JPH0531059B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention automatically controls the amount of fuel supplied to the burner according to the required amount of heat calculated based on the temperature difference between the set temperature and the inlet water temperature and the amount of inlet water. It relates to water heaters that use adjustable feed forward control.

[Prior Art] Conventionally, a burner has been provided with a first burner connected to a fuel supply path through a proportional valve, and a second burner connected to the proportional valve through a switching solenoid valve. Select either half-open capacity operation with combustion of only one burner or full-open capacity operation with simultaneous combustion of the first burner and second burner, and close or open the switching solenoid valve according to the selected capacity operation. By performing feedback control that proportionally controls the proportional valve, it is possible to control the control range by half-open capacity operation (switching solenoid valve is closed) and fully open capacity operation (switching solenoid valve is open). A water heater is known in which a region is set.

Further, during feedback control, if the temperature of the hot water is considerably lower than the set temperature, the amount of heat larger than the required amount of heat is proportionally controlled. Conversely, when the hot water temperature is higher than the set temperature, the amount of heat is proportionally controlled to be smaller than the required amount of heat.

[Problems to be Solved by the Invention] However, in conventional water heaters, when the proportional valve is proportionally controlled to output a larger amount of heat than the required amount of heat, it is necessary to open the proportional valve to obtain that ability. The control state of the proportional valve is switched from a control range based on half-open capacity operation to a control range based on full-open capacity operation.

In addition, if the proportional valve is opened too much by switching to the control area with full-open capacity operation, the control state of the proportional valve will be changed to the control area with full-open capacity operation, and then it will be opened again when the amount of heat approaches the required amount. The switching solenoid valve is closed and the control area is switched to half-open capacity operation.

In this way, when the proportional valve is proportionally controlled to output a larger amount of heat than the required amount of heat, when the proportional valve is opened to obtain capacity, the control state of the proportional valve changes from the control range of half-open capacity operation to fully open. If the switching solenoid valve is switched to the control area based on capacity operation, the switching solenoid valve may cause chattering due to repeated switching between the open and closed states. There was a risk that defects would occur.

The present invention prevents control failure by preventing chattering of the switching solenoid valve due to repeated switching between the open state and the closed state of the switching solenoid valve when feedforward control is performed. The purpose is to provide water heaters that

[Means for Solving the Problems] The present invention comprises a first burner connected to a fuel supply passage, and a second burner connected to the fuel supply passage in parallel with the first burner. a burner; a fuel supply amount control means for controlling the amount of fuel supplied to the burner; and a fuel supply amount control means disposed between the second burner and the fuel supply amount control means for controlling the supply of fuel to the second burner and a switching solenoid valve that controls stop; a heat exchanger that is placed above the burner and heats water passing through the burner with fuel heat of the burner; and detects the temperature of water flowing into the heat exchanger. temperature setting means for setting the temperature of the hot water flowing out of the heat exchanger to a desired set temperature; and inflow water amount detection means for detecting the amount of water flowing into the heat exchanger; A half-open capacity operation with fuel for only the burner and a full-open capacity operation with simultaneous combustion of the first burner and the second burner are set, and the temperature is determined based on the temperature difference between the set temperature and the incoming water temperature and the amount of incoming water. calculates the required amount of heat, and based on the required amount of heat, varies the control state of the fuel supply amount control means, and controls the switching solenoid valve to select between the half-open capacity operation and the full-open capacity operation. and a control circuit that performs feedforward control to perform feedforward control, and the control circuit is configured to output a heat amount larger than the required heat amount when the feedforward control is performed and half-open capacity operation is set. When varying the control state of the fuel supply amount control means, a technical means is adopted that fixes the switching solenoid valve in a closed state even if there is a request to switch from half-open capacity operation to full-open capacity operation.

In the present invention, "half open" includes not only 1/2 of full open, but also other partial open.

[Operation] The present invention calculates the required amount of heat based on the temperature difference between the set temperature and the incoming water temperature and the amount of incoming water. and,
Based on the required amount of heat, the control state of the fuel supply amount control means is varied, and the switching solenoid valve is controlled to select between half-open capacity operation and full-open capacity operation.

Therefore, during half-open capacity operation, by closing the switching solenoid valve and supplying fuel only to the first burner, while only the first burner is burning,
Feedforward control is performed in which the amount of heat is proportionally controlled by varying the control state of the fuel supply amount control means. In addition, during full capacity operation, the switching solenoid valve is opened to supply fuel to the first burner and the second burner.
Feedforward control is performed in which the amount of heat is proportionally controlled by varying the control state of the fuel supply amount control means while burning the burners simultaneously.

And, during feed forward control,
In addition, when half-open capacity operation is set, when changing the control state of the fuel supply amount control means to output a larger amount of heat than the required amount of heat, there is a request to switch from half-open capacity operation to full-open capacity operation. Also, by fixing the switching solenoid valve in the closed state, switching from half-open capacity operation to full-open capacity operation is not performed.

Therefore, it is possible to control the amount of heat by changing the control state of the fuel supply amount control means only when the switching solenoid valve is in the closed state. Switching between them is never repeated.

[Effects of the Invention] The present invention can prevent chattering of the switching solenoid valve by not switching between half-open capacity operation and full-open capacity operation when feedforward control is performed. , the cause of poor water heater control can be removed. Further, since fluctuations in the amount of fuel supplied between half-open capacity operation and full-open capacity operation can be prevented, the temperature control range can be expanded, and the outlet hot water temperature can be quickly brought close to the set temperature.

[Example] An example of a gas combustion type water heater using fuel gas as fuel will be described based on the drawings.

FIG. 1 shows a gas combustion type water heater employing an embodiment of the present invention.

A combustor case 10 is provided in a water heater case 2 of a gas combustion type water heater (hereinafter abbreviated as water heater) 1, and a combustor case 10 is further provided inside the combustor case 10. A gas burner 11 of the type is provided. The gas burner 11 includes a first burner 11a connected to the gas supply pipe 20,
A second burner 11b is connected to the gas supply pipe 20 in parallel with the first burner 11a. The combustor case 10 also includes a combustion fan 1 using a three-phase Y-wired brushless DC motor.
2 are provided. And gas burner 11
is a forced-air combustor that burns combustion air supplied by a combustion fan 12 and fuel gas supplied from a gas supply pipe 20, and the combustion gas generated by combustion is is exhausted to the outside from the exhaust port 3.

Above the combustor case 10 is a water supply pipe 30.
A heat exchanger 13 is provided, and water passing through the heat exchanger 13 is heated by the flame generated by the gas burner 11 and the heat of the combustion gas. Furthermore, the gas burner 1 inside the combustor case 10
In the vicinity of 1, there is a sparker 14 which is an ignition device,
A flame rod 15 is provided as flame detection means.

The gas supply pipe 20 includes a source solenoid valve 21, a main solenoid valve 22, which allows fuel gas to pass through when energized from the upstream side.
Governor type gas proportional valve (hereinafter abbreviated as governor proportional valve)
23 and switching electromagnetic valves (hereinafter abbreviated as switching valves) 24 are provided, respectively, and supply fuel gas to the gas burner 11 described above. The governor proportional valve 23 is a fuel supply amount control means that can continuously change the opening degree of the gas supply pipe 20 based on the applied current, and controls the supply pressure that changes according to the opening degree, thereby controlling the fuel supply amount. The amount of gas supplied (hereinafter referred to as gas amount) is continuously varied. The switching valve 24 is arranged between the governor proportional valve 23 and the second burner 11b, and is turned on (ON).
When it is turned off, the valve opens to supply fuel gas to the second burner 11b, and when it is turned off, it closes and stops supplying fuel gas to the second burner 11b.

A water filter 31 is installed at the most upstream part of the water supply pipe 30.
A water drain valve 32 is provided downstream of the drain valve 32, and a water volume proportional adjustment valve 33 using a geared motor that adjusts the amount of water entering the heat exchanger 13 is provided downstream thereof. A potentiometer 34 is provided for detecting the opening degree.

The temperature of the water whose amount has been adjusted by the water amount proportional adjustment valve 33 is detected by an inlet water temperature thermistor 35, which is an inlet water temperature detection means provided immediately downstream.
Further, the amount of water entering is detected by a water amount sensor 36 which is a water amount detecting means downstream of the water, and is sent to the heat exchanger 13 through the water supply pipe 30 .

The water supply pipe 30 on the downstream side of the heat exchanger 13 is equipped with a hot water temperature thermistor 38, which is a hot water temperature detection means for detecting the temperature of heated water, and a boiling water temperature thermistor 38, which is a hot water temperature detecting means for detecting the temperature of heated water, and a boiling water temperature thermistor 38, which is a hot water temperature detecting means for detecting the temperature of hot water. Prevention switch 39
A hot water tap (not shown) attached to a hot water supply location is provided at the most downstream position.

The water heater 1 having the above structure has a control device 50
controlled by As shown in FIG. 2, the control device 50 includes a control circuit 60 connected to a power cord 51 connected to a wiring outlet, and a main controller 54 for remotely controlling the water heater 1.
and a terminal for connecting the sub-controller 54a, and a gas type changeover switch 55 which is set according to the type of fuel gas when the water heater 1 is installed.

The main controller 54 and the sub-controller 54a are temperature setting means operated by the user. In this embodiment, the main controller 54 is provided close to the water heater 1, and the sub-controller 54a is installed in a hot water supply place such as a bathroom. It is provided. Note that the main controller 54 and the sub-controller 54a have respective operation switches 55,
56a, and outlet temperature setting switches 57, 57a for setting the outlet water temperature to a desired set temperature.

The control circuit 60 includes a microcomputer (hereinafter referred to as CPU) 70, a sparker circuit 71, a fan drive circuit 72, and a proportional valve control circuit 7.
3. Geared motor drive circuit 74, position detection circuit 7
5. There is a water amount detection circuit 76, and these circuits
Predetermined control is performed by the CPU 70.

The fan drive circuit 72 rotates the combustion fan 12 according to the combustion capacity such as the set temperature, and
A Hall IC provided in a three-phase Y-connected brushless DC motor detects its rotational speed and sends a detection signal to the CPU 70.

The proportional valve control circuit 73 controls the current applied to the governor proportional valve 23 according to the characteristics of the governor proportional valve 23 (depending on the type of gas) in order to adjust the amount of fuel gas supplied so that combustion in the gas burner 11 is performed at a desired air-fuel ratio. This is a circuit that performs control based on a proportional control constant depending on the The proportional valve control circuit 73 is a semi-fixed type that proportionally controls the maximum value of the current flowing to the governor proportional valve 23 in order to correct errors due to variations in the water heater 1 and pressure loss due to gas type to obtain an appropriate amount of gas. It has a volume.

The geared motor drive circuit 74 includes a water amount proportional adjustment valve 3 for adjusting the amount of water flowing into the heat exchanger 13.
This circuit drives the geared motor No. 3. It does not operate when the power is off (OFF), but when the power is on (ON), regardless of whether the operation switch 56a of the sub-controller 54a is ON or OFF, the previous set temperature is maintained. It is set at the position, and from that position it is initially set to a position according to the reference temperature.

The position detection circuit 75 is a circuit for analyzing the signal from the potentiometer 34 provided in the water volume proportional adjustment valve 33 to detect its opening degree. Accurate control is achieved by using only the electrically effective portion of the entire rotation angle in which a change in rotation appears as a change in resistance value, and by reading the detected resistance value directly as the rotation angle.

The water amount detection circuit 76 detects the amount of water entering based on the rotational speed signal of the water amount sensor 36. In this embodiment, the water amount detection circuit 76 detects the amount of water entering the water based on the rotation speed signal of the water amount sensor 36.
By obtaining two new pulse signals, the pulse repetition period is shortened and the pulse width is increased to reduce errors in the F/V lead pipe.

The CPU 70 has a memory function that stores a reference temperature that is set in advance at the time of assembling the water heater 1 or at the shipping stage, and the type of fuel gas to be used, and a main controller 5a and a subcontroller 54a.
It also performs a discrimination function to determine whether the water heater 1 is in a safe state, sequence control to control the operating order and timing of each of the above circuits, and combustion capacity control to control the combustion capacity of the gas burner 11. It also has safety controls for this purpose.

The determination function is a part that analyzes pulse signals in order to perform control according to the respective setting states of the main controller 54 and sub-controller 54a connected to the terminals 61 and 62 of the control circuit 60, respectively. The terminal 62 is a wire-saving terminal that can supply electricity to the main controller 54 and sub-controller 54a.
It is a wire terminal.

In the sequence control, when a water flow signal based on the water flow sensor 36 is obtained by the user opening the supply tap, the combustion fan 12 is activated, and after pre-purging is performed for a predetermined period of time, the ignition operation is performed. In the ignition operation, the main solenoid valve 21, the main solenoid valve 22, the governor proportional valve 23, and the sparker 14 are energized at the same time, and after the ignition is detected, the first and second calculated values Q,
The most efficient combustion capacity is calculated from q, and combustion capacity control is started.

The operation of the sparker 14 is not limited to the time of starting use.
In the following cases where there is a possibility of misfire even during use, i.e. when the double gas burner 11
When the switching valve 24 is opened due to the combustion capacity control associated with the use of The sparker 14 is activated even when the percentage decreases, and the sparker 14 continues to operate until a predetermined period of time has elapsed after starting the activation.

On the other hand, when a water flow signal is detected based on the water flow sensor 36, the combustion amount calculation starts simultaneously based on the inlet water temperature thermistor 35, but if the water temperature when water is not flowing through the water supply pipe 30 is read, the water temperature is correct. Therefore, in this embodiment, the water temperature is read by the inlet water temperature thermistor 35 after the water flow signal is detected, and the water temperature at that time is used as the water temperature data.

In combustion capacity control, the first calculated value (required heat = required capacity) Q is calculated from the temperature difference between the set temperature and the inlet water temperature and the amount of water input, as well as the temperature difference between the inlet water temperature and the outlet water temperature, and the amount of water input. Feed forward control (hereinafter referred to as
(referred to as FF control), automatic adjustment of the gas amount based on the temperature difference between the set temperature and the hot water temperature, the opening (ON) and closing (OFF) of the switching valve 24, and the air volume of the combustion fan 12. Feedback control (hereinafter referred to as FB control), which performs proportional integral control (hereinafter referred to as PI control) of the combustion amount and water input amount for adjustment, and FF control.
Switching control for switching between FB control and FB control is performed.

The FF control uses a first calculated value Q calculated from the temperature set by the main controller 54 and the sub-controller 54a, the incoming water temperature, and the amount of incoming water.
The most efficient capacity is calculated from the temperature difference between the incoming water temperature and the outgoing water temperature and the second calculated value q calculated from the incoming water amount, and the combustion fan 12, cabana proportional valve 23, switching valve 24, and water amount are The proportional adjustment valves 33 are controlled to automatically adjust the amount of air, gas, and water input. Note that the switching valve 24 is not switched only in the rapid heating capacity range described later.

The FF control selects one of the slow heating capacity range, rapid heating capacity range, and residual heat purge capacity range based on the comparison result between the first calculated value (required heat amount) Q and the second calculated value q. . In addition, in the FF control, the combustion fan 12, the governor proportional valve 23,
The switching valve 24 and the water volume proportional adjustment valve 33 are controlled to automatically adjust the amount of air, gas, and water input.

In the slow heating capacity range, the current applied to the governor proportional valve 23 (the opening degree of the governor proportional valve 23 ) is the capability range in which the amount of heat (gas amount) is proportionally controlled. In addition,
When this slow heating capacity range is selected, when the control of the governor proportional valve 23 to the control target value is completed, the FB
Move to control.

In the rapid heating capacity range, current is applied to the governor proportional valve 23 (governor proportional valve 23), and then when a predetermined condition (the temperature difference between the set temperature and the hot water temperature or the output time of the rapid heating heat amount) is satisfied, the capacity range shifts to the slow heating capacity range.

The residual heat purge capacity range is determined by adjusting the governor proportional valve 2 so that the control target value (target opening degree) outputs residual heat purge {Q×(Q+β)/Q} smaller than the required heat amount Q.
3 (the opening degree of the governor proportional valve 23), and then when a predetermined condition (the temperature difference between the set temperature and the tapped water temperature or the output time of residual heat purge heat amount) is satisfied, the gradual heating capacity is increased. This is an area of ability that moves into the area of ability.

FIG. 9 is a graph showing the relationship between the opening degree of the governor proportional valve 23 and the gas amount. In this embodiment, since the water heater 1 is equipped with a governor proportional valve 23 that can throttle the opening to 1/4 of the full opening, the half-open capacity control range and the full-open capacity control range are defined as follows during FF control and FB control. Overlapping control areas are performed.

The half-open capacity control range is a capacity of 1/8 to 1/2 of the fully open capacity of the gas burner 11 when the switching valve 24 is in the closed state, that is, during half-open capacity operation in which only the first burner 11a is burned, and is, for example, a necessary range. This is a control region in which the amount of heat is proportionally controlled by proportionally controlling the current flowing to the governor proportional valve 23 (the opening degree of the governor proportional valve 23) so as to output the amount of heat Q.

In the full-open capacity control range, when the switching valve 24 is in the open state, the first burner 11a and the second burner 11
During full-open capacity operation in which gas b is simultaneously combusted, current is applied to the governor proportional valve 23 (the opening degree of the governor proportional valve 23 is ) is a control region in which the amount of heat is proportionally controlled.

The overlapping control area is a control area in which the maximum area of the half-open capacity control area and the minimum area of the full-open capacity control area overlap, and the maximum value of the half-open capacity control area (= 1/2 of the full-open capacity of the gas burner 11) ability) below,
Moreover, the governor proportional valve 2 is configured to output the required amount of heat Q at a capacity that is higher than the minimum value of the full-open capacity control range (= 1/4 of the full-open capacity of the gas burner 11).
This is a control region in which the amount of heat is proportionally controlled by proportionally controlling the amount of electricity supplied to 3 (the opening degree of the governor proportional valve 23).

During FF control, depending on the required amount of heat Q, there is half-open capacity operation (switching valve 24 is closed) by combustion of only the first burner 11a, and full-open capacity operation by simultaneous combustion of the first burner 11a and second burner 11b. Capacity operation (the switching valve 24 is in an open state) is set.

Then, when the rapid heating capacity range is selected and the half-open capacity operation is set, the governor proportional valve 2
When the control target value of No. 3 is less than the maximum value of the half-open capacity control area, proportional control of the amount of heat is performed with the capacity less than the maximum value of the half-open capacity control area. In addition, if the control target value of the governor proportional valve 23 exceeds the maximum value of the half-open capacity control area, the amount of heat is proportionally controlled using the capacity within the overlapping control area of the half-open capacity control area, with the maximum value of the half-open capacity control area as the upper limit. By doing this, the switching valve 24 is fixed in the OFF state, so that the switching valve 24 is not switched between ON and OFF during the proportional control in the rapid heating capacity range.

In addition, when the rapid heating capacity range is selected and the full open capacity operation is set, the governor proportional valve 23
When the control target value is greater than or equal to the minimum value of the full-open capacity control range, proportional control of the amount of heat is performed at a capacity that is greater than or equal to the minimum value of the full-open capacity control range. In addition, governor proportional valve 2
If the control target value in step 3 is lower than the minimum value of the full-open capacity control area, the minimum value of the full-open capacity control area is set as the lower limit, and proportional control of the amount of heat is performed using the capacity within the overlapping control area of the full-open capacity control area. During this proportional control, the switching valve 24 is prevented from being switched on and off.

In addition, in FF control, when the outlet hot water temperature is higher than the set temperature, when half-open capacity operation (switching valve 24 is off) is selected according to the required heat amount Q, half-open capacity control is performed with a heat amount smaller than the required heat amount Q. The amount of heat is proportionally controlled at the minimum value in the range. Also,
In FF control, if the hot water temperature is higher than the set temperature and full open capacity operation (switching valve 24 is on) is selected according to the required amount of heat Q, the required amount of heat Q
Proportional control of the amount of heat is performed at the minimum value of the full-open capacity control range, which is a smaller amount of heat, so that the switching valve 24 is not switched between on and off during this proportional control.

Here, when the residual heat purge capacity range is selected and the full open capacity operation is set, if the control target value of the governor proportional valve 23 is less than the minimum value of the full open capacity control range, the control target value of the governor proportional valve 23 is lower than the minimum value of the full open capacity control range. Proportional control of the amount of heat may be performed using the capacity within the overlapping control area of the full-open capacity control area, with the minimum value as the lower limit, and the switching valve 24 may be prevented from being switched on and off during this proportional control.

With FB control, when the proportional control of gas amount (opening degree of governor proportional valve 23) reaches near the maximum range (duplicate control range) of the half-open capacity control range during half-open capacity operation, switching is performed while performing slow ignition control. valve 24
Turn ON (valve open) and switch to full open capacity control area. In addition, by FB control, when the proportional control of the gas amount (opening degree of the governor proportional valve 23) reaches the vicinity of the minimum range (overlapping control range) of the full open capacity control range during full open capacity operation, the switching valve 24 is turned OFF. By closing the valve and switching to the half-open capacity control region, switching control is performed to smoothly switch between half-open capacity operation and full-open capacity operation while performing combustion in a safe combustion state.

As a safety control, if the hot water temperature reaches the boiling temperature or higher and the boil prevention switch 39 remains on for a predetermined time (t8 seconds: e.g. 1 to 10 seconds), continuous combustion will continue for a predetermined time (t7 minutes: e.g. 40 seconds). ~120 minutes)
If this continues, turn off all the original solenoid valves 21 and main solenoid valves 22 when no flame is detected in the gas burner 11.
(closing the valve) and stopping the operation of the water heater 1.

The operation of the control device 50 of the water heater 1 of this embodiment will be explained based on the flowcharts shown in FIGS. 3 to 8 and the graphs shown in FIGS. 9 and 10. Note that FIGS. 3 to 5 are flowcharts showing sequence control (ignition operation), combustion capacity control, safety control, etc.

When installing the water heater 1, the type of fuel gas used by the gas company or the distributor of the water heater 1 is confirmed, and a reference temperature (40° C. in this embodiment) is set (S1). The user of the water heater does not set the fuel gas type and reference temperature.
Furthermore, the fuel gas type and reference temperature settings are stored in the memory function of the CPU 70 regardless of whether the power is turned on or off. However, when the set temperature is input by the user, the CPU 70 gives priority to the set temperature over the reference temperature and controls the water heater 1 so that the hot water temperature approaches the set temperature.

To use the water heater 1, connect the power cord 51 to a wiring outlet and turn on the power (S2).

It is determined whether the opening degree of the water volume proportional adjustment valve 33 is initially set to the maximum opening degree that allows for the maximum amount of water input, which is the amount of water input according to the reference temperature (40° C. in this embodiment) (S3).

Here, the water volume proportional adjustment valve 33 is set to an opening degree corresponding to the set temperature (or reference temperature) when the water heater 1 was last used, regardless of whether the sub-controller 54a is ON or OFF. However, with the geared motor that changes the opening degree of the water volume proportional adjustment valve 33, if you try to adjust the opening degree after inputting the set temperature,
Since several seconds of travel time are required, there is a risk that the combustion capacity control time will be cut into, and the combustion capacity control will be delayed. In order to prevent this, in this embodiment, the water volume proportional adjustment valve 33 is moved in advance before starting the combustion capacity control (FF control).

Therefore, the adjustment time of the water volume proportional adjustment valve 33 from the initial setting opening degree of the water volume proportional adjustment valve 33 to the opening degree corresponding to the set temperature during FF control (described later) is shortened, so that the FF control At times, the hot water temperature can be quickly set to the set temperature.

When the opening degree is set to the maximum that allows the maximum amount of water to enter for the combustion capacity, the geared motor is turned OFF (S4). If the opening is not set to the maximum that allows the maximum amount of water to enter, turn on the geared motor (S5).

Normally, the driving time of the water volume proportional adjustment valve 33 is approximately several seconds even when the maximum displacement occurs, but when freezing or foreign matter is mixed in, the water volume proportional adjustment valve 33
Because the water volume proportional adjustment valve 33 is locked, the water volume proportional adjustment valve 33 is closed despite the power supply from the geared motor drive circuit 74.
may not be displaced, and as a result, the energization time of the geared motor becomes longer, and there is a risk of burnout due to heating of the motor or geared motor drive circuit 74. In this embodiment, the geared motor drive circuit 74 is designed to prevent equipment failure even in such a case.
When the predetermined energization time (t1 seconds: e.g. 5 to 30 seconds) has elapsed (S6), the geared motor is
I try to turn it off.

Next, the operation switches 56, 56a of the main controller 54 or sub-controller 54a are activated.
Determine whether it is turned on (S7) and repeat S7 until it is turned on. When it is ON, it is determined whether or not the hot water outlet temperature is set to a desired set temperature by the hot water outlet temperature setting switches 57, 57a (S8).

Further, if the outlet hot water temperature is not detected after a predetermined period of time (t2 seconds: for example, 1 second) has elapsed (S9), the set temperature is set to the reference temperature of 40° C. (S10). Next, when the user opens the hot water tap (S11), the amount of water entering is detected by the water amount sensor 36 (S12).

Here, the way in which the inflowing water amount change signal is accepted is that a minute change not detected by the water amount detection circuit 76 is not accepted, but it is accepted when the amount of change in the inflowing water amount is equal to or greater than a predetermined value compared to the current inflowing water amount (steady flow). .

If the signal input to the water amount detection circuit 76 that reads the signal from the water amount sensor 36 is higher than a predetermined voltage, it is detected as a water flow signal, but a reading error occurs in the water amount detection circuit 76 due to undulations of the water flow, etc. If this is done, chattering will occur, so in this example, chattering is prevented by providing a hysteresis characteristic.
When the water flow rate is 2.5/min or more, it is detected as a water flow signal, and when there is a minute change such as 2.0/min or less, it is not detected as a water flow signal.

Normally, data on the amount of water entering is updated every sampling time, but taking into consideration the response delay of the water amount sensor 36, the amount of water entering may change if the cumulative value within a certain time exceeds a predetermined value. accepted as

Therefore, it is possible to detect not only an instantaneous change in the amount of water inflow, but also a change in the amount of water inflow within a certain period of time, and it is possible to adjust the gas amount in response to a wide range of changes in the amount of water inflow.

After detecting the amount of water entering, after a predetermined time (t3 seconds: for example 10 seconds) has elapsed (S13), the entering water temperature thermistor 3
5, the incoming water temperature is detected (S14). and,
The user determines whether or not the incoming water temperature is 55°C or higher (S15), and when the incoming water temperature is 55°C or higher, the user closes the hot water tap (S16) and turns on the operation switches 56, 56a of the main controller 54 and subcontroller 54a.
Turn off (S17). When the inlet water temperature is lower than 55℃, determine whether the inlet water temperature is below the set temperature (S18),
When the temperature is higher than the set temperature, the operations in S12 and below are repeated, and when the temperature is lower than the set temperature, the combustion fan 12 is turned on as shown in FIG. 4 (S19).

The Hall IC detects the rotation speed of the combustion fan 12 (S20), and determines whether the rotation speed of the combustion fan 12 is equal to or higher than a predetermined rotation speed (S12). When the rotation speed of the combustion fan 12 is lower than the predetermined rotation speed, the rotation speed corresponding to the combustion capacity cannot be obtained.
The main solenoid valve 21, main solenoid valve 22, switching valve 24, governor proportional valve 23, and combustion fan 12 are all turned off (S22 to S26), the user closes the hot water tap (S27), and then the main controller 54 and Operation switches 56, 56a of the sub-controller 54a
Turn off (S28).

When the rotation speed of the combustion fan 12 is higher than a predetermined rotation speed, a predetermined period of time (t4 seconds: e.g. 0.5 to 10 seconds)
Perform pre-purge (S29)) and remove all sparker 14, original solenoid valve 21, main solenoid valve 22, and switching valve 24.
It is turned ON (S30 to S33), and a slow ignition current is supplied to the governor proportional valve 23 (S34).

As shown in FIG. 10, the current flowing to the governor proportional valve 23 is controlled based on the rotational speed of the combustion fan 12, that is, the air volume, and the type of gas, except at the time of ignition. In this embodiment, in particular, the amount of gas for slow ignition during ignition is set to a constant ratio (initial value) to the maximum value of the current flowing to the governor proportional valve 23, which is adjusted by the semi-fixed volume of the proportional valve control circuit 73. This makes it possible to supply an appropriate amount of slow ignition gas at the time of ignition.

Further, after turning on the sparker 14, after a predetermined time (t5 seconds: for example, 5 to 20 seconds) has elapsed (S35), the sparker 14 is turned off (S36). and,
The combustion flame is detected by the flame rod 15, and it is determined whether a current greater than IA is inputted by the flame rod 15 (S37). When a current higher than IA is not input, S22 is detected as an ignition error.
Repeat the following actions. When a current of IA or more is input, the specified time (t6 seconds: e.g. 0.1 to 10
A slow ignition timer (seconds) is activated (S38), and the outlet hot water temperature is detected by the outlet hot water temperature thermistor 38 (S39), as shown in the flowchart of FIG.

Next, after the combustion capacity control shown in the flowcharts of FIGS. 6 to 8 is performed (S40), safety control from S41 onwards is performed.

It is determined whether the rotation speed of the combustion fan 12 is equal to or higher than a predetermined rotation speed (S41). When the rotational speed of the combustion fan 12 is lower than the predetermined rotational speed, an operation of S22 or lower is performed, and when the rotational speed of the combustion fan 12 is higher than the predetermined rotational speed, is a current of IA or higher being input by the flame rod 15? It is determined whether or not (S42). When a current of IA or more is input, continuous combustion will continue for a specified time (t7 minutes: e.g. 40 to 120 minutes)
(S43), the temperature of the hot water reaches the boiling temperature or higher (S44), and the water temperature continues to rise for a predetermined period of time (t8 seconds: e.g. 1 to 10 seconds).
(seconds) continues (S45), repeat the operations from S22 onwards.

If the continuous combustion is within t7 minutes and the hot water temperature does not reach the boiling temperature, the set temperature is input again (S46), and the operations from S39 onwards are repeated. The operation of S46 deals with the case where the user changes the set temperature.

When a current higher than IA is not input, it is detected as a misfire such as blowing out, and a misfire during combustion is detected as one.
It is determined whether or not it is the second misfire (S47).
Repeat the operations from S22 onwards. When a misfire occurs for the first time, close the main solenoid valve 21, main solenoid valve 22, and switching valve 24.
Turn OFF (S48 to S50) and then repeat the operations from S19 onwards.

FIG. 6 mainly shows a flowchart of FF control among combustion capacity controls.

After performing the operation of S39 in FIG. 5, the required amount of heat is calculated based on the following formula (S100), (S101).

Equation 1...First calculated value Q=(Tset-THin)×w=Required capacity (required heat amount) Equation 2...Second calculated value q=(THout-THin)×w=Currently in transition period Capacity Tset: Set temperature THin: Incoming water temperature THout: Outgoing hot water temperature w: Incoming water amount After calculating the first calculated value Q and the second calculated value q, the combustion amount and incoming water amount are set by FF control. If the combustion amount and water input amount are set by FF control (S102), the steps in S123 and below shown in the flowchart in Figure 7 are performed.
Performs FB (PI) control.

In addition, if the combustion amount and water input amount are not set by FF control, the water amount proportional adjustment valve 3
It is determined whether a predetermined time (t9 seconds: for example, 1 second) has elapsed after the initial setting of step 3 (S103). Here, t9 seconds is calculated from (heat capacity of heat exchanger 13)/(required amount of heat Q).

Then, after t9 seconds have elapsed, it is determined whether Q≧qx (S104). Here, x is a coefficient satisfying, for example, 1.5, and a cold start of the water heater 1 is determined based on the comparison result between the first calculated value Q and the second calculated value q.

When Q≧qx is not the case, it is determined whether Q<q or not (S105), and when Q<q is not the case, that is, when the hot water temperature (THout) is slightly lower than the set temperature (Tset),
The switching valve 24
is controlled (on: full-open capacity operation, or off: half-open capacity operation). And the hot water temperature (THout)
In order to bring the temperature close to the set temperature (Tset), the control target value of the governor proportional valve 23 is set so as to output the same amount of slow heating heat (Q x 1.0) as the required amount of heat Q, and the fan drive circuit 72 and the proportional valve Control circuit 73 and geared motor drive circuit 74 are controlled (S106). Note that 1.0 of (Q×1.0) is a coefficient.

That is, in the operation of S106, the current applied to the governor proportional valve 23 is adjusted by proportional control, with the opening degree (gas amount) at which the slow heating heat amount (Q×1.0) is obtained as the control target value. Furthermore, the rotational speed of the combustion fan 12 and the opening degree of the water volume proportional adjustment valve 33 are also controlled.

When Q<q, that is, when the hot water temperature is higher than the set temperature, the switching valve 24 is controlled according to the required heat amount Q calculated in S100 (ON: full open capacity operation, or OFF: half open capacity operation). ) to be done.
In order to bring the hot water temperature closer to the set temperature,
A control target value for the governor proportional valve 23 is set so as to output a minimum capacity smaller than the required amount of heat Q, and the fan drive circuit 72, proportional valve control circuit 73, and geared motor drive circuit 74 are controlled (S107).

That is, when the switching valve 24 is turned off (half-open capacity operation) according to the required heat quantity Q calculated in S100, the opening degree (gas quantity) that provides the minimum value of heat quantity in the half-open capacity control region is set to the control target value. As a result, the current flowing to the governor proportional valve 23 is adjusted by proportional control.

In addition, when the switching valve 24 is turned on (full-open capacity operation) according to the required heat quantity Q calculated in S100, the opening degree (gas quantity) is adjusted so that the minimum value of heat quantity in the full-open capacity control region is obtained. The current applied to the governor proportional valve 23 is adjusted. Furthermore, the rotational speed of the combustion fan 12 and the opening degree of the water volume proportional adjustment valve 33 are also controlled.

Then, the predetermined time {τ ₁ =
a/w [seconds]} (S108). Note that a is a coefficient, for example, when the heat capacity of the heat exchanger 13 is 500 c.c., the coefficient a is 20 × 60 [], and w is the amount of water input, for example, when the amount of water input w is 5 [/min], τ ₁ is set to 4 seconds, and when the amount of water input w is 10 [/min], τ ₁ is set to 2 seconds.

Then, it is determined whether the FF control time has elapsed a predetermined time (τ ₁ second: for example, 2 to 4 seconds) which is a function of the amount of water entering (S109). Note that the predetermined time (τ ₁
(seconds: for example, 2 to 4 seconds) is a function of the amount of water input, that is, the current amount of excess or deficiency and the amount commensurate with the heat capacity of the appliance, and the combustion amount of the gas burner 11 is adjusted only during the response delay of the hot water temperature thermistor 38. Waiting for control.

When τ ₁ second has elapsed, the fan drive circuit 72, proportional valve control circuit 73, and geared motor drive circuit 74 are controlled to output the same amount of slow heating heat (Q×1.0) as the required amount of heat Q (S110). In addition,
1.0 of (Q×1.0) is a coefficient.

In other words, the amount of slow heating heat (Q×
The current supplied to the governor proportional valve 23 is adjusted by proportional control using the required opening degree that yields 1.0) as the control target value. Furthermore, the rotational speed of the combustion fan 12 and the opening degree of the water volume proportional adjustment valve 33 are also controlled.

After that, FF control is output as an output that corresponds to large changes, so if there is an error due to variation, the outlet temperature will not reach the set temperature.
Take control.

Here, when τ ₁ second has not elapsed, the deviation between the set temperature (Tset) and the outlet hot water temperature (THout) is |dt
Determine whether the deviation is within |℃ (=±y℃: for example, ±5℃) (S111), and if the deviation is within |dt|℃, S110
If the deviation is not within |dt|℃, continue to perform S109.

When Q≧qx, that is, when the hot water temperature does not reach the set temperature, is the deviation between the set temperature (Tset) and the hot water temperature (THout) within |dt| (=±y℃: For example, ±5℃)? Determine whether or not (S112),
When the deviation is within |dt|℃, perform S106.

When the deviation is not within |dt|°C, the switching valve 24 is controlled (ON: full open capacity operation, or OFF: half open capacity operation) according to the required heat amount Q calculated in S100. Then, the control target value of the governor proportional valve 23 is set so as to output the maximum capacity {quick heating heat amount: Q×(Q+α)/Q} which is larger than the required heat amount Q, and the fan drive circuit 72 and geared motor drive circuit 74 are controlled. Control (S113). In addition, (Q+
α)/Q is a coefficient, and for example, when α is Q×3/4 kcal, it is 1.75.

In other words, the size maximum capacity {Q
The control target value is set so that the target opening degree is obtained by x(Q+α)/Q}. Furthermore, the rotational speed of the combustion fan 12 and the opening degree of the water volume proportional adjustment valve 33 are also controlled.

At this time, for example, the water volume proportional adjustment valve 33 is
The data input to the CPU 70 is read and the opening degree is quickly narrowed down according to the deviation between the set temperature (Tset) and the outlet hot water temperature (THout).

However, due to a change in the amount of water entering, the first calculated value Q, which is the required amount of heat, is updated, and if the governor proportional valve 23 is operated at this time, the change in the amount of gas and the change in the amount of water entering interfere, and the temperature of the hot water exiting is affected. appears, so when changing the opening degree (inflow amount) of the water volume proportional adjustment valve 33,
Proportional control of the amount of heat (gas amount) by the governor proportional valve 23 is not performed.

Here, the following restrictions are added to the operation of S113. That is, since ON or OFF of the switching valve 24 is determined based on the calculation result of S100,
It is determined whether or not the switching valve 24 is turned on (S114), and when the switching valve 24 is turned on, that is, when operating at full capacity with simultaneous combustion of the first burner 11a and the second burner 11b, that is, at maximum When the target opening degree at which the capacity is obtained is an opening degree corresponding to the capacity in the full-open capacity control area, the output of the maximum capacity {Q × (Q + α) / Q} that is larger than the required heat amount Q will be the output within the full-open capacity control area. In this way, proportional control of the amount of heat (gas amount) is performed. Then it returns to S112 operation.

Further, when the switching valve 24 is not turned on, that is, during half-open capacity operation with combustion of only the first burner 11a, it is determined whether the control target value of the governor proportional valve 23 is equal to or greater than the maximum value of the half-open capacity control range. (S115).

When the control target value of the governor proportional valve 23 is not greater than or equal to the maximum value of the half-open capacity control region, that is, when the target opening degree at which the maximum capacity is obtained is smaller than the opening degree corresponding to the maximum value of the half-open capacity control region, the required amount of heat Q Proportional control of the amount of heat (gas amount) is performed so that the output of the larger maximum capacity {Q×(Q+α)/Q} becomes the output of the half-open capacity control region outside the overlap control region. Then it returns to S112 operation.

Further, when the control target value of the governor proportional valve 23 is greater than or equal to the maximum value of the half-open capacity control region, that is, when the target opening degree at which the maximum capacity is obtained is greater than or equal to the opening degree corresponding to the maximum value of the half-open capacity control region, In order not to change the valve state of the switching valve 24, the current flowing through the governor proportional valve 23 is adjusted with the maximum value of the half-open capacity control region as the upper limit. Therefore, proportional control of the amount of heat (gas amount) is performed so that the output of the maximum capacity {Q×(Q+α)/Q}, which is larger than the required amount of heat Q, becomes the output of the half-open capacity control region within the overlap control region.
(S116). Then it returns to S112 operation.

In other words, after the governor proportional valve 23 is opened with the opening degree corresponding to the maximum value of the half-open capacity control region as the upper limit while continuing the half-open capacity operation, when the outlet hot water temperature approaches the set temperature, the required value is lower than the upper limit. The governor proportional valve 23 is gradually throttled until the required opening degree is reached to obtain the amount of heat Q. Therefore, during half-open capacity operation in the rapid heating capacity range, the current applied to the governor proportional valve 23 is limited so as to be equal to or less than the maximum value in the half-open capacity control range.

Therefore, when the switching valve 24 is only in the open state or only in the closed state, the governor proportional valve 2
Since the amount of heat (gas amount) can be proportionally controlled by the switch valve 2, the gas burner 11 is not switched between full open capacity operation and half open capacity operation.
The switching between the valve open state and the valve closed state in step 4 is not repeated.

This makes it possible to prevent chattering caused by repeating ON and OFF of the switching valve 24, thereby eliminating the cause of poor control of the water heater 1.
Further, since the gas burner 11 is not switched between full-open capacity operation and half-open capacity operation, fluctuations in the gas amount can be prevented, so the temperature control range can be expanded and the hot water temperature can be brought closer to the set temperature quickly. This makes it possible to speed up the control of the rapid heating capacity range.

FIG. 7 shows a flowchart of FB (PI) control.

In PI control, it is determined whether the deviation between the set temperature (Tset) and the hot water temperature (THout) is more than +y℃ (for example, +5℃) (S123), and when the deviation is more than +y℃, the required heat amount Q is determined. Small residual heat purge heat amount {Q
The fan drive circuit 72, proportional valve control circuit 73, and geared motor drive circuit 74 are controlled so as to output x(Q+β)/Q} (S124). In addition,
(Q+β)/Q is a coefficient, for example, 0.6 when β is 1/4Qkcal.

That is, first, the capacity {Q
The governor proportional valve 23 is throttled so that the target opening degree is obtained by x(Q+β)/Q}. and,
The switching valve 24
is controlled (on: full-open capacity operation, or off: half-open capacity operation). Furthermore, the combustion fan 12
The rotation speed and the opening degree of the water volume proportional adjustment valve 33 are also controlled.

Then, for a predetermined period of time (t10 seconds: for example, 30 seconds)
After the time has elapsed (S125), safety control from S41 shown in the flowchart of FIG. 5 is performed. Furthermore, if t10 seconds have not elapsed, the operations from S123 onwards are repeated.

When the deviation is not more than +y°C, the integral time is calculated from the composite function of the temperature deviation function and the water input amount function (S127).

Temperature deviation: e = Set temperature - Hot water temperature ∴F(e) = (K ₁ - e) x k ₁ K, k are constants Incoming water volume w is a known quantity detected by the water flow sensor ∴G(w) = (K ₂ - w) x k ₂ Integral time T is: ∴T = {F(e) + G(w)} = {(155-e) x 1/8 + (80-w) x 1/8} = PI control Output time Therefore, the greater the deviation between the set temperature and the outlet temperature, the shorter the integral time [seconds], or the greater the amount of water input, the shorter the integral time, and the output time to the governor proportional valve 23 or water volume proportional adjustment valve 33. becomes shorter.

Then, the integration time (T time: e.g. 150 seconds)
has passed (S128), it is determined whether the temperature deviation e≦1 (S129), and when the temperature deviation between the set temperature and the hot water temperature is less than 1, that is, e≦1, the Perform safety controls below S41 in the flowchart.

In addition, when the temperature deviation between the set temperature and the hot water temperature is not less than 1, that is, when e≦1, the coefficient Kp corresponding to the gas type of the fuel gas is input (S130), and the coefficient Kp according to the gas type is input. , and the following PI control output is updated so as to switch to a proportional control constant (PI control output change amount) based on the temperature deviation between the set temperature and the hot water temperature, and the governor proportional valve 23 or water flow rate is applied to the PI control output. After outputting the proportional control constant to the proportional adjustment valve 33 as a temperature deviation function and performing switching control of the gas burner 11 as shown in the flowchart of FIG. 8 (S131), S41 and below shown in the flowchart of FIG. Performs safety control.

PI control output: PN=PN-1+e×Kp PI control output variation: ΔVS=e×Kp Current PI control output: PN-1=Q+α ∴PI control output: PN=PN-1+ΔVS However, the specified flow rate (5/ ), the maximum value of PI control output PN {Q×(Q
+α)/Q} is brought close to the amount of slow heating heat (Q+1.0), which is the same as the required amount of heat Q, to improve stability at minute flow rates.

Therefore, by switching to a proportional control constant according to the load such as gas type, gas amount, and water input amount, the gas amount can be increased or decreased (variable rather than fixed value), allowing a wide range of free PI. can be controlled. In addition, PI control that is compatible with the characteristics of the governor proportional valve 23 (which differs depending on the gas type) can be performed. Furthermore, from the integral time T and the PI control output, the outlet hot water temperature can be quickly brought close to the set temperature.

Also, the gas type of fuel gas or the gas supply pipe 2
A predetermined amount of gas may not be obtained due to zero pressure loss. In this case, the current flowing to the governor proportional valve 23 is changed from A ₁ to A ₂ for the minimum current during full-open capacity operation, and from B _{2 to B for the maximum current during half-open capacity operation, as shown in the graph of Fig. 10} . ₁ and proportional control is performed so that a predetermined amount of gas is obtained.

Here, as shown in the flowchart of Figure 7,
When the PI control output is updated in S131, switching control is performed to switch the dual gas burner 11 between half-open capacity operation and full-open capacity operation based on the flowchart shown in FIG.

When updating the PI control output in S131 shown in the flowchart of FIG. 7, it is determined whether the switching valve 24 is turned on (S200), and the switching valve 24 is
When it is not turned on, that is, the first burner 11a
In half-open capacity operation with only combustion, the supply voltage to the combustion fan 12 is proportionally controlled based on the deviation between the set temperature and the hot water temperature to automatically adjust the amount of air, and the current supplied to the governor proportional valve 23 is The gas amount is automatically adjusted by proportional control (S201).

At this time, has the proportional control of the voltage supplied to the combustion fan 12 and the current applied to the governor proportional valve 23 reached near the maximum range of the half-open capacity control range (overlapping control range: for example, the maximum value of the half-open capacity control range)? It is determined whether or not (S202), and when the half-open capacity control range reaches the vicinity of the maximum range, a full-open switching signal is output (S203). The full open switching signal uses a limit on the voltage supplied to the combustion fan 12 or the current applied to the governor proportional valve 23.

A certain period of time (t11:
For example, for 5 to 30 seconds), the combustion fan 1
The proportional control of the supply voltage to the governor proportional valve 23 and the current flowing to the governor proportional valve 23 remains near the maximum range of the half-open capacity control range (duplicate control range: for example, the maximum value of the half-open capacity control range) (S204). S205), for example, in order to equalize the capacity to the maximum value of the half-open capacity control range, a gentle ignition current is supplied to the governor proportional valve 23 (S206), the switching valve 24 is turned ON (S207), and the first burner 11a is When the second burner 11b is operated at full capacity with simultaneous combustion, the supply voltage to the combustion fan 12 is automatically controlled proportionally based on the deviation between the set temperature and the hot water temperature, and the amount of air is automatically adjusted. The amount of gas is automatically adjusted by proportionally controlling the current supplied to the valve 23.

When the switching valve 24 is turned on, that is, when the first burner 11a and the second burner 11b are operating at full capacity with simultaneous combustion, the flow to the combustion fan 12 is determined based on the deviation between the set temperature and the hot water temperature. In addition to proportionally controlling the supply voltage and automatically adjusting the air volume,
The gas amount is automatically adjusted by proportionally controlling the current supplied to the governor proportional valve 23 (S208).

At this time, has the proportional control of the voltage supplied to the combustion fan 12 and the current applied to the governor proportional valve 23 reached near the minimum range of the full-open capacity control range (overlapping control range: for example, the minimum value of the full-open capacity control range)? It is determined whether or not (S209), and when it reaches near the minimum range of the full-open capacity control range, a half-open switching signal is output (S210). The half-open switching signal uses a limit on the voltage supplied to the combustion fan 12 or the current applied to the governor proportional valve 23.

A certain period of time (t12:
For example, for 5 to 30 seconds), the combustion fan 1
The proportional control of the supply voltage to the governor proportional valve 23 and the current flowing to the governor proportional valve 23 remains near the minimum range of the full-open capacity control range (overlapping control range: for example, the minimum value of the full-open capacity control range) (S211). S212), the switching valve 24 is turned off without changing the supply voltage to the combustion fan 12 and the current flowing to the governor proportional valve 23 (S213), and half-open capacity operation is performed by combustion of only the first burner 11a. Based on the deviation between the set temperature and the hot water temperature, the supply voltage to the combustion fan 12 is proportionally controlled to automatically adjust the air volume, and the current supplied to the governor proportional valve 23 is proportionally controlled to automatically adjust the gas volume. Adjust.

At this time, the voltage supplied to the combustion fan 12 and the current supplied to the governor proportional valve 23 each correspond to their optimum values, and are constant regardless of whether the gas burner 11 is operated at full or half open capacity. Since the combustion fan 12 has a large inertial force and a response delay, the voltage supplied to the combustion fan 12 and the current applied to the cabana proportional valve 23 are not changed. Then,
Smooth switching control from half-open capacity operation to full-open capacity operation or from full-open capacity operation to half-open capacity operation can be performed while maintaining a safe combustion state.

Furthermore, each of the first burner 11a and the second burner 11b has a capacity limit, and if the other burner can cover the limit value, the control range may be expanded by switching the switching valve 24. However, the method of detecting the switching signal as an instantaneous value can cause chattering of the switching valve 24 in water heaters with large heat capacity or delayed response, such as the water heater 1, which may cause the control of the water heater 1 to become difficult. This was a cause of defects. However, as in this embodiment, when the switching region remains in the switching region {near the overlapping control region (for example, the maximum value of the half-open capacity control region or the minimum value of the full-open capacity control region)] for a certain period of time, the half-open capacity operation and the full-open capacity operation are switched. The switching valve can prevent chattering of the switching valve 24 caused by repeating ON and OFF of the switching valve 24.

[Modification] In this embodiment, a gaseous fuel such as fuel gas is used as the fuel, but a liquid fuel such as petroleum may also be used as the fuel.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a gas combustion water heater according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a control device for a gas combustion water heater according to an embodiment of the invention. 3 to 5 show sequence control, combustion capacity control, and combustion capacity control according to an embodiment of the present invention.
Flowchart of safety control, FIG. 6 is a flowchart mainly of FF control according to an embodiment of the present invention,
FIG. 7 is a flowchart of FB control according to an embodiment of the present invention, FIG. 8 is a flowchart of gas burner switching control, and FIG. 9 is a flowchart of governor proportional valve opening and gas according to an embodiment of the present invention. FIG. 10 is a graph showing the relationship between the current to the governor proportional valve and the gas amount according to an embodiment of the present invention. In the figure, 1... Gas combustion water heater, 11... Gas burner, 11a... First burner, 11b... Second burner, 13... Heat exchanger, 20... Gas supply pipe (fuel supply path) ), 23...Governor proportional valve (fuel supply amount control means), 24...Switching solenoid valve, 3
5...Incoming water temperature thermistor (incoming water temperature detection means), 3
6...Water amount sensor (water inflow detection means), 38...
Outlet hot water temperature thermistor (outlet hot water temperature detection means), 50...
Control device, 54...Main controller (temperature setting means), 54a...Sub controller (temperature setting means), 60...Control circuit, Q...First calculated value (required amount of heat), q...Second Calculated value.

Claims (1)

[Claims] 1 (a) a first burner connected to a fuel supply path;
and a second burner connected to the fuel supply path in parallel with the first burner; (b) fuel supply amount control means for controlling the amount of fuel supplied to the burner; (c) ) a switching solenoid valve disposed between the second burner and the fuel supply amount control means to control supply and stop of fuel to the second burner; (d) a switching solenoid valve disposed above the burner; a heat exchanger that heats the water passing through the heat exchanger using the combustion heat of the burner; (e) an inlet water temperature detection means that detects the temperature of water flowing into the heat exchanger; and (f) the heat exchanger. temperature setting means for setting the outlet temperature of water flowing out from the heat exchanger to a desired set temperature; (g) inflow water amount detection means for detecting the amount of water flowing into the heat exchanger; and (h) the first burner. A half-open capacity operation with only combustion, and a full-open capacity operation with simultaneous combustion of the first burner and the second burner are set. A feed that calculates the amount of heat and changes the control state of the fuel supply amount control means based on the required amount of heat, and controls the switching solenoid valve to select between the half-open capacity operation and the full-open capacity operation. a control circuit that performs forward control, the control circuit controlling the fuel supply so as to output a larger amount of heat than the required amount of heat during the feed forward control and when half-open capacity operation is set. A water heater characterized in that, when changing the control state of the quantity control means, the switching solenoid valve is fixed in a closed state even if there is a request for switching from half-open capacity operation to full open capacity operation.