JP6822103B2 - Hot water supply device and control method of hot water supply device - Google Patents

Description

The disclosure relates to a method of controlling a hot water supply device and a hot water supply device, and more particularly to a method of controlling a hot water supply device and a hot water supply device that controls combustion of a burner to heat a heat exchanger.

Regarding the combustion control of the gas burner, for example, in Patent Document 1 (Japanese Unexamined Patent Publication No. 10-253157), a part of combustion in the burner is performed when the hot water supply is stopped in order to suppress a decrease in the hot water discharge temperature at the time of re-delivery. Discloses the control means for stopping the combustion after the burner has been burned for a predetermined time when the burner has been burned for a predetermined time.

Further, in Patent Document 2 (Japanese Unexamined Patent Publication No. 2000-240939), the maximum OFF time of the burner is set in advance corresponding to each division of the output range of the temperature controller, and is calculated by the normal cycle time and the output signal. When the OFF time exceeds the maximum OFF time corresponding to the above classification, the cycle time when the maximum OFF time is set is calculated, and the burner ON-OFF control is performed based on the calculated cycle time and the maximum OFF time. Disclose the configuration that implements.

Japanese Unexamined Patent Publication No. 10-253157 Japanese Unexamined Patent Publication No. 2000-24039

Conventionally, the gas hot water supply device maintains the hot water temperature at the set temperature by measuring the temperature of the hot water in the hot water supply device and controlling the combustion of the burner based on the measured temperature and the set temperature.

However, when combustion control is performed using the measured temperature, it may be difficult to stably maintain the hot water temperature at the set temperature. For example, when the water supplied to the hot water supply device has preheating (hereinafter, also referred to as “water supply preheating”), the water supply temperature changes, and the response of the heating control to the change in the water supply temperature may be delayed. There is a delay in the output of the command for controlling the gas burner (command of "required number" described later). As a result, there is a problem that the hot water temperature exceeds the set temperature (overshoots or undershoots). However, none of the above patent documents proposes a method of dealing with the problem.

Therefore, an object of the present disclosure is to provide a hot water supply device and a control method for the hot water supply device that control combustion so as to obtain an appropriate hot water outlet temperature.

The hot water supply device according to a certain aspect of the present disclosure includes a heating unit including a heat exchanger, a burner for heating the heat exchanger, a flow rate sensor for measuring the flow rate of hot water in a flow path passing through the heating unit, and a hot water supply device. It includes a control unit for controlling.

The control unit requests to acquire the required amount of heat for heating the heat exchanger from the target temperature value of the heating unit, the input temperature value of hot water input to the heating unit from the water input path, and the flow rate value measured by the flow sensor. A heat quantity acquisition unit, a heating command unit that outputs a heating command for burning the burner, a predicted heat quantity acquisition unit that acquires the predicted heat quantity generated by combustion of the burner according to the heating command, and a heat treatment unit that controls the heating command unit. And, including.

The heat treatment unit controls the heating command unit to output a combustion stop command when the required heat amount is equal to or less than the minimum heat amount corresponding to the minimum combustion capacity of the burner and the predicted heat amount is larger than the required heat amount. Moreover, when the predicted heat quantity is equal to or less than the required heat quantity, the heating command unit is controlled so as to output a combustion command for generating the minimum heat quantity.

Preferably, the heat exchanger comprises a primary heat exchanger that recovers sensible heat and a secondary heat exchanger that recovers latent heat, the outlet of the secondary heat exchanger being connected to the inlet of the primary heat exchanger. To. The hot water supply device further includes a temperature sensor that measures the temperature of hot water input from the water entry path. The control unit estimates the temperature value of the hot water at the outlet of the secondary heat exchanger based on the measured temperature value and the measured flow rate value by the temperature sensor, and the incoming water temperature value for obtaining the required heat amount is the measured temperature value and the second. The lower of the estimated temperature values at the outlet of the secondary heat exchanger.

Preferably, the water heater further includes a pipe connected to a hot water tap and a distribution valve for distributing a part of the total amount of water supplied to the water heater to the pipe. The opening degree of the distribution valve indicates the ratio of the diversion to the pipe to the total water supply amount. The control unit calculates the target temperature value for controlling the heating unit based on the set temperature value, the incoming water temperature value, and the ratio, and the target temperature value for acquiring the required heat amount is the set temperature value. It is the lower of the calculated target temperature values.

Preferably, when the combustion stop command is output, the heat treatment unit controls the heating command unit so that the combustion stop of the burner continues for at least a predetermined time.

Preferably, the predicted heat quantity acquisition unit acquires the predicted heat quantity y [n] according to y [n] = ((L × y [n-1]) + x [n]) / (L + 1) for each cycle [n]. Then, x [n] indicates the amount of heat required by the heating command output in the period [n], and L indicates the time constant.

Preferably, the time constant indicated by L is changed according to the change tendency of the incoming water temperature and the measured flow rate value.
According to other aspects of the invention, a method of controlling a water heater is provided. The hot water supply device includes a heating unit including a heat exchanger and a burner for heating the heat exchanger. The control method consists of a step of acquiring the required amount of heat for heating the heat exchanger from the target temperature value of the heating unit, the inflow temperature value of hot water input to the heating unit, and the flow rate value passing through the heating unit. It includes a step of outputting a heating command for burning the burner and a step of acquiring a predicted amount of heat generated by burning the burner according to the heating command. In the step of outputting the heating command, when the required heat quantity is equal to or less than the minimum heat quantity corresponding to the minimum combustion capacity of the burner, and when the predicted heat quantity is larger than the required heat quantity, a combustion stop command is output and the predicted heat quantity is When it is less than the required heat quantity, a combustion command to generate the minimum heat quantity is output.

According to the present disclosure, it is possible to control the combustion of the burner so that the hot water temperature becomes appropriate.

It is a schematic block diagram of the hot water supply apparatus according to embodiment of this invention. It is a block diagram which shows schematic the functional structure of the controller 300. It is a figure for demonstrating the intermittent operation which concerns on Embodiment 1. FIG. It is a figure for demonstrating the intermittent operation which concerns on Embodiment 1. FIG. It is a schematic processing flowchart of the combustion control which concerns on Embodiment 1. FIG. It is a processing flowchart of intermittent operation which concerns on Embodiment 1. FIG. It is a figure explaining the time constant L which concerns on Embodiment 3. (A) and (B) are diagrams for explaining the fourth embodiment. It is a figure explaining the operation of the hot water supply device 100 at the time of intermittent operation by each embodiment. It is a figure which shows the relationship of (required heat quantity and present output) or (can body set temperature and present can body temperature) during intermittent operation. It is a figure for demonstrating the advantage of each embodiment. It is a figure for demonstrating the advantage of each embodiment. It is a figure for demonstrating the advantage of each embodiment. It is a figure for demonstrating the advantage of each embodiment.

Embodiments of the present disclosure will be described in detail with reference to the drawings. In each figure, the same reference numerals indicate the same or corresponding parts.

In this specification, in the hot water supply device, the amount of heat (Kcal) generated by the combustion of the gas burner is indicated by "number". The number = 1 corresponds to the amount of heat required to raise the hot water temperature by a predetermined temperature (for example, 25 ° C.) under a flow rate of 1 (L / min).

[Overview]
Summarizing each embodiment, the required amount of heat required to heat the heat exchanger in the hot water supply device (hereinafter, also referred to as “required number”) is the minimum combustion capacity of the burner (hereinafter, “minimum number”). The control unit controls the burner so as to perform intermittent operation when the amount of heat is equal to or less than the minimum amount of heat corresponding to the number. Specifically, the burner is controlled so as to stop combustion when the predicted heat quantity is larger than the above required heat quantity, and the minimum calorific value is set when the predicted heat quantity for predicting the output of the primary heat exchanger is less than the required heat quantity. Control the burner to generate and burn. The above predicted heat quantity indicates the heat quantity predicted to be output from the primary heat exchanger due to the combustion of the burner.

According to the above-mentioned hot water supply device, intermittent operation by switching between combustion of the burner or combustion stop is possible according to the magnitude relationship between the required heat quantity and the predicted heat quantity.

By carrying out the above-mentioned intermittent operation, it is possible to obtain a calorific value in a low number range of "minimum number" or less in the hot water supply device. As a result, heating control (output of the heating command) that follows the change in the water entry temperature to the heat exchanger becomes possible in the low number range, and the hot water outlet temperature can be maintained at the set temperature in the low number range. ..

[Embodiment 1]
(Configuration of water heater)
FIG. 1 is a schematic configuration diagram of a hot water supply device according to an embodiment of the present invention. With reference to FIG. 1, the hot water supply device 100 includes a heating unit 20, a gas burner 30, a combustion can body (hereinafter, also simply referred to as “can body”) 10 for storing the heating unit 20, a blower fan 40, a water inlet pipe 50, and a bypass. It includes a pipe 60, a hot water pipe 70, and a controller 300. The heating unit 20 is a portion that heats and sends out hot water by the amount of heat generated by combustion of the gas burner 30, and includes a primary heat exchanger 11 that recovers sensible heat and a secondary heat exchanger 21 that recovers latent heat. The outlet of the secondary heat exchanger 21 is connected to the inlet of the primary heat exchanger 11.

A bypass pipe 60 is arranged between the water inlet pipe 50 and the hot water outlet pipe 70. The water inlet pipe 50 is an embodiment of the “water entry route” for inputting hot water to the heating unit 20. A distribution valve 80 for controlling the diversion to the bypass pipe 60 is inserted and connected to the water inlet pipe 50. Further, a temperature sensor 110 and a flow rate sensor 150 are arranged in the water inlet pipe 50. The temperature sensor 110 detects the entry temperature Tw. A part of the amount of water supplied to the hot water supply device 100 is diverted from the water inlet pipe 50 to the bypass pipe 60 according to the opening degree of the distribution valve 80. The ratio of the diversion to the total water supply amount is controlled according to the opening degree of the distribution valve 80. Tap water or hot water from an external device may be supplied to the water inlet pipe 50. In the first embodiment, the external device that can be connected to the water inlet pipe 50 includes, for example, a fuel cell power generation unit.

The hot water from the water inlet pipe 50 is preheated by the secondary heat exchanger 21 inserted in the water inlet path, and then mainly heated in the primary heat exchanger 11. The hot water heated by the primary heat exchanger 11 and the secondary heat exchanger 21 is discharged from the hot water tap 190 of the kitchen, bathroom, etc. via the hot water pipe 70.

The hot water outlet pipe 70 is connected to the bypass pipe 60 at the confluence point 75. Therefore, the hot water from the hot water tap 190 has an appropriate temperature that is a mixture of the hot water output from the can body 10 and the hot water from the bypass pipe 60.

The hot water outlet pipe 70 is provided with a flow rate adjusting valve 90 and temperature sensors 120 and 130. The temperature sensor 120 is arranged on the upstream side (can body 10 side) of the confluence point 75 of the hot water discharge pipe 70 with the bypass pipe 60, and detects the output hot water temperature (hereinafter, can body temperature) from the can body 10. .. The temperature sensor 130 is provided on the downstream side (hot water discharge side) of the confluence point 75, and detects the hot water discharge temperature Th after the hot water from the bypass pipe 60 is mixed. The flow rate adjusting valve 90 is provided to control the flow rate of hot water.

The fuel gas delivered from the gas burner 30 is mixed with the combustion air from the blower fan 40. When the air-fuel mixture is ignited by an ignition device (not shown), the fuel gas is burned to generate a flame. The combustion heat generated by the flame from the gas burner 30 is given to the primary heat exchanger 11 and the secondary heat exchanger 21 in the can body 10.

The primary heat exchanger 11 heats the incoming water by heat exchange by the sensible heat (combustion heat) of the combustion gas by the gas burner 30. The secondary heat exchanger 21 heats the water passed by the latent heat of the combustion exhaust gas from the gas burner 30 by heat exchange. An exhaust path 15 for discharging the exhaust gas after heat exchange is provided on the downstream side of the can body 10 in the flow direction of the combustion gas. In this way, in the can body 10, the primary heat exchanger 11 and the secondary heat exchanger 21 heat the hot water supplied from the water inlet pipe 50 by the calorific value generated by the combustion in the gas burner 30.

The gas supply pipe 31 to the gas burner 30 is provided with a source gas solenoid valve 32, a gas proportional valve 33 whose opening degree is adjusted in proportion to the amount of current supplied, and capacity switching valves 35a to 35c. The original gas solenoid valve 32 has a function of turning on / off the supply of fuel gas to the gas burner 30. The gas flow rate of the gas supply pipe 31 is controlled according to the opening degree of the gas proportional valve 33.

The controller 300 includes a CPU (Central Processing Unit) 301, an interface 302 for controlling input / output from the outside, a timer 303, and a storage unit 304. The CPU 301 receives an output signal (detection) from each sensor and a user operation via the interface 302, generates a control command to each device in order to control the overall operation of the hot water supply device 100, and generates a control command to each device via the interface 302. And output.

Further, the CPU 301 samples the output signal (detection) from each sensor via the interface 302, and converts the sampled signal into a measured value by A / D (Analog / digital) conversion. The user operation includes a power on / off command for the hot water supply device 100 and a command for a set temperature value (including a hot water supply set temperature value Tr). The user operation may include an operation on / off command for the water heater 100. The control command includes a heating command for controlling the combustion of the gas burner 30. The heating command includes an open command or a close command to the original gas solenoid valve 32, and a command for variably adjusting the opening degree to the gas proportional valve 33.

Further, in the hot water supply device 100, heated water (water entry temperature Tw + ΔT) from the can body 10 and non-heating from the bypass pipe 60 are provided from the flow rate adjusting valve 90 arranged on the downstream side (hot water outlet side) of the confluence point 75. Hot water mixed with water (incoming water temperature Tw) is output.

The controller 300 can control the flow rate value Q and the flow rate of hot water discharged from the hot water discharge pipe 70 by controlling the opening degree of the flow rate adjusting valve 90. In the hot water supply device 100 shown in FIG. 1, the flow rate value Q is determined by the water supply pressure and the opening degree of the flow rate adjusting valve 90.

The flow rate sensor 150 is arranged on the downstream side (can body side) of the distribution valve 80. Therefore, the flow rate value Q detected by the flow rate sensor 150 indicates the flow rate (can body flow rate) that passes through the heating unit 20 stored in the can body 10.

When the operation command of the hot water supply device 100 is turned on, the controller 300 turns on the combustion operation in the can body 10 when the flow rate value Q detected by the flow rate sensor 150 exceeds the MOQ (minimum operating flow rate value). When the combustion operation is turned on, the original gas solenoid valve 32 is opened, and the supply of fuel gas to the gas burner 30 is started.

As can be understood from FIG. 1, the flow rate adjusting valve 90 is inserted and connected to a water passage from the water inlet pipe 50 to the hot water outlet pipe 70 through the can body 10. Then, the flow rate sensor 150 can detect the flow rate of "water" in the water passage. As shown in FIG. 1, even in the configuration in which the bypass pipe 60 is provided, the output flow rate from the flow rate adjusting valve 90 is determined by the value detected by the flow rate sensor 150 using the distribution ratio determined by the opening degree of the distribution valve 80. Can be detected.

(Functional configuration of controller 300)
FIG. 2 is a block diagram schematically showing a functional configuration of the controller 300. Each part of FIG. 2 may be composed of a software program executed by the CPU 301, dedicated hardware (electronic circuit), or a combination of the software program and the circuit. The controller 300 is an embodiment of a "control unit" that controls the hot water supply device 100.

With reference to FIG. 2, the controller 300 includes a required heat quantity acquisition unit 307, a predicted heat quantity acquisition unit 308, a heat treatment unit 309, and a heating command unit 310. The heat treatment unit 309 controls the heat command unit 310. In the first embodiment, when the hot water supply device 100 is turned on, the controller 300 repeats the processing by the required heat amount acquisition unit 307, the predicted heat amount acquisition unit 308, and the heat treatment unit 309 every cycle [n]. Further, the controller 300 samples (accepts) various sensor outputs via the interface 302 at a cycle synchronized with the above processing cycle [n].

The heating command unit 310 generates a heating command based on the control output from the heat treatment unit 309 and outputs the heating command to the heating unit 20. During the above intermittent operation, the heating command unit 310 outputs a combustion stop command 311 or a combustion command 312 based on the control output from the heat treatment unit 309. Since the gas burner 30 stops combustion when the combustion stop command 311 is output, the amount of heat generated corresponds to "No. 0". Further, when the combustion command 312 is output, the gas burner 30 burns at the minimum number which is the minimum combustion capacity, so that the amount of heat generated corresponds to the "minimum number". No. 2.4 is preset (stored) as the "minimum number" in the storage unit 304 of the hot water supply device 100 of the first embodiment. The minimum number is not limited to 2.4.

In the first embodiment, the heating command output from the heating command unit 310 to the gas proportional valve 33 is the calorific value to be input (supplied) to the heating unit 20 by burning the gas burner 30 (hereinafter, "actual input number"). A current signal of a magnitude corresponding to (also referred to as) is shown. Therefore, the hot water supply device 100 can variably control the amount of heat generated by the combustion of the gas burner 30 by the heating command.

(How to get the required number)
The required heat quantity acquisition unit 307 calculates the required number. Specifically, the required heat quantity acquisition unit 307 is based on the can body set temperature value TT, the hot water input temperature value Tin input to the heating unit 20 from the water input path, and the flow rate value Q measured by the flow rate sensor 150. Calculate the required number RQ according to 1). The coefficient β in (Equation 1) is a coefficient for converting the amount of heat into a number.

RQ = (TT-Tin) x Q x β ... (Equation 1)
In the first embodiment, the required heat quantity acquisition unit 307 calculates the required number RQ based on (Equation 1), but the method for acquiring the required number RQ is not limited to this. For example, when the table registered in association with the set of the can body set temperature value TT and the water entry temperature value Tin is stored in the storage unit 304 in advance, the required heat quantity acquisition unit 307 may use the can body set temperature value TT and the water entry temperature value TT. The required number RQ may be read out by searching the table based on the temperature value Tin.

In the first embodiment, the can body set temperature value TT indicates a target temperature by combustion control of the gas burner 30 of the combustion can body (more specifically, the primary heat exchanger 11). In the first embodiment, the can body set temperature value TT is set by using, for example, the hot water supply set temperature value Tr set by the user by operating the hot water supply device 100 (can body set temperature value TT = hot water supply set temperature value Tr + 15 degrees). ) Is set. However, 50 degrees ≤ TT ≤ 67 degrees.

(How to get virtual output)
The predicted heat quantity acquisition unit 308 predicts the calorific value output by the primary heat exchanger 11 when the gas burner 30 burns according to the “actual input number” indicated by the heating command from the heating command unit 310. This predicted amount of heat is also referred to as "virtual output" below.

The predicted heat quantity acquisition unit 308 follows the exponential moving average of the virtual output y [n] of the period [n] from the actual input number x [n] and the time constant L of the response delay of the water heater 100 (Equation 2). ) Is calculated.

y [n] = (L / (L + 1) x y [n-1]) + (1 / (L + 1) x x [n])
Converting the above equation gives the following (Equation 2).

y [n] = ((L × y [n-1]) + x [n]) / (L + 1) ... (Equation 2)
The predicted heat quantity acquisition unit 308 calculates the virtual output y [n] in synchronization with the processing cycle [n]. For example, the virtual output y [n] is a calculated value in the current processing cycle [n], and the virtual output y [n-1] is a calculated value in the previous processing cycle [n-1], and is a virtual output. y [n + 1] is a calculated value in the next processing cycle [n + 1]. Further, the actual input number x [n] is a calculated value in the current processing cycle [n]. When the virtual output is calculated during intermittent operation, the actual input number x [n] indicates 0 when the combustion stop command 311 is output in the processing cycle [n], and the processing cycle [n]. When the combustion command 312 is output, the number 2.4 (“minimum number”) is indicated.

In (Equation 2), the virtual output y [n] corresponds to the internal division point of the virtual output y [n-1] and the actual input number x [n] based on the time constant L and the time constant (L + 1). The value to be used is shown (see FIG. 4). According to (Equation 2), the virtual output y [n] can be calculated as a value obtained by correcting the value corresponding to the response delay.

In the first embodiment, the predicted heat quantity acquisition unit 308 calculates and acquires the virtual output y [n] by (Equation 2), but the acquisition method is not limited to this. For example, a table in which the virtual output y [n] is associated with the virtual output y [n-1] and the actual input number x [n] is stored in the storage unit 304, and the predicted calorific value is acquired. Unit 308 may read the virtual output y [n] by searching the table based on the virtual output y [n-1] and the actual input number x [n].

When the required number is equal to or less than the minimum number in each treatment cycle [n], the heat treatment unit 309 compares the magnitude relationship between the virtual output and the required number, and stops combustion according to the comparison result. The command 311 or the combustion command 312 is output via the heating command unit 310. As a result, the heat treatment unit 309 can intermittently operate the gas burner 30 by switching between combustion and combustion stop when the required number is equal to or less than the minimum number.

By performing the intermittent operation, the hot water supply device 100 can obtain a calorific value corresponding to a low number range of the minimum number or less.

(Explanation of intermittent operation)
3 and 4 are diagrams for explaining the intermittent operation according to the first embodiment. In FIGS. 3 and 4, time is taken on the horizontal axis and the number is taken on the vertical axis. In the first embodiment, a set minimum number (for example, 0.8) is shown as a reference value for ending the intermittent operation (stopping combustion). The set minimum number is stored in the storage unit 304. The set minimum number is not limited to 0.8 as long as the value has a relationship of 0 <set minimum number <minimum number (2.4).

A case where water with high preheating is supplied from an external device via a water entry path will be described with reference to FIGS. 3 and 4. When the hot water tap 190 is opened at time = 0 and the flow rate of the can body exceeds the minimum operating flow rate (MOQ), the combustion operation by proportional control is started. Since the proportionally controlled combustion operation is a well-known operation, the description will not be repeated.

After that, when the water entry temperature Tw from the external device rises, the required number RQ decreases. When the required number RQ becomes the minimum number (2.4) or less, the operation of the hot water supply device 100 is switched from the proportional control operation to the above-mentioned intermittent operation (see FIG. 3). With reference to FIG. 4, in the intermittent operation, the combustion command 312 indicating that the actual input number is 2.4 and the actual input number 0 are shown according to the magnitude relationship between the virtual output and the required number RQ. Combustion stop command 311 is output alternately. As a result, the hot water supply device 100 can output a calorific value corresponding to a low number range (minimum number (2.4) to set minimum number (0.8)) that cannot be originally obtained. it can. In the first embodiment, the intermittent operation ends when the required number RQ becomes less than the set minimum number.

(Flow chart of control of gas burner 30)
FIG. 5 is a schematic processing flowchart of combustion control according to the first embodiment. FIG. 6 is a processing flowchart of the intermittent operation according to the first embodiment. These flowcharts are stored in the storage unit 304 as a program. The processing is realized by the CPU 301 reading and executing the program from the storage unit 304. In the first embodiment, the CPU 301 calls and executes the program of the flowchart of FIG. 5 from the main routine that controls the hot water supply device 100 at regular intervals (periodically). The execution cycle of this program is synchronized with the processing cycle [n] described above.

With reference to FIG. 5, the CPU 301 determines whether or not the water heater 100 is in the power-on state based on the received user operation content (step S1). If it is not determined that the power is on (NO in step S1), the process of step S1 is repeated.

When the CPU 301 determines that the hot water supply device 100 is in the power-on state (YES in step S1), the required heat quantity acquisition unit 307 acquires the required number RQ according to (Equation 1) (step S3). The heat treatment unit 309 uses the set minimum number (0.8) and the minimum number (2.4) for the required number RQ (0.8 <required number RQ ≦ 2.4). It is determined whether or not the condition is satisfied (step S5). When the heat treatment unit 309 determines that the condition is not satisfied (NO in step S5), the series of processes is completed and the process returns to the original main routine.

When the heat treatment unit 309 determines that the above-mentioned conditions are satisfied (YES in step S5), the heat treatment unit 309 executes the intermittent operation process (step S6).

In the intermittent operation process with reference to FIG. 6, first, the predicted heat quantity acquisition unit 308 acquires a virtual output according to (Equation 2) (step S11). Further, the required heat quantity acquisition unit 307 acquires the required number RQ based on (Equation 1).

The heat treatment unit 309 determines whether or not the condition of (virtual output> required number RQ) is satisfied for the acquired virtual output and the required number RQ (step S17). When the heat treatment unit 309 determines that the condition (virtual output> required number RQ) is satisfied (YES in step S17), the heat treatment unit 309 controls the heating command unit 310 to output the combustion stop command 311 (step S19). As a result, when the output (calorific value) of the gas burner 30 is predicted to exceed the required number RQ, that is, when the hot water outlet temperature Th is predicted to exceed the hot water supply set temperature, the combustion stop command 311 is output. , It is possible to stop the combustion of the gas burner 30 and prevent overshoot.

Further, the heat treatment unit 309 controls the heating command unit 310 to output the combustion command 312 when it is determined that the condition (virtual output> required number RQ) is not satisfied (NO in step S17) (step S20). ). As a result, when it is predicted that the output (calorific value) of the gas burner 30 will be less than or equal to the required number RQ, the combustion command 312 is output and the gas burner 30 is calmed down with the minimum number (2.4). By burning, it is possible to prevent a situation in which the hot water outlet temperature Th falls below the hot water supply set temperature (undershoot). After the process of step S19 or step S20, the process returns to the original process of FIG.

[Embodiment 2]
The second embodiment shows a modification of each of the above-described embodiments. In the second embodiment, two types of entry temperature value Tin (1) and entry temperature value Tin (2) are defined as the entry temperature value Tin (1) in (Equation 1) for calculating the required number RQ.

The water entry temperature value Tin (1) is a value obtained by measuring the output (water entry temperature Tw) of the temperature sensor 110. The entry water temperature value Tin (2) indicates the hot water temperature [n] at the outlet of the secondary heat exchanger 21, that is, the temperature of the hot water immediately before entering the primary heat exchanger 11.

As a background of the embodiment, when the secondary heat exchanger 21 is provided in the middle of the water entry path, the primary heat exchanger is due to the piping capacity of the secondary heat exchanger 21 provided in the middle of the water entry path. The water entry temperature to 11 may change from the water entry temperature Tw detected by the temperature sensor 110 upstream of the water entry path. Therefore, if the intermittent operation is performed according to the required number RQ calculated based on the incoming water temperature Tw, the output of the heating command (combustion command 312) may be delayed and the hot water temperature Th may undershoot.

Against this background, in the second embodiment, the required heat quantity acquisition unit 307 used the lower temperature of the incoming water temperature value Tin (1) and the incoming water temperature value Tin (2) (Equation 2). According to this, the required number RQ is calculated. This prevents an output delay of the heating command (combustion command 312) during intermittent operation.

In the second embodiment, the CPU 301 calculates (estimates) the entry temperature value Tin (2) according to the following (Equation 3). This equation is the same as the calculation of the virtual output (Equation 1), the entry temperature value Tin (2) [n-1] calculated in the cycle [n-1] and the entry temperature value Tin (in the cycle [n]). 1) For [n], it is an expression for calculating the value of the internal division point according to the time constant L.

Water entry temperature value Tin (2) [n] = (L x water entry temperature value Tin (2) [n-1] + water entry temperature value Tin (1) [n]) / (L + 1) ... (Equation 3)
The value (initial value) of the incoming water temperature value Tin (2) at the start of operation of the hot water supply device 100 is a value calculated from a predetermined function using the flow rate value Q.

According to the second embodiment, the required heat quantity acquisition unit 307 has a temperature value measured by the temperature sensor 110 on the upstream side of the secondary heat exchanger 21 in the water entry path, and a secondary heat exchanger 21 on the downstream side. The required number RQ is calculated using the lower of the hot water temperature [n] at the outlet of the heat exchanger 21.

Therefore, for example, when the hot water stored in the tank of the fuel cell power generation unit, which is an external device, is supplied to the hot water supply device 100 from the water entry path, when the hot water in the tank runs out, the water entry temperature value Tin (1) Is lower. Further, when switching the operation from the fuel cell power generation unit to the hot water supply device 100, the hot water temperature [n] (water inlet temperature value Tin (2)) at the outlet of the secondary heat exchanger 21 is the water inlet temperature value Tin (2). It will be lower than 1). According to the second embodiment, in any case, it is possible to promptly output the combustion command 312 to prevent the undershoot of the hot water temperature Th.

[Embodiment 3]
The third embodiment shows a modification of the second embodiment. In the third embodiment, the above-mentioned entry temperature value Tin (2), that is, the time constant L of (Equation 3) for calculating the hot water temperature [n] at the outlet of the secondary heat exchanger 21 is changed.

FIG. 7 is a diagram for explaining the time constant L according to the third embodiment. In the third embodiment, in order to calculate the hot water temperature [n] at the outlet of the secondary heat exchanger 21 more accurately, the CPU 301 sets the time constant L variably by the flow rate value Q. That is, the third embodiment focuses on the fact that the time until the hot water reaches the primary heat exchanger 11 (the outlet of the secondary heat exchanger 21) via the water entry path changes depending on the flow rate of the hot water. Then, the time constant L of (Equation 3) is variably set by the flow rate value Q (see FIG. 7). Specific effects according to the third embodiment will be described later with reference to FIGS. 13 and 14.

[Embodiment 4]
The fourth embodiment shows a modification of each of the above-described embodiments. In the fourth embodiment, in order to calculate the required number RQ using (Equation 1), the can body set temperature value TT (1) and the can body set temperature value TT (2) are set as the can body set temperature value TT. Two types of upper limit values are defined.

The required heat quantity acquisition unit 307 calculates the required number RQ according to (Equation 1) using the can body set temperature value TT (1) and the can body set temperature value TT (2).

The can body set temperature value TT (1) indicates the above-mentioned (hot water supply set temperature value Tr + 15 degrees). The can body set temperature value TT (2) is calculated according to the following (Equation 4), which is a function of the incoming water temperature value Tin and the hot water supply set temperature value Tr.

TT (2) = (Tr-Tin x η (x = 100)) / (1-η (x = 100)) ... (Equation 4)
The function η (x = 100) is the amount of hot water mixed from the water inlet route to the hot water passage via the distribution valve 80 when the distribution ratio of the distribution valve 80 is η and is fully open (x = 100). Shown.

As a background of the embodiment, in the proportional control operation described above, the CPU 301 outputs a command based on the can body set temperature and the water entry temperature, and variably controls the distribution ratio (opening) of the distribution valve 80. The hot water temperature Th is maintained at the set temperature.

Here, when the temperature of the water supply preheating in the water entry path is high, the hot water supply temperature Th is maintained at the hot water supply set temperature even if the CPU 301 outputs a command to the distribution valve 80 to fully open (x = 100). It cannot be done and overshoots can occur. In order to deal with this, in the fourth embodiment, the required number RQ is calculated by using the lower upper limit value of the can body set temperature value TT (1) and the can body set temperature value TT (2). To do.

8 (A) and 8 (B) are diagrams for explaining the fourth embodiment. In the graph of FIG. 8, the horizontal axis represents time, and the vertical axis represents temperature or the required number RQ. In the comparative example of FIG. 8A, unlike the fourth embodiment, the case where the can body set temperature value TT is constant is shown. According to the comparative example, even if the entry temperature value Tin (that is, the temperature of the water supply preheating) in the entry path rises and approaches the hot water supply set temperature value Tr, the can body set temperature is constant, so the required number. The RQ does not become zero, and the combustion command 312 is output. Further, even when the distribution valve 80 is fully open, the hot water outlet temperature Th cannot be lowered to the hot water supply set temperature. As a result, an overshoot occurs.

On the other hand, in the fourth embodiment of FIG. 8 (B), as the incoming water temperature value Tin (water supply preheating temperature) rises, the can body set temperature value TT (2) calculated by (Equation 4) becomes a can. It becomes lower than the body set temperature value TT (1). After that, the required number RQ calculated using the can body set temperature value TT (2) becomes smaller as the incoming water temperature value Tin (water supply preheating temperature) increases.

When the entry temperature value Tin reaches the hot water supply set temperature value, the required number RQ calculated by (Equation 1) becomes zero. As a result, the condition (virtual output> required number) (step S17 in FIG. 6) is satisfied, the combustion stop command 311 is output, and the combustion of the gas burner 30 is stopped. Therefore, it is possible to prevent overshoot and maintain the hot water outlet temperature Th at the hot water supply set temperature.

[Embodiment 5]
The fifth embodiment shows a modification of each of the above-described embodiments. In the fifth embodiment, in the intermittent operation, the heat treatment unit 309 controls the heating command unit 310 so that the combustion stop continues for at least a predetermined time when the combustion stop command 311 is output.

This makes it possible to prevent high-speed switching of combustion stop → combustion → combustion stop of the gas burner 30 in intermittent operation. As a result, deterioration of the combustion system including the gas proportional valve 33 due to high-speed switching can be prevented, for example.

[Simulation by embodiment]
FIG. 9 is a diagram illustrating the operation of the hot water supply device 100 during intermittent operation according to each embodiment. In the graph of FIG. 9, the vertical axis represents temperature (° C.) or number, and the horizontal axis represents time (seconds). The graph of FIG. 9 shows the result of a computer simulation that imitates the intermittent operation performed by the inventors. In the simulation, each value is calculated while periodically changing the water entry temperature Tw and the flow rate value Q (can body flow rate value) in each of the above equations. The graph of FIG. 9 is a plot of the calculated values. In the simulation, the temperature of the preheating water supply was gradually changed from 15 degrees to 40 degrees. In addition, the duration of combustion stop was set to a minimum of 1.0 seconds, and the set minimum number was set to 0.8.

With reference to FIG. 9, the hot water tap 190 is opened, water is started to be supplied to the hot water supply device 100, and the operation is started. The water entry temperature Tw (graph G5), which is the water supply preheating temperature at the start of operation, shows a low value. At this time, proportional control operation is performed. Therefore, the calculated virtual output (graph G4) changes according to the required number (graph G3).

After that, when the water supply preheating temperature starts to rise, the lower upper limit of the can body set temperature value TT is adopted according to the fourth embodiment, so that the can body set temperature value TT (graph G6) starts to decrease.

About 40 seconds after the start of operation, when the condition (0.8 <requested number RQ ≦ 2.4) is satisfied, the intermittent operation is started. Even in the intermittent operation, the incoming water temperature Tw (graph G5) indicating the preheating temperature of the water supply rises, and accordingly, the lower can body set temperature value TT is selected according to the fourth embodiment (see graph G6). The number RQ (graph G3) decreases. After that, the virtual output (graph G4) also decreases and approaches the required number RQ. As a result, at the start of the intermittent operation, the period during which the combustion command 312 is output and burned (referred to as the ON period) is relatively longer than the period during which the combustion stop command 311 is output and the combustion is stopped (referred to as the OFF period). However, after that, the ON period becomes shorter, and when the water entry temperature Tw (graph G5) almost reaches the hot water supply set temperature value Tr (at the end of the intermittent operation), the combustion stop (OFF period) continues.

In this way, in the period of intermittent operation, the ON (combustion) period and the OFF (combustion stop) period are alternately repeated in synchronization with the cycle [n] (see graph G7). According to each embodiment, the duty ratio including ON and OFF in each cycle can be changed autonomously.

Therefore, in the intermittent operation when the required number RQ is the minimum number (2.4) or less, the hot water temperature Th while preventing overshoot and undershoot as compared with the case where the duty ratio is fixed. It is possible to accurately adjust the calorific value (the calorific value in the low number range between No. 2.4 to No. 0.8 in FIG. 5) so as to maintain the hot water supply set temperature value Tr.

[Effect of embodiment]
Regarding the effect of each embodiment, the advantage of using the virtual output (predicted heat quantity) to control the gas burner 30 and the advantage of switching the entry temperature used for calculating the required number RQ will be described.

(Advantages of using virtual output (predicted heat quantity))
The water heater generally includes a temperature sensor for detecting the temperature of water entering the primary heat exchanger, a water amount sensor for detecting the flow rate, and a temperature sensor for detecting the temperature of the can body. Therefore, it is possible to calculate the output of the current primary heat exchanger using the current detected temperature and the detected flow rate by the temperature sensor. However, as a background of each embodiment, (1) the outlet temperature of the primary heat exchanger 11 is detected downstream from the temperature heating unit (gas burner 30) by the can body temperature sensor, and (2) the gas burner 30. It is known that the primary heat exchanger (can body) has residual heat even after the combustion is stopped.

Therefore, in the intermittent operation, if the current calorific value is used to compare with the required number RQ and the combustion stop or permission is determined, the combustion stop determination is delayed. In order to prevent this, in each embodiment, the intermittent operation is performed using the virtual output (predicted heat quantity) which is the predicted value of the output of the primary heat exchanger 11 instead of the current heat quantity.

FIG. 10 is a diagram showing the relationship between (required heat quantity and current output) or (can body set temperature and current can body temperature) during intermittent operation. With reference to FIG. 10, it is assumed that a combustion permission command is output at time t = t1 and the current output matches the required number RQ at t = t2. Here, assuming that the controller 300 has determined that combustion has stopped, considering the current output or the can body temperature after t2, the temperature does not drop immediately as shown in Graph A of FIG. 10, but the required number as shown in Graph B. It will behave like a decrease after exceeding several RQs or exceeding the set temperature of the can body. The cause lies in the backgrounds (1) and (2) described above.

FIG. 11 shows a case in which a graph obtained by calculating the amount of heat using the temperature immediately after the output from the heating unit 20 or the amount of heat immediately after the output of the heating unit 20 is added to FIG. In FIG. 11, graph C shows a virtual output (predicted heat quantity). In FIG. 11, by comparing the virtual output with the required number RQ, the timing of determining the combustion stop can be advanced from t2 to t2'. That is, the combustion stop command 311 can be output at t2', whereby the detected temperature and the current output change as shown in FIG. That is, it is possible to prevent an overshoot.

(Advantage of switching the entry temperature used to calculate the required number RQ)
As shown in the second embodiment, the water entry temperature value Tin (1) in (Equation 1) for calculating the required number RQ is the water entry temperature value Tin (1) by the temperature sensor 110 and the outlet of the secondary heat exchanger 21. It is switched to one of the incoming water temperature value Tin (2), which is the estimated hot water temperature of.

In the second embodiment, the reason for using the two types of water entry temperature values Tin (1) and (2) is for preheating the water supply and running out of hot water (running out of hot water in the tank of the fuel cell (SOFC: Solid Oxide Fuel Cell) power generation unit). This is to prepare. FIG. 13 illustrates the change in the incoming water temperature during preheating the water supply, and FIG. 14 illustrates the change in the incoming water temperature when the hot water runs out.

In either case of FIG. 13 and FIG. 14, the outlet temperature of the secondary heat exchanger 21 rises or falls later than the currently detected water entry temperature. This is because it takes time for hot water to reach, depending on the piping capacity between the detection point and the primary heat exchanger 11.

Here, if the required number RQ is calculated using the incoming water temperature detected during the preheating of the water supply, the gas burner 30 stops the combustion even though the temperature is still at which combustion should be continued. As a result, it undershoots. This is also understood from the fact that, as shown in FIG. 13, the secondary heat exchanger outlet temperature (= primary heat exchanger inlet temperature) shows a lower value than the incoming water temperature detected at time t. To. That is, undershoot can be prevented by using the secondary heat exchanger outlet temperature as the incoming water temperature for calculating the required number RQ at the time of preheating the water supply.

On the other hand, when the required number RQ is calculated using the outlet temperature of the secondary heat exchanger at the time of running out of hot water, the determination of combustion permission by the controller 300 is delayed, and the output of the combustion command 312 is delayed. .. As a result, it undershoots. Therefore, when the hot water runs out, if the required number RQ is calculated using the detected water entry temperature, it is possible to accelerate the ignition of the gas burner 30 and prevent undershoot.

As described above, in the second embodiment, the secondary heat exchanger outlet temperature is assumed by calculating the detected temperature (incoming water temperature) by (Equation 3) (using the exponential moving average). Then, by adopting the lower of the two types of entry temperature value Tin (1) and the entry temperature value Tin (2) in the calculation of the required number RQ, the above-mentioned undershoot prevention requirement can be satisfied. ..

Further, in the third embodiment, the time constant L used for calculating the secondary heat exchanger outlet temperature (incoming water temperature value Tin (2)) is the flow value Q as described in FIG. It can be set variably by a one-variable function. Specifically, when the flow rate is low (that is, when the time required to reach the primary heat exchanger 11 is long), a large time constant can be calculated by the one-variable function. When the flow rate is high (that is, when the time required to reach the primary heat exchanger 11 is short), a small time constant can be calculated by the one-variable function.

As described above, in the third embodiment, the entry temperature value Tin (2) can be calculated more accurately by changing the degree (time constant L) of the entry temperature value Tin (2) according to the flow rate value Q. it can.

According to each embodiment, even in a water heater using water supply preheating, the hot water supply temperature Th is set to prevent overshoot and undershoot in the low number range by performing intermittent operation. The temperature value Tr can be maintained.

For example, when the hot water supply device 100 is connected to the fuel cell power generation unit, the water entry temperature value Tin of the water supply path of the hot water supply device 100 changes depending on the temperature of the hot water supplied from the fuel cell power generation unit (water supply preheating). Even in that case, by performing the intermittent operation according to each embodiment, the combustion control of the gas burner 30 is made to follow the change of the incoming water temperature value Tin promptly and linearly, and the hot water outlet temperature Th is set to the hot water supply set temperature value. It can be maintained at Tr.

It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is shown by the scope of claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

20 heating part, 30 gas burner, 32 source gas electromagnetic valve, 33 gas proportional valve, 50 water inlet pipe, 60 bypass pipe, 70 hot water outlet pipe, 75 confluence point, 80 distribution valve, 90 flow rate control valve, 100 hot water supply device, 110, 120 , 130 Temperature sensor, 111 piping, 150 flow rate sensor, 190 hot water tap, 300 controller, 307 required heat quantity acquisition unit, 308 predicted heat quantity acquisition unit, 309 heat treatment unit, 310 heating command unit, 311 combustion stop command, 312 combustion command.

Claims (7)

It ’s a water heater,
A heating unit including a heat exchanger and
A burner that heats the heat exchanger and
A flow rate sensor that measures the flow rate of hot water in the flow path that passes through the heating unit, and
A control unit that controls the hot water supply device is provided.
The control unit
To heat the heat exchanger from the target temperature value of the temperature of the hot water output from the heating unit, the input temperature value of the hot water input to the heating unit from the water entry path, and the flow rate value measured by the flow rate sensor. The required heat quantity acquisition unit that acquires the required heat quantity of
A heating command unit that outputs a heating command for burning the burner,
A predicted heat quantity acquisition unit that acquires a predicted heat quantity generated by combustion of the burner according to the heating command,
Includes a heat treatment unit that controls the heating command unit.
The heat treatment unit
When the required heat amount is equal to or less than the minimum heat amount corresponding to the minimum combustion capacity of the burner, and when the predicted heat amount is larger than the required heat amount, the heating command unit is controlled to output a combustion stop command. A hot water supply device that controls the heating command unit so as to output a combustion command for generating the minimum heat amount when the predicted heat amount is equal to or less than the required heat amount. The heat exchanger is
A primary heat exchanger that recovers sensible heat,
Including a secondary heat exchanger that recovers latent heat,
The outlet of the secondary heat exchanger is connected to the inlet of the primary heat exchanger.
The water heater further
A temperature sensor for measuring the temperature of hot water input from the water entry path is provided.
The control unit
Based on the temperature value measured by the temperature sensor and the measured flow rate value, the temperature value of the hot water at the outlet of the secondary heat exchanger is estimated.
The hot water supply device according to claim 1, wherein the water inlet temperature value for obtaining the required heat amount is the lower of the measured temperature value and the estimated temperature value at the outlet of the secondary heat exchanger. .. The hot water supply device
The piping that connects to the water heater and
A distribution valve for distributing a part of the total amount of water supplied to the water heater to the pipe is further provided.
The opening degree of the distribution valve indicates the ratio of the diversion to the pipe to the total water supply amount.
The control unit
A target temperature value of the temperature of the hot water output from the heating unit is calculated based on the hot water supply set temperature value, the water inlet temperature value, and the ratio.
Claim 1 or 2 that the target temperature value for acquiring the required heat amount is the lower of the set temperature value of the temperature of the hot water output from the heating unit and the calculated target temperature value. The hot water supply device described in. The heat treatment unit controls the heating command unit so that the combustion stop of the burner continues for at least a predetermined time when the combustion stop command is output, according to any one of claims 1 to 3. The hot water supply device described. The predicted calorific value acquisition unit
For each cycle [n], the predicted calorific value y [n] is acquired according to y [n] = ((L × y [n-1]) + x [n]) / (L + 1).
The hot water supply device according to any one of claims 1 to 4, wherein x [n] indicates the amount of heat required by the heating command output in the period [n], and L indicates a time constant. The hot water supply device according to any one of claims 1 to 5, wherein the time constant indicated by L is changed according to the measured flow rate value. It is a control method of the hot water supply device.
The hot water supply device
A heating unit including a heat exchanger and
A burner for heating the heat exchanger is provided.
The control method is
A request for heating the heat exchanger from the target temperature value of the temperature of the hot water output from the heating unit, the incoming temperature value of the hot water input to the heating unit, and the flow rate value passing through the heating unit. Steps to get the amount of heat and
A step of outputting a heating command for burning the burner, and
A step of acquiring the predicted amount of heat generated by the combustion of the burner according to the heating command is provided.
The step of outputting the heating command is
When the required heat amount is equal to or less than the minimum heat amount corresponding to the minimum combustion capacity of the burner, when the predicted heat amount is larger than the required heat amount, a command to stop combustion is output, and the predicted heat amount is the required heat amount. A method for controlling a hot water supply device that outputs a combustion command for generating the minimum amount of heat when the following is true.

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