JPH0472136B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides feedforward control that controls a proportional valve based on incoming water temperature, set temperature, and incoming water amount, and feed forward control that controls a proportional valve based on outlet water temperature and incoming water amount. The present invention relates to a water heater that employs feedback control.

[Prior Art] Generally, in the control circuit of a water heater, a minute change in the amount of water entering per a certain sampling time is not detected because the response is poor, and the water amount signal from the water sensor is When a change greater than the amount of water is detected, it is detected as a water flow signal, and the water input amount data is updated based on the water flow signal.
Depending on the updated water inflow data, the opening degree of the proportional valve is controlled to automatically adjust the amount of fuel supplied, and the blower is controlled to automatically adjust the amount of combustion air supplied.

In addition, as a method of detecting the amount of water entering, for example, as described in Japanese Patent Application Laid-open No. 58-24751, a pulse output with a frequency proportional to the water flow rate from a water flow sensor attached to a water supply pipe is used. By converting to a DC voltage signal proportional to the frequency,
Detecting the amount of water entering. When this method of detecting the amount of water entering is used, if the pulse output from the water amount sensor is sufficiently smoothed, a response delay will occur, and if a quick response is obtained, ripples will occur. Furthermore, if the proportional valve is controlled in response to ripples, chattering or the like may occur, so minute changes in the amount of water entering due to ripples are not detected.

[Problems to be Solved by the Invention] However, in conventional water heaters, when a minute change in the amount of water entering due to undetected ripples continues for a certain period of time, in other words, it changes gradually. No consideration was given to the fact that small changes may not be detected or the response of the water sensor may be delayed, making it impossible to accurately detect the amount of water. For this reason, there was a problem in that it was not possible to adjust the amount of fuel supplied or the combustion air to accommodate a wide range of changes in the amount of water that could be handled even with minute changes in the amount of water entering.

SUMMARY OF THE INVENTION An object of the present invention is to provide a water heater that can adjust the amount of fuel supplied and the amount of combustion air in response to a wide range of changes in the amount of water that can deal with even minute changes in the amount of water entering.

[Means for Solving the Problems] The water heater of the present invention includes a burner that burns fuel, a fuel supply amount control means that controls the amount of fuel supplied to the burner, and a supply amount of combustion air to the burner. a heat exchanger that heats the water passing through the burner using the heat of the burner; and an incoming water temperature detection means that is provided upstream of the heat exchanger and detects the incoming water temperature of the water flowing into the heat exchanger. a hot water outlet temperature detection means for detecting the outlet temperature of water flowing out from the heat exchanger; a temperature setting means for setting the outlet water temperature to a desired set temperature; and a temperature setting means for detecting the amount of water flowing into the heat exchanger. When the incoming water amount detection means detects an incoming water amount that has changed by a predetermined amount of water with respect to the past water inflow amount per certain sampling time, it is detected as an update signal of the water flow signal, A water inflow amount detection circuit detects as an update signal of the water flow signal when the cumulative total of minute changes within a certain time reaches the predetermined water flow amount; When detected, the input water amount is updated to a value obtained by increasing or decreasing the amount of change in the past water input amount, and the fuel supply amount control means and the blower are controlled based on the updated water input amount, the input water temperature, and the set temperature. A technical means is adopted that includes a control circuit that performs yield forward control and performs feedback control to control the fuel supply amount control means and the blower based on the updated water input amount and the hot water exit temperature.

[Function] The inflowing water amount detection circuit detects it as an update signal of the water flow signal when the inflowing water amount detection means detects the amount of incoming water that has changed by a predetermined amount of water per a certain sampling time, and also detects it as an update signal of the water flow signal when the inflowing water amount detection means detects an inflow amount that has changed by a predetermined amount of water per a certain sampling time. When the cumulative value of minute changes in the amount of water entering the system changes by a predetermined amount of water, it is detected as an update signal of the water flow signal.

Then, when the water inflow amount detection circuit detects an update signal of the water flow signal, the control circuit updates the inflow amount to a value obtained by increasing or subtracting the change from the past water inflow amount. For this reason, feedforward control that controls the fuel supply amount control means and the blower based on the updated water inflow amount, inlet water temperature, and set temperature, and feedforward control that controls the fuel supply amount control means and the blower based on the updated water inflow amount and outlet temperature. Feedback control is performed to control the

[Effects of the Invention] It is possible to obtain the optimum fuel supply amount and combustion air amount corresponding to a wide range of water amount changes that can cope with even minute changes in the amount of water flowing into the heat exchanger.

[Example] Next, an example of a gas combustion 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.

Inside the water heater case 2 of the gas combustion water heater 1,
A combustor case 10 is provided, and a double gas burner 11 consisting of a first burner 11a and a second burner 11b that combusts fuel gas supplied through a gas supply pipe 20 is further provided inside the combustor case 10. . In addition, the combustor case 10 includes a three-phase Y
A combustion fan 12 is provided, which is a blower using a wired brush DC motor, and a gas burner 11 is provided.
is a forced-air combustor that burns the combustion air supplied by the combustion fan 12 and the fuel gas supplied from the gas supply pipe 20 at a predetermined air-fuel ratio. The fuel gas 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. Further, in the vicinity of the gas burner 11 in the combustor case 10, a sparker 14 as an ignition device and a flame rod 15 as a flame detection means are provided.

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.
A governor-type gas proportional valve (hereinafter referred to as governor proportional valve) 23, which is a fuel supply amount control means that adjusts the amount of fuel gas supplied (hereinafter referred to as gas amount) by controlling the supply pressure, goes to the second burner 11b. A switching electromagnetic valve (hereinafter abbreviated as a switching valve) 24 is provided to cut off the fuel gas depending on the usage state, and supplies the fuel gas to the gas burner 11 described above.

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 inflow amount is adjusted by the water amount proportional adjustment valve 33 is detected by an incoming water temperature thermistor 35, which is an incoming 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 .

In the water supply pipe 30 on the downstream side of the heat exchanger 13, there is a hot water temperature thermistor 38, which is a hot water temperature detection means for detecting the temperature of heated water, and a boiling prevention device that turns on when the hot water temperature reaches the boiling temperature or higher. A switch 39 is provided, and a hot water tap (not shown) attached to a hot water supply location is provided at the most downstream side.

The water heater 1 having the above configuration has a control device 50
controlled by

As shown in FIG. 2, the control device 50 connects a control circuit 60 connected to a power cord 51 connected to a wiring outlet, and a main controller 54 and a sub-controller 54a for remotely controlling the water heater 1. and a gas type switching switch 55 that is set at the time of installation of the water heater depending on the type of fuel gas. Many types of fuel gas can be used, such as LP gas, gaseous fuels such as city gas 13A and city gas 6C, liquid fuels such as petroleum, etc., and these are selectively switched by the gas type changeover switch 55.

The main controller 54 and the sub-controller 54a are temperature setting means set 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 are operated by respective operation switches 56, 5.
6a, and a hot water temperature setting switch 5 for setting the hot water temperature.
7, 57a are provided.

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 inflow 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 amount of electricity supplied to the governor proportional valve 23 based on 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 connected to the water heater 1
In order to obtain an appropriate amount of gas by correcting errors due to variations in the gas and pressure loss due to the type of gas, a semi-fixed volume is provided to proportionally control the maximum value of the current to the governor proportional valve 23.

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 is the circuit that drives the geared motor in step 3, and the power supply is
In the OFF state, it does not operate, but in the power ON state, the operation switch 56 of the sub-controller 54a
Regardless of whether a is ON or OFF, it is set to the position of the previous set temperature, and from that position it is initially set to a position corresponding to the reference temperature.

The position detection circuit 75 is a circuit for analyzing a signal from the potentiometer 34 provided in the water volume proportional adjustment valve 33 to detect its opening degree.

The water inflow amount detection circuit 76 detects an update signal of the water flow signal (water inflow amount) based on the rotational speed signal of the water amount sensor 36.

The method of detecting the update signal of the communication signal is based on the amount of water entering per certain sampling time t (for example, 1 to 4.0
/min) changes from the previous water inflow data (steady flow) by more than a predetermined water amount (predetermined value: 1.5 to 4.0/min, for example), it is detected as an update signal of the water flow signal.

The incoming water amount detection circuit 76 of this embodiment detects as a water flow signal when the water amount signal from the water amount sensor 36 is equal to or higher than a predetermined voltage per certain sampling time. If a reading error occurs and the set voltage is kept constant, it will cause chattering. Therefore, in this example, a hysteresis characteristic is provided to prevent chattering, and the amount of water inflow is compared to past water inflow data. Predetermined amount of water (predetermined value: 2.5/min)
When it increases or decreases, it is detected as a water flow signal. Moreover, when there is a minute change such as a change of 2.0/min or less, it is not detected as an update signal of the water flow signal.

Normally, data on the amount of water entering is updated every sampling time, but if there is a slight change in the amount of water that continues for a certain period of time, or when the water amount sensor 36
In consideration of the case where accurate water volume cannot be detected due to response delay, the cumulative value of minute changes in water volume within a certain time period longer than the sampling time increases or decreases by more than a predetermined water volume (predetermined value: 2.5/min). Even if this occurs, it is detected as an update signal for the water flow signal.

The CPU 70 has a memory function that stores the reference temperature 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 discrimination function that discriminates between the main controller 54 and the sub-controller 54a. , sequence control for controlling the operating order and timing of each of the above circuits;
Feed forward control (hereinafter referred to as FF control) which controls the combustion amount and water input amount based on the input water temperature, set temperature and water flow signal as combustion capacity control;
Automatic adjustment of gas amount based on outlet hot water temperature and water flow signal, ON/OFF of switching valve 24, combustion fan 12
Feedback control (hereinafter referred to as FB control) that performs proportional-integral control (hereinafter referred to as PI control) of combustion volume and air volume adjustment, and switching control that does not switch between FF control and FB control. It also has functions.

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 the user opens the hot water tap and an update signal of the water flow signal based on the water flow sensor 36 is detected, the combustion fan 12 is activated, and after pre-purging is performed for a predetermined time, the ignition is performed. perform the operation. 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 ignition is detected, the capacity of the combustion amount is calculated, and combustion is performed according to the combustion amount. It begins.

On the other hand, when the incoming water amount detection circuit 76 detects an update signal of the water flow signal based on the water amount signal from the water amount sensor 36, the calculation of the combustion amount based on the incoming water temperature thermistor 35 starts at the same time. If you read the water temperature when this is not done, the correct water temperature will not be obtained. For this reason, in this embodiment, the incoming water amount detection circuit 76 reads the water temperature by the incoming 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.

Combustion capacity control includes FF control that detects the temperature difference between the set temperature and incoming water temperature and the incoming water amount to set the combustion amount and incoming water amount, and FB (PI) control that detects the hot water temperature and corrects the combustion amount and incoming water amount. ) control is performed.

The FF control is based on the first calculated value (required capacity) Q calculated from the temperature difference between the set temperature and the inlet water temperature set by the main controller 54 and the sub-controller 54a and the inlet water amount, and the temperature difference between the inlet water temperature and the outlet water temperature and the input water temperature. The most efficient capacity is calculated from the second calculated value q calculated from the water amount, and 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 air volume, gas volume, and water intake volume.

FF control has a capacity larger than the required capacity Q {Q×
(Q+α)}, which is controlled by proportional control during rapid heating, and proportional control during residual heat purge, which outputs capacity {Q×(Q-β)}, which is smaller than the required capacity Q. The combustion fan 12, the governor proportional valve 23, the switching valve 24, and the water volume proportional adjustment valve 33 are each controlled according to the residual heat purge capacity range to be controlled, thereby automatically adjusting the amount of air and gas and the amount of water entering.

FB control controls the combustion fan 12, the governor proportional valve 23, the switching valve 24, and the water volume proportional adjustment valve 33 based on the deviation between the set temperature and the hot water temperature and the amount of water entering, and adjusts the amount of air, gas, and Automatically adjusts the amount of water entering.

As a safety function, if the temperature of the hot water reaches boiling point or higher and continues for a predetermined period of time (t8 seconds: e.g. 1 to 10 seconds), continuous combustion will continue for a predetermined period of time (t7 minutes:
For example, if the flame continues for 40 to 120 minutes, or if no flame is detected, each solenoid valve is closed and the operation is stopped.

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. 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 water inflow detection circuit 76 detects the water flow signal from the water flow sensor 36, and reads the updated water inflow data based on the flowchart in FIG. 6 (S12). ).

After detecting the current amount of water inflow from the water inflow data,
After a predetermined time (t3 seconds: for example 10 seconds) has elapsed (S13), the amount of water entering is detected by the entering water temperature thermistor 35 (S14). Then, it is determined whether 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 the operation switch 56 of the main controller 54 and subcontroller 54a, 56a is turned off (S17). When the inlet water temperature is lower than 55℃, it is determined whether or not the inlet water temperature is below the set temperature (S18), and when the temperature is higher than the set temperature, the operation in S12 and below is repeated, and when it is below the set temperature, as shown in Figure 4. Turn on the combustion fan 12 to
(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-purging (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 applied 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 Kp, 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.

FIG. 6 explains the detection of the water flow signal by the water inflow amount detection circuit 76 based on a flowchart.

The current amount of water entering is detected by the water amount sensor 36 (S60).

Next, it is determined whether the amount of incoming water detected by the water amount sensor 36 has changed by a predetermined water temperature (predetermined value: 2.5/min) or more (S61).

When the amount of water detected by the water amount sensor 36 changes by 2.5/min or more with respect to past water inflow data, that is, when it increases or decreases by 2.5/min or more with respect to past water inflow data, It is detected as an update signal of the water flow signal based on past water inflow data (S62).

Further, when the amount of water inflow detected by the water amount sensor 36 has a minute change amount of 2.0/min or less with respect to past water inflow data, it is not detected as an update signal of the water flow signal. Therefore, by providing a hysteresis characteristic, it is possible to prevent chattering even if a reading error occurs in the water input amount detection circuit 76 due to the right mixing of the water flow, etc.

Then, the water inflow data is updated. That is, the amount of water that is obtained by adding or subtracting the changed water temperature (increase or decrease in water temperature) to the past water amount data is input as the current water amount data. Here, if the water inflow does not change by 2.5/min or more, the past water inflow data is set as the current water inflow data (S63).

After a certain sampling time t (seconds) has elapsed since inputting the water inflow data (S64), the water inflow detected by the water flow sensor 36 changes again by more than a predetermined water temperature (predetermined value: 2.5/min). It is determined whether or not there is one (S65). When the water inflow rate changes by 2.5/min or more, repeat the operation flow chart below S62.

When the water inflow rate does not change by more than 2.5/min,
Considering the case where a slight change in the amount of water entering the water continues for a certain period of time or the case where accurate water temperature cannot be detected due to a delay in the response of the water amount sensor 36, the amount of small change in the amount of water entering within a certain period of time is calculated. It is determined whether the cumulative value has changed by more than a predetermined water temperature (predetermined value: 2.5/min) (S66), and even if the cumulative value of minute changes in the amount of water entering within a certain period of time has changed by more than a predetermined value. Detected as a water flow signal update signal and repeats the operations from S52 onwards. If the cumulative value of the minute changes in the amount of water entering within a certain period of time does not exceed a predetermined value, the operations from S63 onwards are repeated.

Therefore, in the conventional method of detecting the amount of water entering, if the pulse output from the water amount sensor is sufficiently smoothed, a response delay may occur, or if a quick response is obtained, ripples may occur. Since controlling the proportional valve would cause problems such as chattering, small changes in the amount of water entering due to ripples were not detected, and changes in water temperature exceeding a certain amount were detected as an update signal for the amount of water entering. In addition to detecting instantaneous increases and decreases in the amount of water flowing in, the system also detects as an update signal for the water flow signal when the cumulative value of minute changes in the amount of water entering, such as ripples, changes to a predetermined value or more within a certain period of time. I try to do that.

Therefore, it is possible to adjust the supply voltage of the combustion fan 12 and the energizing current of the governor proportional valve 23 in response to a wide range of water temperature changes that can deal with minute changes in the amount of water entering, such as ripples, so that The optimal amount of gas and air can be controlled.

Next, after the combustion capacity control shown in the flowcharts of FIGS. 7 and 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. 7 mainly shows a flowchart of FF control among combustion capacity controls.

After performing the operation of S39 in FIG. 5, the first calculated value Q and the second calculated value q are calculated based on the following calculation formulas (S100) and (S101).

Equation 1...First calculated value Q=(Tset-THin)×w = Required capacity Equation 2...Second calculated value q=(THout-THin)×w = Current ability in transition period Tset: Set temperature THin : Incoming water temperature THout : Outgoing water temperature w : Incoming water amount After calculating the first calculated value Q and the second calculated value q, it is determined whether FF control has been performed (S102),
If FF control is being performed, FB (PI) control from S119 shown in the flowchart of FIG. 8 is performed.

In addition, it is determined whether a predetermined time (t9 seconds: for example, 1 second) has elapsed after the initial setting of the water volume proportional adjustment valve 33 (S103), and after t9 seconds have passed, Q≧
qx or not (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),
Switching valve 24 according to the required capacity Q calculated in S100.
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 slow heating capacity (Q x 1.0) as the required capacity 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) that provides the slow heating capacity (Q x 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.

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 capacity 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 capacity Q, and the fan drive circuit 72, proportional valve control circuit 73, and geared motor drive circuit 74 are controlled (S107).

In other words, when the switching valve 24 is turned off (half-open capacity operation) according to the required capacity Q calculated in S100, the opening degree (gas amount) that provides the minimum capacity in the half-open capacity control area 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 capacity Q calculated in S100, the opening degree (gas amount) is adjusted so that the minimum value of the capacity in the full open capacity control area is obtained. The current applied to the governor proportional valve 23 is adjusted. Further, 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 and w is the amount of water input, for example, if the capacity of the heat exchanger 13 is
At the time of 500 c.c., the coefficient a is 20 [1/] and the water inflow w
When is 5 [/sec], τ ₁ is set to 4 seconds, and when the water input amount w is 10 [/sec], τ ₁ is set to 2 seconds.

Then, after the FF control time has passed a predetermined time (τ ₁ second: e.g. 2 to 4 seconds) that is a function of the amount of water input (S109), the relaxation heat capacity (Q×
1.0), the fan drive circuit 72,
The proportional valve control circuit 73 and the geared motor drive circuit 74 are controlled (S110). Note that 1.0 of (Q×1.0) is a coefficient.

In other words, the same slow heating capacity as the required capacity Q (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, as shown in the flowchart of Figure 8,
Performs FB (PI) control for S123 and below.

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 it is within |℃ (=±y℃) (S111), and if the deviation is within |dt|℃, perform S110,
When the deviation is not within |dt|℃, continue to S109
I do.

When Q≧qx, that is, when the hot water temperature does not reach the set temperature, it is determined whether the deviation between the set temperature (Tset) and the hot water hot water temperature (THout) is within |dt|(=±y)℃. (S112), when the deviation is within |dt|°C, 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 capacity Q calculated in S100. Then, so as to output a rapid heating capacity {Q×(Q+α)/Q} larger than the required capacity Q,
The fan drive circuit 72, proportional valve drive circuit 73, and geared motor drive circuit 74 are controlled (S113).
Then, the operations from S112 onwards are repeated. In addition, (Q
+α)/Q is a coefficient, for example, 1.75 when α is Q×3/4kcal.

In other words, the maximum capacity {Q
×(Q+α)/Q} target opening (gas amount)
The current supplied to the governor proportional valve 23 is adjusted by proportional control using 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.

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 input, the first calculated value Q, which is the required capacity, is updated, and if the governor proportional valve 23 is activated at this time, the change in the gas amount and the change in the amount of water input will interfere, and the temperature of the hot water being discharged will be affected. Therefore, when changing the opening degree (inflow amount) of the water temperature proportional adjustment valve 33, proportional control of the capacity (gas amount) by the governor proportional valve 23 is not performed.

FIG. 8 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 outlet temperature (THout) is more than +y℃ (for example, +5℃) (S119), and when the deviation is more than +y℃, the required capacity Q is determined. Small residual heat purge capacity {Q
The fan drive circuit 72, proportional valve control circuit 73, and geared motor drive circuit 74 are controlled to output x(Q-β)/Q} (S120). In addition,
(Q-β)/Q is a coefficient, for example β is Q x 1/4 kcal
It is assumed to be 0.6.

That is, first, the governor proportional valve 23 is throttled to a target opening that provides a minimum capacity {Q×(Q-β)/Q} smaller than the required capacity Q. and,
Switching valve 24 according to the required capacity Q calculated in S100.
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 (S121), safety control from S41 shown in the flowchart of FIG. 5 is performed. Furthermore, if t10 seconds have not elapsed, the operations from S119 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 (S123).

Temperature deviation: e = set temperature - hot water temperature ∴ F (e) = (K ₁ - e) × k ₁ K, k are constants Incoming water volume w is a known quantity detected by the water flow sensor ∴ G (w) = (K _{2 − e} ) ] is shorter or the amount of water entering is larger, the integration time is shorter, and the output time to the governor proportional valve 23 or the water temperature proportional adjustment valve 33 is shorter.

Then, the integration time (T time: e.g. 150 seconds)
has elapsed (S124), it is determined whether the temperature deviation e≦1 or not (S125). If e≦1, safety control is performed as shown in S41 of the flowchart shown in FIG.
When it is not ≦1, input the gas type Kp of the fuel gas (S126), update the PI control output below so as to switch to the proportional control constant according to the gas type Kp,
After outputting the proportional control constant of the PI control output to the governor proportional valve 23 or water volume proportional adjustment valve 33 as a temperature deviation function (S127), safety control from S41 shown in the flowchart of FIG. 5 is performed.

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 input flow rate is less than the specified flow rate. When the amount of water is
Maximum value of PI control output PN {Q×(Q+α)/Q}
is brought close to the slow heating capacity (Q x 1.0), which is the same as the required capacity Q, to improve safety in minute flow.

Therefore, by switching to a proportional control constant according to the load such as gas type Kp, gas amount, and water input amount, the gas amount can be increased or decreased (variable rather than fixed value), and can be used over a wide range and freely. PI control can be performed. Furthermore, 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.

[Modification] In this embodiment, gaseous fuel such as fuel gas is used as the fuel, but 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 of water flow signal detection, FIG. 7 is a flowchart mainly of FF control according to an embodiment of the present invention, and FIG.
The figure is a flowchart of FB control according to an embodiment of the present invention. In the figure 1...Gas combustion water heater, 11...Gas burner, 12...Combustion fan (blower), 13...Heat exchanger, 23...Governor proportional valve (fuel supply amount control means), 35...Water inflow thermistor (Water inflow amount Detection means), 36...Water amount sensor (water input amount detection means), 38
... Hot water temperature thermistor (hot water amount detection means), 50...
Control device, 54... Main controller (temperature setting means), 54a... Sub controller (temperature setting means), 60... Control circuit, 76... Water inflow detection circuit.

Claims (1)

[Claims] 1 (a) a burner for burning fuel; (b) a fuel supply amount control means for controlling the amount of fuel supplied to the burner; (c) supplying combustion air to the burner. (d) a heat exchanger that heats water passing through the heat exchanger using the heat of the burner; (e) provided upstream of the heat exchanger to detect the temperature of water flowing into the heat exchanger; (f) Outlet water temperature detection means for detecting the outlet temperature of water flowing out from the heat exchanger; (g) Temperature setting means for setting the outlet water temperature to a desired set temperature; h) an inflow water amount detection means for detecting an inflow water amount flowing into the heat exchanger; (i) the inflow water temperature detection means detects an inflow water amount that has changed by a predetermined amount of water with respect to a past inflow amount per certain sampling time; The water inflow amount is detected as an update signal of the water flow signal when detected, and is detected as an update signal of the water flow signal when the cumulative value of minute changes within a certain time period that is larger than the sampling time reaches the predetermined water amount. a detection circuit; (j) when the water inflow detection circuit detects an update signal of the water flow signal, updates the inflow amount to a value obtained by increasing or decreasing the past water inflow amount by the amount of change; Performs feedforward control to control the fuel supply amount control means and the blower based on the input water temperature and the set temperature, and controls the fuel supply amount control means and the blower based on the updated input water amount and the outlet hot water temperature. A water heater equipped with a control circuit that performs feedback control.