JPH0271050A - Controller for hot water supplying apparatus - Google Patents

Abstract

PURPOSE:To suppress the fluctuating width of output hot water temperature immediately after hot water feeding is started by elimination the correction of a deviation amount between a set temperature and the fed hot water temperature by a feedback control to the vicinity of the output temperature to the set temperature immediately after the feeding of hot water is started. CONSTITUTION:Combustion quantity Q obtained by a controller 40 includes in combination a feed-forward control and a feedback control. The feed-forward control is obtained by adding a feed-forward amount FF, a heat exchanging amount correcting amount K, and air-fuel ratio correcting amount T, and the feedback control is obtained by adding a proportional correcting amount P and an integration correcting amount I. Immediately after the feeding of hot water is started, the values of the amounts P, I of the feedback control are set to '0' to the vicinity of output hot water temperature To to the set temperature Ts. That is, a deviation amount between the temperatures Ts and To is not corrected by the feedback control. Thus, if the deviation amount immediately after the feeding of hot water is started is large, the combustion quantity Q is determined only by the feed-forward control.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a water heater control device that corrects the amount of deviation between a set temperature and a hot water outlet temperature by feedback control.

[Prior art 1] Some water heaters control the amount of heating (for example, combustion input) by a control device. The combustion amount controlled by the control device is determined by feedforward control, which determines the combustion amount based on water flow, set temperature, inlet water temperature, etc., and feedforward control, which corrects the deviation amount between the set temperature and the outlet temperature. It is conceivable to perform this in combination with feedback control that corrects the combustion amount.

This feedback control includes proportional control, integral control, differential control, etc. as means for correcting the amount of deviation between the set temperature and the tapped water temperature.

[Problems to be Solved by the Invention] On the other hand, immediately after starting hot water supply, the threshold difference between the set temperature and the outlet temperature is large.

If feedback control is performed when this deviation amount is large, a large correction amount will be added to the combustion amount determined by the feeder 4-word control. For this reason, feedback control is applied too much, resulting in a combustion amount different from the target combustion amount.

As a result, the hot water temperature immediately after the hot water tap starts fluctuates significantly around the set temperature.

The present invention has been made in view of the above circumstances, and its purpose is to provide a water heater control device that eliminates problems caused by excessive feedback control immediately after hot water starts being dispensed.

[Means for Solving the Problems 1] In order to achieve the above object, the present invention provides a heating means 1 and a heat exchanger for exchanging heat generated by the heating means 1 with water, as shown in FIG. 2, and a control device 3 that performs heating control of the heating means 1. m until the temperature approaches
x:: Feedback control means 4 that does not perform amount correction
It is a technical means to have the following.

[Operation and Effects of the Invention] When an instruction to start dispensing hot water is given to the control device of the water heater,
The heating means generates heat, and hot water heated by the heat generated by the heating means is supplied from the water heater.

At this time, the hot water temperature is determined from the incoming water temperature immediately after hot water starts being tapped.
Raise the temperature by 1-9 degrees to the set temperature.

Immediately after the start of hot water tapping, the deviation between the set temperature and the hot water temperature is not corrected by feedback control until the hot water temperature approaches the set temperature. As a result, when the deviation χ, :t between the set temperature and the tapped water temperature is large immediately after the start of hot water tapping, feedback is not applied too much.

As a result, it is possible to eliminate problems caused by feedback control immediately after the start of hot water dispensing, and to suppress fluctuations in the tapped water temperature immediately after the start of hot water dispensing.

[Example] Next, an example in which the present invention is applied to a bypass mixing water heater will be described with reference to the drawings.

Figure 2 shows a schematic diagram of a bypass mixing type gas water heater.

This gas water heater is roughly divided into a combustion section 1 that burns fuel.
0, gas supply piping 20, water piping 30, and control device 4
It is composed of 0.

The combustion section 10 is a heating means of the present invention, and consists of a combustion case 12 in which a ceramic surface combustion burner 11 is disposed, and a blower 13 that supplies air for the combustion section into the combustion case 12. Combustion case 12 by blower 13
After combustion, the combustion air guided inside is discharged as combustion gas from an exhaust port (not shown).

The gas supply pipe 20 supplies fuel gas to a nozzle 21 that opens on the inner periphery of the centrifugal fan 14 of the blower 13, and the main solenoid valve 22, the main solenoid valve 23, and the proportional valve 24 are sequentially supplied from the upstream side. It is provided. The downstream side of the proportional valve 24 is branched into two parts, one of which is provided with a switching solenoid valve 25 and the other with an orifice 26. Note that the main solenoid valve 22, the main solenoid valve 23, and the switching solenoid valve 25 open and close the gas supply pipe 20 by energization control, and the proportional valve 24
The aperture ratio changes according to ffi, and the amount of gas supplied to the nozzle 21 is adjusted.

The water pipe 30 has one end connected to a water supply source and the other end connected to a hot water supply port, and exchanges heat between the heat generated by combustion of gas in the burner 11 and the water flowing inside. A heat exchanger 31 that heats the water to be heated, and this heat exchanger 3
1.

Heat exchanger 331 and bypass waterway 32 The water pipe 30 upstream of which branch path has a governor valve function that keeps the amount of water flowing into the heat exchanger 31 and bypass waterway 32 constant even if the water pressure flowing into the heat exchanger 31 and bypass waterway 32 changes. An electric water J1 control device 33 is provided which combines the functions of a water flow control valve and a water flow control valve for regulating water flow. Further, the bypass waterway 32 is provided with a throttle valve (opening/closing valve of the present invention) 34 that can adjust the amount of water passing through the bypass waterway 32 and open/close the bypass waterway 32.
There is.

Note that the aperture ratio of the electric water flow control bag W33 is the same as that of the heat exchanger 31.
In order to regulate the total amount of water flowing into the bypass waterway 32, it is provided to be the same as the throttle valve 34 or smaller than the throttle valve 34. In addition, an electric water flow control device 33 and a throttle valve 34
uses a geared motor to drive a valve body that can open and close the waterway as a means to adjust the amount of water.

As shown in FIG. 3, the control device 40 is composed of a microcomputer 41, a relay circuit 42, and a drive circuit 43, and controls the burner 11 according to the outputs of a controller 44 and various sensors operated by the user. a sparker 45 for igniting, a main solenoid valve 22, a main solenoid valve 23, a proportional valve 24, a switching solenoid valve 25, an electric water flow control device 33,
The throttle valve 34 is energized and controlled.

Various sensors of the control device 40 are linked to a flame rod 46 and a thermocouple 47 for detecting the flame of the burner 11 and the air-fuel ratio, an electric water flow control device 33, and a valve body of the throttle valve 34 to detect the opening degree. an air volume detection sensor 50 that detects the air volume of the blower 13 based on its rotational speed, and an inlet water temperature sensor 51 that detects the temperature of water flowing into the heat exchanger 31 and the bypass waterway 32.
, a hot water temperature sensor 5 that detects the temperature of hot water that has passed through the heat exchanger 31
2. A hot water temperature sensor 53 that passes through the heat exchanger 31 and the bypass waterway 32 and detects the temperature of the mixed hot water, and the heat exchanger 3
1 and a water amount detection sensor 54 for detecting the amount of water flowing into the bypass waterway 32.

Note that the air volume detection sensor 50 includes a rotating body that is interlocked with the motor of the blower 13, and generates a pulse signal according to the rotation of the rotating body. Further, the water amount detection sensor 54 includes a rotating body that rotates with the flow of water, and generates a pulse signal according to the rotation of the rotating body.

Then, the computer 41 detects the rotational speed of the blower 13 and the rotational speed of the rotating body from the interval of pulse signals generated by the airflow detection sensor 50 and the water amount detection sensor 54, and detects the airflow and water volume.

Next, combustion control and water amount control by the computer 41 will be briefly explained.

The user operates the switch connected to the hot water supply inlet, and the water pipe 3
When a water flow is generated at zero, the rotating body within the water amount detection sensor 54 rotates, and combustion is started. The amount of combustion after the start of combustion is determined based on the amount of water obtained by various sensors, the temperature of inlet water,
The temperature of the hot water passing through the heat exchanger 31, the temperature of the mixing hot water, the temperature of the hot water discharged, etc. are determined, and the voltage of the air blower 1fi13 is controlled so as to supply the burner 11 with an air volume corresponding to the determined combustion amount.

In other words, the amount of combustion equals the amount of air blown by the blower 13.

Then, the proportional valve 24 and the switching solenoid valve 25 are controlled to be energized so that a gas amount corresponding to the rotational speed of the blower 13 and the temperature of the flame of the burner 11 is obtained. The amount of combustion is such that the temperature of the hot water passing through the heat exchanger 31 is maintained at 1.1 F below the temperature at which water (drain water) generated by combustion does not adhere to the heat exchanger 31 (for example, 60°C). It is set as follows.

The throttle valve 34 is fixed at an appropriate opening calculated from the incoming water temperature, the set temperature, the temperature of the hot water that has passed through the heat exchanger 31, and the outlet temperature. Note that this fixation is set so that the flow rate flowing through the bypass waterway 32 is twice the amount of water flowing through the heat exchanger 31. In other words, the bypass waterway 32 and the heat exchanger 31
The ratio of the flow resistance to the flow resistance is set to about 2:1 by the throttle valve 34. Further, the opening degree of the throttle valve 34 is fixed when the amount of water entering is small or when the temperature of hot water coming out is lowered, and the opening degree of the throttle valve 34 is fixed so that the opening degree is calculated according to the amount of water entering and the temperature of hot water coming out. Energization is controlled.

Further, the electric water flow rate control device 33 is controlled to be energized so as not to exceed the maximum flow rate required to obtain the hot water temperature.

Next, calculation of the fuel Vt amount by the control device 740 will be described in detail.

The combustion ff1Q determined by the control device 40 is a combination of feedforward control and feedback control. The feedforward control of this embodiment uses the feedforward IF [, the heat exchange capacity correction IK,
The feedback control is the sum of the proportional oil stop P and the integral correction ff1I. Note that the feedback control means of the present invention is programmed into the microcomputer 41 together with the feedforward control means.

And combustion] tQ is It is expressed by the formula Q=FF++TfP+I.

Feedforward JilFT is the difference between the set temperature Ts set by the controller 44 and the inlet water temperature detected by the inlet water temperature sensor 51] and the water detected by the water 1 detection sensor 54! It is calculated from JW and the heat exchange efficiency 1/eff of the heat exchanger 31.

This is expressed by the formula FF = (Ts-Ti) W/eff.

The heat exchanger 1 correction IK is the difference between the set temperature [S set by the controller 44 and the outlet hot water temperature 1o detected by the outlet hot water temperature sensor 53 (one-point difference amount) and the heat exchanger Ff4 used.
The heat capacity ff1 is preset according to the container 31. It is calculated from M and a constant a depending on the bypass ratio between the heat exchanger 31 and the bypass waterway 32.

This is expressed by the formula K = a (TS - To)
The number is reversed.

This is expressed by the equation TN.

Proportional 'ffA] - amount P is the set temperature IS set by the controller 44 and the hot water detected by the hot water temperature sensor 53, ! - The difference (deviation N) from 0 is corrected by this (proportional correction amount proportional to the flatness amount, proportional correction -
It is calculated using the water amount W detected by the water amount detection sensor 54 and the proportionality constant aE so that the amount of change in EiP is proportional to the water amount W.

This is expressed by the formula P = E (Ts-To) W.

Note that in this embodiment, E=approximately 0.8 is appropriate.

The integral correction ff1I is to correct the difference (deviation amount) between the set temperature Ts set by the controller 44 and the outlet temperature ■0 detected by the outlet hot water temperature sensor 53 by integral control. Let the constant of integration be bxw so that the amount of water is proportional to the amount of water W. In addition, so that the integral correction amount ■ changes according to the change in the combustion amount (heating amount), it is set as the product of the change ratio of the feedforward amount I a-1+bw, (Ts-To) r
r. /Frfi-0.

In addition, ■. is the integral correction 1 calculated this time, ■□l is the integral correction amount calculated last time, F is the feedforward amount calculated this time, Fr is the feedforward amount calculated last time, and W is the amount calculated this time. Indicates the amount of water used.

In the feedback control, the deviation amount between the set temperature 1s and the tapped water temperature 1o is not corrected until the tapped water temperature To approaches the set temperature [S] immediately after the start of tapping when combustion is started according to the present invention. That is, immediately after the start of hot water tapping, P=o and I=O until the hot water tap temperature [0 approaches the set temperature 1 s.

As a result, the combustion amount Q is set to Q=FF++T0+O immediately after the start of hot water tapping until the hot water tapping temperature 0 approaches the set temperature 0.

The microcomputer 41 includes a determining means for determining when the hot water temperature To approaches the set temperature Ts.

Next, an example of this determination means will be listed.

B) A timer is provided in the control device 40 that starts counting from the start of hot water taping, and the timer determines that the hot water tap temperature 1o is not close to the set temperature Ts until a predetermined period of time (for example, 15 seconds) has elapsed. In other words, after a predetermined period of time has elapsed, it is determined that the hot water temperature [0] approaches the set temperature [S].

Until the difference between the outlet water temperature 1o and the inlet water temperature 11 reaches a predetermined ratio of the difference between the set temperature S and the inlet water temperature Ti,
It is determined that hot water temperature] 0 is not close to the set temperature 1s. In other words, after starting hot water, (Ts-Ti)×c≦T
When the o-Ti equation is satisfied, it is determined that the outlet hot water temperature]0 has approached the set temperature Ts. Note that C is a constant close to 1, such as 0.8 or 0.85.

c) After the start of hot water dispensing, when the difference between the dispensing hot water temperature 10 and the set temperature IS is within a predetermined temperature (for example, 20° C.), it is determined that the dispensing hot water temperature 0 has approached the set temperature 1S.

When the control device 40 determines that the hot water temperature 10 approaches the set temperature 1S, it performs proportional corrections M, P and integral corrections +7. I
By this, correction of the deviation amount between the set temperature 1S and the outlet hot water temperature]0 is started.

When the above determination means determines that the hot water temperature 10 approaches the set temperature IS and starts feedback control,
The initial values of the proportional correction ff1P and the integral correction LF and MI are set to 0, respectively, or (the proportional correction amount P is determined from the offset amount,
Feedback control is started by setting the integral correction amount I=-P or I=0.

According to this embodiment, immediately after the start of hot water dispensing, the values of the proportional correction ff1P and the integral compensator r1, which are feedback controls, are set to 0 until the dispensing hot water temperature ■0 approaches the set temperature Ts. In other words, the difference 1 between the set temperature Ta1l and the outlet hot water temperature is not corrected by feedback control.

As a result, when the deviation amount immediately after the start of tapping is large, the combustion amount Q is determined only by feedforward control. As a result, it is possible to eliminate the problem of excessive feedback control immediately after starting hot water dispensing, and to stabilize the temperature of hot water immediately after starting hot water dispensing.

(Modified example) Although an example in which the present invention is applied to PI control has been shown, it may be applied only to proportional control, only to integral control, only to differential control, or to PD sub-control. It may also be applied to PID control.

Although a water heater with a bypass waterway is shown as an example, the present invention may be applied to a water heater without a bypass waterway.

Further, although an example is shown in which gas is used as the fuel, other fuels such as kerosene may be used.

Further, although a combustion section that generates C heat by burning fuel is used as a heating means, other heat generating means such as an electric heater may be used.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a schematic configuration diagram of a bypass mixing type gas water heater, and FIG. 3 is a schematic block diagram of a control device.

Claims (1)

[Scope of Claims] 1) A water heater comprising: a heating means; a heat exchanger for exchanging heat generated by the heating means with water; and a control device for controlling heating of the heating means; A water heater characterized in that the control device is equipped with a feedback control means that corrects a deviation amount between a set temperature and a hot water outlet temperature, and does not correct the deviation amount until the hot water outlet temperature approaches the set temperature at the start of hot water dispensing. control device.