JP3077717B2 - Water heater control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an instantaneous water heater.

[0002]

2. Description of the Related Art Conventionally, as described in JP-A-62-26416, in order to move a gas proportional valve in accordance with the response speed of a combustion air supply fan, a set temperature, a supply water temperature, Means for calculating the required amount of heat based on the hot water supply temperature and the amount of supplied water, means for setting the target opening of the gas proportional valve based on the required amount of heat, and a combustion air supply fan which is detected by the target opening of the gas proportional valve and the air volume detecting means. The gas proportional valve is provided with a means for comparing the actual amount of air with the amount of correction and adding a correction amount corresponding to the comparison result to the target proportional valve opening to output a proportional valve opening output signal to the proportional valve output circuit. The opening is not limited to the target opening set based on the actual opening of the combustion air supply fan, that is, the opening is corrected based on the actual rotation speed of the fan. Gas instantaneous water heater gas Reiben control apparatus is known.

[0003]

In the prior art described above, the gas amount (the amount corresponding to the gas proportional valve opening) required to obtain the combustion amount F is F * Kff. If the gas actually used at home is a gas having a higher calorific value or a higher gas pressure than the gas used as a standard for water heater performance, the gas amount G actually required to obtain the combustion amount F is F *
Kff−ΔG. Here, Kff = gas amount / combustion amount. Further, since the gas amount Go actually supplied is adjusted based on the deviation (Ts-Th) between the set temperature Ts and the hot water supply temperature Th that fluctuate with time, the fluctuation Go as shown in FIG. It was stable at F * Kff-ΔG.

On the other hand, since the ratio of the gas amount G to the air amount needs to be kept constant, the fan rotational speed N is equal to the fan rotational speed N = Go * Kn.
(Kn = number of rotations / gas amount).
As shown in (1), it fluctuated with time in synchronization with the gas amount Go actually supplied. Here, the fan rotation speed No when Go = F * Kff−ΔG is finally stabilized is as follows: No = (F * Kff−ΔG) * Kn = F * Kff * Kn−ΔG * Kn = F * γ− ΔG * Kn, and as shown in FIG.
It was lower than Kn. Here, γ is the ratio of the fan rotation speed N to the combustion amount F that does not cause incomplete combustion or lowering of the combustion efficiency, and F * γ is an appropriate rotation speed for the combustion amount F obtained by γ.

[0005] Therefore, there is a case where the amount of air becomes insufficient with respect to the combustion amount F, the combustion flame becomes smaller than normal, and incomplete combustion or reduction in combustion efficiency may occur. Further, the flame may flow back into the burner, and the burner may be melted.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems of the prior art, and has as its object to cope with incomplete combustion and reduced combustion efficiency by responding to gas types and pressure fluctuations. It is an object of the present invention to provide a water heater control device capable of maintaining a hot water temperature at a set temperature without causing the hot water.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a fuel operation unit for calculating a fuel supply amount based on a set temperature, a supply water temperature and a hot water supply amount, and a control deviation between the set temperature and the hot water supply temperature. A first correction unit that corrects the fuel supply amount to calculate a first fuel correction amount based on the first fuel correction amount, a fuel adjustment unit that controls a fuel control valve based on the first fuel correction amount, and a correction gain stored in advance. A second correction unit that corrects the first fuel correction amount based on the second fuel correction amount to calculate a second fuel correction amount, an air flow adjustment unit that adjusts a flow amount required for combustion based on the second fuel correction amount, A correction rate calculating unit that calculates a ratio of the fuel supply amount to the first fuel correction amount; and a correction gain updating unit that stores the ratio as the correction gain.

The correction gain updating section stores the ratio as the correction gain when the ratio is kept constant for a predetermined time. Further, the first correction unit includes an integral calculation unit and an integral value limiting unit, and the correction gain update unit keeps the ratio constant when a predetermined time has elapsed while the control deviation between the set temperature and the hot water supply temperature is zero. It is determined that it has continued for a predetermined time.

[0009]

In the case where the gas actually used has a higher calorific value or a higher gas pressure than the standard gas, the combustion ratio and the air volume are kept at an optimum ratio in advance. In addition, the amount of air does not become excessive even in the case of a gas having a small calorific value or a low gas pressure.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram of a control device for a water heater according to the present invention, FIG. 2 is a flowchart showing the operation of a correction gain updating unit 10, FIG. 3 is a block diagram of a PID calculation unit 25, and FIG. It is a block diagram showing another example.

As shown in FIG. 1, the control device of the gas water heater includes a fuel calculation unit 1 for calculating a fuel (gas) supply amount G based on a temperature difference between a set temperature Ts and a water supply temperature Tc, a water supply amount Q and the like.
A first correction unit 2 that corrects the fuel supply amount G based on the control deviation ΔTe between the set temperature Ts and the hot water supply temperature Th to calculate a first fuel correction amount Go; A second fuel correction amount βe * Go is calculated by correcting the first fuel correction amount Go based on the fuel adjustment unit 4 for controlling the control valve 3 and the correction gain βe stored in the correction gain output unit 5 in advance. 2 correction unit 6 and an air volume (fan) for adjusting the rotation speed of a combustion air supply fan 7 for supplying an air volume required for combustion based on a coefficient Kn (rotation speed / gas amount) and a second fuel correction amount βe * Go. A rotational speed) adjusting unit 8, a correction rate calculating unit 9 for calculating a ratio G / Go between the fuel supply amount G and the first fuel correction amount Go,
Corrected gain output unit 5 using ratio G / Go as corrected gain βe
And a correction gain updating unit 10 for storing the correction gain.

Reference numeral 11 denotes a heat exchanger, 12 denotes a gas burner, 13 denotes a feed water temperature sensor for detecting a feed water temperature Tc, 1
4 is a hot water supply temperature sensor for detecting the hot water supply temperature Th, 15 is a flow rate sensor for detecting the hot water supply amount Q, and 16 is a rotation speed / gas amount characteristic storage unit for storing a coefficient Kn.

The fuel calculating section 1 comprises a combustion amount calculating section 20 and a gas amount calculating section 21. The gas amount calculating section 21 has a coefficient Kff () via a gas group switching section 22 and a gas amount / burning amount characteristic storing section 23. Gas amount / combustion amount) is input. Therefore, the combustion amount F is calculated by the combustion amount calculation unit 20 based on the temperature difference between the set temperature Ts and the feedwater temperature Tc and the hot water supply amount Q, and the combustion amount F is further multiplied by the coefficient Kff by the gas amount calculation unit 21 to obtain the fuel. The (gas) supply amount G (Kff * F) is calculated.

The coefficient Kff is a value set by measuring a test gas at the time of shipment. Further, the coefficient Kff according to the gas type can be output by the gas group switching unit 22. However, even if the same gas group has a different combustion calorific value or a different gas pressure at the time of installation, a difference in combustion efficiency appears, so that the present invention is not applied. Control device is required.

The first correction unit 2 includes a PID (proportional + integral + derivative) calculating unit 25 and an adding unit 26. Further, as shown in FIG.
s and a hot water supply temperature Th, a proportional operation unit 27 that outputs a signal proportional to an input that is a control deviation ΔTe, an integration operation unit 28 that outputs a signal obtained by integrating an input that is a control deviation ΔTe, and an input that is a control deviation ΔTe. A differential operation unit 29 that outputs a signal obtained by differentiating the above, an addition unit 30 that outputs a value obtained by adding the outputs of the operation units 27, 28, and 29, and a limiter unit 31 that limits the value of the output signal. The gain is multiplied by the gain Kfb.

The limiter 31 is provided so as not to perform over-integration when the control deviation ΔTe between the hot water supply temperature Th and the set temperature Ts continues. Is exceeded, the output value is limited to the limiter value.

The correction gain updating section 10 stores the ratio G / Go as the correction gain βe in the correction gain output section 5 when the ratio G / Go continues for a predetermined time while the ratio G / Go is constant. Also, the control deviation ΔTe between the set temperature Ts and the hot water supply temperature Th
When the predetermined time has elapsed while the value of the ratio G / Go remains zero, the correction gain update unit 10 may determine that the ratio G / Go has continued for a predetermined time while being constant.

The operation of the control device for a water heater according to the present invention having the above configuration will be described. First, the fuel calculation unit 1 determines the fuel supply amount G based on the temperature difference between the set temperature Ts and the feed water temperature Tc, the hot water supply amount Q, and the coefficient Kff according to the gas group.

Further, the first correction unit 2 adds the output of the PID calculation unit 25 to the fuel supply amount G determined by the fuel calculation unit 1 with the control deviation ΔTe between the set temperature Ts and the hot water supply temperature Th as an addition unit 26. Is output as the first fuel correction amount Go. Then, the first fuel correction amount Go is input to the fuel control unit 4 to drive the fuel control valve 3.

In the second correction unit 6, the fuel supply amount G
The second fuel correction amount βe * G is obtained by multiplying the ratio G / Go of the first fuel correction amount Go and the first fuel correction amount Go as the correction gain βe.
o is obtained and input to the fan rotation speed adjusting unit 8.

Next, the operation of the correction gain updating unit 10 will be described with reference to the flowchart shown in FIG. First,
After the power is turned on, the correction gain output unit 5 outputs the initial value βe = 1 (S1). Next, it is determined whether or not combustion is in progress (S
2) If it is determined that combustion is taking place, it is further determined whether or not the set temperature Ts matches the hot water supply temperature Th (S3). On the other hand, if it is determined that combustion is not taking place, a predetermined time (for example, 20
(Seconds) is initially activated (S4).

In step S3, if it is determined that the set temperature Ts and the hot water supply temperature Th match, then it is determined whether or not the timer has expired (S5), and the set temperature Ts and the hot water supply temperature Th are equal to one another. If not, the timer is started initially (S4). In step S5, if it is determined that the timer has expired, the correction gain output unit 5 further stores the ratio G / Go between the fuel supply amount G and the first fuel correction amount Go as the correction gain βe (S6). If the timer has not expired, the process returns to step S2.

FIG. 4 shows another embodiment of the first correction unit 2, in which the reciprocal 1 / G of the fuel supply amount G, the set temperature Ts, and the hot water supply temperature Th are input to the PID calculation unit 30 and the output thereof is output. The coefficient 1 is added, and the calculation result is multiplied by the fuel supply amount G to obtain the first
This is the fuel correction amount Go. FIG. 4 shows the first correction unit 2
When the fuel supply amount G increases and βe * Go sharply increases, the output of the PID calculator 25 immediately increases, and the value of the first fuel correction amount Go immediately increases. Since it changes, the ratio G / Go can be treated as the correction gain βe.

[0024]

As described above, according to the present invention, the combustion amount and the air amount are kept at an optimum ratio in advance even when the combustion calorific value of the gas actually used is large or the gas pressure is higher than the standard gas. Therefore, it is possible to prevent incomplete combustion and a decrease in combustion efficiency due to an insufficient amount of air. Further, even when the calorific value of combustion of the gas is small or the gas pressure is low, it is possible to prevent the combustion flame from blowing out due to an excessive amount of air.

When a predetermined time has elapsed while the ratio of the fuel supply amount to the first fuel correction amount remains constant, this ratio is stored as a correction gain, so that the correction gain is not frequently updated. Therefore, stable combustion can be realized without a frequent change in the ratio between the gas amount and the air amount.

Further, when a predetermined time has elapsed while the deviation between the set temperature and the hot water supply temperature is zero, the ratio of the fuel supply amount to the first fuel correction amount is stored as a correction gain, and this ratio is multiplied by the first fuel correction amount. As a result, the second fuel correction amount is calculated without calculating the ratio of the fuel supply amount to the integral-limited first fuel correction amount as the correction gain.

[Brief description of the drawings]

FIG. 1 is a block diagram of a control device for a water heater according to the present invention.

FIG. 2 is a flowchart showing the operation of a correction gain update unit;

FIG. 3 is a block diagram of a PID operation unit.

FIG. 4 is a block diagram showing another embodiment of the first correction unit.

FIG. 5 is a characteristic diagram showing a temporal change of a gas supply amount G with respect to a required gas amount (F * Kff) in the related art.

FIG. 6 shows an appropriate fan speed (F *) in the prior art.
FIG. 6 is a characteristic diagram showing a temporal change of the fan rotation speed N with respect to γ)

[Description of Signs] 1 ... Fuel operation unit, 2 ... First correction unit, 3 ... Fuel control valve, 4
... Fuel adjustment unit, 5 ... Correction gain output unit, 6 ... Second modification unit, 7 ... Combustion air supply fan, 8 ... Air volume (fan rotation speed) adjustment unit, 9 ... Correction rate calculation unit, 10 ... Correction gain update Part, 11 heat exchanger, 12 gas burner, 13 supply water temperature sensor, 14 hot water supply temperature sensor, 15 flow rate sensor,
16: rotational speed / gas amount characteristic storage unit, 28: integral calculation unit,
31: limiter section (integral value limiting section), Ts: set temperature,
Th: Hot water supply temperature, ΔTe: Control deviation, Tc: Water supply temperature, Q
... Hot water supply amount, G ... Fuel supply amount, Go ... First fuel correction amount, βe
... Correction gain, Kn ... Coefficient (rotation speed / gas amount).

Continuation of the front page (56) References JP-A-1-150742 (JP, A) JP-A-62-2616 (JP, A) JP-A-60-235913 (JP, A) JP-A-62-19641 (JP, A) , A) (58) Field surveyed (Int. Cl. ⁷ , DB name) F23N 1/10 101 F24H 1/10 302 F24H 9/20

Claims (3)

(57) [Claims] A fuel calculation unit for calculating a fuel supply amount based on a set temperature, a supply water temperature, and a hot water supply amount; and a first fuel supply amount correcting unit for correcting the fuel supply amount based on a control deviation between the set temperature and the hot water supply temperature.
A first correction unit that calculates a fuel correction amount, a fuel adjustment unit that controls a fuel control valve based on the first fuel correction amount, and corrects the first fuel correction amount based on a correction gain stored in advance. A second correction unit that calculates a second fuel correction amount by using the second fuel correction amount, an air flow amount adjustment unit that adjusts a flow amount required for combustion based on the second fuel correction amount, and a ratio of the fuel supply amount to the first fuel correction amount. And a correction gain updating unit that stores the ratio as the correction gain. 2. The control device for a water heater according to claim 1, wherein the correction gain updating unit stores the ratio as the correction gain when the ratio is kept constant for a predetermined time. 3. The first correction unit includes an integral calculation unit and an integral value limiting unit, and the correction gain update unit sets the ratio to a predetermined value when the control deviation between the set temperature and the hot water supply temperature is zero for a predetermined time. 3. The control device for a water heater according to claim 2, wherein it is determined that the predetermined time has been maintained for a predetermined time.