JPH11281158A - Hot-water supplier and method for controlling it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water heater for stabilizing a hot water outputting temperature to a set temperature after altering in a short time by at least suppressing an overshoot or an undershoot to the set temperature after the altering when the set temperature during hot water outputting is altered. SOLUTION: When a set temperature is altered during hot water outputting, an altering characteristic setting means 25 obtains altering characteristics for approaching a gas amount supplying to a combustor to approach from an initial value toward a target gas amount with a predetermined gas amount changed by exceeding the target gas amount in a direction of existing the target amount for steadily operating at the set temperature after the altering from the present gas amount as the initial value. A first combustion control means 21 feedforward controls the gas amount according to the characteristics from a time point of altering the set temperature. Then, the control means is returned to a second combustion control means 22 when a difference between the supply gas amount and the target amount falls within a reference value, and the gas amount is controlled by a predetermined combustion control accompanied with feedback control based on at least the hot water outputting temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water heater capable of changing a set temperature during tapping.

[0002]

2. Description of the Related Art A conventional water heater controls the amount of gas supplied to a combustion section by feedforward control based on an incoming water temperature, a set temperature, and the like for a few seconds after the start of hot water supply. The gas amount was controlled by a control method that used both feedback control and feedforward control.

[0003]

However, there is a certain time delay before a change in the gas amount appears as a change in the tapping temperature, and even when the gas amount is changed stepwise, the tapping temperature remains at a predetermined time constant. Therefore, if the set temperature is changed during tapping, the feedback control becomes too effective. Therefore, the hot water temperature overshoots or undershoots the set temperature until the set temperature after the change is stabilized, and
There is a problem that it takes time for the hot water temperature to stabilize at the set temperature after the change.

The present invention has been made in view of such problems of the conventional technology. When the set temperature is changed during tapping, the overshoot and undershoot with respect to the changed set temperature are reduced. It is an object of the present invention to provide a water heater capable of suppressing the hot water temperature to a set temperature after the change in a short time and a control method thereof.

[0005]

The gist of the present invention to achieve the above object lies in the following inventions. [1] In a water heater that can change the set temperature during hot water supply,
First combustion control means (21) for feedforward controlling the amount of gas supplied to the combustion section (11);
1) controlling the amount of gas supplied to 1) by a predetermined control method including feedback control based on at least the tapping temperature;
The control of the amount of gas supplied to the combustion control means (22) and the combustion section (11) is performed by controlling any one of the first combustion control means (21) and the second combustion control means (22). Switching means (23) for switching whether or not to perform the means, and a change characteristic of the gas amount when the first combustion control means (21) performs feedforward control on the gas amount supplied to the combustion section (11). A change characteristic setting means (25), wherein the switching means (23) controls the gas amount supplied to the combustion section (11) to the first combustion when the set temperature is changed during tapping. The control means (21) is switched to the control means (21), and when a predetermined return condition is satisfied thereafter, the control means for the gas amount is returned to the second combustion control means (22), and the change characteristic setting means (25) is set during the tapping. When the temperature changes, the current The gas amount changed beyond the target gas amount in the direction in which the target gas amount for steady operation at the set temperature after the change from the gas amount is set as the initial value, and gradually approaches the target gas amount from the initial value. Is set as the change characteristic of the gas amount, and the first combustion control means (21) sets the change characteristic set by the change characteristic setting means (25) from the time when the set temperature is changed during tapping. A water heater characterized in that the amount of gas supplied to the combustion section (11) is feedforward controlled according to the change characteristic.

[2] The change characteristic setting means (25)
The water heater according to [1], wherein the change characteristic is set based on a temperature difference between a set temperature before the change and a set temperature after the change.

[3] The switching means (23) is provided with the first
When a predetermined time has passed since the switching to the combustion control means (21), it is determined that the return condition has been satisfied, and the control means for controlling the amount of gas supplied to the combustion part (11) is changed to the second combustion control means (22). The water heater according to [1] or [2], wherein the water heater is returned to [1].

[4] The switching means (23) determines that the return condition is satisfied when the difference between the gas amount supplied to the combustion section (11) and the target gas amount is within a predetermined value. The water heater according to [1] or [2], wherein control means for controlling the amount of gas supplied to the combustion section (11) is returned to the second combustion control means (22).

[5] The change characteristic setting means (25)
The gas amount change characteristic is set such that the tapping temperature reaches the set temperature at the fastest without overshooting or undershooting [1].
The water heater according to [2], [3] or [4].

[6] In the method for controlling a water heater capable of changing the set temperature during tapping, when the set temperature is changed during tapping, a target for steady operation at the set temperature after the change from the current gas amount. A predetermined gas amount changed beyond the target gas amount in a direction in which the gas amount exists is set as an initial value, and the combustion unit (1
The feed amount is controlled so that the gas amount supplied to the first portion gradually approaches the target gas amount from the initial value, and when a predetermined return condition is satisfied, the combustion unit (1) is controlled.
A method of controlling a water heater, wherein the control of the amount of gas supplied to 1) is returned from the feedforward control to a predetermined control accompanied by at least feedback control based on a tapping temperature.

The present invention operates as follows. The water heater includes first combustion control means (21) for feed-forward controlling the amount of gas supplied to the combustion section (11) and feedback control based on at least the outlet temperature of the gas amount supplied to the combustion section (11). A second combustion control means (22) for controlling by a predetermined control method, and in a steady state after the start of hot water supply and after the temperature of the hot water is stabilized, feedback control by the second combustion control means (22). The gas amount is adjusted by the combustion control accompanied by.

When the set temperature is changed during tapping in the steady state, the switching means (23) switches the control means for controlling the amount of gas supplied to the combustion part (11) to the first combustion control means (21).
Switch to When the set temperature is changed during tapping, the change characteristic setting means (25) sets the target gas amount in the direction in which the target gas amount for steady-state operation at the changed set temperature from the current gas amount exists. The gas amount changed beyond the initial value is set as an initial value, and the characteristic of changing from the initial value to gradually approach the target gas amount is a gas amount changing characteristic when the first combustion control means (21) performs feedforward control. Set as

The first combustion control means (21) starts changing characteristic setting means (2) when the set temperature is changed during tapping.
According to the change characteristic set by 5), the combustion unit (1)
The amount of gas supplied to 1) is feedforward controlled, and the switching means (23) returns the gas amount control means to the second combustion control means (22) when a predetermined return condition is satisfied.

As described above, the gas amount is adjusted by the feedforward control until a predetermined period elapses from the time when the set temperature is changed, and the gas amount at that time is initially adjusted to correspond to the changed set temperature. After a sudden change to a value exceeding the target gas amount, it is gradually changed to approach the target gas amount. be able to.

The change characteristic of the gas amount during the feedforward control is set based on the temperature difference between the set temperature before the change and the set temperature after the change. Thereby, the optimum change characteristic can be set according to the temperature difference before and after the change, and the outlet temperature can be made to quickly follow the set temperature after the change regardless of the change range of the set temperature.

The switching means (23) controls the amount of gas supplied to the combustion part (11) when the predetermined time has elapsed since the switching to the first combustion control means (21). Return to (22). Since the elapsed time is used as a reference in this way, switching to the second combustion control means (22) can be easily performed.

The switching means (23) includes a combustion section (11).
When the difference between the amount of gas supplied to the gas and the target gas amount falls within a predetermined value, it is determined that the return condition is satisfied and the combustion unit (1
The control means for controlling the amount of gas supplied to 1) is returned to the second combustion control means (22). For example, when the difference between the supplied gas amount and the target gas amount falls within 5% of the difference between the gas amount before changing the set temperature and the target gas amount, the second combustion control means (22) Switch.

As described above, when the temperature of the hot water almost approaches the target gas amount, the tapping temperature also substantially approaches the set temperature after the change. There is no significant fluctuation. In addition, since feedback control is performed at a stage when the target gas amount is almost approached, the actual tapping temperature can be quickly and reliably matched with the set temperature.

The changing characteristic setting means (25) sets the changing characteristic of the gas amount such that the tapping temperature reaches the set temperature most quickly without overshooting or undershooting.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. Each drawing shows an embodiment of the present invention. As shown in FIG. 2, the water heater 10 includes a burner 11 and a heat exchanger 12 disposed above the burner 11, and a water supply pipe 13 is provided on the inlet side of the heat exchanger 12. A hot water supply pipe 14 is connected to the outlet side of the exchanger 12. A faucet (not shown) is attached to the end of the hot water supply pipe 14.

In the middle of the water supply pipe 13, a flow sensor 15 for detecting the presence or absence of water flow and the amount of water flow, and an incoming water temperature sensor 16 for detecting the temperature of the supply water before heating flowing into the heat exchanger 12 are attached. ing. Further, a tapping temperature sensor 17 for detecting the temperature of the hot water heated by the heat exchanger 12 is provided at a location near the heat exchanger 12 in the hot water supply pipe 14. In the middle of the gas supply pipe 18 leading to the burner 11,
A gas proportional valve 19 for adjusting the amount of gas supplied to the burner 11 is attached.

The water heater 10 has a control unit 20 on which various circuit components for controlling the hot water supply operation are mounted. In addition to the flow sensor 15, the incoming water temperature sensor 16, the outgoing water temperature sensor 17, the gas proportional valve 19, and the like, the control unit 20 allows the user to perform operations such as setting the outgoing water temperature and turning on and off the operation of the water heater 10 itself. A remote controller 40 is connected to accept the request.

FIG. 1 shows an outline of a circuit configuration of the control unit 20. The control unit 20 controls the amount of gas supplied to the burner 11 by using the first combustion control unit 21 that controls the amount of gas supplied to the burner 11 by feedforward control, and controls the amount of gas that is supplied to the burner 11 by using both feedforward control and feedback control. The second combustion control means 22 and the first combustion control means 21
And switching means 23 for switching which of the combustion control means 22 is controlled by the control means.

The switching means 23 controls the gas amount by the first combustion control means 21 for a predetermined time from the start of tapping and for a predetermined period after the set temperature is changed during tapping, and in the other period, the gas amount is controlled by the second combustion control means. These control means are switched so that the gas amount is controlled by the combustion control means 22 of FIG. That is, the switching unit 23 switches the first combustion control unit 21 when the required heat amount changes significantly, and switches the second combustion control unit 22 during the steady operation in which the required heat amount does not change much.
Is to be selected. The switching means 23 includes
A timer 24 for measuring the elapsed time after switching to the first combustion control means 21 is connected.

The change characteristic setting means 25 connected to the first combustion control means 21 determines how the burner 11 should change the gas amount by feedforward control when the set temperature is changed during tapping. This is a circuit part for determining a change characteristic indicating the above. Change characteristic setting means 2
Reference numeral 5 indicates that when the set temperature is changed, a change characteristic according to the change width of the set temperature before and after the change is selected. In the data storage unit 26, change characteristics for each change width are registered in advance.

The remote controller 40 has a temperature setting switch 41 for changing the set temperature. In addition, the remote controller 40 includes various operation switches (not shown) and a display unit for displaying a set temperature, an operation status, error information, and the like.

FIG. 3 is a graph showing a part of the change characteristic data stored in the data storage section 26 of the change characteristic setting means 25. The abscissa in the figure indicates the time after the set temperature is changed, and the ordinate indicates the amount of change in the gas amount based on the gas amount (GF1) immediately before changing the set temperature.

A change characteristic 51 indicated by a solid line indicates a case where the change range of the set temperature is + 10 ° C., and a change characteristic 52 indicated by a dotted line indicates a case where the change range is + 8 ° C. The change characteristic 5 indicated by a two-dot broken line.
3 indicates the case where the change width is + 6 ° C., and the change characteristic 54 indicated by the one-dot broken line indicates the case where the change width is + 4 ° C., respectively.
The gas amounts 51a to 54a when the change characteristics 51 to 54 are substantially parallel to the horizontal axis are the gas amount (target gas amount GF2) required for steady operation at the changed set temperature and the gas amount immediately before the change. The difference from the amount (GF1) is shown.

As described above, since the change characteristic is stored using the change width of the set temperature as a parameter without depending on the absolute temperature, the amount of data to be stored can be reduced. These gas amount change characteristics are characteristics determined such that when the set temperature is changed during tapping, the tapping temperature shifts to the changed set temperature in the shortest time without overshoot or undershoot. , Obtained by repeating a driving test. Note that FIG.
In the above, the case where the set temperature is raised is shown, but the change characteristic when the set temperature is lowered is substantially vertically symmetrical with respect to that shown in FIG. 3 about the time axis.

Next, the operation will be described. FIG. 4 shows a flow of operation performed by the control unit 20 when the set temperature is changed during tapping. Until a certain time elapses from the start of hot water
The gas amount is controlled by the first combustion control means 21, and thereafter, since the hot water temperature is stable and the required heat quantity does not change significantly, the gas quantity is controlled by the second combustion control means 22. When the set temperature is changed after entering the steady tapping state in this manner (step S101; Y), the change characteristic setting means 25 determines how much the set temperature has been changed in any of the upper and lower directions (change The width △ Tsp) is obtained, and the change characteristic corresponding to the change width is obtained with reference to the data storage unit 26 (step S102).

The switching means 23 sets the change characteristic acquired by the change characteristic setting means 25 in the first combustion control means 21 and then controls the gas amount supplied to the burner 11 from the second combustion control means 22. The control is switched to the first combustion control means 21 (step S103). As a result, the control of the gas amount is switched from a combination of the feedback control and the feedforward control to a single feedforward control.

FIG. 5 shows a change in the set temperature, a change in the tapping temperature and a change in the amount of gas supplied to the burner 11 when the set temperature is increased from Tsp1 to Tsp2. As shown in FIG. 5A, the set temperature is Tsp
When it is increased from 1 to Tsp2, as shown in FIG. 5C, the control of the gas amount is shifted to the feedforward control, and the initial gas amount 61 is changed to the value at the time of steady operation at the changed set temperature Tsp2. The value is set to a value larger than the target gas amount GF2. Then, as shown by a solid line b in FIG.
The gas amount is gradually reduced toward the target gas amount GF2 (step S104).

When the difference ΔGF between the gas amount supplied by the feedforward control and the target gas amount GF2 becomes smaller than a predetermined reference value (step S105;
Y), the switching unit 23 switches the gas amount control unit to the second combustion control unit 22 (step S106), and thereafter controls the gas amount by combustion control using both feedforward control and feedback control. . Here, the value of the reference value △ GF is determined by the following equation. ΔGF = ABS (GF2−GF1) × 0.05 (2) Here, ABS indicates an absolute value.

After the set temperature is changed, by controlling the gas amount as described above, the tapping temperature does not overshoot as shown by the solid line b in FIG. The new set temperature is reached. When the combustion control with the feedback control is executed even after the set temperature is changed as in the related art, the gas amount changes as indicated by a dotted line a in FIG. 5C, and the tapping temperature changes as indicated by a dotted line in FIG. As shown by a, the temperature changes to reach the set temperature after the change while overshooting and undershooting.

This is because even if the gas amount is changed, there is a certain delay time before the change appears in the tapping temperature as shown in FIG. 5B, and the tapping temperature does not change even after the change starts to appear. Changes gradually according to a certain time constant, so if the set temperature is changed, if the feedback control is continued to bring the tapping temperature close to the set temperature, the gas amount will be changed more than necessary, resulting in Hot water temperature overshoots. Further, when it is detected that the tapping temperature has exceeded the set temperature after the change, and this is fed back, the gas amount sharply decreases, and an undershoot will appear this time.

The change characteristic set by the change characteristic setting means 25 is determined in consideration of such a time delay and a time constant so that the tapping temperature shifts to the changed set temperature without causing overshoot or the like. Therefore, the feedwater temperature can be smoothly shifted to the target temperature by performing the feedforward control according to the change characteristic.

Since the initial value of the gas amount in the change characteristic is changed at once to a value exceeding the target gas amount GF2 corresponding to the set temperature after the change, the tapping temperature is rapidly increased toward the set temperature after the change. It is possible to change to. After that, since the supplied gas amount gradually approaches the target gas amount GF2, the outlet temperature can be stabilized at the changed set temperature without overshooting or undershooting.

FIG. 6 shows a change in the set temperature, a change in the tapping temperature, and a change in the amount of gas supplied to the burner 11 when the set temperature is reduced from Tsp1 to Tsp2. As shown in FIG. 6A, the set temperature is Tsp
Also when the pressure is reduced from 1 to Tsp2, the control of the gas amount is shifted to the feedforward control as shown in FIG. 6C, and the initial gas amount 71 is steadily operated at the changed set temperature Tsp2. Is set to a value smaller than the target gas amount GF2 at that time. Thereafter, as shown by a solid line b in FIG. 6C, the gas amount is gradually increased toward the target gas amount GF2.

When the difference ΔGF between the gas amount supplied by the feedforward control and the target gas amount GF2 becomes smaller than the reference value, the gas amount control means is switched to the second combustion control means 22, Thereafter, the gas amount is controlled by combustion control using both the feedforward control and the feedback control.

As described above, when a change is made to lower the set temperature, by controlling the gas amount as described above, FIG.
As shown by the solid line b in (b), the tapping temperature reaches the changed set temperature within a short time without undershoot. When the control with the feedback control is executed even after the set temperature is changed as in the related art, the gas amount changes as indicated by a dotted line a in FIG. 6C, and the tapping temperature changes as shown in FIG. As shown by the dotted line a, the temperature changes to reach the set temperature after the change while overshooting and undershooting.

In the embodiment described above, the reference value ΔG
Although F was set to 5% of the absolute value of the difference between GF1 and GF2, the value of ΔGF is not limited to this. Further, the timing of returning from the feedforward control to the combustion control with the feedback control is determined based on the gas amount (、 GF). The control may be returned to the combustion control involving feedback control by the second combustion control means 22. For example, the elapsed time after switching to the feedforward control by the first combustion control means 21 is measured by the timer 24 in FIG. 1, and when a predetermined time such as 5 seconds has elapsed, the second combustion control means 22 May be returned to.

[0042]

According to the water heater and the method of controlling the same according to the present invention, the gas amount is adjusted by feedforward control over a certain period from the time when the set temperature is changed during tapping, and the gas at that time is adjusted. After changing the amount at once to a value exceeding the target gas amount corresponding to the set temperature after the change, it is gradually changed so as to approach the target gas amount. The tapping temperature can be stabilized at the set temperature after the change.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram showing a configuration of a water heater according to one embodiment of the present invention.

FIG. 3 is an explanatory diagram showing an example of a change characteristic of a gas amount stored in a data storage unit of a change characteristic setting unit.

FIG. 4 is a flowchart illustrating a flow of an operation performed by the water heater according to the embodiment of the present invention when the set temperature is changed during tapping.

FIG. 5 is an explanatory diagram showing a change in the set temperature, a change in the tapping temperature, and a change in the amount of gas supplied to the burner in a case where the set temperature is increased from Tsp1 to Tsp2.

FIG. 6 is an explanatory diagram showing a change in the set temperature, a change in the tapping temperature, and a change in the amount of gas supplied to the burner in a case where the set temperature is reduced from Tsp1 to Tsp2.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Hot water heater 11 ... Burner 12 ... Heat exchanger 13 ... Water supply pipe 14 ... Hot water supply pipe 15 ... Flow sensor 16 ... Inlet water temperature sensor 17 ... Outlet water temperature sensor 18 ... Gas supply pipe 19 ... Gas proportional valve 20 ... Control unit 21 ... First combustion control means 22 ... Second combustion control means 23 ... Switching means 24 ... Timer 25 ... Change characteristic setting means 26 ... Data storage unit 40 ... Remote control 41 ... Temperature setting switch

Claims (6)

[Claims] 1. A water heater capable of changing a set temperature during hot water supply, a first combustion control means for feedforward controlling an amount of gas supplied to a combustion section, and a gas amount supplied to the combustion section to at least a hot water temperature. A second combustion control unit that performs control using a predetermined control method that includes feedback control based on the first combustion control unit, and controls the amount of gas that is supplied to the combustion unit using any of the first combustion control unit and the second combustion control unit Switching means for switching whether to perform the control by the control means, and change characteristic setting means for setting a change characteristic of the gas amount when the first combustion control means performs feedforward control on the gas amount supplied to the combustion section. The switching means, when the set temperature is changed during tapping,
Switching the control means for controlling the amount of gas supplied to the combustion section to the first combustion control means, and thereafter returning the control means for controlling the gas amount to the second combustion control means when a predetermined return condition is satisfied; The setting means, when the set temperature is changed during tapping, the gas amount changed beyond the target gas amount in the direction in which the target gas amount for steady-state operation at the changed set temperature from the current gas amount exists. Is set as an initial value, and a characteristic that gradually changes from the initial value to approach the target gas amount is set as a change characteristic of the gas amount, and the first combustion control unit changes the set temperature during hot water supply. A water heater characterized in that the amount of gas supplied to the combustion section is feedforward controlled from a point in time in accordance with the change characteristic set by the change characteristic setting means. 2. The water heater according to claim 1, wherein the change characteristic setting means sets the change characteristic based on a temperature difference between a set temperature before the change and a set temperature after the change. 3. The switching means determines that the return condition is satisfied when a predetermined time elapses after switching to the first combustion control means, and controls the gas amount control means to supply the gas to the combustion section with the second combustion control means. The water heater according to claim 1 or 2, wherein the control is returned to the combustion control means. 4. The gas supply device according to claim 1, wherein said switching means determines that said return condition is satisfied when a difference between a gas amount supplied to said combustion unit and said target gas amount becomes within a predetermined value. 3. A water heater according to claim 1, wherein said control means is returned to said second combustion control means. 5. The changing characteristic of the gas amount according to claim 1, wherein the changing characteristic setting means sets the changing characteristic of the gas amount such that the tapping temperature reaches the set temperature most quickly without overshooting or undershooting. The water heater according to 2, 3 or 4. 6. A method for controlling a water heater capable of changing a set temperature during tapping, wherein when the set temperature is changed during tapping, a target gas for steadily operating at a changed set temperature from a current gas amount. A predetermined gas amount changed beyond the target gas amount in the direction in which the amount exists as an initial value, and feedforward control is performed so that the gas amount supplied to the combustion unit gradually approaches the target gas amount from the initial value. Controlling the amount of gas to be supplied to the combustion section when a predetermined return condition is satisfied from the feedforward control to at least a predetermined control accompanied by a feedback control based on at least a tapping temperature. .