JP3103674B2 - Hot water supply temperature 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 hot water supply temperature control device for a water heater by feedback control.

[0002]

2. Description of the Related Art There has been known a water heater in which a microcomputer is mounted on an appliance and the opening of a gas proportional valve to a combustion burner, that is, a proportional valve current value is controlled by controlling the microcomputer. In addition, feedback control by a microcomputer is widely used for controlling the tapping temperature. That is, the temperature of the hot water from the heat exchanger provided in the water heater is detected, and a feedback control by the microcomputer is performed by comparing the detection signal with a set temperature signal from the hot water temperature control volume, thereby controlling the gas to the combustion burner. The purpose is to control the opening degree (gas amount) of the proportional valve, that is, the proportional valve current value.

[0003]

However, in the conventional feedback control, the constant used in the feedback calculation expression is set to a constant and unchangeable value, that is, feedback calculation is performed using a fixed constant, and based on the calculation result, This was to determine and control the proportional valve current value to the gas proportional valve.

[0004] The conventional feedback control equation is given by
It is shown in the following.

[0005]

(Equation 1)

[0006] According to the conventional feedback control equation shown in Equation 1, the feedback amount (INPFB) has a constant value in a constant temperature change state. FIG. 4 shows a change state of the input amount (the current input amount INPn, the previous input amount INPn-1) based on the current feedback control formula.

In this figure, for example, if the input amount is
Temperature change is constant between 10,000 Kcal / h and 20,000 Kcal / h, and the feedback amount (INPFB) is 5,000 Kca
1 / h, when the input amount is 10,000 Kcal / h, the feedback amount (INPFB) is 5,000
/ 10,000 x 100 = 50% change, 20,000 Kcal
/ H input amount, the feedback amount (I
NPFB) changes by 5,000 / 20,000 × 100 = 25%. That is, when the input amount is low, the rate of change of the input amount is large, which is the same as the gain of the feedback constant, and the tapping temperature is easily hunted.

On the other hand, when the input amount is high, the rate of change of the input amount is small, which is the same as the decrease in the gain of the feedback constant, and the time until the temperature reaches the set temperature becomes longer, resulting in poor response. Becomes

Therefore, when a high feedback constant is determined, hunting of the tapping temperature occurs when the water supply amount (flow rate) is low, and when a low feedback constant is determined, it takes time to adjust the temperature until the tapping temperature reaches the high flow rate. There was a problem that response was poor.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has as its object to solve the problem when the proportional valve current value to the gas proportional valve for adjusting the gas amount to the combustion burner is high. It is an object of the present invention to provide a hot water supply temperature control device for a water heater that can obtain the same effect as setting the feedback constant high and setting the feedback constant low when the proportional valve current value is low. This prevents hunting of the tapping temperature, shortens the time required to reach the tapping temperature, and enhances the responsiveness of the tapping temperature adjustment.

[0011]

In order to achieve the above object, a hot water supply temperature control device for a water heater according to the present invention comprises a hot water temperature detecting means for detecting a hot water temperature from a heat exchanger, and a hot water setting means for setting the hot water temperature. Temperature setting means, a tapping temperature signal from the hot water temperature detecting means and a setting temperature signal from the hot water setting means are inputted, and the gas proportional valve to the combustion burner is controlled by feedback control so that the tapping temperature becomes the setting temperature. A water heater provided with a burner control means for controlling an opening degree, wherein the burner control means corrects the input amount based on a feedback signal from the gas proportional valve so that the input amount becomes larger as the previous input amount increases. There is provided feedback calculation means for calculating the current input amount by performing an addition operation with a feedback amount having a coefficient.

The correction coefficient of the feedback amount at this time may be a value associated with the previous input amount with respect to the maximum opening of the gas proportional valve (ie, the maximum proportional valve current value), or the maximum hot water temperature with respect to the hot water set temperature. It may be a value associated with the set temperature. It is also possible to make the two values synergistically related.

[0013]

According to the water heater of the present invention having the above structure,
When the tapping temperature signal from the hot water temperature detecting means and the set temperature signal from the hot water setting means are input to the burner control means, the feedback calculating means calculates the present input quantity from the previous input quantity and the feedback quantity of the combustion burner. However, at this time, when the input amount is low, the correction coefficient applied to the feedback amount is a small value, and when the input amount is high, the correction coefficient is a large value. When the input amount of the valve is low, the opening degree, that is, the change amount of the proportional valve current value is small, and when the input amount is high, the opening degree, that is, the change amount of the proportional valve current value is large. Therefore, when the input amount is low, hunting of the tapping temperature is avoided, and when the input amount is high, the tapping temperature is quickly reached.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a water heater to which a tapping temperature control device according to the present invention is applied. As shown in the figure, the water heater 10 is provided with a water governor 16 and a water flow detection switch 18 in a water supply pipe 14 leading to a heat exchanger 12. The tapping pipe 20 on the tapping side of the heat exchanger 12 is provided with a tapping thermistor 22 for detecting the temperature of tapping water flowing through the tapping pipe 20. Then, by opening the faucet 24 provided at the tap of the tapping pipe 20, the water governor 1 is opened.
6 is opened so that water flows into the water supply pipe 14 and the flowing water is detected by the water flow detection switch 18.

The ON signal from the water flow detection switch 18 and the detection signal of the tapping temperature by the tapping thermistor 22 are as follows:
It is transmitted to the burner controller 26. The water heater 10 is provided with a hot water temperature adjusting volume 28 for adjusting the hot water temperature, and a hot water temperature setting signal by the hot water temperature adjusting volume 28 is also transmitted to the burner controller 26.

On the other hand, the combustion burner 30 for heating the heat exchanger 12 is provided with a gas proportional valve 34 in a gas pipe 32 for supplying a fuel gas. Combustion air is also sent to the combustion burner 30. Gas proportional valve 34
, Ie, the proportional valve current value is adjusted based on a signal from the burner controller 26.

The burner controller 26 compares the hot water temperature setting signal transmitted from the hot water temperature adjusting volume 28 with the hot water temperature signal transmitted from the hot water thermistor 22 as described above. The feedback control is performed based on a feedback control formula described later in consideration of the output value.

In the water heater having such a configuration, in the present invention, Expression 2 is set in the control unit of the burner controller 26 as a feedback control type.

[0019]

(Equation 2)

Here, INPn: input amount output this time INPn-1: input amount output last time INPmax: input amount when the proportional valve current value is maximum INPFB: feedback amount calculated this time A, B: coefficient (A> 0, B ≧ 0)

Thus, according to the feedback control equation of the present invention, the correction coefficient (A) of the feedback amount (INPFB)
× INPn-1 + B) / INPmax, so the feedback amount (INPF
The rate of change in B) can be reduced, which is equivalent to a decrease in the gain of the feedback constant, and a state in which hunting of the tapping temperature is unlikely to occur can be obtained. Also, when the input amount is high, the rate of change of the feedback amount (INPFB) can be increased, which is the same as the increase in the gain of the feedback constant, and the time required to reach the set temperature is shortened. Control will be fulfilled.

On the other hand, the rise of the tapping temperature greatly changes depending on the set temperature. Therefore, it is also effective to perform the correction based on the set temperature. This is because the gas flow rate changes depending on the set temperature even if the output amount of the combustion burner 30 is the same. When the gas flow rate is small, the feedback amount (I
NPFB) has a large effect, so it is desirable to correct this.

Equation 3 is expressed by Equation 2 as a feedback control equation.
The correction coefficient for the set temperature is inserted in the control formula shown in FIG.

[0024]

(Equation 3)

Here, Nmax: set maximum temperature N ': correction set temperature 15: average water temperature

The correction set temperature can be expressed by the following equation (4).

[0027]

(Equation 4)

Where C and D are coefficients

According to the feedback control equations shown in Equations 3 and 4, the input amount is an equation related to the set temperature. If the tapping temperature is controlled according to this control equation, the hunting phenomenon of the tapping temperature is eliminated, and It can be expected that the responsiveness of temperature control will also be improved.

That is, in the feedback control formula of Equation 3, when the set temperature is high (this corresponds to the case where the flow rate of water is small), the feedback amount (IN
(PFB) correction coefficient (Nmax-15) / (N'-1)
This is the same as the case where the value of 5) is reduced and the gain of the feedback constant is reduced, and hunting of the tapping temperature can be avoided. When the set temperature is low (this corresponds to a high flow rate of water), the correction coefficient of the feedback amount (INPFB) is (Nmax-15) / (Nmax).
As the value of '-15) increases and the gain of the feedback constant increases, the set temperature can be reached in a short time.

FIG. 2 shows a change state of the input amount (INPn) based on the feedback control equation in which the correction coefficient of the set temperature shown in Expression 3 is inserted. This diagram shows the condition when the coefficients A and C are both 1 and the coefficients B and D are both 0 (A = 1, B = 0, C = 1, D = 0). As shown in this figure, the feedback amount (INFBB) gradually increases with the input amount at both the maximum temperature setting and the minimum temperature setting.
When the input amount at the maximum temperature setting and the input amount at the minimum temperature setting are both lower than the change by the current feedback control formula (constant feedback amount), the gain of the feedback constant is the same as the decrease in the gain of the feedback constant. Hunting of the tapping temperature is unlikely to occur, and when the input amount is high, it is the same as increasing the gain of the feedback constant, and a state of good responsiveness in tapping temperature adjustment can be obtained.

FIG. 3 shows the relationship between the current set temperature (N) and the corrected set temperature (N '). In FIG. 2 described above, the coefficient C = 1 and the coefficient D = 0, and the corrected set temperature N ′ = current set temperature N has been described, but as shown in FIG. It is needless to say that if the measurement is made and this correction formula is applied (introduced) to the above-mentioned feedback control formula shown in the above equation (3), it is possible to obtain a control in which the hunting phenomenon of the tapping temperature does not occur and the tapping temperature adjustment response is good. No.

[0033]

As is clear from the above description, according to the water heater of the present invention, when adjusting the tapping temperature by feedback control, the feedback coefficient is set to a small value when the input amount is low and the feedback calculation is made small. Is performed to control the proportional valve current value corresponding to the opening (gas amount) of the gas proportional valve of the combustion burner. Therefore, when the input amount is low, the hunting phenomenon of the tapping temperature can be avoided, and the high input amount can be avoided. In this case, since the feedback calculation is performed by setting the correction coefficient of the feedback amount to a large value, the time until the tapping temperature reaches the set temperature can be reduced, and the tapping temperature control with good responsiveness can be achieved. It is.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a water heater according to one embodiment of the present invention.

FIG. 2 is a diagram illustrating a change state of an input amount in the case of the feedback control of the present invention in the water heater shown in FIG.

FIG. 3 is a diagram illustrating a correction function when correcting a set temperature in feedback control in FIG. 2;

FIG. 4 is a diagram illustrating a change state of an input amount in a conventional (current) feedback control.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Water heater 12 Heat exchanger 22 Hot water thermistor 26 Burner controller 28 Hot water temperature adjustment volume 30 Combustion burner 34 Gas proportional valve

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F24H 1/10 302 F23N 5/02 350

Claims (1)

(57) [Claims] 1. A hot water temperature detecting means for detecting a hot water temperature from a heat exchanger, a hot water setting means for setting a hot water temperature, a hot water temperature signal from the hot water detecting means and a setting from the hot water setting means. A water signal that inputs a temperature signal and controls the opening of a gas proportional valve of a combustion burner by feedback control so that the outlet temperature becomes a set temperature.The burner control means includes: A feedback calculating means for calculating a current input amount by adding a previous input amount and a feedback amount having a correction coefficient that gradually increases as the input amount increases based on a feedback signal from the proportional valve; A tap water temperature control device characterized by the following.