JP6631041B2 - Oxygen concentration measurement device - Google Patents

Description

  The present invention relates to an oxygen concentration measuring device that optically measures an oxygen concentration in a measurement target area, and particularly to an oxygen concentration measurement that can be suitably used for measuring an oxygen gas concentration in an oxygen gas flow path inside a fuel cell. Equipment related.

  A fuel cell is a device that generates power using an electrochemical reaction between hydrogen supplied to a negative electrode side and oxygen supplied to a positive electrode side. In recent years, it has various advantages such as not generating harmful substances such as carbon dioxide and nitrogen oxides during power generation, high power generation efficiency and energy use efficiency, and being able to easily obtain hydrogen as fuel. It is used in various fields.

  In a fuel cell, a current flows when electrons released from hydrogen on the negative electrode side move to the positive electrode side through an external circuit. In addition, hydrogen ions generated as a result of the release of electrons from hydrogen move in the electrolyte toward the positive electrode, and react with oxygen (oxygen ions) that have received the electrons on the positive electrode to become water. Therefore, the state of oxygen consumption on the positive electrode side reflects the state of power generation, and evaluating this is necessary to improve battery performance by improving the structure of the battery, the type of electrolyte membrane and catalyst, the power generation conditions, and the like. It is effective for

  The applicant of the present application has proposed a device (oxygen concentration measuring device) for optically measuring the oxygen gas concentration in a fuel cell in Patent Document 1 and Non-Patent Document 1. In this oxygen concentration measurement device, an oxygen-sensitive substance whose fluorescence intensity changes according to the oxygen concentration is applied in advance to an oxygen gas flow path provided in contact with the positive electrode of the fuel cell, and a predetermined amount is applied to the oxygen-sensitive substance through a light transmission window. By irradiating with excitation light of a wavelength, the fluorescence intensity emitted from the oxygen-sensitive substance is detected. The oxygen-sensitive substance emits fluorescence having an intensity corresponding to the oxygen concentration, and the oxygen gas concentration in the oxygen gas flow path can be obtained from the fluorescence intensity of the oxygen-sensitive substance.

  FIG. 1 shows a main configuration of an oxygen concentration measuring apparatus 100 described in Patent Document 1. In the oxygen concentration measuring device 100, light (excitation light) emitted from a light source 101 at a predetermined spread angle is converted into parallel light by a collimating lens 102, reflected by a total reflection mirror 103 and a dichroic mirror 104, The oxygen gas flow path 105 is irradiated. The collimating lens 102 is movable in the optical axis direction of the excitation light. By moving the collimating lens 102, the excitation light can be irradiated with an area corresponding to the size of the oxygen gas flow path in the visualization cell 105. Can be. Fluorescence from the oxygen-sensitive substance previously applied to the oxygen gas flow path 105 is detected by the photodetector 106.

JP 2011-89944 A

Takashi Ohno, et al., "Fuel Cell Oxygen Concentration Visualization System FC-O2 Monitor FCM-405-Oxy Type", Shimadzu Review, Vol. 67, No. 1-2 (2010)

  Usually, the measurement of the oxygen concentration is performed in a dark room where external light is blocked. However, in the above-described oxygen concentration measuring apparatus 100, optical elements such as a collimator lens 102, a total reflection mirror 103, and a dichroic mirror 104 are arranged on an optical path from a light source 101 to an oxygen gas flow path. Therefore, even if the external light is blocked, a part of the excitation light emitted from the light source is scattered by the optical element such as the collimator lens 102 and becomes stray light. When such stray light enters the photodetector 106, there is a problem that the measurement result of the fluorescence intensity becomes inaccurate and the measurement accuracy of the oxygen gas concentration deteriorates.

  The problem to be solved by the present invention is to improve the accuracy of measurement in an oxygen concentration measurement device that measures an oxygen gas concentration in a measurement target space using an oxygen-sensitive substance that emits fluorescence having an intensity corresponding to the oxygen concentration. It is.

Means for Solving the Problems The present invention made in order to solve the above-mentioned problem provides an apparatus for measuring an oxygen gas concentration in the measurement target space by measuring a fluorescence intensity of an oxygen sensitive substance applied to a detection surface placed in the measurement target space. And
a) a light source that emits excitation light of a predetermined wavelength;
b) irradiating the excitation light on the detection surface, an irradiation optical system including an optical element,
a light incident surface which the fluorescence incident emitted from c) the oxygen sensitive material, one end opening in a direction facing the detection surface, the other end is in contact with the light incident surface, the fluorescent of the optical element A light detection unit having a cover member that is a tubular body that blocks a linear path connecting the optical element and the light incident surface, which is disposed outside a path incident on the light incident surface,
It is characterized by having.

  In the oxygen concentration measuring device according to the present invention, the excitation light is applied to the detection surface coated with the oxygen-sensitive substance through the irradiation optical system. Then, the intensity of the fluorescence of the oxygen-sensitive substance is detected by the light detection unit. At this time, since the cover member, which is a cylindrical body opened in the direction facing the detection surface, is attached to the light incident surface of the light detection unit, stray light generated by scattering by the optical element of the irradiation optical system is applied to the light detector. It is possible to prevent incidence. Therefore, the intensity of the fluorescence from the oxygen-sensitive substance can be accurately measured, and the oxygen gas concentration can be measured with high accuracy.

  The light detector may measure the total intensity of the fluorescence of the oxygen-sensitive substance, but is preferably an imaging device (camera). Thus, an image of the detection surface is obtained, and the distribution of the oxygen gas concentration in the measurement target space can be obtained from the distribution of the brightness (the distribution of the fluorescence intensity of the oxygen-sensitive substance) in the image. This configuration can be suitably used particularly for measuring the oxygen gas concentration in the oxygen gas flow path inside the fuel cell.

  There are fuel cells of various sizes according to applications and places of use, and the size of the detection surface also varies. In order to flexibly cope with such a detection surface, it is preferable that the irradiation optical system includes a collimating lens arranged so as to be movable in an optical axis direction of the excitation light. Thereby, the irradiation area of the excitation light can be changed according to the size of the detection surface.

  By using the oxygen concentration measuring device according to the present invention, it is possible to prevent stray light generated by scattering of the excitation light by the optical element included in the irradiation optical system from being incident on the light detection unit, and to prevent fluorescence from the oxygen-sensitive substance from being emitted. The intensity can be accurately measured, and the measurement accuracy of the oxygen gas concentration in the measurement target space can be improved.

FIG. 2 is a configuration diagram of a main part of a conventional oxygen concentration measurement device. FIG. 1 is a configuration diagram of a main part of an embodiment of an oxygen concentration measuring device according to the present invention. FIG. 4 is a configuration diagram of a main part of another embodiment of the oxygen concentration measuring device according to the present invention. FIG. 9 is a configuration diagram of a main part of still another embodiment of the oxygen concentration measurement device according to the present invention.

  An embodiment of the oxygen concentration measuring apparatus according to the present invention will be described below with reference to the drawings. The oxygen concentration measuring device 10 of the present embodiment is a device for measuring the oxygen gas concentration in the oxygen gas flow path inside the fuel cell. An oxygen-sensitive substance that absorbs light of about 400 nm and emits fluorescence of about 650 nm is applied in advance to the oxygen gas flow path (detection surface). The oxygen-sensitive substance is a substance such as platinum porphyrin that emits fluorescence having an intensity corresponding to the oxygen concentration (for example, the fluorescence is quenched by oxygen gas).

FIG. 2 is a main part configuration diagram of the oxygen concentration measuring device 10 of the present embodiment.
The oxygen concentration measuring device 10 includes an LED light source 1, a collimating lens 2, a total reflection mirror 3, a dichroic mirror (dielectric multilayer film mirror) 4, and a camera 6. The collimating lens 2 is arranged so as to be movable in the optical axis direction of the excitation light by a moving mechanism (not shown). The LED light source 1 includes an LED and a beam expander for shaping light emitted from the LED to a predetermined divergence angle. Alternatively, instead of the LED light source 1, a laser light source having a laser and a beam expander for shaping light emitted from the laser into a predetermined spread angle may be used.

  Fuel cells of various sizes are used depending on the application and the place of use. Therefore, the size of the oxygen gas flow path also varies from about 10 mm square to 1000 mm square. In the oxygen concentration measuring apparatus 10 of the present embodiment, when the collimating lens 2 is moved away from the LED light source 1, the irradiation area of the excitation light can be increased. Therefore, the irradiation area of the excitation light can be changed according to the size of the oxygen gas flow path of the fuel cell.

  Excitation light of about 400 nm (dashed-dotted line in the figure) emitted from the LED light source 1 at a predetermined spread angle is converted into parallel light by the collimating lens 2 and then reflected by the total reflection mirror 3 and the dichroic mirror 4. The light enters the detection surface 5. As a result, the fluorescence (broken line in the figure) emitted from the oxygen-sensitive substance applied to the detection surface 5 is imaged by the camera 6, subjected to predetermined image processing, and displayed on a screen of a display unit (not shown). Is done.

  In the oxygen concentration measuring device 10 of the present embodiment, a cover member 8 is attached to the light incident surface 7 of the camera 6. The cover member 8 is a cylindrical body opened in a direction facing the detection surface 5. The cover member 8 is preferably made of a black resin or a black painted metal, whose surface is roughened to suppress reflection. Further, the optical element (ie, the collimating lens 2 and the total reflection mirror 3) positioned on the optical path through which the excitation light passes prevents the stray light generated by scattering the excitation light from directly entering the light incident surface 7. It is formed in length. That is, the cover member 8 is mounted so as to block a linear path connecting the collimating lens 2 and the total reflection mirror 3 to the light incident surface 7. This is because, based on the length and shape of the cover member 8 attached to the camera 6, the collimator lens 2 and the stray light scattered by the total reflection mirror 3 do not directly enter the light incident surface 7. In other words, the total reflection mirror 3 is arranged. Therefore, even if the excitation light is scattered by the collimator lens 2 and the total reflection mirror 3 and becomes stray light, they are not detected. Therefore, the fluorescence intensity of the detection surface 5 can be accurately measured, and the oxygen gas concentration can be measured with high accuracy.

  The shape of the cover member 8 can be changed according to the size of the detection surface 5. For example, when the detection surface 5 is larger than the light incident surface 7, the entire cover member 8 can be configured to be deformable so as to be larger according to the size of the detection surface 5. By appropriately increasing the size of the cover member 8 as compared with the size of the camera 6, the entry of stray light can be more effectively suppressed.

  The above embodiment is an example, and can be appropriately changed in accordance with the gist of the present invention. Although an LED light source is used in the above embodiment, a white light source that emits light in a wavelength range that includes a wavelength at which light is absorbed by the oxygen-sensitive substance but does not include the fluorescence wavelength of the oxygen-sensitive substance may be used. Further, in the present embodiment, the case where the oxygen gas concentration in the oxygen gas flow path of the fuel cell is measured has been described as an example, but it goes without saying that the oxygen gas concentration in other measurement target spaces can be similarly measured. .

Instead of the irradiation optical system in the above embodiment, a configuration as shown in FIG. 3 or FIG. 4 can be adopted.
In the oxygen concentration measuring device 20 shown in FIG. 3, the excitation light from the LED light source 11 is converted into parallel light by the collimating lens 12, and is irradiated on the detection surface 15 from an oblique direction. Then, the fluorescence from the oxygen-sensitive substance applied to the detection surface 15 is imaged by the camera 16. The camera 16 includes a cover member 18 on the light incident surface 17 as in the above embodiment. In this configuration, since a total reflection mirror or a dichroic mirror is not used, it is possible to reduce the generation factor of stray light.

  In the oxygen concentration measuring device 30 shown in FIG. 4, the excitation light from the LED light source 21 is converted into parallel light by the collimator lens 22, and the parallel light passes through the dichroic mirror 23 and irradiates the detection surface 25. The fluorescence from the detection surface 25 is reflected by the dichroic mirror 23 and the total reflection mirror 24, and then captured by the camera 26. The camera 26 also has a cover member 28 on the light incident surface 27 as in the above embodiment. The dichroic mirror 23 used in the configuration shown in FIG. 4 is different from the dichroic mirror used in the configuration shown in FIG. 2 in that it transmits light having the wavelength of excitation light and reflects light having the wavelength of fluorescence. In this configuration, a dichroic mirror that transmits excitation light and reflects fluorescence may be used instead of the total reflection mirror 24. By using the dichroic mirror, stray light generated by scattering of the excitation light (that is, stray light having the same wavelength as the excitation light) can be more reliably blocked, and the measurement accuracy of the oxygen gas can be further improved.

1, 11, 21 ... LED light sources 10, 20, 30 ... Oxygen concentration measuring device 2, 12, 22 ... Collimating lenses 3, 24 ... Total reflection mirror 4, 23 ... Dichroic mirrors 5, 15, 25 ... Detection surfaces 6, 16 , 26: Cameras 7, 17, 27: Light incident surface 8, 18, 28: Cover member

Claims (4)

An apparatus for measuring the oxygen gas concentration of the measurement target space by measuring the fluorescence intensity of the oxygen-sensitive substance applied to the detection surface placed in the measurement target space,
a) a light source that emits excitation light of a predetermined wavelength;
b) irradiating the excitation light on the detection surface, an irradiation optical system including an optical element,
a light incident surface which the fluorescence incident emitted from c) the oxygen sensitive material, one end opening in a direction facing the detection surface, the other end is in contact with the light incident surface, the fluorescent of the optical element A light detection unit having a cover member that is a tubular body that blocks a linear path connecting the optical element and the light incident surface, which is disposed outside a path incident on the light incident surface,
An oxygen concentration measuring device comprising:   2. The oxygen concentration measuring device according to claim 1, wherein the irradiation optical system includes a collimating optical element movably arranged in an optical axis direction of the excitation light. 3.   The oxygen concentration measuring device according to claim 1, wherein a shape of the cover member can be changed according to a size of the detection surface. Apply an oxygen-sensitive substance that emits fluorescence of different intensity according to the oxygen concentration on the detection surface placed in the measurement target space,
Excitation light of a predetermined wavelength is irradiated on the detection surface by an irradiation optical system including an optical element,
Fluorescence from the oxygen-sensitive substance applied to the detection surface, a light incident surface on which the fluorescence is incident, one end is opened in a direction facing the detection surface, and the other end is in contact with the light incident surface. A light detection device having a cover member that is a cylindrical body that blocks a linear path connecting the optical element and the optical element , the optical element being disposed outside a path through which the fluorescence is incident on the light incident surface; A method for measuring oxygen concentration, characterized in that the oxygen concentration is detected by a part.

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