Flame sensor and flame detection method using the same

Abstract

This invention provides a flame sensor that offers improved detection performance when installed on piping for burners or other devices, or when positioned facing openings in light shields, and that can detect the entire ultraviolet region, including UV-A, at high speed and with high sensitivity, as well as a flame detection method utilizing this sensor. [Solution] A flame sensor 2 comprising a main electrode 3 having a light-receiving surface 31, a titanium oxide film 4 covering the light-receiving surface 31 of the main electrode 3, a counter electrode 5 positioned so as not to obstruct the light reception of the titanium oxide film 4 on the light-receiving surface 31 and generating a potential difference with the main electrode 3, and an electrolyte 6 interposed between the titanium oxide film 4 and the counter electrode 5. The main electrode 3 is made of titanium, and the light-receiving surface 31 is circular. The thickness of the titanium oxide film 4 is 170 to 320 nm. A flame detection method using the flame sensor 2 is provided, which measures the change in the potential difference between the main electrode 3 and the counter electrode 5 that occurs when ultraviolet light is received by the titanium oxide film 4 on the light-receiving surface 31.

Description

Technical Field

[0005]

[0001] The present invention relates to a flame sensor for detecting a flame at high speed and high sensitivity, and a flame detection method using the same.

Background Art

[0002] It is a known fact that the wavelength in the UV region is slightly included in a flame. However, an ammonia flame, which is expected as a next-generation energy, contains only wavelengths in a much smaller ultraviolet region and is difficult to detect. Its detection has become an extremely important technology in recent years when the deadline for energy conversion is approaching.

[0003] For example, as described in FIG. 13 of "Basic Study on the Development of In-Furnace Ammonia Flame Visualization Technology for GX Acceleration" described in Non-Patent Document 1, it has been shown that for the visualization of an ammonia flame, a wavelength region of 240 to 290 nm where the influence due to the absorption of NOx is weakened is used. [[ID=??]]

[0004] Near-ultraviolet rays of sunlight (UV-A (400 to 315 nm) and UV-B (315 to 280 nm)) pass through the ozone layer and reach the earth's surface, while UV-C (280 to 100 nm) of sunlight is absorbed by the ozone layer and does not reach the earth's surface. However, when a flame burns, a small amount of UV-C is generated by a chemical reaction with oxygen in the air. In order to prevent false detection by sunlight, it is known that ultraviolet detection type flame detection performs detection limited to the wavelength region of UV-C.

[0005] <​​​ [Non-patent literature]

[0006] [Non-Patent Document 1] "Basic Study on the Development of In-Factor Ammonia Flame Visualization Technology for Accelerating GX," Shikoku Electric Power Co., Inc., Shikoku Electric Power Transmission & Distribution Co., Inc., Shikoku Research Institute, Research Report 120 (June 2024) 7-13 [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2023-35577 [Overview of the project] [Problems that the invention aims to solve]

[0008] Burners used in combustion furnaces and the like are equipped with flame-detecting sensors at the rear end of the flame-emitting pipe, but there were no sensors capable of detecting ammonia flames.

[0009] The interiors of combustion furnaces and similar equipment are shielded from sunlight, thus avoiding its effects. Therefore, even if the wavelength range is expanded to include the ultraviolet region, false detections will not occur in terms of application. Consequently, there is no problem in detecting all ultraviolet regions, including UV-A.

[0010] In view of these circumstances, the present invention aims to provide a flame sensor that can detect flames in the entire ultraviolet region at high speed and with high sensitivity, and a flame detection method utilizing the same, while improving detection performance when installed in piping such as burners or facing openings in light shielding plates. Furthermore, the present invention aims to provide a sensor that can detect flames generated by the combustion of ammonia in particular. Further, the present invention aims to provide a flame sensor that can accurately detect the presence or absence of a flame. And yet another objective of the present invention is to provide a flame sensor with controlled flame detection characteristics. [Means for solving the problem]

[0011] To solve at least one of the above problems, the present invention provides a flame sensor for detecting flames, comprising: a main electrode having a light-receiving surface provided with an ultraviolet-absorbing film made of a material having a bandgap energy of 3.0 eV or more; a counter electrode positioned so as not to obstruct the light reception of the ultraviolet-absorbing titanium oxide film on the light-receiving surface, and generating a potential difference between itself and the main electrode; and an electrolyte interposed between the ultraviolet-absorbing titanium oxide film and the counter electrode. According to the flame sensor, various flames, including ammonia flames, can be detected by measuring the change in potential difference between the main electrode and the counter electrode. The aforementioned ultraviolet absorbing film is formed using a material with a bandgap energy of 3.0 eV or higher, preferably a material with a bandgap energy of 3.5 eV to 4.2 eV, and particularly preferably a material with a bandgap energy of 3.8 eV to 4.1 eV. This is to efficiently detect ammonia flames.

[0012] Materials with a band gap energy of 3.0 eV or higher include oxides such as zinc oxide (band gap approximately 3.4 eV), gallium oxide (band gap approximately 4.7 eV), titanium oxide (band gap of anatase and rutile types is 3.0 eV to 3.2 eV), indium oxide (band gap approximately 3.6 eV), tantalum oxide (band gap ranges from 3.8 eV to 5.3 eV), and niobium oxide (band gap approximately 3.6 eV). Among these, titanium oxide, tantalum oxide, and niobium oxide are preferable, with titanium oxide being particularly desirable, considering the effects of water and the human body. Furthermore, considering ultraviolet absorption, rutile-type titanium oxide is preferable.

[0013] The titanium oxide film is an n-type semiconductor with a bandgap energy of approximately 3.2 eV and exhibits photocatalytic activity when irradiated with ultraviolet light (λ ≤ 380 nm) from a flame. Furthermore, this titanium oxide film allows for the detection of UV-A (315-400 nm), including 310 nm, which has high emission intensity in ammonia flames, even when UV transmittance is low due to UV absorption by NOx generated during ammonia combustion. Therefore, ammonia flames can be detected more accurately.

[0014] The counter electrode can be made of any conductive material that can generate a potential difference between it and the main electrode. The counter electrode can be made of, for example, silver, platinum, carbon, copper, copper-tungsten alloy, silver-tungsten alloy, brass, graphite, copper-graphite, etc., which are stable with respect to the electrolyte. The counter electrode can have an oxide film, chloride film, sulfide film, etc. formed on the surface in contact with the electrolyte as needed.

[0015] The electrolyte may be an aqueous solution or a solid electrolyte. Preferably, the electrolyte can be a substance that dissolves in a solvent and dissociates into cations and anions, such as an aqueous solution or gel-like liquid of sodium sulfate, sodium hydroxide, potassium hydroxide, lithium hydroxide, hydrochloric acid, sodium chloride, potassium chloride, lithium chloride, potassium iodide, etc., which have low electrical resistance. The electrolyte can be replaced with a semi-solid electrolyte in which the electrolyte is dissolved in a gel-like solvent.

[0016] The main electrode consists of a disc-shaped light-receiving end having a light-receiving surface and a terminal rod extending from the side of the light-receiving end opposite to the light-receiving surface, and the light-receiving end and terminal rod are made of titanium. The main electrode and counter electrode are housed in a cylindrical container filled with an electrolyte and having a transparent tip, and one end of the terminal rod of the main electrode and one end of the counter electrode protrude from the cylindrical container, thus forming a flame sensor.

[0017] The electrolyte can be sealed in a cylindrical container in a manner that prevents leakage, together with the main electrode and the counter electrode. The cylindrical container is configured to allow at least the titanium oxide coating on the light-receiving surface of the main electrode to be optically exposed (transmitted light), and it is desirable that the end facing the light-receiving surface be made transparent. The cylindrical container can be, for example, a quartz tube, and the ends of the main electrode and the counter electrode are led out of the container and closed.

[0018] In the aforementioned main electrode, it is desirable that the light-receiving surface be formed in a circular, particularly disc-shaped, form. This is because the shape allows for viewing into the furnace, is applicable to existing equipment, and maximizes the sensitivity of the light-receiving surface. In other words, when a circular or disc-shaped light-receiving surface faces piping such as burners or openings in light-shielding plates, it is easier to secure a larger light-receiving area compared to polygons including squares, allowing for more efficient light reception and improved detection performance. In order to accommodate such a circular or disc-shaped light-receiving surface, it is desirable that the cylindrical container be formed as a cylindrical container.

[0019] The main electrode can easily form the oxide film by oxide film treatment of the light-receiving surface. In particular, by forming the light-receiving surface by anodic oxidation, the main electrode can form the oxide film more uniformly, thereby increasing production efficiency. Especially when the main electrode is made of titanium, a uniform titanium oxide film can be formed by anodic oxidation of its light-receiving surface.

[0020] The thickness of the ultraviolet absorption film can be 170 to 320 nm. Of these, a thickness of 20 nm to 170 nm of the ultraviolet absorption film can detect particularly large flames, but preferably the thickness of the ultraviolet absorption film is in the range of 200 nm to 320 nm. By setting the thickness of the ultraviolet absorption film to 170-320 nm, the detection performance of the flame sensor can be most effectively enhanced. If the thickness of the ultraviolet absorption film is less than 170 nm, there is a risk that sufficient detection performance cannot be obtained. Furthermore, if the thickness of the ultraviolet absorption film exceeds 320 nm, there is a risk that the detection performance will decrease or production costs will increase.

[0021] In the present invention, in order to solve at least any of the above problems, a flame sensor is provided in which the detection characteristics of a flame are controlled by the film thickness of an ultraviolet absorption film. That is, a flame sensor for detecting a flame, comprising a main electrode provided with a light receiving surface provided with an ultraviolet absorption film, a counter electrode provided at a position that does not block the light reception of the ultraviolet absorption film on the light receiving surface, and generating a potential difference between the main electrode, and an electrolyte interposed between the ultraviolet absorption film and the counter electrode, and a flame sensor is provided in which the detection sensitivity of a flame is controlled by the film thickness of the ultraviolet absorption film. The ultraviolet absorption film can be formed by anodizing the light receiving surface of the main electrode, and the film thickness of the ultraviolet absorption film can be adjusted by controlling the conditions (voltage and time) of the anodization. And by the film thickness, the voltage output by the flame sensor at the time of detecting a flame and the time until detection can be adjusted. More specifically, as the voltage during anodization increases, the film thickness becomes thicker. And as the film thickness becomes thicker, the voltage at the time of flame detection becomes higher. On the other hand, as the film thickness becomes thicker, the detection time of the change in pressure at the time of flame detection becomes longer, and the sensitivity becomes dull. Therefore, a flame sensor can be manufactured in which the sensitivity, detection time, and responsiveness of the flame sensor are adjusted by the thickness of this oxide film. For example, when making a flame sensor for detecting a large flame, a main electrode provided with a light receiving surface having a thin oxide film thickness can be used. Also, when making a flame sensor for detecting a small flame, a main electrode provided with a light receiving surface having a thick oxide film thickness can be used. [[ID=�10]]

[0022] The present invention provides a flame detection method using the flame sensor, which measures a change in the potential difference between the main electrode and the counter electrode that occurs when the titanium oxide film on the light receiving surface receives ultraviolet light.

[0023] According to the flame detection method, the entire ultraviolet region including UV-A can be detected at high speed and high sensitivity. The titanium oxide film exhibits photocatalytic activity with respect to the ultraviolet rays of the flame, and the excited electrons move through the electrolyte, utilizing the mechanism in which a current change occurs. In particular, it is effective to employ a titanium oxide film in order to detect UV-A (315 to 400 nm) including around 310 nm where the intensity of ammonia luminescence is high, even when the transmittance is low due to the influence of NOx. Various flames including ammonia flames in a combustion furnace where sunlight is blocked can be detected with high sensitivity.

[0024] The flame sensor has the characteristic that when energized, the voltage baseline shows a gentle drift. This phenomenon may lead to false detection where it is determined that ultraviolet rays that are not being received are being received. The flame detection method can execute a detection determination process that avoids false detection caused by this phenomenon.

[0025] In the detection determination process, the light receiving surface is exposed towards the flame generation source for an extremely short time and then shielded, and the change in the potential difference during that time is output. Further, the light receiving surface is exposed and then shielded for the next next next short time, and a threshold value of the potential difference that changes with the passage of time is obtained. Based on the change rate of this threshold value, the presence or absence of a flame can be determined.

[0026] The present invention provides a flame detection device including the flame sensor, a measurement unit capable of outputting information on the change in the potential difference between the main electrode and the counter electrode to the outside, a light reception control mechanism for controlling the light received by the flame sensor, an information processing circuit that receives and performs arithmetic processing on the change data of the potential difference output by the measurement unit, and a signal output circuit that outputs the result of the arithmetic processing of the information processing circuit. According to such a flame detection device, various flames including ammonia flames can be detected at high speed and high sensitivity.

[0027] The flame sensor incorporated into the flame detection device is not limited to having a main electrode with the titanium oxide film on the light-receiving surface. For example, the main electrode can be replaced with a metal other than the titanium oxide film that can form an oxide film. The main electrode can be replaced with tantalum, aluminum, niobium, hafnium, zirconium, zinc, tungsten, bismuth, antimony, etc. The titanium oxide film can be replaced with other oxide films. For example, the titanium oxide film can be replaced with an oxide film of tantalum, aluminum, niobium, hafnium, zirconium, zinc, tungsten, bismuth, antimony, etc.

[0028] The measurement unit can continuously receive the potential difference excited by the flame sensor upon receiving light from the flame and output it as information on the change in potential difference. The measurement unit can intermittently receive the potential difference and output it as information on the change in potential difference. The measurement unit has, for example, a power supply circuit that applies a constant voltage forming a voltage baseline between the main electrode and the counter electrode of the flame sensor.

[0029] The light-receiving control mechanism controls the time for which the flame sensor receives light from the flame. The light-receiving control mechanism controls the exposure and shielding of the flame light to the flame sensor. The light-receiving control mechanism has a shutter section that receives and shields light from the light-receiving surface and a drive section that drives the shutter section. The shutter section is an opening / closing plate, and the drive section drives the opening / closing plate to open and close. The shutter section is also a light-shielding plate having an opening, and the drive section moves the light-shielding plate back and forth or rotates it.

[0030] The opening and closing plate can be replaced with a sliding plate that reciprocates along a slide rail to open and close, or with a shielding film that is wound up on a shaft to open and then pulled out to provide cover. The drive unit can reciprocate the sliding plate, or wind up and unwind the shielding film.

[0031] The light-receiving control mechanism, measurement unit, and information processing circuit output the potential difference of the light-shielding (no-load) state and the potential difference of the light-receiving (loaded) state, which change over time, enabling accurate determination of flame reception. The signal output circuit can output the result of the flame reception determination as a signal.

[0032] For example, a typical combustion furnace burner has an ignition trial time (5 to 10 seconds or less) during which the pilot automatic shut-off valve opens and the ignition spark operates, followed by a pilot flame confirmation time (flame extinction response time + 1 second or more). The pilot flame confirmation time is the flame extinction response time.

[0033] Furthermore, after the pilot flame confirmation time, there is a main flame confirmation time (3 to 5 seconds or less) during which the main automatic shut-off valve is opened, and following the main flame confirmation time, there is a flame extinguishing response time and a pilot automatic shut-off valve closing time (3 seconds or less) that follows the closing of the pilot automatic shut-off valve.

[0034] The light receiving control mechanism, measurement unit, and information processing circuit operate within a few seconds of the flame extinguishing response time and can output a signal indicating the result of the flame light reception judgment. It is desirable that the time from the detection of flame light to the output of the signal indicating the result of the flame light reception judgment be within 1 second.

[0035] The light receiving control mechanism includes, for example, a shutter mechanism that opens and closes the light receiving surface, and opens and closes the shutter mechanism multiple times within the flame extinguishing response time and / or the pilot automatic shut-off valve closing time, thereby enabling flame reception each time the shutter mechanism is opened or closed.

[0036] The information processing circuit includes a flame detection application and a display capable of displaying flame detection results, and can display the flame detection results within 1 second of the flame extinguishing response time and / or pilot automatic shutoff valve closing time.

[0037] The present invention provides a flame detection method that utilizes a flame detection device and comprises the steps of: the measurement unit outputting information on the change in potential difference between the main electrode and the counter electrode of the flame sensor to the outside; the light receiving control mechanism controlling the light received by the flame sensor; the information processing circuit receiving the potential difference change data output by the measurement unit and performing calculation processing; and the signal output circuit outputting a signal to notify the change in potential difference.

[0038] As described above, the flame sensor has the characteristic that when power is applied, the voltage baseline shows a gradual up-and-down movement (hereinafter referred to as "drift"). To avoid false detections caused by this phenomenon, where flame light that is not being received is mistakenly judged to have been received, the light receiving control mechanism controls the exposure and shielding of the light receiving surface, and the information processing circuit can perform calculations on the output result of the measurement unit.

[0039] The information processing circuit acquires the potential difference of the light-shielding state and the potential difference of the light-receiving state of the flame sensor, which change over time due to the operation of the light-receiving control mechanism. The information processing circuit uses the potential difference of the light-shielding state as a threshold, and determines that UV light has been received if the potential difference of the light-receiving state immediately after is higher than the threshold of the preceding state. The information processing circuit prevents misjudgments due to a gradual drift (rise) of the voltage baseline and can determine UV light reception more accurately. The determination result of the information processing circuit can be output externally through the signal output circuit. [Effects of the Invention]

[0040] The flame sensor and flame detection method using the present invention can improve detection performance when installed on piping such as burners or when facing an opening in a light shield, and can achieve the excellent effect of detecting the entire ultraviolet region, including UV-A, at high speed and with high sensitivity. [Brief explanation of the drawing]

[0041] [Figure 1]Figure 1 shows a schematic configuration of a flame sensor 2 according to one embodiment of the present invention. (A) is a perspective view showing the flame sensor 2. (B) is a three-view drawing showing an example of the main electrode 3. (C) is a cross-sectional view showing another example of the main electrode 3. [Figure 2] This is a perspective view showing an example of a flame detection device 1. [Figure 3] This is a perspective view showing another example of flame detection device 1. [Figure 4] This is a block diagram showing an example of the control system for flame detection device 1. [Figure 5] This is a perspective view showing the flame sensor 2 located at the rear end of the burner. [Figure 6] (A) and (B) are graphs showing examples of output data from the UV detection circuit and the drift state, which is characteristic of flame sensor 2 in which UV is not detected in other examples. [Figure 7] An example of the output data from the flame sensor 2 is shown. (A) is a graph in which the vertical axis shows potential difference and the horizontal axis shows time, with arrow A indicating the timing when the light shielding mechanism opened and arrow B indicating the timing when the light shielding mechanism closed. (B) is a graph in which an example of the correction value for the output data of the flame sensor 2 is shown. [Figure 8] Graph showing the correlation between film thickness and voltage change under anodic oxidation conditions in Example 1. [Figure 9] Graph showing the difference in response under different anodizing conditions in Example 1. [Modes for carrying out the invention]

[0042] The flame sensor according to this embodiment and the flame detection method using the same will be described in detail below with reference to the drawings. As shown in Figure 1(A), the flame sensor 2 of this embodiment has a main electrode 3 having a light-receiving surface 31, a titanium oxide film 4 covering the light-receiving surface 31 of the main electrode 3, a counter electrode 5 positioned so as not to obstruct the light reception of the titanium oxide film 4 on the light-receiving surface 31 and generating a potential difference with the main electrode 3, and an electrolyte 6 interposed between the titanium oxide film 4 and the counter electrode 5.

[0043] (Flame sensor) As shown in Figures 1(A) and 1(B), the main electrode 3 has a short column portion 30 and a terminal portion 32. One of the two end faces of the short column portion 30 is the light-receiving surface 31, and the terminal portion 32 extends from near the outer edge on the back surface opposite the light-receiving surface 31.

[0044] The short column portion 30 is made of a pure titanium (99.5%) disc with a diameter of Φ20.0 mm and a thickness of 5.0 mm. The light-receiving surface 31 can be one of the two circular planar end faces at either end of the short cylindrical shape of the short column portion 30. The terminal portion 32 is made of a pure titanium (99.5%) wire with a diameter of Φ1.0 mm. The terminal portion 32 can be erected perpendicular to the back surface of the short column portion 30. The light-receiving end portion 30 and the terminal portion 32 can be integrated by welding, solid-state bonding, or the like.

[0045] As shown in Figure 1(C), the light-receiving surface 31 of the short column portion 30 can be an elliptical convex shape. The light-receiving surface 31 can be a spherical convex, non-spherical convex, spherical concave, non-spherical concave, or the like. As shown in Figure 1(A), the main electrode 3 can be coated with an oxide film on the entire surface of the short column portion 30 including the light-receiving surface 31, and the terminal portion 32, excluding the area of ​​the terminal end 33 connected to the measurement unit 7 described later, to form a titanium oxide film 4 with a thickness of 170 to 320 nm. If the titanium oxide film 4 is formed only on the light-receiving surface 31, an insulating film can be provided on the entire surface of the main electrode 3, excluding the light-receiving surface 31 with the titanium oxide film 4 and the terminal end 33.

[0046] The counter electrode 5 is made of a pure silver rod with a diameter of Φ1.9 mm. The counter electrode 5 is cylindrical and can be coated with a silver oxide film, silver chloride film, silver sulfide film, etc., except for the terminal end 50. The counter electrode 5 has its electrode end 51 facing the back surface of the short column portion 30 of the main electrode 3, separated by a gap. The counter electrode 5 is positioned near the outer edge of the main electrode 3, 180° opposite to the terminal rod 32, and is positioned parallel to the terminal portion 32, separated by a gap.

[0047] The main electrode 3 and the counter electrode 5 are housed in a quartz tube 60, which serves as a cylindrical container. The quartz tube 60 is a test tube shape with a diameter of Φ25.0 mm and a length of 50.0 mm, with a spherical tip that serves as a light-transmitting wall 61 and a base end opening 62 at the base end. The quartz tube 60 is filled with sodium hydroxide 6 as an electrolyte 6 to fill the space between the titanium oxide film 4 of the main electrode 3 and the counter electrode 5. The base end opening 62 is sealed with a silicone stopper 63. The stopper 63 has two terminal holes 64 that penetrate the terminal portion 32 and the terminal ends 33 and 50 of the counter electrode 5, respectively. The light-receiving surface 31 of the main electrode 3 can be positioned perpendicular and concentrically to the axis of the quartz tube 60.

[0048] The terminal portion 32 of the main electrode 3 is coated with the titanium oxide film 4 up to the outside of the terminal hole 64 of the plug 63, so that only the titanium oxide film 4 is in contact with the electrolyte 6, and only the terminal end 33 exposed from the terminal hole 64 does not have the titanium oxide film 4. Furthermore, if the counter electrode 5 has a coating such as a silver oxide film or a silver chloride film, the coating is in contact with the electrolyte 6, and the terminal end 51 extending outward from the terminal hole 64 does not have the coating.

[0049] The flame sensor 2 can be used in the flame detection method of this embodiment. The flame detection method utilizes the flame sensor 2 to measure the change in potential difference between the main electrode 3 and the counter electrode 5 that occurs when ultraviolet light is received on the titanium oxide film 4 of the light-receiving surface 31. The flame sensor 2 can detect the entire ultraviolet region, including UV-A, and can detect various flames, including ammonia flames, at high speed and with high sensitivity.

[0050] As shown in Figure 5, the flame sensor 2 can be mounted with the titanium oxide film 4 of the light-receiving surface 31 and the light-transmitting wall 61 facing the flame-receiving tip of the burner 20, which is installed in a combustion furnace or the like, inside the base end opposite to the tip that emits the flame of the burner 20. As shown in Figure 1(A), the light-receiving surface 31 and the light-transmitting wall 61 have a circular cross-sectional shape, and the quartz tube 60 is cylindrical, so it can be easily mounted inside the piping of the burner 20 or the like via an adapter or the like. The flame sensor 2 can be incorporated into the flame detection device 1 according to this embodiment.

[0051] (Flame detection device) As shown in Figures 1(A), 2, and 4, the flame detection device 1 comprises the flame sensor 2, a measurement unit 7 capable of outputting information on the change in potential difference between the main electrode 3 and the counter electrode 5 to the outside, a light receiving control mechanism 8 that controls the light received by the flame sensor 2, an information processing circuit 9 that receives and processes the potential difference change data output by the measurement unit 7, and a signal output circuit 10 that outputs the result of the calculation processing of the information processing circuit 9. However, the measurement unit does not have to be configured as the flame sensor in this embodiment and may be an external measuring device.

[0052] As shown in Figure 4, the flame detection device 1 includes, for example, a light receiving control mechanism 8, a flame sensor 2, a measurement unit 7, an information processing circuit 9, and an alarm system 10 which is a signal output circuit 10. The light receiving control mechanism 8, the flame sensor 2, the measurement unit 7, and the information processing circuit 9 can be integrally controlled by a control unit 90 consisting of hardware and software provided in the information processing circuit 9.

[0053] The measurement unit 7 is connected to the terminal end 33 of the main electrode 3 of the flame sensor 2 and the terminal end 50 of the counter electrode 5. The measurement unit 7 has a power supply circuit that applies a constant voltage that forms a voltage baseline between the main electrode 3 and the counter electrode 5. The measurement unit 7 measures the change in potential difference that occurs between the main electrode 3 and the counter electrode 5 and outputs it as information on the change in potential difference. The measurement unit 7 is controlled by the control unit 90.

[0054] As shown in Figures 6(A) and (B), the flame sensor 2 and measurement unit 7 of this embodiment have the characteristic that the voltage baseline shows a gradual drift when energized. This drift can be caused by electromagnetic waves in the circuit or other external factors, resulting in a slight increase in voltage as shown in Figure 6(A), or a decrease in voltage as shown in Figure 6(B). Therefore, the light receiving control mechanism 8, information processing circuit 9, and control unit 90 prevent false detection of flame ignition and extinguishing due to this drift.

[0055] As shown in Figure 2, the light receiving control mechanism 8 includes a shutter section 80 and a drive section 81 that drives the shutter section 80. The shutter section 80 is a light-shielding plate 801 having openings 803, and the drive section 81 reciprocates or rotates the light-shielding plate 801. The light-shielding plate 801 is disc-shaped with a diameter approximately three times that of the light-receiving surface 31 of the flame sensor 2, and has an axis 802 at the center of the disc shape. Three openings 803 are formed around the axis 802 at equal opening angles (e.g., 120°), with openings approximately corresponding to the diameter Φ20mm of the light-receiving surface 31. The diameter of the openings 803 can be approximately Φ25mm, which is equal to the diameter of the light-transmitting wall 61 of the quartz tube 60. The motor 81, which is the drive section 81, can be connected to the light-shielding plate 801 to enable high-speed rotation.

[0056] The openings 803 are positioned on the same radius around the shaft 802, and the flame sensor 2 is positioned such that the light-receiving surface 31 faces the openings 803. The flame light to be detected is shown by the white arrow in Figure 2(A). When the light shielding plate 801 rotates and one of the openings 803 corresponds to the light-receiving surface 31, the titanium oxide coating 4 on the light-receiving surface 31 receives the light, and when the opening 803 moves away from the light-receiving surface 31, the titanium oxide coating 4 on the light-receiving surface 31 is shielded.

[0057] As shown in Figure 3, the light receiving control mechanism 8 uses an opening / closing plate 804 for the shutter section 80, and the drive unit 81 drives the opening / closing plate 804 to open and close. The opening / closing plate 804 is a flat plate with an area that can shield the light-receiving surface 31 and / or the light-transmitting wall 61 of the flame sensor 2, and has an axis 802 on one edge of the flat plate. A motor 81, which is the drive unit 81, is connected to the axis 802, allowing the opening / closing plate 804 to open and close at high speed. When the opening / closing plate 804 is open, it receives light on the titanium oxide coating 4 of the light-receiving surface 31, and when it is closed, it shields the titanium oxide coating 4 of the light-receiving surface 31. The light receiving control mechanism 8 makes it possible to acquire the potential difference (or "output voltage"; the same applies hereinafter) of the light-shielding state of the flame sensor 2 and the potential difference (or "output voltage"; the same applies hereinafter) of the light-receiving state, which change over time.

[0058] As shown in Figures 2 and 4, the information processing circuit 9 and the control unit 90 apply a constant voltage that forms a voltage baseline to the flame sensor 2 from the power supply circuit of the measurement unit 7. The information processing circuit 9 and the control unit 90 control the light receiving control mechanism 8 to repeatedly shield and expose the titanium oxide film 4 on the light receiving surface 31. As shown in Figure 7(A), the information processing circuit 9 and the control unit 90 acquire the potential difference of the light-receiving state (arrow A) and the potential difference of the light-shielding state (arrow B), which change over time, from the measurement unit 7. The flame sensor 2 of this embodiment is characterized in that the potential difference of the light-receiving state decreases over time, and the potential difference of the light-shielding state increases over time.

[0059] The control unit 90 controls the light receiving control mechanism 8 to open and close multiple times per second during a few seconds of flame confirmation time, such as the flame extinguishing response time and / or pilot automatic shut-off valve closing time set in the control circuit of a combustion furnace burner, for example. The light receiving control mechanism 8 can open and close for a few times per second to tens of thousands of times per second. The control unit 90 may be provided with a detection timing linkage means consisting of software and / or hardware that works in conjunction with the control device of a combustion furnace burner, etc., to detect ignition and extinguishing at appropriate timings such as ignition, combustion, and extinguishing.

[0060] The information processing circuit 9 and control unit 90 use the potential difference in the light-shielding state (arrow B) as a threshold, and determine UV light reception when the potential difference in the light-receiving state immediately afterward (arrow A) is higher than the previous threshold (arrow B). The information processing circuit 9 and control unit 90 prevent misjudgments caused by the gradual drift of the voltage baseline of the flame sensor 2, and can more accurately determine UV light reception (ignition).

[0061] As shown in Figure 7(B), the information processing circuit 9 and the control unit 90 determine the rate of change of the threshold from the potential difference of the light-shielding state (arrow B) which changes over time, predict the next threshold based on this rate of change, and determine that UV has been detected (ignited) when the potential difference is greater than the predicted threshold.

[0062] As shown in Figure 7(A), the information processing circuit 9 and the control unit 90 determine the rate of change of the potential difference of the light-receiving state (arrow A) as it changes over time, predict the potential difference of the next light-receiving state (arrow A) based on this rate of change, and determine that UV has been detected (ignited) when the predicted potential difference of the light-receiving state (arrow A) is the same as or approximates the predicted potential difference.

[0063] The information processing circuit 9 and the control unit 90 perform the same information processing as described above when the flame sensor 2 detects any of the ultraviolet, visible light, and / or infrared regions, provided that the voltage baseline has the characteristic of drifting slowly as described above, thereby preventing misjudgments of ignition and extinguishing.

[0064] The alarm system 10, which serves as the signal output circuit 10, can be a monitor, speaker, warning light, various PCs, a terminal connected via a communication line, etc., connected to the information processing circuit 9 and the control unit 90. The information processing circuit 9 and the control unit 90 can be a PC, microcontroller, and interfaces connected to them, etc., which have hardware and software such as a CPU and memory connected to the measurement unit 7 and the light receiving control mechanism 8.

[0065] As shown in Figures 2 and 4, the flame detection device 1 of this embodiment can be used to implement a flame detection method. The flame detection method using the flame detection device 1 includes the steps of: the measurement unit 7 outputting information on the change in potential difference between the main electrode 3 and the counter electrode 5 of the flame sensor 2 to the outside; the light receiving control mechanism 8 controlling the light received by the flame sensor 2; the information processing circuit 9 receiving the potential difference change data output by the measurement unit 7 and performing calculation processing; and the signal output circuit 10 outputting a signal to notify the change in potential difference.

[0066] The flame detection method described above can be implemented by the control unit 90 of the information processing circuit 9 integratively controlling the light receiving control mechanism 8, the flame sensor 2, the measurement unit 7, the information processing circuit 9, and the signal output circuit 10.

[0067] The output process of the measurement unit 7 measures the change in potential difference between the main electrode 3 and the counter electrode 5 of the flame sensor 2 and sequentially outputs the acquired data of the change in potential difference. The control process of the light receiving control mechanism 8 is such that the control unit 90 cooperates with the control device of the incinerator burner through detection timing linkage means (hardware and software) and repeatedly opens and closes the shutter section 80 of the light receiving control mechanism 8 during a few seconds of flame confirmation time, such as the flame extinguishing response time and / or the pilot automatic shut-off valve closing time.

[0068] The calculation process of the information processing circuit 9 involves outputting data on the change in potential difference measured by the measurement unit 7 during multiple light reception and shielding cycles, and the information processing circuit 9, upon receiving the change in potential difference data, stores it in memory. As shown in Figure 7(A), the information processing circuit 9 acquires the potential difference of the light reception state (arrow A) and the potential difference of the light shielding state (arrow B), which change over time. The information processing circuit 9 can determine that a flame has been detected if the potential difference of the next light reception state (arrow A) is higher than the threshold of the potential difference of the previous light shielding state (arrow B), for example, if a V-shaped rise is observed. The information processing circuit 9 can determine that the fire has been extinguished if no rise is observed from the threshold of the potential difference of the previous light shielding state (arrow B), or if a V-shaped rise is not observed in the potential difference of the next light reception state (arrow A).

[0069] Furthermore, the calculation process of the information processing circuit 9, based on the data of the potential difference in the light-shielding state (arrow B) in the graph of Figure 7(A), where the voltage baseline drifts gradually for each of the flame sensors 2, determines, for example, the rate of change over time (C) of the threshold of the potential difference in the light-shielding state (arrow B), as shown in Figure 7(B). This data (C) of the rate of change over time of the threshold is stored, and the stored data (C) of the rate of change over time of the threshold is compared with the real-time potential difference in the light-receiving state (arrow A) to determine whether there is a flame or extinguishing. Because the determination is made based on stored data, ignition and extinguishing can be determined at a faster speed.

[0070] The output process of the signal output circuit 10 can be performed within 1 second of the start of the process in which the light receiving control mechanism 8 controls the light received by the flame sensor 2. In addition to outputting and notifying the ignition and extinguishing judgment results, the output process of the signal output circuit 10 also outputs a signal to a control device such as a burner or combustion furnace, which can then control actions such as re-ignition in the event of a misfire or stopping the fuel supply based on this output signal. [Examples]

[0071] In this embodiment, main electrodes were manufactured with different thicknesses of oxide films applied to the light-receiving surface of the main electrode. Figure 8 shows the correlation between film thickness and voltage change under anodic oxidation conditions, and Figure 9 shows the differences in responsiveness under anodic oxidation conditions. The samples used in the experiments shown in Figures 8 and 9 consisted of titanium with an outer diameter of 1.5 mm, which was placed in dilute sulfuric acid and subjected to different anodic oxidation conditions to form oxide films (titanium oxide films) of varying thicknesses for each sample. Specifically, samples with a titanium oxide film thickness of 20 mm (indicated as "film thickness 20 mm" in each figure), a titanium oxide film thickness of 134 mm (indicated as "film thickness 134 mm" in each figure), a titanium oxide film thickness of 254 mm (indicated as "film thickness 254 mm" in each figure), and a titanium oxide film thickness of 312 mm (indicated as "film thickness 312 mm" in each figure) were produced.

[0072] As shown in Figure 8, when the overvoltage during anodizing was low, the output voltage was also low, while when the overvoltage during anodizing was high, the output voltage was also high. Furthermore, the response time during detection was faster when the overvoltage during anodizing was low. As shown in Figure 9, the thickness of the oxide film and the output voltage increased as the overvoltage during anodizing increased. Specifically, the thickness and output voltage increased in the following order: "thickness 20 mm", "thickness 134 mm", "thickness 254 mm", and "thickness 312 mm". [Industrial applicability]

[0073] The flame sensor of the present invention, and the flame detection method utilizing the same, can be used for ignition control of combustion furnaces, burner control, flame monitoring, fire alarms, ultraviolet light, visible light, infrared light, etc., as well as other detectors or alarms. [Explanation of symbols]

[0074] 1. Flame detection device 2 Flame sensor 20 Same Burner 3 Main electrode 30 Same light receiving end 31 Same light-receiving surface 32 Same terminal bar 33 Same terminal end 4. Titanium oxide film 5 pairs of electrodes 50 Same terminal end 51 Same electrode end 6 Electrolytes 60. Quartz tube (cylindrical container) 61 Translucent wall 62 Proximal opening 63 Same stopper 64 Same terminal hole 7 Measurement Unit 8. Light Reception Control Mechanism 80 Same shutter section 801 Same light-shielding plate 802 coaxial 803 Same opening 804 Same Opening / Closing Plate 81. Same motor (drive unit) 9. Information Processing Circuits 90 Control unit (detection timing control means) 10. Alarm system (signal output circuit)

Claims

1. A flame sensor that detects flames, A main electrode having a light-receiving surface provided with an ultraviolet absorption film made of a material with a bandgap energy of 3.0 eV or more, A counter electrode is provided in a position that does not obstruct the light reception of the ultraviolet absorption film on the light-receiving surface, and generates a potential difference between itself and the main electrode, The electrolyte interposed between the ultraviolet absorbing film and the counter electrode, A sharp flame sensor.

2. The main electrode consists of a disc-shaped light-receiving end having the light-receiving surface and a terminal rod extending from the side of the light-receiving end opposite to the light-receiving surface, and the light-receiving end and the terminal rod are made of titanium. The flame sensor according to claim 2, wherein the main electrode and the counter electrode are housed in a cylindrical container filled with an electrolyte and having a transparent tip, and one end of the terminal rod of the main electrode and one end of the counter electrode protrude from the cylindrical container.

3. The flame sensor according to claim 1 or 2, wherein the thickness of the ultraviolet absorbing film is 170 to 320 nm.

4. The flame sensor according to claim 1 or 2, wherein the thickness of the ultraviolet absorbing film provided on the light-receiving surface is adjusted according to the voltage output by the flame sensor when a flame is detected.

5. Using the aforementioned flame sensor, A flame detection method using a flame sensor according to any one of claims 1 to 3, wherein the change in potential difference between the main electrode and the counter electrode that occurs when ultraviolet light is received on the ultraviolet absorption film of the light-receiving surface is measured.

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