JP3096497B2 - Water heater control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a water heater comprising a heat source, a water chamber for storing water heated by the heat source, and a water supply pipe and a water supply pipe connected to the water chamber.

[0002]

2. Description of the Related Art In this type of water heater, for example,
As disclosed in Japanese Patent No. 25621, a temperature detector for detecting a water temperature of a water chamber, and a heat source control for starting and stopping a heat source according to a set temperature determined by a temperature setter and a detected temperature of the temperature detector. And a control device having means. Then, the detected temperature T of the temperature detector becomes the set ON temperature T
When the temperature becomes lower than S1, the heat source is operated, and when the detected temperature T becomes higher than the OFF set temperature TS2 (TS2> TS1), the heat source is stopped.

[0003]

In recent years, water heaters have been reduced in size, and accordingly, the amount of hot water stored in a water chamber has been reduced to 20%.
It is as small as about 30 liters. For this reason, the water temperature change in the water chamber is larger than that of a large amount of hot water storage,
There was a drawback that the tapping temperature became significantly higher than the set off temperature or the tapping temperature was significantly lower than the set on temperature, and the tapping temperature became unstable.

The present invention has been made in view of the above-mentioned facts, and has a function of starting and stopping a heat source in accordance with a temperature detected by a temperature detector for detecting a water temperature of a water chamber and a set temperature determined by the temperature setter. It is an object of the present invention to stabilize the tapping temperature even when the capacity of the water chamber is small.

[0005]

According to the present invention, a heat source,
A water chamber for storing water heated by the heat source, and a water heater including a water supply pipe and a hot water supply pipe connected to the water chamber, a temperature detector for detecting a water temperature of the water chamber, and a temperature setter. Heat source control means for starting and stopping a heat source in accordance with a set temperature determined by the temperature setter and a detected temperature of the temperature detector, wherein the heat source control means has a predetermined temperature gradient of the detected temperature of the temperature detector. When the temperature is equal to or greater than the value, the heat source is started and stopped when the detected temperature is predicted to reach the set temperature after a predetermined time from the temperature gradient.

[0006]

With this configuration, for example, when the positive temperature gradient of the temperature detected by the temperature detector is larger than a predetermined value during the operation of the heat source, the detected temperature is increased before the detected temperature rises to the OFF set temperature. When the temperature reaches a predetermined temperature determined by the temperature gradient (off set temperature−temperature gradient × predetermined time), the heat source is stopped, and there is no concern that the water temperature in the water chamber will greatly exceed the set temperature.

If the negative temperature gradient of the temperature detected by the temperature detector is larger than a predetermined value while the heat source is stopped, the detected temperature is determined by the predetermined temperature determined by the temperature gradient before the detected temperature falls to the set ON temperature. The heat source is activated when (on set temperature−temperature gradient × predetermined time), and the water temperature of the water chamber can be prevented from dropping significantly below the set temperature.

[0008]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.

FIG. 2 shows a water heater to which the present invention is applied. In FIG. 2, reference numeral 1 denotes a water heater main body installed under the eaves and the like outdoors.
Water chamber 3, exhaust chamber 4 and flue 5 with capacity of about 20 liters
A heat exchanger 6 comprising a burner 7 serving as a heat source facing the combustion chamber 2 and a control device 8 are built in.

Reference numeral 9 denotes a water supply pipe connected to the water chamber 3 slightly above the upper wall of the combustion chamber 2, reference numeral 10 denotes a hot water supply pipe connected to the upper part of the water chamber 3, and reference numeral 11 denotes a combustion pipe collected in the exhaust chamber 4. An exhaust top 12 for dispersing exhaust gas to the atmosphere is a temperature detector for detecting the temperature of the water in the water chamber 3 between the water supply pipe 9 and the hot water supply pipe 10. Hot water supply pipe 10 led out of water heater main body 1 is connected to faucet 13 installed in an indoor kitchen, a washroom, or the like.
A remote control 14 is provided near the faucet 13, and the remote control 14 is connected to the control device 8 via a remote control line 15.

FIG. 1 shows a concrete example of the control device 8 for a water heater described above. In FIG. 1, reference numeral 16 denotes a microcomputer (hereinafter referred to as a microcomputer) for controlling the burner 7 as a heat source, and an operation switch 17 and a temperature setting device 18 of a remote controller 14 and a temperature detector 12 are provided on the input side of the microcomputer 16. , A flame detector 19. On the output side of the microcomputer 16, a burner fan 20, an ignition device 21, and a fuel supply pump (fuel supply means) 22 constituting the burner 7 are provided.

While the operation switch 17 is turned on, the microcomputer 16 controls the start / stop of the burner 7 as shown in FIGS. That is, as shown in FIG. 3, the microcomputer 16 reads the temperature T detected by the temperature detector 12 every second, for example, and stores it. Further, by calculating the difference between the detected temperature data and the previous detected temperature data, the temperature gradient Δ
T is detected. When the absolute value of the temperature gradient ΔT is equal to or more than a predetermined value (for example, 0.5 deg ° C./sec),
A different start / stop control of the burner 7 is performed when the value is less than the predetermined value.

Since the temperature of the water in the water chamber 3 is low when the operation switch 17 is turned on, the microcomputer 16 issues a thermo-on signal to operate the burners 7 in the following order. First, as shown in FIG. 4, the burner fan 20 is operated to start the pre-purge of the burner 7, and in the case of using kerosene as fuel, the oil attached to the ignition device 21 is scattered. Next, after the ignition device 21 is operated, the fuel supply pump 22 is operated.

The interval from the start of operation of the burner fan 20 to the start of operation of the fuel supply pump 22 is the pre-purge time. In this embodiment, the operation interval between the burner fan 20 and the ignition device 21 (pure The pre-purge time is fixed (for example, 2 seconds), and the operation interval (pre-ignition time) between the ignition device 21 and the fuel supply pump 22 is made variable (for example, 3 to 8 seconds) according to the detected temperature T. That is, as shown in Table 1, the pre-ignition time is the longest (8 seconds) when the detected temperature T is lower than 22 ° C., and is 0.5 to 5 times longer than the longest time when the detected temperature T is 22 ° C. or higher. .0 seconds.

[0015]

[Table 1]

When the operation switch 17 is turned on, the detected temperature T
, The pre-ignition time is usually up to 8 seconds. Therefore, the pre-purge time is 10 seconds, and the pre-purge of the burner 7 is sufficiently performed. When the fuel supply pump 22 operates, the burner 7 ignites the mixture of fuel and air, and combustion starts. Then, when ignition is detected based on a signal from the flame detector 19, the microcomputer 16 stops the ignition device 21 after continuing the operation for a predetermined time (post-ignition time).

In the water chamber 3 having a relatively small capacity, the water temperature rises sharply except during tapping. In this case, since the positive temperature gradient of the detected temperature T of the temperature detector 12 is equal to or greater than a predetermined value, the microcomputer 16 determines that the detected temperature T is lower than the off-set temperature TS2 (TS2-ΔT × At the time of 5), a thermo-off signal is issued to stop the burner 7. That is, the burner 7 is stopped when the detected temperature T is predicted to reach the off-set temperature TS2 after 5 seconds from the temperature gradient (positive). For this reason, water chamber 3
There is no need to worry that the water temperature will greatly exceed the off set temperature TS2.

Of course, as during tapping, the temperature gradient ΔT
Is smaller than the predetermined value, the microcomputer 16 continues the operation of the burner 7 until the detected temperature T reaches the OFF set temperature TS2 as shown in FIG. 6, so that the burner 7 may be stopped during the continuous hot water supply. Absent. When the burner 7 is stopped, post-purge is performed as shown in FIG. 4 to prepare for the next operation of the burner 7.

If hot water is supplied while the burner 7 is stopped, fresh water is supplied from the water supply pipe 9 to the water chamber 3, so that the temperature detected by the temperature detector 12 drops rapidly. Also in this case, since the absolute value of the negative temperature gradient ΔT of the temperature detected by the temperature detector 12 is equal to or more than a predetermined value, the microcomputer 16 sets the detected temperature T to a temperature (TS1−ΔT × 5) higher than the ON set temperature TS1. At this point, a thermo-on signal is issued to operate the burner 7. That is, the burner 7 is operated at a point in time when the detected temperature T is predicted to reach the on-set temperature TS1 after 5 seconds from the temperature gradient (negative). For this reason, water chamber 3
There is no worry that the water temperature will drop significantly below the on-set temperature.

Of course, when the absolute value of the negative temperature gradient ΔT is small, such as during the stoppage of tapping, the microcomputer 16 activates the burner 7 when the detected temperature reaches the on-set temperature TS1.

When the start / stop of the burner 7 is repeated in response to the signals of the thermo-off and the thermo-on, the pre-purge time for operating the burner 7 is shortened because the water temperature of the water chamber 3 is high. When the temperature of the water in the water chamber 3 is high, the fuel remaining in the burner 7 is easily discharged naturally, and sufficient prepurge is performed when the operation switch 17 is turned on.
Even if the prepurge time is shortened, there is no safety problem. In addition, the pre-purge time is reduced only by the pre-ignition time, and the pure pre-purge time is always constant. Therefore, there is no fear that the ignition is performed with the oil attached to the ignition device 21.

It is preferable that the prepurge time is not shortened in the case of the anti-freezing operation performed when the operation switch 17 is turned off or in the case of the recycle operation when the fire is extinguished halfway. Also, the post-purge time may be shortened together with the pre-purge time.

[0023]

Since the present invention is configured as described above, when the temperature gradient of the water chamber is equal to or higher than a predetermined value, the heat source is started and stopped early according to the temperature gradient, and the water temperature of the water chamber is reduced. It is possible to prevent the temperature from exceeding or lowering significantly.
It is possible to stabilize the tapping temperature even in a water heater with a small capacity of the water chamber.

[Brief description of the drawings]

FIG. 1 is a block diagram of a control device of a water heater showing one embodiment of the present invention.

FIG. 2 is a schematic structural explanatory view showing an example of a water heater.

FIG. 3 is a flowchart for explaining the operation of the control device.

FIG. 4 is a time chart for explaining the operation of the control device.

FIG. 5 is an explanatory diagram showing temperature control characteristics of a control device.

FIG. 6 is an explanatory diagram showing another temperature control characteristic of the control device.

[Description of Signs] 1 Hot water heater main body 3 Water chamber 6 Heat exchanger 7 Burner (heat source) 8 Control device 9 Water supply pipe 10 Hot water supply pipe 12 Temperature detector 16 Microcomputer (heat source control means) 20 Burner fan 21 Ignition device 22 Fuel Supply pump (fuel supply means)

Claims (1)

(57) [Claims] A temperature for detecting a water temperature of a water chamber in a water heater including a heat source, a water chamber for storing water heated by the heat source, and a water supply pipe and a water supply pipe connected to the water chamber. A detector, a temperature setter, and heat source control means for starting and stopping a heat source in accordance with a set temperature determined by the temperature setter and a temperature detected by the temperature detector. If the temperature gradient of the detected temperature is equal to or higher than the predetermined value,
A water heater control device configured to start and stop the heat source when the detected temperature is predicted to reach the set temperature after a predetermined time from the temperature gradient.