JP6001289B2 - Combustion device - Google Patents

Description

  The present invention relates to a combustion apparatus for burning a combustible gas.

  Conventionally, some combustion devices that combust flammable gas have a gas detection device that can detect flammable gas or incomplete combustion gas in order to detect gas leakage from the gas supply path or incomplete combustion. (See, for example, Patent Document 1).

JP 2009-271018 A

  By the way, in order to supply a combustible gas to a combustion apparatus such as a gas fan heater whose location can be changed, gas cords having connectors suitable for the connection ports of the combustion apparatus and the gas plug are used. Here, when a regular gas cord having a connector suitable for the connection port of the combustion apparatus is not used, and a rubber tube not provided with a connection instrument suitable for the connection port is connected to the connection port of the combustion apparatus, Since the connection state between the rubber tube and the connection port is not perfect, there is a possibility that the rubber tube is detached from the connection port and the fuel gas leaks. The combustion device disclosed in the above-mentioned patent document includes a gas detection device for detecting a gas leak. This gas detection device is for detecting a gas leak during combustion, and power is consumed when combustion is stopped. Since the gas detection device is stopped in order to reduce consumption, there is a problem that gas leakage cannot be detected when combustion is stopped.

  Further, in the combustion apparatus described in Patent Document 1, when the gas detection device is stopped when the combustion is stopped, moisture adheres to the gas sensitive body included in the gas detection device, and at the start of combustion due to the attached moisture, the gas sensitive body is detected. As a result, the detection performance could be degraded.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a combustion apparatus that can detect a detection target gas even when combustion is stopped while suppressing power consumption.

Claims of the present invention is the first aspect, a combustion portion for burning fuel, and a combustion control unit for controlling the combustion state of the combustion unit, the leaked fuel gas and target gas both incomplete combustion gas generated by incomplete combustion A gas detection unit that detects the detection target gas, and a notification unit that performs a notification operation when the gas detection unit detects the detection target gas. The gas detection unit includes a gas-sensitive member which changes its electrical characteristic value by responding to the detection target gas, a heater for heating the pre-Symbol Gas sensitive body, and a heater control circuit for controlling the energization of the heater, A detection circuit for detecting the detection target gas from an electrical characteristic value of the gas sensitive body. The heater control circuit controls the energization of the heater at each time of combustion and when the combustion is stopped, so that the gas sensitive body is heated to a temperature range in which the sensitivity to the fuel gas is higher than that at the low temperature. The high temperature period in which the gas sensitive body is heated is periodically provided in a temperature range in which the sensitivity to the incomplete combustion gas is higher than that in the high temperature period. The heater control circuit controls energization of the heater so that a period other than the high temperature period is longer than that during combustion when the combustion is stopped in a repetition cycle of the high temperature period and the low temperature period. The detection circuit, and detects the detection target gas from an electrical characteristic value of the sensitive body of gas in each of the high-temperature period and the low-temperature period. Here, the fuel includes gas fuel such as city gas and propane gas mainly containing methane, and liquid fuel such as kerosene used in an oil stove or an oil fan heater. When the fuel is a gas fuel, the gas fuel itself becomes a fuel gas detected by the gas detection unit, and when the fuel is a liquid fuel, the gas generated by vaporization of the liquid fuel is detected by the gas detection unit. It becomes a fuel gas.

In the invention of claim 2, during the combustion, the heater control circuit may control energization to the heater so that the high temperature period and the low temperature period are alternately repeated. Further, when the combustion is stopped, the heater control circuit includes: the hot period, and the low-temperature period, the stop period for stopping the energization of the heater to control the energization of the heater to repeat periodically May be.

In the invention of claim 3, prior Symbol heater control circuit, before SL during combustion stop may control the energization of the said heater to increase the low-temperature period than during the combustion.

According to a fourth aspect of the present invention , when the gas detection unit detects fuel gas when the combustion is stopped, the notification unit may notify the leakage of fuel .

According to a fifth aspect of the present invention , when the gas detection unit detects fuel gas when the combustion is stopped, the combustion control unit may prohibit ignition of the fuel by the combustion unit .

  According to the first aspect of the present invention, when the combustion is stopped, the heater control circuit energizes the heater so that the sensitivity to the detection target gas is higher than the sensitivity to the gas other than the detection target gas. A heating period for heating the body is provided intermittently. Since the gas detection circuit detects the detection target gas from the electrical characteristic value of the gas sensitivity body in a state where the gas sensitivity body is heated to the above temperature range, the detection target gas is detected even when the combustion is stopped. Is possible. Further, since the heater control circuit intermittently provides the heating period when the combustion is stopped, the power consumption can be reduced as compared with the case where the gas sensitive body is continuously heated to the above temperature range, and the gas sensitive body has high power. Since the supply period is shortened, deterioration of the gas sensitive body can be suppressed. In addition, the sensitivity of the gas sensitive body may change immediately after the start of energization due to the influence of water adhering to the gas sensitive body while the energization to the heater is stopped. Since the period for heating the gas sensitive body is provided intermittently, the change in sensitivity due to the influence of moisture can be suppressed by evaporating the water adhering to the gas sensitive body.

  According to the second aspect of the present invention, the power consumption can be reduced by providing the stop period as compared with the case where the heater is continuously heated.

  According to the third aspect of the present invention, the power consumption per unit time can be reduced by extending the low temperature period at the time of stopping the combustion as compared with the time of the combustion.

  According to the invention of claim 4, it is possible to notify the user of fuel leakage even when combustion is stopped.

  According to the fifth aspect of the present invention, the ignition of the fuel is prohibited when the fuel gas is detected when the combustion is stopped, so that the possibility of igniting the leaked fuel can be reduced.

It is a schematic circuit diagram of the gas detection part used for the combustion apparatus of this embodiment. It is a block diagram same as the above. It is sectional drawing of the package which accommodated the gas sensitive part used for the same as the above. It is the perspective view which fractured | ruptured a part of the state in which the package used for the same was accommodated in the outer case. (A)-(c) is a time chart explaining operation | movement of the gas detection part at the time of combustion same as the above. (A)-(c) is a wave form diagram of the heater voltage applied to the heater of the gas detection part used for the same.

  Hereinafter, an embodiment in which the present invention is applied to a heating apparatus such as a gas fan heater that heats a room by burning fuel gas (for example, city gas) will be described with reference to FIGS. The combustion apparatus according to the present invention is not intended to be limited to a heating apparatus, and if it is a combustion apparatus having a fuel combustion section, a hot water supply apparatus that warms water with the combustion heat of the fuel, or gas cooking such as a gas stove A vessel may be used.

  FIG. 2 is a block diagram of the combustion apparatus 1, and includes a control circuit unit 10, a combustion unit 11, a fuel supply unit 12, a blower unit 13, a gas detection unit 14, an operation unit 15, a notification unit 16, And a power supply circuit unit 17.

The gas connection port 18 of the combustion apparatus 1 is connected to a gas plug P1 provided in the room via a gas cord H1 provided with a connector at both ends of the rubber tube. The fuel gas (for example, city gas 12A, 13A mainly composed of methane (CH ₄ )) supplied from the gas plug P1 to the gas connection port 18 through the gas cord H1 is sent to the fuel supply unit 12.

  The fuel supply unit 12 is provided in a gas supply path between the gas connection port 18 and the combustion unit 11, and controls the amount of fuel gas supplied to the combustion unit 11 in accordance with a control signal input from the control circuit unit 10. adjust.

  The combustion unit 11 includes a burner that combusts fuel gas supplied via the fuel supply unit 12, and warms the air by the combustion heat of the burner.

  The blower unit 13 sucks outside air from an intake port provided on the back side of the combustion apparatus main body (not shown), and blows the air sucked into the outside from the blower opening provided on the front side of the combustion apparatus main body. To do. A combustion unit 11 is disposed in an air flow path between the intake port and the blower port, and outside air introduced from the intake port is warmed by the combustion heat of the combustion unit 11 and then blown to the outside from the blower port. .

  The gas detection unit 14 is generated by incomplete combustion with fuel gas (for example, methane) leaking from a gas supply path (for example, a connection portion between the gas cord H1 and the gas connection port 18 or a gas pipe in the combustion apparatus body). Both of the incomplete combustion gases (for example, carbon monoxide) to be detected are set as detection target gases. The gas detection unit 14 performs the detection operation of the fuel gas and the incomplete combustion gas, and outputs the detection result to the control circuit unit 10.

  The operation unit 15 is provided on the surface of the combustion apparatus main body, and is provided for performing various operations such as a heating operation start operation, a stop operation, and a heating temperature setting operation.

  The notification unit 16 includes a speaker that outputs a notification sound such as a beep sound or a voice message, for example, and outputs a desired notification sound by an output signal from the control circuit unit 10.

  The control circuit unit 10 includes, for example, a microcomputer as a component, and controls the overall operation of the combustion apparatus 1 according to an operation input from the operation unit 15 and a detection result of the gas detection unit 14.

  The power supply circuit unit 17 receives power from the commercial AC power supply AC and supplies operating power to the above-described units.

  Next, the configuration of the gas detection unit 14 will be described in more detail with reference to the block diagram of FIG. The gas detection unit 14 includes a gas sensitive body 20, a heater 21, a center electrode 22, a thermistor 23, a signal processing circuit 24, and a constant voltage circuit 25.

  The constant voltage circuit 25 receives power supply from the power supply circuit unit 17 to generate a constant DC voltage (for example, DC 5V), and supplies an operating voltage to the signal processing circuit 24 and the like.

The gas sensitive body 20 is made of, for example, a sintered body of a metal oxide semiconductor such as tin oxide (SnO ₂ ), and the electrical resistance, which is an electrical characteristic value, changes in response to the detection target gas in the atmosphere. As the concentration of the detection target gas increases, the electrical resistance of the gas sensitive body 20 decreases due to the oxidation-reduction reaction of the gas sensitive body 20. In this type of gas sensitive body 20, the temperature range in which the gas sensitivity is high is different depending on the type of detection target gas. For example, in a relatively high temperature range near 400 ° C., the sensitivity of methane, which is a fuel gas, is sufficiently high compared to the sensitivity of carbon monoxide, which is an incomplete combustion gas. From the change in resistance value in this temperature range, It is possible to selectively detect methane. Also, in a relatively low temperature range around 80 ° C., the sensitivity of carbon monoxide, which is an incomplete combustion gas, is sufficiently high compared to the sensitivity of methane, which is a fuel gas. From the resistance value change in this temperature range, It is possible to selectively detect carbon monoxide. Note that the temperature range in which the sensitivity to the detection target gas is higher than that of other gas types is the required gas detection accuracy, the composition of the gas sensitive body 20, the type of detection target gas, and the detection target gas. It is set as appropriate according to the assumed concentration at the time of gas detection (at the time of alarm issuance).

  The metal oxide semiconductor that is the material of the gas sensitive body 20 preferably supports a catalyst that reduces the sensitivity to various gases. Examples of such catalysts include palladium (Pd), tungsten (W), platinum (Pt), rhodium (Rh), cerium (Ce), molybdenum (Mo), vanadium (V), and the like. One type of these catalysts may be used alone, or two or more types may be used in combination. In particular, when Pd is used as the catalyst, the responsiveness of the gas sensitive body 20 is improved. That is, as the gas concentration of the detection target gas increases, the time required for the electric resistance to stabilize after the electric resistance of the gas sensitive body 20 starts to change is shortened.

  As shown in FIG. 3, a heater 21 and a center electrode 22 are embedded in the gas sensitive body 20. The heater 21 is formed by winding a noble metal wire (for example, platinum wire) in a coil shape. The center electrode 22 is made of a rod-like noble metal wire (for example, platinum wire), and is disposed so as to penetrate the center of the heater 21 formed in a coil shape. FIG. 1 shows an equivalent circuit of the gas sensitive body 20, where the electrical resistance of the heater 21 is Rh, and the electrical resistance of the gas sensitive body 20 between one end of the heater 21 and the center electrode 22 is Rs.

  As shown in FIGS. 3 and 4, the gas sensitive body 20 is accommodated in a package 30 including a base 31 and a case 32. The base 31 is formed in a disc shape with an insulating resin, and three lead terminals 33a, 33b, 33c are provided so as to penetrate the base 31 in the thickness direction. Both ends of the heater 21 are welded to the lead terminals 33a and 33b, respectively, and one end of the center electrode 22 is welded to the lead terminal 33c. The case 32 is integrally provided with a cylindrical tube portion 32a and an upper plate portion 32b provided so as to project inward from the upper end portion of the tube portion 32a, using a metal material. A through hole 32c for ventilation is provided at the center of the upper plate portion 32b, and a stainless steel wire mesh 34 is attached to the through hole 32c in order to suppress the intrusion of dust and dirt.

  The package 30 is housed in an outer case 40 made of synthetic resin. The outer case 40 includes a cylindrical tube portion 40a having an inner diameter slightly larger than the outer diameter of the tube portion 32a, and an upper plate portion 40b provided so as to project inward from the upper end portion of the tube portion 40a. Is integrated. An opening 40c for ventilation is provided in the center of the upper plate portion 40b, and a stainless steel wire mesh 41 is attached to the opening 40c. The package 30 is housed inside the outer case 40 with the through hole 32c facing inward, and a filter 42 is disposed in the gas flow path between the through hole 32c and the opening 40c. The filter 42 is formed of, for example, activated carbon, silica gel, or the like, or may be formed of a material combining activated carbon and silica gel. When the filter 42 is provided, miscellaneous gas (for example, NOx, vapor of organic solvent such as alcohol) or poisonous gas (for example, silicon vapor) contained in the gas flowing into the outer case 40 from the opening 40c is filtered. 42 is removed. Thereby, since miscellaneous gas and poisonous gas flowing into the package 30 are reduced, erroneous detection due to miscellaneous gas is suppressed, and the gas sensitive body 20 is not easily poisoned by poisonous gas.

  As described above, the heater 21 is embedded in the gas sensitive body 20, and both ends thereof are exposed to the outside of the gas sensitive body 20. The heater 21 is connected between the output terminals of the constant voltage circuit 25 via the switching element Q1. The switching element Q1 is made of, for example, an FET (Field Effect Transistor), and its gate electrode is connected to the output terminal T1 of the signal processing circuit 24, and is switched on / off according to the output signal from the signal processing circuit 24. The signal processing circuit 24 adjusts the average value and power consumption of the voltage applied to the heater 21 by controlling the pulse width of the duty signal output from the output terminal T1 to the gate electrode of the switching element Q1, thereby sensing the sensitivity. The temperature of the gas body 20 is controlled. For example, in the high temperature period during which the fuel gas is detected, the signal processing circuit 24 sets the average value of the voltage applied to the heater 21 to about 0.9 V, and the power consumption to about 150 mW, so that the temperature of the gas sensitive body 20 is about. Control at 400 ° C. Further, the signal processing circuit 24 sets the average value of the voltage applied to the heater 21 to about 0.2 V and the power consumption to about 36 mW during the low temperature period in which the incomplete combustion gas is detected, so that the temperature of the gas sensitive body 20 is increased. Is controlled at about 80 ° C. Here, the signal processing circuit 24 and the switching element Q1 constitute a heater control circuit that controls energization to the heater 21.

  Further, both ends of the center electrode 22 are exposed to the outside of the gas sensitive body 20. One end of the center electrode 22 is electrically connected to the output terminals T2 and T3 of the signal processing circuit 24 via load resistors R1 and R2, respectively, and to the A / D input terminal T4 of the signal processing circuit 24. Connected. The signal processing circuit 24 outputs a constant voltage from the output terminal T2 or T3, and applies the voltage V1 of the center electrode 22 to A / A in a state where the constant voltage is applied to the series circuit of the load resistor R1 or R2 and the gas sensitive body 20. The data is taken from the D input terminal T4. Here, when the electric resistance of the gas sensitive body 20 changes according to the gas concentration of the detection target gas, the voltage dividing ratio between the load resistance R1 or R2 and the gas sensitive body 20 changes, and the voltage V1 of the center electrode 22 changes. To do. For example, when the gas concentration of the detection target gas increases, the electric resistance of the gas sensitive body 20 decreases, and thus the voltage V1 of the center electrode 22 decreases due to the change of the partial pressure ratio. The signal processing circuit 24 performs A / D conversion and takes in the voltage V1 input to the A / D input terminal T4 in a state where a constant voltage is output from the output terminal T2 or T3. The resistance value of the gas body 20 can be obtained.

  A series circuit of the thermistor 23 and the resistor R3 is connected between both ends of the constant voltage circuit 25, and the voltage V2 at the connection point of the thermistor 23 and the resistor R3 is input to the A / D input terminal T5 of the signal processing circuit 24. Yes. Since the electric resistance of the thermistor 23 changes according to the temperature, the voltage dividing ratio between the thermistor 23 and the resistor R3 changes according to the temperature change, and thereby the value of the voltage V2 changes. In a built-in memory (not shown) of the signal processing circuit 24, calibration curve data indicating the relationship between the ambient temperature and the voltage V2 is stored in advance. The signal processing circuit 24 can obtain the ambient temperature based on the calibration curve data and the value of the voltage V2 fetched from the A / D input terminal T5. Since the electric resistance of the gas sensitive body 20 changes under the influence of temperature and humidity, the signal processing circuit 24 corrects the electric resistance of the gas sensitive body 20 based on the ambient temperature detected using the thermistor 23. ing.

By the way, the above-mentioned gas sensitive body 20 is produced by an appropriate method. For example, when the oxide semiconductor contained in the gas sensitive body 20 is SnO ₂ , SnO ₂ powder prepared by an appropriate technique is used. For example, an aqueous solution of SnCl ₄ is hydrolyzed with NH ₄ to prepare a stannic acid sol. The stannic acid sol is air-dried and then baked in an air atmosphere at 550 to 700 ° C. for 0.5 to 3 hours, for example. When the SnO ₂ lump obtained by this firing is pulverized, SnO ₂ powder is obtained. To the powdered SnO ₂ is supported palladium (Pd) is impregnated with an aqua regia solution of Pd in the SnO ₂ powder, calcined 1 hour at for example 500 ° C. in air atmosphere. The amount of Pd supported can be 1.7% by mass with respect to SnO _2, for example. In addition to Pd, tungsten (W) may be supported at 5% by mass with respect to SnO ₂ . In addition to Pd and W, SnO ₂ contains one or more of platinum (Pt), rhodium (Rh), cerium (Ce), and molybdenum (Mo) at about 0.5 mass% with respect to SnO ₂ . It may be supported. When aggregate is used, SnO ₂ powder and aggregate powder such as alumina (α-alumina) are mixed. When an organic solvent such as polyethylene glycol, glycerin or terpineol is added to this mixture, a paste-like mixture is prepared. When this paste-like mixture is applied around the heater 21 and the center electrode 22 supported by the lead terminals 33a to 33c and baked in, for example, an air atmosphere at 500 ° C. for 1 hour, the gas sensitive body 20 is formed. The

  The gas sensitive body 20 is formed in an appropriate shape such as a flat plate shape or a spherical shape (including an elliptical spherical shape), and the size of the gas sensitive body 20 is also designed appropriately. In the present embodiment, as shown in FIG. 3, the gas sensitive body 20 is formed in an elliptical shape having a diameter in the longitudinal direction of approximately 0.5 mm and a diameter in the lateral direction of approximately 0.3 mm. When the gas sensitive body 20 is formed in a spherical shape, the gas sensitive body 20 can be reduced in size as compared with the case where the gas sensitive body 20 is formed in a flat plate shape or a cylindrical shape. The heat capacity can be reduced.

  Next, operation | movement of the combustion apparatus 1 of this embodiment is demonstrated. First, the operation of the combustion apparatus 1 during the combustion operation will be described. When the user performs an operation to start operation using the operation unit 15, the control circuit unit 10 starts fuel supply from the fuel supply unit 12 and burns the fuel gas supplied from the fuel supply unit 12 to the combustion unit 11. The air heated by the combustion heat is blown by the blower 13. The control circuit unit 10 controls the amount of fuel gas supplied from the fuel supply unit 12 and the amount of air supplied from the blower unit 13 in accordance with the instruction content from the operation unit 15, thereby adjusting the heating amount. doing.

  During this combustion, the gas detection unit 14 periodically detects the fuel gas and the incomplete combustion gas in accordance with a control command from the control circuit unit 10.

  FIG. 5 is a timing chart for explaining the operation of the gas detector 14. FIG. 5A shows an average value of voltages applied to the heater 21 (hereinafter referred to as heater voltage), and FIG. ) Shows the timing of gas detection, and FIG. 5C shows the load resistance to be used.

  The signal processing circuit 24 of the gas detection unit 14 adjusts the duty ratio of the duty signal output from the output terminal T1, thereby adjusting the period Ta (about 5 seconds) in which the average value of the heater voltage is about 0.9 V, and about Periods Tb (about 20 seconds) of 0.2 V are alternately provided. Here, in the period Ta, the gas sensitive body 20 is heated to about 400 ° C., in the period Tb, the gas sensitive body 20 is heated to about 80 ° C., the period Ta is a high temperature period, and the period Tb is a low temperature period. The signal processing circuit 24 detects the fuel gas at the timing immediately before the high temperature period Ta ends, and detects the incomplete combustion gas at the timing immediately before the low temperature period Tb ends. Further, the signal processing circuit 24 detects hydrogen gas, which is a miscellaneous gas, at a timing when a predetermined time Te (about 0.6 seconds) has elapsed since the switching from the high temperature period Ta to the low temperature period Tb.

  The signal processing circuit 24 applies a constant voltage to the series circuit of the load resistor R1 and the gas sensitive body 20 by outputting a constant voltage from the output terminal T2 in the high temperature period Ta and setting the output of the output terminal T3 to zero. . At time t1 (at the time indicated by a circle in FIG. 5B) immediately before the high temperature period Ta ends, the signal processing circuit 24 applies the voltages V1 and V2 input to the A / D input terminals T4 and T5 to the A / D, respectively. Conversion is performed, and the temperature of the voltage V1 is corrected based on the ambient temperature obtained from the voltage V2. Then, the signal processing circuit 24 compares the level of the voltage V1 after the temperature correction with the first reference voltage set corresponding to the detection level (for example, 5000 ppm) of methane as the fuel gas. When the temperature-corrected voltage V1 falls below the first reference voltage, the signal processing circuit 24 determines that gas leakage has occurred because the fuel gas concentration has exceeded the detection level, and sends a gas leakage detection signal to the control circuit unit. 10 is output. When the gas leakage detection signal is input from the gas detection unit 14, the control circuit unit 10 stops the operation of the combustion unit 11 and the fuel supply unit 12 to stop the combustion of the fuel gas, and the notification unit 16. By this, the gas leak of the fuel gas is notified. Note that the detection level of methane, which is a fuel gas, is normally set to 5000 ppm, which is one-tenth the concentration of 50000 ppm, which is the lower explosive limit (LEL).

  Further, the signal processing circuit 24 outputs a constant voltage from the output terminal T2 until the predetermined time Te elapses after switching to the low temperature period Tb, and sets the output of the output terminal T3 to zero so that the load resistance R1 and A constant voltage is applied to the series circuit with the gas sensitive body 20. At the time when the predetermined time Te has elapsed since switching to the low temperature period Tb (at the time indicated by Δ in FIG. 5B), the signal processing circuit 24 receives the voltages V1, V2 input to the A / D input terminals T4, T5. Are A / D converted, and the temperature of the voltage V1 is corrected based on the ambient temperature obtained from the voltage V2. Then, the signal processing circuit 24 compares the level of the voltage V1 after temperature correction with the third reference voltage set corresponding to the detection level of hydrogen gas, which is a miscellaneous gas. When the voltage V1 after temperature correction is lower than the third reference voltage, the signal processing circuit 24 determines that miscellaneous gas exists because the concentration of hydrogen gas exceeds the detection level, and the incomplete combustion gas or fuel gas Change the detection level to prevent misdetection due to miscellaneous gases.

  Further, when the miscellaneous gas detection operation is completed in the low temperature period Tb, the signal processing circuit 24 outputs a constant voltage from the output terminal T3 and sets the output of the output terminal T2 to zero, whereby the load resistance R2 and the gas sensitive body 20 are output. A constant voltage is applied to the series circuit. Then, at time t2 immediately before the end of the low temperature period Tb (at the time indicated by ● in FIG. 5B), the signal processing circuit 24 applies voltages V1 and V2 input to the A / D input terminals T4 and T5, respectively. A / D conversion is performed, and the temperature of the voltage V1 is corrected based on the ambient temperature obtained from the voltage V2. The signal processing circuit 24 compares the level of the voltage V1 after temperature correction with the second reference voltage set corresponding to the detection level (for example, 300 ppm) of carbon monoxide that is incomplete combustion gas. When the voltage V1 after temperature correction falls below the second reference voltage, the signal processing circuit 24 determines that incomplete combustion has occurred because the concentration of incomplete combustion gas exceeds the detection level, and a detection signal for incomplete combustion. Is output to the control circuit unit 10. When the incomplete combustion detection signal is input from the gas detection unit 14, the control circuit unit 10 stops the operation of the combustion unit 11 and the fuel supply unit 12 to stop the combustion of the fuel gas, and the notification unit 16 indicates the occurrence of incomplete combustion.

  As described above, during combustion, the signal processing circuit 24 of the gas detection unit 14 sequentially detects the presence or absence of fuel gas and incomplete combustion gas by alternately repeating the high temperature period Ta and the low temperature period Tb. Here, the signal processing circuit 24 and the load resistors R1 and R2 constitute a detection unit that detects the detection target gas from the electrical characteristic value of the gas sensitive body 20. The first reference voltage, the second reference voltage, and the third reference voltage corresponding to the detection levels of fuel gas, incomplete combustion gas, and hydrogen gas are preset in the internal memory of the microcomputer that constitutes the signal processing circuit 24. Has been.

  Next, the operation | movement at the time of the combustion stop of the combustion apparatus 1 is demonstrated. When the user performs the operation stop operation using the operation unit 15, the control circuit unit 10 stops the fuel supply by the fuel supply unit 12, stops the combustion in the combustion unit 11, and blows air by the blower unit 13. Stop operation.

The gas detection unit 14 detects fuel gas in accordance with a control command from the control circuit unit 10 even when combustion is stopped. FIG. 6B is a time chart showing an average value of the heater voltage applied to the heater 21 when the combustion is stopped. The signal processing circuit 24 of the gas detection unit 14 adjusts the duty ratio of the duty signal that drives the switching element Q1, thereby adjusting the period Ta (about 5 seconds) during which the average value of the heater voltage is about 0.9 V, and about A period Tb (about 20 seconds) of 0.2 V and a stop period Tc (about 100 seconds) for stopping energization of the heater 21 are periodically repeated in the order of Ta → Tb → Tc (125 seconds). period). In the period Ta, the gas sensitive body 20 is heated to about 400 ° C., and in the period Tb, the gas sensitive body 20 is heated to about 80 ° C. And the signal processing circuit 24 of the gas detection part 14 performs the detection process similar to the above-mentioned at the timing just before the high temperature period Ta is complete | finished, and has detected the presence or absence of fuel gas. In this case, the power consumption of the gas detection unit 14 is 150 mW in the period Ta, 36 mW in the period Tb, and 18 mW in the period Tc, and the average power consumption per unit time is about 27 mW / sec. Even in the period Tc when the sensor voltage is zero, standby power of 18 mW is generated due to power consumption of the signal processing circuit 24, the constant voltage circuit 25, and the like.

  On the other hand, FIG. 6A shows the average value of the heater voltage during normal combustion, the period Ta (5 seconds) in which the average value of the heater voltage is about 0.9 V, and the average value is about 0.2 V. Periods Tb (20 seconds) are alternately repeated (25-second cycle). In this case, the power consumption of the gas detection unit 14 is 150 mW in the period Ta and 36 mW in the period Tb, and the average power consumption per unit time is about 60 mW / sec.

  As described above, by periodically repeating the high temperature period in which the gas sensitive body 20 is heated to a relatively high temperature, the low temperature period in which the gas sensitive body 20 is heated to a relatively low temperature, and the stop period in which the heating is stopped when the combustion is stopped, The presence or absence of fuel gas can be detected even when combustion is stopped while reducing power consumption. Although the detection performance of the fuel gas that is the detection target gas is lowered by providing the stop period Tc, the period of heating to a high temperature state in which the detection of the fuel gas is performed within a range in which the minimum detection performance can be maintained is intermittent. It only has to be provided. If the gas to be detected is a fuel gas such as methane, the gas sensitive body 20 may be intermittently heated to such an extent that at least the concentration of the lower explosion limit can be detected.

  Further, the signal processing circuit 24 adjusts the duty ratio of the duty signal for driving the switching element Q1 to change the average value of the heater voltage in a pattern as shown in FIG. The application pattern is not limited to this. That is, the signal processing circuit 24 of the gas detection unit 14 can intermittently provide a period during which the gas sensitive body 20 is heated to a high temperature so that the fuel gas that is the detection target gas can be detected even when combustion is stopped. If it is, it is not limited to the application pattern shown in FIG.6 (b). For example, as shown in FIG. 6C, a period Ta (5 seconds) in which the average value of the heater voltage is about 0.9 V and a period Td in which the average value is about 0.2 V are alternately provided. May be set to a longer time (for example, 55 seconds) than at the time of combustion (period of 60 seconds). In this case, the power consumption of the gas detection unit 14 is 150 mW in the period Ta and 36 mW in the period Td, and the average power consumption per unit time is about 46 mW / sec. Therefore, the average power consumption can be reduced as compared with the time of combustion. Therefore, as shown in FIG. 6C, by making the low temperature period longer than that at the time of combustion, it is possible to detect the presence or absence of fuel gas even when the combustion is stopped while reducing the power consumption as compared with the time of combustion.

  As described above, the combustion apparatus 1 of the present embodiment includes the combustion unit 11, the control circuit unit 10 (combustion control unit), the gas detection unit 14, and the notification unit 16. The combustion unit 11 burns fuel (for example, fuel gas such as city gas). A control circuit unit 10 serving as a combustion control unit controls the combustion state of the combustion unit 11. The gas detection unit 14 detects the detection target gas using at least one of the leaked fuel gas and the incomplete combustion gas generated by the incomplete combustion as a detection target gas. The notification unit 16 performs a notification operation when the gas detection unit 14 detects the detection target gas. The gas detection unit 14 includes a gas sensitive body 20, a heater 21, a heater control circuit (comprising a signal processing circuit 24 and a switching element Q1), and a detection circuit (comprising a signal processing circuit 24 and load resistors R1 and R2). The gas sensitive body 20 changes its electric characteristic value (for example, electric resistance) in response to the detection target gas. The heater 21 heats the gas sensitive body 20 to a temperature range in which the sensitivity to the detection target gas is higher than the sensitivity to the gas other than the detection target gas. A heater control circuit (consisting of a signal processing circuit 24 and a switching element Q1) controls energization to the heater 21. The detection circuit (comprising the signal processing circuit 24 and the load resistors R1 and R2) detects the detection target gas from the electrical characteristic value of the gas sensitive body 20. When the combustion is stopped, the heater control circuit intermittently provides a heating period in which the heater 21 is energized to heat the gas sensitive body 20 to the above temperature range. The detection target gas is detected from the electrical characteristic value of the gas sensitive body 20 in a state heated to the temperature range.

  Thus, when the combustion is stopped, the heater control circuit intermittently provides a heating period in which the heater 21 is energized to heat the gas sensitive body 20 to the above temperature range. The gas detection circuit detects the detection target gas from the electrical characteristic value of the gas sensitive body 20 in a state in which the gas sensitive body 20 is heated to the above temperature range. Gas detection becomes possible. In addition, since the heater control circuit intermittently heats the heater 21 when the combustion is stopped, the power consumption can be reduced as compared with the case where the heater 21 is continuously heated, and a period during which high power is supplied to the gas sensitive body 20. Therefore, the deterioration of the gas sensitive body 20 can be suppressed. Further, the sensitivity of the gas sensitive body 20 may change immediately after the start of energization due to the influence of moisture adhering to the gas sensitive body 20 while the energization of the heater 21 is stopped. Since the period for heating the gas sensitive body 20 is intermittently provided even during the stop, the change in sensitivity due to the influence of moisture can be suppressed by evaporating the water attached to the gas sensitive body 20.

  Further, in the above-described embodiment, the gas detection unit 14 uses both the fuel gas and the incomplete combustion gas as the detection target gas, and when the combustion is stopped, the heater control circuit has higher sensitivity to the fuel gas than when the temperature is low. The heater 21 is energized so as to periodically repeat a high temperature period, a low temperature period in which the sensitivity to the incomplete combustion gas is higher than that of the high temperature period, and a stop period in which the heater 21 is de-energized. Control is performed (see FIG. 6B).

  As described above, when the combustion is stopped, by providing a stop period in which the energization to the heater 21 is stopped, the power consumption can be reduced as compared with the case where the heater 21 is continuously heated.

  Further, in the above-described embodiment, the gas detection unit 14 sets both the fuel gas and the incomplete combustion gas as the detection target gas, and the heater control circuit at the time of combustion and when the combustion is stopped, respectively, when the sensitivity to the fuel gas is low The energization to the heater 21 is controlled so that the high temperature period in which the sensitivity is higher than the high temperature period and the low temperature period in which the sensitivity to the incomplete combustion gas is higher than the high temperature period are alternately repeated. It is also preferable to lengthen the low temperature period compared with the time of combustion.

  Thereby, the power consumption per unit time can be reduced by lengthening the low temperature period compared with the time of combustion when the combustion is stopped.

In the above-described embodiment, it is also preferable that when the gas detection unit 14 uses at least the fuel gas as a detection target gas and the gas detection unit 14 detects the fuel gas when combustion is stopped, the notification unit 16 notifies the fuel leakage. Thereby, if fuel gas is detected at the time of a combustion stop, the alerting | reporting part 16 will alert | report a fuel leak to a user by performing alerting | reporting operation | movement.

  In the above-described embodiment, when the gas detection unit 14 uses at least the fuel gas as the detection target gas and the gas detection unit 14 detects the fuel gas when the combustion is stopped, the combustion control unit causes the combustion unit 11 to ignite the fuel. It is also preferable to prohibit.

  Accordingly, when fuel leakage is detected at the time of combustion stop, ignition of the fuel is prohibited, so that the possibility of ignition of the leaked fuel can be reduced.

  In the above-described embodiment, the gas detection unit 14 includes the gas sensing body 20 using a metal oxide semiconductor, and based on the electric resistance of the gas sensing body 20 that changes according to the gas concentration of the detection target gas, Although the detection target gas is detected, if the electrical characteristic value changes in response to the detection target gas, the detection target gas may be detected based on an electrical characteristic value other than electrical resistance. Further, the gas sensitive body 20 is not intended to be limited to the metal oxide semiconductor gas sensor, and may be provided with a catalytic combustion type gas sensitive body. By providing the heating period for heating intermittently, it becomes possible to detect the detection target gas even when the combustion is stopped, and by providing the heating period intermittently, power consumption can be reduced compared to the case where the heater 21 is continuously heated. Can be reduced.

  Moreover, in this embodiment, although illustrated about the case where this invention is applied to the gas detection part of the combustion apparatus which uses city gas as fuel, gas fuel is not limited to city gas which has methane as a main component, For example, propane gas may be used. The present invention can also be applied to a gas detector for a combustion apparatus that uses liquid fuel as fuel. In this case, the gas obtained by vaporizing the liquid fuel is detected by the gas detection unit as the fuel gas. In addition to the gas fan heater exemplified in the above embodiment, the present invention can be applied to gas detection units of various combustion devices such as a gas stove, an oil fan heater, an oil stove, and a hot water supply device.

DESCRIPTION OF SYMBOLS 1 Combustion apparatus 11 Combustion part 12 Fuel supply part 14 Gas detection part 16 Notification part 20 Gas sensitive body 21 Heater 24 Signal processing circuit (heater control circuit, detection circuit)
Q1 switching element (heater control circuit)
R1, R2 load resistance (detection circuit)

Claims (5)

A combustion section for burning fuel;
A combustion control unit for controlling a combustion state of the combustion unit;
A gas detection unit for detecting the detection target gas using both the leaked fuel gas and the incomplete combustion gas generated by incomplete combustion as the detection target gas; and
A notification unit that performs a notification operation when the gas detection unit detects the detection target gas;
The gas detection unit includes a gas-sensitive member which changes its electrical characteristic value by responding to the detection target gas, a heater for heating the pre-Symbol Gas sensitive body, and a heater control circuit for controlling the energization of the heater, A detection circuit for detecting the detection target gas from an electrical characteristic value of the gas sensitive body,
When the combustion is stopped and when the combustion is stopped, the heater control circuit controls energization to the heater, so that the gas sensitive body is heated to a temperature range in which the sensitivity to the fuel gas is higher than that at the low temperature. A high temperature period and a low temperature period in which the gas sensitive body is heated in a temperature range in which sensitivity to incomplete combustion gas is higher than that in the high temperature period are periodically provided,
The heater control circuit controls energization to the heater such that a period other than the high temperature period is longer than that at the time of combustion when the combustion is stopped in a repetition cycle of the high temperature period and the low temperature period,
The said detection circuit detects the said detection target gas from the electrical characteristic value of the said gas sensitive body in each of the said high temperature period and the said low temperature period, The combustion apparatus characterized by the above-mentioned . During the combustion, the heater control circuit controls energization to the heater so that the high temperature period and the low temperature period repeat alternately,
During the combustion stop, the heater control circuit includes: the hot period, and the low-temperature period, that the suspension period for stopping the energization of the heater to control the energization of the heater to repeat periodically The combustion apparatus according to claim 1, characterized in that: Before Symbol heater control circuit, a combustion apparatus according to claim 1, wherein when the combustion is stopped, characterized in that to control the energization of the heater so as to increase the low-temperature period than during the combustion. When the gas detecting portion at the time of the combustion is stopped to detect the fuel gas, the notification section, a combustion apparatus according to any one of claims 1 to 3, wherein the notifying the leakage of fuel. The said combustion control part prohibits the ignition to the fuel by the said combustion part, if the said gas detection part detects fuel gas at the time of the said combustion stop, The any one of Claim 1 thru | or 4 characterized by the above-mentioned. Combustion device.

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