JPS61295458A - Combustion controller for hot water supplier - Google Patents

Abstract

PURPOSE:To prevent a supply hot water temperature from varying and also prevent uncomfortable feeling with respect to warm water from being imparted to the user by providing differentiation constant changeover means which changes over to substantially zero the differentiation constant of D action control means in proportional integration-differentiation (PID) control means when the deviation is less than a predetermined value. CONSTITUTION:In the combustion controller for a hot-water supplier, comprising target temperature setting means 17 with respect to the supply hot water temperature, supply hot water detection means 18, and PID control means 25 for computing the opening of the fuel control value 4 on the basis of the deviation between the target temperature signal from target temperature setting means 17 and the detected temperature signal from the supply hot water temperature detection means 18 and outputting the value current to the fuel control valve 4, differentiation constant in saud PID control means substantially to zero when the deviation is less than the predetermines value.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention includes a target temperature setting means for the hot water outlet temperature, a hot water outlet temperature detecting means, a target temperature signal from the target temperature setting means, and a target temperature signal from the hot water outlet temperature detecting means. The present invention relates to a combustion control device for a water heater including a PTD (proportional integral derivative) control means that calculates the opening degree of a fuel control valve based on a deviation from a detected temperature signal and outputs a valve drive current to the fuel control valve.

(Summary of the Invention) The present invention provides PID? when the deviation between the target temperature signal and the detected temperature signal is quite small. By switching the differential constant of the D (differential) operation control means in the IJI control means to virtually zero, unstable fluctuations in the outlet temperature are prevented even when the change in water volume is small with no change in the target temperature. At the same time, in order to save energy, and when the water amount change is more than a predetermined value, output > a ? This is to ensure responsiveness with a high degree of FA.

(Prior Art and its Problems) The operation of the conventional combustion control device for a water heater having the configuration described in the section (Field of the Invention) will be explained based on the flowchart of FIG.

In step 2, the target temperature TS is inputted into the target temperature setting means, in step 2 the detected temperature TN from the hot water temperature detection means is manually input, and in step 2 PID calculation is executed to set the PI.
Calculate D output M7. In step ■, the valve drive current for the fuel control valve is calculated based on the PID output output,
In step (2), the fuel control valve is driven by the valve drive current, and the valve opening degree is controlled so that the detected temperature TN becomes the target temperature TS.

The PID calculation is performed using the following equation.

M, l(χ')-Kp-e,.

+ Σ, ・ell +) (Il(e, l-6fl-1) −・----・
- In formula 111 (]), M is the manipulated variable for controlling the opening of the fuel control valve at sampling timing t7, that is, the PID output, and e is the deviation between the target temperature TS and the detected temperature TNn at timing 1. That is, e, "TSa TNfi"...
・""" (21.

Also, in the first term, .e7 is a proportional term, and K is a proportional constant. The second term Σ is 1·eゎ is an integral term, and K1 is an integral constant. K in the third term.

(e,,"+1-1) is a differential term, ea-1 is the temperature deviation at the timing [7-7, and Ko is a differential constant.

The differential term Mo = Ko (+!n em-+ ) is
This is to increase responsiveness to sudden changes.

For example, when the amount of water changes, the outlet temperature (detected temperature T
N) will be stabilized promptly.

From formula (2), en−+ −TS, l−+ −TNa−+ −・
=--(3+Therefore, M6 =Ko (el16a-1) =Ko (TSRTS,-+) + Kn (T Na-+ T N, l) ・・
・・・・・・・・・・・・(4)

There is no change in target temperature TS, TSnxTS, l-.

In the case of Ma −Kn (TNll−+ TN−) ・・
・・・・・・・・・・・・(5)

In the case where the target temperature TS is not changed, as shown in Fig. 8, as a result of the increase in water volume, the outlet temperature (detected temperature TN
) decreases (TN, l-+>TN, ), the differential term MD increases according to equation (5).

As a result, the opening degree of the fuel control valve increases, the tapping temperature rises, and the differential term MD gradually decreases.

The hot water temperature rises to the original hot water temperature, and T N, =
When T N,l-r and the tapping temperature becomes stable, the differential term M0 becomes zero.

In order to have high responsiveness, the differential constant K.

It is necessary to set it large. The more the amount of water changes
jlLI:! When only one person is working, this high responsiveness results in good hot water temperature rise characteristics.

However, the conventional example having such a configuration has the following problems.

That is, even when the change in water volume is small without any change in the target temperature, the differential term MIl acts in accordance with the amount of variation in outlet temperature corresponding to the change in water volume. Small changes in the amount of water are constantly occurring, for example, due to subtle changes in the amount of hot water used within one's home or in the amount of hot water used by neighboring households.

As shown in Fig. 9, in a state where such small water volume changes are constantly occurring, the hot water temperature also changes slightly, so the differential term M0 also acts frequently, and as a result, the hot water temperature constantly fluctuates. A situation may occur in which the temperature is not stabilized.

If hot water is used in such a state, the function of the hot water itself will become unstable.

Particularly, when using a shower, there is a problem of great discomfort. Furthermore, since the burner output is adjusted by carefully driving the fuel control valve, there is a problem in that energy consumption is wasted.

In order to avoid this problem, it is sufficient to set the differential constant to a small value, but if this is done, there is a fundamental problem that the responsiveness of the hot water temperature will deteriorate.

(Object of the Invention) The present invention has been made in view of the above circumstances, and is capable of preventing unstable fluctuations in the temperature of hot water even when minute changes in water volume are constantly occurring. The purpose is to ensure high responsiveness of the hot water temperature when the water amount change is greater than a predetermined value, so as not to cause discomfort to users of hot water, and to save energy.

(Configuration and Effects of the Invention) In order to achieve the above object, the present invention has the following configuration.

That is, the combustion control device for a water heater of the present invention, as shown in FIG.
l! ,! I! 3-l % peak means 18 calculates the opening degree of the fuel control valve 4 based on the deviation between the target temperature signal from the target temperature setting means 17 and the detected temperature signal from the hot water temperature detection means 18, and calculates the opening degree of the fuel control valve 4. In the combustion control device for a water heater, which includes a PID control means 25 that outputs a valve-driving Ti flow to the control valve 4, when the deviation is less than or equal to a predetermined value, fi? The differential constant switching means 27 is provided for switching the differential constant of the D operation control means 24 in the i-th PID control means 25 to substantially zero.

The effects of this configuration are as follows (see Figure 6)
.

In a state where minute changes are constantly occurring in the water, the temperature of the hot water also varies slightly, resulting in a deviation between the target temperature signal and the detected temperature signal.

However, since the deviation is less than the predetermined value, the differential constant switching means 27 switches the differential constant to substantially zero. Therefore, the differential term Mn does not act, and as a result, unstable fluctuations in the tapping temperature are prevented and a stable state is maintained. In addition, energy savings can be achieved by preventing unstable fluctuations in the temperature of the hot water.

From the above, it is not necessary to set the differential constant to a small value, and it is possible to set it to a large value.

When there is a relatively large change in the amount of water and the deviation between the target temperature signal and the detected temperature signal exceeds a predetermined value, a differential term M0 having a value of 0 acts on the differential constant set to a large value, and the fuel control valve 4 The valve opening degree is controlled. Therefore, fluctuations in the tapping temperature caused by changes in water amount can be suppressed within a short time.

That is, responsiveness is maintained in a high state and the rising characteristic of the tapping temperature is made good.

As described above, according to the present invention, even in a state where minute changes in the amount of water constantly occur, unstable fluctuations in the tapping temperature can be prevented, and when the change in the amount of water is equal to or greater than a predetermined value, It is possible to ensure high responsiveness of the hot water temperature so as not to cause discomfort to users of hot water, and it is also effective in saving energy by preventing unstable fluctuations in the hot water temperature. be done.

(Description of Examples) Hereinafter, the present invention will be described in detail based on examples shown in the drawings.

Figure 2 is a professional circuit diagram of a water heater to which the present invention is applied;
FIG. 3 is a block diagram of a combustion control device for a water heater according to an embodiment of the present invention.

In FIG. 2, 1 is a burner, 2 is a fuel supply path connected to the burner 1, and the fuel supply path 2 includes a solenoid valve (main valve) 3 that controls fuel supply to the burner 1 and a fuel control valve (
A proportional valve) 4 is installed. A spark plug 5 and a flame loft 6 are arranged near the burner 1.

A combustion chamber 7 is provided above the burner 1, and a fan motor 8 is provided in an exhaust path communicating with the combustion chamber 7. The fan motor 8 controls exhaust gas and also supplies combustion air to the burner 1 .

Reference numeral 9 denotes a heat exchanger constructed by winding a water supply pipe around the combustion chamber 7, and this heat exchanger 9 is connected to a plurality of hot water outlets 10 such as a boiler or a shower.

11 is a stabilizing power supply circuit, 12 is a drive circuit for the solenoid valve 3, 1
3 is a control circuit for the fan motor 8, 14 is a drive circuit for the spark plug 5, 15 is a flame detection circuit connected to the flame rod 6, and 16 is a combustion control device for a water heater according to an embodiment of the present invention.

The configuration of this combustion control device 16 will be explained based on FIG. 3.

In FIG. 3, 17 is a target temperature setting means for the hot water outlet temperature, 18 is a hot water outlet temperature detection means, and 19 is a proportional constant of 1.
．． 1 for the constant of integration and K for the differential constant.

ROM (read only memory) that stores 20
is the deviation e11 between the target temperature signal from the target temperature setting means 17 and the detected temperature signal a from the hot water temperature detection means 18.
21 is a valve drive current calculation means that calculates the valve drive current value iw of the fuel control valve 4 based on the PID output M7.

The PID calculation processing means 20 is a P (proportional) operation control means 2.
2.1 (integral) operation control means 23 and D (m minute) operation control means 24, which store the proportionality constant Kp and the integral constant 9.1 from the ROM 19 based on the deviation e7, respectively. 0 is read as the differential constant, and the proportional term, integral term, and differential term shown in equation (1) are calculated. PID calculation processing means 2
0 sums these up and calculates the PID output M7.

These ROM19. The PID calculation processing means 20 and the valve drive current calculation means 21 constitute the PID control means 25 referred to in the configuration of the invention.

26 is the valve drive current value i from the valve drive current calculation means 21
This is a fuel control valve drive means that drives the fuel control valve 4 based on the valve drive current value iv to the valve opening degree corresponding to the valve drive current value iv.

27 inputs the deviation e7, compares the value with a predetermined value Th, and when it is less than the predetermined value Th, outputs the D operation prohibition signal.
This is a differential constant switching means for switching the differential constant KD of the D operation control means 24 to substantially zero by outputting the signal to the operation control means 24 and prohibiting the operation of the D operation control means 24.

For example, as shown in FIG. 4, when the absolute value of the deviation e7 between the target temperature and the detected temperature is less than or equal to the predetermined value Th, Ko
-0, and when the predetermined value Th is exceeded, the differential constant is set to, for example, KD-10.

The operation of this combustion control device will be explained below based on the flowchart shown in FIG.

In step ■, the target temperature setting means 17 sets the target temperature T.
S is input, the detected temperature TN from the outlet hot water temperature detection means 18 is inputted in step (2), and the deviation e7 between the target temperature TS and the detected temperature TN is calculated in step (2). In step (2), it is determined whether the absolute value of the deviation e1 is less than or equal to a predetermined value Th.

If the determination in step (2) is YES, that is, if minute changes in the amount of water are constantly occurring as shown in the first half of FIG. 6, the following flow is executed. That is, the process moves to step (2), and the proportional constant is set to 1 from the ROM 19. At the same time as reading 1 into the integral constant, the differential constant Ko is set to K,=0, and the PID calculation based on the above-mentioned 2(1) is executed to calculate the PID output M7. Since Ko=0, the arithmetic expression in this case is M, (χ)=Kp'fl.

+ 1 to Σ ・ell ・・・・・・・・・・・・
・It becomes (6). In step ■, the valve drive current iv for the fuel control valve 4 is calculated based on the PID output M7 calculated in step ■, and in step ■, the valve drive current i
The fuel control valve 4 is driven by v, and the valve opening degree is controlled so that the detected temperature TN becomes the target temperature TS.

As described above, when the absolute value of the deviation e1 is less than or equal to the predetermined value Th, the differential term M. As a result, unstable fluctuations in the tapped water temperature can be prevented and a stable state can be maintained. In addition, energy savings can be achieved by preventing unstable fluctuations in the temperature of the hot water.

Therefore, the differential constant can also be set to a large value.

If the determination in step (2) is No, that is, as shown in the second half of FIG. 6, there has been a relatively large change in water volume and the deviation 87 between the target temperature signal and the detected temperature signal has exceeded the predetermined value Th. In this case, execute the following flow. That is, proceed to step (2), and from ROM+9, change the proportionality constant to 6. Read out 0 for the integral constant Kl and the m-minute constant, and use the above formula fi+
, Mll (χ) = Kp ”3n + Σ, ・el + Ko (em −e A-1) −−−
...(Execute the normal PID calculation based on 11 to calculate P
Calculate the ID output M. In step■, step■
Calculate the valve drive current iv for the fuel control valve 4 based on the PID output M, calculated in step (2), drive the fuel control valve 4 with the valve drive current i, and detect the valve opening degree. Control is performed so that the temperature TN becomes the target temperature TS.

As described above, when the deviation 87 exceeds the predetermined value Th, the differential term M0 with the differential constant KD set to a large value
acts, and the valve opening degree of the fuel control valve 4 is controlled. Therefore, fluctuations in the tapping temperature caused by changes in water amount can be suppressed within a short time. That is, responsiveness can be maintained in a high state and the rising characteristics of the tapping temperature can be improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention, FIGS. 2 to 6 relate to a combustion control device for a water heater according to an embodiment of the present invention, and FIG. 2 is a block diagram of a water heater to which the present invention is applied. figure,
Fig. 3 is a block diagram of a combustion control device for a water heater according to an embodiment of the present invention, Fig. 4 is an explanatory diagram of differential constant switching, Fig. 5 is a flowchart, Fig. 6 is a time chart, and Figs. Figure 9 relates to a conventional example, Figure 7 is a flowchart,
FIGS. 8 and 9 are time charts. 4... Fuel control valve 17... Target temperature setting means 18... Hot water temperature detection means 24... D operation control means 25... PID control means 27... Differential constant switching means

Claims (1)

[Claims] (1) A target temperature setting means for the hot water outlet temperature, a hot water outlet temperature detecting means, and a fuel control valve control based on the deviation between the target temperature signal from the target temperature setting means and the detected temperature signal from the hot water outlet temperature detecting means. In a combustion control device for a water heater, comprising a PID control means for calculating an opening degree and outputting a valve driving current to the fuel control valve, when the deviation is less than or equal to a predetermined value, the D operation control means in the PID control means is activated. A combustion control device for a water heater equipped with a differential constant switching means for switching a differential constant to substantially zero.