JPS61295457A - Combustion control unit of hot water supplier - Google Patents

Abstract

PURPOSE:To prevent the temperature of supplied hot water from over-shooting and hunting even when the amount of water changes in a state where the target temperature does not change, and to secure a high response to the supply hot water temperature thereby to save energy by providing gain changeover means for increasing or decreasing a gain of proportional integration-differentiation (PID) means in accordance with the increase or decrease of the deviation. CONSTITUTION:Even in a state where the target temperature is not changed, when the amount of water is changed, it results in producing a deviation between a target temperature signal and a detected temperature signal. When the amount of water has increased, the detected temperature decreases and the deviation increases. Accordingly, the gain changeover means 27 increases the gain of the PID control means 25. The PID output having the gain thus increased evades the ovrshooting and hunting of the supply hot water temperature and further imparts a high response to the supply hot water temperature. Further, when the amount of water has decreased, the deviation also decreases. Accordingly, the gain changeover means 27 decreases the PID control means 25. In any case, since the response to the supply hot-water temperature is high, energy is saved.

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 PID (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 an increase in the deviation between a target temperature signal and a detected temperature signal.
By increasing or decreasing the gain of the PID control means in accordance with the change in temperature, overshoot and hunting in the hot water temperature can be prevented even if the water volume has changed without any change in the target temperature. This ensures high responsiveness to the hot water temperature and saves energy.

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

The PID calculation is performed using the following equation.

Mll (χ) - KP ・e- + Σ K , ・ ell 10 KB (e ar" + 1-1) ......
...In the fl1 formula fl+, M,1 is the manipulated variable for controlling the opening degree of the fuel control valve at sampling timing t7, that is, P[D output, and e7 is the deviation between the target temperature TS at timing t7, and the detected temperature TNfi. , that is, e a ” T Ss −T N, 1””'---
-----(I'm 21.

Also, in the first term, .e and l are proportional terms, and K is a proportional constant. In the second term Σ, 1·eR is an integral term, and K is an integral constant. KD in Section 3
ell-, ) is a differential term, and ell-1 is the timing t1
The temperature deviation in 1-1, Kl, is a differential constant.

In conventional water heater combustion control devices, the proportionality constant is 1
．． + for the integral constant and 0 for the differential constant are each fixed values.

When determining each of these constants, assuming that the heat capacity of the control system does not change, the optimal value of each constant is set to 1.
can be determined.

However, like a water heater, the target temperature TS can be adjusted (
For example, when the water volume changes (for example, from 30 to 93 degrees Celsius) or when the amount of water changes (for example, from 3.5 to 16 Il changes), the optimal values of proportionality constant KF, integral constant of 1, and differential constant of 8 cannot be fixed. do not have.

For example, as shown in Fig. 7 (A), when the amount of water is small, the proportionality constant Kp, the integral constant 1, and the differential constant are determined to be optimal values that will improve the rise characteristics of the tapping temperature. Suppose we did. In this case, the value of the PID output M1 is small and the gain of the PID control means is low.

If the amount of water increases without any change in the target temperature, it is equivalent to a deviation between the target temperature and the detected temperature, but since the gain is low, the hot water output will increase as shown in (B) in Figure 7. The temperature rise time becomes considerably longer. In other words, the responsiveness of the tapping temperature deteriorates.

Moreover, in contrast to the above, for example, as shown in FIG. 8(A), when the amount of water is large, the proportionality constant KF.

It is assumed that the integral constant KI and the differential constant are set to 0, which are optimal values that provide good rise characteristics of the tapping temperature. In this case, the value of the PID output M8 is large and the gain of the PIDIJ control means is high.

If the amount of water decreases without changing the target temperature, a deviation will occur, but since the gain is high, the hot water temperature will overshoot, and hunting will occur immediately after that, as shown in FIG. 8(B).

Since this overshoot and hunting are very undesirable, the gain of the PID control means is usually determined to be low. Therefore, the response when the amount of water increases is extremely poor.

The problem is that poor responsiveness to the hot water temperature can cause a lot of discomfort, especially when using a shower.

There is. Further, there is a problem in that energy consumption (burner output) is wasted.

(Object of the Invention) The present invention has been made in view of the above circumstances, and is intended to prevent overshoot and hunting in the outlet temperature even when the water amount changes without changing the target temperature. At the same time, the purpose is to ensure high responsiveness of the hot water temperature 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. PID control means 2 which calculates the opening degree of the fuel control valve 4 based on the deviation between the detected temperature signal from the outlet hot water temperature detection means 18 and outputs a valve drive current to the fuel control valve 4;
5, in the combustion control device for a water heater, the PID control means 2
It is equipped with a gain switching means 27 that increases or decreases the gain of 5 by 1.

The effects of this configuration are as follows.

Even if there is no change in the target temperature, if there is a change in the amount of water, a deviation will occur between the target temperature signal and the detected temperature signal.

When the amount of water increases, the detected temperature decreases and the deviation increases. Therefore, the gain switching means 27 increases the gain of the PID control means 25. The gain after the increase at this time is a gain of an optimum value commensurate with the amount of increase in water amount or a value close to the optimum value. The PAD output with the increased gain avoids overshoot and hunting in the tapped water temperature, and increases the responsiveness of the tapped hot water temperature.

Furthermore, when the amount of water decreases, the deviation also decreases. Therefore, the gain switching means 27 reduces the gain of the PID control means 25. The gain after the decrease at this time is a gain of an optimal value commensurate with the amount of water volume decrease or a value close to it. Again, the PID output with the reduced gain avoids overshoot and hunting in the outlet temperature and makes the outlet temperature more responsive.

In addition, in both cases, the responsiveness of the hot water temperature is high, so
Energy saving is achieved.

As described above, according to the present invention, even if the water volume changes without any change in the target temperature, by automatically switching to a gain commensurate with the amount of change in water volume, overshoot of the hot water temperature can be prevented. Hunting can be prevented, high responsiveness of tap water temperature can be ensured, and energy can be saved.

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

FIG. 2 is a block circuit diagram of a water heater to which the present invention is applied, and 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 radiator 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 is in charge of exhaust gas and also supplies combustion air to the burner l.

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 drain 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 water heater salt m control device 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 the target temperature setting means for the hot water temperature, 18 is the hot water temperature detection means, and +9 is the proportional constant K P I + integral constant when the gain is large.
2□ is the proportionality constant when the m-minute constant KD is set to a medium gain.
, 12. to the constant of integration. 0 for the differential constant, and proportional constant K F 3 + +3 for the integral constant when the gain is small.
．． It is a ROM (read only memory) that stores +13 in the differential constant.

20 is the deviation e 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.
PID calculation processing means for calculating the PID output M based on 7; 21 is the PID output M;

This is a valve drive current calculating means that calculates a valve drive current value i of the fuel control valve 4 based on the following.

The PID calculation processing means 20 is a P (proportional) operation control means 2.
2. r(integral) operation control means 23 and D Cm) operation control means 24, each of which inputs a proportional constant from the ROM 19 based on the deviation e7, any one of ~KP3, and an integral constant K1. Read out any one of K 1 s and any one of the differential constants K11l-KI13, and calculate the proportional term shown in 2fi+.

Calculate the integral term and differential term. The PID arithmetic processing means 20 adds up these and outputs a PIDID output sound 7.

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 driving means that drives the fuel control valve 4 based on the valve driving current value 1v to the valve opening degree corresponding to the valve driving current value 1v.

27 inputs the deviation e7 and sets the value to a predetermined value Th+
-Thz (Th+ > O > Th,) compared to
When e a >'l' h 1 , the ROM1
9 to the proportionality constant KFI+ when increasing the above gain
Command to read integral constant K + + + differential constant Kll+, T h z ≦e, l≦Th.

In this case, for the PID calculation processing means 20, the ROM1
9 to the proportionality constant when the gain is medium, and 1 to the integral constant! , command to read out the differential constant KDI, all<Th.

In this case, for the PID calculation processing means 20, the ROM1
9 to the proportionality constant K P when the above gain is made small
This is a gain switching means that instructs to read +s and a component constant K113 from 2+integral constant.

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 e between the target temperature TS and the detected temperature TN is calculated in step (2).

When the amount of water changes while the target temperature TS remains unchanged, a deviation ell occurs that is approximately proportional to the amount of change in the amount of water.

In step (■), the deviation e, , is set to a predetermined value Th.

Compare with Thz (Th+>O>'rh,).

ell>Th.

If so, proceed to step ① and store the proportional constant for increasing the gain described above from ROM19, the integral constant ++
, reads out the differential constant Kll+, executes a PID operation based on the above equation (1), and calculates the PID output M1. The calculation formula in this case is M n + = K r I
-e 11+ Σ, ・el + K11l(e a e n−+ ) −−
・=-f31. In this case, 1) the value of the ID output M11 is large (the gain of the PID control means 25 is high; in other words, it is the optimum gain commensurate with the increase in water volume, and overshoot and hunting of the outlet temperature are prevented; High responsiveness of the hot water temperature is ensured.

Also, based on the judgment in step ■, Th, ≦e, l≦Th.

In this case, proceed to step ■, and set the proportional constant Krz and #f1 constant for the case where the gain is medium from ROM19.
□, read out the differential constant, and use the formula, M*z=Kpt'
en + Σ to 1□・e7 + Koz (6a e n-+ ) +++++
PID output M7□ is calculated based on +++++f41. The value of PID output M *z in this case is medium, and P
The gain of the ID control means 25 is also medium. In this case, the gain is optimal according to the normal amount of water, preventing overshoot and hunting, and ensuring high responsiveness of the tapping temperature.

In addition, if all <Thg in the judgment at step (2), the process moves to step (2), and 3. +s1m to integral constant
Read 0 to the minute constant and use the formula, MnswK, 3-e.

+ Σ+s・e7 + Kos(e m −6m−1) −−−−f
PID output MB3 is calculated based on 5). PID output M7 in this case. The value of is small, and the PID control means 25
The gain is also small. In this case as well, the gain is optimal in proportion to the decrease in water volume, preventing overshoot and hunting, and ensuring high responsiveness of the tapping temperature.

After step ■, ■ or ■, in step ■, the valve drive current iVl+ for the fuel control valve 4 is determined based on the previously calculated PID output Mn, , M, □ or M, , 3.
f v! Alternatively, fv3 is calculated, and in step (2), the fuel control valve 4 is driven by the valve drive current I Vl+ l Vt or iv, and the valve opening degree is determined by the detected temperature T.
Control is performed so that N becomes the target temperature TS.

For example, as shown in FIG. 5, when the gain is selected to be moderate without changing the target temperature TS,
When the amount of water increases and the detected temperature TN decreases, the formula (2
), the deviation eR becomes positive, but when e,>Th, the gain G of the PID control means 25
The valve drive current is increased to widen the valve opening (and the input to burner 1 is increased to raise the hot water temperature. In other words, there is no overshoot or hunting, and high responsiveness is achieved. Combustion is controlled so that the detected temperature TN matches the target temperature TS.

Furthermore, when the target temperature TS is unchanged and the gain is selected to be moderate, when the water volume decreases and the detected temperature TN increases, the deviation ell becomes negative, but e, < Th , the gain G of the PID control means 25
The valve drive current is reduced to reduce the valve opening, thereby reducing the input to the burner 1 and lowering the hot water temperature. In this case as well, combustion is controlled so that the detected temperature TN matches the target temperature TS without overshoot or hunting and with high responsiveness.

The present invention also includes the following configuration as an example.

(1) The gain switching means 27 is connected to the P operation control means 22. in the PID control means 25. ■Operation control means 23 and D
It is configured to switch the gain of any one of the operation control means 24.

(■) The gain switching means 27 controls the P operation control means 22.1 operation control means 23 and D in the PID control means 25.
It is configured to switch the gains of any two of the operation control means 24.

(II[) The above examples and the above (I), (II)
In either case, the number of gain switching is two or four or more.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention, FIGS. 2 to 5 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 a flowchart, FIG. 5 is a time chart, FIGS. 6 to 8 are related to a conventional example, and FIG. is a flowchart, and FIGS. 7 and 8 are waveform diagrams for specifying problems. 4... Fuel control valve 17... Target temperature setting means 18... Hot water temperature detection means 22... P operation control means 23... I operation control means 24... D operation control means 25... - PID control means 27...gain switching means

Claims (2)

[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 the combustion control device for a water heater, the gain of the PID control means is increased in accordance with an increase or decrease in the deviation. , a combustion control device for a water heater equipped with gain switching means for decreasing and changing the gain. (2) The gain switching means is configured to switch the gain of at least one of the P operation control means, the I operation control means, and the D operation control means in the PID control means. The combustion control device for a water heater as described in (1).