JP3879729B2 - Gas combustion equipment - Google Patents

Description

  The present invention relates to a gas combustion apparatus, and more particularly, to an automatic gas type discrimination technique in a gas combustion apparatus provided with a thermal mass flow sensor as a fuel gas flow rate measuring means.

  Gas combustion devices that use gas as fuel (for example, water heaters and bath tubs) use a flow rate control valve that adjusts the fuel gas supply amount by varying the passage area of the gas supply path for combustion control. Has been proposed. (For example, refer to Patent Document 1).

  By the way, in the gas combustion apparatus having such a configuration, a mass flow sensor is provided to measure the gas flow rate in the gas supply path, but the mass flow sensor is a sensor whose flow rate output value differs depending on the gas type. Since it has characteristics, it is necessary to specify the gas type before starting the operation of the gas combustion apparatus.

  Therefore, in the conventional gas combustion apparatus, as a method for discriminating such gas type, for example, the burner is burned while maintaining the flow control valve at a constant opening, and the combustion amount at that time (that is, the tapping temperature, the incoming water temperature, and the incoming water amount) The amount of heat required to generate hot water based on the above) is determined, and the gas type is determined based on this amount of heat and known data (such as the amount of heat generated per unit volume of each gas type and the passage area of the pipe). ing.

Japanese Utility Model Publication No. 5-79240

  However, the conventional gas combustion apparatus having such a configuration has the following problems, and improvements have been desired.

  That is, in the gas type discrimination method as described above, it is necessary to burn the burner to obtain the temperature difference between the incoming water temperature and the outgoing hot water temperature, and a certain amount of gas must be supplied to the burner. However, in this type of combustion apparatus, since the sensor output value of the mass flow sensor is normally used for combustion control, the gas type is not determined in the above method (that is, the sensor output characteristic is undetermined). This is not preferable because it causes a combustion operation.

  The present invention has been made in view of such conventional problems, and an object of the present invention is to perform a function that can perform gas type discrimination surely and quickly and perform optimum combustion control according to the discrimination result. An object is to provide a gas combustion apparatus provided.

In order to achieve the above object, a gas combustion apparatus according to the present invention includes a heater in a fuel gas supply path to a burner, a detection unit having temperature sensors disposed on both sides thereof, an ambient temperature sensor for detecting ambient temperature, In the gas combustion apparatus having a thermal mass flow sensor that is controlled so that the heater temperature rise value becomes constant by the heater voltage, voltage detecting means for detecting the heater voltage, and fuel gas gas Gas for determining the fuel gas type by comparing the storage means storing the data indicating the relationship between the species and the heater voltage, and comparing the voltage detection value detected by the voltage detection means with the data stored in the storage means Rutotomoni a species discriminating means, interruptible formed with the ignition means for igniting the burner, the ignition detecting means for detecting the ignition of the burner, the supply of fuel gas to the burner And when the ignition detecting means detects ignition during the ignition operation by the ignition means, the fuel cutoff means cuts off the supply of the fuel gas and the fuel type discrimination means It is characterized by performing gas type discrimination .

  Preferably, in addition to the above configuration, the gas type discrimination by the gas type discrimination means is performed after the combustion of the burner is stopped.

  Furthermore, it is characterized by comprising combustion control means for performing combustion control suitable for the gas type based on the discrimination result of the gas type discrimination means.

  And as an embodiment of the combustion control means, the combustion control means comprises a control table showing the correlation between the sensor output of the thermal mass flow sensor and the calorific value for each gas type, and the gas type Combustion control is performed by selecting the control table suitable for the gas type based on the determination result of the determination means.

  As another embodiment, the combustion control means includes a first relational expression indicating a correlation between a heater voltage and thermal conductivity of the thermal mass flow sensor, and the thermal conductivity and the calorific value ratio. A second relational expression indicating a correlation is provided for each gas type, and the first and second relational expressions are selected based on the determination result of the gas type discrimination means, and the calorific value ratio is determined from these relational expressions. And a control structure for calculating the calorific value of the fuel gas actually supplied to the burner from the calorific value ratio and the sensor output of the thermal mass flow sensor.

  In another embodiment, when setting the first relational expression and the second relational expression, a group of gas species having the same or similar correlation with respect to at least one of these relational expressions. It is preferable that a single relational expression is prepared for each grouped gas type and the relational expression is selected according to the determination result of the gas type determination means.

  According to the present invention, in the gas combustion apparatus provided with the thermal mass flow sensor in the fuel gas supply path to the burner, the voltage detection means for detecting the heater voltage of the mass flow sensor, the gas type of the fuel gas and the heater Storage means for storing data indicating a voltage relationship, and gas type determination means for comparing the voltage detection value detected by the voltage detection means with the data stored in the storage means to determine the gas type of the fuel gas. Therefore, it is possible to automatically determine the gas type without a gas type setting operation by a person, and to perform the gas type determination reliably and quickly.

  In addition, since the gas type determination by the gas type determination means is performed by interrupting the supply of the fuel gas after the ignition is detected during the ignition operation to the burner, an erroneous determination due to mixing of gas other than the fuel gas is avoided and accurate. The gas type can be determined.

  Furthermore, by performing the gas type discrimination during the ignition operation, it is possible to automatically cope with the change of the gas type. In addition, by providing combustion control means for performing combustion control suitable for the gas type based on the determination result of the gas type determination means, a user-friendly gas combustion apparatus can be provided.

  In particular, the first relational expression showing the correlation between the heater voltage and the thermal conductivity of the thermal mass flow sensor in the combustion control means, and the second relational expression showing the correlation between the thermal conductivity and the calorific value ratio, For each gas type or a group of gas types having a common correlation, and the first and second relational expressions are selected based on the determination result of the gas type discrimination means, and the calorific value is calculated from these relational expressions. By providing a control configuration for calculating a ratio and calculating a calorific value (actual calorific value) of the fuel gas actually supplied to the burner from this calorific value ratio and the sensor output of the thermal mass flow sensor, The combustion control means can adjust the gas flow rate and the air amount for optimum combustion based on the actual calorific value, and can realize highly accurate combustion control.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

Embodiment 1
FIG. 1 shows a case where the gas combustion apparatus of the present invention is applied to a water heater. As shown in the figure, the water heater 1 is provided with a burner 2 using gas as fuel in its main body, and a heat exchanger 3 configured to be heated by the burner 2 is provided above the burner 2. . A blower fan 4 for supplying air to the burner 2 is provided below the burner 2.

  A water supply pipe 5 is connected to the water inlet side of the heat exchanger 3, and a hot water pipe 6 is connected to the hot water side. The water supply pipe 5 has a water inlet temperature Ta to the heat exchanger 3. An incoming water temperature sensor (incoming water temperature detecting means) 7 for detecting and an incoming water amount sensor (incoming water amount detecting means) 9 for detecting the incoming water amount Q are provided. The tapping pipe 6 is provided with a tapping temperature sensor (tapping temperature detecting means) 8 that detects a tapping temperature Tb of hot water heated by the heat exchanger 3.

  On the other hand, a gas pipe 10 for supplying fuel gas to the burner 2 is connected to the burner 2. The gas pipe 10 is connected to a gas supply source (for example, a gas pipe for supplying city gas for city gas, a gas cylinder for propane gas, etc.), and constitutes a fuel gas supply path to the burner 2. ing.

  The gas pipe 10 includes a gas flow rate sensor 11 for detecting the flow rate V of the fuel gas, a gas flow rate control valve 12 for adjusting the flow rate V of the fuel gas supplied to the burner 2, and supply of the fuel gas to the burner 2. An original gas solenoid valve (fuel cutoff means) 13 configured to be capable of shutting off is provided.

  Here, in the present embodiment, a thermal mass flow sensor that detects the mass flow rate of the fluid flowing in the gas pipe 10 is suitably used as the gas flow sensor 11. As shown in FIG. 2 (a), the gas flow sensor 11 is a heater that raises the temperature of a fluid to be measured at a constant temperature on a base 101 having an insulating film layer formed on the surface of a silicon chip as a detector. The heater resistance Rh as a temperature sensor, the upstream temperature sensor resistance Ru and the downstream temperature sensor resistance Rd as temperature sensors disposed on both upstream and downstream sides in the fluid passage direction across the heater resistance Rh, and the upstream temperature An ambient temperature sensor resistance Rr as a temperature sensor for detecting an ambient temperature (in other words, a fluid temperature) is disposed further upstream of the sensor resistance Ru.

  Each of these resistors Rh, Ru, Rd, Rr employs a resistor whose resistance value changes according to temperature (for example, platinum resistor), and although not shown, the heater resistor Rh and the upstream and downstream temperature sensors. Silicon at the center of the base 101 on which the resistors Ru and Rd are provided is removed by etching or the like, and a diaphragm structure in which these resistors are thermally insulated from the base 101 is obtained.

  By the way, the specific configuration (particularly, the configuration of the temperature detection circuit using the temperature sensor resistances Ru and Rd) and the operation principle of the thermal mass flow sensor configured as described above are well known, and a detailed description thereof will be given here. Although omitted, in this type of gas flow sensor 11, the heater resistance Rh and the ambient temperature sensor resistance Rr constitute a bridge circuit as shown in FIG. 2B, and the bridge voltage (heater voltage) of this circuit is set. The amount of heat generated by the heater resistor Rh is controlled by controlling with the operational amplifier OP (heater control circuit). Specifically, the heater voltage is controlled so that the heater resistance Rh compensates for the heat taken away by the surrounding gas, and is applied so that the heater temperature rise value becomes constant.

  For this reason, in this type of gas flow sensor 11, for example, when a gas (gas) having high thermal conductivity comes into contact with the heater resistance Rh, the amount of heat diffused from the heater to the gas side increases. On the other hand, when it comes into contact with a gas (gas) having a low thermal conductivity, it has a characteristic that the heater voltage decreases because of less heat diffusion to the gas side. In the present invention, the gas type is discriminated by making use of the characteristics of such a sensor, details of which will be described later.

  The gas flow rate control valve 12 is constituted by a proportional valve that controls the flow rate of the fuel gas by operating the valve body and changing the opening area of the valve seat, such as a needle valve. That is, the amount of gas supplied to the burner can be adjusted by changing the cross-sectional area (passage area) of the fuel gas supply path by adjusting the opening of the valve.

  The gas solenoid valve 13 is composed of an open / close solenoid valve that switches between opening and closing of the gas supply path, and is arranged upstream of the gas flow sensor 11 as shown in the figure, and the fuel gas is supplied to the burner 2 by closing the valve body. It is configured to be able to shut off.

  Further, an igniter (ignition means) 14 for igniting the burner 2 and a frame rod (ignition confirmation means) 15 for detecting ignition (presence / absence of flame) are provided in the vicinity of the burner 2. Yes. In addition, since these structures and arrangement | positioning are well-known, detailed description is abbreviate | omitted.

  The controller 16 constitutes a control means for controlling the operation of each part of the water heater 1, and specifically, for executing various controls and processes such as combustion control and gas type discrimination process described later. A microcomputer is the main part. In the present embodiment, when the controller 16 is configured based on its function, the controller 16 includes a combustion control means 20, a gas type determination means 21, and a storage means 22, as shown in FIG. The 16 functions will be described later.

  As shown in FIG. 1, the controller 16 outputs signals from the water temperature sensor 7, the hot water temperature sensor 8, the water amount sensor 9, the gas flow rate sensor 11, the frame rod 15 and the like as indicated by broken lines in the figure. Connected through a line. Similarly, the controller 16 is connected to the blower fan 4, the gas flow rate control valve 12, the original gas solenoid valve 13, the igniter 14 and the like through signal lines indicated by broken lines, and control signals for controlling the operation thereof. Can be output.

  Therefore, the operation of the water heater 1 configured as described above will be described with reference to FIGS. 3 and 4. 3 shows a functional block diagram of the water heater 1 according to the present invention, and FIG. 4 is a flowchart showing an example of the procedure of the gas type discrimination process. In FIG. 3, reference numeral S denotes an operation unit such as a remote controller.

  When an operation start operation is performed at the operation unit S, and the tip plugs are opened in this state, and water flow exceeding the minimum operating water flow rate occurs in the water heater 1 (see step S1 in FIG. 4), the combustion control means of the controller 16 The ignition operation is started by 20 (see step S2 in FIG. 4).

  This ignition operation refers to a series of processes for opening the original gas solenoid valve 13 and the gas flow rate control valve 12 to operate the igniter 14. This ignition operation is repeated until flame is detected by the frame rod 15. (See step S3 in FIG. 4). This is because even when both the original gas solenoid valve 13 and the gas flow rate control valve 12 are opened when the gas pipe 10 is filled with air (for example, after the completion of the gas pipe connection work). This is because the amount of fuel gas required for ignition does not come out of the burner 2 and the ignition operation is performed until the amount of fuel gas required for ignition comes out of the burner 2.

  When the flame (ignition) in the burner 2 is detected by the frame rod 15, the controller 16 next executes a process for closing the original gas solenoid valve 13 (see step S4 in FIG. 4). The supply of the fuel gas to 2 is stopped, and the gas type determination process (the processes of steps S5 and S6 in FIG. 4) is started. That is, the gas type determination process (the processes of steps S5 and S6 in FIG. 4) is performed in a state where the ignited flame is once extinguished.

  Here, the reason why the ignited flame is once extinguished and the next process is performed is that the fuel gas is filled in the gas pipe 10 when the burner 2 is ignited. This is to stop the flow of the fuel gas by closing the valve, that is, to perform the gas type discrimination in a state where the fuel gas is filled in the gas pipe 10.

  When the closing process of the original gas solenoid valve 13 is completed, the controller 16 next measures the heater voltage in the heater control circuit of the gas flow sensor 11 (see step S5 in FIG. 4). The heater voltage is measured through voltage detection means (not shown), and the detection result is input to the controller 16 (specifically, the gas type determination means 21).

  When the heater voltage in the heater control circuit of the gas flow sensor 11 is measured in this manner, the value of the heater voltage is then corrected by the ambient temperature measured by the ambient temperature sensor in the gas type discrimination means 21. The corrected value is compared with the data stored in the storage means 22 to determine the gas type of the fuel gas.

  That is, as described above, since the heater voltage of the heater control circuit differs depending on the thermal conductivity of the gas to be measured, the heater voltage for each gas type (hereinafter referred to as the reference heater voltage) is stored in the storage means 22 in advance. Is stored as data, and the heater voltage value measured in step S5 in FIG. 4 (specifically, the value after temperature correction) and the reference heater voltage value stored in the storage means 22 are stored. The gas type is determined by comparison. In other words, it is determined that the gas type has the reference heater voltage indicating the same value as the heater voltage after temperature correction measured in step S5 in FIG.

  FIG. 5 shows an example of such data. Specifically, the data shown in FIG. 5 represents the reference heater voltage on the vertical axis and the gas type on the horizontal axis, and indicates the reference heater voltage for each gas type when the flow rate is zero. Further, in the illustrated example, data of seven types of fuel gas, 13A-0, 13A-1, 12A-3, air propane, 12A-2, C3H8, and C4H10, are shown as gas types.

  That is, in this embodiment, the original gas solenoid valve 13 is closed in step S4 in FIG. 4 (that is, the flow rate in the gas pipe 10 is made zero), and the heater voltage of the gas flow rate sensor 11 is measured. Therefore, the reference heater voltage data stored in the storage means 22 uses the same conditions, that is, data for each gas type when the flow rate is zero.

  Regarding this point, if the heater voltage of the gas flow sensor 11 actually measured and the reference heater voltage for each gas type can be compared (both have the same flow rate), the data of the reference heater voltage Is not limited to that when the flow rate is zero. That is, the flow rate of the fuel gas is set to a constant flow rate (constant flow rate) with the gas flow rate control valve 12 without closing the original gas solenoid valve 13 in step S4 in FIG. It is also possible to use the data acquired below as the reference heater voltage.

  When the gas type is determined in step S6 in FIG. 4, thereafter, the combustion control means 20 normally uses a combustion control table (control table) suitable for the gas type based on the determination result of the gas type determination. Is started (see step S7 in FIG. 4).

  That is, the combustion control means 20 performs the ignition operation again and becomes a target from the target temperature To, the incoming water temperature Ta, and the incoming water amount Q so that hot water can be discharged at the target temperature To set by the operation unit S. While calculating the combustion amount (target heat generation amount) of the burner 2, the above determination is made from a control table (a table showing the correlation between the sensor output (gas flow rate) of the flow sensor 11 and the heat generation amount) provided for each gas type. The control table corresponding to the gas type obtained as a result is selected, and the valve opening degree of the gas flow rate control valve 12 is adjusted and controlled so that the target calorific value is obtained by the burner 2. Along with this, the rotational speed of the blower fan 4 is controlled so that an optimal combustion state is obtained by the burner 2.

  As described above, in the water heater of the present invention, the gas type discrimination means automatically discriminates the gas type of the fuel gas at the time of ignition operation. Species determination can be performed. In particular, since the measurement of the heater voltage only takes about 20 milliseconds, the above-described processing from step S1 to step S6 in FIG. 4 is performed in a time that is almost the same as the ignition operation in a general water heater. The water heater user can normally use the water heater without being aware that the gas type determination is performed.

  Further, after the ignition to the burner 2 is confirmed, the combustion is temporarily stopped and the gas type determination is performed. Therefore, the gas type determination can be performed in a state where the gas gas is filled in the gas pipe 10, and a gas other than the fuel gas ( Misjudgment due to air) can be avoided, and the gas type can be accurately determined.

Embodiment 2
Next, a second embodiment of the present invention will be described with reference to FIGS. This second embodiment is a modification of the control configuration of the combustion control in the combustion control means 20, and other configurations (basic configuration of the water heater 1 and the above-described gas type discrimination procedure) are the above-described embodiments. Same as 1. Accordingly, parts having the same configuration are denoted by the same reference numerals and description thereof is omitted.

  That is, in the first embodiment described above, the combustion control means 20 includes a plurality of control tables according to the gas type, and performs the combustion control by selecting a control table suitable for the gas type according to the gas type discrimination result. In this embodiment, the combustion control means 20 includes first and second relational expressions described later without using the control table as described above, and these relational expressions and the sensor of the gas flow rate sensor 11. The calorific value (actual calorific value) of the fuel gas actually supplied to the burner 2 is calculated from the output (gas flow rate), and the gas flow rate is set so that the burner 2 can burn the target calorific value based on the calculation result. The control valve 12 and the fan motor (not shown) of the blower fan 4 are configured to be controlled.

  Specifically, the above relational expression is the first relational expression showing the correlation between the heater voltage of the gas flow sensor 11 and the thermal conductivity of the fuel gas, and the correlation between the thermal conductivity of the fuel gas and the calorific value ratio. It consists of a second relational expression indicating the relation.

  By the way, regarding the first and second relational expressions, the applicant of the present application relates to the correlation between the heater voltage of the gas flow sensor 11 and the thermal conductivity of the fuel gas for typical gas types used in Japan. When the correlation between the thermal conductivity of the fuel gas and the calorific value ratio was measured, the relational expressions indicating these correlations were all expressed by linear expressions, and the gas types with the same or similar correlations. It became clear that existed. It has also been found that when the gas types having the same or similar correlation are collected as a group of gas types, they are roughly classified into the following three groups.

1st group A: 13A-1, 13A-3, 12A-3 mainly composed of methane, city gas of typical gas company specifications, etc. 2nd group B: gas with many hydrogen components such as 13A-2 3rd group C : LP gas, C4H10, propane air 13A, etc.

    Therefore, in the present embodiment, in setting the first and second relational expressions, one relational expression (that is, one relational expression for each group) for a group of gas species having the same or similar correlation. It was decided to use. An example is shown in FIG. FIG. 6A is a graph showing the correlation between the heater voltage of the gas flow sensor 11 and the thermal conductivity of the fuel gas, and FIG. 6B is a graph showing the fuel gas. The graph shows the correlation between the thermal conductivity and the calorific value ratio.

  In this way, the combustion control means 20 of the water heater 1 shown in the present embodiment includes the first group A to the third group C 3 as the first and second relational expressions as shown in FIG. A seed relational expression is stored.

  Then, the procedure of the combustion control using the first and second relational expressions will be described based on the flowchart of FIG. Since the procedure until the gas type determination is completed as described above is the same as that in the first embodiment described above, the description of the procedure up to that point is omitted here.

  That is, in this embodiment, when the gas type determination is performed as shown in step S1 of FIG. 7, the combustion control means 20 selects the first and second relational expressions according to the result of the gas type determination. The For example, when the gas type determination result is 13A-3 gas, the 13A-3 gas belongs to the first group A. Therefore, the combustion control means 20 uses the first and second relational expressions as follows. In FIG. 7, the relational expression indicating the first group A is selected.

  When the relational expression is selected in this way, the combustion control means 20 next causes the gas flow rate sensor 11 of the gas flow rate sensor 11 at the time of the gas type determination (that is, the gas pipe 10 is filled with fuel gas and the flow rate is zero). The thermal conductivity of the fuel gas (here, 13A-3 gas) is calculated from the heater voltage (voltage after temperature correction) and the first relational expression (see step S3 in FIG. 7), and further obtained by calculation. The calorific value ratio of the fuel gas is calculated from the thermal conductivity and the second relational expression (see step S4 in FIG. 7).

  On the other hand, as described above, in the present embodiment, since the gas type determination is performed at the time of the ignition operation to the burner 2, the combustion control means 20 opens the original gas electromagnetic valve 13 again and performs the ignition operation after the gas type determination. The combustion operation is started (see step S5 in FIG. 7). As a result, the fuel gas flows again into the gas pipe 10, so that the combustion control means 20 detects the sensor output (gas flow rate) from the gas flow rate sensor 11 as shown in step S6 of FIG. Is multiplied by the above calorific value ratio to calculate the actual calorific value of the fuel gas actually supplied to the burner 2 (see step S7 in FIG. 7).

  During the combustion operation, the gas flow rate control valve 12 is controlled based on the actual calorific value thus obtained so that the actual calorific value coincides with the target calorific value (see step S8 in FIG. 7). The fan motor of the blower fan 4 is controlled so that optimum combustion can be performed by the burner 2 (see step S9 in FIG. 7).

  That is, in the present embodiment, the combustion control means 20 applies the burner 2 to the burner 2 based on the gas type determination result, the first and second relational expressions, and the detection value (gas flow rate) of the gas flow rate sensor 11. A control configuration for calculating the actual calorific value of the supplied fuel gas is provided, and the necessary gas amount and air amount are determined based on the actual calorific value, so that optimal combustion control can be performed.

  In addition, since both the first and second relational expressions are expressed by linear expressions, appropriate combustion control can be performed without having a complicated and enormous data amount control table.

  That is, in the configuration in which the combustion control means 20 is provided with the control table for each gas type as shown in the first embodiment described above, the correlation between the gas flow rate and the calorific value draws a curved characteristic. If a control table is provided for all of the representative gas types used in the above, the table size (data amount) will become enormous. Therefore, in practice, only a certain number of control tables can be provided (to the extent that the table size does not become excessive), and the gas type of the fuel gas actually supplied to the burner 2 does not match the control table. In some cases, proper combustion control cannot be performed.

  On the other hand, in this embodiment, since it is only necessary to set a relational expression for each gas type having common characteristics, the amount of data stored in the combustion control means 20 can be very small, and the first and second data can be stored. Are expressed by a linear expression (that is, the characteristic is linear). Therefore, if the gas type determination is performed at the initial stage of the combustion start of the burner 2, the first and the following are then performed according to the gas type. By simply selecting the second relational expression, it is possible to perform appropriate combustion control according to the introduced gas component based on the linear characteristics.

  Note that the above-described embodiments merely show preferred embodiments of the present invention, and the present invention is not limited to these, and various design changes can be made within the scope thereof.

  For example, in the above-described embodiment, the determination of the gas type is performed during the ignition operation. However, for example, the gas type determination process (the processes of steps S5 and S6 in FIG. 4) is performed after the combustion is stopped. You can also. Moreover, the gas type determination at the time of the ignition operation described above can be performed only at the time of construction of the gas combustion apparatus, or can be performed at every ignition operation after the construction. Further, it is possible to make a gas type determination every predetermined time.

  Further, in the above-described embodiment, the case where the so-called flow control type gas flow control valve 12 is used as the valve device for adjusting the adjustment of the fuel gas supply amount is shown. For example, the present invention can also be applied to a water heater using a pressure control type valve device.

  In the above-described embodiment, the original gas electromagnetic valve 13 is used as the fuel cutoff means. However, if the flow of the fuel gas in the gas pipe 10 can be stopped, another valve device (for example, the gas flow control valve 12). May be used.

  Moreover, although the case where this invention was applied to the water heater was shown in embodiment mentioned above, this invention is applicable also to gas combustion apparatuses other than a water heater (for example, a bathtub, a gas stove, etc.).

  In the second embodiment described above, the first and second relational expressions are set by classifying the gas types of the fuel gas into three groups from the first group A to the third group C. The classification of the first and second relational expressions can be changed as appropriate. In short, it should be classified so that one relational expression is set for each gas type having the same or similar correlation. Further, the above relational expressions can be provided for each gas type.

It is explanatory drawing which shows schematic structure of the water heater to which the gas combustion apparatus which concerns on this invention is applied. It is explanatory drawing of the thermal mass flow sensor used for the water heater, Comprising: Fig.2 (a) is a schematic structure of the detection part of the sensor, FIG.2 (b) is an example of the heater control circuit of the sensor Show. It is a functional block diagram explaining the function of the water heater. It is a flowchart which shows an example of the gas type discrimination | determination procedure of the water heater. FIG. 5 is a diagram showing an example of gas type discrimination data used in the gas type discrimination procedure of FIG. FIG. 6A is a graph showing the relational expression in the second embodiment of the present invention, and FIG. 6A is a first relational expression showing the correlation between the heater voltage of the gas flow sensor and the thermal conductivity of the fuel gas. FIG. 6B shows a second relational expression showing the correlation between the thermal conductivity of the fuel gas and the calorific value ratio. It is a flowchart which shows the procedure of the combustion control in 2nd embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Water heater 2 Burner 3 Heat exchanger 4 Blower fan 5 Water supply pipe 6 Hot water outlet pipe 7 Water inlet temperature sensor 8 Hot water temperature sensor 9 Water quantity sensor 10 Gas pipe 11 Gas flow sensor 12 Gas flow control valve 13 Original gas solenoid valve )
14 Igniter (ignition means)
15 Frame rod (ignition detection means)
16 Controller 20 Combustion control means 21 Gas type discrimination means 22 Storage means A First group of gas types (relational expression thereof)
B Second group of gas types (relational expression)
C Group 3 gas types (relational formulas)

Claims (6)

The fuel gas supply path to the burner has a heater, a detection unit having temperature sensors arranged on both sides thereof, and an ambient temperature sensor for detecting the ambient temperature, and the heater voltage has a constant temperature rise value. In a gas combustion apparatus equipped with a thermal mass flow sensor that is controlled to be
Voltage detection means for detecting the heater voltage, storage means for storing data indicating the relationship between the gas type of the fuel gas and the heater voltage, a voltage detection value detected by the voltage detection means, and the storage means and ignition means for comparing the data Rutotomoni and a gas type determining means for determining the gas type of the fuel gas, to ignite the burner, the ignition detecting means for detecting the ignition of the burner, the burner Fuel cutoff means configured to be able to shut off the supply of fuel gas to
During the ignition operation by the ignition means, when the ignition detection means detects ignition, the fuel cutoff means shuts off the supply of fuel gas, and the gas type discrimination means executes the gas type discrimination of the fuel gas. A gas combustion apparatus characterized by that. The gas combustion apparatus according to claim 1 , wherein the gas type discrimination by the gas type discrimination means is executed after the combustion of the burner is stopped. The gas combustion apparatus according to claim 1, further comprising a combustion control unit that performs combustion control in accordance with a gas type based on a determination result of the gas type determination unit. The combustion control means is provided with a control table showing the correlation between the sensor output of the thermal mass flow sensor and the calorific value for each gas type, and matches the gas type based on the determination result of the gas type determination means. The gas combustion apparatus according to claim 3 , wherein combustion control is performed by selecting the control table. The combustion control means includes a first relational expression showing a correlation between a heater voltage and a thermal conductivity of the thermal mass flow sensor, and a second relation showing a correlation between the thermal conductivity and a heating value ratio. Formula for each gas type,
Based on the determination result of the gas type determination means, the first and second relational expressions are selected to calculate a calorific value ratio from these relational expressions, and the calorific value ratio and the sensor output of the thermal mass flow sensor. The gas combustion apparatus according to claim 3 , further comprising: a control configuration that calculates a calorific value of the fuel gas that is actually supplied to the burner. When setting the first relational expression and the second relational expression, for at least one of these relational expressions, the gas types having the same or similar correlation are grouped together as a group of gas types, and the group of grouped groups 6. The gas combustion apparatus according to claim 5 , wherein one relational expression is prepared for each gas type, and the relational expression is selected according to a determination result by the gas type determination means.

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