view showing a schematic configuration of the ignition plug 10 shown in FIG. 1B. FIG. 3 is a schematic enlarged cross-sectional view showing a schematic configuration of the signal light acquisition unit 25 provided at the tip of the ignition plug 10 shown in FIG.

  The fuel concentration measuring apparatus 100 of this embodiment irradiates the measurement light path LP inside the combustion chamber C of the internal combustion engine E such as an automobile engine, and the intensity of the signal light SL transmitted through the measurement light path LP. This is an apparatus for measuring the fuel concentration in the combustion chamber C. As will be described in detail later, the fuel concentration measurement apparatus 100 of the present embodiment includes a half mirror 25a (see FIG. 3) as a branching part that branches the reference light RL from the measurement light ML before entering the measurement optical path LP. The greatest feature is that the mirror 25a is arranged inside the internal combustion engine E.

  The fuel concentration measuring apparatus 100 includes a light source 1 that irradiates the measurement light ML, an optical fiber 2 that forms a light transmission path that transmits the measurement light ML, and an optical fiber 3 that forms a signal light transmission path that transmits the signal light SL. And an optical fiber 4 that is a reference light transmission path for transmitting the reference light RL. A bundle fiber 5 is configured by bundling the optical fibers 2, 3 and 4.

  The light source 1 emits, as the measurement light ML, light having a predetermined wavelength that is absorbed by the fuel vapor in the combustion chamber C and attenuates in intensity, such as light having a medium red line wavelength of about 3.39 μm. . The optical fiber 2 constituting the light transmission path has a light receiving portion 2a that receives the measurement light ML from the light source 1 at the end on the light source 1 side. Between the light receiving unit 2 a of the optical fiber 2 and the light source 1, a lens 6 that collects the measurement light ML emitted from the light source 1 on the light receiving unit 2 a is installed.

  The fuel concentration measurement apparatus 100 further includes a reference light measurement unit 8 that measures the intensity of the reference light RL, and a signal light measurement unit 7 that measures the intensity of the signal light SL. The reference light measurement unit 8 is connected to one end of an optical fiber 4 that is a reference light transmission path drawn from the inside of the internal combustion engine E to the outside. The signal light measuring unit 7 is connected to one end of an optical fiber 3 that is a signal light transmission path drawn from the inside of the internal combustion engine E to the outside.

  The optical fiber 2 constituting the light transmission path transmits the measurement light ML from the light source 1 to the optical fiber 23a constituting the light transmission path in the ignition plug 10 provided in the internal combustion engine E. The optical fiber 3 constituting the signal light transmission path transmits the signal light SL from the optical fiber 23 b constituting the signal light transmission path in the ignition plug 10 to the signal light measuring unit 7. The optical fiber 4 serving as the reference light transmission path transmits the reference light RL from the optical fiber 23 c constituting the reference light transmission path in the ignition plug 10 to the reference light measurement unit 8.

  The fuel concentration measuring apparatus 100 calculates the fuel concentration in the combustion chamber C based on the intensity of the signal light SL measured by the signal light measuring unit 7 and the intensity of the reference light RL measured by the reference light measuring unit 8. A unit 9 is further provided. The calculation unit 9 is configured by electronic components such as a CPU and a memory, for example, and performs various calculations and controls the light source 1, the signal light measurement unit 7, the reference light measurement unit 8, and the like.

  The internal combustion engine E includes a spark plug 10 that is provided with a plug hole PH in the cylinder head SH and is inserted into the plug hole PH and fixed to the cylinder head SH with a screw. The spark plug 10 includes a housing 20 and a spark plug component 30 supported by the housing 20. The housing 20 is screwed to the plug hole PH of the cylinder head SH.

  The spark plug component 30 is mainly composed of an electrode member 31, an insulator 32, and a fixing nut 33. The electrode member 31 can be made of a highly conductive metal material such as a nickel alloy, and copper can be used for the core portion in order to improve thermal conductivity. The electrode member 31 is provided with a terminal portion 31a at a proximal end portion and a center electrode 31b at a distal end portion. The electrode member 31 is covered with an insulator 32, which is an insulator, except for the center electrode 31b at the tip, and is enclosed in the center of the spark plug component 30.

  A terminal portion 31a at the base end portion of the electrode member 31 is connected to a high voltage terminal 34a of a high voltage cable 34 connected to an external ignition coil. The center electrode 31b at the tip of the electrode member 31 is further provided with a tip 31c made of a rare metal such as platinum or iridium at the tip. The tip 31c of the center electrode 31b is opposed to the ground electrode 26 provided in the housing 20 with a predetermined discharge gap G. In the spark plug component 30, the gasket 35 is disposed between the center electrode 31b of the electrode member 31 and the housing 20, and the insulator 32 is insulated from the housing 20 by the gasket 35 and the insulator 32. Are fixed to the support portion 21 of the housing 20 by fixing nuts 33 arranged around the periphery of the housing 20.

  The housing 20 includes a support portion 21 that supports the spark plug constituting portion 30, a connector portion 22 that connects the connector portion 5 a of the bundle fiber 5 on the light source 1 side, and a guide hole 24 through which the bundle fiber 23 is inserted. Yes. In addition, the housing 20 injects a buffer material into the signal light acquisition unit 25 that receives the signal light SL that irradiates the measurement light path LP with the measurement light ML and transmits the measurement light path LP, the ground electrode 26, and the guide hole 24. And a plurality of injection holes 27. The ground electrode 26 is made of nickel steel, for example, and is welded to the tip of the housing 20. The injection hole 27 is used to inject a buffer into the guide hole 24. The buffer injected into the guide hole 24 relaxes vibration between the bundle fiber 23 inserted through the guide hole 24 and the housing 20.

  The support portion 21 of the housing 20 is formed in a cylindrical shape into which the spark plug component 30 can be inserted, and has a screw portion 21 a into which the fixing nut 33 of the spark plug component 30 is screwed. The support portion 21 is disposed between the tip tip 31c of the spark plug component 30 and the ground electrode 26 of the housing 20 in a state where the gasket 35 is disposed between the center electrode 31b of the spark plug component 30 and the support portion 21. In addition, the spark plug component 30 is supported with a predetermined discharge gap G.

  A connector portion 22 of a bundle fiber 23 that passes through the guide hole 24 is fitted and fixed to an end portion of the housing 20. The guide hole 24 penetrates the housing 20 in the longitudinal axis direction and allows the bundle fiber 23 to pass therethrough. One end of the bundle fiber 23 inserted into the guide hole 24 is connected to the connector portion 22 of the housing 20, and the other end reaches the signal light acquisition portion 25 of the housing 20.

  The connector part 22 of the bundle fiber 23 passing through the guide hole 24 is provided at the end of the bundle fiber 5 in which the optical fibers 2, 3 and 4 from the light source 1, the signal light measurement part 7 and the reference light measurement part 8 are bundled. It is connected to the connector part 5a. Thereby, each optical fiber 23a, 23b, 23c which comprises the bundle fiber 23 which passes along the guide hole 24 is the light source 1 which comprises a light transmission path | route, a signal light transmission path | route, and a reference light transmission path | route, and a signal light measurement part, respectively. 7 and the optical fibers 2, 3 and 4 from the reference light measuring unit 8, and constitutes a part of each optical transmission path.

  The signal light acquisition unit 25 is provided facing the discharge gap G between the tip tip 31 c that is an electrode discharge portion of the spark plug component 30 and the ground electrode 26. The signal light acquisition unit 25 transmits a part of the measurement light ML from the light transmission path and reflects the rest as reference light RL, and a mirror 25b that reflects the reference light RL reflected by the half mirror 25a. And a lens 25c that collects the measurement light ML that has passed through the half mirror 25a, and a window portion 25d that isolates the measurement light ML from the combustion chamber C. Unlike the glass mirror that transmits all the light incident from one side, the half mirror 25a transmits a part of the light incident from one side and reflects the rest. The half mirror 25a and the mirror 25b may be a mirror surface made of a film bonded to the end faces of the optical fibers 23a and 23c, or may be a solid mirror surface which is a member different from the optical fibers 23a and 23c.

  Further, the signal light acquisition unit 25 includes a gap forming unit 25e that forms a measurement gap g for obtaining the signal light SL in the combustion chamber C, and a concave mirror 25f provided in the gap forming unit 25e. ing. The gap forming portion 25e is provided at the front end of the housing 20 so as to face the window portion 25d with a predetermined interval, supports the concave mirror 25f on the surface facing the window portion 25d, and the window portion 25d and the concave mirror 25f. A measurement gap g with a predetermined interval is formed between the two.

  The bundle fiber 23 passing through the guide hole 24 is positioned with respect to the signal light acquisition unit 25 by fitting the connector portion 22 to the end portion of the housing 20, and a predetermined gap S is formed between the bundle fiber 23 and the window portion 25d. Arranged. The half mirror 25a, the mirror 25b, and the lens 25c are disposed in the gap S between the end portion of the bundle fiber 23 and the window portion 25d.

  Further, by fitting the connector portion 22 of the bundle fiber 23 passing through the guide hole 24 to the end portion of the housing 20, the end portion of the optical fiber 23a constituting the light transmission path is incident on the half mirror 25a with the measurement light ML. So as to be adjacent to the half mirror 25a. Further, the end of the optical fiber 23b constituting the signal light transmission path is disposed at a position where the signal light SL transmitted through the lens 25c is incident. Further, the end of the optical fiber 23c constituting the reference light transmission path is arranged adjacent to the mirror 25b so that the reference light RL reflected by the mirror 25b is incident.

  The half mirror 25a is disposed adjacent to the end of the optical fiber 23a constituting the light transmission path, and has a measurement light incident surface F1 on which the measurement light ML transmitted through the light transmission path is incident. The measurement light incident surface F1 is inclined at a predetermined angle with respect to the incident direction of the measurement light ML, transmits a part of the measurement light ML incident through the optical fiber 23a, and the remaining mirror as an adjacent reference light RL. Reflected toward 25b.

  The mirror 25b is disposed adjacent to the end of the optical fiber 23c constituting the reference light transmission path, and has a reference light incident surface F2 on which the reference light RL reflected by the half mirror 25a is incident. The reference light incident surface F2 is inclined at a predetermined angle with respect to the incident direction of the reference light RL, and is opposed to the measurement light incident surface F1 of the half mirror 25a at an angle of approximately 90 °. The mirror 25b reflects the reference light RL incident on the reference light incident surface F2 and makes it incident on the optical fiber 23c constituting the reference light path.

  The lens 25c condenses the measurement light ML so that the measurement light ML transmitted through the half mirror 25a passes through the window portion 25d and the measurement gap g and enters the concave mirror 25f. Further, the lens 25c receives the signal light SL obtained by the measurement light ML irradiated to the measurement gap g from the window portion 25d passing through the measurement gap g, reflected by the concave mirror 25f, and again transmitted through the measurement gap g. The light is incident on the optical fiber 23b constituting the signal light transmission path. That is, the measurement gap g between the window portion 25d and the gap forming portion 25e, more specifically, the measurement gap g between the window portion 25d and the concave mirror 25f transmits the measurement light ML and transmits the signal light SL. It becomes the measurement optical path LP of the combustion chamber C to obtain.

  The window portion 25d is provided at a position facing the gap forming portion 25e and facing the measurement gap g, and seals the half mirror 25a, the mirror 25b, the lens 25c, the bundle fiber 23, and the like inside the housing 20, The structure is isolated from the combustion chamber C. The window portion 25d can be made of a transparent material that transmits the measurement light ML and the signal light SL, such as sapphire glass having high heat resistance.

  As described above, the fuel concentration measuring apparatus 100 according to the present embodiment irradiates the measurement light ML to the measurement optical path LP of the combustion chamber C of the internal combustion engine E, and determines the intensity of the signal light SL transmitted through the measurement optical path LP. It is an apparatus for measuring the fuel concentration in the combustion chamber C. The fuel concentration measuring apparatus 100 includes a half mirror 25a as a branching part for branching the reference light RL from the measurement light ML before entering the measurement optical path LP, and the half mirror 25a as the branching part is disposed inside the internal combustion engine E. Has been.

  In addition, the fuel concentration measurement apparatus 100 according to the present embodiment includes a reference light measurement unit 8 that measures the intensity of the reference light RL, a signal light measurement unit 7 that measures the intensity of the signal light SL, and the intensity and signal of the reference light RL. And an arithmetic unit 9 that calculates the fuel concentration based on the intensity of the light SL.

  Further, the fuel concentration measuring apparatus 100 of the present embodiment includes a light source 1 that irradiates the measurement light ML, and an optical fiber 2 that serves as a light transmission path for transmitting the measurement light ML from the light source 1 to the half mirror 25a serving as a branching unit. , And an optical fiber 3 as a signal light transmission path for transmitting the signal light SL from the measurement light path LP to the signal light measurement unit 7.

  In addition, the fuel concentration measurement device 100 of the present embodiment includes an optical fiber 4 as a reference light transmission path for transmitting the reference light RL from the half mirror 25a that is a branching portion to the reference light measurement unit 8.

  Furthermore, the half mirror 25a which is a branching portion is provided at the front end portion of the ignition plug 10 provided in the internal combustion engine E on the combustion chamber C side.

  Hereinafter, the operation of the fuel concentration measuring apparatus 100 of the present embodiment having the above configuration will be described.

  In order to measure the fuel concentration in the combustion chamber C of the internal combustion engine E by the fuel concentration measuring device 100, for example, the measurement light ML is emitted from the light source 1 under the control of the calculation unit 9. The measurement light ML emitted from the light source 1 is incident on the lens 6 and collected, and then enters the light receiving portion 2a of the optical fiber 2 constituting the light transmission path. The measurement light ML incident on the light receiving portion 2a passes through the optical fiber 2 constituting the light transmission path, reaches the connector portion 5a of the bundle fiber 5, and passes through the connector portion 22 to guide holes 24 in the housing 20 of the spark plug 10. Is incident on an optical fiber 23a that constitutes a light transmission path passing through.

  The measurement light ML incident on the optical fiber 23a of the spark plug through the connector part 22 passes through the optical fiber 23a, exits from the end of the optical fiber 23a opposite to the connector part 22, and is half of the signal light acquisition part 25. The light enters the measurement light incident surface F1 of the mirror 25a. Part of the measurement light ML incident on the measurement light incident surface F1 of the half mirror 25a is reflected by the measurement light incident surface F1 of the half mirror 25a, is incident on the reference light incident surface F2 of the mirror 25b, is reflected again, and is ignited. The light enters the optical fiber 23c constituting the reference light transmission path passing through the guide hole 24 of the housing 20 of the plug 10 as the reference light RL. The remaining part of the measurement light ML incident on the measurement light incident surface F1 of the half mirror 25a is transmitted through the half mirror 25a and incident on the lens 25c.

  The measurement light ML incident on the lens 25c is collected by the lens 25c, passes through the window portion 25d, and is applied to the measurement gap g as the measurement optical path LP. The measurement light ML that has passed through the window portion 25d and has been irradiated onto the measurement optical path LP passes through the measurement gap g, enters the concave mirror 25f, is reflected by the concave mirror 25f, and passes through the measurement gap g again. The signal light SL transmitted through the LP enters the window 25d.

  The measurement light ML incident on the measurement optical path LP is absorbed by the fuel vapor existing in the measurement optical path LP at an absorptance corresponding to the fuel concentration in the process of passing through the measurement optical path LP. Therefore, by irradiating the measurement light path LP with the measurement light ML and acquiring the signal light SL transmitted through the measurement light path LP, the signal light SL having an intensity corresponding to the concentration of fuel present in the measurement light path LP can be acquired. it can.

  The signal light SL that has passed through the measurement optical path LP and entered the window 25d passes through the window 25d and enters the lens 25c. The signal light SL that has entered the lens 25 c passes through the lens 25 c and enters the optical fiber 23 b that forms the signal light transmission path of the spark plug 10. In addition, by using the concave mirror 25f, it is possible to prevent the signal light SL from entering the half mirror 25a. Further, the S / N ratio of the signal light SL can be improved by the concave mirror 25f and the lens 25c.

  The signal light SL incident on the optical fiber 23b constituting the signal light transmission path of the spark plug 10 passes through the connector portion 22 of the bundle fiber 23 of the spark plug 10 and the connector portion 5a of the bundle fiber 5 on the light source 1 side. The light enters the optical fiber 3 constituting the signal light transmission path connected to the optical measurement unit 7 and reaches the signal light measurement unit 7. For example, the signal light measurement unit 7 measures the intensity of the signal light SL under the control of the calculation unit 9.

  On the other hand, the reference light RL is reflected by the measurement light incident surface F1 of the half mirror 25a, is further reflected by the reference light incident surface F2 of the mirror 25b, and passes through the reference light transmission path passing through the guide hole 24 of the housing 20 of the spark plug 10. The light enters the constituent optical fiber 23c. The reference light RL constitutes a reference light transmission path connected to the reference light measurement unit 8 via the connector part 22 of the bundle fiber 23 of the spark plug 10 and the connector part 5a of the bundle fiber 5 on the light source 1 side. The light enters the optical fiber 4 and reaches the reference light measurement unit 8. The reference light measurement unit 8 measures the intensity of the reference light RL, for example, under the control of the calculation unit 9.

  The calculation unit 9 calculates the fuel concentration in the combustion chamber C based on the intensity of the signal light SL measured by the signal light measurement unit 7 and the intensity of the reference light RL measured by the reference light measurement unit 8. For example, when the intensity of the signal light SL is A and the intensity of the reference light RL is B, the transmittance of the measurement light ML can be obtained as transmittance (%) = (A / B) × 100. For example, the calculation unit 9 calculates the transmittance of the measurement light ML, converts the transmittance to the fuel concentration based on the relationship between the transmittance stored in advance and the fuel concentration, and calculates the fuel concentration in the combustion chamber C. can do.

  Here, in the fuel concentration measuring apparatus 100 of the present embodiment, the half mirror 25a serving as a branching portion for branching the reference light RL from the measurement light ML before entering the measurement light path LP of the combustion chamber C includes the combustion of the spark plug 10. It is provided at the front end of the chamber C side. Thereby, the half mirror 25a is arrange | positioned inside the internal combustion engine E through the plug hole PH. Therefore, according to the fuel concentration measuring apparatus 100 of the present embodiment, in the optical path inside the internal combustion engine E, the light quantity fluctuation caused by the vibration of the internal combustion engine E such as the engine is accurately detected, and the light quantity fluctuation is compensated. Thus, the measurement error of the fuel concentration can be reduced as compared with the conventional case. Further, by arranging the half mirror 25a for branching the reference light RL inside the internal combustion engine E, the fuel concentration measuring device 100 can be reduced in size, and the handling of the device can be facilitated.

  Further, the fuel concentration measuring apparatus 100 of the present embodiment includes optical fibers 4 and 23c as reference light transmission paths for transmitting the reference light RL from the half mirror 25a that is a branching portion to the reference light measuring unit 8. As a result, the reference light RL branched from the measurement light ML by the half mirror 25a is transmitted from the half mirror 25a, which is the branching portion, to the reference light measuring unit 8 by the optical fibers 4 and 23c, which are the reference light transmission paths, and the reference light. The strength of RL can be measured. Therefore, it is not necessary to arrange a half mirror that reflects the reference light RL outside the fuel concentration measuring apparatus 100, the fuel concentration measuring apparatus 100 can be further downsized, and the handling of the apparatus can be facilitated. .

[Embodiment 2]
Next, a fuel concentration measuring apparatus 100A according to Embodiment 2 of the present invention will be described with reference to FIGS. 4 and 5 with reference to FIGS. 1B and 2. FIG. 4 is a schematic configuration diagram of a fuel concentration measuring apparatus 100A according to the second embodiment corresponding to FIG. 1A of the first embodiment. FIG. 5 is a schematic cross-sectional view illustrating a schematic configuration of the signal light acquisition unit 25A of the fuel concentration measurement device 100A according to the second embodiment corresponding to FIG. 3 of the first embodiment.

  The fuel concentration measuring device 100A of the present embodiment does not have the optical fibers 23c and 4 that transmit the reference light RL from the half mirror 25a that is a branching portion of the signal light acquiring unit 25A to the reference light measuring unit 8, the light source 1 and It differs from the fuel concentration measuring apparatus 100 described in the first embodiment in that the glass mirror 2b is provided between the optical fiber 2 serving as a light transmission path and the mirror 25b is not provided in the signal light acquisition unit 25. ing. Since the other points of the fuel concentration measuring apparatus 100A of the present embodiment are the same as those of the fuel concentration measuring apparatus 100 described in the first embodiment, the same parts are denoted by the same reference numerals and description thereof is omitted.

  The fuel concentration measuring apparatus 100A includes a glass mirror 2b between the light source 1 and the optical fiber 2 constituting the light transmission path. The glass mirror 2b transmits all the light incident from one side, transmits part of the light incident from the other side, and reflects the rest. The glass mirror 2b transmits all of the measurement light ML incident on the optical fiber 2 constituting the light transmission path from the light source 1, and is branched by the half mirror 25a of the signal light acquisition unit 25 that is a branching unit to exit the optical fiber 2. A part of the reference light RL is transmitted, and the rest is reflected so as to be incident on the reference light measurement unit 8. The half mirror 25a of the signal light acquisition unit 25A is provided on the end face of the optical fiber 23a constituting the light transmission path of the bundle fiber 23A of the spark plug 10, reflects a part of the measurement light ML as the reference light RL, and the remaining The measurement light ML is transmitted.

  As described above, the fuel concentration measuring apparatus 100A of the present embodiment includes the glass mirror 2b between the light source 1 and the optical fiber 2 serving as the light transmission path. Then, the glass mirror 2b transmits the measurement light ML incident on the optical fiber 2 which is a light transmission path from the light source 1, and is branched by the half mirror 25a of the signal light acquisition unit 25 which is a branching part. The reference light RL exiting the fiber 2 is reflected so as to enter the reference light measurement unit 8.

  Hereinafter, the operation of the fuel concentration measuring apparatus 100A of the present embodiment will be described.

  In order to measure the fuel concentration in the combustion chamber C of the internal combustion engine E by the fuel concentration measuring device 100A, for example, the measurement light ML is emitted from the light source 1 under the control of the calculation unit 9. The measurement light ML emitted from the light source 1 passes through the glass mirror 2b, enters the lens 6 and is collected, and enters the light receiving portion 2a of the optical fiber 2 constituting the light transmission path. The measurement light ML incident on the light receiving portion 2a passes through the optical fiber 2 constituting the light transmission path, reaches the connector portion 5a of the bundle fiber 5, and passes through the connector portion 22 to guide holes 24 in the housing 20 of the spark plug 10. Is incident on an optical fiber 23a that constitutes a light transmission path passing through.

  The measurement light ML that has entered the optical fiber 23a of the spark plug 10 through the connector portion 22 passes through the optical fiber 23a, exits from the end of the optical fiber 23a on the opposite side of the connector portion 22, and passes through the signal light acquisition portion 25. The light enters the measurement light incident surface F1 of the half mirror 25a. A part of the measurement light ML incident on the measurement light incident surface F1 of the half mirror 25a is reflected by the measurement light incident surface F1 of the half mirror 25a, and the optical fiber 23a constituting the light transmission path is directed in the direction opposite to the measurement light ML. To the reference light RL. The remaining part of the measurement light ML incident on the measurement light incident surface F1 of the half mirror 25a is transmitted through the half mirror 25a and incident on the lens 25c.

  The measurement light ML incident on the lens 25c is collected by the lens 25c, passes through the window portion 25d, and is applied to the measurement gap g as the measurement optical path LP. The measurement light ML that has passed through the window portion 25d and has been irradiated onto the measurement optical path LP passes through the measurement gap g, enters the concave mirror 25f, is reflected by the concave mirror 25f, and passes through the measurement gap g again. The signal light SL transmitted through the LP enters the window 25d.

  The measurement light ML incident on the measurement optical path LP is absorbed by the fuel vapor existing in the measurement optical path LP at an absorptance according to the fuel concentration in the process of passing through the measurement optical path LP. Therefore, by irradiating the measurement light path LP with the measurement light ML and acquiring the signal light SL transmitted through the measurement light path LP, the signal light SL having an intensity corresponding to the concentration of fuel present in the measurement light path LP can be acquired. it can.

  The signal light SL that has passed through the measurement optical path LP and entered the window 25d passes through the window 25d and enters the lens 25c. The signal light that has entered the lens 25 c passes through the lens 25 c and enters the optical fiber 23 b that forms the signal light transmission path of the spark plug 10. The signal light SL incident on the optical fiber 23b constituting the signal light transmission path of the spark plug 10 passes through the connector portion 22 of the bundle fiber 23A of the spark plug 10 and the connector portion 5a of the bundle fiber 5 on the light source 1 side. The light enters the optical fiber 3 constituting the signal light transmission path connected to the optical measurement unit 7 and reaches the signal light measurement unit 7. For example, the signal light measurement unit 7 measures the intensity of the signal light SL under the control of the calculation unit 9.

  On the other hand, the reference light RL is reflected by the measurement light incident surface F1 of the half mirror 25a, and returns to the opposite direction to the measurement light ML through the optical fiber 23a constituting the light transmission path. The reference light RL is incident on the optical fiber 2 constituting the light transmission path on the light source 1 side via the connector part 22 of the bundle fiber 23A of the spark plug 10 and the connector part 5a of the bundle fiber 5 on the light source 1 side. , Exits the optical fiber 2 and enters the lens 6.

  The reference light RL incident on the lens 6 is transmitted through the lens 6 and incident on the glass mirror 2b, a part thereof is transmitted through the glass mirror 2b, and the rest is reflected by the glass mirror 2b and incident on the reference light measuring unit 8. . For example, the reference light measurement unit 8 measures the intensity of the reference light RL under the control of the calculation unit 9. As in the first embodiment, the calculation unit 9 is based on the intensity of the signal light SL measured by the signal light measurement unit 7 and the intensity of the reference light RL measured by the reference light measurement unit 8. The fuel concentration is calculated.

  In the fuel concentration measurement device 100A of the present embodiment, the half mirror 25a as a branching portion for branching the reference light RL from the measurement light ML before entering the measurement optical path LP of the combustion chamber C is provided on the combustion chamber C side of the ignition plug 10. It is provided at the tip. Thereby, the half mirror 25a is arrange | positioned inside the internal combustion engine E through the plug hole PH. Therefore, according to the fuel concentration measuring apparatus 100A of the present embodiment, the light quantity fluctuation caused by the vibration of the internal combustion engine E or the like can be accurately detected in the optical path inside the internal combustion engine E, and the light quantity fluctuation can be compensated for. The measurement error of the fuel concentration can be reduced as compared with the conventional case. Further, by arranging the half mirror 25a for branching the reference light RL inside the internal combustion engine E, the fuel concentration measuring device 100A can be reduced in size, and the handling of the device can be facilitated.

  In the fuel concentration measuring apparatus 100A of the present embodiment, the configuration of the signal light acquisition unit 25A is not limited to the configuration shown in FIG. FIG. 6 shows a modification of the signal light acquisition unit 25A in the fuel concentration measurement apparatus 100A of the present embodiment. In this modification, the signal light acquisition unit 25B includes a deflection-independent optical isolator 25g on the opposite side of the half mirror 25a from the optical fiber 23a, and the gap forming unit 25e has a flat mirror 25h instead of the concave mirror 25f. Is provided. Thereby, it is possible to prevent the signal light SL reflected by the flat mirror 25h from entering the half mirror 25a. Therefore, according to the fuel concentration measurement apparatus having the signal light acquisition unit 25B of this modification, the same effect as that of the fuel concentration measurement apparatus 100A of Embodiment 2 can be obtained.

  The embodiment of the present invention has been described in detail with reference to the drawings, but the specific configuration is not limited to this embodiment, and there are design changes and the like without departing from the gist of the present invention. They are also included in the present invention. For example, a through hole other than the plug hole may be used to arrange the signal light acquisition unit having the branching unit inside the internal combustion engine. Further, the signal light acquisition unit having the branching unit may be provided separately from the spark plug.

1 Light source 2 Optical fiber (light transmission path)
2b Glass mirror 3 Optical fiber (signal light transmission path)
4 Optical fiber (reference light transmission path)
7 Signal light measurement unit 8 Reference light measurement unit 9 Calculation unit 10 Spark plug 23a Optical fiber (optical transmission path)
23b Optical fiber (signal light transmission path)
25a Half mirror (branch part)
100 Fuel Concentration Measuring Device 100A Fuel Concentration Measuring Device C Combustion Chamber E Internal Combustion Engine LP Measuring Optical Path ML Measuring Light PH Plug Hole RL Reference Light SL Signal Light

Claims (6)

A fuel concentration measuring device for irradiating measurement light to a measurement optical path of a combustion chamber of an internal combustion engine and measuring a fuel concentration in the combustion chamber from the intensity of signal light transmitted through the measurement optical path,
A branching portion for branching reference light from the measurement light before entering the measurement optical path;
The fuel concentration measuring device according to claim 1, wherein the branch portion is disposed inside the internal combustion engine.   A reference light measurement unit that measures the intensity of the reference light, a signal light measurement unit that measures the intensity of the signal light, and an operation that calculates the fuel concentration based on the intensity of the reference light and the intensity of the signal light The fuel concentration measuring device according to claim 1, further comprising a unit.   A light source that irradiates the measurement light, a light transmission path that transmits the measurement light from the light source to the branching unit, and a signal light transmission path that transmits the signal light from the measurement light path to the signal light measurement unit. The fuel concentration measuring device according to claim 2, further comprising:   The fuel concentration measuring device according to claim 3, further comprising a reference light transmission path for transmitting the reference light from the branching unit to the reference light measuring unit. A glass mirror is provided between the light source and the light transmission path,
The glass mirror transmits the measurement light incident on the light transmission path from the light source, reflects the reference light branched at the branching section and exiting the light transmission path, and enters the reference light measurement section. The fuel concentration measuring device according to claim 3, wherein the fuel concentration measuring device is provided as described above.   The fuel concentration measuring device according to any one of claims 1 to 5, wherein the branch portion is provided at a combustion chamber side tip of an ignition plug provided in the internal combustion engine.

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