JPH0473051B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a water heater that adjusts the amount of water entering a heat exchanger by controlling a water amount proportional adjustment valve according to a set temperature.

[Prior Art] Conventionally, an inlet water temperature sensor detects the temperature of water flowing into a heat exchanger, a setting unit sets the outlet temperature of water flowing out from the heat exchanger to a desired set temperature,
2. Description of the Related Art There is a gas combustion water heater equipped with a water amount proportional adjustment valve that adjusts the amount of water flowing into a heat exchanger according to the temperature difference between a set temperature and an incoming water temperature.

For this water heater, turn on the operation switch, then input the set temperature, and then control the opening of the water volume proportional adjustment valve so that the amount of water input corresponds to the temperature difference between the set temperature and the incoming water temperature. are doing.

[Problems to be Solved by the Invention] Generally, in the proportional water flow control of a water heater, control is performed such that the lower the set temperature, the greater the amount of water flowing into the heat exchanger. For this reason, the temperature of the heat exchanger also becomes low, so that when the combustion gas from the burner comes into contact with the wall surface of the heat exchanger, it is cooled.

Then, when the temperature of the combustion gas is cooled to below the dew point temperature, water vapor in the combustion gas condenses and dew begins to adhere to the wall surface of the heat exchanger. Therefore, from the viewpoint of durability of the water heater, it is not preferable to increase the amount of water input until the temperature of the combustion gas falls below the dew point temperature.

An object of the present invention is to provide a water heater that improves durability by preventing the temperature of a heat exchanger from dropping below the dew point temperature of combustion gas.

[Means for Solving the Problems] The water heater of the present invention includes a burner that burns combustion air and fuel at a predetermined air-fuel ratio, and a heat source that heats water passing through the interior with combustion gas from the burner. an exchanger, a water volume proportional adjustment valve that adjusts the amount of water flowing into the heat exchanger, and a temperature setting means that sets the outlet temperature of water flowing out of the heat exchanger to a desired set temperature; a water inflow detection means for detecting the amount of water flowing into the heat exchanger; a maximum water inflow amount that takes into consideration the set temperature set by the temperature setting means and the dew point temperature of the combustion gas; A technical means including a control circuit for controlling the opening degree of the water amount proportional adjustment valve so that the amount of water inflow detected by the water amount detection means is equal to or less than the maximum amount of water inflow is adopted.

[Operation and Effects of the Invention] The water heater of the present invention adjusts the amount of water flowing into the heat exchanger so that it is equal to or less than the maximum amount of water that is set according to the set temperature and the dew point temperature of the combustion gas. By doing so, it is possible to prevent the temperature of the heat exchanger from dropping below the dew point temperature of the combustion gas. That is, the temperature of the heat exchanger can be maintained higher than the dew point temperature of the combustion gas.

Therefore, even if the combustion gas comes into contact with the heat exchanger, the combustion gas will not be cooled below the dew point temperature, so the water vapor in the combustion gas will not condense, and dew will adhere to the walls of the heat exchanger. It disappears. Therefore, problems such as corrosion of the heat exchanger can be prevented, and the durability of the water heater can be improved.

[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. .

The combustor case 10 also includes a combustion fan 12 that uses a three-phase Y-connected brushless DC motor and changes the amount of air by changing the number of rotations depending on the supplied voltage.

The gas burner 11 is a forced-air combustor that burns combustion air supplied by the combustion fan 12 and fuel gas supplied from the gas supply pipe 20 at a predetermined air-fuel ratio. The combustion gas generated by this 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 11 in the combustor case 10
A sparker 14, which is an ignition device, and a flame rod 15, which is a flame detection means, are provided near the ignition device.

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 adjusts the supply amount of fuel gas (hereinafter referred to as gas amount) by controlling the supply pressure, and brings the fuel gas to the second burner 11b into a use state. A switching electromagnetic valve (hereinafter abbreviated as a switching valve) 24 that shuts off accordingly is provided, and supplies 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 thereof, and a water volume proportional adjustment valve 33 that adjusts the amount of water entering the heat exchanger 13 according to the degree of opening is provided. is driven by a geared motor and includes a potentiometer 34 for detecting its opening.

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.
Furthermore, the amount of water entering is detected by a water amount sensor 36 which is a water amount detecting means downstream of the water entering 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 provided a hot water temperature thermistor 38, which is a hot water temperature detecting means for detecting the hot water temperature of the water flowing out from the heat exchanger 13, when the hot water temperature reaches the boiling temperature or higher. A boil prevention switch 39 that is turned on is provided, and a hot water tap (not shown) attached to a hot water supply location is provided at the most downstream side. The outlet hot water temperature thermistor 38 outputs an overcapacity signal when the outlet hot water temperature is lower than the set temperature by a predetermined temperature difference.

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. It is equipped with a terminal.

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 outlet hot water temperature setting switches 57, 57a for setting the outlet hot 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 installed in a Y-phase Y-wired brushless DC motor detects its rotational speed and outputs a detection signal.
Send to CPU70.

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 a semi-fixed volume that proportionally controls the maximum value of the current 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 is equipped with

The geared motor drive circuit 74 is a circuit that drives a geared motor that changes the opening degree of the water volume proportional adjustment valve 33 for adjusting the amount of water flowing into the heat exchanger 13, and does not operate when the power is off, but when the power is on. Through the operation, the operating switch 56a is initially set from the previous set temperature position to the position corresponding to the reference temperature, regardless of whether the operating switch 56a is on or off. In this geared motor drive circuit 74, especially the water amount proportional adjustment valve 3
Detect the opening degree of 3.

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 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 F/V conversion.

The CPU 70 has a memory function that stores a reference temperature, which is a first set hot water temperature that is set in advance at the stage of assembling the water heater 1, and the type of fuel gas to be used, and distinguishes between the main controller 54 and the sub-controller 54a. It performs a determination function to perform a determination function, a sequence control to control the operating order and timing of each of the above-mentioned circuits, and a combustion capacity control to control the combustion amount of the gas burner 11, and also has safety 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 a water flow signal based on the water flow sensor 36 is obtained, the combustion fan 12 is activated, and after pre-purging is performed for a predetermined period of time, ignition is performed. In this ignition operation, the main solenoid valve 21, the main solenoid valve 22, the cabana 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 starts according to the combustion amount. .

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.

Combustion capacity control includes feed-forward control (hereinafter referred to as FF control), which controls the combustion amount and water input amount based on the temperature difference between the inlet water temperature and the set temperature (reference temperature) and the amount of water input, and the feed forward control (hereinafter referred to as FF control) that controls the amount of combustion and water input based on the temperature difference between the inlet water temperature and the set temperature (reference temperature), and the feed forward control (hereinafter referred to as FF control). Feedback control (hereinafter referred to as FB control) that performs proportional-integral control (hereinafter referred to as PI control) to correct the combustion amount and water input amount based on the deviation from the (reference temperature);
FF→FB (PI) switching control is performed to switch between FF control and FB control.

FF control uses the first calculated value (required capacity) calculated from the temperature difference between the set temperature and incoming water temperature and the amount of incoming water.
Q, the second calculated value calculated from the temperature difference between the incoming water temperature and the outgoing water temperature, and the amount of incoming water (current capacity during the transition period) q
According to the comparison results, the combustion fan 12, governor proportional valve 23, and
A slow heating capacity range controlled by the proportional control of the switching valve 24 and the water volume proportional adjustment valve 33, and an output (maximum capacity combustion) that results in a rapid heating capacity {Q×(Q+α)/Q} that is larger than the required capacity Q. Combustion fan 12, governor proportional valve 23, switching valve 2 during sudden heating
4. Rapid heating capacity range controlled by proportional control of water volume proportional adjustment valve 33 and combustion during residual heat purge that produces an output of residual heat purge capacity {Q×(Q-β)/Q} smaller than the required capacity fan 12,
Select the residual heat purge capacity range controlled by the proportional control of the governor proportional valve 23, switching valve 24, and water volume proportional adjustment valve 33, and automatically adjust the air volume, gas volume, and water input volume according to these control ranges. Adjust.

In particular, in this embodiment, a half-open capacity control range and a full-open capacity control range are set.

In the case of a water heater 1 having a governor proportional valve 23 that can throttle the governor proportional valve 23 to 1/4 of its full opening, the half-open capacity control range means that when the switching valve 24 is in the closed state, only the first burner 11a controls the governor The combustion amount is proportionally controlled to 1/8 to 1/2 of the full opening capacity of the proportional valve 23.

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
At b, proportional control of the combustion amount is performed to 1/4 to 1 of the full opening capacity of the governor proportional valve 23.

Furthermore, in this embodiment, the maximum value of the half-open capacity control range (1/2 of the full-open capacity of the governor proportional valve 23) and the minimum value of the full-open capacity control range (the governor proportional valve 23
An overlapping control area with 1/4 of the full-open capacity of the engine is set.

In FF control, when the outlet hot water temperature is higher than the set temperature, the minimum capacity corresponds to the minimum value of the half-open capacity control range when the switching valve 24 is OFF, or the minimum value of the fully open capacity control range when the switching valve 24 is ON. It is controlled by proportional control of the combustion fan 12, the governor proportional valve 23, and the water amount proportional adjustment valve 33 at the time of the minimum capacity that produces the output.

In FF control, after initial setting of the opening degree of the water volume proportional adjustment valve 33, a predetermined time {t9 seconds=(heat exchanger 1
When the deviation between the hot water temperature and the set temperature does not approach the predetermined temperature difference (y°C: for example 5°C) even after a period of time (e.g. 1 second) has elapsed, that is,
When the outlet hot water temperature is lower than the set temperature by a predetermined temperature difference (an overcapacity signal is detected from the outlet hot water temperature thermistor 38), the opening degree of the water volume proportional adjustment valve 33 is determined by the deviation between the set temperature and the outlet hot water temperature. At the same time, the combustion capacity of the gas burner 11 is reduced for a predetermined time {τ ₂ seconds = b - cw: for example, 5
By fixing the capacity to the maximum capacity by 2 seconds), changes in the amount of combustion (air amount and gas amount) and changes in the water input amount correction operation are prevented from interfering with each other. In addition,
When b is 12 seconds and c is 0.7 ^seconds2 /, w is 10/
If w is 5/min then τ ² is 5 seconds and τ ₂ is 9 seconds. (w = water inflow amount) When the proportional control of the combustion fan 12 and governor proportional valve 23 reaches near the maximum range of the half-open capacity control range (for example, the maximum value of the half-open capacity control range) by FB control, slow ignition is performed. While controlling, the switching valve 24 is turned on (opened) and switched to full-open capacity operation.

By FB control, when the proportional control of the combustion fan 12 and the governor proportional valve 23 reaches around the minimum range of the full-open capacity control range (for example, the minimum value of the full-open capacity control range), the supply voltage of the combustion fan 12 and By turning off (closing) the switching valve 24 and switching to half-open capacity operation without changing the energizing current of the governor proportional valve 23, it is possible to smoothly switch between half-open capacity operation and full-open capacity operation while maintaining a safe combustion state. Performs switching control.

In FF → FB (PI) switching control, the deviation between the set temperature and the hot water temperature is a predetermined temperature difference (±y℃: for example, ±5
℃), switch from FF control to PI control. Alternatively, in FF control, even when the deviation |dt| between the set temperature and the hot water temperature does not reach the predetermined temperature difference (±y℃: for example, ±5℃) during the minimum capacity output,
A predetermined time (τ ₁ second = a/w:
For example, when a period of 2 to 4 seconds has elapsed, the FF control is switched to the PI control. In addition, when outputting the rapid heating capacity in FF control, even if the deviation |dt| between the set temperature and the outlet hot water temperature does not reach the predetermined temperature difference (±y℃: for example, ±5℃), the output hot water temperature thermistor 38 will signal an overcapacity signal. Even when detecting water, if a predetermined time (τ ₂ seconds = b - cw: e.g. 5 to 9 seconds) that is a function of the amount of water entering has elapsed, the FF control will start.
Switch to PI control.

Generally, in the proportional water flow control of the water heater 1, the lower the set temperature, the greater the amount of water entering the water heater 1, but the heat exchanger 13
Increasing the amount of water flowing into the heat exchanger 13 until the temperature of the wall surface falls below the dew point temperature of the combustion gas may cause malfunctions such as corrosion of the heat exchanger 13 and the water heater 1 unfavorable in terms of durability. Note that the dew point temperature of fuel gas depends on the air-fuel ratio, gas components,
It is determined from the gas amount and saturated vapor pressure, and the heat exchanger 13
The wall surface temperature is determined from the amount of water entering, the characteristics of the heat exchanger 13, and the physical property values of the water. Therefore, in this embodiment, the opening degree of the water amount proportional adjustment valve 33 is controlled so that the amount of water input is equal to or less than the maximum amount of water that is set according to the set temperature and the dew point temperature of the combustion gas. The wall temperature is maintained higher than the dew point temperature of the combustion gas.

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 and the graph of FIG. 9. 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 to 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 7 is designed to prevent equipment failure even in such a case.
The predetermined energization time to the geared motor according to 4 (t1
When a period of time (for example, 5 to 30 seconds) has elapsed (S6), the geared motor is turned 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 reading errors occur in the water amount detection circuit 76 due to undulations of the water flow, etc., and the set voltage is kept constant. 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 20/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 (S21). 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).

The current applied to the governor proportional valve 23 is controlled based on the rotational speed of the combustion fan 12, that is, the amount of air 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 made to be a constant ratio 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, when the sparker 14 is turned on, the sparker 14 is turned off after a predetermined time (t5 seconds: for example, 5 to 20 seconds) has elapsed (S35) (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 outlet water temperature has not reached the boiling temperature, the set temperature is input again (S46), and then 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.
OF (S48-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 first calculated value (required ability) Q and the second calculated value q are calculated based on the following formula (S100), (S101).

Equation 1...First calculated value Q = (Tset-THin) x w = Required capacity Equation 2... Second calculated value q (THout-THin) x w = Current ability during 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 or not the combustion amount and incoming water amount have been set by FF control ( S102), if the combustion amount and water input amount are set by FF control,
Gas amount control is performed in S119 and subsequent steps shown in the flowchart of FIG.

In addition, if the combustion amount and water input amount are not set by FF control, the water amount proportional adjustment valve 33
It is determined whether a predetermined time (t9 time: for example, 1 second) has elapsed after the initial setting of the opening degree (S103). Note that t9 seconds is calculated from (heat capacity of heat exchanger 13)/(required capacity Q).

Then, after t9 seconds have elapsed, it is determined whether Q≧qx (S104). Here, x is, for example, 1.5
, and the first calculated value Q
Based on the comparison result between q and the second calculated value q, water heater 1
This is used to determine whether a cold start is possible. Q
When not ≧qx, it is determined whether Q<q or not (S105), and when Q<q is not, 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).

Then, set the hot water temperature (THout) to the set temperature (Tset).
In order to approach the temperature, a target opening degree of the water volume proportional adjustment valve 33 is set according to the deviation between the set temperature (Tset) and the outlet hot water temperature (THout), and the target opening degree is output to the geared motor drive circuit 74.

Also, the same slow heating capacity as the required capacity Q (Q x 1.0)
The target combustion amount of the gas burner 11 (the target opening degree of the governor proportional valve 23 and the combustion fan 1
2) and sends the target combustion amount signal to the fan drive circuit 72 and the proportional valve control circuit 73.
(S106). In addition, 1.0 out of (Q×1.0)
is the coefficient.

That is, the geared motor is driven so that the opening degree of the water volume proportional adjustment valve 33 becomes a target opening degree according to the deviation between the set temperature (Tset) and the outlet temperature (THout). Then, the same slow heating capacity as the required capacity Q (Q×
1.0), the voltage supplied to the combustion fan 12 and the current supplied to the governor proportional valve 23 are adjusted by proportional control so as to achieve the target rotational speed and target opening degree.

After that, in the FF control, if there is an error due to variations in the output corresponding to a large change, the tapped water temperature will not reach the set temperature, so the FF control is switched to gas amount control at S119 or lower shown in the flowchart of FIG.

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.

Then, in order to bring the outlet hot water temperature close to the set temperature, a target opening degree of the water flow proportional adjustment valve 33 is set according to the deviation between the set temperature (Tset) and the outlet hot water temperature (THout), and the target opening degree is controlled by the geared motor. Drive circuit 7
Output to 4.

In addition, the target combustion amount of the gas burner 11 (the target opening degree of the governor proportional valve 23 and the target rotation speed of the combustion fan 12) is set so that the minimum capacity smaller than the required capacity Q is output, and the target combustion amount is set. A signal is output to the fan drive circuit 72 and the proportional valve control circuit 73 (S107).

That is, the geared motor is driven so that the opening degree of the water volume proportional adjustment valve 33 becomes a target opening degree according to the deviation between the set temperature (Tset) and the outlet temperature (THout). For example, the opening degree of the water volume proportional adjustment valve 33 is opened. When the switching valve 24 is turned off (half-open capacity operation) according to the required capacity Q calculated in S100, the target rotation speed and target opening degree are set such that the minimum value of the capacity in the half-open capacity control area is obtained. supply voltage to the combustion fan 12 and the governor proportional valve 2.
3 is regulated 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 target rotation speed and target opening degree are set such that the minimum value of the capacity in the full open capacity control range is obtained. The voltage supplied to the combustion fan 12 and the current supplied to the governor proportional valve 23 are adjusted.

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, when the heat capacity of the heat exchanger 13 is 500 c.c., when the coefficient a is 20 [1/] and the amount of water input w is 5 [/sec], τ ₁ is assumed to be 4 seconds, and when the amount of water entering w is 10 [/second], τ ₁ is assumed to be 2 seconds.

Then, the FF control time to output the minimum capacity is a predetermined time (τ ₁ second: for example 2 to
4 seconds) have elapsed (S109).
Note that the predetermined time (τ ₁ second: for example, 2 to 4 seconds) is a function of the amount of water entering, that is, the amount corresponding to the current excess or deficiency and the heat capacity of the appliance, and is calculated only during the response delay of the hot water temperature thermistor 38. It is waiting for control of the combustion amount of the gas burner 11.

When τ ₁ second has elapsed, the target combustion amount of the gas burner 11 (the target opening degree of the governor proportional valve 23 and the target rotation of the combustion fan 12 ), and sends the target combustion amount signal to the fan drive circuit 72.
is output to the proportional valve control circuit 73 (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×
1.0), the voltage supplied to the combustion fan 12 and the current supplied to the governor proportional valve 23 are adjusted so that the target rotational speed and target opening degree are obtained.

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, so gas amount control below S119 shown in the full chart in Figure 7 can be switched to

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, the deviation between the set temperature (Tset) and the hot water hot water temperature (THout) is |dt|℃ (=±y
℃: for example, ±5℃) (S112), and if 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 capacity Q calculated in S100.

Then, set the hot water temperature (THout) to the set temperature (Tset).
To quickly raise the temperature to
A target opening degree of the water volume proportional adjustment valve 33 is set according to the deviation between the temperature and the outlet hot water temperature (THout), and a signal of the target opening degree is output to the gear motor drive circuit 74.

Also, the maximum ability {Q×
The target combustion amount of the gas burner 11 (the target opening degree of the governor proportional valve 23 and the target rotation speed of the combustion fan 12) is set so as to output (Q+α)/Q},
A signal indicating the target combustion amount is output to the fan drive circuit 72 and the proportional valve control circuit 73 (S113). In addition,
(Q+α)/Q is a coefficient, for example α is Q×3/4Kca
It is assumed to be 1.75.

That is, the opening degree of the water volume proportional adjustment valve 33 is quickly narrowed down to the opening degree according to the deviation between the set temperature (Tset) and the outlet hot water temperature (THout). And the required ability Q
The voltage supplied to the combustion fan 12 and the current supplied to the governor proportional valve 23 are proportionally controlled so that the target rotation speed and target opening degree are obtained to obtain a larger maximum capacity {Q×(Q+α)/Q}. adjusted.

Next, the predetermined time {τ ₂ = b−
cw [seconds]} (S114). Note that b and c are coefficients, and w is the amount of water input. For example, when the heat capacity of the heat exchanger 13 is 500 c.c., the coefficient b is 12.5 [seconds] and the coefficient c is
0.7 [second ² /], when the water input amount w is 5 [/second], τ ₂ is set to 9 seconds, and when the water input amount w is 10 [/second], τ ₂ is set to 5.5 seconds.

Then, the FF control time due to the rapid heating ability is a predetermined time (τ ₂ seconds: for example, 5 to 9
(seconds) have elapsed (S115). In addition, the predetermined time (τ ₂ seconds: for example, 5 to 9 seconds) is a function of the amount of water entering, that is, the amount corresponding to the current excess or deficiency and the heat capacity of the water flow equipment such as the heat exchanger 13 is calculated, and the exit hot water temperature is determined. Control of the combustion amount of the gas burner 11 is on standby only during the response delay of the thermistor 38.

As described above, when the opening degree (inflow water amount) of the water volume proportional adjustment valve 33 is changed, when the outlet water temperature reaches the set temperature or the predetermined time {τ ₂ = b - cw [seconds]} has elapsed. By burning the gas burner 11 at its maximum capacity until then, it is possible to prevent interference between a change in the amount of gas and a change in the amount of water entering, so that the temperature of the hot water outlet is not affected and the temperature of the outlet hot water can be set quickly.

The FF control time due to the rapid heating ability is the specified time (τ ₂
seconds: e.g. 5 to 9 seconds), in order to stabilize the hot water temperature (THout), the residual heat purge capacity is smaller than the required capacity Q {Q × (Q - β) /
Q}, the target combustion amount of the gas burner 11 (target opening degree of the governor proportional valve 23 and target rotation speed of the combustion fan 12) is set, and a signal of the target combustion amount is sent to the fan drive circuit 72. It is output to the proportional valve control circuit 73 (S116). In addition, (Q-β)/Q
is a coefficient, for example 0.6 when β is Q x 1/4kca
It is said that

In other words, the voltage supplied to the combustion fan 12 and the voltage applied to the governor proportional valve 23 are adjusted so that the target rotation speed and opening degree are such that a residual heat purge capacity {Q×(Q-β)/Q} smaller than the required capacity Q is obtained. The energizing current is adjusted by proportional control.

After that, FF control is output as an output corresponding to a large change, so if there is an error due to variation, the outlet temperature will not reach the set temperature, so the gas amount control below S119 shown in the flowchart of Figure 7 can be switched to

In addition, when the FF control time due to the rapid heating ability has not passed the predetermined time (τ ₂ seconds: e.g. 5 to 9 seconds), the set temperature (Tset) and hot water temperature (THout)
It is determined whether the deviation from ｜dt
When the difference is not within |, it is determined whether or not there is a change in the outlet hot water temperature that is less than or equal to the temperature difference Δy in the outlet hot water temperature in a predetermined time Δt (S118). When there is a change in the outlet hot water temperature by Δy/Δt or less, S116 is performed, and when there is no change in the outlet hot water temperature by Δy/Δt or less, the operations from S115 onwards are repeated.

FIG. 7 shows a flowchart of gas amount control during the transition period to small capacity (when the hot water temperature overshoots).

It is determined whether the deviation between the set temperature (Tset) and the outlet hot water temperature (THout) is greater than or equal to +y°C (for example, +5°C) (S119). When the deviation is +y℃ (e.g. +5℃) or more, the ability smaller than the required ability Q {Q×(Q-
The target combustion amount of the gas burner 11 (the target opening degree of the governor proportional valve 23 and the target rotation speed of the combustion fan 12) is set so as to output β)/Q}, and the signal of the target combustion amount is used to drive the fan. It is output to the circuit 72 and the proportional valve control circuit 73 (S120). In addition, (Q-
β)/Q is a coefficient, for example, 0.75 when β is Q×1/4kcal.

Then, after the output time of the FF control output (t10 seconds: for example, 30 seconds) has elapsed (S121), the safety control from S41 shown in the flowchart of FIG. 5 is performed. Also, if t10 seconds have not elapsed, S119
Repeat the following actions.

Therefore, the deviation (e) between the set temperature (Tset) and the outlet hot water temperature (THout) is +y℃ (for example, +5℃)
In the above case, the output time (t10 seconds: e.g.
30 seconds), FF control output {Q×(Q-β)/Q}
becomes.

In addition, the set temperature (Tset) and hot water temperature (THout)
When the deviation from (S123).

The temperature deviation function is: ∴F(e)=(K ₁ − e)×k ₁ K ₁ , k ₁ is a constant e = set temperature − outlet water temperature The water input function is: ∴G(w)=(K ₂ − w )×k ₂ K ₂ , k ₂ are constants Integral time is: ∴T={F(e)+G(w)} = {(155-e)×1/8+(80-w)×1/8} = Output time of PI control Therefore, the deviation (e) between the set temperature (Tset) and the outlet temperature (THout) is +y℃ (for example, +5℃)
When it is less than, the larger the deviation (e) or the amount of water input.
The more (w), the shorter the variable update time (integration time) T [seconds] of the PI control output. Further, the smaller the deviation (e) or the smaller the amount of water input (w), the longer the variable update time (integration time) T [seconds] of the PI control output.

Then, the integration time (T seconds: e.g. 150 seconds)
has passed (S124), it is determined whether the temperature deviation e≦1 (S125), and when e≦1, that is, the deviation (e) between the set temperature (Tset) and the outlet hot water temperature (THout) is 1. ℃ or below, the flowchart shown in Figure 5
Performs safety control below S41.

In addition, when e≦1, that is, when the deviation (e) between the set temperature (Tset) and the outlet temperature (THout) is not less than 1°C, input the gas type Kp of the fuel gas (S126), The fan drive circuit 7 updates the PI control output based on the following PI control output calculation formula so as to switch to a proportional control constant according to the seed Kp, and the fan drive circuit 7
2 and the proportional valve control circuit 73 (S127).

PI control output: PN=PN-1+e×Kp PI control output variation: ΔVS=e×Kp Current PI control output: PN-1=Q×(Q-
α)/Q ∴PI control output: PN=PN-1+ΔVS In other words, in the operation of S127, the PI control output (proportional control constant to the combustion fan 12 and governor proportional valve 23) is output as a temperature deviation function. Accordingly, the voltage supplied to the combustion fan 12 and the current supplied to the governor proportional valve 23 are adjusted by proportional control so that the target rotational speed and target opening degree are obtained to obtain the PI control output.

However, when the water inflow is less than the predetermined flow rate (5/min), the maximum value of the FF control output is brought close to the output of the slow heating capacity (Q x 1.0), which is the same as the required capacity Q, to stabilize the exit hot water temperature at a minute flow rate. Improving sexuality.

After that, as shown in the flowchart of Figure 5,
Performs safety control below S41.

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. It is possible to update the PI control output. 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.

FIG. 8 shows a flowchart of the maximum water input amount control of the water amount proportional control of the CPU 70. Note that this flowchart is performed when the set temperature is determined.

In this embodiment, water amount proportional control is performed based on data as shown in the graph of FIG. In addition,
The maximum amount of water entering the oil feeder 1 is 16/min. In this example, the dew point temperature of the combustion gas is determined from the air-fuel ratio, gas components, gas amount, and saturated vapor pressure, and the amount of water input, the characteristics of the heat exchanger 13, the physical property values of water, and the
We are looking for the temperature of the wall of No.3.

First, the set temperature set by operating the hot water temperature setting switch 57 of the main controller 54 or the hot water temperature setting switch 57a of the sub-controller 54a is read (S200), and if the set temperature is below a predetermined temperature (for example, 35°C), It is determined whether the temperature is set (S201). Set temperature is 35
When the temperature is set to below ℃, heat exchanger 1
As shown in the graph of Fig. 9, the maximum amount of water flowing into the chamber is determined based on the set temperature and the dew point temperature of the combustion gas (a/min:
For example, 12.6/min) (S202).

Also, when the established temperature is not set to a temperature below 35℃, the set temperature is set to a predetermined temperature (for example, 39℃).
℃) or less is determined (S203). When the set temperature is set to 39°C or lower, the maximum amount of water flowing into the heat exchanger 13 is as shown in the graph of Fig. 9.
Set water input amount determined based on the set temperature and dew point temperature of combustion gas (b/min: e.g. 13.6/min)
(S204).

In addition, when the set temperature is not set to a temperature below 39°C, the maximum amount of water flowing into the heat exchanger 13 is determined by the set temperature and the dew point of the combustion gas, as shown in the graph of Figure 9. The set water input amount (c/min) determined based on the temperature is set to, for example, maximum water input amount x thermal efficiency/set temperature - input water temperature {/min} (S205).

The minimum operating water amount of the water heater 1 in this embodiment is 2/
The maximum operating water flow rate is set at 15 to 16 minutes, but it can be varied depending on the hot water output capacity.

As described above, heat exchange is performed by adjusting the amount of water flowing into the heat exchanger 13 to be equal to or less than the maximum amount of water that is set according to the set temperature and the dew point temperature of the combustion gas. It is possible to prevent the temperature of the vessel 13 from dropping below the dew point temperature of the combustion gas. That is, the temperature of the heat exchanger 13 (approximately the same temperature as the hot water temperature) can be maintained at a higher temperature than the dew point temperature of the combustion gas.

Therefore, even if the combustion gas comes into contact with the heat exchanger 13, the combustion gas is not cooled below the dew point temperature, so the water vapor in the combustion gas does not condense, and dew does not form on the wall of the heat exchanger 13. It will no longer stick. Therefore, problems such as corrosion of the heat exchanger 13 can be prevented, and the durability of the water heater can be improved.

[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 mainly of FF control according to an embodiment of the present invention,
FIG. 7 is a flowchart of gas amount control during the transition period to small capacity according to an embodiment of the present invention, and FIG. 8 is a flowchart of maximum water input flow control of water flow proportional control according to an embodiment of the present invention. FIG. 9 is a graph showing the relationship between outlet hot water temperature and water input amount according to an embodiment of the present invention. In the figure, 1...Gas combustion water heater, 11...Gas burner, 13...Heat exchanger, 33...Water volume proportional adjustment valve, 35...Inlet water temperature thermistor (inlet water temperature detection means), 36...Water flow sensor (Water inflow detection means), 3
8... Outlet hot water temperature thermistor (outlet hot water temperature detection means), 5
0... Control device, 54... Main controller (temperature setting means), 54a... Sub controller (temperature setting means), 60... Control circuit.

Claims (1)

[Claims] 1 (a) a burner that burns combustion air and fuel at a predetermined air-fuel ratio; (b) a heat exchanger that heats water passing through the interior with combustion gas from the burner; (c) a water volume proportional adjustment valve that adjusts the amount of water flowing into the heat exchanger; (d) temperature setting means that sets the outlet temperature of water flowing out of the heat exchanger to a desired set temperature. (e) water inflow detection means for detecting the amount of water flowing into the heat exchanger; and (f) a maximum water input in consideration of the set temperature set by the temperature setting means and the dew point temperature of the combustion gas. A water heater comprising: a control circuit that sets a water amount and controls the opening degree of the water amount proportional adjustment valve so that the amount of water detected by the water amount detection means is equal to or less than the maximum water amount.